Download Endocrine

14.0, 15.0 ENDOCRINE SYSTEM
Endocrine I: Hypothalamus, pituitary and pineal
Upon completion of this lecture, students will be able to:
a) Define and use properly the following words: Endocrine organ, Ductless glands , Highly
vascular, Hypophysis cerebri (pituitary), Adenohypophysis, pars distalis, pars tuberalis,
pars intermedia, Neurohypophysis, pars nervosa (neural lobe) infundibulum, infundibular
stalk, median eminence, Adenohypophysis, Pars distalis, Chromophobe, Acidophil,
somatotropes (alpha), lactotopes (epsilon), Basophil, thyrotropes (beta), gonadotropes
(delta), corticotropes, Pars tuberalis, Pars intermedia, Melanotropes, Hypothalmoadenohypophysial system, Neuroendocrine cells, Hypophysial portal system,
Neurohypophysis, Pituicytes, Axons unmyelinated, Herring bodies, Hypothalamic nuclei,
Supraoptic, Paraventricular, Neurophysins, Epiphysis cerebri (pineal), Pinealocytes,
Astrocytes, Corpora arenacea.
b) Describe and associate basic structure/function for the following: all structures listed
above.
c) Identify by microscopy: Acidophil, Adenohypophysis, Basophil, Chromophobe, Corpora
arenacea, Corticotropes, Ductless glands, Herring bodies, hypophysial portal system,
Infundibular stalk, infundibulum, Median eminence, Neural lobe, Neurohypohysis, pars
distalis, pars intermedia, pars nervosa, pars tuberalis, Pituitary.
Endocrine II: Thyroid, parathyroid, adrenal
Upon completion of this lecture, students will be able to:
a) Define and use properly the following words: Thyroid gland, Colloid, Follicular lining cells
(chief cells), Parafollicular cells (C cells), Transport iodine, Thyroglobulin, Calcitonin,
Parathyroid gland, Principal cells (chief cells), Oxyphil cell, Parathyroid hormone,
Suprarenal gland (adrenal gland), Capsule, Stroma, Adrenal Cortex , Zona glomerulosa
or Zona arcuata, Zona fasiculata, Zona reticularis, Mineralocorticoids, Glucocorticoids,
Androgen, Estrogen , Adrenal medulla, Chromaffin cells, Ganglion cells.
b) Describe and associate basic structure/function for the following: all structures listed
above.
c) Identify by microscopy: Adrenal cortex, Adrenal gland (suprarenal), Adrenal medulla,
capsule, Chief cells, chromaffin cells, Colloid, Cords, cortex, follicle, Follicular lining cells
(chief cells), Ganglion cells, Medulla, Medullary endocrine cells (chromaffin cells),
Oxyphil cell, Parafollicular cell (C-cells), Parathyroid gland, Polyhedral, Principal cells
(chief cells), Thyroid, Zona fasiculata, zona fasiculata, zona glomerulosa, Zona arcuata,
zona intermedia, Zona reticularis.
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Endocrine System
I.
GENERAL CHARACTERISTICS OF ENDOCRINE ORGANS
A. Ductless glands
1. formed by invagination of epithelium which separates and sinks below the
surface
2. an exocrine glands maintains connection with the surface through a duct system
B. Highly vascular
1. secretions are released into and transported by the vascular system
C. Distinct organ, part of an organ, or a single cell
1. ex. hypophysis cerebri (pituitary) or pancreatic islets
D. Cell arrangement
1. single cell
2. cluster
3. cord
4. follicle
E. Produce and sometimes store hormones
II.
HYPOPHYSIS CEREBRI (PITUITARY)
A. Organization
1. Adenohypophysis
a. pars distalis
b. pars tuberalis
c. pars intermedia
i. derived from oral ectoderm
2. Neurohypophysis
a. pars nervosa (neural lobe) infundibulum
i. infundibular stalk
ii. median eminence
b. derived from neural ectoderm
B. Adenohypophysis
1. Pars distalis
a. Chromophobe
i. 50%
ii. does not stain well
iii. not secretory
b. Acidophil
i. 40%
ii. somatotropes (alpha) - somatotropin
iii. lactotopes (epsilon) - prolactin > mammary gland, crop
c. Basophil
i. 10%
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ii. thyrotropes (beta) - thyrotropin > thyroid follicles
iii. gonadotropes (delta) - LH and FSH > testes and ovaries
iv. corticotropes - ACTH, beta-lipotropin
2. Pars tuberalis
a. function uncertain
b. weakly basophilic cuboidal cells
3. Pars intermedia
a. melanotropes- melanocyte stim. hormone & ACTH
b. target: skin and adrenal
4. Hypothalmo-adenohypophysial system
a. neuroendocrine cells of the hypothalamus
b. factors from these cells stimulate or inhibit the release of pituitary
hormones
c. hypophysial portal system
i. rostral hypophyseal aa. forms capillary bed in upper pit. stalk
(median eminence) and hypothalamus
ii. pick up releasing factors from hypothalamic neurons and carry to
pars distalis through portal venules
iii. form second capillary bed in pars distalis where factors are
released
iv. caudal hypophyseal a. - single capillary bed in pars nervosa; not a
portal system
C. Neurohypophysis
-- ventral evagination of nervous tissue of the hypothalamus
1. Regions
a. Median eminence
b. Infundibular stalk
c. Neural lobe (Pars nervosa)
2. Cells and cell processes
a. Pituicytes
i. modified astrocytes; form framework among axons and capillaries
b. Axons
i. unmyelinated
ii. contain neurosecretory granules (Herring bodies)
iii. storage form of the hormone secretions of the neuron in the
hypothalamic nuclei
iv.
c. Hypothalamohypophyseal tract
i. hypothalamic nuclei - where neuron cell bodies are located
1. Supraoptic
a. vasopressin (ADH)
b. target: kidney
2. Paraventricular
a. oxytocin
b. target: repro organs, milk let down, stimulate
myometrium
3. Neurophysins
a. carrier proteins that transport hormones
ii. axons which extend into the neural lobe
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1. release stored hormones into endocrine capillaries
III.
EPIPHYSIS CEREBRI (PINEAL)
-- light sensitive organ responsible for the production of melatonin and serotonin
-- role in sexual maturation, circadian rhythms, thermoregulation
A. Capsule
1. is pia mater
B. Pinealocytes
1. large cells with round open nucleus
C. Astrocytes
1. interdigitated between pinealocytes and vessels
D. Corpora arenacea
1. intercellular Ca deposits
2. associated with increasing age but not decreased glandular function
IV.
THYROID
A. Structure
1. Capsule
a. dense irregular ct
2. Parenchymal arrangement
a. cells arranged in follicles
b. hollow sphere of variable size
c. surrounded by dense capillary network
3. Colloid
a. gel-like material in center of follicle
b. storage product of follicular epithelium
c. acidophilic
d. vacuolation at the periphery indicates active follicle
4. Cells
a. Follicular lining cells (chief cells)
i. vary from squamous to columnar
ii. acidophilic with a basal nucleus and microvilli
b.
Parafollicular cells (light cells, C cells)
i. outside follicular epithelium; do not reach lumen
ii. pale staining
iii. secrete calcitonin
B. Synthesis and storage of thyroid hormone
1. collect and transport iodine
a. uptake of circulating iodide
b. iodide concentrated and oxidized to iodine
2. synthesize thyroglobulin
a. polypeptides synthesized and glycosylated to form thyroglobulin
b. thyroglobulin transported into the colloid
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3. tyrosine residues of thyroglobulin iodinated in colloid
a. stored thyroglobulin contains mono- and di-iodotyrosine which are the
building blocks of T 3 and T4
C. Mobilization of thyroid hormone
1. Regulation
a. regulated by TSH
2. Changes in the morphology of the follicle
a. lg. apical pseudopods form> increased intracellular colloid droplets and
phagolysosomes
b. colloid becomes foamy at edge
3. Secretion of T 3 (triiodothyronine) and T 4 (tetraiodothyronine, thyroxine)
a. Thyroglobulin phagocytosed
b. Secondary lysosome formed
c. T 3 and T 4 released across cell membrane
D. Effects of thyroid hormone
1. involves energy metabolism, growth and differentiation
E. Calcitonin
1. Secretion
a. parafollicular cells produce
b. released in response to high blood Ca; causes blood Ca decrease
2. Action
a. inhibits osteoclasts and stimulates osteoblasts
b. inhibits Ca absorption from gut
V.
PARATHYROID GLAND
-- external - cranial pole of thyroid; 3rd pharyngeal pouch
-- internal (not present in birds, pigs) - caudal pole of thyroid-embedded within; 4th
pharyngeal pouch
A. Structure
1. Capsule
a. dense irregular connective tissue
2. Parenchymal arrangement
a. cords or clusters of cells
3. Cells
a. Principal cells (chief cells)
i. lt and dk cells are different physiol. state of same cell
1. lt - inactive
a. most common cell type
b. large acidophlic cell with light cytoplasm;
c. few organelles
2. dk - active
a. dark cytoplasm with many active organelles
b. Oxyphil cell
i. in ox, horse, man
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ii. lg cells with pale acidophilic cytoplasm
iii. derived from chief cell
iv. function unknown
c. Transitional cell - characteristics of both cell types
B. Parathyroid hormone
1. produced by principal cells
2. increases blood calcium, absorption of ca from intestine, resorption from bones
3. decreases Ca loss from urine
VI.
SUPRARENAL GLAND (ADRENAL GLAND)
A. Structure
1. Capsule
a. dense fibrous ct.
2. Stroma
a. ct trabecula and fine stroma
3. Blood supply
a. capsular arteries branch to supply cortex and then empty into medulla
b. medullary arterioles supply the medulla directly
c. a fresh blood supply plus one rich in adrenocortisteroids to stimulate
adrenaline production in the medulla
4. Cortex
a. Cellular arrangement
i. parenchyma in cords
b. Zones
i. Zona glomerulosa or Zona arcuata - cuboidal to columnar cells
arranged in glomeruli or curved cords
ii. Zona fasiculata - cuboidal cells with foamy cytoplasm; lg amount
of lipids
iii. Zona reticularis - less foamy than fasiculata
c. TEM
i.
prominent SER related to steroid synthesis
d. Function of adrenal cortex
i. Mineralocorticoids
a. aldosterone-control Na retention in the kidney (DCT and
CD)
b. z. glomerulosa
ii. Glucocorticoid production
a. cortisol and corticosterone-gluconeogenesis; release of
fatty acids; anti-inflammatory
b. z. fasciculata and some from z. reticularis
iii. Androgen and estrogen
a. zona reticularis and some in zona fasiculata
iv. Regulation
a. zona glomerulosa regulated by renin-angiotensin system
b. zona fasiculata and zona reticularis by ACTH of pit. And
CRH of hypothalamus
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5. Adrenal medulla
a. Cells
i. Medullary endocrine cells (chromaffin cells)
a. modified postganglionic sympathetic neurons
b. contain membrane-bounded granules
c. produce epinephrine and norepinephrine
ii. Ganglion cells
a. sympathetic ganglion
b. randomly scattered; difficult to find
c. synapse with glandular cells and control their secretion
VII.
ENDOCRINE PANCREAS
A. Pancreatic islets (Islets of Langerhans)
---randomly scattered throughout the organ
---clusters of cells with extensive vascular supply
---connected by gap jcts. at EM level
1. A cell (alpha)
a. secrete glucagons
b. elevates blood glucose
c. dense granules with halo TEM
2. B cell (beta)
a. secrete insulin
b. decreases blood glucose
c. halos around less dense granule with TEM; granules may be crystalloid in
man, dog, cat
3. D cells (delta)
a. produce somatostatin
b. somatostatin release of somatotrophin by pituitary; inhibits release of
insulin and glucagons
4. Other cells of the pancreatic islets
a. pancreatic polypeptide cells (F cells)
i. releases pancreatic polypeptide hormone which inhibits
exocrine secretions of the pancreas
b. G cells
i. releases gastrin which stimulates production of gastric acid by
parietal cells in stomach
VIII.
AMINE PRECURSOR UPTAKE DERIVATIVE (APUD) CELLS
---single endocrine cells scattered around the body
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