Boundaries of the Abdominal Cavity

ABDOMINAL CAVITY Boundaries of the abdominal cavity ● Superior = diaphragm ● Inferior = pelvic brim (iliac crests) ● Anterior = anterior abdominal wall ● Posterior = posterior abdominal wall and vertebral column Surface anatomy ● ● ● ● Hypochondriac ○ Under the cartilage of the ribs ○ 'breast bone' ○ Below the cartilage of the thoracic region Hypogastric region ○ Upon the stomach Lumbar regions ○ Where the lumbar vertebrae start Umbilical region ○ Midpoint of the abdominal region ● Iliac region ○ Can feel the iliac crests when you put your hands on your hips Abdominal cavity subdivisions (peritoneal and subperitoneal) Peritoneal cavity ● Peritoneal is most anterior ● Covered in brown peritoneum (serous membrane) ● Intraperitoneal = Peritoneum completely surrounds the digestive organs on all surfaces Retroperitoneal cavity ● Most posterior ● Not covered in peritoneal structure ● Space behind the organs which are covered in peritoneum ● Predominantly urinary and some digestive organs ● Retroperitoneal organs lie on the posterior abdominal wall Peritoneum ● Serous sac that lines the abdominal cavity ● Lines the organs in the peritoneal cavity ● Two layered structure but the layers are continuous (visceral and parietal) ● Parietal = body wall ● Visceral = organ Intraperitoneal vs retroperitoneal Intraperitoneal - Have blood vessels that need to be protected as they go to the organ Extend to the posterior abdominal wall E.g. liver, small intestine, stomach, spleen Or have to undergo lots of twisting, peristalsis, churning Need to move around on each other to propel the food through the tube Not fixed to the body wall Mobility in the abdominal cavity and contains them within the abdominal cavity ALL INTRAPERITONEAL ORGANS ARE COVERED IN: ○ Visceral peritoneum ○ Attached to a mesentery ○ Or attached to an omentum Retroperitoneal - - - - Fixed to the body wall Moving increases risk of kinking, blocking or tearing blood vessels or structures going to that region Pancreas pierces into the duodenum to secrete digestive juices If they can move, you would risk breaking the connection between the duodenum and the pancreas This part of the large intestine stays stable, the other parts are moveable, if this moves = risk of a knot These fixed parts (lateral parts of the large intestine) are fixed to decrease the risk of knots Mesentery ● Peritoneum that extends forward into free space and is not attached to anything ● Fan shaped ● Extends from the posterior abdominal wall ● Functions ○ Controls the extent of movement within the abdominal cavity ○ Protects blood vessels ● Anchors jejunum and ileum (mesentery proper) and transverse and sigmoid colon (mesocolon) to the posterior abdominal wall Mesentery proper ● When it gets to the abdominal aorta it will extend anteriorly where the parietal peritoneum changes to mesentery ● Fan shaped where it extends from the abdominal aorta and branches out ○ Narrow root and then fans forward Mesocolon ● That part of the colon can move around and perform peristaltic movements to contract and push the food through that part ● How far the part of the colon can move is based on the length of the mesentery Mesentery proper = small intestine Mesocolon = large intestine/colon Omentum = stomach Attached to the wall = parietal Attached to the organ = visceral Omentum ● Double fold of peritoneum ● Greater = extends from the greater curvature (bottom) of the stomach to the transverse colon - Most anterior structure in the abdominal cavity - Extends down towards the pubic bones but folds back on itself and attaches to the transverse part of the large intestine - Function = cushioning and increasing the distance between the abdominal wall and external environment (no bony casing) - Can migrate to areas of the peritoneal cavity where there is disease/cancer/infection and wrap itself around that particular structure and compartmentalise the disease from the rest of the body ● Lesser = extends from the lesser curvature (top) of the stomach to the liver - Compartmentalise the space in the retroperitoneal cavity - Compartment behind the peritoneal structures especially the liver and stomach - Peritoneum because it extends from the stomach