Difference between revisions of "Peritoneal Cavity - Anatomy & Physiology"

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<big><center>[[Alimentary - Anatomy & Physiology|'''BACK TO ALIMENTARY - ANATOMY & PHYSIOLOGY''']]</center></big>
 
==Introduction==
 
==Introduction==
  
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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]].
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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 mesentries, 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.
  
 
===Development===
 
===Development===
  
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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.
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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 [[Forestomach - Anatomy & Physiology|stomach]] and cranial to the [[Rectum - Anatomy & Physiology|rectum]]. This gives the entire small intestine and most of the large intestine large scope for expansion and rotation. It also allows the left and right coelomic cavities coalesce. This forms one cavity; '''the peritoneal cavity'''.
 +
Peritoneal structures develop from the dorsal and ventral mesogastria.
  
 
==Structure & Histology==
 
==Structure & Histology==
  
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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'''.
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*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'''.
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**Mesothelial cells are simple squamous and of mesodermal origin.
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''NB: In reality there are no viscera located in the peritoneal cavity. However the cavity created by the '''serosa''' is also confusingly referred to as the peritoneal cavity, and contains most abdominal contents.''
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***Have microvilli on their surface.
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***Very fragile but regenerate very quickly.
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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.
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*A small amount of fibroelastic tissue is present within the connective tissue layer to provide support.
−
 
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*There are two layers of peritoneum lining the abdomen.
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''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.''
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**Lining the abdominal wall is the '''parietal layer'''.
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**Lining the abdominal viscera is the '''visceral layer'''.
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The peritoneal cavity is complete in the male, but a potential communication with the exterior exists in the female at the opening of the [[Oviduct - Anatomy & Physiology|oviduct]].
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**The small space within these two layers is called the '''peritoneal cavity'''.
 +
**''NB: In reality there are no viscera located in the peritoneal cavity. However the cavity created by the '''serosa''' is also confusingly referred to as the peritoneal cavity, and contains most abdominal contents.''
 +
*The peritoneum evaginates to extend into the inguinal canals.
 +
*Many species have 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.
 +
*''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===
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*Peritoneal fluid is produced by mesothelial cells.
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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]]''.
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*The potential space formed by the two layers of peritoneum is filled with a thin film of fluid that 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.
  
 
==Function==
 
==Function==
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*Secretes a small volume of clear fluid for lubrication
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Peritoneum secretes a small volume of clear fluid for lubrication. It provides a route for entry of blood and nerve and lymphatics. There is high fibrinolytic activity to protect against the formation of adhesions. Inflammed portions of the peritoneum adhere to each other and may become organised and permanent. This may help to wall of infections and bring leuckocytes to the site of infection. This trait is taken advantage of in surgery when serosal surfaces are often turned in when closing an incision.
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**Allows the abdominal viscera to move around by reducing the friction between them.
 +
***High fibrinolytic activity to protect against the formation of adhesions.
 +
*Provides a route for entry of blood and nerve and lymphatics
  
 
==Types of Peritoneum==
 
==Types of Peritoneum==
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Terminology:
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The peritoneum doubles up to form the following suspensory structures: '''Mesentery''', from viscera to the dorsal abdominal wall.
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becomes double in some areas
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'''Omentum''', from the [[Monogastric Stomach - Anatomy & Physiology|stomach]] to other viscera and '''ligament''', from viscera not involved in digestion to the abdominal wall ''or'' to other viscera that are not involved in digestion (e.g.ligaments of the [[Liver - Anatomy & Physiology|liver]]).
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*Mesentry: attaches viscera to the dorsal abdominal wall.
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*Omentum: from the stomach to other viscera.
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===Mesenteries===
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*Ligament: from viscera not involved in digestion to the abdominal wall ''or'' to other viscera that are not involved in digestion (e.g.ligaments of the [[Liver - Anatomy & Physiology|liver]]).
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The entire alimentary tract is attached to the dorsal body wall by mesentery, a derivative of the dorsal mesogastrium. '''Mesoduodenum''' attaching the [[Duodenum - Anatomy & Physiology|duodenum]] to the abdominal roof contains the right lobe of the [[Pancreas - Anatomy & Physiology|pancreas]]. '''Great Mesentery''' extends from the [[Jejunum - Anatomy & Physiology|jejunum]] and [[Ileum - Anatomy & Physiology|ileum]] to the abdominal roof and contains the cranial abdominal artery and vein, mesenteric lymph nodes and mesenteric plexus. '''Mesocolon''' attaches the [[Colon - Anatomy & Physiology|colon]]  and  '''mesorectum''' the [[Rectum - Anatomy & Physiology|rectum]] to the abdominal roof. The [[:Category:Female Reproduction|female reproductive tract]] is also suspended by peritoneal derivatives. The '''broad ligament''' consisting of mesometrium, mesosalpinx and mesovarium, from [[Ovary - Anatomy & Physiology|ovary]], [[Oviduct - Anatomy & Physiology|oviduct]], [[Uterus - Anatomy & Physiology|uterus]], [[Cervix - Anatomy & Physiology|cervix]] and cranial [[Vagina and Vestibule - Anatomy & Physiology|vagina]] to the dorsal body wall, contains ovarian artery, uterine branch of the ovarian artery, uterine artery, ovarian vein, uterine vein and uterine [[Lymph Nodes - Anatomy & Physiology|lymph node]] (mare).
 
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===Omenta===
 
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During development in the region of the [[Monogastric Stomach - Anatomy & Physiology|stomach]], a fold of the dorsal mesogastrium becomes extended into a curtain - like structure called the '''greater omentum'''. It originates from the dorsal wall of the abdomen and attaches to the greater curvature of the stomach. The potential space between the two sheets is called the '''omental bursa'''. It covers the [[Jejunum - Anatomy & Physiology|jejunal mass]] on the ventral abdominal wall. The opening to the omental bursa is called the '''epiploic foramen'''. The '''lesser omentum''' runs from the lesser curvature of the [[Monogastric Stomach - Anatomy & Physiology|stomach]] to the [[Liver - Anatomy & Physiology|liver]].
 
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===Ligaments===
 
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The '''gastrophrenic ligament''' - from the greater curvature of the [[Monogastric Stomach - Anatomy & Physiology|stomach]] to the crura of the diaphragm.
 
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The '''gastrosplenic ligament''' - part of the greater omentum. Connects the [[Spleen - Anatomy & Physiology|spleen]] to the [[Monogastric Stomach - Anatomy & Physiology|stomach]].
 
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The '''hepatoduodenal ligament''' - remnant of the ventral mesogastrium. From the cranial part of the [[Duodenum - Anatomy & Physiology|duodenum]] to the [[Liver - Anatomy & Physiology|liver]]. The bile duct runs within it.
 
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The '''nephrosplenic ligament''' (renosplenic ligament) - In the horse, from [[Spleen - Anatomy & Physiology|spleen]] to [[Urinary System Overview - Anatomy & Physiology#Upper Urinary Tract|left kidney]].
 
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The '''round ligament''' - part of the broad ligament. From the [[Ovary - Anatomy & Physiology|ovary]] to the inguinal ring.
 
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The '''suspensory ligament''' - from the [[Ovary - Anatomy & Physiology|ovary]] to the abdominal wall.
 
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The '''proper ligament of the [[Ovary - Anatomy & Physiology|ovary]]''' - from the [[Ovary - Anatomy & Physiology|ovary]] to the [[Oviduct - Anatomy & Physiology|oviduct]].
 
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The '''ligaments of the [[Liver - Anatomy & Physiology| Liver]]'''.
 
  
 
==Intraperitoneal Organs==
 
==Intraperitoneal Organs==
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*Organs are intraperitoneal if they are enclosed by a fold of visceral peritoneum.
 +
*Intraperitoneal organs include:
 +
**[[Forestomach - Anatomy & Physiology|Stomach]]
 +
**[[Small Intestine - Anatomy & Physiology|Small Intestine]]
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**[[Large Intestine - Anatomy & Physiology|Large Intestine]]
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**[[Liver - Anatomy & Physiology|Liver]]
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**[[Gall Bladder - Anatomy & Physiology|Gall Bladder]]
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**[[Pancreas - Anatomy & Physiology|Pancreas]]
 +
**[[Spleen - Anatomy & Physiology|Spleen]]
  
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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]].
+
==Retroperitoneal Organs==
 +
*Organs are described as retroperitoneal if they are located behind the parietal peritoneum.  
 +
*Retroperitoneal organs include:
 +
**[[Urinary System - Anatomy & Physiology|Kidneys]]
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**[[Endocrine System - Adrenal Glands - Anatomy & Physiology|Adrenal glands]]
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**[[Ureters - Anatomy & Physiology|Ureter]]
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**[[Bladder - Anatomy & Physiology|Urinary Bladder]]
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**Part of [[Oesophagus - Anatomy & Physiology|Oesophagus]]
 +
**[[Rectum - Anatomy & Physiology|Rectum]]
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**[[Female Reproductive Tract -The Ovary - Anatomy & Physiology|Ovaries]]
 +
**[[Female Reproductive Tract - The Uterus - Anatomy & Physiology|Uterus]]
 +
**Aorta
 +
**Caudal Vena Cava
  
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==Retroperitoneal Organs==
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==Species Differences==
  
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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.
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*Small animals
 +
**Low volume of clear straw coloured fluid
 +
**Specific gravity <1.015 to 1.018
 +
**Total protein 25-39g/L
 +
**Nucleated cell count <3x10e9/L
 +
**[[Mesothelial cells|Mesothelial cells]]/macrophages
  
 
==Links==
 
==Links==
  
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'''Click here for information on the [[:Category:Peritoneal Cavity - Pathology|pathology of the peritoneal cavity]]'''
 
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{{Template:Learning
 
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|flashcards = [[Peritoneal_cavity_- Anatomy & Physiology_-_Flashcards|peritoneal cavity flashcards]]
 
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|videos = [http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0048.mp4 The Small and Large intestine of the Ruminant]<br>[http://stream2.rvc.ac.uk/Anatomy/bovine/Pot0061.mp4 The Bovine Liver]<br>[http://stream2.rvc.ac.uk/Anatomy/canine/Pot0036.mp4 The Canine Abdomen]<br>[http://stream2.rvc.ac.uk/Anatomy/equine/Pony_abdomen.mp4 Lateral View of the Equine Abdomen]<br>[http://stream2.rvc.ac.uk/Anatomy/equine/pot0228.mp4 The Equine Liver]<br>[http://stream2.rvc.ac.uk/Frean/Pony/left_topography.mp4 Left Sided topography of the Equine abdomen]<br>[http://stream2.rvc.ac.uk/Frean/Pony/left_topography.mp4 Left Sided topography of the Equine abdomen]<br>[http://stream2.rvc.ac.uk/Anatomy/feline/pot0357.mp4 The Feline Abdomen]<br>[http://stream2.rvc.ac.uk/Frean/sheep/LeftSideTopography.mp4 Left sided topography of the Ovine Abdomen and Thorax]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RightSideTopography.mp4 Right sided topography of the Ovine Abdomen]<br>[http://stream2.rvc.ac.uk/Frean/sheep/RuminantStomachStructure.mp4 Structure of the ruminant forestomachs]
 
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|full text = [http://www.cabi.org/cabdirect/FullTextPDF/2009/20093073709.pdf  '''Greater omentum: the surgeons' friend, no longer a forgotten organ.''' Saifzadeh, S.; Iranian Veterinary Surgery Association, Kermen, Iran, Iranian Journal of Veterinary Surgery, 2008, Supplement 2, pp 39-47, 60 ref.]
 
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|Vetstream = [https://www.vetstream.com/canis/Content/Disease/dis00671.asp Peritonitis]
 
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}}
 
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==Webinars==
 
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<rss max="10" highlight="none">https://www.thewebinarvet.com/gastroenterology-and-nutrition/webinars/feed</rss>
 
  
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[[Category:Alimentary System - Anatomy & Physiology]]
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<big><center>[[Alimentary - Anatomy & Physiology|'''BACK TO ALIMENTARY - ANATOMY & PHYSIOLOGY''']]</center></big>
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[[Category:Peritoneal Cavity]]
 
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[[Category:A&P Done]]
 

Revision as of 14:10, 23 July 2008

BACK TO ALIMENTARY - ANATOMY & PHYSIOLOGY

Introduction

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 mesentries, 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.

Development

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 stomach and cranial to the rectum. This gives the entire small intestine and most of the large intestine large scope for expansion and rotation. It also allows the left and right coelomic cavities coalesce. This forms one cavity; the peritoneal cavity. Peritoneal structures develop from the dorsal and ventral mesogastria.

Structure & Histology

  • Lining the abdomen is a thin layer of loose connective tissue covered by a single layer of 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.
      • Have microvilli on their surface.
      • 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.
    • NB: In reality there are no viscera located in the peritoneal cavity. However the cavity created by the serosa is also confusingly referred to as the peritoneal cavity, and contains most abdominal contents.
  • The peritoneum evaginates to extend into the inguinal canals.
  • Many species have 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.
  • 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 is produced by mesothelial cells.
  • The potential space formed by the two layers of peritoneum is filled with a thin film of fluid that 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.

Function

  • Secretes a small volume of clear fluid for lubrication
    • Allows the abdominal viscera to move around by reducing the friction between them.
      • High fibrinolytic activity to protect against the formation of adhesions.
  • Provides a route for entry of blood and nerve and lymphatics

Types of Peritoneum

Terminology: becomes double in some areas

  • Mesentry: attaches viscera to the dorsal abdominal wall.
  • Omentum: from the stomach to other viscera.
  • Ligament: from viscera not involved in digestion to the abdominal wall or to other viscera that are not involved in digestion (e.g.ligaments of the liver).

Intraperitoneal Organs

Retroperitoneal Organs

Species Differences

  • Small animals
    • Low volume of clear straw coloured fluid
    • Specific gravity <1.015 to 1.018
    • Total protein 25-39g/L
    • Nucleated cell count <3x10e9/L
    • Mesothelial cells/macrophages

Links

BACK TO ALIMENTARY - ANATOMY & PHYSIOLOGY
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