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Histology Exam 3 > 21- Endocrine System 1 > Flashcards

21- Endocrine System 1 Flashcards

1
Q

General structure of endocrine glands

A
  • ductless: the secretory units secrete into the interstitum
  • The secretory product (hormone) often diffuses into the blood or lymph system for dispersal
  • The secretory units are formed by epithelial cells in the form of cords, clumps, plates or follicles (thyroid)
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2
Q

The secretary units are surrounded by a

A

basal lamina at the periphery

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3
Q

The secretory cells secrete

A

hormones, which act on target organs or cells

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4
Q

Hormones can act (control) in one of three ways

A
  1. Endocrine control is the classic description in which the hormone passes into the circulatory system and is transported to the cells of the target organ
  2. Paracrine control involves release of the hormone into the connective tissue interstitum. The target cells are cells found in close proximity to the hormone secreting cell.
  3. Autocrine control occurs when the secreted hormone acts on receptors within the secretory cell itself
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5
Q

The endocrine glands have an abundant _________

A

blood supply, for uptake of the hormone product

Usually in the form of fenestrated capillaries or sinusoids

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6
Q

A connective tissue framework, usually consisting of _______________ supports the secretory units

A

in the form of a capsule and trabeculae or septa

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7
Q

Hormones generally fall into 1 of 3 classes of compounds

A
  1. small peptides, proteins, and polypeptides
  2. steroids (usually require attachment to a transport protein)
  3. amino acid and arachadonic acid analogues and derivatives
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8
Q

When the hormone reaches its target cell, the hormone either

A

binds with a cell surface receptor or an intracellular receptor

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9
Q

Control of hormone secretion is by

A

direct feedback, which can be negative or positive
OR
release in response to a stimulus, either physical or chemical

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10
Q

Types of endocrine glands

A
  1. discrete or classical endocrine glands are the hypophysis (pituitary), thyroid, parathyroid, adrenal and pineal glands
  2. glands with mixed endocrine and exocrine functions include the pancreas, liver, kidney and gonads
  3. the diffuse neuroendocrine system consists of APUD (amine precursor uptake and decarboxylation) cells, which are scattered unicellular glands
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11
Q

Structure of the Hypophysis (Pituitary Gland)

“The Master Gland”

A

Pituitary is a pea sized gland, 0.5 gram in adults

Larger in women (it can reach 1 g or more in multiparous women)

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12
Q

Location of the Pituitary Gland

A

Localized in the sella turnica (bony depression) in the middle cranial fossa of the skull
Suspended from the hypothalamus of the brain by a stalk called the infundibulum (has neural and vascular connections to the brain)

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13
Q

Pituitary is formed by 2 distinct tissues

A

adenohypophysis and neurohypophysis

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14
Q

Adenohypophysis develops from the glandular tissue of the

A

ectoderm of Rathke’s cleft (pouch), which arises from the lining of the primitive oral cavity
It’s composed of secretory cells that are epithelial in nature

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15
Q

3 parts of Adenohypophysis

A
  1. pars distalis- 75% of the pituitary gland
  2. pars tuberalis- forms a collar of tissue around the infundibulum
  3. pars intermedia- portion lying posterior to Rathke’s cleft, which is the slit-like remnant of the lumen of Rathke’s pouch
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16
Q

Neurohypophysis is composed of

A

neural tissue derived from the neuroectoderm of the primitive diencephalon of the brain

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17
Q

2 parts of neurohypophysis

A
  1. Pars nervosa (infundibular process) lies directly posterior to the pars intermedia of the adenohyphysis
  2. Infundibulum which is directly connected tot he median eminence of the overlying hypothalamus
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18
Q

Some authors consider the neurohypophysis to have 3 parts

A

pars nervosa
median eminence
infundibular stalk (stem)

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19
Q

2 lobes of pituitary gland

A

Anterior lobe- consists of the parts distalis and the pars tuberalis
Posterior lobe- consists of the parts intermedia and pars nervosa

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20
Q

The pituitary has a capsule of dense

A

connective tissue
-a delicate framework of reticular cells and fibers is suspended from the capsule and supports the secretory elements and blood vessels

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21
Q

Blood supply to adenohypophysis

A

no direct arterial supply except to the pars tuberalis

-It shares a common capillary bed with the neurohypophysis

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22
Q

Bloody supply to neurohypophysis

A

inferior hypophyseal arteries supply primarily the pars nervosa
superior hypophyseal arteries supply the pars tuberalis, median eminence and the infundibulum.

These arteries branch into a primary capillary plexus in the parts tuberalis, median eminence and the infundibulum

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23
Q

The primary capillary plexus forms

A

small hypophyseal portal veins that drain into the adenohypophysis

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24
Q

The veins that lie between the primary and secondary capillary plexus if the neurohypophysis and adenohypophysis form the ____________

A

hypophyseal portal system

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25
Q

The capillaries of the adenohypophysis drain into the _______

A

pituitary veins

Pituitary veins carry the hormones of the pituitary gland into general circulation

26
Q

The nerve supply to the pituitary is via the

A

hypothalamohypophyseal tract

27
Q

What supports the secretory cells and blood sinusoids in all 3 parts of the adenohypophysis? (pars distalis, pars tuberalis, pars intermedia)

A

Reticular cells and fibers

28
Q

Cells of the pars distalis form clumps or cords of cells. The cells may be classified as either

A

chromophils or chromophobes depending on their staining characteristics

29
Q

Chromophils

A

-“Color loving”
-Granules in the cytoplasm of the cells stain with dyes, can be Acidiphils or Basophils
-Contain secretory granules 100-350 nm ini diameter
(granule size is specific for each cell type, individual granules are not visible with the light microscope)

30
Q

Acidophils

A

Alpha cells
Comprise 40% of cells in the pars distalis
Granules in the cytoplasm stain pink with H&E
2 types of acidophils- somatotropes and lactotropes
(can’t tell them apart with light microscope)

31
Q

Somatotropes (type of acidophil)

A

Most common type of acidophil

secrete the growth hormone somatotropin (STH)

32
Q

Lactotropes (type of acidophil)

A 
aka- mammotropes
secrete prolactin (PRL)
33
Q

Basophils

A

Beta cells
Comprise 10% of cells in pars distalis
Granules in cytoplasm stain blue with H&E
3 types of basophils- corticotropes, thyrotropes, gonadotropes
(can’t tell them apart with light microscope)

34
Q

Corticotrope (type of basophil)

A

secrete adrenocorticotropic hormone (ACTH)

35
Q

Thyrotropes (type of basophil)

A

secrete thryotropic hormone (thyroid stimulating hormone, TSH)

36
Q

Gonadotropes (type of basophil)

A

secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

37
Q

Chromophobes

A

form 50% of pars distal is
Have colorless cytoplasm
Majority are believed to be degranulated chromophils
Some are reserve cells

38
Q

Pars tuberalis consists of

A

glandular tissue around the infundibulum (infundibular stalk)

39
Q

Pars tuberalis is formed by

A

Short cords of secretory cells, separated by sinusoids
The cells are acidophils, basophils and chromophobes
Gonadotropes are the most common type of cell

40
Q

Pars intermedia

A

lies immediately adjacent to Rathke’s cleft
It is rudimentary in man, forming only 2% of the tissue of the hypophysis
Has basophils, chromophobes, and colloid-filled cysts
Secretory cells are assumed the be corticotropes
Other basophils in the pars intermedia secrete intermedin (melanocyte-stimulating hormone in some species, role of intermedin in humans is unknown)

41
Q

Control of hormone release by the adenohypophysis
Releasing hormones are known for:
Inhibiting hormone is known for:

A

Releasing hormones are known for: GH, TSH, ACTH, FSH/LH

Inhibiting hormone is known for: GH (somatostatin)

42
Q

Releasing or inhibiting hormones originate in

A

the hypothalamus

They travel to the adenohypophysis via the hypophyseal portal system

43
Q

The levels of releasing or inhibiting hormones is under the feedback control of

A

circulating hormone levels

44
Q

Neurohypophysis (pars nervosa, infundibular stem, median eminence)

A
  • all portions are histologically similar

- the parenchyma is formed by the unmyelinated axons of hypothalamohypophyseal tract

45
Q

In the neurophyophysis, the nerve cell bodies of the axons are in the

A

supraoptic and paraventricular nuclei of the hypothalamus

46
Q

In the neurophyophysis, the axons contain

A

hormones produced by the neurons of the supraoptic and paraventricular nuclei. The hormones produced by these neurons are oxytocin and anti-diuretic hormone (ADH)

47
Q

Oxytocin

A
  1. Causes contraction of the myoepithelial cells surrounding the alveoli of the mammary gland (results in milk release from the mammary gland)
  2. Oxytocin is released in response to the physical stimulus of the infant’s suckling
  3. Oxytocin also causes contraction of the smooth muscle of the uterus during orgasm, menstruation, and parturition (birth)
48
Q

Antidiuretic hormone (ADH, vasopressin)

A
  1. ADH acts on the collecting ducts and distal convoluted tubules of the kidney to increase their permeability to water by increasing water resorption from the kidney filtrate
  2. decreases perspiration
  3. increases blood pressure by smooth muscle contraction
  4. ADH release is controlled by neurons of the supraoptic and paraventricular nuclei acting as osmoreceptors
49
Q

Oxytocin and ADH are bound to

A

carrier proteins in the axon

These carrier proteins are called neurophysins

50
Q

The hormone/carrier protein complex accumulates in the ends of the axons to form homogenous

A

Herring bodies

51
Q

Herring bodies are

A
  • homogeneously staining spheres found in the tissue of the neurohypophysis
  • the hormone/carrier protein complex is released by exocytosis into the perivascular space
52
Q

Pituicytes

A

supporting cells of the neurohypophysis; glial-like cells

53
Q

Pathology of the Pituitary

Lesions of the hypothalamus that destroy ADH producing neurons cause

A

diabetes insipidus
Characterized by excessive thirst and urine production
Pituitary tumors can occur, but they are usually benign

54
Q

Pineal Gland structure

A

cone-shaped gland found in the brain
Located in the diencephalon adjacent to the third ventricle
It’s attached to the brain via the pineal stalk
Has connective tissue capsule

55
Q

Parenchyma of Pineal gland

A

formed by secretory cells in clumps or cords

Contains pineal concretions (corpora arenacea, brain sand)

56
Q

Pineal concretions

A

accumulations of calcium phosphates and carbonates
They increase in amount with age
function is unknown
they can serve as a radio-opaque marker for the midline in an x-ray and CT scans

57
Q

Nerve supply to pineal gland

A
  • Innervated by post-ganglionic sympathetic fibers arising in the superior cervical ganglion
  • Innervation is directly connected to the retina of the eye, so the metabolism of the gland is related to the phasing of the light:dark cycle
  • In lower mammals, the metabolism of the gland is related to seasonal reproduction
58
Q

Secretory cells of pineal glands

A

Pinealocytes

Interstitial (glial) cells

59
Q

Pinealocytes

A
  • found in clumps or cords
  • active cell with many organelles
  • secrete the presumptive hormone, melatonin
  • Tumors of pineal parenchymal cells in children ersult in precocious puberty
60
Q

Melatonin is released by pinealocytes in a _________ fashion

A

circadian fashion, with blood serum levels higher during the dark phase
Function of melatonin in man is unknown, but it is antigonadotropic in lower mammals

61
Q

Interstitial (glial) cells

A

Supportive elements of the pineal

A form of astrocyte

62
Q

Pineal tumors, pineolomas, that destroy the pineal parenchyma can result in

A

precocious puberty in children

Histology Exam 3 (7 decks)

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