Fibrous Joint StructureThese types of joints are held together byfibrous connective tissue, no joint cavity ispresent. Either slightly mobile or immobile.
Synovial Joint StructureMade up of synovial fluid, freely movable andcharacterize most joints.Subtypes-Hyaline Cartilage- Covers the end of the boneSynovial Membrane- Surrounds synovial cavity.Fibrous capsule- Made up of ligaments ( dense,irregular connective tissue)Articulate capsule- Both synovial and fibrousmembrane.
Types of MovementSYNOVIAL JOINTS- All are freely movable(diarthrosis)Gliding- Two sliding surfacesHinge- Concave surface with convex surface,diathrosisPivot- Rounded end fits into ringCondyloid- oval condyle with oval cavitySaddle- each surface is concave or convexBall&Socket- Ball shaped head, and cupshaped pocket
The Four Types of Bones● Long Bones● Short Bones● Flat Bones● Irregular Bones
Long BonesThese bones typically have an elongated shaft and twoexpanded ends one on either side of the shaft. The shaft isknown as diaphysis and the ends are called epiphyses.Normally the epiphyses are smooth and articular. The shafthas a central medullary cavity where lies the bone marrow.Examples include the humerus, femur, radius, ulna, tibiaand fibula
Short BonesThese bones are short in posture and canbe of any shape. Most of them are namedaccording to their shape.Examples of this class of bones includecuboid, cuneiform, scaphoid, trapezoidetc. In fact all the carpal and tarsal bonesare included in this category.
Flat BonesThese bones are flat in appearance andhave two prominent surfaces. Theyresemble shallow plates and formboundaries of certain body cavities.Examples include scapula, ribs, sternumetc.
Irregular BonesThe shape of these bones is completelyirregular and they do not fit into anycategory of shape.Examples of this type of bones arevertebrae, hip bone and bones in thebase of skull.
Major Structures of a LongBone● The diaphysis, or shaft, is the long tubular portion of long bones. It is composed of compact bone tissue.● The epiphysis (plural, epiphyses) is the expanded end of a long bone. It is in the epiphyses where red blood cells are formed.● The metaphysis is the area where the diaphysis meets the epiphysis. It includes the epiphyseal line, a remnant of cartilage from growing bones.● The medullary cavity, or marrow cavity, is the open area within the diaphysis. The adipose tissue inside the cavity stores lipids and forms the yellow marrow.● Articular cartilage covers the epiphysis where joints occur.● The periosteum is the membrane covering the outside of the diaphysis (and epiphyses where articular cartilage is absent). It contains osteoblasts (bone-forming cells), osteoclasts (bone-destroying cells), nerve fibers, and blood and lymphatic vessels. Ligaments and tendons attach to the periosteum.● The endosteum is the membrane that lines the marrow cavity.
Bone as a TissueThere are two different kinds of bone tissue: Compact and Spongy bone.Compact bone ● Is made up of concentric rings of matrix that surround central canals which contain blood vessels. ● Embedded in this bone tissue are small cave-like spaces called lacunae, which are connected to each other through small tunnels called canaliculi. ● The lacunae contain osteocytes cells. As just discussed, osteocytes help maintain healthy bone tissue and are involved in the bone remodeling process that will be outlined later in this lesson.Spongy bone ● Looks like an irregular latticework (or sponge) with lots of spaces throughout. ● These spaces are filled with red bone marrow which is the site of hematopoiesis or formation of blood cells.
The Haversian SystemA Haversian System consists of many cylinder-shapedstructural units. There are four types of structures that make upeach Haversian system. (1)1. Lamellae – concentric, cylinder-shaped layers of calcifiedmatrix2. Lacunae – small spaces containing tissue fluid in whichbone cells lie imprisoned between the hard layers of the lamellae3. Canaliculi – ultrasmall canals radiating in all directionsfrom the lacunae and connecting them to each other and into alarger canal, the haversian canal4. Haversian canal – extends lengthwise through the centerof each Haversian system; contains blood vessels, lymphaticvessels, and nerves from the Haversian canal; nutrients andoxygen move through canaliculi to the lacunae and their bone
Three Major Types of CellsFound in Bones1. Osteoblasts – bone-formingcells2. Osteoclasts – bone-resorbing cells3. Osteocytes – mature bonecells
OsteoblastsOsteoblasts are small cells thatsynthesize and secrete a specializedorganic matrix, called osteoid. (1)
OsteoclastsOsteoclasts are giant multinucleatecells that are responsible for the activeerosion of bone minerals. (1)
OsteocytesOsteocytes are mature, non-dividingosteoblasts that have becomesurrounded by matrix and now lie withinlacunae. (1)
Homeostatic Functions ofBones1. Support: contributes to the shape, alignment, andpositioning of the body parts2. Protection: hard, bony “boxes” that serve to protect thedelicate structures they enclose3. Movement: bones with their joints constitute levers,muscles are anchored firmly to bones, as muscles contractand shorten, they pull on bones. Making it movement in a joint4. Mineral storage: depends on changes in the rate ofcalcium movement between the blood and bones5. Hematopoiesis: blood cell formation(1)
Intramembranous andEndochondral BoneIntramembranous and Endochondral bone are two essential processes duringfetal development of the mammalian skeletal system by which bone tissue iscreatedIntramembranous: · Cartilage is not present during intramembranous ossification · Intramembranous ossification is essential process during the natural healing of bone fractures and the rudimentary formation of bones of the headEndochondral: · Cartilage is present during endochondral ossification · Essential process during the rudimentary formation of long bones, the growth of the length of long bones, and the natural healing of bone fractures.
Bone Fracture Repair1. White blood cells move in to the area to clean up debris created by the break, which creates inflammation, in turn triggering the growth of new blood cells2. New blood vessels develop to begin the healing process3. Soft callus also known as cartilage or soft fibrous tissue, begins to form to bridge the gap from the break.4. A harder cartilage develops in place of the soft cartilage, forming a more solid bond within the gap5. Through a process called remodeling, old bone is continually replaced by new bone, completing the process of bone fracture healing.
Bone and CartilageA bone is a rigid organ that constitutes part of theendoskeleton of vertebrates. It supports and protects thevarious organs of the body, produces red and white bloodcells and stores minerals. Bone is made up of osteoblasts,osteocytes, osteoclasts, and bone lining cells whichregulate the movement of calcium· Cartilage is a flexible connective tissue found in manyareas in the bodies of humans and other animals, includingthe joints between bones. Cartilage is made up ofchondroblasts, chondrocytes, and dense matrix made up ofcollagen and elastic fibers
Types of Cartilage1. Elastic2. Hyaline3. Fibrocartilage
Elastic CartilageElastic cartilage or yellow cartilage is a type of cartilagepresent in the outer ear and epiglottis. It contains elasticfiber networks and collagen fibers. The principal protein iselastin.Elastic cartilage is histologically similar to hyaline cartilagebut contains many yellow elastic fibers lying in a solidmatrix. These fibers form bundles that appear dark under amicroscope. These fibers give elastic cartilage greatflexibility so that it is able to withstand repeated bending.The chondrocytes lie between the fibers. It is found in theepiglottis (part of the larynx) and the pinnae (the externalear flaps of many mammals including humans). Elastinfibers stain dark purple/black with Verhoeff stain.
Hyaline Cartilage: Hyaline cartilage is a type of cartilage found on many joint surfaces. It is pearlybluish in color with firm consistency and considerable collagen. It contains nonerves or blood vessels, and its structure is relatively simple.Hyaline cartilage is covered externally by a fibrous membrane, called theperichondrium, except at the articular ends of bones and also where it is founddirectly under the skin. This membrane contains vessels that provide thecartilage with nutrition.If a thin slice is examined under the microscope, it will be found to consist ofcells of a rounded or bluntly angular form, lying in groups of two or more in agranular or almost homogeneous matrix.The cells, when arranged in groups of two or more, have generally straightoutlines where they are in contact with each other, and in the rest of theircircumference are rounded.They consist of clear translucent protoplasm in which fine interlacing filamentsand minute granules are sometimes present; embedded in this are one or tworound nuclei, having the usual intranuclear network.
FibrocartilageWhite fibrocartilage consists of a mixture of white fibroustissue and cartilaginous tissue in various proportions. Itowes its flexibility and toughness to the former of theseconstituents, and its elasticity to the latter. It is the only typeof cartilage that contains type I collagen in addition to thenormal type II.Fibrocartilage is found in the pubic symphysis, the annulusfibrosis of intervertebral discs, menisci, and the TMJ.During labor, relaxin loosens the pubic to aid in delivery,but this can lead to later joint problems.
Bone GrowthTo make a bone longer just add bone tissue to the ends. The problem is, wecant add directly to the end of a bone, it has to move at the joints. If tissue isadded at the end of the bone the skeleton could not move properly. Its likeclosing both lanes on an interstate until the bridge is repaired.For this to work, bone tissue must be added below the joint somewhere alongthe length of the bone. This occurs at the epiphyseal plate, or growth plate.Here chondrocytes first produce hyaline cartilage. The cartilage thenbecomes calcified or ossified to form hard bone tissue (involves addition of Ca+and Phosphorous ions). The chondrocytes produce cartilage on one side of theplate and push the end of the bone up. The other side of the epiphyseal plategradually becomes calcified.Once a person reached adulthood and the bones have reached maximumlength, and the whole plate gets calcified. It forms a visible line called theepiphyseal line.
Cartilage GrowthIn embryogenesis, the skeletal system is derived from themesoderm germ layer. Chondrification (also known aschondrogenesis) is the process by which cartilage isformed from condensed mesenchyme tissue, whichdifferentiates into chondroblasts and begins secreting themolecules that form the extracellular matrix.Following the initial chondrification that occurs duringembryogenesis, cartilage growth consists mostly of thematuring of immature cartilage to a more mature state.