Endocrine system anatomy
Describe the pancreas position?
A soft lobulated organ that lies slightly oblique on the posterior abdominal wall in roughly the transpyloric plane (L1)
Lesser sac?
Extending towards the right from the hilum of the spleen and posterior to the stomach is part of the lesser sac.
Which artery gives off the superior thyroid artery?
External carotid artery
Where does the right suprarenal vein drain into?
IVC - This makes it difficult to remove when performing an adrenalectomy
The spleen information:
In a normal adult the spleen does not extend further forwards than the midaxillary line. In a healthy adult you cannot palpate the spleen.However, sometimes it may get enlarged and then you can feel it below the left costal margin.
Why is the hypophyseal fossa also known as the sella turcica?
The depth of this fossa is exaggerated by clinoid processes at each corner, and a roof of dura mater surrounding the pituitary stalk, and is also therefore known as the sella turcica
What does vasopressin do?
Causes vasoconstriction but also has antidiuretic function causing an increase in absorption of water in the distal convoluted tubules and collecting ducts in the kidney.
What is the anterior surface of the pancreas covered in?
The anterior surface of the pancreas is covered with peritoneum and lies behind the stomach. The transverse mesocolon is attached to the anterior surfaces of the head and neck, and the anterior border of the body of the pancreas.
Blood supply of the parathyroid glands?
The blood supply is mostly by the inferior thyroid arteries.
what is the blood supply of the pancreas?
The body and tail - receive blood supply from the splenic artery (several pancreatic branches from the splenic artery form anastomotic arcades with pancreatic branches of the gasproduodenal artery and SMA.) The head of the pancreas - Supplied by the branches of the anterior and posterior superior pancreaticoduodenal artery (branches of gastroduodenal artery) and by the anterior and posterior inferior pancreaticoduodenal arteries (branches of the SMA)
What is the accessory duct (of santorini)?
Sometimes an accessory duct may enter the duodenum proximal to the main duct. As a rule only a small upper anterior part of the head uses the accessory pancreatic duct as a drainage system.
Which part of the thyroid gland is supplied by the superior thyroid artery?
The STA descend to the superior poles of each lobe and pierce through the pre tracheal fascia and divide into anterior and posterior branches.
Is the whole of the pancreas retroperitoneal?
All of the pancreas is retroperitoneal except the tail - which sits in the hilum of the spleen
The pituitary gland:
Also known as the hypophysis is the size and shape of a baked bean.
Innervation of the spleen?
Autonomic nerves derived from the celiac plexus accompany the splenic artery to innervate the spleen.
Describe the position of the neck of the pancreas?
Continuous with the head of the pancreas is its neck which is situated anterior to the Superior mesenteric vein and the hepatic portal vein.
What is the blood supply to the suprarenal glands?
Each gland has three arteries supplying it: 1) A branch from the phrenic artery --> superior supra renal artery 2) A direct branch from the aorta --> Middle suprarenal artery 3) A branch from the renal artery --> inferior suprarenal artery
Which artery gives off the inferior thyroid artery?
It is a branch of the thyrocervical trunk <-- subclavian artery
Which layer is the medulla derived from?
It is derived from the neural crest (ectoderm)
innervation of the suprarenal glands?
Pregnaglionic fibres from thoracic splanchnic nerves (especially greater splanchnic ) end in the suprarenal medulla to innervate the glands.
Where is the uncinate process?
Projects from the lower part of the head and extends leftward and posteriorly behind the superior mesenteric vessels is the uncinate process of the pancreas
All retroperitoneal organs?
SADPUCKER- Suprarenal (adrenal) glands Aorta/IVC Duodenum (2nd + 3rd segments) Pancreas (except tail) Ureters Colon (ascending and descending parts) Kidneys Esophagus Rectum
Where does the head of the pancreas lie?
The head of the pancreas lies within the C-shaped concavity of the duodenum
The venous drainage of the parathyroid glands?
The parathyroid veins drain into the venous plexus around the thyroid gland so have the same venous drainage as the thyroid gland.
The thyroid glands:
The thyroid gland produces thyroid hormones which are secreted into the blood and then carried to every tissue in the body. The thyroid hormones are essential to proper development and differentiation of all cells of the human body; they regulate protein, fat, and carbohydrate metabolism and stimulate vitamin metabolism. Thyroid hormones cause increases in the basal metabolic rate, affect protein synthesis, help regulate long bone growth, neuronal maturation and increase the body's sensitivity to catecholamines (such as adrenaline).
Where lies the splenic artery?
The tortuous splenic artery lies along the upper border of the pancreas.
Lymphatic drainage of the thyroid gland?
lymphatic vessels within the thyroid gland itself drain to a capsular lymphatic plexus and thence to the following lymph nodes - 1) Pre - laryngeal --> superior cervical nodes 2) Pre - tracheal and paratracheal nodes --> inferior deep cervical nodes
What is a pyramidal lobe?
occasionally you have an extra pyramidal lobe which is present and this projects upwards from the isthmus.
what two nuclei's axons make up the posterior pituitary?
supra optic and paraventricular
The right suprarenal gland:
1) Is pyramidal in shape and sits on the pole of the right kidney 2) Lies behind the right lobe of the liver and tucks medially behind the inferior vena cava 3) lies over the right crus of the diaphragm
What are the three zones of the suprarenal cortex?
1) The thin outer layer of the cortex is the zone glomerulosa which secretes mineralocorticoids (e.g. aldosterone which acts on the distal convoluted tubule of the kidney to modulate water/ electrolyte balance) 2)The thick middle zone of the cortex is the zone fasiculata, which secretes glucocorticoids (e.g. cortisol, corticosterone, etc. which regulate carbohydrate metabolism , facilitate catabolism of fats and proteins, show anti inflammatory activity and suppress immune responses) 3) The thin inner zone is the zone reticularis, which secretes weak androgens (promoting masculine characteristics)
What are the different parts of the pancreas?
1) head with uncinate process 2) body 3) neck 4) tail
The left suprarenal gland:
1) is crescent shaped and extends down towards the hilum of the left kidney 2) is posterior to the pancreas, splenic vessels, and stomach 3) Lies over the left crus of the diaphragm. 4) The celiac plexus lies between the left suprarenal gland and pancreas.
What are the five different types of endocrine cells in the anterior pituitary?
1) somatotroph - GHRH/GHIH --> GH --> stimulates liner growth in epiphyseal cartilages. 2) Lactotroph - PRH/PIH --> prolactin --> stimulates lactogenesis 3) Corticotroph - CRH --> ACTH--> stimulates the suprarenal glands to produce corticosteroids and sex hormones 4) Thyrotroph - TRH --> TSH --> stimulates the production of thyroxine by the thyroid glands 5) Gonadotroph - LHRH/FRH --> LH and FSH --> stimulates ovarian follicles and production of oestrogen and progesterone
What are the two parts of the pituitary gland?
1) the anterior/ adenohypophysis lobe 2) posterior / neurohypophysis lobe
What tracheal rings does the isthmus overlie?
2nd - 4th tracheal rings
What vessels are enclosed in the gastrosplenic ligament:
Encloses the short gastric vessels, the left gastroepiploic vessels (gastro-omental) and branches of the splenic artery which supply the stomach.
Adrenal cortex mnemonic:
Go Find Rex, Make Good Sex: G - glomerulosa, F - fasciculata, R - reticularis, M - mineralcorticoids, G - glucocorticoids, S - sex hormones
The situation of the thyroid gland in the body?
It is a highly vascular organ that is located in the anterolateral regions of the neck overlying the trachea and the larynx. It is a bilobed gland which are connected in the midline by a narrow isthmus. It has its own fibrous capsule Each lobe of the thyroid gland is pear shaped with its apex lying over the thyroid cartilage of the larynx, and the base of the the thyorid gland lies at the level 4th or 5th tracheal ring
What does the supraoptic nucleus act like?
It is an osmoreceptor and so if the blood circulating through it is at high osmotic pressure, its neuronal cell bodies increase the production of vasopressin which will cause increased absorption of water in the kidney back into the vascular compartment --> reducing osmotic pressure.
What is the posterior surface of the body of the pancreas in contact with?
It is in contact with the Aorta between the origins of the coeliac artery and the superior mesenteric artery. It in also in contact with the left suprarenal gland and left kidney with its associated vessels.
What are the three distinct components of the anterior pituitary?
It is largely composed of a distal lobe - pars distalis - which is incompletely separated from the posterior pituitary by a rudimentary intermediate lobe = pars intermedia. A layer of extending into the pituitary stalk is the anterior tubular lobe = pars tuberalis
Where is the pituitary gland located?
It is located on the underside of the brain to which it is connected to via the pituitary stalk, and sits within a depression of the sphenoid bone known as the hypophyseal fossa.
What does oxytocin do?
It is produced in large amounts at the end of a pregnancy and its stimulates the contractions of uterine smooth muscle during child birth. Also the stimulation of the nipple by sucking infant stimulates the paraventricular nucleus to secrete more oxytocin which causes contraction of the myoepithetlial cells surrounding the alveoli and ducts of the breast and expression of milk - the 'let down reflex'.
What is the lymphatic drainage of the pancreas?
Lymphatic drainage of the pancreas tends to follow its blood vessels. Most of the lymph initially flows to the pancreatiocsplenic lymph nodes which lie along the splenic artery or to the pre- pyloric lymph nodes. Efferent vessels from these nodes then drain into the coeliac, hepatic and superior mesenteric lymph nodes.
Is the spleen retroperitoneal?
NO
What is on the visceral surface of the spleen?
On the visceral surface of the spleen is the hilum where blood and lymphatic vessels enter or leave.
The lymphatic drainage of the parathyroid glands?
Same as the thyroid gland Prelaryngeal pre tracheal and paratracheal nodes
Innervation of the parathyroid glands?
Same as thyroid gland so sympathetic vasomotor innervation from the superior, middle and inferior cervical ganglia --> the fibres reach the gland along the periarterial plexuses which accompany the inferior thyroid arteries as they supply the parathyroid glands.
What hormones mostly mediate the secretion of the pancreas?
Secretin and Cholecystokinin
The venous drainage of the spleen?
Several veins draining the spleen unite under the hilum of the spleen to from the splenic vein. The splenic vein passes across the abdominal wall behind the body of the pancreas and joins the superior mesenteric vein to form the hepatic portal vein behind the neck of the pancreas.
The route of the superior mesenteric vein in relation to the pancreas?
So the SMV passes anterior to the uncinate process and posterior to the neck of the pancreas.
How do the regulatory hormones from the hypothalamus travel to the anterior pituitary?
Through the long portal veins of hypothalamic-hypophyseal portal system
Describe the position of the body of the pancreas?
The body of the pancreas continues with the neck and gradually slopes superiorly to the left to reach the hilum of the spleen. The body is triangular in section with posterior,anterior and inferior surfaces.
What is the function of the parathyroid glands?
The function of the parathyroid glands is to secrete PTH into the blood stream which controls the calcium in the blood within a very tight range. They control how much calcium is contained in bones. As blood passes through the thyroid glands they detect the Ca2+ levels in the blood and respond by making more or less PTH. A drop in calcium causes an increase in PTH.
What is the thyroid gland surrounded by?
The gland is surrounded by pre tracheal fascia which is external to the capsule of the thyroid gland. The pre tracheal fascia holds the gland in position in the neck. If the thyroid gland enlarges, it does so in an inferior direction, since the pre-tracheal fascia surrounding it also attaches laterally to the carotid sheath, limiting expansion of the thyroid laterally . Superiorly the attachment of thyrohyoid prevents the thyroid enlarging in a superior direction.
What is immediately posterior the head of the pancreas?
The inferior vena cava, the renal veins and bile duct
The lymphatic drainage of the spleen?
The lymphatic vessels in the spleen drain into several nodes at the hilum and efferent vessels from this drain into the coeliac group of lymph nodes.
The main pancreatic duct (of wirsung) and its route?
The main pancreatic duct begins in the tail of the pancreas as the amalgamation of several small ducts and extends to the head where it turns downward and backward.
what is the hepatopancreatic ampulla?
The main pancreatic duct pierces the posteromedial wall of the descending part of the duodenum at about its middle and opens with the bile duct into the hepatopancreatic ampulla which goes into the duodenum via the major duodenal papilla.
The medulla of the suprarenal glands:
The medullary region is derived from the neural crest cells. Two types of chromaffin cells (Chromaffin cells, also pheochromocytes, are neuroendocrine cells found mostly in the medulla of the adrenal glands (located above the kidneys) in mammals) present in the medulla secreteeither adrenaline and noradrenaline. It is directly regulated by preganglionic fibres of the sympathetic nervous system. Scattered sympathetic ganglionic cells in the medulla also act on smooth muscle cells in the medullary veins to control blood flow through the suprarenal glands.
Where does the neck of the pancreas lie?
The neck of the pancreas lies on the transpyloric plane approx 1 cm left of the midline, behind the pylorus.
Where is vasopressin and oxytocin synthesised?
The neuronal cell bodies of the supraoptic nucleus synthesise the hormone = vasopressin also known as antidiuretic hormone The neuronal cell bodies of the paraventricular nucleus synthesise oxytocin.
Innervation of the pancreas?
The pancreas is a gland and therefore receives autonomic innervation. Visceral efferents both sympathetic (from abdominopelvic splanchnic nerves) and parasympathetic ( via the vagus nerve) reach the pancreas via travelling along the supplying arteries. Sympathetic fibres innervate smooth muscle in pancreatic blood vessels walls and both sympathetic and parasympathetic axons pass to pancreatic acinar cells and Islets of Langerhans.
The venous drainage of the suprarenal glands?
The segmental veins of the suprarenal glands drain into a single main vein from the hilum of the gland to the nearest available vessel, which is for the right suprarenal gland = IVC and for the left renal gland = left renal vein
Describe the spleen?
The spleen is firm, vascular organ which is reddish in colour and about the size of a closed fist. The outer surface of the spleen is convex and the inner (visceral) surface is concave.
Peritoneal coverings of the spleen:
The spleen is invested in peritoneum coming from both the posterior abdominal wall (splenorenal ligament) and the greater curvature of the stomach (gastrosplenic ligament) These ligaments form the left lateral boundary of the lesser sac and provide the routes by which the blood vessels pass from the abdominal aorta on the posterior abdominal wall to the spleen and the stomach
What is the splenorenal ligament/ilenorenal ligament?
The spleen is not retroperitoneal and so the pancreatic tissue must be between two layers of peritoneum which are known as the splenorenal ligament. The splenorenal ligament (or lienorenal ligament), is derived from the peritoneum, where the wall of the general peritoneal cavity comes into contact with the lesser sac between the left kidney and the spleen
What is the exact situation of the spleen in the body?
The spleen is situated in the left hypochondrium at the level of the posterior parts of the 9th to 11th ribs. The left half of the diaphragm separates the convex surface of the spleen from the costodiaphragmatic recess of the pleural cavity and 9th to 11th ribs.
Blood supply of the spleen?
The splenic artery This artery is a branch of the coeliac artery and it runs a tortuous course along the superior margin of the pancreas.Having passed through the splenorenal ligament the artery divides into several branchess which enter the hilum of the spleen. The splenic artery supplies the spleen and the pancreas and also gives rise to short gastric and left gastroepiploic arteries near the hilum of the spleen.
What does the splenorenal ligament enclose?
The splenic artery and vein and the tail of the pancreas.
Where does the splenic vein lie?
The splenic vein usually lies posterior to the body of the pancreas but can also be sometimes embedded in the gland.
Parathyroid glands:
The superior and inferior parathyroid glands are small, flattened oval structures which lie medially in pairs on the posterior surface of the thyroid gland. Most individuals have 4 parathyroid glands but 5% have two.
Suprarenal glands and their different parts?
The suprarenal glands consist of a cortex and a medulla which represent two developmentally and functionally independent endocrine glands within the same anatomical structure
The innervation of the suprarenal medulla and what it secretes?
The suprarenal medulla receives preganglionic fibres from the greater splanchnic nerves and secretes adrenaline and nor adrenaline.
The blood supply to the thyroid gland?
The thyroid gland is supplied by a pair of arteries on each side - The superior and inferior thyroid arteries
The innervation of the thyroid gland
The thyroid gland only receives sympathetic innervation which is just vasomotor from the SUPERIOR, MIDDLE AND INFERIOR CERVICAL GANGLIA ; the fibres reach the gland along the PERIARTERIAL PLEXUSES which accompany the thyroid arteries. The endocrine secretion from the thyroid is regulated by the influence of TSH from the anterior pituitary gland.
Where does the thyroid ima artery arise from?
The thyroid ima artery can arise from 1) the brachiocephalic trunk 2) the aortic arch 3) right common carotid, subclavian, internal thoracic arteries If it is present it ascends over the trachea to supply the isthmus.
What is the venous drainage of the pancreas?
The venous drainage is mostly to the splenic vein and also to the SMV and/or directly into the hepatic portal vein
What is on the visceral surface of the spleen?
There are impressions made by adjacent viscera, the stomach, kidney, colon and pancreas.
What are the two main cell types within the thyroid gland and what do they secrete?
There are the: 1) follicular cells - secrete thyroxine (T4) and triiodothyronine (T3) 2) parafollicular cells - secrete calcitonin
The venous drainage of the thyroid gland?
There are three pairs of thyroid veins - 1) superior thyroid vein --> internal jugular vein 2) inferior thyroid vein -->brachiocephalic vein Both superior and inferior run alongside the corresponding arteries. 3) middle thyroid vein --> internal jugular vein All three receive venous blood from a plexus of veins which surround the thyroid gland.
The lymphatic drainage of the suprarenal glands?
There are two lymphatic plexuses associated with the suprarenal glands. One lies deep to the capsule Other lies deep to the medulla Lymph from these plexuses drains into the lumbar lymph nodes also known as the lateral aortic nodes.
where are the suprarenal glands situated in the body?
They are located on the upper poles of the kidneys and lie against the diaphragm. They are retroperitoneal structures which are surrounded by their own individual capsule which in turn is surrounded by renal fascia. This arrangement allows the easy removal of the suprarenal glands during surgery.
Where are both oxytocin and vasopressin released?
They are released at the axon terminals in the posterior lobe and immediately absorbed into the bloodstream circulating through its fenestrated capillaries.
Which part of the thyroid gland is supplied by the inferior thyroid arteries?
They run superomedially posterior to the carotid sheaths to reach to the posterior aspect and inferior poles of each lobe.
The posterior pituitary:
This is a direct, inferior continuation of the hypothalamus. It is composed of axons extending from the neuronal cell bodies located in the supraoptic and paraventricular nuclei of the hypothalamus, supported by specialised glial cells known as pituicytes. The axons terminate in the posterior pituitary lobe adjacent to a dense capillary network.
Which layer is the cortex derived from?
This is derived from the mesoderm