Glandular Tissues And How Cells Secrete Flashcards
Gland
An epithelial cell or collection of cells specialised for secretion
Exocrine
Glands with ducts - secrete onto an epithelial surface
Endocrine
‘ductless glands’ - secrete (hormones) into bloodstream
Unicellular glands
e.g. Goblet cell
CF
cystic fibrosis transmembrane regulator (CFTR) is not present in the apical membranes of the epithelial cells
Chloride ion transport across the membrane is compromised
RESPIRATORY TRACT - water does not leave the epithelium in sufficient quantities to adequately hydrate the secreted mucus
The mucus becomes viscous and can less readily be moved to the oropharynx for swallowing - serious pulmonary infection often occurs
GI TRACT - mucus also becomes too viscous
SWEAT GLANDS - poor reabsorption of chloride ions - sweat is rich in chloride and sodium ions - SALTY SWEAT
PANCREAS - the gut receives insufficient pancreatic digestive enzyme and malabsorption results
Acinar
alveolar
e.g. Pancreatic
Compound
If ducts branch
Combined tubular - mucous glands in mouth
Compound alveolar - mammary glands
Compound tubuloalveolar - salivary glands, pancreas
Mucous glands
secretions contain mucus - rich in mucking (highly glycosylated polypeptides)
Stain poorly with H&E - lightly stained
Serous glands
secretions (often enzymes) are watery and free of mucus
Pink in H&E sections (darker than mucous glands)
Merocrine secretion
(exocytosis)
(apocrine and eccrine sweat glands)
- membrane bound component approaches cell surface
- vesicle fuses with the plasma membrane
- contents are released into extracellular space
- plasma membrane is transiently larger
- membrane is retrieved, stabilising cell surface area
Apocrine secretion
e.g. lactating mammary glands
- non-membrane bound structure (e.g. lipid) approached the cell surface
- makes contact and pushes apical membrane
- thin layer of apical cytoplasm drapes around droplet
- membrane surrounding droplet pinches off from cell
- plasma membrane transiently smaller
- membrane has to be added to to regain original area
Holocrine Secretion
e.g. sebaceous glands fill hair follicle with sebum
- disintegration of cell
- release of contents
- discharge of whole cell
Endocytosis
- engulfing of material that is initially outside of the cell
- opposite of merocrine secretion
- Endo- and Exo-cytosis are coupled in transepithelial transport
Transepithelial transport
- material endocytosed at one surface
- transport vesicle shuttles across cytoplasm
- material exocytosed at opposite surface
Golgi Apparatus
Structure
- stack of disc-shaped cisternae
- one side of discs are flattened, other concave
- disks have swellings at their edges - distal swellings pinch off as migratory Golgi Vacuoles
Function
- sorting of proteins into different comparments
- adding of sugars to proteins and lipid (Glycosylation)
- transport of resultant vesicles
