The Jejunum and Ileum
General arrangement:  
  • The jejunum and ileum together measure about 6m in length in adult.

  • The upper two-fifths comprise the jejunum;

  • the lower three-fifths the ileum.

  • The jejunum and ileum are massed into numerous coils which occupy the major part of the infracolic compartment of the greater sac.

  • They are covered to a varying extent by the greater omentum.

  • They extend into the pelvic cavity and rest on the pelvic viscera, occupying the various recesses between them.

  • The coils have a varying degree of mobility, depending on the length of their mesentery. The first part of the jejunum and the last part of the ileum are shorter stalks and are therefore less mobile than the intervening coils.
   

External differences between jejunum and ileum

It is sometimes necessary to distinguish between jejunum and ileum by external features, as follows:

 
Jejunum
 Ileum
 
Position:
  • More to the left and above;
  • Right and below.
Appearance
  • Redder and wider.
  • Paler and narrower
Feel:
  • Thicker
  • Numerous plicae circulares, which can be felt through the bowel wall.
  • Thinner
  • Fewer plicae
Aggrated lymphatic follicles:
  • Fewer and smaller in the jejunum.
  • More and larger
Messenteric fat :
  • Less fat in the mesentery of the jejunum near the gut, so that translucent ‘windows' are visible when the mesentery is held against the light.
  • Such areas are absent from the mesentery of the terminal ileum.
Arterial arcades
  • Arteries form a greater number of arcades than do the ileal arteries. .
  • Form fewer arcades- Receives shorter terminal branches from tertiary or quaternary arcades


The Intestines