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The Intricacies of Epithelial Tissues: Function, Structure & Classification

Understand the essential functions, characteristics, and classifications of epithelial tissues in the human body. Explore different types, shapes, and arrangements of epithelial cells and their roles in maintaining bodily functions. Discover glandular epithelium and its secretions.

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The Intricacies of Epithelial Tissues: Function, Structure & Classification

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  1. TISSUES • Tissues - cells working together to perform a common function • Histology - Study of tissues

  2. 4 BASIC TYPES • Epithelial - covers & lines surfaces, forms glands • Connective - connects tissues, provides support, stores energy reserves • Muscle - Contracts for movement, generates heat • Neural - Carries information from one part of body to another in the form of electrical impulses

  3. Epithelial Tissue - layer of cells that forms a barrier • Functions: • provides physical protection • controls permeability • provides sensations • produces secretions • Characteristics: • consists mainly of cells • consists of single layer or multiple layers • always has a free surface exposed to the environment • avascular • mitotic rate can be very high

  4. Intercellular Connections • Tight Junction - formed by fusion of cell membranes • Desmosome - thin proteoglycan layer between opposing cell membranes • Gap Junction - binding of membrane proteins

  5. Shapes: Squamous - flat Cuboidal - cubed Columnar - higher than wide Arrangements: Simple - single layer of same shape Stratified - many layers of same shape Transitional - several layers of differing shapes CLASSIFICATIONSubdivided according to shape & arrangement of cells in each type http://trc.ucdavis.edu/biosci10v/bis10v/media/ch20/epithelial_structure.html

  6. Bell work QuestionsAug 20th • What are the four types of tissues? • Define tissue. • The study of tissues is call ______________. • How are Epithelial tissues named? • What are the 3 basic shapes of epithelial tissues? • What are the 3 basic arrangements of epithelial tissues

  7. SIMPLE SQUAMOUS(most delicate) • Locations • Alveoli in lungs • blood & lymphatic vessels • Functions • Reduce friction • Diffusion of gases • Controls permeability

  8. STRATIFIED SQUAMOUS(tough) • Locations • Surface of skin • Lining of mouth, throat, esophagus, rectum, vagina • Functions • Protection against abrasion, pathogens, and chemicals

  9. SIMPLE CUBOIDAL • Locations - • glands, ducts, kidney tubules, thyroid gland • Functions - • protection, secretion, and/or absorption

  10. STRATIFIED CUBOIDAL(RARE) • Locations - • lining of some ducts like sweat glands • Mammary glands • Functions - • Protection, secretion, absorption

  11. TRANSITIONAL EPITHELIUM(STRETCHY) • Locations - • Urinary bladder, ureters • Functions - • Permits expansion & recoil after stretching

  12. SIMPLE COLUMNAR • Locations- • Lining of stomach, intestine, gallbladder, uterine tubes, collecting ducts of kidneys • Functions - • Protection, secretion, absorption

  13. PSEUDOSTRATIFIED COLUMNAR EPITHELIUM • Locations - • lining of nasal cavity, bronchi, trachea • Functions - • protection, secretion • Nuclei are located at varying distances from surface

  14. STRATIFIED COLUMNARRelatively Rare • Locations - • pharynx, epiglottis, anus, mammary ducts, urethra • Functions - • Protection

  15. Bell work

  16. Glandular epithelium • Cells that make up glands are specialized to produce and secrete substances • Types of secretions from cells • 1. endocrine • Glands that secrete their products into tissues or blood • Ex: Pituitary and sex glands • 2. exocrine • Merocrine: release products by exocytosis Ex: salivary glands/ pancreas • Apocrine: Lose small portions of glandular bodies during secretion ex: mammary glands: fat droplets/sweat glands • Holocrine: entire cell disintegrates Ex: sebaceous glands of skin (fatty mixture called sebum)

  17. Reflection • How are epithelial tissues classified? • How can you i.d. if a tissue is an epithelial?

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