5) Glands Flashcards
Define a gland
An epithelial cell or aggregate of epithelial cells that are specialised for the secretion of a substance
Define secretion
The production and release of material from epithelial cells or an aggregate of epithelial cells
How are glands typically classified?
1) Structure
2) How they secrete their product
What are endocrine glands?
Glands that secrete hormones directly into the blood flowing through them into distant parts of the body
What are exocrine glands?
Glands that secrete substances, typically lubricants and enzymes, into ducts
What is a benefit of a gland secreting it’s product directly into the bloodstream?
This allows the secretion to function at distant parts of the body
Which cells secrete hormones?
All epithelial cells in endocrine glands
Which cells secrete enzymes and lubricants ?
Cells at the apex of the duct in exocrine glands
What types of epithelial cells are present in endocrine glands?
Simple cuboidal epithelial cells
What type of epithelial cells are present in exocrine glands?
Simple cuboidal epithelial cells
Complex epithelial cells
How are endocrine glands generated?
1) Mesenchymal cells under the epithelium produce fibroblast profactors (typically 7 & 10), which causes the epithelial cells to grow towards the mesenchymal
2) As the epithelial cells grow they produce multiple enzymes that breakdown the extracellular matrix (connective tissue) that surrounds the mesenchymal, allowing the cell room to grow
3) Central cells and surface cells die during programmed cell deat or apoptosis, forming a duct i the middle
4) As the duct elongates the apical cells differentiate and change function, allowing them to begin secreting substances
How are exocrine glands generated?
1) Mesenchymal cells under the epithelium produce fibroblast profactors (typically 7 & 10), which causes the epithelial cells to grow towards the mesenchymal
2) As the epithelial cells grow they produce multiple enzymes that breakdown the extracellular matrix (connective tissue) that surrounds the mesenchymal, allowing the cell room to grow
3) Aniogenic factors are produced (growth factor 1), which causes the development of blood vessels between and around the epithelial tissue
4) Apoptis occurs, causing thduct cells to dissapear and the gland to separate from the epithelial tissue.
5) The tissue moves away from the epithelial surface and proliferates
What are mesenchymal cells?
Cells that we dont know the function of
How do limbs form?
Mesenchymal cells produce epidural profactors qhich caus ethe epithelial cells to grow away from the mesenchymal
What enzymes are produced by the epithelial cells during the generation of glands?
Lipase - breaks down lipids
Elastase - breaks down elastin
Collagenase - breaks down collagen
Plasmin - breaks down fibrin
What are the 4 ways of gland secretion?
Merocrine
Apocrine
Holocrine
Cytocrine
What is merocrine secretion?
The fusion of vesicles with the apical membrane which is then released by epithelial cells or glands
What is apocrine secretion?
The partial loss of the top of the cell or the cytoplasm which is lost into the duct (therefore exocrine secretion)
What is holocrine secretion?
The complete loss of the cell cytoplasm
What is cytocrine secretion?
The release of the entire cell
Define exocytosis
The secretion of molecules outside of the cell via a vesicles fusing to a membrane
Define endocytosis
The engulfing of molecules inside of the cell via vesicle formation
Why is exocytosis important?
To prevent the cell from bursting after endocytosis
What is phagocytosis and which cells use this process?
The process by which cells envelop or engulf other cells or particles
Mainly used by cells of the immune system
What is pinocytosisis and which cells use this process?
The process in which liquid droplets are ingested by cells
Used by all cells but particularly smooth muscle
How does branching and/or elongation of glands occur?
1) Basic growth factors (FGF10) are released by mesenchymal cells
2) The epithelial cells move towards the signal
3) Different growth factors are active or inactive resulting in tubule elongation and branching
