Peritoneum is the serous membrane which lines the abdominal cavity and a part of pelvic cavity and the organs contained in them
In the male, it is completely closed one. In the female there are two small openings in it, and these are abdominal openings of the oviducts
The peritoneum, which covers the parieties, is called parietal peritoneum, which is reflected over the contained organs, the visceral layer of peritoneum
The peritoneal cavity is a potential space formed between two layers, parietal and visceral, which are normally in contact with each other
It contains a thin film of serous fluid that acts as a lubricant. Though the peritoneal cavity as a whole is single, it is divisible in to two sacs
The greater sac is exposed when the inferior wall of the abdomen is cut through
The lesser sac forms only diverticulum of the greater sac, which envelops the intestines
The two sacs are continuous with each other through the foramen of Winslow or epiploic foramen
The peritoneum gets reflected on the organs contained in the cavity to form their outermost covering
It then extends into a number of folds, which extend between the various organs or connect them to the walls
These folds serve to hold the organ in position and also to enclose the vessels and nerves passing through them. They are as follows,
A double fold passing from the stomach to the other viscera is an omentum E.g.. greater omentum
A double fold that attaches the intestine to the dorsal abdominal wall is mesentery E.g.. common mesentery of ox and dog
A double fold, which attaches viscera other than parts of the digestive tube to the walls, is ligament, E.g.., ligament of liver
Omentum and mesentery transmit blood vessels and nerves to the organ whereas a ligament does not, except the broad ligament of the uterus
Peritoneum as a whole
Tracing the peritoneum as a whole, we may consider it as consisting of two sacs a greater and a lesser
The greater sac lines the greater part of the abdominal cavity and covers most of the viscera, which have a peritoneal investment
The lesser sac formed by the two layers of greater omentum, is an introversion or invagination of the greater sac, formed during the development of the viscera
The cavity of the greater sac is termed general peritoneal cavity
The cavity of the lesser sac is the omental cavity – a potential space, similar to the general peritoneal cavity
The two cavities communicate by a relatively narrow passage termed the epiploic foramen (foramen of Winslow). This opening is situated on the visceral face of liver
It is almost sagittal in direction, formed between caudate lobe of liver dorsally and portal vein and pancreas ventrally
Its walls are normally in contact and the passage merely a potential one.
We may now trace the peritoneum in a longitudinal direction beginning in front
It is reflected from the ventral abdominal wall and the diaphragm upon the liver forming the ligaments of the liver and its serous coat
It leaves the liver as lesser omentum and becomes continuous with the mesoduodenum and greater omentum
From the dorsal abdominal wall it is reflected on the rumen and spleen to form their serous coat and greater omentum on the left
The reflection from the dorsal abdominal wall in the midline forms the common terminal part of the colon in the sublumbar region and the rectum in the pelvic cavity forming the mesocolon and mesorectum respectively
It is then reflected from the rectum to the dorsal surface of the bladder to form the genital fold (broad ligaments in the female) and passes to the body wall laterally and ventrally to form the lateral and middle ligaments of the bladder. In the newborn, the following folds are very large
The falciform ligament of liver extends to the umbilicus, and contains in its free edge the large umbilical vein
The bladder at this time an abdominal organ has a ventral median fold, which connects it and the umbilicus and contains the large umbilical artery
Omentum
These are two in number -the greater and the lesser
The greater omentum conceals the greater part of the intestine on the right side except duodenum and covers the ventral sac of the rumen almost entirely
It is composed of two layers,
The superficial layer extends from the left longitudinal groove of the rumen, curves ventrally around the ventral sac of the rumen, and ascends to the right side covering the deep layer of the omentum. It ends along the second part of the duodenum and the greater curvature of the abomasum
The deep layer is attached along the visceral surface of the rumen ventral to the right longitudinal groove of the rumen and curves around the intestinal mass on the right side and is covered by the superficial part. It ends chiefly by blending with the medial layer of meso-duodenum but cranially it is attached on the first bend of the colon and the visceral surface of the liver along the ventral border of the pancreas. The two parts are continuous at the attachment along the caudal transverse groove of the rumen
The superficial and deep layers thus enclose a potential space, the omental bursa. The greater omentum stores considerable amount of fat
The lesser omentum is a double fold extending from the liver (oesophageal notch to portal fissure) to the parietal surface of the omasum, pyloric part of the abomasum and the first part of duodenum
