Lecture 2 Endocrine System Anatomy PDF

LECTURE 2 BY/DR.MAHA ABDEL BAKY AHMED These are a pair of important endocrine glands ANATOMY OF ADRENAL GLAND situated on the posterior abdominal wall over the upper pole of the kidneys behind the peritoneum SITE Each gland lies at the upper pole of the kidney, in front of the crus of the diaph...

LECTURE 2 BY/DR.MAHA ABDEL BAKY AHMED These are a pair of important endocrine glands ANATOMY OF ADRENAL GLAND situated on the posterior abdominal wall over the upper pole of the kidneys behind the peritoneum SITE Each gland lies at the upper pole of the kidney, in front of the crus of the diaphragm, opposite the vertebral end of the 11th intercostal space and the 12th rib. They are made up of two parts: (a) an outer cortex of mesodermal origin, which secretes a number of steroid hormones (b) an inner medulla of neural crest origin, which is made up of chromaffin cells and secretes adrenalin and noradrenalin (catecholamines). RELATIONS The adrenal glands consist of the adrenal cortex and medulla The adrenal cortex contains The zona glomerulosa that produces mineralocorticoids, The zona fasciculata that is the site of glucocorticoid biosynthesis, and the zona reticularis, which is responsible for the production of adrenal androgens  RIGHT SUPRARENAL GLAND It is triangular (or pyramidal) in shape. It has 1) an apex; 2) a base; 3)two surfaces (anterior and posterior); and (4) three borders (anterior, medial and lateral). Relations: A- The base is related to the upper pole of the right kidney. B. The anterior surface is devoid of peritoneum, except for a small part inferiorly. It is related to: 1. The inferior vena cava, medially; (2) The liver, laterally. C. The posterior surface is related to the right crus of the diaphragm The hilum lies near the apex from which the right suprarenal vein arise to join the inferior vena cava.  LEFT SUPRARENAL GLAND The left gland is semilunar. It has (1) two ends (upper, narrow end; and lower, rounded end); (2) two borders (medial convex; and lateral concave); and (3) two surfaces (anterior and posterior). Relations: A. Anterior surface. From above downwards it is related to: (1) the cardiac end of the stomach; (2) the splenic artery; and (3) the pancreas. B. Posterior surface. It is related to: (1) the kidney, laterally; and (2) the left crus of the diaphragm, medially. Each gland is supplied by three arteries: 1) The superior suprarenal artery, a branch of the inferior phrenic artery; 2) The middle suprarenal artery, a branch of the abdominal aorta; and 3) The inferior suprarenal artery, a branch of the renal artery. Venous Drainage Each gland is drained by one vein. The right suprarenal vein drains into the inferior vena cava, and the left suprarenal vein into the left renal vein Lymphatic Drainage the suprarenal glands drain into the lateral aortic nodes. Nerve Supply he suprarenal medulla has a rich nerve supply through sympathetic fibers. Embryology:the adrenal gland is composed of two embryologically distinct tissues, the cortex and medulla, arising from the mesoderm and neuroectoderm, respectively The adrenal gland is composed of two embryologically distinct tissues, the cortex and medulla, arising from the mesoderm and neuroectoderm, respectively. An isolated clump of cells appears within the urogenital ridge, known as the adrenal-gonadal primordium. This tissue gives rise to the fetal adrenal cortex and to Lyedig cells. At 7 weeks of gestation, sympatho-adrenal cells migrate into the adrenal primordium. In later stages of embryonic development, the cortex engulfs, and ultimately encapsulates the entire medulla.  PANCREAS 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. RELATIONS Stomach – Separated from the pancreas by the lesser sac, 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. The lienorenal ligament is formed from peritoneum and connects the spleen to the tail of the pancreas. PANCREAS Nerves: parasympathetic: vagus nerve (CN X) Sympathetic: greater and lesser splanchnic nerves Lymph node : Pancreaticoduodenal, splenic, gastroduodenal, and superior mesenteric arteries Embryology: The pancreas first appears at approximately 5 weeks of gestation as two outpouchings of the endodermal lining of the duodenum just distal to the forming stomach. The outpouchings are the ventral and dorsal pancreas. The dorsal pancreas grows more rapidly than the ventral pancreas. In addition, the ventral pancreas rotates toward the dorsal pancreas as it is “carried” by the common bile duct. Finally, the ventral and dorsal pancreas join and the ductal systems fuse so that secretions from the ventral pancreas enter the shared ductal system of the ventral pancreas and common bile duct.  The head of the pancreas originates from both the dorsal pancreas and the ventral pancreas. The ventral pancreas portion is called the uncinate process.  The body and tail of the pancreas originate from the dorsal pancreas. During the eighth week of gestation, the remaining portion of the ventral diverticulum separates into the pars cystica and pars hepatica. The pars cystica forms the cystic duct and gallbladder. The pars hepatica branches to form the two major lobes of the liver. The proliferation is followed by vacuolation, and the coalescence of the ensuing lacunae produces a tubular biliary duct system. The pars cystica vacuolates and expands, and the stalk becomes the cystic duct. This structure is initially hollow, then solid (by proliferation of epithelial lining), and recanalization occurs by vacuolation of this expanded epithelium. The dorsal pancreatic bud forms the upper head, body, and tail of the pancreas. The ventral bud forms the inferior head and uncinate process. When both pancreatic buds fuse, the pancreatic duct system starts to establish.  The main pancreatic duct forms from the ventral pancreatic duct in the head and the distal part of the dorsal pancreatic duct in the body and tail.  The accessory pancreatic duct forms from the dorsal pancreatic duct. The accessory pancreatic duct (dorsal pancreatic duct) joins the main pancreatic duct (ventral pancreatic duct) at a site 1-2 cm proximal to the ventral pancreatic duct or at the distal end of the ventral pancreatic duct.