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Why is digestion necessary
1. Why is digestion necessary
All animals require a supply of water,
oxygen, simple sugars, amino acids,
fatty acids, vitamins, other organic and
inorganic molecules.
2. • In nature these substances are available in the
form of
• Proteins
• Starches
• Fats
• Vitamins
• Minerals.
3. • All of these substances need to be broken
down in to simple molecules so that they can
pass through cell membranes and are used by
body.
4. • These simple molecules are
• amino acids
• sugars
• fatty acids
7. Cardiac sphincter
• It is a special ring of muscles at the junction of
oesophagus and stomach.
8. sphincter
• sphincter
• a circular band of voluntary or involuntary
muscle that encircles an orifice (opening) of
the body or one of its hollow organs.
9. • When sphincter muscles contract , the
entrance to stomach closes and stops moving
back of stomach contents back into
oesophagus (food pipe).
10. • This sphincter opens when a wave of
peristalsis comes down the food pipe.
11. • per·i·stal·sis
• the progressive wave of contraction and
relaxation of a tubular muscular system
15. Location of stomach
• Stomach is situated on the left side of
abdomen under diaphragm
16. • (in direction or location) from front to back in
the median plane or in a plane parallel to the
median.
17.
18.
19. Stomach wall
• 3 layers
• Outer layer of connective tissue
• Middle layer of smooth muscles
• Inner layer( mucosa) of connective tissue with
many glands.
20. Middle layer
• Outer longitudinal
• Inner circular muscles
• These muscle layers help in churning (mixing
,tossing and turning) and mixing of food with
stomach secretions.
• This mixture is called chyme
21. Mucosa
• It has various tubular gastric glands which are
composed of 3 kinds of cells.
22. Mucous cells
• They secrete mucus
• Mucous is thick secretion that covers the
inside of stomach and stops digestion of lining
of stomach wall
23. Parietal cells
• Also called oxyntic cells
• They secret HCl.
• HCl is secreted in concentrated forms.
• It adjusts the pH of stomach contents ranging
from 2-3 so that pepsin can act on proteins.
• It also makes food soft
• It kills microorganism taken along with food
24. Zymogen cells
• They secrete pepsinogen.
• Pepsin is an enzyme.
• Its inactive form is called pepsinogen.
• Pepsinogen gets converted to pepsin only in
acidic environment or after getting exposed to
some already activated pepsin.
• Pepsin hydrolyses protein to produce
peptones and polypeptides.
26. Digestion of carbohydrates
• In the Mouth
The process of digesting carbohydrates begins
in the mouth. Our saliva contains an enzyme
called amylase that starts breaking down the
more complex carbs into simpler types.
• In the Stomach
Enzyme activity continues in the stomach, but
slows down significantly as digestive acids are
released into the stomach by the glands.
27. • The secretion of gastric juice is regulated by
• 1. smell
• 2.sight
• 3.quality
28. • Chyme finally goes to duodenum through
relaxed pyloric sphinter.
