Abdominal wall and intestines

1. Describe the arrangement of the muscles that make up the anterior and lateral body wall and understand their functions. 

  • Laterally, the wall of the abdomen is composed of 3 layers of muscles- external, internal and transverse abdominal muscles.
  • Anteriorly, the wall consists of a vertical band of muscle, the rectus abdominis, which extends from the xiphoid process to the pubic crest. It is a paired muscle, joined by the linea albea. It is contained in a separate rectus sheath.
  • The muscles of the abdominal wall support the abdominal viscera and regulate the pressure within the peritoneal cavity.
  • They are important for:
    • Respiration, coughing and sneezing
    • Micturition, defecation and childbirth
    • Lifting heavy objects

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2. Be able to distinguish the major segments of the intestinal tract both within a cadaver and in isolation.

  • The oesophagus penetrates the diaphragm and opens immediately into the stomach which is followed by the duodenum, forming a c shaped loop towards the upper left hand side of the abdomen.
  • The jejunum and ileum then run on a slant from top left to bottom right of the abdomen.
  • From here, the large intestine, consisting of the caecum, ascending colon, transverse colon and descending colon form a wide clockwise loop around the outside of the abdomen before giving rise to the sigmoid colon and rectum.
  •  The appendix is connected to the caecum, and is located in the right iliac fossa.
  • The fundus of the stomach often contains gas.
  •  The jejunum is covered in plicae circularis and folds, whereas the ileum is much fattier.
  • The large intestine has fatty tags (appendices epiploica) externally and an outer layer of three bands known as tenae coli that form haustrations.

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3. Locate and recognise the superior mesenteric artery and its major branches. 

  • This artery arises from the aorta and supplies the second part of the duodenum to two thirds along the transverse colon.
  •  The branches are:
    • Jejunal and ileal
    • Ileocolic
    • Right colic
    • Middle colic

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4. Locate and recognise the inferior mesenteric artery and its major branches.

  • This artery is the third branch of the aorta.
  • It supplies the last part of the transverse colon, the descending colon and the sigmoid colon and rectum.
  •  The branches are:
    • Left colic
    • Sigmoid
    • Superior rectal