Organs of Abdominal Cavity Lecture Sp25 PDF

Organs of the Abdominal Cavity Gastrointestinal System in Health & Disease HWDP 142 Meghan M. Newcomer, PhD [email protected] Outline ▪ Organs of Abdominal Cavity ▪ Blood Supply ▪ Innervation Organs of Abdominal Cavity ▪ Abd...

Organs of the Abdominal Cavity Gastrointestinal System in Health & Disease HWDP 142 Meghan M. Newcomer, PhD [email protected] Outline ▪ Organs of Abdominal Cavity ▪ Blood Supply ▪ Innervation Organs of Abdominal Cavity ▪ Abdominal cavity bounded by abdominal walls, diaphragm, & pelvis Forms major part of abdominopelvic cavity: combined & continuous abdominal & pelvic cavities Contains: most of digestive organs, spleen, kidneys, & ureters Anterior Posterior Digestive Tract ▪ The viscera of the abdomen constitute the majority of the digestive tract Abdominal Quadrants ▪ For descriptive purposes, the abdomen is often divided into 4 quadrants by imaginary horizontal & vertical lines crossing at the umbilicus: 1) Right Upper Quadrant Liver, Gallbladder, Pylorus, Duodenum, Hepatic flexure of colon, Head of pancreas 2) Left Upper Quadrant Spleen, Splenic flexure of colon, Stomach, Body & Tail of pancreas 3) Right Lower Quadrant Terminal ileum, Cecum, Appendix, Ascending colon, Right ovary 4) Left Lower Quadrant Descending colon, Sigmoid colon, Left ovary Abdominal Regions ▪ Abdomen can also be divided into 9 regions: 1) Epigastric 2) Right Hypochondriac 3) Left Hypochondriac 4) Umbilical 5) Right Lumbar 6) Left Lumbar 7) Hypogastric/Suprapubic 8) Right Iliac/Inguinal 9) Left Iliac/Inguinal Peritoneum ▪ Peritoneum: 1) Parietal Peritoneum – mesothelium covering inside of abdominopelvic cavity 2) Visceral Peritoneum – mesothelium investing the viscera; continuous with the parietal peritoneum Peritoneal cavity: ▪ Potential space located between parietal & visceral peritoneum; contains a small amount (~50mL) of peritoneal fluid ▪ *Closed in males, but has opening in females allowing for passage of oocytes from the ovaries to fallopian tube Peritoneum ▪ Peritoneum: Mesentery – double layer of peritoneum that encloses an organ & connects it to posterior abdominal wall; provides pathways for nerves, vessels, & lymphatics Peritoneal ligaments – double layer of peritoneum (mesentery) that connects one organ to another or to the abdominal wall Intraperitoneal vs. Retroperitoneal ▪ During embryonic development, abdominal cavity becomes lined with parietal peritoneum, which forms a closed sac → lumen is the peritoneal cavity As viscera develop, they invaginate to varying degrees into peritoneal sac, acquiring a peritoneal covering (visceral peritoneum) A. Retroperitoneal: some viscera (e.g., kidney) protrude only partially remaining external to to peritoneal cavity & posterior to the peritoneum lining the abdominal cavity B. Intraperitoneal: other viscera (e.g., stomach) protrude completely into the peritoneal sac & are almost completely invested by visceral peritoneum Intraperitoneal viscera are connected to the abdominal wall by a mesentery  Intraperitoneal Organs ▪ Intraperitoneal organs – enveloped by visceral peritoneum & attach to abdominal walls via mesentery Liver Tail of pancreas Spleen Stomach Duodenum (*1st part) Jejunum & Ileum Cecum Appendix Transverse colon Sigmoid colon Upper 1/3 of rectum Retroperitoneal Organs ▪ Retroperitoneal organs – covered with parietal peritoneum on anterior surface only Mnemonic: “SAD PUCKER” ▪ Suprarenal glands ▪ Aorta/IVC, ▪ Duodenum (*2nd, 3rd, 4th parts only) ▪ Pancreas (*except tail which is intraperitoneal) ▪ Ureters ▪ Colon (*Ascending & Descending only) ▪ Kidneys ▪ Esophagus ▪ Rectum Organs  Liver ▪ Functions of liver include: Detoxification Glycogen storage Production of hormones Synthesis of plasma proteins Production of bile Liver ▪ Divided into 4 anatomical lobes: 1) Right 2) Left 3) Quadrate 4) Caudate Liver ▪ Liver can be divided functionally divided into 8 surgically-resectable hepatic segments, each supplied by tertiary branches of the portal triad Liver ▪ Bare area – portion of liver in direct contact with diaphragm; NOT covered with visceral peritoneum ▪ Liver ligaments: Anterior & Posterior Coronary ligaments Right & Left Triangular ligaments Falciform ligament ▪ Connects liver to anterior abdominal wall Round ligament (ligamentum teres hepatis) ▪ Fibrous remnant of the umbilical vein Liver ▪ Hepatic portal vein brings 75%-80% of blood to liver Carries nutrients absorbed by GI tract Short, wide vein formed by superior mesenteric vein & splenic vein Terminates by dividing into right & left branches Portal Venous System ▪ Portal venous system transports blood from GI viscera to liver for filtration by way of hepatic portal vein Hepatic portal vein formed by union of superior mesenteric vein & splenic vein Inferior mesenteric vein typically drains into splenic vein Caval Venous System ▪ Caval venous system comprised of inferior vena cava & its tributaries Drains venous blood from structures of posterior abdominal wall, kidneys, suprarenal glands, gonads, pelvic & perineal structures, and lower limbs Blood bypasses liver to enter right atrium of heart IVC located posterior to liver; formed by union of left & right common iliac vv. Portal-Caval Anatomoses ▪ Anastomoses between caval & portal veins provide collateral circulation in cases of obstruction in liver or portal vein Portal-Caval Anatomoses ▪ Portal-Caval Anastomoses: A. Left Gastric vv. – Esophageal vv. B. Superior Rectal vv. – Middle & Inferior rectal vv. Impaired flow in these veins can lead to hemorrhoids C. Paraumbilical vv. – Epigastric vv. Portal obstruction can cause veins of anterior abdominal wall (epigastric vv.) to become varicose & radiate under skin around umbilicus like small snakes → Caput Medusae D. Colic vv. – Retroperitoneal vv. Gallbladder ▪ Gallbladder – stores & concentrates bile, which emulsifies fat during digestion Fundus Body Neck Duct System ▪ Common Bile Duct = Cystic duct + Hepatic duct Common bile duct joins main pancreatic duct to form hepatopancreatic ampulla (ampulla of Vater) ▪ Ampulla opens into 2nd part of duodenum at major duodenal papilla Portal Triad ▪ Portal triad contains: 1) Hepatic portal vein 2) Hepatic artery proper 3) Common bile duct Stomach ▪ Stomach – stores food and chemically & mechanically prepares it for digestion and passage into duodenum Divided into 4 major regions: 1) Cardia – first part of stomach 2) Fundus – dome-shaped superior portion 3) Body – middle section; largest 4) Pylorus – terminal end of stomach Stomach ▪ Stomach: interior Rugae – longitudinal folds of mucous membrane of empty stomach; disappear when distended Cardiac (lower esophageal) sphincter – at junction of esophagus & stomach; prevents reflux of gastric contents into esophagus Pyloric sphincter – located at gastroduodenal junction; prevents reflex of duodenal contents into stomach Stomach: Ligaments ▪ Greater omentum – double-layered peritoneal sheet hanging from greater curvature of stomach 1) Gastrosplenic ligament – connects stomach to spleen 2) Gastrophrenic ligament – connects stomach to inferior surface of diaphragm 3) Gastrocolic ligament – apron-like part of greater omentum; connects stomach to transverse colon Stomach: Ligaments ▪ Lesser omentum – double-layered peritoneal fold that passes from liver to lesser curvature of the stomach & superior portion of duodenum 1) Hepatogastric ligament – sheet-like part; extends between liver & lesser curvature of stomach 2) Hepatoduodenal ligament – thickened free edge; conducts portal triad; extends between duodenum & liver Small Intestine ▪ Small intestine – primary site for absorption of nutrients; comprised of: 1) Duodenum – short (~1ft), C-shaped region 2) Jejunum – ~8ft 3) Ileum – ~12ft Small Intestine: Duodenum ▪ Duodenum – first & shortest part of the small intestine Superior (1st) part – short, mostly horizontal, lies anterolateral to body of L1 Descending (2nd) part – runs vertically along sides of L2 & L3, curving along head of pancreas, contains major duodenal papilla Inferior (horizonal, 3rd) part – crosses anterior to IVC & aorta and posterior to superior mesenteric artery & vein at L3 level Ascending (4th) part – begins to the left of L3 Small Intestine: Jejunum & Ileum Jejunum – most lies within left upper quadrant Ileum – most lies within right lower quadrant Jejunum vs. Ileum Features Jejunum Ileum Plicae circulares Prominent Fewer Arterial arcades Fewer, large loops Many short loops Vasa recta Long Short Small Intestine: Mesentery ▪ Mesentery Proper (mesentery of small intestine) – fan-shaped fold of peritoneum that attaches jejunum & ileum to posterior abdominal wall Contains blood vessels, lymphatics, and nerves supplying jejunum and ileum Pancreas ▪ Pancreas – accessory digestive gland; lies posterior to stomach between duodenum & spleen Produces: 1) Exocrine secretion (pancreatic juice) which enters duodenum 2) Endocrine secretions (glucagon & insulin) Pancreas Head – within C-shaped curve of the duodenum ▪ Uncinate process – projection from inferior part of head; posterior to superior mesenteric artery Neck – short; overlies superior mesenteric vessels Body – to the left of superior mesenteric vessels Tail – closely related to hilum of spleen & left colic flexure  Pancreas: Ducts ▪ Common bile duct – crosses posterosuperior surface of head of pancreas ▪ Main pancreatic duct – begins in tail of pancreas & runs through parenchyma of gland to head, where it merges with common bile duct Pancreatic & bile ducts unite to form a short, dilated hepatopancreatic ampulla → opens into descending (2nd) part of duodenum at major duodenal papilla Large Intestine ▪ Large intestine – absorbs water & electrolytes, produces and absorbs vitamins, & propels feces toward rectum for elimination Cecum (with Appendix) Ascending colon Transverse colon Descending colon Sigmoid colon Rectum Large Intestine ▪ Large intestine characteristics: 1) Omental (epiploic) appendices – small, fatty omentum-like projections 2) Teniae coli – 3 separate bands of longitudinal muscle 3) Hausta – pouch-like appearance caused by contraction of teniae coli Kidneys ▪ Kidneys – remove excess water, salts, wastes from blood; return nutrients & chemicals to blood Lie retroperitoneally on posterior abdominal wall On either side of vertebral column at level of T12-L3 Left kidney slightly more superior than right Kidneys ▪ Kidney surrounded by multilayered capsule: Fibrous capsule – closely applied to surface of kidney Perinephric fat – surrounds kidneys and suprarenal glands; continuous with fat in the renal sinus Renal fascia – membranous layer that encloses kidneys, suprarenal glands, & perinephric fat Paranephric fat – extraperitoneal fat of lumbar region; external to renal fascia Kidneys ▪ Cortex ▪ Medulla Renal Pyramid ▪ Renal papilla Renal Column ▪ Renal sinus ▪ Renal hilum ▪ Minor calyx ▪ Major calyx ▪ Renal Pelvis ▪ Ureter Blood Supply Foregut, Midgut, Hindgut ▪ Gut tube: 1) Foregut – Esophagus, Stomach, Liver, Gallbladder, Pancreas, Upper Duodenum Celiac Trunk 2) Midgut – Lower duodenum, Jejunum, Ileum, Cecum, Appendix, Ascending Colon, Proximal 2/3 Transverse Colon Superior Mesenteric Artery 3) Hindgut – distal 1/3 Transverse Colon, Descending Colon, Sigmoid Colon, Rectum, Upper Anal Canal Inferior Mesenteric Artery Celiac Trunk ▪ Celiac Trunk – arises from abdominal aorta at T12 1) Left gastric artery 2) Splenic artery 3) Common hepatic artery  Celiac Trunk 1) Left gastric 2) Splenic Left Gastro-omental (Gastroepiploic) Short gastric 3) Common hepatic Hepatic artery proper ▪ Right gastric Gastroduodenal ▪ Right gastro- omental (gastroepiploic) Celiac Trunk Superior Mesenteric Artery ▪ Superior Mesenteric Artery – arises from abdominal aorta at L1; runs between the layers of the mesentery 1) Ileocolic 2) Right Colic 3) Middle Colic 4) Intestinal arteries Superior Mesenteric Artery Superior Mesenteric Artery ▪ Intestinal arteries – 15-18 branches to jejunum & ileum Unite to form loops called arterial arcades, which give rise to straight arteries called vasa recta Inferior Mesenteric Artery ▪ Inferior Mesenteric artery – arises from abdominal aorta at L3 1) Left colic artery 2) Sigmoid arteries 3) Superior Rectal artery Marginal artery (of Drummond) – anastomotic connection between Superior & Inferior Mesenteric arteries Inferior Mesenteric Artery Abdominal Vasculature: Veins Innervation GI Tract Innervation ▪ Sympathetic Inhibits peristalsis Constricts blood vessels to GI tract so blood is available to skeletal muscle Contracts internal anal sphincter to aid fecal continence Promotes breakdown of glycogen to glucose (increased energy) ▪ Parasympathetic Promotes peristalsis and secretion of digestive juices Contracts rectum, inhibits internal anal sphincter to cause defecation Promotes building/conservation of glycogen Increases secretion of bile Autonomic Nervous System ▪ Autonomic nervous system is a two-neuron system: Presynaptic neuron – within CNS Postsynaptic neuron – within PNS (in autonomic ganglia) Autonomic Plexuses ▪ Autonomic Plexuses – large collections of sympathetic & parasympathetic efferents, along with visceral afferents; branches from these plexuses innervate viscera Thorax: ▪ Cardiac ▪ Pulmonary ▪ Esophageal Abdomen & Pelvis: ▪ Abdominal aortic (celiac, superior mesenteric, inferior mesenteric, suprarenal & renal) – surround abdominal aorta & major branches ▪ Superior Hypogastric plexus – carries autonomic innervation for hindgut & pelvic viscera ▪ Inferior Hypogastric plexus – carries autonomic innervation to pelvic & perineal organs Splanchnic Nerves ▪ Splanchnic nerves – paired nerves that carry both visceral efferent (autonomic) & visceral afferent fibers to/from organs of the body cavities ▪ SYMPATHETIC Cardiopulmonary – postsynaptic sympathetic Abdominopelvic – presynaptic sympathetic ▪ Greater splanchnic ▪ Lesser splanchnic ▪ Least splanchnic ▪ Lumbar splanchnic ▪ Sacral splanchnic ▪ PARASYMPATHETIC Pelvic – presynaptic parasympathetic Sympathetic Nervous System ▪ Sympathetic (thoracolumbar) division: “fight or flight” A. Presynaptic neuron: within CNS → Lateral horn of spinal cord (T1-L2) B. Postsynaptic neuron: ▪ Paravertebral ▪ Prevertebral ganglia Sympathetic Ganglia: Prevertebral ▪ Prevertebral (preaortic/collateral) ganglia Located in plexuses that surround the origins of the main branches of the abdominal aorta Contain postganglionic neurons that innervate the abdominal viscera Sympathetic Ganglia: Prevertebral ▪ Prevertebral (preaortic/collateral) ganglia: 1) Celiac ganglion 2) Aorticorenal ganglion 3) Superior mesenteric ganglion 4) Inferior mesenteric ganglion Splanchnic Nerves: Sympathetic ▪ Abdominopelvic splanchnic nerves Presynaptic sympathetic fibers involved in innervation of viscera of abdominopelvic cavity pass to the prevertebral ganglia through abdominopelvic splanchnic nerves Splanchnic Nerves: Sympathetic ▪ Abdominopelvic splanchnic nerves Presynaptic sympathetic fibers of abdominopelvic splanchnic nerves synapse in prevertebral ganglia Postsynaptic fibers form periarterial plexuses, which follow branches of abdominal aorta to reach their destinations Abdominopelvic Splanchnic Nerves ▪Abdominopelvic splanchnic nerves – presynaptic sympathetic fibers innervating viscera of abdominopelvic cavity: 1) Thoracic splanchnic nerves Greater, Lesser, Least 2) Lumbar splanchnic nerves Abdominopelvic Splanchnic Nerves 1)Thoracic splanchnic nerves: Greater splanchnic n. – originates at T5-T9 ▪ Synapses in Celiac ganglion ▪ Postganglionic fibers distribute to foregut structures Lesser splanchnic n. – originates at T10-T11 Renal Plexus ▪ Synapses in Superior Mesenteric Aor ticoren al gan glion ganglia ▪ Postganglionic fibers distribute to midgut structures Least splanchnic n. – originates at T12 ▪ Synapses in Aorticorenal ganglia; contributes to renal plexus *Postganglionic fibers form periarterial plexuses, which follow branches of abdominal aorta to reach their destination Abdominopelvic Splanchnic Nerves 2)Lumbar splanchnic nerves – originate from L1-L2/L3 Synapses in inferior mesenteric ganglion Postganglionic fibers distribute to hindgut structures *Postganglionic fibers form periarterial plexuses, which follow branches of abdominal aorta to reach their destination Innervation: Sympathetic Parasympathetic Nervous System ▪ Parasympathetic division Presynaptic neuron 1) Brainstem cranial nerve nuclei 2) Sacral region of spinal cord (S2-S4)) Postsynaptic neuron: 1) 4 ganglia within head (Ciliary, Pterygopalatine, Submandibular, Otic) 2) Postsynaptic cell bodies located near organ or within organ walls Parasympathetic Nervous System ▪ Cranial outflow – provides innervation to head, as well as thoracic & abdominal viscera Head – via CN III, VII, IX Thorax – via CN X Abdomen – via CN X (*foregut & midgut) ▪ Sacral outflow – supplies hindgut (distal GI tract) & pelvic viscera via pelvic splanchnic nerves Ganglia: Parasympathetic ▪ Parasympathetic: Head Ganglia – Ciliary, Pterygopalatine, Submandibular, Otic Terminal or Intramural ganglia – ganglia near to (terminal) or within (intramural) wall of target organ Abdomen: Parasympathetics ▪ Parasympathetic innervation of Abdomen supplied by two nerves: Vagus nerve – esophagus to splenic flexure (foregut & midgut) Pelvic splanchnic nerves – descending colon, sigmoid colon, rectum (hindgut) ❖ Presynaptic fibers synapse with postsynaptic cell bodies near or within the wall of the target organ (intrinsic/enteric ganglia) Abdomen: Vagus Nerve ▪ Parasympathetic innervation of foregut & midgut (esophagus to left colic flexure) via CN X: Preganglionic fibers carried in anterior & posterior vagal trunks Postganglionic cell bodies: near or within walls of viscera Pelvic Splanchnic Nerves ▪ Parasympathetic innervation to distal GI tract (hindgut) & pelvic viscera is supplied via pelvic splanchnic nerves Pelvic Splanchnic Nerves ▪ Pelvic Splanchnic Nerves Presynaptic cell bodies located within sacral spinal cord (S2-S4) Presynaptic fibers arise from anterior rami of spinal nerves S2-S4 Pelvic Splanchnic Nerves ▪ Pelvic Splanchnic Nerves Presynaptic fibers distribute to inferior hypogastric plexus (majority) or superior hypogastric plexus From plexuses, presynaptic fibers reach target organs via periarterial plexuses; synapse on ganglia within organ walls Questions? 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