Absorption

• Absorption

  the process whereby digested food substances are absorbed into the body cells.
• Small Intestine


  • Inner surface of small intestine has numerous finger-like projections called villi, which increase surface area for absorption
  • The epithelium wall of the villus is one cell thick, it provides a short diffusion distance for nutrients to pass through
  • The cell walls of the epithelium have many microvilli, which further increase the surface area for absorption

  
• Small Intestine


  • Each villus has many blood capillaries which allow blood to transport the absorbed glucose and amino acids away, maintaining a diffusion gradient
  • Each villus contains a lacteal, allowing transport of absorbed fats away, maintaining a steep diffusion gradient
  • The epithelial cells have many mitochondria, which provide energy for active transport of nutrients into villi

  
• Absorption in small intestine


  • glucose and amino acids are absorbed by diffusion into the blood capillaries of the villi
  • glucose and amino acids are absorbed by active transport
  • lower concentration of digested food substances in the lumen of the small intestine than in blood capillaries
  • glycerol and fatty acids diffuse onto epithelium, then combine to form minute fat globules that enter the lacteals
• Undigested and unabsorbed matter


  • Undigested and unabsorbed matter is stored temporarily in the rectum
  • it is then discharged as faeces through the anus (egestion)