TISSUES—NOTHING TO SNEEZE AT! EPITHELIUM

TISSUE Group of cells with a specialized structural and functional role Group of cells with a specialized structural and functional role

I.Epithelial Tissue 1. Cellularity- closely packed cells, very little extracellular space 2. Specialized contacts- fit close together to form continuous sheets 3. Polarity- all epithelial cells have a ‘apical surface’ and an attached basal surface.

More properties… 4. Supported by Connective Tissue 5. Avascular 6. Inervated 7. Regeneration- High capacity for making copies of themselves

General functions: Epithelial cells provide: Epithelial cells provide: A. protection A. protection B. absorption B. absorption C. filtration C. filtration D. excretion D. excretion E. secretion E. secretion F. sensory reception F. sensory reception

SIMPLE SQUAMOUS EPITHELIUM Single layer of thin, flattened cells Single layer of thin, flattened cells Broad thin nucleus (disc shaped) Broad thin nucleus (disc shaped) Fxn: allows passage of materials by diffusion and filtration where protection is not important Fxn: allows passage of materials by diffusion and filtration where protection is not important Examples: air sacs (alveoli) Examples: air sacs (alveoli) Capillary walls, lining the heart, lining of ventral body cavity, kidney glomeruli Capillary walls, lining the heart, lining of ventral body cavity, kidney glomeruli

Special Simple Squamous Endothelium: Simple squamous that lines the inside of the heart, blood vessels and lymphatic vessels. Slick, reduces friction. Endothelium: Simple squamous that lines the inside of the heart, blood vessels and lymphatic vessels. Slick, reduces friction. In fact capillaries are just a tiny tube of simple squamous. In fact capillaries are just a tiny tube of simple squamous. Mesothelium: Helps form serous membranes. The membranes that line the body cavities and organs in the ventral body cavity. Mesothelium: Helps form serous membranes. The membranes that line the body cavities and organs in the ventral body cavity. You remember body cavities from Unit 1! You remember body cavities from Unit 1!

Simple Cuboidal Epithelium Single layer of cube shaped cells Single layer of cube shaped cells Centrally located, spherical nucleus Centrally located, spherical nucleus FXN: Secretion and absorption FXN: Secretion and absorption Ex: ovaries, kidney tubules, salivary glands, thyroid, pancreas, liver Ex: ovaries, kidney tubules, salivary glands, thyroid, pancreas, liver

Simple Columnar Epithelium Elongated (longer than they are wide) Elongated (longer than they are wide) Nuclei located near/on basement membrane Nuclei located near/on basement membrane (often you will find microvilli on surface) (often you will find microvilli on surface) (also find goblet cells) (also find goblet cells)

Simple Columnar Found: Lining most of Digestive tract (non-ciliated type), gallbladder, excretory ducts of some glands; small bronchi, uterine tubes, regions of uterus Found: Lining most of Digestive tract (non-ciliated type), gallbladder, excretory ducts of some glands; small bronchi, uterine tubes, regions of uterus Function: Absorption, secretion of mucous, enzymes and other substances Function: Absorption, secretion of mucous, enzymes and other substances

Bleeping Awesome, Goblet Cell Excreting Mucus

Simple Columnar

Stratified Squamous Epithelium Multiple layer of squamous cells Multiple layer of squamous cells 1. Keratinized  outer layer of epidermis 1. Keratinized  outer layer of epidermis Cells on free surface are dead! Cells on free surface are dead! 2. Non-keratinized 2. Non-keratinized Ex: mouth, throat, anus Ex: mouth, throat, anus (cells on free surface remain alive) (cells on free surface remain alive)

Stratified cuboidal Epithelium 2-3 layers of cuboidal cells (form lining of lumen) 2-3 layers of cuboidal cells (form lining of lumen) -protection -protection -sweat glands, mammary glands, salivary glands, glands of pancreas -sweat glands, mammary glands, salivary glands, glands of pancreas

Stratified Columnar RARE!!! RARE!!! Several layers of elongated cells Several layers of elongated cells Ex: Male urethra, Vas deferens, parts of pharynx Ex: Male urethra, Vas deferens, parts of pharynx

Pseudostratified Columnar Appears to be stratified or layered. (BUT THEY ARE NOT)!! Appears to be stratified or layered. (BUT THEY ARE NOT)!! Cell nuclei are actually at different levels in the row. Cell nuclei are actually at different levels in the row. Ex: Respiratory system Ex: Respiratory system

Transitional Epithelium Specialized epithelium designed to change in response to increased tension. Specialized epithelium designed to change in response to increased tension. Ex: Bladder, ureters, parts of urethra Ex: Bladder, ureters, parts of urethra

Transitional