Pituitary gland Flashcards
List the anterior pituitary gland hormones
1) LH
2) FSH
3) Prolactin
4) ACTH
5) TSH
6) Growth hormone
List the 5 different cell types of the pars distalis
1) Thryotropes (TSH)
2) Corticotropes (ACTH)
3) Gonadotropes (FSH/ LH)
4) Somatotropes (GH)
5) Lactotropes (Prolactin)
State the cell type found in the pars intermedia and what hormone it produces
-Melanotropes (MSH)
Which cells of the pars distalis stain blue and which stain red?
Somatotropes and lactotropes are acidophiles hence stain red
Corticotropes, thyrotropes and gonadotropes are basophils and so stain blue
What are the 3 hormones that regulate GH?
1) GH releasing hormone
2) Somatostatin
3) Ghrelin (secrete GH in response to food)
What are the affects of GH?
- Stimulates IGF-1 secretion from the liver
- Growth
- Stimulate protein synthesis
- Stimulates lipolysis
- Inhibits glucose utilisation (inhibits insulin)
How is prolactin regulated?
- Tonic inhibition by dopamine
- Can be stimulated by TRH
- Hypertrophy of lactotropes occurs during pregnancy
What do corticotropes produce?
POMC
ACTH
Describe the pars intermedia
Series of small cystic cavities, the follicles are filled with colloid
Give examples of short and long feedback loops
- Short= hormones from pituitary gland (e.g. ACTH) feedback to hypothalamus (less CRH from hypothalamus)
- Long= hormones from gland (e.g. cortisol) feedbacks to hypothalamus
What are independent systems?
Systems that do not depend on hypothalamus or pituitary gland
e.g. calcium regulation ->PTH, calcitonin, active Vit D
or Glucose regulation -> insulin, glucagon, epinephrine
Discuss pituitary dwarfism
- Common in german shepherds
- Cyst forms instead of adenohypophysis
- No GH so you get a small dog
- No ACTH= hypoadrenocorticism
- No TSH= hypothyroidism
Which hormones are associated with the posterior pituitary gland?
ADH and oxytocin
What are the clinical signs of dehydration?
- Prolonged skin tent
- Dry mucous membranes
- Sunken eyes
Describe the detection of dehydration
- Osmoreceptors within the hypothalamus
- Respond to increase in osmolarity of the ECF
- More concentrated= higher osmolarity and so more ADH is released so more water conserved.
- Stretch receptors (detect decreased distension and send nervous impulses to hypothalamus ->secrete more ADH)
What are the actions of ADH?
- Acts on DCT and CD= increases permeability to water (when ADH is present aquaporins present on apical membrane)
- Water reabsorption increases
- Urine volume decreases
- Urine concentration increases
Which aquaporin receptor is under ADH control?
- AQP-2
- The aDH binds to the receptor and activates adenyl cyclase-> produces cAMP triggering the vesicles containing aquaporin to move to the cell surface
What causes diabetes insipidous?
ADH dysregulation
Describe the two forms of diabetes insipidous
- Neurogenic: inadequate release of ADH from pituitary
- Nephrogenic: inadequate response to ADH within the kidney
How do you diagnose diabetes insipidous?
-Injection of exogenous ADH (if concentrated urine produced then you know its nephrogenic but if it dilute still you know it is nephrogenic)
Where is alpha lactalbumin produced?
In the mammary epithelial cells
It forms a complex with galactosyltransferase which forms lactose synthase.
Describe the neuronal transmission of oxytocin secretion
- High density of nerve endings in teats detect suckling
- Impulses are transmitted via superficial sensory pathways and inguinal nerve
- Afferent sensory neurons enter lumbar segments of the SC
- Ascend SC sensory tracts to the thalmus
- Secretion of oxytocin from nerve endings in posterior pituitary into circulation
What are the affects of oxytocin on the mammary gland?
- Increases pressure within the alveoli
- Reduces resistance in the excretory ducts
- Reduces resistance in teat canal
- Resulting in increased milk outflow
How does oxytocin reduce resistance in the ducts and teat?
- The myoepithelial cells surrounding the alveoli are orientated along the long axis of secretory duct, oxytocin makes the duct become shorter and wider
- Has opposite effect on circular sphincter muscle of teat= causes relaxation
