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Functional Anatomy & Embryology > Anatomical Basis of Homeostasis II: Endocrine glands > Flashcards

Anatomical Basis of Homeostasis II: Endocrine glands Flashcards

1
Q

List characteristics of peptide/protein hormone cell

A
  • Lots of RER
  • Golgi
  • Secretory vesicles – vary in size
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2
Q

List characteristics of Steroid-secreting cells

A

Lots of smooth ER
Abundant mitochondria
Lipid droplets

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3
Q

What is function of pituitary gland?

A

Major interface between brain and the endocrine system.

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4
Q

Describe anatomy of pit gland

A
  • rounded body, about 1 cm dia.
  • connected to floor of III ventricle by the infundibulum (pituitary stalk), just posterior to the optic chiasma
  • lies in a depression in the body of the sphenoid bone = pituitary (hypophyseal) fossa - also called the sella turcica
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5
Q

What is the pit fossa lined and covered over by?

A
  • dura

- covered over by a sheet of dura (diaphragma sellae), pierced by the pituitary stalk

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6
Q

Name the 2 parts of the pit gland

A
  1. Adenohypophysis (Anterior pituitary)

2. Neurohypophysis (Posterior pituitary)

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7
Q

Name parts of ant. pit

A
  • pars distalis
  • pars tuberalis
  • pars intermedia
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8
Q

Name parts of pos. pit

A
  • pars nervosa

- infundibulum (neural stalk)

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9
Q

Where does the ant. pit dev from?

A
  • an upgrowth of ectoderm/ endoderm from the embryonic oral cavity (remnant of Rathke’s Pouch).
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10
Q

Where does post. pit dev from?

A
  • downgrowth from floor of the diencephalon in brain.
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11
Q

What does post. pit consist of?

A
  • axons of modified neurones, supported by a population of glial-like cells = pituicytes.
  • Cell bodies of these neurones lie in the supraoptic and paraventricular nuclei of the hypothalamus - Hormones syn in nuclei travel down axons
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12
Q

List functions of ADH/vasopressin

A
  • increases water retention in kidney.

- raises blood pressure by contracting vascular smooth muscle cells (at high concentrations).

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13
Q

List functions of oxytocin

A
  • contraction of smooth muscle cells, esp. of uterus during childbirth; and myoepithelial cells of mammary gland during lactation.
  • bonding both socially and sexually
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14
Q

What types of hormones are ADH and oxytocin and how many aa?

A
  • peptides

- 9

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15
Q

Where are ADH + oxytocin made and how are they released?

A
  • made in cell bodies of neurones (in hypothalamus) initially as a larger protein, subsequently cleaved to yield the hormone and a binding protein (neurophysin).
  • transported down axons to terminals
  • released from terminals into fenestrated capillaries on stimulation of the cell bodies in the hypothalamus
    – fenestrations allow plasma in blood to come into contact with cells lying underneath capillary endo.
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16
Q

What are Herring bodies?

A
  • accumulations of hormone within the axons

– secretory granules containing hormone

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17
Q

What is in the pars distalis region?

A

Cords of cuboidal/polygonal epithelial secretory cells clustered around large, fenestrated sinusoids.

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18
Q

What are the cells in the pars distalis region trad classed into and how do they stain?

A
  • Acidophils (stain pink/orange with H & E)
  • Basophils (stain blue with H & E)
  • Chromophobes (stain poorly)
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19
Q

List 2 types of acidophils and hormones they secrete

A
  • Somatotrophs - Growth Hormone

- Mammotrophs - Prolactin

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20
Q

List 3 types of basophils and hormones they secrete

A

Thyrotrophs - Thyroid Stim. Hormone (TSH)
Corticotrophs - Adrenocorticotrophic hormone (ACTH)
Gonadotrophs - Follicle Stim. Hormone (FSH), Luteinizing hormone (LH)

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21
Q

What is function of chromophobes?

A
  • either reserve cells/stem cells or resting cells that have lost their secretory granules
    – replace acidophils and basophils when they die
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22
Q

Describe characteristics of somatoptrophs in EM

A

packed with granules of moderate size

23
Q

Describe characteristics of thyrotrophs in EM

A

have smaller granules mostly at the periphery of the cell

24
Q

Describe characteristics of Gonadotrophs in EM

A

larger cells, variable sized granules

25
Q

Describe characteristics of Corticotrophs in EM

A
  • paler cytoplasm under e.m.

- sparse granules located at periphery.

26
Q

What is located in pars tuberalis?

A

Thin layer of cuboidal cells, mostly gonadotrophs.

27
Q

What is located in pars intermedia?

A
  • Cells (basophilic) secrete Melanocyte stimulating hormone
    – increases skin pigmentation, but physiological role in man is uncertain.
28
Q

Describe reg of secretion of ant. pit

A
  • regulated by neuroendocrine cells of the hypothalamus whose axons project to the median eminence.
  • discharge releasing hormone into capillaries of the pituitary portal vessels.
  • these in turn end in capillaries bathing the cells of the anterior pituitary
    – RH stim release of hormones from acidophils and basophils.
29
Q

What can happen as a result of trauma to the stalk?

A

loss of hormonal control of pit

30
Q

What hormones do the hypothalamic hormones stimulate release of?

A
  • Thyrotropin releasing hormone (TRH) – stim release of thyroid hormone
  • Gonadotropin releasing hormone (GnRH) – LH + FSH release
  • Growth hormone releasing hormone (GRH) - GH
  • Corticotropin releasing hormone (CRH) - ACH
31
Q

What hormones do the hypothalamic hormones inhib release of?

A
  • Somatostatin (blocks GH and TSH release)

- Dopamine (blocks prolactin release)

32
Q

Why is it a portal system?

A
  • Need less releasing hormone – short distance between hypo and pit – no need for circ around body before it arrives at destination
  • More immediate response
  • Can use the same hormone again locally elsewhere for other purposes. e.g. somatostatin from Islets of Langerhans blocks release of insulin and glucagon
33
Q

Describe anatomy of thyroid

A
  • 2 pear-shaped lateral lobes connected by a midline isthmus
  • intimately associated with the trachea
  • isthmus lies at level of 2nd-4th tracheal rings
  • isthmus may be joined to the hyoid bone by a fibrous cord, a remnant of the embryological thyroglossal duct
34
Q

Describe dev of thyroid

A

Arises from a diverticulum (outpouch) in floor of the primitive pharynx just caudal to the site of the future tongue
– thyroglossal duct
- opens at base of tongue as the foramen caecum
- connection to pharynx eventually lost, isolating the gland

35
Q

Describe cells of the thyroid

A
  • Thyroid epithelial cells are organized into follicles.
  • secrete thyroglobulin (large glycoprotein, mw 660Kd)
  • accumulates in the follicles as “colloid”
36
Q

Describe storage of iodine in thyroid

A
  • oxidized to Iodine

- covalently attached to the tyrosines of thyroglobulin within the lumen of the follicle

37
Q

Describe how iodine is released from thyroid

A
  • On stimulation by TSH (from the anterior pituitary)
  • follicular cells endocytose (Take up) the iodinated thyroglobulin
  • break it down in lysosomes
  • release the iodinated tyrosine derivatives as tetra- iodothyronine (thyroxine) (T4) or tri-iodothyronine (T3)
38
Q

Describe structure and location of Thyroid C cells/Parafollicular cells

A
  • scattered cells found within the follicular epithelium or as clusters between the follicles.
  • larger, more rounded than the follicle cells
39
Q

Describe function of Thyroid C cells/Parafollicular cells

A

secrete calcitonin (inhibits Ca++ mobilization) = release Ca from bone

40
Q

What is the neural crest?

A
  • all NS pop of cells derived from it

- migrate to thyroid during development

41
Q

Describe anatomy of parathyroid glands

A
  • 2 pairs of parathyroid glands, each about the size of a pea
  • Usually found on or embedded in the posterior border of the lateral lobes of the thyroid gland, but position is somewhat variable (esp. inferior parathyroids)
  • No functional significance in the association between thyroid and parathyroid glands
42
Q

Describe cells of parathyroid glands

A
  • Densely-packed, small Chief (or principal; P) cells arranged in irregular cords around blood vessels (C).
  • secrete parathyroid hormone (parathormone)
    stimulates calcium mobilization.
  • There is a second, minor population of larger, eosinophilic oxyphil cells (O), of unknown function (lack secretory granules)
43
Q

Describe anatomy of adrenal glands

A
  • Pyramidal (right) or crescent- shaped (left) bodies in contact with the upper poles of the kidneys
    Separated from kidneys by connective tissue but surrounded by the renal fascia.
44
Q

Describe development of adrenal glands

A
  • 2 distinct parts with different embryonic origins:
  • Cortex - derived from the coelomic epithelium (mesothelium) lining the posterior abdominal wall
  • Medulla - derived from an adjacent sympathetic ganglion, which was itself derived from neural crest
45
Q

Describe cells of adrenal cortex

A
  • Cells secrete steroids - have lots of smooth endoplasmic reticulum (SER) and lipid droplets (containing cholesterol) so appear pale and “frothy” in histological sections.
  • Cells are organized into 3 zones:-
    1) Zona glomerulosa (G)
    2) Zona fasciculata (F)
    3) Zona reticularis (R)
46
Q

Describe cells of zona glom

A
  • cells arranged in rounded clusters, surrounded by capillaries
  • secrete mineralocorticoids – mainly aldosterone (95%)
  • target : Kidney (Na+ retention by distal convoluted tubule) regulated by renin/anigiotensin system
47
Q

Describe cells of zona fasciculata

A
  • cells arranged in straight cords, running radially
  • secrete glucocorticoids – mainly cortisol (95%)
  • regulate : general glucose, lipid and protein metabolism
  • secretion regulated by ACTH
48
Q

Describe cells of Zona reticularis

A
  • cells arranged in irregular cords
  • secrete some glucocorticoids and small quantities of sex steroids (mostly weak androgens)
  • functionally insignificant (?)
49
Q

Describe structure of adrenal medulla

A
  • modified sympathetic ganglion
  • large, polyhedral cells arranged in clumps or cords
  • resemble “axon-less” ganglion cells
50
Q

Describe islets of Langerhans

A
  • Small, rounded clusters of cells,
  • 100-200 µm dia.,
  • embedded within the exocrine pancreas
  • The cells are smaller and more-lightly stained than the exocrine cells, and arranged in irregular cords around capillaries.
51
Q

List cells of IOL and what they secrete

A
  • A or alpha cells (~20%) secrete glucagon
  • B or beta cells (~70%) secrete insulin
  • D or delta cells (5-10%) secrete somatostatin
  • F or PP cells (1-2%) secrete pancreatic polypeptide
  • Other, minor cell types secrete vasoactive- intestinal peptide (VIP), substance P, motilin, serotonin, etc.
52
Q

Describe cells of Diffuse neuroendocrine system

A
  • Scattered cells found especially in the gut and respiratory system
  • Secrete amines or peptides with hormone-like (promote homeostasis) or neurotransmitter activity (promote sm contraction) e.g. gastrin, CCK, secretin, enteroglucagon, serotonin etc
  • Often secrete locally (paracrine)
53
Q

What do cells of Diffuse neuroendocrine system have ability to do and how?

A
  • Cells often have ability to take up and decarboxylate amines
    – Old name – APUD cells (amine precursor uptake and decarboxylation)
  • Possess synaptic vesicle-like structures or neurosecretory-type granules (dense core granules)
    – released by exocytosis in response to external stimuli
  • Derived from neural crest
  • Produce hormones in vesicles

Functional Anatomy & Embryology (8 decks)

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