Pituitary Gland (hormones & histology)


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  • Created by: Becca
  • Created on: 24-12-13 15:58
What is anterior pituitary also known as? What is it divided into?
Glandular lobe, adenohypophysis. Divided into pars distalis/tuberalis/intermedia
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What is the posterior pituitary also known as? What is it divided into?
Neural lobe, neurohypophysis. Divided into pars nervosa, infundibular stem & median eminence
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What is the embryology of pituitary development?
Pituitary is in 2 pieces because if forms from an ectodermal upgrowth from roof of primitive mouth & a neuroectodermal downgrowth of the brain
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What is the blood supply to the pituitary gland?
Branches of supeior & inferior hypophyseal arteries, drained by inferoir hypophyseal veins. Sup artery divides, forms capillary bed in post lobe, portal vessels travel down, forms new capillary bed in ant lobe. Capillary plexus gets messages (brain)
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What are the neronal pathways between the hypothalaus in the brain & the pituitary?
Arcuate, ventromedial & preoptic nuclei attach to superior capillary bed via nerve processes. Releasing/inhibitory factors pass along portal vessels to reach inf capillary beds. Paraventricular & supraoptic nuclei send nerves directly into post pit
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What is the histology of the posterior pituitary lobe?
Neural: axons with dilations, nuclei belong to pituictyes (specialised glial cells)
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What is the histology of the anterior pituitary lobe?
Endocrine: vascularised, chromophils (actively secreting cells) - Acidophils -> somatotrophs (GH), mammotrophs (prolactin). Basophils -> corticotrophs (ACTH), thyrotrophs (TSH). Cells secreting glycoproteins -> gonadotrophs (LH, FSH). Chromophobes
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Which hormones are released by the anterior pituitary? (-trophin/-tropin)
Somatotropin (GH), prolactin, corticotropin (ACTH), thyrotropin (TSH) & gonadotropins (LH, FSH)
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What is the chemical structure of the different anterior pituitary hormones?
Somatotropin & prolactin = single-chain polypeptide with disulphide bridge. Cortiotropin = small peptide. Thyrotropin & gonadotropins = glycoproteins with two subunits
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What is the role of somatotropin?
Growth hormone: major role in growth, particularly linear, and development. Also affects metabolism
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What is the role of prolactin?
Stimulates mammay glands to produce milk (lactation), promotes growth & development of the breasts. High prolactin concentration inhibits GnRH release (no period during breast feeding)
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What is the role of corticotropin? What is it's chemical structure & origin?
Adrenocorticotropic hormone (ACTH) stimulates synthesis/release of cortisol. It is a small peptide synthesised from a very large precursor glycoprotein called pro-opiomelanocortin (POMC)
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What is the role of thyrotropin?
TSH stimulates synthesis & release of thyroid hormones
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What is the role of the gonadotropins?
Luteinizing hormone (LH) in the ovaries & testes (Leydig cells) stimulates steroid hormone synthesis (causes ovulation/formation of corpus luteum). FSH stimulates follicular development in ovaries & spermatogenesis in testes (Sertoli cells)
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Whch anterior pituitary hormmones do the followin hypothalmic hormones control: GnRH, GHRH, somatostatin, TRH, dopamine, CRH?
GnRH (gonadotropin-releasing hormone) -> +LH/FSH. GHRH (growth hormone) -> somatostatin/+GH. Somatostatin -> -GH/TSH. TRH (thyrotropin-releasing hormone) -> +TSH/prolactin. Dopamine -> -prolactin. CRH (corticotropin-releasing hormone): +ACTH
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What are the hormones of the posterior pituitary?
Arginine vasopressin (AVP, or antiduretic hormone ADH) & oxytocin
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What is the simulation & actions of AVP?
Stimulated by increase in body fluid osmolality, fall in blood volume/pressure & stress. Acts on blood vessels -> vasoconstriction via V1 receptors & kidneys -> increases permeability & hence re-absorption of water via V2 receptors (works in DCT/CD)
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What is the stimulation of oxytocin? What is its release mechanism & actions?
Stimulated by suckling & cervical stimulation (parturition). Released via positive feedback control: suckling/distension -> sensory nerves -> hypothalamus -> post pituitary -> milk let-down/contraction uterine smooth muscle
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What is the posterior pituitary also known as? What is it divided into?

Back

Neural lobe, neurohypophysis. Divided into pars nervosa, infundibular stem & median eminence

Card 3

Front

What is the embryology of pituitary development?

Back

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Card 4

Front

What is the blood supply to the pituitary gland?

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Card 5

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What are the neronal pathways between the hypothalaus in the brain & the pituitary?

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