Session 2 Flashcards
What is an exocrine gland?
- Ducts with glands
Define gland
- An epithelial cell or collection of cells specialised for secretion
What is an endocrine gland?
- A ductless gland that secretes directly into the bloodstream
How can glands be classified?
- Destination of secretion
- Structure
- Nature of secretion
- Method of secretion
How are glands classified by structure?
- Unicellular or multicellular
- Acinar (alveolar) or tubular
- Coiled or branched
- Simple or compound
Give an example of a unicellular gland
- Goblet cell in the upper respiratory tract and in the intestines
What happens to the gland in cystic fibrosis?
- Cystic Fibrosis Transmembrane Regulator ion channel molecule is not present in epithelial cells
- Chloride ions are not transported across the membrane out of the cell
- Water stays in the epithelium and does not diffuse into the respiratory tract lumen, causing the mucus to become viscous and dehydrated
- The mucus can no longer be moved easily and pulmonary infections can then occur
Give an example of an Acinar/alveolar gland
- Pancreatic exocrine acinar cells
What is the difference between simple and compound glands?
- Simple glands: have non-branching ducts
- Compound glands: branching ducts
How are glands classified by nature of secretion?
- Mucous or serous glands
What is a mucus gland?
- Secretions contain mucus, which is rich in mucins (highly glycosylated polypeptides)
- Cells stain poorly in H&E sections
What is a serous gland?
- secretions are often of enzymes, are watery and free of mucus
- stain pink (eosinophilic) in H&E sections
What are the major salivary gland?
- Parotid
- Submandibular
- Sublingual
How are glands classified by method of secretion?
- Merocrine
- Apocrine
- Holocrine
What is Merocrine secretion?
- Exocytosis
- Membrane bound vesicle approaches cell surface
- The vesicle membrane fuses with the plasma membrane
- Contents are in continuity with the extracellular space
- Plasma membrane is now larger
- Membrane is retrieved, stabilising the cell surface area
What is apocrine secretion?
- Non-membrane bound structure (eg lipid) approaches cell surface
- Makes contact and pushes up apical membrane
- Thin layer of apical cytoplasm drapes around droplet
- Membrane surrounding droplet pinches off from cell
- Plasma membrane is now smaller
- Membrane added to regain original size
Give an example of an apocrine gland
- Mammory glands
What test is used for cystic fibrosis and why?
- Sweat-testing for abnormally salty sweat
- Sweat is rich in sodium and chloride ions as the CFTR molecule is absent, so chloride ion reabsorption is poor in ducts of sweat glands
What is Holocrine secretion?
- Cell disintegrates
- Contents are released
- Whole cell is discharged
Give an example of a Holocrine gland
- Sebaceous glands
What is endocytosis
- Engulfing of material initially outside the cell
What is transepithelial transport?
- Endocytosis and exocytosis combined
- Material is endocytosed at one surface
- Transport vesicles shuttle across cytoplasm
- Material exocytosed at opposite surface
Describe the structure of the Golgi Apparatus
- Stack of disc-shaped cisternae
- One side of the discs are flattened, the other concave
- Discs have swellings at their edges (budding vesicles)
- Swellings pinch off as migratory Golgi Vacuoles
Where does glycosylation take place in the Golgi apparatus?
- Cisternae
Describe the function of the Golgi Apparatus
- Sorting into different compartments
- Packaging through condensation of contents
- Glycosylation (adding sugars to proteins and lipids)
- Transport of vesicles