Epithelial Tissue Anatomy

What are tissues? Groups of cells that are similar in structure and perform a common function Histology: the study of tissues

Epithelial Tissue Covers body surface Lines a body cavity Forms boundaries between different environments Skin: lies between inside/outside of body Epithelium in bladder: separates bladder and urine

Epithelial Forms outer layer of skin Lines open cavities of cardiovascular, digestive and respiratory systems

Characteristics of Epithelium Cellularity: closed packed cells (little to no extracellular material) Specialized contacts: continuous sheets

Characteristics of Epithelium Polarity: apical surface (surface exposed to body exterior/cavity) basal surface/lamina (opposite the apical, supporting)

Characteristics of Epithelium Supported by connective tissue: Reticular lamina (contains collagen fibers) Basement membrane: reticular lamina with the basal lamina, reinforces, resists stretching/tearing/defines boundary

Characteristics of Epithelium Avascular but innervated Has nerve fibers but does not contain blood vessels Nourished by substances diffusing into layer from lower layers

Characteristics of Epithelium Regeneration High regeneration capacity

Classification of Epithelia Simple Stratified Squamous Cubodial Columnar

Simple squamous epitheial Single layer of flattened cells Disc shape central nuclei Allows passage of materials (diffusion/filtration), secretes serosa Kidney glomeruli, air sacs of lungs, linging of heart, blood vessels, lymphatic vessels

Simple cubodial epithelium Single layer of cube like cells with large central nuclei Secretion/absorption Kidney tubules, ducts of glands, ovary surface

Simple columnar epithelial Single layer of tall cells with oval nuclei, cilia, contrain mucus secreting cells (goblet cells) Absorption, secretion, propel secretion (mucus, enzymes) Digestive tract, gallbadder, uterus

Stratified squamous epithelium Thick, basal cells are cubodial/columnar, surface cells are flat, surface cells full of keratin (dead) Protection Mouth, esophagus, skin, dry membranes

http://classes. midlandstech. edu/carterp/Courses/bio210/chap04/chap04 http://classes.midlandstech.edu/carterp/Courses/bio210/chap04/chap04.html