Function of epithelial tissue
- cover external surface
- lines internal surfaces
- Glands are usually deprived from epithelium
Describe features of epithelial tissue
- large sheets of cells
- covers exterior surface and lines organs
Location of where epithelial tissue is found
- Lining of GI tract organs (glands)
- lines hollow organs
- skin surface (epidermis)
- airways
- digestive tract
- urinary and reproductive system
- blood vessels
- serous membranes
Epithelial characteristics
- highly cellular
- polarity
- supported by connective tissue
- avascular
- innervated
- regeneration
Polarity characteristics
- apical facing surface (external)
- basal surface (internal)
Apical surface
- contains organelles and extensions
- cilia
Basal surface
- contains organelles
What is the basement membrane?
- combination of basal and reticular lamina
- connects epithelial tissue with connective tissue
- provides structural and functional support
- reticular lamina is secreted by connective tissue
Avascular characteristic
- do not contain blood vessels
- materials that go through epithelial layer must go through diffusion or absorption
Innervated characteristic
- supplied by nervous tissue
- allow interactions w/ external environment
Regeneration characteristic
- quickly replaces damaged or dead cells
key function of epithelial tissue
- first line of protection
- its cells are gatekeepers that control permeability
- everything must cross epithelium
Epithelial cells
- secrete and release mucous and specific compounds on apical surface
- mucus can trap material
Endocrine glands
- ductless
- releases secretions directing into surrounding tissues and fluid
- “inside”
Exocrine glands
- secretions leave through a duct that opens to external environment
What are the secretions of endocrine glands? and what happens to them?
- hormones
- released into interstitial fluid, into bloodstream, and delivered to cells
examples of endocrine glands
- anterior pituitary
- thymus
- adrenal cortex
- gonads
Secretions of exocrine glands, what happens to them?
- mucus
- sweat
- saliva
- breast milk
- they are released onto external environment (Apical surface)
Simple epithelium and types
- single layer of cells
- simple squamous
- simple cuboidal
- simple columnar
- pseudostratified columnar
Simple Squamous Epithelium
- flat and horizontal
- found in lungs, kidneys, and capillaries
Special characteristic of simple squamous
- thin
- allows rapid passage
Simple Cuboidal Epithelium
- boxlife cells
- nucleus located near center of cell
- in kidneys and gland ducts
Special characteristic of simple cuboidal
- secretion and absorption of molecules
Simple Columnar Epithelium
- tall, rectangular
- nucleus located in basal end of cells
- in digestive system and female reproductive tract
