MALL INTESTINE

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MALL INTESTINE
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Overview

• In humans over 5 years old it is approximately 7
  m (21 ft) long and can vary from 4-7 m
  (13.12-22.97 ft).
• It is divided into three structural parts
• Duodenum 26 cm (9.84 in) in length
• Jejunum 2.5 m (8.2 ft)
• Ileum 3.5 m (11.5 ft)
• Although the small intestine is much longer than
  the large intestine (typically 4-5 times longer),
  it is referred to as such due to its
  comparatively smaller diameter. On average, the
  diameter of the small intestine of an adult human
  measures approximately 2.5-3cm, and the large
  intestine measures about 7.6 cm in diameter
• The small intestine is the portal for absorption
  of virtually all nutrients into blood

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Structure small intestine
The villi are hair-like protrusions INTO the
intestine -- emanating from the wall of the
intestine. The purpose of the villi is to slow
the passage of food, and to allow food particles
to be captured in among these finger-like villi
-- so that the blood inside the villi can absorb
the nutrients in the food.
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Chemical digestion

• After food is churned up in your stomach, a
  sphincter muscle at the end of your stomach opens
  to squirt small amounts of food into the top of
  your small intestine. This first section of the
  small intestine is called the duodenum.
• Your pancreas releases digestive juices through a
  duct into your duodenum. This fluid is rich in
  enzymes that break down fats, proteins and
  carbohydrates. It also contains sodium
  bicarbonate which neutralises acid produced in
  your stomach.
• Your gall bladder squeezes out bile down a duct
  into your duodenum. Bile helps break down fats in
  your food.

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Peristalsis

• Digesting food is pushed through the small
  intestine by peristalsis. Peristalsis is a
  muscular movement in which alternating waves of
  muscle contraction and relaxation cause food to
  be squeezed along the digestive tract.

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Absorbing nutrients

• Most of the nutrients in the food you eat pass
  through the lining of your small intestine into
  your blood. The lining of the small intestine is
  covered in tiny microvilli. These are
  microscopic, finger-like protrusions which give
  the lining of the small intestine a massive
  surface area for absorption of nutrients to occur
  across. The microvilli give the inside of the
  intestine the look and feel of velvet.
• Each microvillus contains a minute blood
  capillary. When nutrients are absorbed into a
  microvillus, they enter its blood capillary. This
  is how nutrients from your food enter your blood.

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Indigestible food passes into the large intestine

• By the time food leaves your small intestine all
  the nutrients in your food will have entered your
  bloodstream. All that remains is indigestible
  food which is passed from your small intestine to
  your large intestine for further processing.

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Bile

• Bile salts are steroids with detergent properties
  which are used to emulsify lipids in foodstuff
  passing through the intestine to enable fat
  digestion and absorption through the intestinal
  wall.
• The five principle bile acids are
• Deoxycholic acid
• Cholic acid
• Chenodeoxycholic acid
• Glycocholic acid
• Taurocholic acid

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• Villi are structures, which act as valves, which
  allow solids liquids and/or acids to pass through
  one structure to another
• Most of food absorption is processed by the small
  intestine. The small intestine has three
  structures to handle absorption, villi,
  microvilli and the circular folds. The purpose of
  villi, microvilli and the circular folds is to
  increase the area of absorption within the small
  intestine. Microvilli are small projections of
  the mucous membrane of the small intestine walls.
  The microvilli give the small intestine walls a
  fuzzy appearance and are also know as the brush
  border. The structure of Villi is very similar to
  the microvilli except that villi are
  substantially larger than microvilli. Within all
  villi are a large number of capillaries and a
  lymphatic capillary as well.