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Nutrition in Man. Let’s Recap!. What are the 3 parts of the small intestine? What are the 3 secretions found in the duodenum? Are you able to recall what enzymes are involved? What about bile? How does bile aid in fats digestion?. Lesson Objectives. Lesson Objectives.

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let s recap
Let’s Recap!
  • What are the 3 parts of the small intestine?
  • What are the 3 secretions found in the duodenum?
  • Are you able to recall what enzymes are involved?
  • What about bile? How does bile aid in fats digestion?
lesson objectives1
Lesson Objectives
  • What are the things you want to know to about the ileum ?
  • In your pairs, share what you want to know about the ileum and write it on your whiteboard
  • 3 minutes
lesson objectives2
Lesson Objectives
  • Describe the functions of ileum in terms of absorption of carbohydrates, proteins and fats
  • To state the adaptation of small intestines in absorption of nutrients , closely relating to the structures : villi and microvilli
ileum

Ileum

Wait… What about jejunum?

structure
Structure
  • Highly coiled tube; inner walls contains numerous folds, villi and microvilli
functions
Functions
  • Mainly for absorption
  • Walls have numerous folds to provide a large surface areafor absorption of digested food
functions1
Functions
  • Epithelialcells of the villi are one-cell thick to allow for quick diffusion.
  • Richly supplied with blood capillariesand lymphatic capillaries to carry away absorbed food substances to maintain a concentration gradient.
adaptations

Adaptations

Of the small intestine for absorption

terms to remember
Terms to remember

Ingestion

Mechanical digestion

Chemical digestion

Absorption

Assimilation

recall diffusion
Recall diffusion…
  • What factors affect the rate of diffusion of molecules across a partially permeable membrane?
    • Temperature
    • Surface area
    • Concentration gradient
    • Thickness of the membrane
rate of absorption
Rate of absorption
  • The rate of absorption of digested food substances depends on:
    • The length of the small intestine
    • The thin epithelial wall that lies between the food substances and the blood capillaries
    • The concentration gradientacross the intestinal wall
slide14

The Digestive System

Absorption of Digested Food

About 90% of the digested food is absorbed in the small intestine.

liver

gall bladder

hepatic portal vein

pancreas

bile duct

pancreatic duct

duodenum

absorption
Absorption
  • The process whereby digested food materials are taken into body cells
adaptations of small intestine
Adaptations of small intestine

Increase surface area to volume ratio

  • The small intestine is long and have inner walls with numerous transverse folds
  • The presence of minute finger-like projection called villi
  • The presence of finger like projection called microvilli on each villus
villi and microvilli
Villi and microvilli

Small Intestine

Lining of small intestine

Microvilli

Section of a villus

villi and microvilli1
Villi and microvilli
  • The villi of the small intestine increases the surface area ratio to volume by approximately 100-folds!
  • Do you know how big that is?

Demonstration

adaptations of small intestine1
Adaptations of small intestine

Other adaptations

1) Villi have thin walls and membranes to facilitate diffusion

  • Epithelial wall of the villi is only one cell thick

2) Intestinal wall and villi richly supplied with blood vessels and lymphatic vessels

  • Carry away absorbed food
villi
Villi
  • Absorbed by villi of small intestine
    • Simple sugars
    • Amino acids
    • Fatty acids and Glycerol
how does absorption take place in the intestines
How does absorption take place in the intestines?

Glucose and amino acids:

Diffusion

  • Transport of substances away from the intestines maintains the concentration gradient for diffusion of new substances across the intestinal walls
how does absorption take place in the intestines1
How does absorption take place in the intestines?

Glucose and amino acids:

Diffusion

  • Transport of substances away from the intestines maintains the concentration gradient for diffusion of new substances across the intestinal walls
how does absorption take place in the intestines2
How does absorption take place in the intestines?

Fatty acid and glycerol:

  • Each villus has a lymphatic capillary (lacteal) which transports fats
transport of nutrients
Transport of nutrients…
  • Lead into small venules joined together forming hepatic portal vein
    • Carries blood directly to liver
slide27

Absorption of Digested Food

to heart

hepatic vein

posterior vena cava

liver

stomach

hepatic portal vein

gastric vein

intestinal vein

small intestine

Blood is carried directly from the stomach and the intestine to the liver via the hepatic portal vein.

summary1
Summary
  • What is absorption?
  • What are the three adaptations of small intestine to increase surface area ratio to volume?
  • What are some of the other ways to facilitate the absorption of nutrients?
  • How are the nutrients being absorbed?
muddiest point
Muddiest Point
  • Any Question?