Transcript 04-Lecture of endocrine system (Updated 28 April)

Endocrine glands (cells)
Hormone secreting cells or glands.
May be in a form of scattered cells as
enteroendocrine cells of GIT.OR in a form of
gland as pituitary and thyroid glands.
Endocrine glands have cells that arranged in
columns or cords separated by fenestrated
blood capillaries EXCEPT thyroid gland in which
cells are arranged to form follicles.
Hypophysis (pituitary gland)
•Development of Hypophysis
(pituitary gland)
Hypophsis (pituitary gland)
It develops from 2 different tissues:
1-Ectodermal epithelial tissue: of the roof of the
developing mouth---Rathke’s pouch giving
Adenohypophsis (Anterior pituitary).
2-Ectodermal neural tissue of dienchephalon---Neurohypophsis (Posterior pituitary).
Parts of hypophsis
1-Adenohypophysis
2Neurohypophysis
a-Pars distalis.
a-Pars nervosa.
b-Pars tuberalis.
b-Infundibulum.
c-Pars intermedia.
c- Median eminence.
Blood supply and control of secretion
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Superior hypophseal arteries supply the pars tuberalis
and the infundibulum and give primary capillary plexus
in the median eminence.
Inferior arteries supply the pars nervosa and send few
branches to the ant. lobe
The hypophseal portal system of veins delivers
neurosecretory hormones from the primary capillary
plexus of the median eminence to the secondary
capillary plexus of the pars distalis.
These hypothalamic hormones stimulate or inhibit the
secretion of cells of pars distalis.
Pars nervosa (Neurohypophsis)
Does not contain secretory cells.
• Does not contain cell bodies of neurons.
• Is rich in unmyelinated nerve axons.
• Is rich in fenestrated
blood capillaries.
• Contains Herring bodies
that contain vasopressin (ADH)
& oxytocin H. that are
secreted by hypothalamus (.
• Contains supporting glial cells called pituicytes.
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Adenohypophysis (anterior
pituitary)
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Pars intermedia : Contains cysts full of colloid
&lined with cuboidal epith.It may contain cords of
basophils that secrete MSH.
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Pars tuberalis :
It surrounds the hypopheseal
• (neural)stalk of neurohypophysis
Most of its cells are basophilic
gonadotropic cells that arranged
in cords separated by blood
capillaries and portal system
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Pars distalis :
1-Chromophobes: Have no affinity to stain.
Are small pale cells.
Undifferentiated cells.
2-Chromophils: Have an affinity to the stain.
They are 2 groups:
I-Acidophils include a- Somatotrophs that secrete
somatotropin or growth H
b-Mammotrophs that secrete
mammotropin or prolactin H.
II-Basophils include a-Thyrotrophs that secrete TSH.
b-Corticotrophs that secrete ACTH.
c-Gonadotrophs that secrete 2 types
of hormones:
-FSH in females it stimulates
follicular maturation. In males it stimulate spermatogenesis.
-LH in females it stimulates
ovulation. In males it stimulate Lyedig cells(interstitial cells) to
secrete testosterone.
Anterior pituitary (Adenohypophsis)
Medical application
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Pituitary benign tumors.
Effects of pituitary Hormones on the mammary
gland.
Prolactin---stimulate milk formation.
Oxytocin---stimulate milk ejection
Parathyroid glands
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They are 4 glands on the post.of thyroid gland.
Each gland has its capsule and thin septae.
The parenchyma is formed of chief cells,
oxyphil cells, blood capillaries and adipose
tissue (in adults).
Chief cells are slightly eosinophilic, rich in rER
and secrete parathyroid hormone ( bl.calcium).
Oxyphil cells are, arranged in groups or
clusters, deep eosinophilic (rich in mitochondria
and glycogen) and of unknown function
(inactivated chief cells).
Thyroid &
parathyroid glands
Parathyroid gland
Post. lobe of
pituitary
Ant. lobe of
pituitary
Parathyroid gland
Thyroid gland
Is covered by CT.capsule that
sends septae to divide it into lobules.
 Its parenchyma is formed of
follicles that are separated
by reticular fibers, parafollicular
cells and fenestrated blood capillaries.
 The follicles are formed of follicular cells (squamous to
columnar) & contain colloid.
 Follicular cells are basophilic, and rich in RER,
mitochondria and apically located lysosomes.
 Parafollicular cells secrete calcitonin (decreases
Bl.Calcium level).
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Thyroid follicles and parafollicular
cells (clear cells)
Follicular cells
Parafollicularcell
Suprarenal (adrenal) glands
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It has a thick capsule that sends septae.
Suprarenal cortex (80% of the gland) produces
mineralocorticoids, glucocorticoids (cortisol and
corticosterone), and androgens.
The cortex is regulated by ACTH of ant. Pituitary and
angiotensin II.
Suprarenal medulla produces epinephrine and
norepinephrine and is regulated by the sympathetic
nervous system.
The cortex is rich in fenestrated (without diaphragm)
sinusoidal capillaries.
The medulla receives a dual blood supply: a. from
cortical arteries and b. from cortical capillary beds.
Adrenal gland
It is formed of:
I. Cortex that is composed of:
A-Zona glomerulosa.
B-Zona fasiculata.
C-Zona reticularis.
II.Medulla
Adrenal gland
Adrenal cortex: zona
glomerulosa
*Is formed of cords and clusters
of small columnar cells that are
rich in SER and mitochondria.
*Produces Aldosterone hormone
that affect renal distal tubules.
Adrenal cortex: zona fasiculata
(spongiocytes)
*It is the intermediate and the
largest layer of the cortex.
*It is formed of columns of large
polyhedral cells that are separated
by longitudinal sinusoidal capillaries.
*It cells are rich in lipids so they
appear empty (spongiocytes).
*Its cells are rich in mitochondria
(tubular cristae),SER and lipofucin
pigment.
*Its cells secrete glucocoticoids.
*It is regulated by ACTH of
pituitary.
Adrenal cortex:zona
reticularis.
*It is the
innermost layer
of adrenal cortex.
*It is formed of
anastomosing
cords of deep
acidophilic cells.
*Its cells contains
few lipofucin and
lipid droplets.
*The cells
secrete
androgens.
Medulla of
adrenal gland
*It the central portion of the
adrenal gland.
*It is completely invested with
adrenal cortex (not separated
from it by CT. septa)
*It is formed of:
1. Chromaffin cells that contains
granules of catecholamine as
that of sympathetic NS.(They
produce epinephrine and
norepinephrine). They stain deep
brown with chromic salts.
2. Sympathetic ganglion cells
scattered in CT. Relay on
chromaffin cells.
Adrenal gland
Thyroid gland