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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]]. | + | 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. |
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| − | ===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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| | ==Structure & Histology== | | ==Structure & Histology== |
| − | | + | *The peritoneum is smooth and clear in the healthy animal. |
| − | 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'''.
| + | *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'''. |
| − | | + | **Mesothelial cells are simple squamous and of mesodermal origin. |
| − | ''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.''
| + | **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. |
| − | 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 in contact with the abdominal wall is called the '''parietal layer'''. |
| − | | + | **The layer covering the abdominal viscera is called the '''visceral layer'''. |
| − | ''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.'' | + | **The small space within these two layers is called the '''peritoneal cavity'''. |
| − | | + | *Many species have lymphoid tissue aggregates and fixed phagocytes in the omentum that are not covered by mesothelial cells |
| − | 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]].
| + | *''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.'' |
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| | ===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]]''.
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| | ==Function== | | ==Function== |
| | + | *Secretes a small volume of clear fluid for lubrication |
| | + | **Allows the abdominal viscera to move around by reducing the friction between them. |
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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.
| + | ==Vasculature== |
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| − | ==Types of Peritoneum== | |
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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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| − | '''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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| − | ===Mesenteries===
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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.
| + | ==Innervation== |
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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.
| + | ==Lymphatics== |
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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.
| + | ==Histology== |
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| − | The '''suspensory ligament''' - from the [[Ovary - Anatomy & Physiology|ovary]] to the abdominal wall.
| + | *Have microvili on their surface |
| | + | *Very fragile but regenerate very quickly |
| | + | *High fibrinolytic activity - protects against the formation of adhesions |
| | + | *Show reactive change with [[Peritoneal cavity - inflammatory|inflammation]] or [[Peritoneal cavity - effusions|effusions]] |
| | + | *May be confused with neoplastic cells |
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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]].
| + | ==Species Differences== |
| − | | + | *Peritoneum is normally smooth and clear, |
| − | The '''ligaments of the [[Liver - Anatomy & Physiology| Liver]]'''.
| + | *Small volume of clear fluid for lubrication - in equilibrium with plasma but doesn't contain high molecular weight molecules like fibrinogen |
| − | | + | *Small animals |
| − | ==Intraperitoneal Organs==
| + | **Low volume of clear straw coloured fluid |
| − | | + | **Specific gravity <1.015 to 1.018 |
| − | 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]].
| + | **Total protein 25-39g/L |
| − | | + | **Nucleated cell count <3x10e9/L |
| − | ==Retroperitoneal Organs==
| + | **[[Mesothelial cells|Mesothelial cells]]/macrophages |
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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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| | ==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]] | + | <big><center>[[Alimentary - Anatomy & Physiology|'''BACK TO ALIMENTARY - ANATOMY & PHYSIOLOGY''']]</center></big> |
| − | [[Category:Peritoneal Cavity]]
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| − | [[Category:A&P Done]]
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