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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
The capillaries of the adenohypophysis drain into the _______
pituitary veins | Pituitary veins carry the hormones of the pituitary gland into general circulation
26
The nerve supply to the pituitary is via the
hypothalamohypophyseal tract
27
What supports the secretory cells and blood sinusoids in all 3 parts of the adenohypophysis? (pars distalis, pars tuberalis, pars intermedia)
Reticular cells and fibers
28
Cells of the pars distalis form clumps or cords of cells. The cells may be classified as either
chromophils or chromophobes depending on their staining characteristics
29
Chromophils
-"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
Acidophils
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
Somatotropes (type of acidophil)
Most common type of acidophil | secrete the growth hormone somatotropin (STH)
32
Lactotropes (type of acidophil)
``` aka- mammotropes secrete prolactin (PRL) ```
33
Basophils
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
Corticotrope (type of basophil)
secrete adrenocorticotropic hormone (ACTH)
35
Thyrotropes (type of basophil)
secrete thryotropic hormone (thyroid stimulating hormone, TSH)
36
Gonadotropes (type of basophil)
secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
37
Chromophobes
form 50% of pars distal is Have colorless cytoplasm Majority are believed to be degranulated chromophils Some are reserve cells
38
Pars tuberalis consists of
glandular tissue around the infundibulum (infundibular stalk)
39
Pars tuberalis is formed by
Short cords of secretory cells, separated by sinusoids The cells are acidophils, basophils and chromophobes Gonadotropes are the most common type of cell
40
Pars intermedia
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
Control of hormone release by the adenohypophysis Releasing hormones are known for: Inhibiting hormone is known for:
Releasing hormones are known for: GH, TSH, ACTH, FSH/LH | Inhibiting hormone is known for: GH (somatostatin)
42
Releasing or inhibiting hormones originate in
the hypothalamus | They travel to the adenohypophysis via the hypophyseal portal system
43
The levels of releasing or inhibiting hormones is under the feedback control of
circulating hormone levels
44
Neurohypophysis (pars nervosa, infundibular stem, median eminence)
- all portions are histologically similar | - the parenchyma is formed by the unmyelinated axons of hypothalamohypophyseal tract
45
In the neurophyophysis, the nerve cell bodies of the axons are in the
supraoptic and paraventricular nuclei of the hypothalamus
46
In the neurophyophysis, the axons contain
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
Oxytocin
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
Antidiuretic hormone (ADH, vasopressin)
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
Oxytocin and ADH are bound to
carrier proteins in the axon | These carrier proteins are called neurophysins
50
The hormone/carrier protein complex accumulates in the ends of the axons to form homogenous
Herring bodies
51
Herring bodies are
- homogeneously staining spheres found in the tissue of the neurohypophysis - the hormone/carrier protein complex is released by exocytosis into the perivascular space
52
Pituicytes
supporting cells of the neurohypophysis; glial-like cells
53
Pathology of the Pituitary | Lesions of the hypothalamus that destroy ADH producing neurons cause
diabetes insipidus Characterized by excessive thirst and urine production Pituitary tumors can occur, but they are usually benign
54
Pineal Gland structure
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
Parenchyma of Pineal gland
formed by secretory cells in clumps or cords | Contains pineal concretions (corpora arenacea, brain sand)
56
Pineal concretions
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
Nerve supply to pineal gland
- 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
Secretory cells of pineal glands
Pinealocytes | Interstitial (glial) cells
59
Pinealocytes
- 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
Melatonin is released by pinealocytes in a _________ fashion
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
Interstitial (glial) cells
Supportive elements of the pineal | A form of astrocyte
62
Pineal tumors, pineolomas, that destroy the pineal parenchyma can result in
precocious puberty in children

Histology Exam 3 (7 decks)

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