Glands introduction - lecture 7 Flashcards
Define ‘gland’
An epithelial cell or an aggregate of epithelial cells that are specialised for the secretion of a substance.
What is an example of a single cell gland?
Goblet cell.
What is the position of the brain in terms of the hypothalamus, pituitary gland and thalamus?
Thalamus
Hypothalamus
Pituitary gland
What are endocrine glands?
- Glands that secrete directly into blood flowing through them, to transport them to different parts of the body.
- Secretions are called hormones.
- Have no duct.
- All epithelial cells in the gland secrete the hormones.
What are exocrine glands?
- Glands that secrete into a location of the body through a duct.
- Secrete enzymes or lubricants.
- Located in places derived from endo or ecto derm.
- Only cells at the apex (end) of the duct secrete the products.
Give some examples of endocrine glands.
PITUITARY GLAND:
- Anterior part produces hormones regulating most glands in endocrine system, as well as prolactin (milk production) and somatotrophin (growth of body tissues).
- Posterior part produces ADH (prevents water loss from kidneys) and oxytocin (signals uterus for delivery).
THYROID GLAND: T3 and T4 (thyroxine) that control metabolism and calcitonin and are involved in calcium homeostasis.
PARATHYROID GLAND: Parathyroid hormone (PTH) which impacts calcium homeostasis.
Give some examples of exocrine glands.
SALIVARY GLAND: secretes saliva - partial digestion of food and lubrication of bolus.
PANCREAS: Secretes amylase, trypsin and lipase to digest carbs, proteins and fats.
MAMMARY: Produces colostrum and milk in response to prolactin and oxytocin hormones that nourish neonates.
SWEAT GLANDS: secrete sweat.
SEBACEOUS GLANDS: attached to hairs, secrete sebum onto skin and in ear to protect tissues from pathogens.
LECHRYMAL GLANDS: secretes an aqueous fluid to moisten the eye and produces lysozome to attack bacteria.
What are the 3 modes of secretion from a gland?
Merocrine
Apocrine
Holocrine MAH
What is merocrine secretion? And give an example.
Secretion through excytosis: Secretory granules accumulate in a vesicle inside the cell which fuses with plasma membrane. Its contents are released out of the extracellular surface and dispersed by diffusion.
Beta cells of the pancreas secrete insulin.
What shape are exocrine and endocrine glands?
Exocrine = compound cuboidal
Endocrine = simple cuboidal
What is apocrine excretion? And give an example.
A non-membrane bound structure approaches the cell surface from within and makes contact. It pushes up the apical membrane. A thin layer of the apical membrane surround the droplet and pinches off from the cell.
The breast during lactation.
What is halocrine excretion? And give an example.
The whole cell becomes disintegrated. The cell fills up with secretory granules. Organelles degenerate and die. Plasma membrane breaks and the contents (secretum) empties. Dead cells are replaced by mitotic division of basic cells.
Sebaceous gland secretes sebum.
Describe endocytosis.
Engulfing of molecules inside the cell via vesicle formation.
What is transepithelial transport?
The movement of substances across the epithelium through epithelial cells using a variety of methods:
- Passive movement through aqueous channel in the intracellular junction (paracellular transport)
- Transcellular transport through lipid cell membranes.
- Through carrier proteins (in or out).
- In via endocytosis and out the other side via exocytosis.
Define and explain adenogenesis.
Gland formation.
Diagram on slide / in workbook to learn.
