What is the definition of epithelia?
Sheets of contiguous cells of varied embryonic origin that cover the external surface of the body and line internal surfaces
Which exterior surface is lined with epithelia?
Skin
Which interior surfaces that open to the exterior are lined with epithelia?
- GI Tract
- Respiratory tract
- Genitourinary tract
Which interior surfaces that do not open to the exterior are lined with epithelia?
- Pericardial sac
- Pleural sac
- Peritoneum
- Blood vessels
- Lymphatic vessels
What is the function of simple squamous epithelia?
- Lubrication
- Gas exchange
- Barrier
- Active transport via pinocytosis
Where is simple squamous epithelia found?
- Endothelium
- lining of body cavities (pleura, pericardium, peritoneum; all lined with mesothelium)
- Alveoli
- Bowman’s capsule
- Loop of Henle (kidney)
- Inner and middle ear
What is the function of simple columnar epithelia?
- Absorption
- Secretion
- Lubrication
- Transport
Can have cilia
Where is simple columnar epithelia found?
- Stomach lining and gastric pits
- Small intestine and colon
- Gall bladder
- Large ducts of some exocrine glands
- Uterus
- Oviducts
- Ductuli efferents of testis
Where is pseudostratified epithelia found?
- Lining of nasal cavity, trachea and bronchi
- Epididymis
- Lacrimal sac
- Large excretory ducts
- Auditory tube
What are the functions of pseudostratified epithelia?
- Secretion and conduit
- Absorption
- Mucus secretion
- Particle trapping and removal
What are the functions of simple cuboidal epithelia and where is it found?
- Absorption and conduit (exocrine glands)
- Absorption and secretion (kidney tubules)
- Barrier (Ovary)
- Hormone synthesis and storage (thyroid follicles)
Where is stratified keratinised squamous epithelia found?
- Surface of skin
- limited distribution in oral cavity
What is the function of stratified keratinised squamous epithelia?
- Protection against abrasion and trauma
- Prevention of water loss
- Protects against ingress of microbes
What is the function of stratified squamous non-keratinised epithelia?
- protection against abrasion
- reducing water loss whilst remaining moist
Where is stratified squamous non-keratinised epithelia found?
- oral cavity
- oesaphagus
- larynx
- vagina
- part of anal canal
- surface of cornea
- inner eyelid
Where is stratified transitional epithelia found?
- Uterus
- Urethra
- Bladder
- Renal calyces
What is the function of transitional epithelia?
- Distensibility
- Protection from toxic chemicals
What are stereocili and where are they found?
- Very long cilia found in ductus deferens and epididymis
- absorptive
What is basement membrane?
-Thin, flexible, acellular layer (basal lamina), between epithelia and subtending connective tissue that epithelial cells adhere to
How is the is the thickness of the basal lamina determined?
Determined by thickness of reticular fibrils (Type 3 collagen)
How are renewal rates of epithelia determined?
Depends on function and location, constant renewal rate. Some epithelial cells aren’t renewed but proliferation triggered by damage or loss of cells
