9.
ENDOCRINE SYSTEM
"Functional unit of thyroid is thyroid follicle"
Synonyms
Hormone: to arouse activity Thyroid: Shield like
Endo: Within
Pineal gland: Epiphysis cerebri (or) third eye
Crine: Secretions
Adrenal: Named after secretion of adrenalin
Exo: Outside
Hypophysis: to grow
Diuretics: to hold water
Chromophobe: Fear to color
Chromophil: Affinity to color
Herring Bodies: Neuro secretory granules
Endocrine glands are ductless glands. They empty their
secretions into blood capillaries and so they are highly vascular. The
endocrine glands produce specific chemical substances known as hormones. They
circulate through vascular system and reach all the cells.
Special features of endocrine glands:
They are rich in capillaries.
•
Hormones released through capillaries.
Target organ specific Example: aldosterone acting on distal convoluted
tubule.
Each gland is unique in cytology.
The endocrine glands are:
1. Pituitary
2. Pineal gland
3. Thyroid gland
4. Parathyroid glands
5. Thymus
6. Supra renal glands
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7. Pancreas
8. Ovaries in female
9. Testis in male.
Anatomy for Allie
Hypothalamus
Posterior pituitary
Anterior pituitary
Thyroid
Adrenal cortex
Adrenal medulla
M
Oxytocin Vasopressini
Gonadotropin hormone (Gink
Oxytocin Vasopressin (A
Prolactin Follicle-stimur hormone (FS Luteinizing he
Triiodothyron Thyroxine (14)
Cortisol Androstene Dehydroepia
Epinephrine Norepinephis
Pancreas
Ovary
Testis
insulin
Estradiol Progesterone Testosterona
Inhibin
Testosterone
Estradiol Inhibin
PITUITARY GLAND (OR) HYPOPHYSIS
It is the master of endocrine symphony.
Situation: It is present in hypophyseal fossa on the upper surfie sphenoid. It is
covered by a circular fold of duramater called the sellae. It is
connected to hypothalamus by a stalk called infundibul
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Endocrine System
Shape and size:
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Transverse diameter is greater than vertical diameter 13mm to
15mm ovoid organ.
Lobe: anterior lobe (or)
adenohypophysis.
Posterior lobe (or) Neurohypophysis.
3
Subdivisions of anterior lobe:
a) Pars anterior.
b) Pars intermediate
c) Pars tuberalis.
pars
tuberalis
pars
nervosa
Subdivisions of posterior pituitary:
pars
a) Pars posterior
distalis
pars intermedia
b) Infundibulum
c) Median eminence
Relations:
of
Superiorly-optic chiasma
Inferiorly-body of sphenoid and sphenoidal air sinus.
On each side - cavernous sinus.
Blood supply:
Superior and inferior hypophyseal artery from internal carotid artery and veins
end in the cavernous sinus.
Microscopic structure:
The anterior lobe is made up of branching cords of epithelial cells. The cords are
separated by sinusoids. There are two types of cells, Chromophobe and
chromophils.the chromophils are of two types, they are acidophil and basophil.
The pars intermediate contains basophils and sinusoids. The pars nervosa contains
nerve fibers and cells contain known as pitucytes. The nerve fibers of
hypothalamo hypophyseal tract expanded called Herring bodies which
carry neurotransmittor from hypothalamus to the posterior lobe.
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Anatomy for Allied
Hormones Produced:
Anterior lobe:
a) Growth hormone or somatotropes - 50% of cells
act on skeletal
tissue.
b) Lactogenic hormone (prolactin) or mammotrophs -
20%, it act
gland to secrete milk.
c) Adrenal corticotrophic hormone (ACTH) 20%, act on
adrenal
medulla.
d) Thyroid stimulating harmone 5%, act on thyroid gland to
prod
T4, Which acts on nervous system and increase
metabolic rate,
e) Gonadotrophs 5%
ii.
i.
FSH: in female FSH act on the follicles of ovary to product and in male act on
semineferous tubules of testis to produ
LH: In female acting on corpus luteum to produce progeste male act on
interstitial cells to produce testosterone.
Pars intermediate:
Melanocyte stimulating hormone (MSH)
Pars posterior:
a) Antidieuritic hormone or vasopressin (ADH)
b) Oxytocin
The ADH acts on collecting ducts of kidney, deficiency of this home in
diabetes insipidus. Oxytocin in female act on uterus and pelvic jo
contraction of uterus for delivery of baby. In male it acts on vas deferent
muscle to produce ejaculation.
Applied anatomy:
Tumour of pituitary
Acromegaly in adults and gigantism in children.
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Scular
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Endocrine System
Pineal gland:
Situation: it is situated in the posterior wall of 3rd ventricle just
above the midbrain.
Shape: comma shaped.
Size: 8mm in length.
Structure: well developed in children.after puberty it is replaced by
connective tissue.as age advances calcified bodies appears known as
corpora arenacea (brain sand). It has thin capsule and subdivided by
septa into lobules. It contains epithelial and neuroglial cells. It secretes
melatonin.
Thyroid gland: it is the largest endocrine gland.
ogen
m.
epiglottis
-thyroid cartilage
(Adam's apple)
pharynx
nd in
-blood vessel
THYROID
GLAND
ults
luce
Goth
trachea (windpipe) PARATHYROID
GLANDS
Situation: It is situated in front and side of the neck opposite to C5, C6 and 7th
cervical and 1st thoracic vertebrae.
Shape:
II-Shaped, vertical limb corresponds to lobe .horizontal limb corresponds to Isthmus.
Lobe:
Right and left lobe connected by isthumus. The left lobe in the upper border presents
a small projection called pyramidal lobe. Fibro muscular band extending
between hyoid and pyramidal lobe called the levator glandulae thyroidae.
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Anatomy for A
Size:
Each lobe is 5cm length,3cm in width and 2cm in thickness, weig larger in female.
Features:
Each lobe has three surface, lateral,medial and posterior
surface, ist
the two lobes.
Relations:
Lateral surface- relations
Skin and superficial fascia.
Sternohyoid,sternothyroid and omohyoid and sterno
mastoid
Posterior surface:
Carotid sheath and its contents.
Medial surface:
Two tubes - oesophagus,trachea.
Two nerves - recurrent laryngeal and external laryngeal nerve.
Two muscles - cricothyroid, inferior constrictor of pharynx.
Isthumus: superficial - sternohyoid, sternothyroid and sternomaston
Deep: 2nd 3rd and 4th tracheal
rings.
Blood supply:
Superior thyroid artery.
Inferior thyroid artery
Thyroidea ima artery.
Veins:
Superior and middle thyroid vein end in internal jugular vein.infor end in
left brachio cephalic vein.
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and
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Endocrine System
Lymph vessels:
Lymph vessel end in pre tracheal and paratracheal and upper
deep cervical lymph
node.
Nerve supply:
Sympathetic: middle cervical sympathetic
ganglion.
Microscopic structures:
The gland has two capsule -outer false capsule derived from cervical fascia of neck
and true capsule derived from fibrous connective tissue of gland. The trabeculae
divide the gland into lobes and lobules. The functional unit of the gland is called
thyroid follicle. The follicles filled with colloid which is a gelatinous jelly like
substance. The colloid contain T3 and T4. TSH act on the follicle to produce
thyroid hormones. If ther is not enough iodide in the body, the TSH keep on
stimulating the follicle, the thyroid enlarge and produce goiture.
Development: endoderm of median thyroid
diverticulum.
Functions of thyroid hormones:
•
Regulation of metabolic rate of tissues.
It helps in the development of nervous system.
Hypothyroidism - cretinism in children and myxodema in adult.
Decrease mental and physical activity.
Calcitonin lowers the blood calcium.
Applied anatomy:
Enlargement of thyroid gland is called goiture.
Removal of thyroid gland is called
thyroidectomy.
PARATHYROID GLAND
Glands are two pairs. situated on the posterior surface of the thyroid
gland.
Shape and color: oval and orange yellow color.
Size: 6mm,4mm,3mm in thickness, weight 50mgs.
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Position:
Superior parathyroid is constant in
position.
Inferior parathyroid is variable in
position.
•
Sometime within the capsule.
.
Outside the capsule
Anatomy for
Within the gland.
Microscopic structure:
The gland is covered by a thin connective tissue capsule, delicate gland into
lobules. The cells are arranged as branching and ane
separated by sinusoids. There are two type of cells ie the
chief c cells. The chief cells secrete a hormones which increases the seru
Increase calcium reabsorption from the renal tubule.
Blood supply:
Inferior thyroid artery.
Veins end in inferior thyroid vein.
hormone is essential to life
Functions: it acts an osteoclast which break down bone and liber
hyposecreation result In neuro muse Nerve supply: middle
cervical sympathetic ganglion.
Applied anatomy:
Increased activity is called hyper parathyroidism. This lead to level. Decreased
activity called hypoparathyroidism. This leads then leads to
convulsion (tetany)
THYMUS
Thymus is a lymphoid organ situated in the superior mediastinu Weight: it is
15gms at birth 30gms at puberty and 10gms in adul Lobes: it
consists of two pyramidal lobe connected by areolar ( Blood
supply: inferior thyroid artery, veins end in inferior thym
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es the
Endocrine System
Nerve supply: inferior cervical sympathetic
ganglion.
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Structure: It has thin capsule its lobes are subdivided incompletely
into hexagonal lobules. It has outer cortex and inner medulla. The cells are
reticular cells, lymphocytes and macrophages. The cortex has dense
lymphoid tissue. Medulla has diffused lymphoid tissue, Hassle's corpuscles
and reticular cells.
Functions:
Secrete hormones called lymphopoitin. It stimulates the lymphoblast
division (i.e) lymphopoitin, lymphocytes and immunologically competent
thymocyte.
Suprarenal gland:
They are paired endocrine glands also known as adrenal
gland.
Situation:
Upper pole of the kidney in the posterior abdominal
wall.
Fords
yphill
Sevel.
Size: length -6cm
Breadth -2cm
MEDULLA
Thickness-1cm
CORTEX
Weight-5gms.
RIGHT
CUT SECTION OF ADRENAL GLAND
LEFT ADRENAL GLAND
ADRENAL
This
Right supra renal gland:
GLAND
Shape - triangular
Relation:
Anterior: right lobe of liver and IVC.
Posterior: diaphragm and right kidney.
ium
Jemia
Left supra renal gland:
Shape - semilunar in outline
Relation:
Anterior: upper part - stomach
lower part - pancreas
Posterior: upper part - diaphragm
lower part - left kidney
LEFT KIDNEY
RIGHT KIDNEY
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Anatomy for Al
Blood supply:
•
Superior supra renal artery-from the inferior phrenic
artery,
Middle supra renal artery-from the abdominal
aorta.
Inferior supra renal artery-from the renal
artery.
Veins: right supra renal veins end in inferior vena cava, left
supra
in left renal vein.
Lymphatic drainage:
Lumbar nodes: Lumph vessels end in para aortic lymph node. Nerve
supply:
Sympathetic fibers from T,, to L, segments. The fibers
are pre gan
the medulla.
Structure:
10
The gland is covered by thin connective tissue capsule. it consists of cortex and inner medulla.
The cortex is essential to life and has thr 1. Zona glomerulosa: contains the
looped collection of cells. 2. Zona fasciculate: consisting of parallel cords
of cells. 3. Zona reticularis: consisting of anastomosing cord of cells, The
medulla contains sympatho chromaffin cells.
Hormones:
Cortex:
1. Zona glomerulosa: secretes mineralocorticoids, aldosterone
convoluted tubule and regulate water and electrolyte balance
2. Zona fasciculate: secretes gluco corticoids
eg: cortisol and hydrocortisone act on every cell of the body and
Excess secretion decreases the immune function.
3. Zona reticularis: secretes sex hormones - androgen
(gonado
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Endocrine System
Medulla: secretes adrenallin and nor-adrenalin hormones.
Epinephrine act on sympathetic neurons. e.g increases heart rate.
Nor-epinephrine is a vasoconstrictor.
Applied anatomy:
Tumour of medulla causes hypertension, palpitation and excessive
sweating.
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Tumour of cortex gives rise to cushing's syndrome (hypo gonadism, obesity,
virulism and diabetes)
Pancreas:
The islets of Langerhans situated among the exocrine serous acini of
pancreas. They are more in the tail of pancreas.
Microscopic structure:
The islets are more or less spherical and closely related to sinusoid. There are two
types of cells. The alpha cells secrete glucagon and beta cells secrete insulin. "P-
cells" secrete pancreatic polypeptide. "D-cells" secrete somatostatin.
Ovary:
The ovary contains ovarian follicle. It secretes oestrogen before ovulation (i.e) in the first half
of menstrual cycle and the corpus luteum which secrete progesterone after ovulation.
Testis:
In the testis, in between the seminiferous tubule lies in the interstitial cells of Leydig. These
cells secrete testosterone hormones.
Gastroduodenal mucosa:
The endocrine cells are seen in the mucous membrane of stomach and small intestine which secrete
gastrin, secretin, cholicystin, kinin and prostaglandin.
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