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Endocrine SystemYuniartiAnatomy DepartmentFaculty of MedicineUNISBAglandA gland may consist of a single cell or a group of cells that secrete substances into ducts (tubes), onto a surface, or into the blood.All glands of the body are classified as either endocrine or exocrine.

ENDOCRINE GLANDEKSOKRIN GLANDsecretions, called hormonessecretions includemucus, sweat, oil, earwax, saliva, and digestive enzymes Secrete their product into the interstitial fluid and thendiffuse directly into the bloodstream without flowing through a ductSecrete their products into ducts that empty onto the surfaceof a covering and lining epithelium such as the skin surface or thelumen of a hollow organ.

Hypothalamic glandPituitary glandThyroid glandParathyroid glandThymus glandPancreas glandAdrenal glandGonads gland

Hypothalamus The hypothalamus is a small part of the diencephalon located inferior to the thalamus

Forms the floor and the inferior part of the lateral walls of the third ventricle

Four major regions of hypothalamus:

1. The mammillary region - Adjacent to midbrain, is the most posterior part of the hypothalamus - It includes : * the mammillary bodies * posterior hypothalamic nucleus

2. The tubular region - The widest part of hypothalamus - It includes : *dorsomedial nucleus *ventromedial nucleus *arcuate nucleus *infundibulum

3. The supraoptic region - Lies to the optic chiasm - Contains : * paraventricular nucleus * supraoptic nucleus * anterior hypothalamic nucleus * suprachiasmatic nucleus

4. The preoptic region - Contain : *medial preoptic nucleus *lateral preoptic nucleus

NucleusFunctionSupraoptic nucleusSynthesizes vasopressin (antidiuretic hormone)Paraventricular nucleusSynthesizes oxytocinPreoptic and anterior nucleiControl parasympathetic systemPosterior and lateral nucleiControl sympathetic systemAnterior hypothalamic nucleiRegulate temperature (response to heat)Posterior hypothalamic nucleiRegulate temperature (response to cold)Lateral hypothalamic nucleiInitiate eating and increase food intake (hunger center)Medial hypothalamic nucleiInhibit eating and reduce food intake (satiety center)Lateral hypothalamic nucleiIncrease water intake (thirst center)Suprachiasmatic nucleusControls circadian rhythms Hypothalamic Regulatory HormoneFunctional ResultGrowth hormonereleasing hormone (GHRH)Stimulates linear growth in epiphyseal cartilagesGrowth hormoneinhibiting hormone (GHIH) or somatostatinReduces linear growth in epiphyseal cartilagesProlactin-releasing hormone (PRH)Stimulates lactogenesisProlactin-inhibiting hormone (PIH), dopamineReduces lactogenesisCorticotropin-releasing hormone (CRH)Stimulates adrenal gland to produce corticosteroids and sex hormonesThyrotropin-releasing hormone (TRH)Stimulates thyroid gland to produce thyroxineLuteinizing hormonereleasing hormone (LHRH),follicle-stimulating releasing hormone (FRH)Stimulates ovarian follicles and production of estrogen and progesterone Hypofisis glandPituitary (hypofisis) glandThe Master Gland :produces hormones that control the activity of other endocrine glands It is a small gland located in the sella turcica (Turk's saddle) of the sphenoid bone of the skull, immediately inferior to the hypothalamus of the brain. The sphenoid bone serves as a protective cradle around the gland. A stalk or infundibulum attaches the gland to the hypothalamus.

Contains two lobes, the anterior (adenohypophysis) and posterior (neurohypophysis). The anterior lobe has three part : pars distalis (Anterior lobe), pars tuberalis, pars intermediaPars tuberalis is a funnel-shaped region surrounding the infundibulum of the neurohypophysis . Most of the cells of the pars tuberalis are basophilic gonadotropic cells that secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH).The pars intermedia, separates the anterior and posterior pituitary. It produces, melanocyte stimulating hormone (MSH). The posterior lobe, the neurohypophysis or pars nervosaAnterior pituitary / adenohypofisis gland

Five types of anterior pituitary cells secrete seven hormones :

Release of anterior pituitary hormone is stimulated by releasing hormone and supressed by inhibiting hormone from the hypothalamus

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Vascularization of anterior pituitary (hypophyseal portal system)The superior hypophyseal arteries, branches of the internal carotid arteries,bring blood ito the hypothalamusat the juncture of the median eminence of the hypothalamus and the infundibulum, these arteries divide into a capillarynetwork called the primary plexus of the hypophyseal portal systemfrom the primary plexus, blood drains into the hypophyseal portal veins that pass down the outside of the infundibulum In the anterior pituitary, the hypophyseal portal vein divide again and form another capillary network called the secondary plexus of the hypophyseal portal systemFrom this plexus, blood drains into anterior hypophyseal vein

Hormone release in anterior pituitaryNear the median eminence and above the optic chiasm are clusters of specialized neurons, called neurosecretory cells They synthesize the hypothalamic releasing and inhibiting hormonesin their cell bodies and package the hormones inside vesicles,which reach the axon terminals by axonal transport. Nerve impulses stimulate the vesicles to undergo exocytosis The hormonesthen diffuse into the primary plexus of the hypophyseal portal system Quickly, the hypothalamic hormones flow with the blood through the portal veins and into the secondary plexus. To anterior pituitary cells, before the hormones are diluted or destroyed in the general circulation Hormones secreted by anterior pituitary cells pass into the secondary plexus capillaries drain into the anterior hypophyseal veins and out into thegeneral circulation. Anterior pituitary hormones then travel totarget tissues throughout the bodyPosterior pituitary / neurohypofisis gland

The posterior pituitary (posterior lobe) contains axons and axon terminals whose cell bodies are located in the supraoptic nuclei (produces antidiuretic hormone (ADH) / vasopressin) and paraventricular nuclei (produces oxytocin (OT).

The posterior pituitary it does not synthesize hormones, it does store and release two hormoneThe inferior hypophyseal arteries, which branch from the internal carotidarteries, supply blood to the posterior pituitary.

In the posterior pituitary, the inferior hypophyseal arteries drains into the capillary plexus of the infundibular process, a capillary network that receives secreted oxytocin and antidiuretic hormone.

From this plexus,hormones pass into the posterior hypophyseal veins for distribution to target cells in other tissue

Vascularization of posterior pituitaryThe cell bodies of the neurosecretory cells are in the paraventricular and supraoptic nuclei of the hypothalamus their axons form the hypothalamohypophyseal tract The paraventricular nucleus synthesizesthe hormone oxytocin and the supraoptic nucleus produces vasopressin After their production in the cell bodies of neurosecretory cells, oxytocin and vasopressin are packaged into secretory vesicles which move by fast axonal transport to the axon terminals in the posteriorpituitary, where they are stored until nerve impulses trigger exocytosis and release of the hormone.

Blood is supplied to the posterior pituitary by theinferior hypophyseal arteries, which branchfrom the internal carotid arteries the inferior hypophyseal arteries drain into the capillary plexus of the infundibular process, a capillary network that receives secreted oxytocin and antidiuretic hormone From this plexus, hormones pass into the posterior hypophyseal veins for distribution to target cells in other tissues.

Hormone release in posterior pituitaryThyroid glandThyroid glandThe thyroid gland is located anteriorly in the neck. Weight : 25 gIt lies deep to the sternothyroid and sternohyoid muscles from the level of the C5-T1 vertebrae

It consists primarily of right and left lobes, anterolateral to the larynx and trachea

A relatively thin isthmus unites the lobes over the trachea, usuallyanterior to the second and third tracheal rings

The thyroid gland is surrounded by a thin fibrous capsule, which sends septa deeply into the gland.

Approximately 50% of thyroid glands have a pyramidal lobe.

This lobe, which varies in size, extends superiorly from the isthmus of thyroid gland, usually to the left of the median plane; the isthmus may be incomplete.

The pyramidal lobe develop from remnants of the epithelium and connective tissue of the thyroglossal duct

Portions of the thyroglossal duct may persist to form thyroid tissue

Accessory thyroid glandular tissue may appear anywhere along the embryonic course of the thyroglossal duct.

Accessory thyroid tissue may develop in the neck lateral to the thyroid cartilage; it usually lies on the thyrohyoid muscle.

Although the accessory tissue may be functional, it is often of insufficient size to maintain normal function if the thyroid gland is removed

Vascularization of thyroid glandThe rich blood supply of the thyroid gland is from the paired superior and inferior thyroid arteriesIn approximately 10% of people, a thyroid ima artery arises from the brachiocephalic trunk, the arch of the aorta, or from the right common carotid, or subclavian artery.This small artery ascends on the anterior surface of the trachea, which it supplies, andcontinues to the isthmus of the thyroid gland.Three pairs of thyroid veins usually drain the thyroid plexus of veins on the anterior surface of the thyroid gland and trachea

The superior and middle thyroid veins drain into the IJVs

The inferior thyroid veins drain into thebrachiocephalic veins

Parathyroid glandParathyroid gland Embedded in the posterior surface of the lateral lobes of the thyroid gland Each has a mass of about 40 mg (0.04 g) Usually, one superior and one inferior parathyroid gland are attached to each lateral thyroid lobe, for a total of four.

The two superior parathyroid glands are usually at the level of the inferior border of the cricoid cartilage.

The inferior parathyroid glands are usually near the inferior poles of thethyroid gland, but they may lie in a variety of positions.

Sites and frequenciesof abberant parathyroidglandular tissueThe inferior thyroid arteries supply both the superior and the inferior parathyroid glands

However, these glands may also be supplied by branches fromthe superior thyroid arteries, the thyroid ima artery, or the laryngeal, tracheal, and esophageal arteries. Vascularization of parathyroid gland

The parathyroid veins drain into the thyroid plexus of veins of the thyroid glandVascularization of parathyroid gland

Adrenal glandLocation of Suprarenal Glands

Located between the superomedial aspects of the kidneys and the diaphragm

The pyramidal right gland is more apical (situated over the superior pole) relative to the right kidney, lies anterolateral to the right of the diaphragm, and makes contact with the IVC anteromedially and the liver anterolaterally

The crescent-shaped left gland is medial to the superior half of the left kidney and is related to the spleen, stomach, pancreas and the left of the diaphragm

Suprarenal glands surrounded by connective tissue containing considerable perinephric fat

Suprarenal glands are enclosed by renal fascia by which they are attached to the crura of the diaphragm

Each gland has a hilum, where the veins and lymphatic vessels exit the gland; whereas arteries and nerve enter the glands at multiple sites

The medial borders of the suprarenal glands are 4-5 cm apart. In this area, from right to left, are the IVC, right of the diaphragm, celiac ganglion, celiac trunk, SMA and the left of the diaphragm.

Each suprarenal gland has two parts : ~ Suprarenal cortex ~ Suprarenal medulla is a modified sympathetic ganglion of the ANSSUPRARENAL CORTEX

Derives from mesoderm

Vascularisation of suprarenal glands

Suprarenal glands arteries :~ Superior suprarenal arteries ~ Middle suprarenal arteries ~ Inferior suprarenal arteries

Venous drainage :

~ Right suprarenal vein drains into the IVC

~ Left suprarenal vein drains into the left renal veinPancreas glandLocation of pancreas :

Pancreas is an elongated, accessory digestive gland that lies retroperitoneally

Transversely across the posterior abdominal wall posterior to the stomach betweenduodenum on the right and the spleen on the left.

The pancreas produce :

An exocrine secretion ( pancreatic juice from the acinar cells) that enter the duodenum through the main and accessory pancreatic ducts.

Endocrine secretion (glucagon & insulin) from the pancreatic islets (of langerhans) that enter blood.

Parts of pancreas :HeadNeckBodyTail

The head of the pancreas is the expanded part of the gland that is embraced by the C-shaped curve of the duodenum to the right of the superior mesenteric vessels. It firmly attaches to the medial aspect of the descending and horizontal parts of the duodenum.

The uncinate process, a projection from the inferior part of the pancreatic head, extends medially to the left, posterior to the SMA.

The neck of the pancreas is short and overlies the superior mesenteric vessels, which form a groove in its posterior aspect

The anterior surface of the neck, covered with peritoneum, is adjacent to the pylorus of the stomach.

The tail of the pancreas lies anterior to the left kidney, where it is closely related to the splenic hilum and the left colic flexure.

The tail is relatively mobileThe main pancreatic duct

Begins in the tail of the pancreas and runs through the parenchyma of the gland to the pancreatic head, here it turns inferiorly and is closely related to the bile duct.

Most of the time, the main pancreatic duct and the bile duct unite to form the short, dilated hepatopancreatic ampulla (of vater), which opens into the descending part of the duodenum at the summit of the major duodenal papilla

Accessory pancreatic duct

Opens into the duodenum at the summit of the minor duodenal papilla

Usually (60%) communicates with the main pancreatic duct

Smooth muscle sphincter that control the flow of bile & pancreatic juice into duodenum : - Sphincter of the pancreatic duct - Sphincter of the bile duct - Sphincter of hepatopancreatic (sphincter of Oddi)

-The pancreatic arteries derive mainly from the branches of the splenic artery -The anterior and posterior superior pancreaticoduodenal arteries, branches of the gastroduodenal artery-The anterior and posterior inferior pancreaticoduodenal arteries, branches of the SMA

The pancreatic veins are tributaries of the splenic and superior mesenteric parts of the hepatic portal vein; however, most of them empty into the splenic vein