Download ANATOMICAL FEATURES OF THE ENDOCRINE GLANDS

ANATOMICAL FEATURES OF THE ENDOCRINE GLANDS
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LEARNING OBJECTIVES
At the end of this lecture, students should be able to,
Understand the anatomy of the endocrine glands.
Define the relations of these endocrine glands.
Know Blood vessels supplying these endocrine glands.
Know Nerve supply of these endocrine glands.
ENDOCRINE GLANDS
Control many body functions by releasing special chemical substances
into the blood called hormones
Act on target organs elsewhere in body
Control and coordinate widespread processes, i.e. homeostasis,
reproduction, growth and development, metabolism and response to
stress.
THE ENDOCRINE SYSTEM
Consists of several glands located in various parts of the body i.e.
Hypothalamus
Pituitary
Thyroid
Parathyroid
Adrenal
Kidneys
Pancreatic Islets
Ovaries
Testes
PITUITARY GLAND
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Lies in the hypophyseal fossa.
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Covered by diaphragma sellae
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On each side is a flange of dura matter separating the gland from the
cavernous sinus.
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Pia and arachnoid blend with the capsule of the gland.
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Below the fossa lies the body of sphenoid containing sphenoidal air
sinuses.
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Pitutary stalk slops down wards and forwards to the perforation in the
diaphragma connecting posterior part of gland to the hypothalamus.
Optic chaisma lies above the diaphragma sellae anterosuperior to the
pitutary stalk.
STRUCTURE OF PITUTARY GLAND
Consists of anterior and posterior lobe.
Anterior lobe or adenohypophysis develops
from ectodermal sacule (rathke‟s pouch) of
stomodeum and consists of pars anterior
(distalis), pars tuberalis and rudimentary
pars intermedia.
Posterior lobe or neurohypophysis, develops
from neuroectodermal growth from the floor
of third ventricle and consists of pars posterior, infundabular stalk and
median eminence.
PARS ANTERIOR
Accounts for 75% of gland and is highly vascular and consists of 50%
chromophobe, 35% acidophils and15% basophils. Acidophils secrete
growth hormones and prolactin.
Basophils produce ACTH, TSH, FSH, LH.
Pars tuberalis is small extension of the pars anterior along the pitutary
stalk. Its function not known.
Pars intermedia consists of colloid filled vesicles and secrete MSH. Its
cells contain endorphins.
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PARS POSTERIOR
Contains about 100,000 unmyelinated
nerve fibers. Cell bodies in paraventricular
nuclei secrete oxytocin.
Cell bodies in supraoptic nuclei secrete
antidiuretic hormone.
Hormones are secreted from
neurohypophysis.
BLOOD SUPPLY
Single inferior and several superior hypophyseal arteries arise from
internal carotid arteries.
Hypophyseal portal venous system forms, connecting hypothalamus
and pitutary and carry hormones and releasing factors from pitutary.
THYROID GLAND
About 25g in weight and is enclosed by pretracheal fascia has two
symmetrical lobes united by isthmus.
Isthmus joins anterior surface of the lobes at their lower part, lies in
front 2nd, 3rd and 4th tracheal rings.
Pretracheal fascia is here fixed between them (It moves gland up and
down during swallowing).
On upper border of isthmus superior and inferior thyroid arteries form
anastomosis. Tributaries of inferior thyroid veins emerge from its lower
border.
Lobes are pear shaped.
Having narrow upper pole and broad lower pole.
Triangular in cross section and possessing lateral, medial and posterior
surface
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LOBES OF THYROID GLAND
Extends from oblique line on thyroid cartilage up to 6th tracheal ring
sternothyroid and sternohyoid muscles cover lateral surface.
Lower part of pharynx and upper esophagus lie behind.
Posterior surface is related with medial part of common carotid artery.
More laterally is internal jugular vein and parathyroid glands.
RECURRENT LARYNGEAL NERVES
Recurrent laryngeal nerves approach medial surface of gland from
below and lie in or in front of groove between trachea and esophagus.
Left nerve recurves around the arch of aorta in superior mediastinum.
Right nerve recurves around right subclavian at the root of the neck,
nerve either passes medial and lateral or through suspensory ligament
of berry.
PYRAMIDAL LOBE
Upward projection from isthmus generally to the left of midline.
It is caudal end of thyroglossal duct.
It may be attached to the inferior border of the hyoid bone by fibrous
tissue named levator glandulae thyroidae.
Aberrant thyroid tissue may be found, near hyoid bone, in the tongue in
the superior mediastinum and any where along the path of descent of
thyroglossal duct.
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SUPERIOR THYROID ARTERY
It is first branch from anterior aspect of external carotid artery.
Pierces pretracheal fascia.
Reaches the summit of upper pole in front of external laryngeal nerve.
Divides in to anterior and posterior branch.
Anterior branch runs down the isthmus and posterior branch runs down
back of lobe and anastomosis with an ascending branch of inferior
thyroid artery.
Be ligated at upper pole or anterior or posterior branch be ligated in
order to avoid damage to external laryngeal nerve.
Inferior thyroid artery arises from thyrocervical trunk.
Arches upward medially and behind carotid sheath and then loops
down to the lower pole of gland.
Divides out side pretracheal fascia.
Branches pierce fascia separately Recurrent laryngeal nerve always
behind pretracheal fascia.
Ligating it lateral to gland or its branches separately can safeguard
nerve.
Branches are ascending cervical artery and smaller pharyngeal,
esophageal, laryngeal and tracheal branches.
Thyroidea ima artery present in 3% of individuals. Enters lower pole of
isthmus.
.Arises from brachiocephalic trunk, arch of aorta or right common
carotid artery.
Venous drainage of thyroid gland
Superior thyroid veins follow superior thyroid artery and opens into
internal jugular vein or facial vein.
Middle thyroid vein crosses internal carotid vein.
Inferior thyroid veins drain mainly in to brachiocephalic vein
Lymphatic drainage Mainly to deep cervical nodes.
A few pass to prelaryangeal, pretracheal and paratracheal nodes.
And few drain directly into thoracic duct.
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PARATHYROID GLAND
Are small and lie behind the lobes of thyroid gland.
Superior parathyroid glands
More constant in position.
Usually within the thyroid‟s pretracheal facial capsule.
Lie at the middle of the back of the thyroid lobe.
At level with first tracheal ring above the inferior thyroid
artery
INFERIOR PARATHYROID GLAND
Is less constant in position.
Usually with in pretracheal facial sheath behind lower pole may be
gland it self or outside facial sheath, in the neck or in superior or
posterior mediastinum.
Not necessary at same level on each side.
Are brownish yellow and thyroid is deep red.
Blood supply of parathyroid
Inferior thyroid artery.
Or anastomosis between superior and inferior thyroid arteries.
Minute veins joins thyroid veins.
Parathyroid hormone (PTH)
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Stimulates Ca2+ release from bone
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Promotes intestinal absorption and renal tubular reabsorption of
calcium
Underactivity
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Decrease serum Ca2+
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Hypocalcemic tetany
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Seizures
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Laryngospasm.
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Overactivity
Increased serum Ca2+
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Pathological fractures
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Hypertension
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Renal stones
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Altered mental status
“Bones, stones, hypertones, abdominal moans”
ADRENAL GLAND
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Among most important and vital endocrine organ
Small bilateral, yellowish and retroperitoneal organ
Lies just above kidney in gerota‟s fascia.
Right adrenal is triangular, related to upper pole Right kidney
Left adrenal is crescent shaped, related to upper and medial part Left
kidney
Size :Right is 3 – 6 cm long and left one is 0.9 – 3.6 cm. Width is 2-3
cm. Weight is 3-5 gm. approximately.
Adrenal cortex consists of three distinct zones
Zona Glomerulosa. Small cells with intermediate
number of lipid inclusion.
Zona Fasiculata. large foamy cells secondary to
lipid inclusion - 75% of cortex.
Zona Reticularis. Consists of compact
cytoplasm and few lipid inclusions.
Adrenal cortex produces
Glucocorticoids (Zona Fasiculata)
Mineralocorticoids (Zona Glomerulosa)
Adrenal androgens (Zona Reticularis)
Adrenal medulla produces
Epinephrine (adrenaline)
Norepinephrine (noradrenaline)
Help increase in cardiac output, vascular
resistance and mediate stress response
All are absolutely required for life
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FUNCTIONS
Aldosterone helps in Na reabsorption & potassium excretion &
preventing dehydration
Cortisol stimulate protein breakdown, inhibition of tissue response in
injury & antagonism to action of insulin
Androgens helps in early development of male sex organ in childhood
VASCULAR SUPPLY
Blood to adrenal supplied by, Inferior phrenic artery (superiorly), aorta
(medially) renal artery (inferiorly)
Rt. adrenal : Superior and inferior suprarenal arteries.
Lt. adrenal : Middle & inferior suprarenal arteries
VENOUS DRAINAGE
Right Adrenal. Drained to IVC via suprarenal vein
Left Adrenal. Drained into left suprarenal vein or
directly to IVC
Lymphatic drainage. Drained to Para-aortic and Para- caval lymph
nodes
PANCREAS
Gland with both exocrine and endocrine functions is 6-10 inch in length
and 60-100 gram in weight.
Location:
Retro-peritoneal, at the level of 2nd lumbar vertebral.
Extends obliquely towards left.
Parts of pancreas:
Head, neck, body and tail
Endodermal in origin.
Develops from ventral and dorsal pancreatic buds. Ventral bud rotates
posteriorly and becomes the uncinate process and inferior part of head
of pancreas
Dorsal bud becomes superior part of head, neck, body and tail
Ventral bud duct fuses with dorsal bud duct to become main pancreatic
duct (Wirsung)
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Head of pancreas
Includes uncinate process
Flattened 2 – 3 cm thick
In the „C‟ shaped concavity of duodenum.
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Neck of pancreas
2.5 cm in length
Superior border relates to the pylorus
Superior mesenteric vessels emerge from the inferior border
Posteriorly, SMV and splenic vein confluence to form portal vein
Body of pancreas
Elongated.
Anterior surface, separated from stomach by lesser sac.
Posterior surface, related to aorta, Lt. adrenal gland, Lt. renal vessels
and upper 1/3rd of Lt. kidney
Splenic vein runs embedded in the post. surface closer to the superior
border
Inferior surface is covered by transverse mesocolon
Tail of pancreas
Narrow, short segment
Lies at the level of the 12th thoracic vertebra
Ends within the splenic hilum.
Anteriorly, related to splenic flexure of colon
May be injured during splenectomy.
PANCREATIC DUCT
Main duct (Wirsung) runs the entire length of pancreas and joins CBD
at the ampulla of Vater
2 – 4 mm in diameter, drains up to 20 secondary branches
Ductal pressure is 15 – 30 mm Hg (vs. 7 – 17 in CBD) thus preventing
reflux and damage to pancreatic duct
Lesser duct (Santorini) drains superior portion of head and empties
separately into 2nd portion of duodenum
ARTERIAL SUPPLY
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Celiac 
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Superior pancreaticoduodenal artery which divides into anterior and
posterior branches
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SMA  Inferior pancreaticoduodenal artery which divides into anterior
and posterior branches Anterior and posterior collateral arcade
between the superior and inferior PDA supply head
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Body and tail supplied by splenic artery by about 10 branches
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Three big branches from splenic are
Dorsal pancreatic artery
Pancreatica Magna (midportion of body)
Caudal pancreatic artery (tail)
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VENOUS DRAINAGE OF PANCREAS
Follows arterial supply
Anterior and posterior arcades drain head and the body
Splenic vein drains the body and tail
Major drainage areas are
Suprapancreatic PV
Retropancreatic PV
Splenic vein
Infrapancreatic SMV
Ultimately, into portal vein
Lymphatic drainage
Rich periacinar network that drain into 5 nodal groups
Superior nodes
Anterior nodes
Inferior nodes
Posterior PD nodes
Splenic nodes
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INNERVATION OF PANCREAS
Sympathetic fibers from the splanchnic nerves
Parasympathetic fibers from the vagus
Both give rise to intrapancreatic periacinar plexuses
Parasympathetic fibers stimulate both exocrine and endocrine
secretion
Sympathetic fibers have a predominantly inhibitory effect
HISTOLOGY-ENDOCRINE PANCREAS
Accounts for only 2% of the pancreatic mass
Nests of cells - islets of Langerhans
Four major cell types
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Alpha (A) cells secrete glucagon
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Beta (B) cells secrete insulin
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Delta (D) cells secrete somatostatin
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F cells secrete pancreatic polypeptide
B cells are centrally located within the islet
and constitute 70% of the islet mass
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INSULIN
Synthesized in the B cells of the islets of Langerhans
80% of the islet cell mass must be surgically removed before diabetes
becomes clinically apparent
Proinsulin, is transported from the endoplasmic reticulum to the Golgi
complex where it is packaged into granules and cleaved into insulin
and a residual connecting peptide, or C peptide
Major stimulants
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Glucose, amino acids, glucagon, GIP, CCK, sulfonylurea
compounds, β-Sympathetic fibers
Major inhibitors
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somatostatin, amylin, pancreastatin, α-sympathetic fibers
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Glucagon
Secreted by the A cells of the islet
Glucagon elevates blood glucose levels through the stimulation of
glycogenolysis and gluconeogenesis
Major stimulants
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Aminoacids, Cholinergic fibers, β-Sympathetic fibers
Major inhibitors
Glucose, insulin, somatostatin, α-sympathetic fibers
Somatostatin
Secreted by the D cells of the islet
Inhibits the release of growth hormone
Inhibits the release of almost all peptide hormones
Inhibits gastric, pancreatic, and biliary secretion
Used to treat both endocrine and exocrine disorders
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PINEAL GLAND
Located within the Diencephalon
Melatonin
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Inhibits ovarian hormones
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May regulate the body‟s internal clock
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HYPOTHALAMUS
Produces several releasing and inhibiting factors that stimulate or
inhibit anterior pituitary‟s secretion of hormones.
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Produces hormones that are stored in and released from posterior
pituitary
HYPOTHALAMUS
Also responsible for:
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Regulation of water balance
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Esophageal swallowing
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Body temperature regulation (shivering)
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Food/water intake (appetite)
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Sleep-wake cycle
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Autonomic functions
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OVARIES
Located in the abdominal cavity adjacent to the uterus
Under the control of LH and FSH from the anterior pituitary
Produce ovum for reproduction
Produce hormones
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estrogen
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progesterone
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Functions include sexual development and preparation of the
uterus for implantation of the egg
OVARIES
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Estrogen
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Development of female secondary sexual characteristics
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Development of endometrium
Progesterone
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Promotes conditions required for pregnancy
Stabilization of endometrium
TESTES
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Located in the scrotum
Controlled by anterior pituitary hormones FSH and LH
Produce sperm for reproduction
Produce testosterone –
promotes male growth and masculinization
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promotes development and maintenance of male sexual
characteristics
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