histology endo/exocrine Flashcards
pineal gland
er above 3d brain ventricle
-conn to brain by pineal stalk, sem er m evagination of roof of 3d ventricle (pineal recess)
-pineal stalk has nerve processes from adj. regions of brain (unclear if a functional link is milli those n.fibers og pineal endoccrine funct)
-Pineal gland surr by CT capsule, cont. w pia-arachnoid meninges
-pineal gland function is regulated by hormonal + neuronal stimul.
neurohypophysis (post. pitituary)
1) pituicytes
-glial cells (resembling astrocytes), assist in storage/release of hormones.
Interspersed milli nerve terminals
2)neurosecretory neurons
-axons terminals in pars nervosa, often distended w alot of neurosecr. material, w aggregates of membrane bound granules
-contain oxytocin og adh og carrier protein neurophysin
-neurosecr. material synth in cell bodies of supraoptic + paraventricular nuclei.
(adh og oxytocin synth. as large macromolecules that have the hormone + respective neurophysin)
-as the macromolecules are transp.to nerve terminals–> covalent bond milli hormone + neurophysin cleaved (though they remain closely associated)
*Herring bodies:
pars nervosa m very distended axon terminals
neurohypophysis (post. pitituary)
Subdivision:
-into pars nervosa (infundibular process)
-infundibular stem
-median eminence
(median eminence, a part of tuber cinereum
sem makes up p. of 3d ventricle. Poorly dev. in humans)
Hormones:
-adh -oxytocin -releasing hormones
Releasing hormones:
-regulate secr. of hormones from spec. adenohypophysis cells
(releasing hormones important in control of pars distalis include: TRH, GnRH og corticotropin releasing hormone CRH)
pituitary adenomas
common tumor of ANTERIOR pituitary gland.
-their growth may suppress hormonal prod in other secr. cells of the pars distalis
pituitary hormones (pars distalis)
1) somatotropin (SRH releasing/somatostatin inhibiting)
-general effects on most cells to incr. metabolism.
-stimulate liver to release somatomedins
(insulin-like-growth F I og II)–> incr proliferation cartilage + assists in growth long bones
2) prolactin (PRH/PRI)
3) adenocorticotropic hormone ACTH
(CRH releasing hormone)
-stim. synth+release hormones (cortisol og corticosterone) from supraren cortex
4) FSH ( gnrh releasing/in males inhibin also)
-stim. 2ndary follicle growth + estrogen secr.
-stim sertoli cells to prod. androgen binding protein
5) LH women (gnrh)
-hjálpar FSH promote ovulation, forming corpus luteum, secr progesterone/estrogen.
Forming neg.feedback to hypothalamus to inhibit GnRH in women
6) LH men
-stim. leydig cells secr/release testostrone,
which forms neg.feedback to hypothalamus to inhibit GnRH in men
7)TSH (TRH/negative feedback via CNS)
-stim. synth/release of thyroid hormone—>
incr. metabolic rate
adenohypophysis (anterior pituitary)
cells:
hormone secr. parenchymal cells
1)acidophils
a) lactotropes (mamotropes)
b) somatotropes
2)basophils
a) corticotropes (ACTH and, melanocyte-S-hormone and lipotropin)
b) thyrotropes
c) gonadotropes
3) chromophobes
probably acidophils/basophils, lost their staining properties after release of granules
hormone target interaction
Many target cells sect. hormones when stim. by adenohypophysial hormones –>
target cells hormone give feedback that help regulate adenohypoph. funct
(td female: FSH og LH by gonadotropic basophils, stim. ovaries prod steroids from dev. follicles + theca interna cells—>
ovarian steroids give hypothalamus feedback which regulates level of GnRH, and thus amount of FSH og LH
hypophysis embryology
- post.pituitary (neurohypophysis/pars nervosa) derived from downgrowth of n.tissue from hypothalamus, remains joined by pituitary stalk.
- ant. pituitary arises as epith. upgrowth from roof of primitive oral cavity (Rathke’s pouch). -this spec. glandular epith is wrapped around ant aspect of post. pituitary.
hypophysis cerebri (pituitary gland)
subdivision:
-pinkish (vascularized) ant lobe
-whitish (neuronal) post lobe
-it is the master control of endocrine system
Regulates basal metab.rate og other endocrine organs (adrenal cortex), reprod.system, mammary glands + overall growth of body
-in most cases, target organs prod hormones that alter funct. of pituitary gland
–> feedback regulates prod. of pituitary hormones
hypophysis cerebri (pituitary gland)
located at base of brain, adj to 3d ventricle
-multiparous women have larger pit.gland
-it lies at base of 3d ventricle, in sella turcica (sphenoid bone)
-dura mater is discont. at the gland, but it surr the stalk and closes the sella with a membr. covering (diaphragma sellae)
zona fasiculata (middle zone adrenal cortex)
glucocorticoids:
td hydrocortisone (cortisol) and
corticosterone
(control general metabolism)
og:
-anabolic effect on liver (uptake of FA, aa, c.hydrates for glucose synth + glycogen polymerization.
-catabolic effect in other tissues (td in adipocytes, they stim. lipolysis. In muscle they stim. proteolysis)
-circulating glucocorticoids at above normal levels, infl anti-infl response–>
inhibiting macrophage/leukocyte infiltration at infl site.
-also supress immune response by inducing atrophy of l.system (reducing circulating l.cyte population)
-negative feedback, partly controlled by plasma concr.
(when blood level high: CRH cells inhibited
–> inhibits corticotrophs in pars distalis from releasing ACTH)
adrenal cortex og medulla
cortex: (mesoderm)
similar embryo.origin as gonads (like them secr steroid hormones, all structurally related to cholesterol)
-mineralocorticoids (electrolyte og fluid balance)
-glucocorticoids (c,aa,lipid metabolism)
-sex hormones
medulla: (ectoderm-n.crest)
similar embryo.origin as symp n system
(may be considered as highly spec. adjunct of that system)
-secr catecholamines (adrenaline/noradrenaline)
zona glomerusa (cortex adrenal) outer layer
outer cortical layer
-cells arranged in rounded clusters
-small round nucleus + few lipid droplets in cytoplasm
-z.glomerusa sometimes absent in human adrenal gland, in such cases–>
replaced by cells of z.fasiculata that ext. out into the capsule
-synth of mineralocorticoid hormones
z. reticularis (innsta lag cortext) next to medulla
cells smaller than in z.fasiculata and do not have abundant lipid droplets.
-en g verið með brownish lipofuscin granules
(lipofuscin granules somtimes in other 2 zones but most abundant in z.reticularis)
-lipofuscin granules m acid phosphatase activity (trúuð vera lysosome related residual bodies of lipid metabolism)
-cells arranged in reticulum
-synth. of androgen precursors —>
released to bloodstream, transp to gonads
—> conv. to testosterone/estrogen
adrenal medulla secretes
catecholamines under control of symp n system.
-not secr cont. But stored in membrane bound dense core granules.
(released only to n.stimuli similar to neurotransmitter release)
-the dense core secr. granules give rise to c.plasmic granularity (sést m microscope)
-also enkephalins (opioid peptides, involved in control of pain)
