بسم االه الرحمن الرحيم

MAY 3, 2012 [POSTERIOR ABDOMINAL WALL] LECTURE 26 ANATOMY Quick Revision: بسم االه الرحمن الرحيم Last time we started with the anterior abdominal wall and said that: 1. Diaphragm is the root of the abdomen. 2. The anterior abdominal wall is covered with 4 muscles **So now we will start with the posterior abdominal wall. Muscles: We only need to know the numeration of the muscles that make up the posterior abdominal wall: 1. Upper 1/3 is made up of the diaphragm (we said that the diaphragm is dome shaped that s why it also takes part in the posterior wall) Then I go down to find three muscles: (medial to lateral) 2. The most medial one is the Psoas major (will be taken in details in the lower limb) 3. The second one is the Quadratus lumborum (rectangular in shape and located in the lumber region) 4. Most lateral muscle Transversus abdominis (the deepest muscle of the anterior wall) Abdulruhman Azzam Page 1

** After covering the perimeter of the abdomen let us start with the contents of the abdomen. Abdominal Aorta: 4 major points: Note: It is called the common iliac artery because each one of them will branch into two arteries the external (main blood supplier for the lower limb) and internal (main blood supplier for the pelvis) iliac arteries. 1. Origin: continuation of the descending thoracic aorta. 2. Course: lies directly in the midline, anterior to the lumber vertebrae and the anterior longitudinal ligament. (L1-L4) 3. End: branches at the 4 th lumber vertebrae into two arteries- the right and the left common iliac arteries. 4. Branches: divided into single branches and paired branches Branches: ~Single branches go to single organs and the only single organs in the abdomen are the gut organs (gastrointestinal tract: stomach small intestines- large intestines). Usually trunk stands for a short artery that gives a lot of branches. Mesenteric: related to the intestines a. First one of the single branches is the celiac trunk. Starts opposite to the upper border of L1. Gives three branches: 1. Left side: gastric branch 2. Right side: hepatic branch 3. Splenic branch b. The second one from the single branches is the superior mesenteric. Starts opposite to the lower border of L1. c. The third one is the inferior mesenteric. Starts opposite to the border of L3. Note: When the embryo folds cephalocaudally it took part of the amnion and the yolk sac and made the gut that evolves into the gastro intestinal tract. The gut is divided into three parts depending on its location in the embryo: the foregut (forehead), the midgut (middle part), and the hindgut (tail). As the embryo is growing each part of the gut would require arterial supply, so the celiac supplies the foregut, the superior mesenteric supplies the midgut, and the inferior mesenteric supplies the hindgut. This organization evolves with us as we grow and organs develop. Abdulruhman Azzam Page 2

~Paired branches go to paired organs: 1. First pair supplies the diaphragm and is called the phrenic arteries. 2. Second pair is the renal arteries, opposite to the border of L2. 3. The third is the suprarenal arteries 4. The fourth is the gonadal arteries (testicular or ovarian) 5. Common iliac arteries Inferior Vena Cava: Again 4 major points: 1. Origin: Union of the two common iliac veins opposite to L5. 2. Course: Directly anterior to the vertebral column at the right side of the abdominal aorta. 3. End: Passes through the central tendon of the diaphragm through the opening for the inferior vena cava till it reaches the right atrium. 4. Tributaries: equal to the paired branches of the abdominal aorta. (gonadal- suprarenal- renal) ~Now you have collected the venous drainage from the paired branches, but what about the single branches? ~The single branches from the aorta fed the gastrointestinal tract (stomach- small intestines- large intestines); however, another venous circulation is responsible for these organs, the portal circulation. So the question remains, why? *The answer is simple; the organs they drain from collect the nutrients the body needs and these nutrients need to be processed, so instead of going to the inferior vena cava they drain into the portal Abdulruhman Azzam Page 3

vein that goes to the liver for the processing of the absorbed substances. The waste products of the liver drain into the hepatic veins, which in turn drain into the inferior vena cava. Tributaries: ~Now we will differentiate between the tributaries that are entering from the right and left side directly into the inferior vena cava: 1. The common iliac veins: the inferior vena cava takes from the right and the left common iliac veins. 2. Gonadal veins: the inferior vena cava takes only from the right gonadal vein, and the left gonadal vein goes to the left renal vein. 3. Renal veins: Right and left renal veins drain directly into the inferior vena cava 4. Suprarenal veins: the right suprarenal vein will drain directly into the inferior vena cava and the left suprarenal vein will drain in the left renal vein. Note ~So why this difference in the left and right gonadal and suprarenal attachments? *The venous drainage that is coming back from the testes doesn t drain well, so the blood stays trapped inside the gonadal veins and this causes a case of testicular varicocele.(دواليالخصيتين) This happens because: a. The transverse colon presses on the left side of the renal vein b. The left suprarenal vein drains into the left renal vein, and the left suprarenal releases catecholamines, and these catecholamines restrict the size of the vessels. Abdulruhman Azzam Page 4

Divisions of the Abdomen: ~The abdomen is divided into 9 areas, and each area is occupied with one or more certain organs. ~When a Dr. taps a certain region and hears a resonance he knows it s the end of an organ if there was no resonance then he is tapping on an organ. By this a Great Dr. can draw a map of the organs on the patient, and know if a certain organ is enlarged, shrunk, or if it s normal. زي لما تيجي تشتري البطيخة P: ~ The two longitudinal lines go from the mid-inguinal point till the mid-clavicular point. ~The upper horizontal line is called the subcostal line; it s at the level of L3 ~The lower horizontal line is called the intertubercular plane; why? Because it lies on the tubercles of the hip bone. It lies at the level of L5. Abdulruhman Azzam Page 5

Peritoneum: ~Like the pleura (first body cavity) and the pericardium (second body cavity) the peritoneum (third body cavity) is a sac that is found in the abdomen. When we were babies it was like an empty balloon. All the abdominal organs formed on the posterior abdominal wall, depending on the size of the mature organ we will know if it s invaginated by the peritoneum or not. For example the liver, a large organ, is completely invaginated in the peritoneum. A small organ will stay on the posterior abdominal wall and will not be covered by the peritoneum; we call such organs retroperitoneal organs. ~In summery we only have to know three points: 1. Peritoneum is the third body cavity 2. Large organs in the abdomen are invaginated by the peritoneum 3. Small organs in the abdomen that are not covered by the peritoneum are called retroperitoneal organs Abdulruhman Azzam Page 6

Stomach: ~Position: Found in the epigastric region and the left hypochondriac region. ~Has two openings: a. cardiac opening (continuous with the esophagus) b. Pyloric opening (continuous with the small intestines) ~Borders: -Right border: greater curvature -Left border: lesser curvature ~Surfaces: *Anterior surface: relations- part of the diaphragm and the left lobe of the liver. relations- spleen (makes anterior and posterior relations because of its position). ~Stomach bed (posterior surface) is composed of: 1. Part of the diaphragm 2. The left kidney 3. Left suprarenal 4. Pancreas: with the splenic artery lying on its upper border 5. Transverse colon ~The stomach s inside wall is lined with mucosa; these form ridges called Gastric Rugae (increase surface area of stomach). ~Blood supply: the stomach is a derivative of the foregut so it takes blood from the celiac trunk. ~Venus drainage: Portal circulation. ~Innervation: the stomach is a smooth involuntary muscle so it takes its nerve supply from the autonomic nervous system: *sympathetic: inhibitory for the wall (relaxant of the wall and closes the sphincter). Nerve of storage and relaxation *parasympathetic: gastric nerves that come from the vagus nerves Nerve of contraction and evacuation The End Abdulruhman Azzam Page 7

I hope you find this sheet clear and useful This is a poem I ve written for this semester, hope you like it: A journey of 6 A blight some may say But for us it s bliss A choice we all made with content Although at times this choice we will contempt Second semester with subjects completely new Let us see what we have all been through From football matches to need for speed A stress outlet that we all seem to need From the Lajneh to the correction team A chosen few whom we all consider to be supreme From sheets to slides that we all now hate To a group fueled with a fiery debate From the head of the humerus to its distal end Endless muscles on which all our time we seem to spend From embryo we now need rest Before our heads spin east and west From alkenes to the benzene ring The constant headache they surely bring Few weeks left till the final test In which everyone will do his best A bumpy path we all now travel With surprises on each turn for us to unravel Abdulruhman Azzam Page 8