LECTURE 11 & 12: ABDOMINAL VISCERA

ABDOMINAL CONTENTS

DIVISION

The location of abdominal viscera is divided into 4 quadrants:

- horizontal line across the umbilicus divides the upper quadrants from the lower quadrants - vertical line from the ziphisternum through the umbilicus to the pubic symphysis divides the right quadrants from the left quadrants

OESOPHAGUS

- ~25cm long muscular tube that traverses the neck, thorax and abdomen o Transfer of food through peristalsis - Begins at the cricoid cartilage at C6, and then descends behind the trachea into the posterior mediastinum - Descent into the abdomen is through the oesophageal hiatus in the diaphragm (T10) which is made from a sling of the left crus on the right side o Diaphragmatic contraction closes the oesophageal hiatus and blocks the reflux of gastric contents - Enters the stomach on the right side - Oesophagus is lined by stratified squamous epithelium which abruptly changes into gastric mucosa at the gastro-oesophageal junction - Oesophagus has natural narrowing points along its entire length with specific vessel supply o Cervical . Upper oesophageal sphincter (narrowing) . Inferior thyroid artery (arterial) . Brachiocephalic and systemic (venous) . Deep cervical nodes o Thoracic . Aortic arch and left main bronchus (narrowing) . Oesophagus branches from descending aorta (arterial) . Azygous and systemic (venous) . Mediastinal nodes

o Abdomen . Oesophageal hiatus (narrowing) . Left gastric from aorta (arterial) . Left gastric portal with overlaps from systemic (venous) . Pre-aortic nodes

HIATUS HERNIA

It is not uncommon for herniation of the stomach to occur at the oesophageal hiatus:

- Paraosoeosophageal hiatal herniation is one sided (5%) - Sliding hiatial herniation when a portion of the stomach is pulled upwards

STOMACH

- Located in the LUQ - J shaped organ o Less curvature is on the medial side o Greater curvature on the lateral side - Two openings o Cardiac orifice is the point in which the oesophagus enters (proximal part of lesser curvature) o Pyloric orifice is the distal opening - Fundus is a domed shaped projection above the stomach o Full of gas - Body of the stomach o Extends from the cardiac notch to the angular notch in the lesser curvature - Pyloric antrum is a funnel from the body into the pylorus (most tubular part of the stomach) o Pylorus is characterised as a strong muscular tube that functions as the pyloric sphincter . The lumen travelling through is called the pyloric canal - Organ is tether to the under surface of the liver from the less curvature by a mesentery called the lesser omentum, the greater curvature of the stomach is anchored in the posterior abdominal wall by a the greater omentum - Rugae are internal folds within the stomach which are most prominent at the pylorus ARTERIAL BLOOD

- Lesser curvature has a right and left gastric artery which richly anastomose - Greater curvature has a right and left gastroepiploic artery which also richly anastomose

DUODENUM

- First part of the small intestine as a C shaped loop (10 inches in total) that encloses the pancreas - Only the very first portion of the duodenum connecting to the stomach is intraperitoneal, whilst the remainder is retroperitoneal - Primary function of digestion and absorption - Duodenum is divided into 4 parts: o Duodenal cap is the first portion and is directed upwards and backwards over the right crus, right psoas major and hilum of the right kidney (2 inches) . Peptic ulcers will usually occur here o Vertical descending portion is completely retroperitoneal (3 inches) . Transverse mesocolon is a landmark found here that encapsulates the transverse colon . Choledochoduodenal junction if found half way down inside  Major duodenal papilla is where the bile duct pancreatic duct enters  Minor duodenal papilla is the accessory duct to pancreas o Horizontal part of the duodenum traverses right psoas to left psoas (4 inches) . Slightly tethered to left psoas . Found at the level of L3 . Root of the mesentery found here which anchors the jejunum and ileum o The final portion curves upwards on left psoas and comes forward . Duodenal-jejunal flexure marks the point the small intestine becomes intraperitoneal with the jejunum JEJUNUM AND ILEUM

- 4-6 metres in length o 2/5 is jejunum and 3/5 is ileum with no clear demarcation o Jejunum tends to be in the situated in the LUQ and is larger in diameter with thicker walls and higher degree of folding o Ileum is in the RLQ - Completely intraperitoneal and suspended by mesentery o Attachment to the posterior abdominal wall and 3 part of the duodenum o Blood supply from the aorta feeds the small intestine by entering the mesentery

ARTERIAL BLOOD SUPPLY

- Jejunum is supplied by vasarector which arise from a few arcades (long arterial loops) - Ileum has an abundance of arcades and much smaller vasarector compared to jejunum

LARGE INTESTINE

- The start of the large intestine is at the ileo- caecal junction o Ileo-caecal valve is a smooth muscle sphincter to this opening - 1.5 metres in length o Caecum, ascending colon (right colic/hepatic flexure), transverse colon (left colic/splenic flexure), descending colon, sigmoid colon (s-shaped bend), and the final centred portion is the rectum (one continuous longitudinal muscle) - Unlike the small intestine which is a single longitudinal muscle coat, the large intestine consists of three distinct muscle bands called tinea o The short banding gives the large intestine a stacked appear which is termed haustra - The large intestine has characteristic fat tags called epiploic appendices hanging off it

APPENDIX

- Found projecting off from the caecum at the point in which the three tinea converge - The tip of the appendix is variable in length o 1/5 are found hanging off in the pelvic brim = pelvic appendix o Most are found tucked behind the large intestine = retrocaecal appendix

LIVER

- Largest solid viscera found tucked up behind the costal margin - Fills the RUQ - The anterior surface is smooth and is called the diaphragmatic surface o Its transition into the visceral surface is demarcated by the sharp inferior border o Divided into two lobes by a falciform ligament (double folded peritoneum) that connects the liver the anterior abdominal wall at the level of umbilicus . Ligametum teres is an obliterated vein and runs inferiorly  Remnant of umbilicus vein that used to receive blood from the placenta - From the anterior surface the liver is divided into one large right lobe and one small left lobe, but both are functionally identical - The visceral surface is imprinted by all the structures it sits on and bears the hilum o H shaped fissure further divides the liver into a caudate and quadrate lobe o Gall bladder also found next to the quadrate lobe o IVC is found attached to the liver next to the caudate lobe o Ligamentum venosum is a remnant of the ductum venosum that drained directly into the hepatic vein (and then the IVC) HEPATIC HILUM/PORTA HEPATIS

- Hepatic artery is divided into left and right to supply each functional half of the liver (left of hilar) - Hepatic duct divides in half to collect bile products from both halves of the liver (right of hilar) - Portal vein receives blood from the digestive system(middle of hilar and behind the arteries ducts) o The hepatic vein is responsible for draining the viscus directly into the IVC

GALL BLADDER

- Sits a groove on the visceral surface of the liver - Fundus of the gall bladder it its bottom which narrows to form the body; further narrowing produces the neck and continues as a duct (cystic duct) to the common hepatic duct - Cystic duct and hepatic duct converge to form the common bile duct which runs between the pancreas and duodenum, before joining with the pancreatic duct and emptying at the major duodenal papilla o the opening of the papilla is controlled by a complex sphincter, hepatopancreatic ampulla, that closes when inactive to allow the accumulation of bile into the gall bladder

PANCREAS

- organ both exocrine and endocrine functions - functionally broken up into the head, neck, body and tail o head fills the C shaped curve of the duodenum and has an unicinate process that is a landmark for the superior mesenteric vessels o body overlies the DJ flexure but is deep the pylorus of the stomach o the tail leads to the hilum of the spleen - the main pancreatic duct will empty into via the major duodenal papilla, but the accessory duct will empty at a more proximal at the minor duodenal papilla to drain the uncinated process

SPLEEN

- Oval shaped organ about the size of a clenched fist (tend to atrophy over time) in the LUQ o The spleen overlies ribs 9-11 - Smooth diaphragmatic surface o Smooth surface is usually demarcated from the visceral surface by notches on the margin - The visceral surfaces bears the impressions of the stomach and kidneys o Hilar is found on this side . Splenic artery and splenic vein  Splenic artery follows the superior border of the pancreas