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EPITHELIAL TISSUES IN NURSING SCIENCE AG
- 1. EPITHELIAL TISSUES • Studyof tissues •Tissues are collections of similar cells and the extracellular matrix surrounding them •The four primary tissue types are 1. Epithelial tissue 2. Connective tissue 3. Muscle tissue 4. Nervous tissue
- 2. Embryonic Tissue • Primarytissue types are derived from the embryonic germ layers – Endoderm • Forms the lining of the digestive tract and its derivatives – Mesoderm • Forms tissues such as muscle, bone, and blood vessels – Ectoderm • Forms the outermost layer of skin and the nervous system • Gives rise to all tissues of the body
- 3. Epithelial Tissue • Epithelialtissue – Covers surfaces – Has little extracellular material – Usually has a basement membrane – Has no blood vessels • Epithelial cells – Have a free, or apical, surface (not attached to other cells) – A lateral surface (attached to other cells) – A basal surface (attached to the basement membrane)
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- 5. Epithelial Tissue Functions 1.Protecting underlying structures – Example: outer layer of skin and oral mucosa 2. Acting as barriers – Example: outer layer of skin 3. Permitting the passage of substances – Example: epithelium in the lungs 4. Secreting substances – Example: mucous glands and sweat glands 5. Absorbing substances – Example: epithelial cells of the intestine
- 6. Epithelial Tissue Classification •Epithelia are classified according to the number of cell layers and the shape of the cells – Cell layers • Simple epithelium has one layer of cells • Stratified epithelium has more than one cell layer • Pseudostratified epithelium has one layer, but appears to have two or more layers • Transitional epithelium is stratified epithelium that can be greatly stretched – Cell shape • Squamous are flat and thin • Cuboidal are cubelike • Columnar are tall and thin
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- 15. Epithelial Tissue Structural andFunctional Relationships • Cell Layers and Cell Shapes – Simple epithelium is involved with • Diffusion • Secretion • Absorption – Stratified epithelium serves a protective role – Squamous cells function in • Diffusion • Filtration – Cuboidal or columnar cells, which contain cellular organelles • Secrete • Absorb
- 16. • Structural andFunctional Relationships – Free Cell Surfaces • A smooth, free surface reduces friction – Example: Lining of blood vessels • Microvilli are cylindrical extensions of the cell membrane that increase surface area (cells involved in absorption of secretion) – Example: Lining of the small intestines • Cilia propel materials over the cell surface – Example: Lining of the nasal cavity and trachea Epithelial Tissue Structural and Functional Relationships
- 17. •Cell connections – Tightjunctions bind adjacent cells together and form a permeability barrier – Desmosomes mechanically bind cells together – Hemidesmosomes mechanically bind cells to the basement membrane – Gap junctions allow intercellular communication Fig. 4.2 Epithelial Tissue Structural and Functional Relationships
- 18. Epithelial Tissue Glands •A gland is a single cell or a multicellular structure that secretes – Endocrine glands do not have ducts • Secrete hormones directly into the blood – Exocrine glands have ducts • Secretions are released onto a surface or into a cavity – Sweat glands and mammary glands • Classified by – Structure – How products leave the cell
- 19. Epithelial Tissue Glands Fig.4.3 • Structure of Exocrine Glands – Simple: have one duct – Compound: have ducts that branch repeatedly – Tubules: ducts end in small tubes – Acini: ducts end in saclike structures – Alveoli: ducts end in hollow sacs
- 20. Epithelial Tissue Glands Fig.4.4 • Exocrine Glands and Secretion Types – Merocrine – no loss of cellular material (Ex. sweat glands) – Apocrine – part of the cell pinches off (Ex. mammary glands) – Holocrine – entire cell is shed (Ex. sebaceous glands)
- 21. Connective Tissue • Consistof cells seperated from each other by abundant extracellular matrix • Functions 1. Enclosing and separating 2. Connecting tissues to one another (Ex. Ligaments and Tendons) 3. Supporting and moving (Ex. Bones and cartilage) 4. Storing (Ex. Adipose tissue and Bones) 5. Cushioning and insulating (Ex. Adipose tissue) 6. Transporting (Ex. Blood) 7. Protecting (Ex. Blood and Bones)
- 22. Connective Tissue Cells •Specialized cells of various connective tissues produce the extra cellular matrix – End in suffixes that identify the cell functions • Blast (germ) cells form the matrix • Cyte (cell) cells maintain it • Clast (break) cells break it down
- 23. Connective Tissue • Extracellularmatrix contains – Protein fibers • Collagen fibers are flexible but resist stretching • Reticular fibers form a fiber network • Elastic fibers recoil – Ground substance • Proteoglycans in ground substance hold water, enabling connective tissues to return to their original shape after being compressed – Fluid
- 24. Connective Tissue Classification •Mesenchyme: – embryonic connective tissue that gives rise to six major categories of connective tissue
- 25. Connective Tissue Classification •Loose, or areolar, connective tissue is the “loose packing” material of the body – Fills the spaces between organs – Holds organs in place • Adipose tissue (fat) – Stores energy – Pads and protects parts of the body – Acts as a thermal insulator • Dense connective tissue consists of a matrix containing densely packed fibers – Collagen fibers (Ex. tendons, ligaments, and dermis of the skin) – Elastic fibers (Ex. elastic ligaments and in the walls of arteries)
- 26. Connective Tissue Classification •Cartilage provides support – Hyaline cartilage (Ex. covers ends of bones and forms costal cartilages) – Fibrocartilage (Ex. disks between vertebrae) – Elastic cartilage (Ex. external ear) • Bone has a mineralized matrix – forms most of the skeleton of the body • Compact bone has more matrix than spaces • Cancellous bone has more spaces then matrix • Blood has a liquid matrix – Found in blood vessels – Produced in hemopoietic tissue (red bone marrow)
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- 39. Muscle Tissue • Specializedto contract, or shorten, making movement possible – Length of muscle cells is greater than the diameter – Sometimes called muscle fibers because they often resemble tiny threads • Three types of muscle tissue – Skeletal • Meat of animals • Constitutes ~40% of a person’s body weight • Attaches to the skeleton and allows for movement • Voluntary, multinucleated, and striated (banded) – Cardiac • Muscle of the heart • Connected to one another by intercalated disks (contain gap junctions) • Involuntary, striated, and usually have one nucleus per cell – Smooth • Forms the walls of hollow organs (except the heart) and also is found in the skin and the eyes • Involuntary, not striated, and have a single nucleus
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- 43. Nervous Tissue • Nervoustissue is specialized to conduct action potentials (electrical signals) • Neurons conduct action potentials • Neuroglia support the neurons
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- 45. Membranes • Mucous membranesline cavities that open to the outside of the body – Digestive, respiratory, urinary, and reproductive tracts – Contain glands – Secrete mucus • Serous membranes line trunk cavities that do not open to the outside of the body – pleural, pericardial, and peritoneal cavities – Do Not contain glands – Secrete serous fluid • Synovial membranes line freely movable joints
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