This document summarizes the key components and characteristics of connective tissue. It discusses:
1) The origin of connective tissue from mesoderm and its characteristics of being mesoderm-derived tissue with widely separated cells and large amounts of extracellular matrix.
2) The main components of connective tissue - cells, fibers, and matrix. It describes the different types of connective tissue including loose connective tissue, cartilage, bone, and blood.
3) The different cell types found in connective tissue including fibroblasts, adipocytes, macrophages, mast cells, and others; as well as the fibers including collagenous, elastic, and reticular fibers.
Microvilli, cilia, and flagella are cell surface projections that serve important functions.
Microvilli increase cell surface area and aid in absorption. They cover the intestinal surface and form the brush border. Cilia are shorter projections that beat in a coordinated way to move substances over cell surfaces, such as mucus in the respiratory tract.
Flagella are much longer than cilia and power sperm cell motility through whip-like beating. Both cilia and flagella contain microtubules in their core that extend from basal bodies anchored in the cell.
Eithelial tissue,connective tissue by Dr Jyoti Prakash Pani Associate Profess...phupu
Epithelial and connective tissues are the two main types of tissues in the body. Epithelial tissue lines the outer surfaces and inner cavities of the body. It is classified as single-layered (simple) or multi-layered (stratified) epithelium. Common types include squamous, cuboidal, columnar, transitional, and pseudostratified columnar epithelium. Connective tissue supports and binds other tissues. It contains ground substance and fibers, along with fibroblasts, adipocytes and immune cells. Major forms are loose connective tissue, dense connective tissue, regular dense connective tissue, elastic connective tissue, and reticular connective tissue.
This document provides an overview of the histology of blood vessels, including arteries and veins. It begins by stating the learning objectives of identifying and describing the microscopic structures of elastic arteries, muscular arteries, medium-sized veins, and blood capillaries. The document then provides detailed descriptions of the tunica intima, tunica media, and tunica adventitia layers and their components in different blood vessel types. Key differences between arteries and veins are highlighted, such as arteries having a thicker tunica media than adventitia, while veins have a thinner tunica media. Examples of elastic and muscular arteries are given along with diagrams and microscopic slides.
Enamel is the hardest substance in the human body. It is composed primarily of hydroxyapatite crystals arranged in rods (prisms) that run from the dentin-enamel junction to the outer enamel surface. The basic structural unit of enamel is the enamel rod, which is hexagonal or oval in cross-section. Between the rods is the interrod enamel. Enamel gains its strength through the interweaving of tightly packed hydroxyapatite crystals in parallel alignment within the rods.
This document discusses four types of simple epithelium: squamous, cuboidal, columnar, and pseudostratified. Squamous epithelium is scale-like and found lining blood vessels and body cavities. Cuboidal epithelium lines small ducts and tubules, and can be secretory or absorptive. Columnar epithelium lines ducts of exocrine glands and the stomach, and is adapted for secretion and absorption. Pseudostratified epithelium appears to have multiple layers but actually has cells of different heights contacting the basement membrane, seen in airways.
The dental pulp originates from cranial neural crest cells that migrate into the developing tooth germ. During tooth development, these cells form the dental papilla which becomes the dental pulp. The pulp contains odontoblasts, fibroblasts, undifferentiated mesenchymal cells, and macrophages. It has a cell-rich zone containing blood vessels and a cell-free zone near the odontoblasts. The pulp shapes change from development to maturity as the root forms and remodels. It is divided into coronal and radicular portions, connected through the apical foramen.
The document summarizes the key developmental changes that occur during the 2nd week of human development from days 8 to 13. During this period, the blastocyst implants into the uterine wall and differentiates into the trophoblast and inner cell mass. The trophoblast secretes HCG and further differentiates into the cytotrophoblast and syncytiotrophoblast layers. The inner cell mass forms the hypoblast and epiblast layers that make up the bilaminar embryonic disc. By day 13, the blastocyst is fully embedded and utero-placental circulation is established as maternal blood enters the lacunar network. Germ layers also begin to form the basis for future tissues and organs.
Microvilli, cilia, and flagella are cell surface projections that serve important functions.
Microvilli increase cell surface area and aid in absorption. They cover the intestinal surface and form the brush border. Cilia are shorter projections that beat in a coordinated way to move substances over cell surfaces, such as mucus in the respiratory tract.
Flagella are much longer than cilia and power sperm cell motility through whip-like beating. Both cilia and flagella contain microtubules in their core that extend from basal bodies anchored in the cell.
Eithelial tissue,connective tissue by Dr Jyoti Prakash Pani Associate Profess...phupu
Epithelial and connective tissues are the two main types of tissues in the body. Epithelial tissue lines the outer surfaces and inner cavities of the body. It is classified as single-layered (simple) or multi-layered (stratified) epithelium. Common types include squamous, cuboidal, columnar, transitional, and pseudostratified columnar epithelium. Connective tissue supports and binds other tissues. It contains ground substance and fibers, along with fibroblasts, adipocytes and immune cells. Major forms are loose connective tissue, dense connective tissue, regular dense connective tissue, elastic connective tissue, and reticular connective tissue.
This document provides an overview of the histology of blood vessels, including arteries and veins. It begins by stating the learning objectives of identifying and describing the microscopic structures of elastic arteries, muscular arteries, medium-sized veins, and blood capillaries. The document then provides detailed descriptions of the tunica intima, tunica media, and tunica adventitia layers and their components in different blood vessel types. Key differences between arteries and veins are highlighted, such as arteries having a thicker tunica media than adventitia, while veins have a thinner tunica media. Examples of elastic and muscular arteries are given along with diagrams and microscopic slides.
Enamel is the hardest substance in the human body. It is composed primarily of hydroxyapatite crystals arranged in rods (prisms) that run from the dentin-enamel junction to the outer enamel surface. The basic structural unit of enamel is the enamel rod, which is hexagonal or oval in cross-section. Between the rods is the interrod enamel. Enamel gains its strength through the interweaving of tightly packed hydroxyapatite crystals in parallel alignment within the rods.
This document discusses four types of simple epithelium: squamous, cuboidal, columnar, and pseudostratified. Squamous epithelium is scale-like and found lining blood vessels and body cavities. Cuboidal epithelium lines small ducts and tubules, and can be secretory or absorptive. Columnar epithelium lines ducts of exocrine glands and the stomach, and is adapted for secretion and absorption. Pseudostratified epithelium appears to have multiple layers but actually has cells of different heights contacting the basement membrane, seen in airways.
The dental pulp originates from cranial neural crest cells that migrate into the developing tooth germ. During tooth development, these cells form the dental papilla which becomes the dental pulp. The pulp contains odontoblasts, fibroblasts, undifferentiated mesenchymal cells, and macrophages. It has a cell-rich zone containing blood vessels and a cell-free zone near the odontoblasts. The pulp shapes change from development to maturity as the root forms and remodels. It is divided into coronal and radicular portions, connected through the apical foramen.
The document summarizes the key developmental changes that occur during the 2nd week of human development from days 8 to 13. During this period, the blastocyst implants into the uterine wall and differentiates into the trophoblast and inner cell mass. The trophoblast secretes HCG and further differentiates into the cytotrophoblast and syncytiotrophoblast layers. The inner cell mass forms the hypoblast and epiblast layers that make up the bilaminar embryonic disc. By day 13, the blastocyst is fully embedded and utero-placental circulation is established as maternal blood enters the lacunar network. Germ layers also begin to form the basis for future tissues and organs.
- There are three junctions in the oral mucosa: the mucocutaneous junction between the mucosa and skin, the mucogingival junction between the alveolar mucosa and attached gingiva, and the dentogingival junction between the tooth and gingiva.
- The mucocutaneous junction, also called the vermilion border, is the transitional zone between the lip skin and mucosa. It is characterized by long papillae, large blood vessels, and sensory nerve endings.
- The mucogingival junction can be identified clinically by the mucogingival groove and change in color from pink alveolar mucosa to pale gingiva. Histologically
The document summarizes the histology of oral mucous membrane and its clinical implications. It describes that oral mucosa is classified based on keratinization and location. It has three layers - epithelium, lamina propria, and submucosa. The epithelium can be keratinized or non-keratinized. Keratinized epithelium has four layers while non-keratinized has three layers. Lamina propria contains fibroblasts, collagen and elastic fibers. Submucosa contains salivary glands, blood vessels and nerves. The oral mucosa is subdivided into masticatory, lining and specialized mucosa based on function.
The document summarizes the characteristics, functions, and staining properties of different blood cells observed on blood smears or films. It describes lymphocytes as having a big nucleus and little cytoplasm and functioning in cell-mediated and humoral immunity. Monocytes are described as having a big kidney-shaped nucleus and functioning in phagocytosis and cell-mediated immunity. Neutrophils have a 3-lobed nucleus and function in acute inflammation, while eosinophils have a bilobed nucleus and acidophilic granules and function in allergic-parasitic conditions. Basophils are described as having an S- or Z-shaped nucleus and functioning in allergic conditions and secreting histamine and heparin. Platelets are described
This document discusses different types of epithelial tissues. It defines epithelium and provides terminology used to describe epithelial layers and cell shapes. Several specific types of epithelial tissues are then described, including their structure, function, and location in the body. Simple squamous epithelium lines parts of the lungs, heart, and blood vessels. Simple cuboidal epithelium is found in the kidneys. Simple columnar epithelium lines parts of the digestive tract. Pseudostratified columnar epithelium lines the trachea. Stratified squamous epithelium forms the skin and mouth lining. Transitional epithelium is found in the bladder and urethra.
1. Gastrulation begins around day 14-15 with the formation of the primitive streak on the dorsal surface of the embryo, through which epiblast cells migrate inward to form the mesoderm and endoderm.
2. Cells invaginating the primitive pit move forward to form the notochordal process, which later forms the definitive notochord, a solid cord of cells.
3. By the end of the 4th week, the primitive streak begins to regress and disappear, and the embryonic disc becomes elongated with broad and narrow ends.
Intercellular junctions are specialized structures that allow adhesion and communication between cells in multicellular organisms. There are three main types: gap junctions, tight junctions, and anchoring junctions. Gap junctions consist of channels that connect adjacent cells and allow for signal transfer. Tight junctions form a continuous belt around cells and prevent fluid leakage between epithelial layers. Anchoring junctions include desmosomes, hemidesmosomes, and adherens junctions, which anchor cells to each other and extracellular fluid through various transmembrane proteins and cytoskeletal elements.
A complete lecture of the Histology of Muscle Tissues, taught at First Moscow State Medical University, Moscow, in the Histology department, for the first year English medium foreign medical students.
Cartilage is a resilient and smooth elastic connective tissue, a rubber-like padding that covers and protects the ends of long bones at the joints, and is a structural component of the rib cage, the ear, the nose, the bronchial tubes, the intervertebral discs, and many other body components.
Histology
Junqueira’s Basic Histology Text and Atlas, 15th Ed
The oral mucosa has two main tissue components - stratified squamous epithelium and an underlying connective tissue layer. It has three main functions: protection, sensation, and secretion. The oral mucosa is classified into three types - masticatory mucosa, lining mucosa, and specialized mucosa. Histologically, the oral epithelium consists of basal, prickle, and granular cell layers in keratinized areas, while non-keratinized areas lack granular and cornified layers. The connective tissue layer lies beneath the basement membrane and contains papillae.
A power point presentation made with hard work, collecting material from various authentic and reliable sources. Best ppt for under grad as well as for post grad students.
This document discusses bones, cartilages, and joints. It describes the composition, types and functions of bones, including long bones, flat bones, and irregular bones. It examines bone cells, formation, and healing. The document also details the types of cartilage, including hyaline, elastic, and fibrocartilage. Additionally, it outlines the different types of joints that restrict movement, allow movement, and names some joint abnormalities.
Development of arterial and venous systemRobbinsHobbin
The cardiovascular system begins developing in the third week as the heart starts beating in the fourth week. Between weeks 4-5, pharyngeal arches form and the aortic arches transform into the adult arterial arrangement between weeks 6-8. During this critical period of heart development from 20-50 days after fertilization, anomalies can occur in the development of the pharyngeal arteries and veins. Common anomalies include double aortic arch, right aortic arch, patent ductus arteriosus, and persistent fetal veins. Remnants of fetal vessels include the umbilical arteries, left umbilical vein, ductus venosus, and ductus arteriosus.
The document provides an overview of the anatomy of the thorax, including:
1. The thoracic wall is formed by the vertebral column, ribs, sternum, and intercostal spaces. It protects the lungs and heart and allows for muscle attachment.
2. The mediastinum is the median partition of the thorax that contains structures like the heart, great vessels, esophagus and thoracic duct.
3. The lungs occupy the pleural cavities on either side of the mediastinum. The diaphragm separates the thorax from the abdomen.
The document summarizes the histology of the gastrointestinal tract. It describes the four layers of the GI tract wall - mucosa, submucosa, muscularis, and serosa. It then focuses on specific structures of the stomach, small intestine, and pancreas. Key points include the four regions of the stomach, gastric glands and their role in digestion, villi and crypts in the small intestine, and acini and islets of Langerhans in the pancreas that produce digestive enzymes and hormones. Clinical correlations are provided regarding conditions like atrophic gastritis, pernicious anemia, and acute pancreatitis.
The temporomandibular joint (TMJ) is a synovial joint that connects the mandible to the temporal bone. It has two articulating surfaces: the condylar head of the mandible and the glenoid fossa and articular eminence of the temporal bone. Between these surfaces is the articular disk which divides the joint cavity into upper and lower compartments. The joint is surrounded by a fibrous capsular ligament lined with synovial membrane. The synovial membrane secretes synovial fluid to lubricate and nourish the articulating surfaces. Common clinical issues involving the TMJ include ankylosis where the condyle fuses to the temporal bone, and
The document provides information about the pectoral girdle (shoulder girdle) and associated bones, joints, muscles and movements. It describes the clavicle bone, its articulations in the sternoclavicular and acromioclavicular joints. It also describes the scapula bone and its movements. Key muscles that act on the pectoral girdle and humerus are identified, including their origins, insertions and actions. The major joints of the pectoral girdle, the sternoclavicular and acromioclavicular joints, are also summarized.
The document describes the life cycle of ameloblasts and the process of amelogenesis. There are seven stages in the life cycle of ameloblasts: 1) morphogenic, 2) differentiation, 3) secretory, 4) transitional, 5) maturative, 6) protective, and 7) desmolytic. Amelogenesis involves two processes - formation of the enamel matrix through protein secretion and mineralization through hydroxyapatite deposition and maturation. Defects in amelogenesis can result from conditions like febrile diseases or tetracycline intake, producing malformed or discolored enamel. Enamel undergoes age-related changes like attrition, discoloration, and increased hardness due
The document discusses the lymphatic system. It describes the location and microscopic features of lymphatic organs including lymph nodes, spleen, thymus, and tonsils. It explains the functions of the lymphatic system in reabsorbing excess fluid, transporting lipids, and facilitating immune responses. The components of the lymphatic system include lymph, lymphatic vessels, and lymphatic organs. It provides details on the anatomy and histology of these structures.
Mitosis and the cell cycle are necessary for three key reasons:
1. Asexual reproduction, as seen in binary fission in bacteria.
2. To replace damaged or dead cells through growth and development.
3. Embryonic development in organisms occurs through cell division of cells like bone marrow and frog embryos.
Connective tissue is composed of cells and an extracellular matrix. The extracellular matrix contains fibers such as collagen, elastic fibers, and reticular fibers embedded in a ground substance. Collagen is the most abundant protein and forms fibers that provide strength and structure. Elastic fibers allow tissues to stretch and return to their original shape. Reticular fibers form networks that support organs. The ground substance contains glycosaminoglycans and proteoglycans that lubricate and protect tissues. Fibroblasts are the most common cell type and produce the extracellular matrix.
Connective tissue is composed of cells and an extracellular matrix. The main cell types are fibroblasts, which produce the extracellular matrix, and macrophages, mast cells, and leukocytes which reside in the tissue. The extracellular matrix contains ground substance and fibers, particularly collagen fibers which are abundant and come in many types that provide different structural functions. Fibroblasts play an important role in wound healing by reverting from fibrocytes to an active state to repair damage.
- There are three junctions in the oral mucosa: the mucocutaneous junction between the mucosa and skin, the mucogingival junction between the alveolar mucosa and attached gingiva, and the dentogingival junction between the tooth and gingiva.
- The mucocutaneous junction, also called the vermilion border, is the transitional zone between the lip skin and mucosa. It is characterized by long papillae, large blood vessels, and sensory nerve endings.
- The mucogingival junction can be identified clinically by the mucogingival groove and change in color from pink alveolar mucosa to pale gingiva. Histologically
The document summarizes the histology of oral mucous membrane and its clinical implications. It describes that oral mucosa is classified based on keratinization and location. It has three layers - epithelium, lamina propria, and submucosa. The epithelium can be keratinized or non-keratinized. Keratinized epithelium has four layers while non-keratinized has three layers. Lamina propria contains fibroblasts, collagen and elastic fibers. Submucosa contains salivary glands, blood vessels and nerves. The oral mucosa is subdivided into masticatory, lining and specialized mucosa based on function.
The document summarizes the characteristics, functions, and staining properties of different blood cells observed on blood smears or films. It describes lymphocytes as having a big nucleus and little cytoplasm and functioning in cell-mediated and humoral immunity. Monocytes are described as having a big kidney-shaped nucleus and functioning in phagocytosis and cell-mediated immunity. Neutrophils have a 3-lobed nucleus and function in acute inflammation, while eosinophils have a bilobed nucleus and acidophilic granules and function in allergic-parasitic conditions. Basophils are described as having an S- or Z-shaped nucleus and functioning in allergic conditions and secreting histamine and heparin. Platelets are described
This document discusses different types of epithelial tissues. It defines epithelium and provides terminology used to describe epithelial layers and cell shapes. Several specific types of epithelial tissues are then described, including their structure, function, and location in the body. Simple squamous epithelium lines parts of the lungs, heart, and blood vessels. Simple cuboidal epithelium is found in the kidneys. Simple columnar epithelium lines parts of the digestive tract. Pseudostratified columnar epithelium lines the trachea. Stratified squamous epithelium forms the skin and mouth lining. Transitional epithelium is found in the bladder and urethra.
1. Gastrulation begins around day 14-15 with the formation of the primitive streak on the dorsal surface of the embryo, through which epiblast cells migrate inward to form the mesoderm and endoderm.
2. Cells invaginating the primitive pit move forward to form the notochordal process, which later forms the definitive notochord, a solid cord of cells.
3. By the end of the 4th week, the primitive streak begins to regress and disappear, and the embryonic disc becomes elongated with broad and narrow ends.
Intercellular junctions are specialized structures that allow adhesion and communication between cells in multicellular organisms. There are three main types: gap junctions, tight junctions, and anchoring junctions. Gap junctions consist of channels that connect adjacent cells and allow for signal transfer. Tight junctions form a continuous belt around cells and prevent fluid leakage between epithelial layers. Anchoring junctions include desmosomes, hemidesmosomes, and adherens junctions, which anchor cells to each other and extracellular fluid through various transmembrane proteins and cytoskeletal elements.
A complete lecture of the Histology of Muscle Tissues, taught at First Moscow State Medical University, Moscow, in the Histology department, for the first year English medium foreign medical students.
Cartilage is a resilient and smooth elastic connective tissue, a rubber-like padding that covers and protects the ends of long bones at the joints, and is a structural component of the rib cage, the ear, the nose, the bronchial tubes, the intervertebral discs, and many other body components.
Histology
Junqueira’s Basic Histology Text and Atlas, 15th Ed
The oral mucosa has two main tissue components - stratified squamous epithelium and an underlying connective tissue layer. It has three main functions: protection, sensation, and secretion. The oral mucosa is classified into three types - masticatory mucosa, lining mucosa, and specialized mucosa. Histologically, the oral epithelium consists of basal, prickle, and granular cell layers in keratinized areas, while non-keratinized areas lack granular and cornified layers. The connective tissue layer lies beneath the basement membrane and contains papillae.
A power point presentation made with hard work, collecting material from various authentic and reliable sources. Best ppt for under grad as well as for post grad students.
This document discusses bones, cartilages, and joints. It describes the composition, types and functions of bones, including long bones, flat bones, and irregular bones. It examines bone cells, formation, and healing. The document also details the types of cartilage, including hyaline, elastic, and fibrocartilage. Additionally, it outlines the different types of joints that restrict movement, allow movement, and names some joint abnormalities.
Development of arterial and venous systemRobbinsHobbin
The cardiovascular system begins developing in the third week as the heart starts beating in the fourth week. Between weeks 4-5, pharyngeal arches form and the aortic arches transform into the adult arterial arrangement between weeks 6-8. During this critical period of heart development from 20-50 days after fertilization, anomalies can occur in the development of the pharyngeal arteries and veins. Common anomalies include double aortic arch, right aortic arch, patent ductus arteriosus, and persistent fetal veins. Remnants of fetal vessels include the umbilical arteries, left umbilical vein, ductus venosus, and ductus arteriosus.
The document provides an overview of the anatomy of the thorax, including:
1. The thoracic wall is formed by the vertebral column, ribs, sternum, and intercostal spaces. It protects the lungs and heart and allows for muscle attachment.
2. The mediastinum is the median partition of the thorax that contains structures like the heart, great vessels, esophagus and thoracic duct.
3. The lungs occupy the pleural cavities on either side of the mediastinum. The diaphragm separates the thorax from the abdomen.
The document summarizes the histology of the gastrointestinal tract. It describes the four layers of the GI tract wall - mucosa, submucosa, muscularis, and serosa. It then focuses on specific structures of the stomach, small intestine, and pancreas. Key points include the four regions of the stomach, gastric glands and their role in digestion, villi and crypts in the small intestine, and acini and islets of Langerhans in the pancreas that produce digestive enzymes and hormones. Clinical correlations are provided regarding conditions like atrophic gastritis, pernicious anemia, and acute pancreatitis.
The temporomandibular joint (TMJ) is a synovial joint that connects the mandible to the temporal bone. It has two articulating surfaces: the condylar head of the mandible and the glenoid fossa and articular eminence of the temporal bone. Between these surfaces is the articular disk which divides the joint cavity into upper and lower compartments. The joint is surrounded by a fibrous capsular ligament lined with synovial membrane. The synovial membrane secretes synovial fluid to lubricate and nourish the articulating surfaces. Common clinical issues involving the TMJ include ankylosis where the condyle fuses to the temporal bone, and
The document provides information about the pectoral girdle (shoulder girdle) and associated bones, joints, muscles and movements. It describes the clavicle bone, its articulations in the sternoclavicular and acromioclavicular joints. It also describes the scapula bone and its movements. Key muscles that act on the pectoral girdle and humerus are identified, including their origins, insertions and actions. The major joints of the pectoral girdle, the sternoclavicular and acromioclavicular joints, are also summarized.
The document describes the life cycle of ameloblasts and the process of amelogenesis. There are seven stages in the life cycle of ameloblasts: 1) morphogenic, 2) differentiation, 3) secretory, 4) transitional, 5) maturative, 6) protective, and 7) desmolytic. Amelogenesis involves two processes - formation of the enamel matrix through protein secretion and mineralization through hydroxyapatite deposition and maturation. Defects in amelogenesis can result from conditions like febrile diseases or tetracycline intake, producing malformed or discolored enamel. Enamel undergoes age-related changes like attrition, discoloration, and increased hardness due
The document discusses the lymphatic system. It describes the location and microscopic features of lymphatic organs including lymph nodes, spleen, thymus, and tonsils. It explains the functions of the lymphatic system in reabsorbing excess fluid, transporting lipids, and facilitating immune responses. The components of the lymphatic system include lymph, lymphatic vessels, and lymphatic organs. It provides details on the anatomy and histology of these structures.
Mitosis and the cell cycle are necessary for three key reasons:
1. Asexual reproduction, as seen in binary fission in bacteria.
2. To replace damaged or dead cells through growth and development.
3. Embryonic development in organisms occurs through cell division of cells like bone marrow and frog embryos.
Connective tissue is composed of cells and an extracellular matrix. The extracellular matrix contains fibers such as collagen, elastic fibers, and reticular fibers embedded in a ground substance. Collagen is the most abundant protein and forms fibers that provide strength and structure. Elastic fibers allow tissues to stretch and return to their original shape. Reticular fibers form networks that support organs. The ground substance contains glycosaminoglycans and proteoglycans that lubricate and protect tissues. Fibroblasts are the most common cell type and produce the extracellular matrix.
Connective tissue is composed of cells and an extracellular matrix. The main cell types are fibroblasts, which produce the extracellular matrix, and macrophages, mast cells, and leukocytes which reside in the tissue. The extracellular matrix contains ground substance and fibers, particularly collagen fibers which are abundant and come in many types that provide different structural functions. Fibroblasts play an important role in wound healing by reverting from fibrocytes to an active state to repair damage.
This document provides a summary of cell structure, cell division, Mendel's laws of inheritance, and the chromosomal theory of inheritance. It describes the key components of plant and animal cells, including the cell wall, plasma membrane, nucleus, cytoplasm, organelles, and their functions. It also explains the stages of the cell cycle and both mitosis and meiosis. The document then summarizes Gregor Mendel's experiments with pea plants, his laws of inheritance including dominance, segregation and independent assortment. Finally, it introduces the chromosomal theory of inheritance which links genes to chromosomes.
This document discusses cell organelles. It describes the structures and functions of various membranous organelles like mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, and peroxisomes. It also discusses non-membranous organelles such as ribosomes, cytoskeleton components, centrioles, and cell inclusions. The key organelles and their roles in cellular processes are summarized, with comparisons made between related structures like rough and smooth endoplasmic reticulum. Micrographs are also included to show organelle features under light and electron microscopy.
The document discusses the structure and function of cells. It defines the cell as the basic structural and functional unit of life. Human beings contain billions of cells arranged into over 200 types across four basic tissue groups. The document then describes the key components of cells including the cell membrane, cytoplasm, organelles like mitochondria and lysosomes, and inclusions. It provides detailed information on the structure and functions of the cell membrane and various organelles.
Stem cells can be either embryonic stem cells, isolated from the inner cell mass of blastocysts, or adult stem cells found in adult tissues. Stem cells are undifferentiated cells that can self-renew and differentiate into specialized cell types. There are two major types of blood cells produced through hematopoiesis in the bone marrow: red blood cells and white blood cells (including lymphocytes and myelocytes). Hematopoietic stem cells in the bone marrow give rise to all blood cell types through proliferation and differentiation controlled by growth factors.
Connective tissue is the most abundant tissue in the body and fills spaces between other tissues. It has several components including fibers, ground substance, and cells. The document categorizes connective tissue and describes its various cell types such as fibroblasts that produce collagen fibers, undifferentiated mesenchymal stem cells that can differentiate into other cell types, pigment cells like melanocytes that produce pigment, fat cells that store lipids, and immune cells including lymphocytes, plasma cells, and macrophages. Connective tissue provides structure and support to the body.
This presentation gives you the detailed description of various cells & organs of immune systems that participates (particularly, in combination), make communication between themselves to regulate the whole immune system very precisely.
The document summarizes the key cells found in major human organs and tissues. It describes the mitochondria, intercalated disks, and T-tubules that give heart cells their unique properties. Liver cells include hepatocytes for protein synthesis and recycling, Kupffer cells which are specialized macrophages, and stellate cells which are part of the nervous system. Skin contains melanocytes for producing melanin pigment, Langerhans cells which interact with the immune system, and Merkel cells in hairless skin. Muscle cells contain myofibrils with actin and myosin filaments that power contraction. Blood contains red blood cells, platelets, and five types of white blood cells - neutrophils, eosinoph
Cell structure includes three main parts - the cell membrane, cytoplasm and organelles, and the nucleus. The cell membrane is a thin double layer that encloses the cell. The cytoplasm contains various organelles that carry out specific functions like protein synthesis, energy production, and waste removal. Prominent organelles include the endoplasmic reticulum, mitochondria, Golgi complex and ribosomes. The nucleus is the largest organelle and houses the cell's genetic material in the form of chromatin and chromosomes.
Blood circulates through the body and consists of plasma and three main cell types: red blood cells, white blood cells, and platelets. It performs critical functions like transporting oxygen, nutrients, hormones, and waste. Bone marrow produces blood cells through a process involving sinusoids, adventitial cells, and migration of cells into blood vessels. The spleen, thymus, lymph nodes, and lymphatic system work with bone marrow to produce and transport immune cells throughout the body and remove aging or damaged blood cells from circulation.
This document summarizes connective or supporting tissue. It discusses the main components and functions of connective tissue, including cells, extracellular matrix, and fibers. The key fibers are collagen, reticular, and elastic fibers. The extracellular matrix contains ground substance made of proteoglycans and glycosaminoglycans. Connective tissue cells can be fixed or wandering. Common types of connective tissue include loose connective tissue, dense regular and irregular connective tissue, adipose tissue, elastic tissue, reticular tissue, and hematopoietic tissue. Bone and cartilage are also described as specialized connective tissues.
This document describes different types of cells found in the human body. It discusses epithelial tissue, which covers surfaces and lines body cavities. The main types of epithelial tissue are squamous, columnar, cuboidal, pseudostratified columnar, and transitional epithelium. It also describes connective tissue such as fibroblasts, adipose tissue, and muscle fibers. Finally, it lists different immune/inflammatory cells like polymorphonuclear cells, lymphocytes, eosinophils, and macrophages.
The lymphoid system circulates lymph through vessels and tissues like lymph nodes. It produces lymphocytes in primary organs like the bone marrow, thymus, and spleen. The thymus matures T cells in its cortex and medulla. Bone marrow generates blood cells and prevents backflow of lymph. Secondary organs like lymph nodes initiate immune responses when antigens are presented.
Connective tissue provides structural support for organs and tissues in the body. It is composed of cells and an extracellular matrix containing fibers and ground substance. The three main fiber types are collagen, reticular, and elastic fibers. Collagen is abundant and provides strength, while elastic fibers allow tissues to stretch and return to their original shape. Reticular fibers form networks and support cells. Connective tissue has roles in structure, metabolism, defense, and holds blood vessels. It is derived from mesenchymal cells in embryos.
This document discusses the lymphatic system and its primary and secondary lymphoid organs. It describes that the lymphatic system consists of lymphatic organs and lymph fluid, and lymphoid organs are classified as primary or secondary. Primary lymphoid organs, such as the bone marrow and thymus, are the sites of lymphocyte development. Secondary lymphoid organs, including the spleen, lymph nodes, and MALT tissues, are where adaptive immune responses are initiated through interactions between immune cells and antigens. The document then provides more detailed descriptions of the structure and functions of the thymus, bone marrow, lymph nodes, and spleen as examples of primary and secondary lymphoid organs
The document summarizes key information about blood cells and cell structure as seen under light and electron microscopes. It discusses how blood cells are viewed using magnification and staining. It also describes the structures and functions of the plasma membrane, including the fluid mosaic model, and compares animal and plant cell structures beyond what can be seen with light microscopy alone.
Histology is the study of the microscopic structure of tissues and organs. There are four main tissue types: epithelial, connective, muscle and nervous. Epithelial tissue lines surfaces and forms glands. It is classified as simple or stratified based on the number of cell layers. Connective tissue binds other tissues together and provides support. It contains cells and intercellular substances like fibers and ground substance. Mesenchyme is embryonic connective tissue that can differentiate into other tissues. Key structures in tissues include tight junctions, desmosomes and gap junctions that connect epithelial cells.
The plasma membrane, cytoplasm, and nucleus are the three major parts of the cell. The plasma membrane is a double layer that selectively permits movement of molecules in and out of the cell and protects the cell. The cytoplasm contains organelles and structures that carry out the cell's functions. The nucleus is the control center and contains the cell's genetic material.
This document provides tips for creating successful content on TikTok. It discusses that raw, authentic content focused on providing value works best on TikTok rather than overly produced content. It recommends creating video series rather than focusing on trends. It also provides tips for using hashtags, posting regularly, engaging with your audience, and using hooks and titles to capture viewers' attention. The key takeaway is that TikTok rewards content that provides genuine value to viewers.
This document provides guidelines for preparing an investment proposal (PIN) to present to the Management Investment Committee (MIC) for evaluation. The PIN should address: 1) the profitability of the investment based on internal rate of return estimates, 2) available competitive strategies and the recommended strategy, 3) what must be done well to succeed, and 4) risks and opportunities and their potential impacts. If approved, the assumptions in the PIN will become the objectives for the business. Actual performance will later be compared to targets in a post-audit review at exit. Overhead and depreciation estimates are provided to aid financial evaluations.
The document outlines the key elements that make up a good project funding proposal, including an introduction describing the project aim and qualifications, a need statement, measurable objectives and goals, an evaluation plan, a budget summary and detailed budget, and plans for follow-up funding. A good proposal provides all necessary information on these elements to convince the funding agency to support the project.
The document discusses principles of oral surgery including access, visibility, and flap design. It states that adequate access requires wide mouth opening and retraction of tissues away from the surgical field. Improved access can be gained by creating surgical flaps using incisions. Key principles of incisions and flap design are outlined such as using a sharp blade, firm strokes, avoiding vital structures, and designing flaps to ensure adequate blood supply and healing. Common flap types including triangular, trapezoidal, envelope, and semilunar flaps are described. Careful handling of tissues is also emphasized to minimize damage.
Lecture 3 Facial cosmetic surgery
Maxillofacial Surgery
Dental Students Fifth Year second semester
Al Azhar University Gaza Palestine
Dr. Lama El Banna
https://twitter.com/lama_k_banna
Lecture 1 Facial cosmetic surgery
Maxillofacial Surgery
Dental Students Fifth Year second semester
Al Azhar University Gaza Palestine
Dr. Lama El Banna
https://twitter.com/lama_k_banna
Facial neuropathology Maxillofacial SurgeryLama K Banna
Lecture 4 facial neuropathology
Maxillofacial Surgery
Dental Students Fifth Year second semester
Al Azhar University Gaza Palestine
Dr. Lama El Banna
https://twitter.com/lama_k_banna
Lecture 2 Facial cosmetic surgery
Maxillofacial Surgery
Dental Students Fifth Year second semester
Al Azhar University Gaza Palestine
Dr. Lama El Banna
https://twitter.com/lama_k_banna
Lecture 12 general considerations in treatment of tmdLama K Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name 12 general considerations in the treatment of TMJ
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name TMJ temporomandibular joint
Lecture 10
Al Azhar University Gaza Palestine
Dr. Lama El Banna
https://twitter.com/lama_k_banna
Lecture 11 temporomandibular joint Part 3Lama K Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name TMJ temporomandibular joint Part 3
Lecture 11
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name TMJ anatomy examination 2
Lecture 9
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Lecture 7 correction of dentofacial deformities Part 2Lama K Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name Correction of dentofacial deformities Part 2
Lecture 7
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Lecture 8 management of patients with orofacial cleftsLama K Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name management of patients with orofacial clefts
Lecture 8
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Lecture 5 Diagnosis and management of salivary gland disorders Part 2Lama K Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name Salivary gland 2
Diagnosis and management of salivary gland disorders Part 2
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Lecture 6 correction of dentofacial deformitiesLama K Banna
The document discusses epidemiological studies that estimate the prevalence of malocclusion and dentofacial deformities in the United States population. The National Health and Nutrition Examination Survey found that approximately 2% of the US population has severe mandibular deficiency or vertical maxillary excess, while other abnormalities such as mandibular excess or open bite affect about 0.3-0.1% of the population. Overall, about 2.7% of Americans may have dentofacial deformities severe enough to require surgical treatment along with orthodontics.
lecture 4 Diagnosis and management of salivary gland disordersLama K Banna
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name Salivary gland
Diagnosis and management of salivary gland disorders
Al Azhar University Gaza Palestine
Dr. Lama El Banna
This document discusses principles of managing panfacial fractures, including anatomic considerations of the craniofacial skeleton and buttresses. It describes two main theories for management: bottom up/inside out and top down/outside in. Reduction, fixation, immobilization and early return of function are discussed. Closed reduction uses manipulation without visualization, while open reduction allows visualization but requires surgery. Various fixation methods are outlined, including arch bars, wiring techniques, and maxillomandibular fixation.
Maxillofacial Surgery
Dental Students Fifth Year First semester
Lecture Name maxillofacial trauma part 2
Al Azhar University Gaza Palestine
Dr. Lama El Banna
Promoting Wellbeing - Applied Social Psychology - Psychology SuperNotesPsychoTech Services
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Mercurius is named after the roman god mercurius, the god of trade and science. The planet mercurius is named after the same god. Mercurius is sometimes called hydrargyrum, means ‘watery silver’. Its shine and colour are very similar to silver, but mercury is a fluid at room temperatures. The name quick silver is a translation of hydrargyrum, where the word quick describes its tendency to scatter away in all directions.
The droplets have a tendency to conglomerate to one big mass, but on being shaken they fall apart into countless little droplets again. It is used to ignite explosives, like mercury fulminate, the explosive character is one of its general themes.
The skin is the largest organ and its health plays a vital role among the other sense organs. The skin concerns like acne breakout, psoriasis, or anything similar along the lines, finding a qualified and experienced dermatologist becomes paramount.
Adhd Medication Shortage Uk - trinexpharmacy.comreignlana06
The UK is currently facing a Adhd Medication Shortage Uk, which has left many patients and their families grappling with uncertainty and frustration. ADHD, or Attention Deficit Hyperactivity Disorder, is a chronic condition that requires consistent medication to manage effectively. This shortage has highlighted the critical role these medications play in the daily lives of those affected by ADHD. Contact : +1 (747) 209 – 3649 E-mail : sales@trinexpharmacy.com
Kosmoderma Academy, a leading institution in the field of dermatology and aesthetics, offers comprehensive courses in cosmetology and trichology. Our specialized courses on PRP (Hair), DR+Growth Factor, GFC, and Qr678 are designed to equip practitioners with advanced skills and knowledge to excel in hair restoration and growth treatments.
- Video recording of this lecture in English language: https://youtu.be/Pt1nA32sdHQ
- Video recording of this lecture in Arabic language: https://youtu.be/uFdc9F0rlP0
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
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8 Surprising Reasons To Meditate 40 Minutes A Day That Can Change Your Life.pptxHolistified Wellness
We’re talking about Vedic Meditation, a form of meditation that has been around for at least 5,000 years. Back then, the people who lived in the Indus Valley, now known as India and Pakistan, practised meditation as a fundamental part of daily life. This knowledge that has given us yoga and Ayurveda, was known as Veda, hence the name Vedic. And though there are some written records, the practice has been passed down verbally from generation to generation.
2. Origin:
Mesoderm , Mesenchymal Tissue [undifferentiated mesenchymal cells (UMCs) +
Matrix].
Characteristics:
1- It is mesodermal in origin.
2- It is formed of widely separated cells with large amount of ground intercellular
substances (matrix).
3- It is penetrated by blood vessels, lymphatics and nerves.
4- It connects, supports and protects other tissues & organs.
Components:
C.T. consists of 3 main components:
1- Cells
2- Fibers
3- Matrix
A- soft..........................C.T. proper
B- Fixed rubbery..........cartilage
C- solid……………… bone
D-fluid………………. blood
CONNECTIVE TISSUE PROPER
Structural composition:
1) Cells: Fixed & free.
2) Fibers: Collagenous, elastic & reticular.
3) Matrix: Soft (jelly like).
C.T Cells
Fixed Free
1. UMCs 8. Plasma cells
2. Pericytes 9. Mast cells
3. Endothelial cells 10. Free macrophages
4. Fibroblasts 11. Leukocytes
5. Fat cells 12. Pigment cells
6. Fixed macrophages
(Histiocytes)
7. Reticular cells
3. The fixed cells are the intrinsic component of the C.T., they are the stable
population of long lived cells.
They are produced in the C.T. & remain in it.
The free cells changeable population, they are motile cells, belonging
to the immune system, entering the C.T. from the blood, and wander through it.
They are short lived, and continuously replaced from the blood.
A- Fixed C.T. Cells
1- Undifferentiated Mesenchymal Cells (UMCs):
Sites:
• Unspecialized stem cells present in the embryo.
• They have the ability to differentiate into other types of C.T. cells (mother
cells).
• In adult, they remain undifferentiated in certain areas to act as a life-long
source for some cells e.g.:
4. - in bone marrow —>• blood cells.
- around blood vessels —≫pericytes.
• Small, irregular, branched star (stellate) shaped cells.
• Pale basophilic cytoplasm.
• Central large oval nucleus with visible nucleoli.
EM: few organelles, many ribosomes & fine chromatin in the nucleus.
Functions:
1- Can differentiate into other types of C.T. cells.
2- In bone marrow, it gives blood cells.
2- Pericytes:
Sites:
• Present around blood capillaries.
• They are considered UMCs of the adults.
LM: branched, with oval nucleus & pale
cytoplasm.
Functions:
1- The same functions of UMCs but after birth.
2- After birth they give rise to fibroblasts & smooth
muscles (during healing).
3- Their contraction leads to vaso-constriction.
3 - Endothelial Cells:
Sites: Lining all blood vessels & heart.
LM: Thin flat squamous epithelium with flat
nucleus, little cytoplasm & few organelles
around the nucleus.
Functions:
1- Can divide to produce new endothelial cells
in injury.
2- Can produce their own basement membrane.
3- Can produce antithrombotic factors, which prevent
platelet aggregation.
4- Can produce collagen (type 4).
4 - Fibroblasts:
Origin: UMCs & Pericytes.
Sites: the most common type; found nearly in all types of C.T. proper.
LM:
• Flat, elongated, branched cells, with thin processes, (fusiform in side view).
5. • Large, pale, oval nucleus & prominent nucleolus.
• Deeply basophilic cytoplasm.
EM:
• Euchromatic nucleus & large nucleolus.
• Large amount of rER & free ribosomes.
• Well developed Golgi apparatus.
• Mitochondria.
N.B.: these are the EM picture of cells
active in protein synthesis. EM picture of flbrob|ast
Functions:
1) Formation of C.T. fibers by secretion of their
proteins (procollagen and
elastin, that form collagenous, elastic & reticular
fibers).
2) Secretion of the ground substances of the matrix,
i.e. the cells that build theC.T.
3) Healing & repair of C.T. after injury.
N.B: Fibrocytes:
• They are old inactive fibroblasts.
• They are smaller, spindle shaped with fewer
processes.
• Less basophilic cytoplasm with darker nuclei.
• Smaller amount of rER.
Functions of fibrocytes:
Continuous slow turnover of extracellular
components, for maintenance of C.T.
5 - Fat Cells (Adipocytes):
Origin: UMC Lipoblast:
A- Unilocular adipocyte (white fat cells)
B- Multilocular adipocyte (brown fat cells)
A- Unilocular fat cell:
- Sites: most abundant in white adipose C.T.
LM:
• Rounded or oval, large (120 ɱm) cells.
• Nucleus is peripheral & flattened.
• Cytoplasm is reduced into a very thin film around a large fat globule.
6. • In H & E —> fat dissolves, so cells appear as large
vacuoles (signet-ring appearance).
• In frozen sections, it stains orange with Sudan III.
EM: fat droplets appear as electron-dense (black)
inclusion that occupies most of cytoplasm.
Functions:
1- Storage of fat.
2- Support some organs e.g. kidney.
3- Heat insulator.
N.B.: fat cells do not divide, but have a long life span.
B- Multilocular fat cell:
Sites: present in brown adipose C.T.
LM: small rounded cells with central rounded nucleus
and many small fat droplets. They have many
mitochondria, so appear brown due to the cytochrome
pigments present in the mitochondria.
Functions: heat generation.
6 - Fixed Macrophages (Histiocytes):
Origin: from mesenchyme derived monocytes (a type of
white blood cells).
They are described as fixed or resident when they are
attached to fibers.
Sites: scattered in the C.T. along the collagen fibers.
LM:
• Large branched cell with irregular cell boundary
pseudopodia), so they have variable shapes, may be
fusiform or stellate.
• It has darkly stained, small, oval or kidney shaped
nucleus.
• Its cytoplasm is acidophilic, granular and vacuolated.
• Can be demonstrated with vital stains as trypan blue or Indian ink, where the stain
granules are phagocytosed by the cells.
EM:
• The surface of macrophage is irregular due to
pseudopodia, surface folds
and microvilli.
• The cytoplasm contains large particles that these cells
have phagocytosed.
7. •Lysosmes, primary & different types of secondary lysosomes, which attack and
degrade the ingested materials, also residual bodies that contain indigestible remains.
• Few cisterns of rER, prominent Golgi (from which arise the lysosomes).
• In certain conditions macrophages fuse and form large multinucleated cells called
foreign body giant cells that are able to phagocytose large foreign materials. N.B.:
Giant cells are common in tuberculosis, and in chronic nodular lesions called
granulomas.
Functions:
1. Phagocytic cell (engulf & digest micro-organisms).
2. Clean wounds from any dead cells (debris).
3. Interaction with lymphocytes & neutrophils by producing interleukins which
stimulate attraction of neutrophils and mitosis of lymphocytes.
4. Act as antigen presenting cells; they can trap, transport & partially digest antigens
to present them to lymphocytes.
5.Histiocytes can fuse with each other to form large multinucleated cell(Foreign
Body Giant cell) to engulf large foreign bodies.
6.Destruction of old RBCs in liver & spleen.
7 - Reticular Cells:
Site: in stroma of different organs.
LM: small stellate shaped branched cells with long
processes. They form a reticulum together with
reticular fibers which stain with silver stain.
Functions:
1.Supportive function.
2.Can act as phagocytic cells on need, i.e. when stimulated
with an antigen.
3.Can differentiate into blood cells in bone marrow.
B- Free C.T. Cells
8 - Plasma Cells
Origin: from further differentiation of Blymphocytes
(B-lymphocyte plasmablast
plasma cell).
Sites: abundant in lymphoid tissue.
LM:
• Oval cell with rounded eccentric nucleus & a clear
nucleolus.
• The nucleus has a cart-wheel or clock-face appearance
8. due to regular radiating chromatin masses under the nuclear
membrane.
• The cytoplasm is deeply basophilic with a pale(unstained
area) “negative Golgi image” near the nucleus.
EM:
Features of cells active in protein synthesis:
• Well developed Golgi apparatus.
• Closely spaced numerous cisternae of rER filling the
cytoplasm.
• Mitochondria.
Functions:
formation & secretion of antibodies.
9 - Mast Cells:
Origin: UMCs in bone marrow.
Sites:
• In loose C.T. around blood vessels.
• Under epithelium of respiratory & digestive tracts.
LM:
•Oval cells with eccentric nuclei.
•Cytoplasm is full of basophilic granules which stain
metachromatically with basic stains (e.g. toluidine blue),
so they stain purple or red instead of blue.
EM: Features of secretory cells:
• Well developed Golgi.
• Mitochondria, rER.
• Electron-dense membrane-bounded granules filling the
cytoplasm.
Functions:
1- Secretion of histamine which causes vasodilation that
initiates allergic reactions.
2- Secretion of heparin (anticoagulant) which prevents
blood clotting.
3- Secretion of eosinophil chemotactic factor, which
attracts eosinophils to
site of allergy.
9. 10 - Free Macrophages:
Origin: Arise from blood monocytes, which circulate in the blood stream
then migrate to the loose C.T. where they undergo direct transformation into
macrophages. They are described free as they are wandering in the C.T.
LM: They have the same features of fixed macrophages as they are the
same cell, but at different sites.
Functions: They have the same function as fixed macrophages.
11 - Blood Leukocytes:
Origin: All blood leukocytes migrate from blood stream to C.T. to perform
their defensive functions (wandering cells) (see blood for their structures &
functions).
12 - Pigment Cells (Melanophores):
Origin: C.T. macrophages which phagocytose melanin pigments produced
in melanocytes.
Sites: C.T. dermis of skin & eye.
LM:
Small branched cells with small dark nuclei, cytoplasm
is granular.
EM:
Cytoplasm is full of melanin granules(melanosomes).
Functions:
1- Carry melanin pigments which gives
the color of the skin
2- Absorb ultraviolet rays and protect the skin from the injurious effect of
the sun.
II- Connective Tissue Fibers
The C.T. fibers are formed of protein molecules that polymerize to form thin threads.
There are three types of C.T. fibers:
1- White Collagenous fibers.
2- Yellow Elastic fibers.
3- Reticular fibers.
10. 1- White Collagenous Fibers:
Structure:
They are formed by aggregation of tropocollagen molecules secreted mainly by
fibroblasts and other cells as chondroblasts, osteoblasts and odontoblasts.
N.B.: collagen protein is the most abundant protein in the human body.
L.M
• In histological preparations, they appear as wavy branching bundles, formed of non-
branching fibers.
• They are colorless when single, white when condensed, so they are called white
fibers, e.g. in tendons & aponeuroses.
• Fibers are parallel to each other in the bundles.
• They are acidophilic in staining.
- H & E pink.
- Mallory's stain blue.
- Van Gieson's stain red.
Characters:
• They are soft, strong, flexible but not elastic.
• Collagen protein can be digested by pepsin & tiypsin enzymes, and is affected by
boiling (transforming into gelatin), acids and alkalies(tanning).
Functions:
give strength and rigidity to tissues, and resist pulling forces.
2 - Yellow Elastic Fibers:
Shape:
• They are formed of thin, long, branching fibers.
• Fibers are stretchable and yellow in color in fresh state.
• They run singly not in bundles, but branch and anastomose to form networks.
11. Structure:
Elastic fiber formed of a core of elastin protein synthesized in
fibroblasts, surrounded with a sheath of microfibirils of a glycoprotein called fibrillin.
Characters:
Resistant to boiling & chemicals, resist digestion by enzymes as
usual proteases, but can be digested by pancreatic elastase.
Staining:
• H & E pink.
• Orcein stain brown.
• Van Gieson's stain yellow.
Functions:
They provide the tissue with the power of stretch and elasticity.
3 - Reticular Fibers:
Shape:
They are formed of delicate (very thin) fibers that branch & anastomose to form
network or reticulum.
Structure:
They are formed of a thin type of collagen (type III).
Staining:
Silver stain brown to black (argyrophilic).
Functions:
Form the stroma of organs (the background).
Ground Substance (Matrix)
• Definition:
It is the inter-cellular substance in which cells & fibers are embedded. It is
amorphous, jelly like, and translucent.
• Structure:
it is formed of a viscid substance which has a complex mixture of:
1- Proteoglycans (glycosaminoglvcans, GAGs):
2- Glycoproteins:
3- Tissue fluid: salvation water surrounding these structures, similar to plasma.
• Staining:
- Ground substance can be stained metachromatically with basic stains as toluidine
blue giving purple color.
- PAS red color
- Silver brown color.
12. • Functions:
1 - Through its aqueous phase all nutrients & gasses and wastes pass between
blood and cells.
2- Cells & fibers are bonded.
3- It acts as a physical barrier for spread of bacteria and microorganisms.
Types of Connective Tissue Proper
According to the relative abundance of the basic components of C.T. (cells,
fibers & matrix) C.T. is classified into two classes:
A- Loose Types of Connective Tissue Proper
1- Loose (Areolar) Connective Tissue:
It is the typical and the most common type of
C.T. proper.
Structure:
• Cells: It contains all types of C.T. cells (most
common cells are fibroblasts, macrophages, fat
cells and mast cells).
• Fibers: All types, white collagenous is the
most common.
• Matrix: most abundant matrix.
Characters:
• It is a loose type that contains potential
cavities (areolae) which can accommodate large
amounts of fluids or gasses.
• Delicate consistency, flexible, well vascularized & nonresistant to stress.
13. Sites:
• Found every where in the body (except the brain):
• Packing and filling the spaces between cells & fibers and organs, e.g. subcutaneous
tissue (dermis ot skm) .
• Submucosa, serous membranes.
• Around blood vessels & nerves along their course.
Functions:
1- Exchange of nutrients to & from blood vessels.
2- It binds structures together.
3- It limits the spread of infection.
2- Adipose Connective Tissue:
Similar to areolar C.T. but fat cells predominate over other components.
Structure:
• Cells: It is formed of a large number of fat cells, closely packed few fibroblasts,
Mast cells & lymphocytes are scattered in the narrow spaces between fat cells.
• Fibers: reticular fibers form a network around the fat cells,Collagen and elastic
fibers are present in between the lobules of fat cells.
Types of adipose tissue:
There are two types according to vascularity & functions:
a) White adipose connective tissue:
Sites:
• Widely distributed in the body.
• Under the skin especially in females, e.g. mammary gland, gluteal region, abdominal
wall & mesentery.
• Around the kidney & blood vessels.
Characters:
• Fat cells are large (up to 150 |im), filled with one globule of nonpigmented yellowish
fat.
• It is poor in blood supply and is affected by diet & hormones.
Functions:
1- Storage of fat.
2- Heat insulation.
3- Support the kidney and other organs.
4- Gives the skin its shape and contour,
b) Brown adipose connective tissue:
Sites:
present in limited areas: interscapular region, mediastinal region & axillary region in
embryo and newborn & is gradually replaced by white fat.
14. Character:
• Fat cells are small in size with central nucleus, filled with multiple small droplets of
pigmented fat.
• Its brown color is due to cytochrome pigments in mitochondria &high vascularity. It
is not affected by starvation.
Functions:
• Heat generation in newly bom infants.
• Release of heat on exposure to cold to warm the body.
3- Reticular Connective Tissue:
Delicate type.
Structure:
• Cells: primitive fibroblasts, called reticular cells. They are stellate with long
processes which are joined with cell junctions.
• Fibers: fine network of branching reticular fibers, forming) network with the cells.
Sites:
It forms the framework (stroma) for cellular solid organs (to support the functioning
cells, e.g. lymphatic organs (spleen & lymph node), kidney, liver, bone marrow, lung
and all endocrine glands.
Staining:
Silver stain (Ag) brown black.
15. 4- Mucoid Connective Tissue:
It is an embryonic, jelly-like C.T., in which the ground
substance predominates.
Structure:
• Cells: mesenchymal cells or young fibroblasts which
are stellate, branched with multiple connected
processes.
• Fibers: very fine collagen and reticular fibers.
• Matrix: large amount of soft, jelly-like ground
substance, rich in mucus and
hyaluronic acid.
Sites:
Umbilical cord, where it forms the main component
and is called Wharton’s Jelly.
B- Dense Types of Connective Tissue Proper
5- White Fibrous Connective Tissue:
Very dense due to great predominance of collagen fibers with few cells.
Structure:
• Fibers: packed collagen fibers in bundles.
• Matrix: minimal amount (poor in blood supply).
• Cells: fibroblasts (tendon cells). Fibroblasts are enclosed between the packed
collagen fibers.
Characters:
appears white in fresh state, less flexible & more resistant.
Types:
according to the arrangement of bundles of collagen fibers, there are two types:
a) Regular white fibrous connective tissue:
The bundles of collagen are arranged regularly & parallel.
Fibroblasts are arranged in rows in between the collagen
bundles (tendon cells), with very little amount of matrix.
Sites:
• Tendons of skeletal muscles.
• Cornea: under the epithelium.
Function: to withstand stretch in one direction.
16. b) Irregular white fibrous connective tissue:
The bundles of collagen fibers are interwoven & irregularly arranged.
Sites:
• Dermis of the skin.
• Capsule of organs & ligaments.
• Periosteum & perichonderium.
• Sclera of the eye.
Function: to withstand stretch in different directions.
6- Yellow Elastic Connective Tissue:
Dense type, with great predominance of elastic fibers, so it appears yellow in fresh
state.
Structure:
• Fibers: regular parallel elastic fibers.
• Cells: few fibtroblasts & fibrocytes.
Sites:
• Aorta & large arteries.
• Bronchi, bronchioles & around alveoli.
• Ligaments (e.g. ligamentum flavum: joining the vertebrae, ligamentum nuchae: at
the back of the neck especially animals & suspensory ligaments of the penis).
• Vocal cords.
17. Staining:
Orcein stain brown black.
Function:
• It forms elastic membranes.
• It has a great elastic power (recoil when stretched, i.e. rubber like).
CARTILAGE
Definition :
it is a specialized type of C.T in which the matrix is rigid to bear mechanical stress.
Characters of cartilage:
• It resembles C.T. proper in that the cells are widely separated by a considerable
amount of intercellular material (matrix).
• Being a type of C.T., it arises from primitive mesenchymal cells (UMCs).
• The matrix is rigid (firm) but flexible. It is formed of ground substance in which the
cells & fibers are embedded.
• It is avascular (non-vascular), nourished by diffusion of 0 2 & nutrients from the
surrounding C.T. or synovial fluid in the joint cavities.
• It has no lymph vessels or nerves.
Functions of cartilage:
• Support soft tissues with some flexibility, tissue attachment & weight bearing.
• Keeps airway patent.
• Shock-absorbing, as it is resilient.
• Smooth sliding surface for joints (for easy movement of bones).
• Development and growth of bones, before and after birth.
Composition of cartilage:
like other C.T. it is formed of cells, fibers and ground substance:
• The Cells are called chondroblasts and chondrocytes.
• The Fibers are collagen and elastic fibers, which are embedded, in varying
proportions, in the ground substance to form the matrix.
• The Matrix, which is abundant, firm & compact.
Types of cartilage:
• There are three types of cartilage based on the amount of ground substance,
relative abundance and type of fibers embedded in it, which makes the
18. different types of cartilage vary in appearance and mechanical properties.
These types are hyaline, yellow elastic and white flbrocartilage.
Hyaline cartilage
has the typical structure of cartilage. The other types are considered as variants of
its basic structure.
The most common type.
It appears translucent, with glassy appearance, (Hyalo = glass).
Sites:
1- Fetal skeleton
2- 2- Epiphyseal plate
3- Costal cartilage
4- 4- Articular surface of bones
5- Respiratory passages (nose, larynx, trachea & bronchi).
Structure:
A) Perichondrium: it is a capsule-like structure formed of dense fibrous C.T.
that surrounds the hyaline cartilage except at the articular surface of joints.
It is formed of two layers:
1- Outer fibrous layer: white fibrous C.T., formed of fibroblasts, which secrete the
collagen fibers (Type I), it is rich in blood vessels & nerves.
2- Inner chondrogenic (cellular): rich in chondrogenic cells that differentiate into
chondroblasts. They are flat or oval cells with dark basophilic cytoplasm, which
secrete the matrix of cartilage & collagen(type II).
19. Functions of perichondrium:
•Nutrition of non-vascular cartilage (by diffusion).
• Formation of new cartilage cells during growth.
• Provides attachment for muscles.
B) Cartilage Cells:
1- Chondroblasts (young chondrocytes):
Origin: arise from mesenchyme (UMCs), which withdraw their processes, proliferate
and become crowded. They are transformed into chondrogenic cells that enlarge and
differentiate into chondroblasts which start to secrete the matrix.
Site: always on the surface of cartilage, at the inner aspect of perichondrium.
LM:
• Flat to oval or spindle in shape, with deep basophilic cytoplasm
• Flat oval pale stained nucleus, with prominent nucleolus.
• It can divide.
EM:
features of protein forming cells (euchromatic nucleus, abundant ribosomes, rER,
large Golgi apparatus & many mitochondria).
Functions:
1.Formation of cartilage matrix.
2.Formation of cartilage collagen (type II).
3. Cartilage growth from outside (appositional growth).
4. They secrete matrix and when surrounded with it they become called chondrocytes.
2- Chondrocytes: They are the mature cartilage cells.
Origin: they develop from chondroblasts. When chondroblasts mature, they secrete
enough matrix to be completely surrounded by it and imprisoned in lacunae, they are
now called chondrocytes.
LM.:
• Rounded with pale basophilic cytoplasm and central rounded dark nucleus.
• Rounded darkly stained central nucleus.
• Embedded in the matrix inside spaces called lacunae, either single forming primary
lacunae or divide once or twice giving clusters of cells formed of 2 or 4, up to 8 cells
in secondary lacunae surrounded by capsule of condensed matrix.
• The superficial cells are small, flat, oval and single in their lacunae & parallel to the
surface.
• The older cells become deeper in the matrix. They are rounded or triangular, with
pale cytoplasm (rich in fat & glycogen which dissolve during preparation). They are
found in groups (2, 4 & 8) surrounded with darkly stained capsule of matrix, which is
due to more condensation of matrix ground substance (GAGs), forming a more
basophilic line. This group of cells is called cell nest.
20. NB:
During life, chondrocytes completely fill the lacunae, but during tissue preparation,
the cells frequently shrink, so the lacunae appear as empty spaces.
EM.:
Features of protein forming cells, in addition mature chondrocytes show large lipid
droplets and glycogen granules
Functions:
Maintain the cartilage matrix, by continuous turnover, like the chondroblasts. They
are responsible for the formation and secretion of matrix components.
C) Fibers:
Collagen fibers (type II), which are very fine type of collagen, embedded in the
matrix. However they can’t be seen by LM and the ground substance appears
homogenous, and transparent. This is because:
- They are very thin, less than the resolution power of LM.
- They have the same refractive index as the surrounding matrix.
- N.B.: They can be seen after digestion of the matrix by enzymes.
D) Ground substance (Matrix):
• It is produced by chondroblasts and chondrocytes.
• It is rubbery, homogenous, transparent and markedly basophilic. It also stains
metachromatically with some basic stains.
• The matrix consists of: proteoglycans, glycoproteins and water.
Yellow Elastic Fibers
It is yellow in fresh state, more opaque & flexible.
Structure:
• Covered by perichondrium.
• Has the same structure of hyaline cartilage, but with large number of branching
elastic fibers embedded in the matrix forming a network that gives this type the
yellow color, with few collagen fibers (type II).
• Cells are chondrocytes in lacunae that form small cell nests (mostly 2 cell isogenous
groups).
Sites:
it is found where support with flexibility is required:
• Ear pinna.
• Eustachian tube.
• Epiglottis and some laryngeal cartilages
• External auditoiy canal.
Functions:
•it is very flexible, recovers its shape after being deformed.
21. White Fibro Cartilage
•It is not surrounded with perichondrium.
•It is a tough type of cartilage which is important in bone to bone attachment.
•It has intermediate character between hyaline cartilage and
Dense regular white fibrous C.T.
Structure:
• It is formed of dense collagen fibers (type I), present in parallel thick bundles.
•Cartilage cells inside lacunae are present in rows between collagen bundles,
embedded in very scanty matrix around them
Sites:
•Mandibular joint.
•Sternoclavicular joint.
• Intervertebral disc.
• Symphysis pubis.
• Cartilage around the hip (acetabulum) and shoulder (glenoid cavity) joints.
• Semilunar cartilages of knee joints.
Functions:
•It is a strong and tough type that can resist reat tensile stretch.
•It attaches bone to bone with limited mobility.
Structure of the intervertebral disc:
•It is present between the bodies of two adjacent vertebrae.
22. •It is formed of an outer fibrous ring formed of white fibrocartilage (collagen type I),
called annulus fibrosus, and an inner soft jelly-like inner mass containing collagen
type II, called nucleus pulposus.
Clinical note: Herniation o f the nucleus pulposus from the annulus fibrosus, a
condition called disc prolapse, can con foress the nerve roots causing severe
pain.
Growth of Cartilage
1- Appositional growth (Exogenous): It is the growth resulting from the
addition of new layers of cartilage to the surface by the activity of the inner
cellular layers of perichondrium (chondroblasts).
2- Interstitial growth: It is the growth of cartilage from inside by division of
young chondrocytes which proliferate and produce matrix around them.
BONE
Definition:
• It is a hard, strong and vascular specialized type of C.T.
• It is formed, as any C.T. of 3 main components, bone cells & fibers (collagen type I)
embedded in solid matrix.
• The matrix is solid due to deposition of mineral salts (mainly calcium and
phosphorus) in the osteoid tissue (which is the ground substance in which collagen
fibers are embedded).
• Bone is covered from the external surface by a specialized fibrous C.T. membrane
(the periosteum) and lined from the internal surface with loose cellular C.T. layer (the
endosteum) in most areas
Functions of bone:
1- It forms the adult skeleton.
2- It supports fleshy structures.
3- It protects the vital organs (brain, heart and lungs).
4- It selves as a reservoir for calcium & phosphorus.
Shape:
(Anatomical classification)
1- Long bones e.g. bones of limbs.
2- Short bones e.g. bones of hands &feet.
23. 3- Flat bones e.g. diploe of the skull, scapula, sternum and ribs.
4- Irregular bones e.g.: vertebrae.
Types of bone: (Histological classification)
1- Compact (regular) or Ivory bone.
2- Cancellous (irregular) or Spongy bone.
Methods of preparation of bone sections:
Bone is a hard tissue, which can not be processed and cut with the microtome,
so special techniques are used for its study:
1- Decalcified bone sections:
• Calcium salts are dissolved by treating the bones with a mineral acid as nitric acid
10%.
• The bones will change into soft tissue that can be processed, cut & stained.
• This method allows the study of soft tissue of bone; (periosteum, endosteum, cells
&organic matrix).
2- Ground bone sections:
• Bone is left to dry in air, then grinding or sawing it into veiy thin transparent slices
by special carborandum wheel or a saw.
• Thin sections are mounted on the slides, examined without stain.
• By this method calcium is preserved, dead soft tissues are replaced by air which
appears black. This method allows the study of hard matrix(calcified bone lamellae),
lacunae & canalicular system
Structure of Bone:
A- Bone Matrix.
B- Bone cells (osteogenic cells, osteoblasts, osteocytes & osteoclasts).
C- Periosteum & endosteum.
A- Bone Matrix
It consists of closely packed layers (lamellae) of calcified collagen bundles, embedded
in amoiphous calcified intercellular substance.
1- Organic component (osteoid): 35% of bone weight, consists of:
• Fibers: collagen fibers mostly (type 1), which form 90% of the organic portion, that
is why bone matrix is highly acidophilic in decalcified H&E
• Ground substance: rich in carbohydrates & proteins (proteoglycans and
glycoproteins).
• Glycosaminoglycans: sulfated as chondroitin sulfate and keratan sulfate, and non-
sulfated as hyaluronic acid.
24. • Glycoproteins: osteocalcin and osteopontin.
•This organic part of the matrix is secreted by the bone cells prior to mineralization.
2- Inorganic component: 65% of bone weight, formed mainly of Ca phosphate,
carbonate, citrate and hydroxide. It also contains magnesium, potassium and sodium.
They lie alongside collagen fibers, and contribute for the lamellar appearance of bone
3- Water: a layer of water & ions surrounding these crystals called hydration shell
which facilitates the exchange of ions between crystals & body fluids.
There are 4 types of bone cells:
1- Osteogenic Cells (Osteoprogenitor Cells)
Origin:
UMCs & pericytes. It is the stem cell derived from embiyonic mesenchyme.
Site:
at the inner layer of periosteum and in the endosteum.
LM:
flat cells with flat dark nuclei & pale basophilic cytoplasm.
EM:
Few organelles (ribosomes & centrioles), i.e. features of mitotically active cells.
Functions:
• It is the main stem cell that gives origin to other types of bone cells. They are
active in bone growth during embiyonic life. In adults, they are active during
bone fractures and repair.
• In low O2 tension (avascular medium) they may change into chondrogenic sections.
2- Osteoblasts (Bone Forming Cells)
Origin:
osteogenic cells.
Site:
at the inner cellular layer of the periosteum and in
the endosteum (always at the growing surfaces of
bone).
LM:
• Oval branched cells with few processes, rounded
eccentric pale nuclei & prominent
nucleoli. The cytoplasm is deeply basophilic, it may show an unstained area called
negative Golgi image.
25. • Its cytoplasm is very rich in alkaline phosphatase enzyme.
• When these cells are active in bone formation, they increase in height and are
seen arranged on the bony surfaces giving an epithelial-like appearance as a
layer of oval, cubical or columnar cells, but with gaps between cells.
EM:
all features of actively secreting cells: extensive rER, large Golgi, many free
ribosomes, plenty of mitochondria and many secretory vesicles.
Functions:
they are the bone building cells as they are responsible for:
1- Synthesis of organic matrix of bone (osteoid).
2- Secretion of alkaline phosphatase which attracts the Ca salts from blood to be
deposited in the matrix around osteoblasts and their processes.
3- When osteoblasts are surrounded with the newly formed matrix, imprisoned
in spaces called lacunae, they mature and transform into osteocytes.
3- Osteocytes (Mature Bone Cells)
Origin:
osteoblasts.
Site:
present singly inside bony lacunae,
between bone lamellae. Cells are
communicated with each other through the
canaliculi, which connect lacunae together.
LM:
• Smaller than osteoblasts.
• Small, oval, flat, branched cells with small oval dark nuclei, faint basophilic
cytoplasm.
• Each cell lies inside a small cavity (lacuna) and lacunae are connected by canaliculi
through which osteocyte processes are connected by gap
junctions.
EM:
•Features of active cells, but they contain less rER
andsmaller Golgi than osteoblasts. •The cells have thin
processes that extend inside the cylindrical bony canaliculi
in which the adjacent cell processes of the neighboring
osteocytes are connected by gap junctions, so the cells are
intercommunicated.
•They also contain alkaline phosphatase
26. Functions:
it is the bone maintaining cell (bone preserver).
1- Maintains bone matrix by formation of collagen fibers &glycoproteins.
2- Maintains the hardness of the matrix by continuous deposition of Ca salts
(continuous exchange between bone & blood).
4 - Osteoclasts (Bone Destroying Cells)
Origin:
formed by fusion of many Mood monocytes.
Sites:
at the bony surfaces undergoing resorption, in a shallow depression near the bone
marrow cavity produced by their erosive action called Howship's lacuna.
LM:
very large cell (up to 150 |um), with foamy acidophilic cytoplasm and multiple nuclei
(up to 50). The cell surface facing the bone is ruffled or striated(brush border).
EM:
• The surface facing the bone(ruffled border), consists ofprojecting from the cell
membrane to the bone surface (bone resorption occurs here)
•The cytoplasm contains many mitochondria, Golgi, ribosomes characteristic vesicles,
vacuoles & many lysosomes.
Functions:
bone eating cell. It is responsible for bone remodeling during growth or after
fractures. This function is produced by:
• Release of hydrogen ions (H+), which produce an acidic medium that dissolves Ca
salts —> decalcification.
• Their lysosomal enzymes (acid phosphatase, collagenase & proteolytic enzymes)
lead to absorption of minerals followed by lysis of organic matrix(bone resorption or
erosion )
27. C. Periosteum & Endosteum
All bones except at joint surfaces are covered both at the external and internal surfaces
with a layer formed of vascular C.T. and bone forming cells.
a) The Periosteum: It is the vascular non-calcified C.T. sheath covering the bone
outer surfaces. It consists of:
1- Outer fibrous layer: a layer of dense collagenous C.T., of collagen fibers&
fibroblasts. It is very rich in blood vessels, which will penetrate to the bone.
inside
2- Inner osteogenic (cellular) layer: it is more cellular, formed of closely arranged
osteogenic cells, which can divide and differentiate into osteoblasts, which are also
seen in this layer.
Functions of periosteum:
1- Nutrition (supplies bone with blood).
2- Muscle attachment.
3- Repair of fractures.
4- Appositional growth.
b) The Endosteum:
• It lines all internal surfaces and cavities within the bone (marrow cavities).
• It is formed of a single layer of osteogenic cells and osteoblasts with little amount of
loose C.T. It supplies osteogenic cells and osteoblasts for growth and repair of bone.
Histological Study of Bone
A- Compact Bone
It is highly organized hard C.T., dense and mature.
• It is present in the shafts of long bones, inner and outer table of flat bones and outer
covering of short irregular bones.
• It is the solid or ivoiy type of bone (mature bone), in which the bone is formed of
layers, called lamellae.
• A bone lamella is a thin plate of bone formed of calcified collagen bundles and
mineral salts deposited in ground substance around it.
•Between the lamellae are small spaces, or lacunae in which osteocytes are present.
•The shaft of long bone is organized into 4 lamellar structures, from outside inwards:
a- Outer circumferential lamellae,
b- Concentric lamellae (haversian system)
c- Interstitial lamellae,
d- Inner circumferential lamellae.
•Lamellae are arranged parallel to each other or concentrically regularly arranged
around blood vessels.
28. •They are organized in long bones into sets of concentric rings, called osteons or
Haversian systems.
• Each osteon includes a central channel, the Haversian canal, which contains
a blood vessel in its center. The long axis of the osteons is usually parallel to
the long axis of the bone
• N.B.: long bones are formed of a shaft called diaphysis, and two ends called
epiphysis. In between the diaphysis and epiphysis in growing bones, there is
a cartilage plate called epiphyseal plate.
• The histological structure can be studied in a transverse section in the shaft
of a long bone.
1. Decalcified Compact Bone
Transverse section in long bone, which is decalcified and stained with H & E, it
consists of:
Periosteum: covers the bone from outside, formed of 2 layers:
• Outer fibrous layer: acidophilic, formed of collagen fibers, fibroblasts, fibrocytes
and blood vessels.
• Inner cellular layer of osteogenic cells & osteoblasts.
External Circumferential lamellae: bone lamellae present under the periosteum, and
arranged in layers parallel to the circumference of the bone, enclosing osteocytes in
their lacunae in between them.
Haversian Systems (Osteons): the structural units of compact bone,
•They are cylindrical structures running parallel to the long axis of bone.
• Each is formed of concentrically arranged bone lamellae (5-20) layers, around a
vascular channel (Haversian canal) which contains blood vessels, nerves & loose
C.T. Osteocytes inside their lacunae are embedded between bone lamellae, lacunae
are connected together by canaliculi, through which they get their nutrition
29. Volkmann's canals: are the communicating transverse canals, linking the Haversian
canals in the Haversian system with one another and with the periosteum and bone
marrow cavity to get better nutrition.
Internal Circumferential lamellae: bone lamellae surrounding the bone marrow
cavity and parallel to the endosteum lining it.
Interstitial lamellae: present in between the Haversian systems. They consist of
irregularly arranged lamellae.
Endosteum: lines the central marrow cavity and consists of one layer of osteogenic
cells and osteoblasts with little amount of C.T.
Perforating fibers of Sharpey: They are calcified collagen fibers that arisefrom
tendons or ligaments at the site of muscle attachment. They perforate the periosteum
at an angle to be attached to the external circumferential lamellae and become
continuous with collagen fibers of the matrix. They fix the tendons into the bone.
30. 2- Ground Compact Bone
•Pieces of bone, from which all organic material
has been removed.
•Prepared by grinding a small chip of bone into
thin sections that transmit
light.
•This unstained section is characterized by:
- No living tissues can be
visualized(periosteum, endosteum & bone
cells).
- Bone lamellae appear whitish yellow in color.
- The lacunae of osteocytes, Haversian canals &
Volkmann's canals appear black, because they
contain air. Fine hair like canaliculi radiate from each lacuna to connect neighboring
lacunae with each other.
31. 3- Spongy (Cancellous) bone
•It is an irregular type of bone which doesn’t have a
lamellar structure. It is the first bone to form during fetal
life and during bone repair.
Sites:
present in the center of the epiphysis, flat & irregular
bones.
Structure:
• It is formed of branching and anastomosing irregular
bone trabeculae, which form a meshwork.
•Osteocytes in their lacunae are embedded in these
trabeculae. No Haversian systems.
• The trabeculae enclose multiple irregular marrow
cavities containing blood forming cells, fat cells and blood vessels. This arrangement
gives the sponge appearance .
32. Formation of Bone (Ossification)
Bone is formed from mesenchymal tissue in the embryo. There are two methods for
bone development or ossification:
1- Intramembranous ossification: in flat bones as skull, mandible, maxilla &
clavicle, which develop within a condensed mesenchymal membrane.
2- Intracartilagenous or endochondral ossification: as in long bones, which
develop by replacement of a pre-existing cartilage model.
N.B.: Primary bone is formed first, and is later replaced by secondary mature
bone.
1- Intramembranous Ossification
This type of ossification occurs in the flat bones as the diploe of the skull, clavicle,
ribs......etc.
1- The site of the future bone is occupied with a mesenchymal membrane.
2- The starting point for ossification is the appearance of a highly vascular area
in the middle of this membrane called the primary ossification center. The
mesenchymal cells (UMCs) condense, proliferate and differentiate into osteogenic
cells.
3- Osteogenic cells increase in size and number and differentiate to form osteoblasts.
4- Osteoblasts divide and synthesize organic matrix (osteoid) (collagen type I,
proteoglycans & glycoproteins), secrete it around themselves. They also secrete
alkaline phosphatase, which stimulates the deposition of Ca salts in the matrix around
them & their processes
5- When osteoblasts are trapped in their own matrix inside lacunae surrounded with
calcified matrix, they are called osteocytes.
6- Bone matrix extends in a radial manner in the form of trabeculae that radiate from
the starting point (primary ossification center).
7- Multiple ossification centers appear in the mesenchymal membrane and the
resulting bone trabeculae fuse together giving rise to spongy bone.
8- The vascular tissue that fills the spaces between trabeculae of spongy bones
differentiates into red bone marrow.
9- Growth and remodeling of bone result by continuous deposition of new bone
by osteoblasts & resorption by osteoclasts.
2- Intracartilagenous (Endochondral) Ossification
This type of bone formation occurs in long bones of limbs and takes place by
replacement of a cartilage model.
Development of cartilage model:
• In the embryo, a limb bud of mesoderm outgrows, condenses and takes the shape of
the future bone.
33. • The mesenchymal cells (in the avascular environment) differentiate into
chondroblasts which produce cartilage matrix, resulting in the development of a
model hyaline cartilage. Perichondrium, made up of outer fibrous and inner
chondrogenic layers, also develops at its periphery
• The cartilage model grows by appositional and interstitial methods.
Cartilage is replaced by bone: through the following steps:
A) Primary center of ossification: which starts to appear at the center of cartilage
model (diaphysis) where the following changes occur simultaneously:
1- The chondrocytes at the middle of the cartilage model proliferate, enlarge
(hypertrophy) & mature. Calcium salts start to be deposited in the matrix around their
lacunae, leading to their deprivation from nutrition. Chondrocytes then die leaving
empty lacunae, separated by calcified cartilage matrix, which is basophilic in H & E
stained sections
2- The perichondrium becomes more vascular & active, so mesenchymal cells
differentiate into osteoblasts, which start to lay down a thin collar of bone matrix in
the inner layer of the perichondrium (now it becomes periosteum).
3- Osteoclasts open holes in the bone collar allowing periosteal capillaries &
osteogenic cells and UMCs (vascular bud) to invade the cavities inside the model.
4- The osteogenic cells attach themselves to the remnants of the basophilic calcified
cartilage matrix and then change to osteoblasts, which start to lay bone matrix
(acidophilic) in an irregular manner (spongy bone).
5- Remodling: Osteoclasts start to resorb the irregular trabeculae in the center,
leading to the formation of a single marrow cavity in which mesenchymal cells gives
the bone marrow cells. At the same time, osteoblasts deposit new bone, to preserve
the general shape of bone during growth.
6- Zone of Ossification & Haversian system formation: Concentric bone lamellae,
produced by osteoblasts, are deposited around the blood vessels, to form Haversian
canals.
B) Secondary center of ossification: appears after birth in the two ends of the
developing bone (epiphyses), which are still cartilage, by increased vascularity
1- Chondrocytes in the center of the epiphysis proliferate, enlarge and mature
then deposit Ca salts in the matrix around them. This is followed by death of
chondrocytes leaving "empty spaces" in the middle of the epiphysis.
2- Capillaries & osteogenic cells invade the cartilage through holes produced
by osteoclasts.
3- Osteoblasts lay down bone matrix forming secondary ossific center.
Thus the cartilage at the middle of the two heads is replaced by spongy bone
except in two regions:
34. - Epiphyseal plated between epiphysis & diaphysis, which is left for growth till age
of 21-23 years.
- Articular cartilage: which will never ossify throughout life.
Postnatal growth of bone:
1- Growth in width (appositional growth): by continuous deposition of new
compact bone on the outer surface, under the periosteum, and continuous
bone resoiption of old bone from inside by osteoclasts, this leads to the
increase in the diameter of bone and also the marrow cavity increases in size.
35. 2- Growth in length (interstitial growth): Occurs in the epiphyseal plates,
where proliferation of cartilage takes place. At the age of 21-23 years, ossification is
complete and growth stops with no further proliferation of cartilage, and the
epiphyseal disc is completely ossified.
The Epiphyseal Plate (Growing End of Bone):
During growth of long bones, the epiphyseal plate has
a characteristic microscopic appearance(where
intracartilagenous ossification occurs). The study of a
longitudinal section of growing bone reveals distinct
histological zones, beginning with the epiphyseal side
of the plate (the stages of intracartilagenous
ossification) in the following zones:
1- Zone of resting cartilage: a reserve zone formed of hyaline cartilage, where
the cells are small, inactive and irregularly arranged.
2- Zone of proliferation: (increase in number), chondrocytes undergo repeated
mitosis, and arrange in parallel rows separated by bars of matrix.
3- Zone of maturation cell& hypertrophy: the chondrocytes are greatly enlarged,
and acquire high glycogen and alkaline phosphatase content. The cartilage matrix
between neighboring cells becomes thin.
4- Zone of calcification: mature chondrocytes secrete alkaline phosphatase,
which deposit Ca in the thin cartilage matrix. This will cut the nutrition from
chondrocytes.
- The trapped chondrocytes will die leaving their lacunae empty
-Lacunae will break and join leaving large empty spaces.
5- Zone of Invasion: a vascular bud (capillaries & osteogenic cells) invades the
empty spaces in the calcified matrix through holes produced by the action of
the osteoclasts.
6- Zone of ossification (spongy bone formation): the osteogenic cells change
into osteoblasts which lay down bone matrix on the calcified cartilage remnants. The
resulting bone trabeculae fuse forming spongy bone.
7- Remodeling: This is done by osteoclasts, which resorb bone trabeculae from
certain areas, while osteoblasts deposit new bone, to preserve a single marrow cavity
and general shape of bone during growth.
8- Zone of Ossification & Haversian system formation: Concentric bone lamellae,
produced by osteoblasts, are deposited from the outer to the inner aspect of a space in
the spongy bone containing blood vessels, until the cavities are reduced to be the
central canals (Haversian canals).
36. Fusion of the Epiphysis:
When the bone attains its full length, at about the age of 21-23 years, the chondrocytes
stop to proliferate.
•The process of calcification continues to extend into the cartilage, till the whole
epiphyseal plate is ossified and fuses with the diaphysis and the bone of the epiphysis
fuses with that of the diaphysis
Metaphvsis:
• It is the portion of the diaphysis adjoining the epiphyseal plate; it is the region of
active bone formation, so it is highly vascular.
• It does not have marrow cavity.
• Muscles and ligaments are usually attached to the bone in this region.
• It acts as a store for calcium and is the most active region for its turn over.
Bone Repair:
• Bone fracture leads to damage of bone matrix, and bone cells in the region as
well as blood vessels supplying the area;
• Hemorrhage is followed by the formation of blood clot. Macrophages remove the
damaged tissues.
• Fibroblasts proliferate in the periosteum and endosteum and surround the
area externally and internally, forming fibrous tissue between the two broken ends.
37. • Osteogenic cells, from the periosteum and blood capillaries migrate to the
area of the clot, starting deposition of bone. Also chondrogenic cells
differentiate, starting to lay cartilage matrix. This mass of tissue formed of
cartilage and bone at the site of the organized clot is called callus.
The Callus:
• It is the organized clot formed of cartilage, which will be replaced by bone, the
primary bone.
• Finally excess bone in the callus is resorbed and is replaced by secondary
bone and union of the two end of the fracture is complete.