Page 55 - Biology Form Two

Biology for Secondary Schools

(iii) There are various blood capillaries (iv) The ileum is very long, about
in the ileum, which join together six metres. Therefore, food takes
to form the hepatic portal vein a long time to pass through the
that transports blood to the liver. ileum. This ensures maximum
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These blood capillaries ensure that absorption of the end products of
digestion.
food is absorbed from the ileum (v) The lining of the ileum is only
instantly and hence maintain the one cell thick allowing easier
diffusion gradient. The liver filters absorption and diffusion of the

harmful and toxic substances nutrients in the body.
(detoxification) and stores fat- (vi) The inner lining of the ileum wall
soluble vitamins as well as excess is folded forming small finger-like
glucose in form of glycogen. structures called villi (singular –

Other products of digestion are villus) as shown in Figure 2.6. The
distributed throughout the body villi help to increase the surface
through the bloodstream. area for absorption of the digested
food into the bloodstream.

Absorptive cells

Lacteal

Blood capillaries

Artery
Vein
Lymph duct

Wall of the ileum

Figure 2.6: Structure of villi

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