Download Gross Morphology of the Endocrine Glands

Gross Morphology of the Endocrine Glands
A Pituitary Gland (Hypophysis Cerebri)
Hypo means below, and physis means
growth, so it is the gland that grows from
below because it is located below the brain.
It has an oval structure that’s located
beneath the hypothalamus and It attaches
to it by a stalk we call it (infundibulum; it
means funnel shaped).
If we go back to the first year, we divided
the brain into 3 parts (forebrain, midbrain
and hindbrain), the forebrain is composed of cerebrum and diencephalon (it means two
things hidden by the cerebrum) and the diencephalon consists of the thalamus (it means
the chamber) and below it we can see the hypothalamus. The main function of the
hypothalamus is the integration between the nervous system and the endocrine system.
The pituitary gland is known as the master endocrine gland because it influences the
activity of other endocrine glands in our body (by secreting hormones), and those
hormones are:
1. Thyroid stimulating hormones (TSH); it influence the activity of the thyroid gland.
2. Adrenocorticotropic hormone (ACTH); it influence the
activity of the adrenal gland.
3. Follicular stimulating hormone (FSH).
4. Luteinizing hormone (LH).
These two hormones
will influence the
activity of the gonads
(testis and ovaries).
However, to make it clear let’s imagine that the pituitary gland is the prime minister
(‫)رئيس الوزراء‬, thus it has a president who is the hypothalamus)‫ (رئيس الدولة‬, and so the
hypothalamus has the superiority over the endocrine system.
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; The location of pituitary gland
It is located in the cranial cavity within the Sella turcica
(Means the Turkish saddle) of the sphenoid
bone. It is made of three parts:
 The anterior part (tuberculum sellae); it
is the anterior horn of the saddle.
 Pituitary fossa or hypophyseal fossa where the
gland is located.
 Dorsum sellae; it is the back of the saddle.
In addition to these parts there is something we call it clinoid
processes (bed post ‫ )حواف السرير‬of the Sella turcica.
The Sella turcica looks like the bed where the pituitary gland is
sleeping, however the post of the bed will be these
clinoid processes (2 anterior and 2 posterior), they are
very important because they provide an attachment for
the sheet (‫ )الغطاء او اللحاف‬which covers the pituitary and
this sheet is a part from the dura matter we call it sellar diaphragm. (The sellar diaphragm
of dura which covers the pituitary should attach to these clinoid processes).
; Divisions of Pituitary Gland
The pituitary gland is made of two parts:
1. The anterior lobe (we call it adeno-hypo-physis):
 Adeno means gland so it is the glandular part of the
pituitary.
 It constitutes about 75% of the weight of the gland.
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2. The posterior lobe (we call it neuro-hypo-physis):
 It is more nervous in nature.
 It constitutes about 25% of the gland.
 It is a down growth from the hypothalamus, it does not secret hormones, but it
stores hormones that’s why it is very rich in axon terminals of nerve cells (more
than 10,000 neurons in the hypothalamus will send their axons to end up in the
posterior lobe).
So the hormones that are secreted from the hypothalamus will be transported by vesicles
down to the neurohypophysis to be stored.
; Development of Pituitary Gland
Adenohypophysis:
It is developed from ectodermal outgrowth or
invagination (we call this outgrowth Rathke’s
Pouch) in the roof of the primordial mouth
which we call it stomatodeum or stomodeum.
During the 3rd week of the embryological
development the ectodermal cells in the roof
of the stomodeum starts to invaginate
upward producing a pouch, this pouch is
called Rathke’s Pouch. As Rathke’s Pouch
develops upward towards the brain
(cranially), it elongates, and by the 5th week of
development the pouch will become
disconnected from the primordial mouth.
Once it is disconnected from the stomodeum it becomes like a small cyst (an ectodermal
covering and a space inside it), the ectodermal covering of this cyst especially the ones in
the anterior part will start to proliferate filling the space.
By the end of the 5th week and the beginning of the 6th week the space will be completely
filled so know it is not anymore a cyst, it is a sphere of cells.
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The anterior part where the anterior cells proliferate and occupy the space will become
the anterior part of the gland or pars anterior or pars distalis (since it is the distal part)
Sometimes, a remnant of the space (a small cleft) remains there, we call it Rathke’s cleft
(not always present), if it is present, it will demarcate the border between the anterior
ectodermal cells that proliferate and the posterior ectodermal cells of the cyst, these
posterior cells will become what’s known as pars intermedia (because it is located in the
middle between pars distalis and pars nervosa which is a part of the neurohypophysis).
As the ectodermal cells proliferate backward to fill the space, they also grow up upward
to cover the infundibulum (pituitary stalk),
once they cover it anterio-laterally we call
them pars tuberalis. So the
adenohypophysis will be divided into:
1. Pars anterior or distalis.
2. Pars intermedia.
3. Pars tuberalis.
However, pars tuberalis and pars distalis
have similar cells (the ectodermal cells from
the anterior part), while pars intermedia has the remnant cells of the posterior ectodermal
cells of the rathke’s cyst.
Neurohypophysis:
At the same period of time when the adenohypophysis develops, there will be a
downward growth from the hypothalamus that starts as a bud (we call it
neurohypophyseal bud), this bud will elongate also but this time downward instead of
upward and by the end of the 5th week it will elongate to become behind the rathke’s
cyst. However, this hypophyseal elongation is not separated from the hypothalamus, it
remains connected to the hypothalamus, so it will be divided (the neurohypophysis) into:
1. Pars nervosa (the nervous part).
2. The infundibulum or the pituitary stalk (the connection remains between the
posterior pituitary and the hypothalamus).
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; The functions of the pituitary gland
 The anterior pituitary: secrets several hormones that controls the activity of the other
endocrine glands (the first 4 hormones mentioned previously) and other three
hormones which are:
1. Somatotropin hormone (growth hormone); which is required during the
juvenile period for growth and during adult period for repair and regeneration
of tissues.
2. Prolactin hormone; stimulate the production of milk by mammary glands.
3. Melanocyte stimulating hormone: it stimulates the melanocyte to proliferate.
 The posterior part: it does not synthesize hormones it stores hormones which are:
1. Oxytocin.
2. ADH (antidiuretic hormone) or vasopressin.
This histological view shows you
the difference, here is the pars
nervosa totally separated part.
And we can see a demarcating line
here which demonstrate the cells
of pars intermedia.
Also, we can see here the cells of
pars distalis.
The cells of pars intermedia are the
ones that secrete the melanocyte
stimulating hormone, while the
cells of pars distalis will secrete the
remaining hormones.
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; Relations to Pituitary Gland
It is very important especially during doing any surgery
in the cranial base of the skull.
 Anteriorly: the tuberculum sellae and the
sphenoidal air sinus.
 Posteriorly: the dorsum sellae, basilar artery
and the pons.
 Superiorly: sellar diaphragm and the optic
nerve (2nd cranial nerve) or optic chiasma.
 Inferiorly: the hypophyseal fossa and the
sphenoidal air sinus.
 Laterally: cavernous sinus (very large
Any adenoma or adenocarcinoma
structure it contains cranial nerves III (oculomotor),
occurs in the pituitary gland, as it
IV (trochlear), VI (abducent), two divisions of the
enlarges, it will start to penetrate
trigeminal nerve (V) which are ophthalmic and
into the cavernous sinus, which
maxillary and internal carotid artery). In addition to
become a very serious condition.
the cavernous sinus on each side the two cavernae
(one on the left and one on the right) are
The part of dura that surrounds
connected to each other by small veins (anterior to
the cerebrum we call it tentorium
the pituitary and posterior to it) those are called the
cerebelli.
inter-cavernous sinuses they are very Important
because they are the drainage site of the veins that draining the pituitary gland.
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; The vasculature of the pituitary gland
In the pituitary gland we have something
unique called the hypophyseal portal
system.
In portal systems in general, the blood will
flow from one capillary network through a
vein to a second capillary network, and
then it will drain into the venous
circulation, so the portal vein is always
located between two capillary networks.
In the hypophyseal portal system the
arteries that supply the adenohypophysis
(anterior lobe) will receive the blood supply
from the Superior hypophyseal arteries
coming from the internal carotid artery, we call them superior because they go superior
to the pituitary (they actually go to the hypothalamus), and in the hypothalamus they will
form the first capillary network, we call it the first hypophyseal plexus, in this plexus the
blood will drain from the hypothalamus down through the portal veins, these portal veins
will go into the adenohypophysis (anterior surface of the pituitary), then they will form
the second plexus we call it the secondary hypophyseal plexus, and from there they will
continue as the anterior hypophyseal veins that will go and drain into the anterior intercavernous sinus.
This portal system is only associated with the anterior pituitary gland because there
is an influence from the hypothalamus on the pituitary so this will permit the
hypothalamic hormones (from hypothalamus) to act immediately on the anterior
Pituitary cells before being diluted or destroyed in the systemic circulation. One
example is the thyroid releasing hormone secreted from hypothalamus that goes to
the first plexus then through the portal veins to the second plexus in the anterior
pituitary gland, then they will bind to its receptors on the adenohypophyseal cells
to stimulate them to secrete thyroid stimulating hormone, this hormone will go
through the anterior hypophyseal veins to the circulation.
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In the posterior lobe because its main function is storage and it is connected directly to
the hypothalamus, we don’t need portal circulation, because of that, the arteries will go
directly from below forming what we call the inferior hypophyseal arteries (branch from
internal carotid), then they will form a plexus that’s called the infundibular plexus, this
plexus will drain posteriorly onto the posterior inter-cavernous sinus.
A Adrenal (Suprarenal) Glands
 It is a yellowish primary retroperitoneal organ that
is located on the upper part of both kidneys.
 Made of two parts:
1. Cortex (the outer part)
 Constitutes about 85% of the gland (so it’s the
major part)
 Divided into 3 zones (from outside to inside):
 Zona glomerulosa (contains spheres of cells)
This zone secretes hormones that control the menials in the body, these hormones are
mineralocorticoids as aldosterone.
 Zona fasciculata (contains bundles or cords of cells)
This zone secretes hormones that control glucose metabolism we called them
glucocorticoids as cortisol.
Androgens in the adult period in
 Zona reticularis (contains network of cells)
females are responsible for
This zone secretes hormones that control the growth of
testosterone production, while
the gonads in the pre-pubertal period we call them
in males they are responsible for
androgens.
production of some androgens
that are responsible for the
2. Medulla (inner part)
masculinity.
Constitutes about 15 % of the gland.
It is considered as a modified sympathetic ganglion area so it originates from the neural
crest (the nervous system).
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Its main function is hormones secretion, which are:
 Epinephrine.
 Norepinephrine.
These hormones are responsible for the sympathetic
response (fight or flight).
The fight or flight response is also called the five Fs response,
they are related to the age and gender and they include:
 Fight (seen in males)
 Flight (seen in males)
 Freeze (seen in children)
 Fright (seen in females)
 Faint (seen in females)
; Coverage & Attachments of Suprarenal Glands
The adrenal glands are covered by the renal
fascia (the deep fascia covering the kidneys).
In this figure, we can see the layers covering
the kidneys, which are pararenal fat from the
outside then we have the renal fascia and
finally deep perirenal fat layer (between the
renal fascia and the kidney), so the suprarenal
gland here is covered by the renal fascia and
this fascia is responsible for the attachment of
the adrenal glands posteriorly to the
diaphragm (to the crura of the diaphragm), so
this is the major attachment.
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Actually the adrenal glands are held in their position
by their attachment to the crura of the diaphragm not
to the kidneys, they are separated from the kidneys
by the perirenal fat.
Left Suprarenal Gland



Crescent in shape (semilunar)
More medial
Larger
The relations:
 Anteriorly: the pancreas, the lesser sac
and the stomach.
 Posteriorly: the left crus of the
diaphragm.
; Vasculature of the Suprarenal Glands
 Arterial Blood Supply, The blood supply to
the adrenal glands is from 3 main
arteries:
Right Suprarenal Gland



Pyramidal in shape (as a cap)
More apical (at the superior pole of the
kidney)
Smaller
The relations:
 Anterio-laterally: the liver.
 Anterio-medially: inferior vena cava (we
have to retrace the IVC to see the gland)
 Posteriorly: the right crus of the
diaphragm.
1. Superior suprarenal arteries
 6-8 in numbers
 Come from the inferior phrenic
artery, which is come from the
abdominal aorta.
2. Middle suprarenal arteries
 Come from the lateral aspect of the
abdominal aorta.
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 At the level of L1 (it is adjacent to the superior mesenteric artery not the celiac
trunk, so in this picture the position is wrong). Important
3. Inferior suprarenal artery
 Come from the renal arteries
These arteries before they reach to the adrenal glands they
will branch to multiple branches, sometimes we can find more
than 50 branch entering into the adrenal gland (there is no
hilum for the arteries).
The hilum of the gland
can only be distinguished
for the veins and nerves.
 Venous Drainage, We have only
one vein for each gland which are:
1. Right suprarenal vein
 Shorter.
 Drains directly to the IVC.
2. Left suprarenal vein
 Longer.
 Drains to the left renal vein
and goes with it to the IVC.
If we look carefully to the figure we will see that the
left suprarenal vein joins with the left inferior phrenic
vein, so we should be careful when you want to ligate
the left suprarenal vein, we should ligate above the
junction (closer to the gland not to the renal vein).
 Lymph Drainage
The lymph flows along with the kidneys into the para-aortic
lymph nodes then to the cisterna chyli then to the thoracic
duct finally to the venous circulation.
Transformers Team A
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