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
The pituitary gland, other name? Location? Hormones?
- Hypophysis
- Base of brain
- TSH (thyroid stimulating hormone), ACTH (Adrenocorticotrophic hormone), FSH (follicle stimulating hormone), LH (luteinising hormone), growth hormone, prolactin, MSH (melanocyte stimulating hormone), ADH OR vasopressin (anti diuretic hormone), oxytocin
Thyroid gland, location? Hormones?
- Anterior to the trachea (two lobes)
2. Thyroxine (T4), tri-iodothyroinine (T3)
Parathyroid gland, location? Hormones?
- 4 of them (2 pairs), each lies on the dorsal surface of the thyroid gland
- PTH (Parathyroid hormone/parathormone, parathyrin)
Adrenal glands, location? Hormones?
- Sits atop each kidney (Cortex surrounds each medulla)
2. Corticosteroids, androgens, oestrogen, progestin
Pancreas, location? Hormones?
- Left of and behind the stomach
- Exocrine = secretes digestive enzymes into duodenum
Endocrine (islet of langerhans): alpha cells = glucagons, beta cells = insulin
What are the two amino acid derived hormone types?
- thyroid hormones (T3, T4)
- catecholamines (adrenaline, noradrenaline)
What is described as the master conductor of the endocrine system?
Hypothalamus
Explain the way the hypothalamus works with relation to hormones.
- Vasopressin and oxytocin travel to posterior pituitary via nerves
- six other hormones travel via the hypothalamo-hypophyseal portal system to the anterior pituitary in the blood
How does a portal circulatory system differ from a normal one? And where are the only 2 portal circ systems found in humans?
- Blood travel-
Normal: Arteries, arterioles, capillaries, venule, veins
Portal: Arteries, arterioles, capillary bed 1, capillary bed 2, venule, veins - Head: between the hypothalamus and pituitary (hypophysis)
Abdomen
