Topic 6 - Glands Flashcards
What is a gland?
- epithelial cell(s) that are specialised for the secretion of a substance
What are the two ways to classify a gland?
- By their structure
2. By how their products are released
What makes a gland endocrine?
- no duct
- secrets hormones directly into bloodstream
- all the epithelial cells secrete the hormone in that particular gland
What makes a gland exocrine?
- ducted (more specific/ localised delivery)
- secretes enzymes/lubricants usually
- only cells at the apex of the duct secrete the products
Give examples of endocrine glands.
- Pituitary (hypothysis), thyroid, parathyroid
Give examples of exocrine glands.
- salivary, pancreas, mammary, sweat, sebaceous, lachrymal
Why is it useful for some duct epithelial cells in a gland to alter their morphology and become myoepithelial cells?
- then have features of both a smooth muscle cell and an epithelial cell
- can squeeze to eject the secretions from the duct
What are acinae?
- an acinus is a cavity at the end of a gland where all the secretory cells reside
What are the functions of the striated duct?
- keep the ductal system open
- reabsorb sodium ions
What are the 3(4) ways that glands secrete products?
- Merocrine - fusion of vesicles with apical membrane before budding off (exocytosis) e.g. endocrine glands in pancreas
- Apocrine - the top part of the cell is pinched off and forms the secretion e.g. lactating mammary gland and external genitalia sweat glands
- Holocrine - Mature cell dies and becomes secretory product e.g. sebaceous gland in skin, tarsal glands in eyelid
(4) . Cytocrine - living cells released as secretion e.g. spermatozoa is only example of this
Briefly explain the 2 different types of Merocrine secretion.
- Regulated Secretion - accumulation of secretory product in large vesicles and is released via exocytosis upon receiving stimulation signal. ACTIVE PROCESS, Requires Ca2+ ions and ATP to work
- Constitutive Secretion - Secretory product is packaged into small vesicles and continuously released to the cell surface
Explain Holocrine secretion.
- Secretory cell gradually fills up with secretory product (granules)
- Cell organelles degenerate (not enough room)
- Cells die
- Plasma membrane breaks and the contents are spilled out
- Dead cells are replaced by mitotically dividing basal cells
What is glycosylation of a protein/lipid?
And what is its role?
- covalent attachment of sugars by enzymes to proteins/lipids to form glycoproteins/glycolipids
- aids protein folding/prevents digestion by lipases or proteases/cell recognition
Define phagocytosis and pinocytosis.
Phagocytosis - The process by which cells engulf or envelop other cells/particles
Pinocytosis - process by which liquid (e.g. lipid) droplets are ingested by cells
Both are endocytosis
What are the 3 types of glandular control?
- Humoral
- Neural
- Hormonal
All 3 via negative feedback loops