Introduction to Epithelial tissue, Exercises of Anatomy

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Body tissues

Tissues

• Groups of cells closely associated that have a

similar structure and perform a related

function

• Four types of tissue
  • Epithelial = covering
  • Connective = support
  • Muscle = movement
  • Nervous = control
• Most organs contain all 4 types

Epithelial tissues

4)They are derived from all three germ layers embryologically

Ectoderm – epidermis of skin Mesoderm – Lining of urinary & genital tracts Endoderm – Lining of alimentary & respiratory tracts

5)They have marked ability to regenerate when injured.

6)They are avascular but gets nutrition by diffusion from underlying blood vessels.

7)They get nerve supply from the nerve fibres which penetrate the intervals between these cells

Epithelial tissues

• Functions:
  1. Selective barrier
  2. Covering & protection - skin
  3. Absorption – intestinal villi
  4. Secretion – glandular epithelium
  5. Sensory receptors – neuroepithelium
  6. Contraction – myoepithelial cells
  7. Lubrication – peritoneal, pleural, pericardial cavities
  8. Prevention of reabsorption – transitional epithelium

Simple Epithelia

Type Cell shape Example Squamous Squashed Endothelium (lines blood vessels), mesothelium (serous lining of celom) Cuboidal Cubed Walls of glands

Columnar Columns Lining of gut tube; sometimes with cilia like lining of uterine tube Pseudo-stratified Flat cells give rise to columns

With cilia in respiratory tubes to move mucous/particles out of lungs

Stratified epithelia

Stratified Squamous Epithelium: •Cells in many layers – basal cells are columnar, intermediate cells are polyhedral, surface cells are flattened. The surface cells may be nucleated & living (moist/non-keratinized) or non-nucleated & dead (dry/keratinized). •Examples: Nonkeratinized – lining of mouth, oesophagus, vagina, anal canal Keratinized – epidermis of skin •Function: Protection, water proofing

Stratified epithelium

Stratified Cuboidal Epithelium: Examples: Sweat glands, developing ovarian follicle

Stratified Columnar Epithelium: Examples: Conjunctiva, ducts of large glands

Transitional Epithelium: •Cell consists of 2-6 layers. The basal cells are cubical, middle cells are pear shaped, surface cells are umbrella shaped but becomes flattened when distended. •Examples: renal calyces, ureter, urinary bladder, proximal part of urethra, etc •Function: prevention of reabsorption, distensibity of mucosa.

• Mesothelium ×
• Simple cuboidal ×
• Simple columnar ×
• Pseudostratified ×
• Goblet cell ×
• Stratified squamous ×
• Transitional ×

Features of Apical Surface of

Epithelium

 Microvilli: in small intestine

 Finger-like extensions of the plasma membrane of apical epithelial cell  Increase surface area for absorption

 Cilia: respiratory tubes

 Whip-like, motile extensions  Moves mucus, etc. over epithelial surface one-way

 Flagella: spermatozoa

 Extra long cilia  Moves cell

Name that Epithelial Feature!

(name and location on cell)

• Cilia
• Tight junction
• Microvilli
• Basement membrane

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