Changes

 

==Introduction==

==Introduction==

The peritoneum is the serous membrane which lines the abdominal cavity. It lies directly beneath the abdominal musculature (rectus abdominis and transverse abdominis). It is a type of '''loose connective tissue''' covered by '''mesothelium'''. Extensions of the peritoneum form the mesenteries that support the abdominal contents. It functions to lubricate abdominal viscera, enhance immune responses and wall off infection in the abdomen to prevent peritonitis.

The peritoneum is the serous membrane that lines the abdominal cavity. It lies directly beneath the abdominal musculature (''rectus abdominis'' and ''transverse abdominis''). It is a type of '''loose connective tissue''' and is covered by '''mesothelium'''. Extensions of the peritoneum form the mesenteries, omenta and ligaments that support the abdominal contents. The peritoneum produces fluid to lubricate abdominal viscera. The peritoneum also enhances immune responses and walls off infection in the abdomen to prevent [[Peritonitis|peritonitis]].

 

 

In the early embryo, the primitive gut tube is suspended by the dorsal and ventral mesogastria. The mesogastria divide the embryo into two cavities, called the left and right coelomic cavities. The ventral mesogastrium atrophies caudal to the pylorus of the [[Monogastric Stomach - Anatomy & Physiology|stomach]] and cranial to the [[Rectum - Anatomy & Physiology|rectum]]. This gives the entire [[Small Intestine Overview - Anatomy & Physiology|small intestine]] and most of the [[Large Intestine - Anatomy & Physiology|large intestine]] large scope for expansion and rotation. It also allows the left and right coelomic cavities to coalesce forming one cavity; '''the peritoneal cavity'''. Peritoneal structures develop from the dorsal and ventral mesogastria.

==Structure & Histology==

==Structure & Histology==

*The peritoneum is smooth and clear in the healthy animal.

 

*It consists of a thin layer of loose connective tissue covered by a single layer of [[Mesothelial cells|mesothelial cells]]. Collectively, the connective tissue and peritoneum are referred to as the '''serosa'''.

Lining the abdomen is a thin layer of loose connective tissue covered by a single layer of [[Mesothelial cells|mesothelial cells]]. The layer of mesothelial cells is referred to as the '''peritoneum'''. Collectively, the connective tissue and peritoneum are referred to as the '''serosa'''. Mesothelial cells are simple squamous and of mesodermal origin, they have microvilli on their surface and are very fragile but regenerate very quickly. A small amount of fibroelastic tissue is present within the connective tissue layer to provide support. There are two layers of peritoneum lining the abdomen. Lining the abdominal wall is the '''parietal layer''', lining the abdominal viscera is the '''visceral layer'''. The small space within these two layers is called the '''peritoneal cavity'''.

**Mesothelial cells are simple squamous and of mesodermal origin.

 

**A small amount of fibroelastic tissue is present within the connective tissue layer to provide support.

*There are two layers of peritoneum lining the abdomen.

 

**The layer in contact with the abdominal wall is called the '''parietal layer'''.

A small evagination extends into the thorax along the right side of the [[Oesophagus -  Anatomy & Physiology|oesophagus]]. The peritoneum also evaginates to extend into the inguinal canals. Fat is often stored beneath the peritoneum. Many species have [[Lymphatic System Overview - Anatomy & Physiology|lymphoid tissue]] aggregates and fixed phagocytes in the omentum that are not covered by mesothelial cells. The peritoneum is smooth and clear in the healthy animal.

**The layer covering the abdominal viscera is called the '''visceral layer'''.

 

**The small space within these two layers is called the '''peritoneal cavity'''.

''NB: Post mortem change and autolysis result in increased volumes of red-brown fluid in the abdomen, not associated with other pathology, nor roughening of surfaces of organs or peritoneum.''

*Many species have lymphoid tissue aggregates and fixed phagocytes in the omentum that are not covered by mesothelial cells

 

*''NB Post mortem change and autolysis result in increased volumes of red-brown fluid in the abdomen, not associated with other pathology, no roughening of surfaces of organs or peritoneum.''

===Peritoneal Fluid===

===Peritoneal Fluid===

*In equilibrium with plasma but doesn't contain high molecular weight molecules like fibrinogen.

 

A small quantity of peritoneal fluid is produced by mesothelial cells. It fills the potential space formed by the two layers of peritoneum and allows the two layers to slide over each other freely. Peritoneal fluid is also produced as a [[transudate]] which coats the serosal surface of viscera to facilitate frictionless movement e.g. during peristalsis. It is in equilibrium with plasma but doesn't contain high molecular weight molecules like fibrinogen. The fluid is constantly being produced and resorbed through the large surface area of the peritoneum, for this reason drugs are sometimes administered by intraperitoneal injection. Bacterial toxins are also absorbed readily and can cause inflammation of the peritoneum; ''[[Peritonitis|peritonitis]]''.

==Function==

==Function==

==Vasculature==

 

==Types of Peritoneum==

 

 

 

 

 

The '''suspensory ligament''' - from the [[Ovary - Anatomy & Physiology|ovary]] to the abdominal wall.

*High fibrinolytic activity - protects against the formation of adhesions

*Show reactive change with [[Peritoneal cavity - inflammatory|inflammation]] or [[Peritoneal cavity - effusions|effusions]]

==Species Differences==

*Peritoneum is normally smooth and clear,  

 

*Small volume of clear fluid for lubrication - in equilibrium with plasma but doesn't contain high molecular weight molecules like fibrinogen

 

==Intraperitoneal Organs==

**Specific gravity <1.015 to 1.018

 

**Total protein 25-39g/L

Organs are intraperitoneal if they are enclosed by a fold of visceral peritoneum. Intraperitoneal organs include: the [Monogastric Stomach - Anatomy & Physiology|stomach]], [[Small Intestine Overview - Anatomy & Physiology|small intestine]], [[Large Intestine - Anatomy & Physiology|large intestine]], [[Liver - Anatomy & Physiology|liver]], [[Gall Bladder - Anatomy & Physiology|gall bladder]], [[Pancreas - Anatomy & Physiology|pancreas]] and [[Spleen - Anatomy & Physiology|spleen]].

 

**[[Mesothelial cells|Mesothelial cells]]/macrophages

 

Organs are described as retroperitoneal if they are located behind the parietal peritoneum. Retroperitoneal organs include: the [[Urinary System Overview - Anatomy & Physiology|kidneys]], [[Adrenal Glands - Anatomy & Physiology|adrenal glands]], [[Ureters - Anatomy & Physiology|ureters]], [[Urinary Bladder - Anatomy & Physiology|urinary bladder]], part of the [[Oesophagus - Anatomy & Physiology|oesophagus]], [[Rectum - Anatomy & Physiology|rectum]], [[Ovary - Anatomy & Physiology|ovaries]], [[Uterus - Anatomy & Physiology|uterus]], aorta and caudal Vena Cava.

==Links==

==Links==

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