Lecture 2 - Epithelium Flashcards
Epithelia are avascular i.e. lack a direct blood and lymphatic supply .Nutrients are delivered by ______
Diffusion
Domain of epithelium
has structures important for protection and absorption microvilli , Cilia and stereo cilia
Apical Domain
Domain of epithelium
have structures needed to anchor epithelial cells to each other e.g. Occluding Junctions, Desmosomes and Cell – Cell attachment.
Lateral Domain
Domain of epithelium
have structures needed to anchor cells to basement membrane e.g. cell to extracellular matrix junctions and basal cell membrane infoldings
Basal Domain
- increase the surface area for absorption / secretion and are found in cells lining stomach and intestines.
- In the small intestines , they are densely packed and have a uniform height –brush border or striated border .
Microvili
-transport matter along the cell surface and are found on columnar cells lining the oviduct , bronchi.
They are long , highly motile apical structures
Cilia
-chronic respiratory infections ( lack of cleansing action of cilia , infertility ( immotile spermatozoa)
Kartagener,s syndrome
________are specialized proteins in the plasma membranes of adjacent cells.
They “stitch together” adjacent cells to form a tight cellular connection.
They are designed to restrict movement of material between the cells they link.
Tight junctions
________ are specialized connection protein complexes in cells that “rivet” cells together. They are attached to the intermediate fibers of adjacent cells.
The anchoring proteins can also be used to communicate between cells
Desmosomes
_______are holes lined with specialized proteins that create cytoplasmic communication bridges between cells allowing for chemical and electrical signals to be passed rapidly.
Gap junctions
Many agents such as cytomegalovirus and cholera toxin cause junctional complexes to become permeable.
__________ disrupt zonula occludens of stomach epithelial cells
Helicobacter pylori
Locations of simple squamous epithelium
Functions of simple squamous epithelium
- Blood vessels ( endothelium)
- Body cavities ( mesothelium)
- Bowman’s capsule of the kidneys
- Alveoli of lungs
- Fluid transport ( e.g. kidney)
- Gas Exchange ( lung alveolus)
- Lubrication ( e.g. mesothelium)
Locations of simple cuboidal epithelium
Functions of simple cuboidal epithelium
- small ducts of exocrine glands
- Most of the kidney tubules.
- Thyroid Follicles
- Protection
- Absorption
- Secretion
- Conduit
Locations of simple columnar epithelium
Functions of simple columnar epithelium
lining the stomach , intestines , gall bladder uterus , oviducts .
- protection , secretion, absorption and transport .
- Simple columnar epithelial cells have specialized projections on apical surface , namely microvilli or cilia.
Type of Stratified squamos epithelium
found lining moist cavities e.g. oral cavity , esophagus , vagina and anal canal. Primary function is to provide a protective barrier
Nonkeratinized
Type of Stratified squamos epithelium
found in the epidermis of thick and thin skin and consist of surface layers of dead cells filled with keratin and no nucleus .
Keratinized
Epithelium found lining sweat glands
Stratified Cuboidal Epithelium
Epithelium found conjunctiva of the eye and ducts of some large glands.
Stratified Columnar Epithelium
Location of pseudo stratified epithelium with cilia
many portions of respiratory tract e.g. trachea , primary bronchi and nasal cavity.
Location of pseudo stratified epithelium without cilia
is found in ducts of male urethra and epididymis
Function of pseudo stratified epithelium
protection , motility , and sensory perception
Composed of 2-6 layers of cells , found exclusively in the portions of urinary system , where it lines the urinary bladder , ureter and parts of urethra.
Transitional epithelium (Lower cell layers are cuboidal but apical layers can be variable in shape . When the bladder is distended the apical cells are flattened , however when the bladder is empty these cells have rounded)
Function of transitional epithelium
Protective by forming a barrier between the urine and underlying tissue . The apical cells have unique intracellular plaques which effectively form a physical shield. Also possesses distensible property
Reversible conversion of one type of epithelial cells into another
An adaptive response to stress , chronic inflammation etc.
The most common epithelial metaplasia is columnar to squamous
Epithelial Metaplasia
Gland that
remain connected to the surface by an excretory duct that transports the secretory product to the outside.
Exocrine glands
Gland that
lack an excretory duct and their product is released into blood circulation
Endocrine glands
