Peritoneal Cavity - Anatomy & Physiology

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Introduction

The peritoneum is the serous membrane which lines the abdominal cavity. 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 the immune response and wall off infection in the abdomen to prevent peritonitis.

Structure

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

Single layer of mesothelial cells

• 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.

Function

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

Histology

• Have microvili on their surface
• Very fragile but regenerate very quickly
• High fibrinolytic activity - protects against the formation of adhesions
• Show reactive change with inflammation or effusions
• May be confused with neoplastic cells

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
• 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

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