endocrine system anatomy.pptx for BSN Generic

Endocrine system ppt for BSN student

1. ENDOCRINE SYSTEM 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.

2. ENDOCRINE SYSTEM 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

3. ENDOCRINE SYSTEM

4. PITUITARY GLAND 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.

5. Anatomical Structure 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.

6. PITUITARY GLAND 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.

7. PITUITARY GLAND 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.

8. PITUITARY GLAND 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

9. PITUITARY GLAND

10. ARTERIAL SUPPLY 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:

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

12. 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.

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

14. Anatomical Location 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 ).

15. Anatomical Relations 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

16. ARTERIAL SUPPLY 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.

17. ARTERIAL SUPPLY 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.

18. NERVE AND LYMPHATIC SUPPLY 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 .

19. parathyroid gland 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.

20. Anatomical Location 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 ) 

21. ARTERIAL SUPPLY 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 .

22. NERVE AND LYMPHATIC SUPPLY 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.

23. PINEAL GLAND 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.

24. Anatomical Structure and Position 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.

25. Anatomical Position 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

26. arterial supply 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 .

27. ADRENAL GLAND 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.

28. Anatomical Location and Relations 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.

29. Anatomical Location and Relations 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

30. Anatomical Structure 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.

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

32. Anatomical Structure 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.

33. Anatomical Structure 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.

34. ARTERIAL SUPPLY 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 .

35. Nerve AND LYMPH SUPPLY 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.

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

37. Anatomical Position 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.

38. Relations 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.

39. PARTS OF PANCREAS 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 ..

40. PARTS OF PANCREAS

41. Duct System 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.

42. Duct System

43. Arterial supply 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.

44. Arterial supply

45. Lymphatics 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.