[HISTO] HORMONE SECRETING CELLS & PITUITARY 1 Flashcards by Aseel Maher

Endocrine glands are formed of

secretory cells
CT stroma
fenestrated capillaries

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steroid hormone secreting cells are characterized by

sER
mitochondria with tubular cristae
lipid droplets

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steroid hormones produce

precursor hormones which form steroids by cholesterol metabolism in mitochondria/sER

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hormones which can easily diffuse through cell membrane

steroid hormones (lipophilic)

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hormones which require cell surface receptor & 2nd messenger to mediate their effect

peptide hormones (hydrophilic)

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peptide hormone secreting cells are characterized by

rER
Golgi complex
secretory granules

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how do peptide hormones achieve their effect

by binding to membrane receptors—>hormone-receptor complex—> (+) 2nd messenger—>2nd messenger mediates effect

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amino acid hormones examples

thyroid hormones
catecholamines
dopamine
ALL DERIVED FROM TYROSINE

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pure endocrine glands (5)

1-pituitary
2-pineal
3-thyroid
4- parathyroids
5-adrenal

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mixed endocrine glands (6)

1-islets of Langerhans
2-interstitial cells of Leydig
3- Hepatocytes
4-ovarian follicles
5-corpus luteum
6-Hypothalamic neurosecretory cells

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scattered isolated cells (5)

1-enteroendocrine cells
2-juxtaglomerular cells
3- cardiac muscle fibers
4- white adipocytes
5- epithelial reticular cells (thymus)

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function of enteroendocrine cells

secrete ghrelin in stomach mucosa
(+) appetite & GH release

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function of juxtaglomerular cells

*secrete renin
control GFR & BP

*secrete erythropoietin
(+) erythrocyte production in red marrow
(-) erythrocyte precursors apoptosis

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function of cardiac muscle fibers

secrete ANF
promotes Na-H2O loss in urine
(DIURETIC EFFECT)

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renin’s effect

(+)aldosterone production
↑ Na-H2O retention
∴ ↑ BP

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renin release increases in case of

low BP

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function of white adipocytes

secrete leptin (satiety factor)
regulates appetite + adipocytes formation

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function of epithelial cells of thymus

differentiation & maturation of T-thymocytes

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modes of hormone secretion

paracrine
juxtacrine
autocrine

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juxtacrine secretion

signaling molecules remain on cell’s surface & mediates respone when target cells make contact

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paracrine secretion?
examples?

act on target cells a short distance away
ex: gastrin, histamine

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autocrine secretion?
examples?

acts on itself
ex: prostaglandins

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gastric hormone is secreted by?
mode of secretion?

pyloric G cells
paracrine

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principle organizers of endocrine glands

hypothalamus & pituitary

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pituitary is regulated by

(+): hypothalamic secretions (-): negative feedback

pituitary gland lies outside the___

blood-brain barrier

hypothalamus is regulated by

negative feedback from pituitary & target organ hormones

pituitary grows in size during

pregnancy

site of pituitary

sella turcica

pituitary is physically connected to hypothalamus by

infundibular stalk

roof of pituitary is formed by

diaphragma sellae (dura)

embryological divisions of pituitary

adenohypophysis neurohypophysis

anatomical divisions of pituitary

anterior lobe= Pars distalis & tuberalis posterior lobe= Pars nervosa & intermedia + neural stalk

adenohypophysis is formed of

Pars distalis Pars intermedia Pars tuberalis

oral component of pituitary

adenohypophysis

neural component of pituitary

neurohypophysis

adenohypophysis develops from

ectodermal up-growth from buccal cavity that forms Rathke's pouch

neurohypophysis develops from

down growth from hypothalamus

neurohypophysis is formed of

Pars nervosa Infundibular stalk

main part of gland which represents 75% of total gland volume

Pars distalis

parts of pars distalis

stroma= capsule & reticular CT parenchyma= secretory cells & fenestrated capillaries

types of cells of pars distalis

chromophobes chromophils

chromophobes characteristics

smaller polygonal pale cytoplasm central rounded nucleus few granules (EM)

types of chromophobes

1-partly degranulated cells (resting stage) 2-undifferentiated stem cells 3-follicular stellate (phagocytic/supporting. NOT secretory)

types of chromophils

acidophils basophils

types of acidophils

somatotrophs mammotrophs

types of basophils

thyrotrophs gonadotrophs corticotrophs

acidophils characteristics

35% of total pars distalis cells site: posterolateral smaller than basophils rounded/polygonal vesicular nuclei !!PAS NEGATIVE!! *rER *Golgi *secretory granules GRANULES STAIN BY EOSIN & ORANGE G

Basophils characteristics

15% of total pars distalis cells site: peripherally larger angular vesicular nucleus !!PAS POSITIVE!! *rER *Golgi GRANULES STAIN BY Hx

why are the granules of basophils PAS positive?

their hormones are glycoproteins in nature

function of basophils

secrete trophic hormones

most abundant cells in pars distalis

somatotrophs

somatotrophs characteristics

close to capillaries ovoid electron dense granules *rER *Golgi STAINED ORANGE BY ORANGE G PAS NEGATIVE

somatrophs functions

secrete GH

GH secretions induces

somatomedins synthesis by liver cells--->protein synthesis-->growth & elongation of long bones

GH secretion is controlled by

(+): GhRH & Ghrelin (-): GIH (Somatostatin)

mammotrophs characteristics

polygonal *few rER *Golgi enlarge during pregnancy thru hypertrophy & hyperplasia PAS NEGATIVE

mammotrophs function

secrete PRL (+)mammogenesis initiate + maintains milk secretion

PRL secretion is controlled by

(+): PRH (-): PIH (Dopamine)

hyperplasia of pituitary in newborn is due to

high estrogen levels from the mother

thyrotrophs characteristics

LEAST in no. SMALLEST granules Large polygonal PAS positive

function of thytrotrophs

secrete TSH

TSH secretion is controlled by

(+): TRH (-): negative feedback by T3 & T4

gonadotrophs characteristics

fusiform PAS POSITIVE electron dense granules

gonadotrophs function

secrete FSH * (+) maturation of ovarian follicle * (+) spermatogenesis *(+) androgen binding protein synthesis secrete LH *(+) ovulation *(+) interstitial cells of Leydig--> (+) testosterone secretion

LH in males is called

ICSH (interstitial cell-stimulating hormone)

androgen binding protein is synthesized by

Sertoli cells

corticotrophs characteristics

oval PAS POSITIVE electron dense granules

corticotrophs function

secrete POMC *cleaved to ACTH *cleaved to β-lipotropic hormone

ACTH function

(+) zona fasiculata in adrenal cortex

β-lipotropic hormone function

regulate lipid metabolism

corticotrophic hormones secretion is controlled by

(+): CRH (-): negative feedback by cortisol

tropic hormones are released into capillaries of pars distalis by

tuberoinfundibular stalk

axons of tuberohypophyseal neurons form? terminates in?

tuberoinfundibular stalk median eminence

only hormones which are regulated by BOTH releasing & inhibiting tropic factors

GH PRL