Glands Flashcards
Define a duct
An epithelial cell or aggregate of epithelial cells that are specialised for the secretion of a substance
Define endocrine gland
Endocrine glands secrete directly into the blood allowing substances to function at distant targets
Define exocrine gland
Exocrine glands secrete into a local area through a duct
Describe the first two steps of gland formation
- Mesenchymal stem cells produce fibroblast growth factor that causes epithelial cells to proliferate downwards
- Daughter cells make extracellular protein degradation enzymes to break down collagen and elastin so proliferating bud can invade that space
Following the first two steps of gland formation, explain how exocrine glands form in 3 steps
- Cells in centre of bud if grapes die producing the duct
- Elongation factors extend the gland
- Cells at the apex start to differentiate forming secretory portion of the gland
Following the initial 2 steps of gland formation, explain how endocrine glands then form
- Angiogenesis factors starts the growth of blood vessels around the gland
- Blood vessels elongate to find capillaries
- Cells migrating further away from original epithelial surface can either form a follicle or not
Explain how follicles are formed
Blood vessels formed around the gland
Colloid produced between the cells causes follicle expansion into a sphere
What factor causes duct branching?
FGF10
What factors are active and inactive in tubule elongation?
mTORC1 is active
ERK1/2 is off
What factors are active and inactive in angular division?
mTORC1 is inactive
ERK1/2 is active
What are the 3 classifications of gland based on their mode of secretion? Explain how they secrete
Merocrine - secretory vesicles fuse with apical membrane
Apocrine- partial loss of cytoplasm when vesicles are secreted
Halocrine- whole cell elongates until is bursts releasing secretory product
Explain in 6 steps how glucose causes insulin secretion
- Glucose binds to glucose 2 transporter on beta pancreatic cells
- Glucose metabolised increases ATP:ADP ratio
- ATP binds to ATP sensitive K+ channel closing it
- Build up if K+ inside the cell depolarises the cell membrane
- VOCC open when membrane depolarises- calcium enters the cell
- Calcium influx mobilises vesicles to fuse with membrane and secrete insulin
How does sulfonylurea treat diabetes type 1?
Sulfonylurea binds to ATP sensitive K+ channel closing the channel resulting in in insulin secretion
What cells make up the adrenal medulla and what is their function?
Chromaffin cells
Numerous pre synaptic nerves pass to chromaffin cells
Release adrenaline/noradrenaline when nerve impulses are received?
What are the 3 layers of the adrenal cortex and what do they secrete?
Zona glomerulosa- produces mineralcorticoids
Zona fasiculata- produces glucocorticoids
Zona reticularis- produce androgen precursors
Outline the long term stress response
- Threat detected by hypothalamus
- Hypothalamus releases CRH Corticotrophic releasing hormone
- CRH passes to hypothalamic-hypophyseal portal system to the anterior pituitary
- CRH acts on corticotrophs to release ACTH
- ACTH binds to ACTH receptors on the adrenal cortex to release mineralcorticoids and glucocorticoids
Outline then short term stress response
- Hypothalamus detects threat
- Sends nerve impulse to spinal cord
- Sympathetic pre ganglionic neurone sends impulse the chromaffin cells of adrenal medulla
- Adrenaline/noradrenaline release
What is the only kind of unicellular exocrine gland and what does is secrete?
Goblet cell
Secretes mucus
What is an acinus?
A cluster of cells arranged in a berry like lobe
What are the 3 types of salivary gland and what type of solution do they secrete?
Parotid - totally serous
Sublingual- totally mucus
Submandibular- mostly serous, partly mucous
What are the 2 ways the submandibular gland can be controlled?
Parasympathetic - controls serous secretion
Sympathetic- controls mucus secretion
What are the two types of hepatic blood supply?
Hepatic portal vein - 70-75% of blood
Hepatic artery- 25-30% of blood
What 3 things form the hepatic triad/ portal triad?
- Hepatic artery
- Hepatic portal vein
- Portal triad
Name 4 types of antigen presenting cells present in the liver
Kuppfer cells
Dendritic cells
Stellate cells
Pit cells
What is unusual about the apical and basolateral surfaces of hepatocytes?
Apical surface is at the side of the cell whereas the basolateral surface is on the outside of the cell, therefore surface specialisations e.g microvilli reside on the basolateral surface
What is the role of Kuppfer cells?
Recycle erythrocytes and ingest pathogens
What are stellate cells?
Stellate cells store Vitamin A
Proliferate during liver damage causing loss of vitamin A storage and differentiate to myofribroblasts which can deposit collagen causing liver fibrosis
What are the 4 functions of hepatocytes?
- Protein synthesis - abundant RER
- Carbohydrate metabolism - from fatty acids from carbs
- Lipid metabolism - form bile solute to solubilise fats
- Detoxification
