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endocrine system anatomy.pptx for BSN Generic

 The endocrine system includes the
endocrine glands and their hormones
 The function of the endocrine system is to
secrete hormones into the bloodstream.
 Hormone: A Chemical messenger which
targets a specific group of cells, in order to
cause that group of cells do some activity or
stop doing an activity.

 Exocrine glands release their secretions into
ducts, or tubes
 Liver Bile released into the gallbladder, then
through a duct into the small intestine
 Pancreas releases pancreatic juice into the small
intestine via a duct
 Endocrine Glands are called ductless glands
 Release hormones directly into the bloodstream
 Blood transports hormones throughout the body
 Each hormone acts on only a certain kind of tissue
called its target tissue

 Anatomical Position and Relations
 The pituitary gland is a pea-sized oval
structure, suspended from the
underside of the brain by the pituitary
stalk (known as the infundibulum). It
sits within a small depression in the
sphenoid bone, known as the sella
turcica (‘’Turkish saddle’’).
 The superior surface of the gland is
covered by a reflection of the dura
mater – the diaphragma sellae. This
membrane has a central opening which
allows passage of the infundibulum.

 Anatomically, the pituitary gland is a ‘’two-
in-one’’ structure consisting of the anterior
pituitary and the posterior pituitary. These
parts have different embryonic origins and
function very differently.

 Anterior Lobe
 The anterior lobe (adenohypophysis) is derived
from an outpouching of the roof of the pharynx,
called Rathke’s pouch. It is composed of
glandular epithelium and secretes a number of
hormones. The lobe can be further divided into
three parts:
 Pars anterior – the largest part, responsible for
hormone secretion.
 Pars intermedia – a thin epithelial layer that
separates the pars anterior from the posterior
lobe.
 Pars tuberalis – an upwards extension of the pars
anterior that surrounds the anterolateral aspect
of the infundibulum.

 The release of hormones is under the control
of the hypothalamus, which communicates
with the gland via neurotransmitters
secreted into the hypophyseal portal
vessels. These vessels ensure that the
hypothalamic hormones remain
concentrated, rather than being diluted in
the systemic circulation.

 Posterior Lobe
 The posterior lobe (neurohypophysis) consists
of nervous tissue.
 Upon stimulation, the posterior lobe secretes
two hormones – ADH (responsible for control
of blood osmolarity), and oxytocin (involved
in parturition and milk secretion

 The vasculature of the pituitary gland is
complex and unique. Whilst the anterior lobe
and posterior lobe have the same venous
drainage (anterior and posterior hypophyseal
veins), they have an individual arterial
supply:

 Anterior Pituitary
 The anterior pituitary gland receives arterial
supply from the superior hypophyseal
artery (a branch of the internal carotid
artery).

 Posterior Pituitary
 The infundibulum and posterior pituitary
gland receive a rich blood supply from many
arteries. Of these, the major vessels are the
superior hypophyseal artery, infundibular
artery and inferior hypophyseal artery.

 The thyroid gland is an endocrine structure
located in the neck. It plays a key role in
regulating the metabolic rate of the body.

 The thyroid gland is located in the
anterior neck and spans the C5-T1
vertebrae. It consists of two lobes
(left and right), which are
connected by a central isthmus
anteriorly – this produces a
butterfly-shape appearance.
 The lobes of the thyroid gland are
wrapped around the cricoid
cartilage and superior rings of
the trachea. The gland is located
within the visceral compartment
of the neck (along with the
trachea, oesophagus and pharynx).

 The thyroid gland is closely
associated with numerous other
structures in the anterior neck:
 Anteriorly – infrahyoid muscles,
namely the sternothyroid, superior
belly of the omohyoid and
sternohyoid
 Laterally – carotid sheath,
containing the common carotid
artey, internal jugular vein and
vagus nerve
 Medially –
 Organs – larynx, pharynx, trachea and
oesophagus
 Nerves – external laryngeal and
recurrent laryngeal

 The arterial supply to the thyroid
gland is via two main arteries:
 Superior thyroid artery
 Inferior thyroid artery
 In a small proportion of people
(around 10%) there is an
additional artery present –
the thyroid ima artery supplies
the anterior surface and isthmus
of the thyroid gland.

 Venous Drainage
 Venous drainage is carried by the superior,
middle, and inferior thyroid veins, which
form a venous plexus around the thyroid
gland.
 The superior and middle veins drain into the
internal jugular vein and the inferior empties
into the brachiocephalic vein.

 Innervation
 The thyroid gland is innervated by branches
derived from the sympathetic trunk.
 These nerves do not control the secretory
function of the gland – the release of thyroid
hormones is regulated by the pituitary gland.
 Lymphatic Drainage
 The lymphatic drainage of the thyroid is to
the paratracheal and deep cervical nodes.

 The parathyroid glands are endocrine glands
located in the anterior neck.
 They are responsible for the production
of parathyroid hormone (PTH), which acts
to increase the level of serum calcium.

 The parathyroid glands are usually located
on the posterior aspect of the thyroid gland.
They are flattened and oval in shape –.
 Most individuals have four parathyroid
glands, although variation in number (from
two to six) is common:
 Superior parathyroid glands (x2)
 Inferior parathyroid glands (x2)

 The vascular supply is similar to that of
the thyroid gland.
 Arterial supply is chiefly via the inferior
thyroid artery (as this artery supplies the
posterior aspect of the thyroid gland – where
the parathyroids are located
 Venous drainage is into
the superior, middle, and inferior thyroid
veins.

 Lymphatics
 The lymphatic drainage from
the parathyroid glands is to
the paratracheal and deep
cervical nodes.
 Nerves
 The parathyroid glands have
an extensive supply of
sympathetic nerves derived
from thyroid branches of the
cervical ganglia.

 The pineal gland is a small endocrine gland
located within the brain. Its main secretion
is melatonin, which regulates the circadian
rhythm of the body.

 The pineal gland is small glandular body,
approximately 6mm long. It is shaped like a
pine cone, from which its name is derived.
There are two types of cells present within
the gland:
 Pinealocytes – hormone secreting cells.
 Glial cells – supporting cells.

 The pineal gland is a midline structure,
located between the two cerebral
hemispheres. It is attached by a stalk to the
posterior wall of third ventricle

 The arterial supply to the pineal gland is
profuse, second only to the kidney.
The posterior choroidal arteries are the
main supply; they are a set of 10 branches
that arise from the posterior cerebral artery.
 Venous drainage is via the internal cerebral
veins.

 The adrenal (or suprarenal)
glands are paired endocrine
glands situated over the medial
aspect of the upper poles of
each kidney.
 They secrete catecholamines
harmones directly into blood.

 The adrenal glands are located in the
posterior abdomen, between the
superomedial kidney and the diaphragm.
They are retroperitoneal, with parietal
peritoneum covering their anterior surface
only.
 The right gland is pyramidal in shape,
contrasting with the semi-lunar shape of the
left gland.

 Perinephric (or renal) fascia encloses the
adrenal glands and the kidneys. This fascia
attaches the glands to the crura of the
diaphragm. They are separated from the
kidneys by the perirenal fat.
 The adrenal glands sit in close proximity to
many other structures in the abdomen

 The adrenal glands
consist of an outer
connective
tissue capsule,
a cortex and
a medulla.
 Veins and lymphatics
leave each gland via
the hilum, but
arteries and nerves
enter the glands at
numerous sites.

 The outer cortex and
inner medulla are the
functional portions of
the gland.
 Cortex –
 Medulla –
 The cortex and medulla
synthesise different
hormones.

 Cortex
 The cortex is yellowish in colour
.Functionally, the cortex can be divided
into three regions (superficial to deep):
 Zona glomerulosa – produces and
secretes mineralocorticoids such as
aldosterone.
 Zona fasciculata – produces and secretes
corticosteroids such as cortisol. It also
secretes a small amount of androgens.
 Zona reticularis – produces and secretes
androgens such
as dehydroepiandrosterone (DHES). It
also secretes a small amount of
corticosteroids.

 Medulla
 The medulla lies in the centre
of the gland, and is dark brown
in colour. It
contains chromaffin cells,
which secrete catecholamines
(such as adrenaline) into the
bloodstream in response to
stress.
 These hormones produce a
‘flight-or-fight‘ response.
Chromaffin cells also secrete
enkephalins which function in
pain control.

 The adrenal glands have
a rich blood supply via
three main arteries:
 Superior adrenal
artery –
 Middle adrenal artery
 Inferior adrenal artery
 Right and left adrenal
veins drain the glands.
The right adrenal vein
drains into the inferior
vena cava, whereas the
left adrenal vein drains
into the left renal vein.

INNERVATION
 The adrenal glands are innervated by the coeliac
plexus and greater splanchnic nerves.
 Sympathetic innervation to the adrenal medulla
is via myelinated pre-synaptic fibres, mainly
from the T10 to L1 spinal cord segments.
LYMPHATICS
 Lymph drainage is to the lumbar lymph nodes by
adrenal lymphatic vessels. These vessels
originate from two lymphatic plexuses – one
deep to the capsule, and the other in the
medulla.

 The pancreas is an abdominal glandular
organ with both digestive (exocrine)
and hormonal (endocrine) functions.

 The pancreas is an oblong-shaped organ
positioned at the level of the transpyloric
plane (L1). With the exception of the tail of
the pancreas, it is a retroperitoneal organ,
located deep within the upper abdomen in
the epigastrium and left hypochondrium
regions.

 Stomach the stomach and pylorus lie
anterior and to the pancreas.
 Duodenum – The “C” shaped duodenum
curves around and outlines the head of
the pancreas. The first part of the
duodenum lies anteriorly whereas the
second part of the duodenum including
the ampulla of Vater lies laterally to the
right of the pancreatic head
 Transverse mesocolon – Attaches to the
anterior surface of the pancreas
 Common bile duct – Descends behind
the head of the pancreas before opening
into the second part of the duodenum
alongside the major pancreatic duct
through the major duodenal papilla
 Spleen – located posteriorly and
laterally.

 Head – the widest part of the
pancreas.
 Uncinate process – a projection
arising from the lower part of the
head and extending medially to lie
beneath the body of the pancreas.
 Neck – located between the head
and the body of the pancreas.
 Body – centrally located, crossing
the midline of the human body to
lie behind the stomach
 Tail – the left end of the pancreas
that lies within close proximity to
the hilum of the spleen..

The exocrine pancreas is classified as a lobulated, serous
gland which produces digestive enzyme precursors.
It is composed of approximately one million ‘berry-like’
clusters of cells called acini, connected by short intercalated
ducts.
 The intercalated ducts unite with those draining adjacent
lobules and drain into a network of intralobular collecting
ducts, which in turn drain into the main pancreatic duct.
 The pancreatic duct runs the length of the pancreas and
unites with the common bile duct, forming
the hepatopancreatic ampulla of Vater. This structure
then opens into the duodenum via the major duodenal
papilla.
 Secretions into the duodenum are controlled by a muscular
valve – the sphincter of Oddi. It surrounds the ampulla of
Vater, acting as a valve.

 The pancreas is supplied by
the pancreatic branches of
the splenic artery. The head is
additionally supplied by
the superior and inferior
pancreaticoduodenal arteries
 Venous drainage of the head of the
pancreas is into the superior
mesenteric branches of
the hepatic portal vein. The
pancreatic veins draining the rest
of the pancreas do so via
the splenic vein.

 The pancreas is drained by lymphatic vessels
that follow the arterial supply. They empty
into the pancreaticosplenal nodes and the
pyloric nodes, which in turn drain into the
superior mesenteric and coeliac lymph
nodes.

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