TOB S2 - Glands and Internal surfaces of the body Flashcards
Define a gland.
A collection of epithelial cells specialised for secretion.
List the ways in which glands are classified.
Destination of secretion
Structure of gland
Nature of secretion
Method of discharge
How are glands classified by secretion destination?
Exocrine glands secrete into ducts or onto surfaces
Endocrine glands are ductless, secrete directly into blood
How are the secretory portion of glands classified by structure?
Uni/multicellular
How are multicellular glands classified? (think shape of secretory portion)
Alveolar, tubular, coiled, branched
What are the different types of ducts present in glands?
Simple
Complex (branched)
How are glands classified by nature of secretion?
Mucous or serous
Describe mucous secretion.
How does it react to H&E staining?
Contains mucus rich in mucin (glcosylated polypeptides)
Stains poorly with H&E stain
Describe serous secretions
How does it react to H&E staining?
Watery, no mucus, enzymes present
Stains pink with H&E stain
What are the three methods of secretion?
Merocrine, Apocrine, Holocrine
Describe the process of merocrine secretion
Membrane bound vesicle fuses with plasma membrane
Contents released into intracellular space
Additional area of plasma membrane recovered
Describe the process of Holocrine secretion.
Disintegration of whole cell releases all cellular contents
Describe the process of Apocrine secretion
Non membrane bound structures (eg. Lipids) approach apical cell membrane, are enveloped by cytoplasm then the plasma membrane.
Buds off releasing vesicles into intercellular space
Large amounts of plasma membrane lost (decapitation)
Plasma membrane added to to recoup loss.
What is endocytosis?
The opposite process to exocytosis (merocrine secretion)
Material outside cell is engulfed by plasma membrane and buds off into the cell cytoplasm.
Describe transepithelial transport
Material enters cell through endocytosis
Shuttled through cytoplasm in transport vesicle
Material is secreted on the other side of epithelial cell via merocrine secretion (exocytosis)
Describe the structure of the Golgi apparatus
Layers of disk shaped cisternae
Flattened on one side, concave on the other
Swellings at the edges of cisternae (bud off to form vesicles)
Describe the functions of the Golgi apparatus
Sorting and packaging of contents into vesicles
Glycosylation of proteins and lipids
Transport
Where do vesicles from the Golgi apparatus end up?
Majority exocytosed
Some retained (eg lysosomes)
Some enter plasma membrane (glycocalyx)
Why is the Golgi apparatus important to the maintenance of the glycocalyx?
Complex branching sugars produced in Golgi apparatus important to specific interactions of the glycocalyx.
How does enzyme damage to the glycocalyx affect its function?
Alters specificity based interactions of glycocalyx such as:
Adhesion to substrates and other cells
Communication with adjacent cells
Cell mobility
Contact inhibition of movement or division
What are the simple mechanisms of control of secretion?
Nervous control
Endocrine control
Neuro-endocrine control
Negative feedback chemical mechanism.
Give an example of nervous control of secretion
Sympathetic nervous stimulation of adrenal medullary cells promotes release of adrenalin.