Transcript bf971d386b8c4c3

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Digestion is the breakdown of large, complex organic
molecules into smaller , more simple components that
can be absorbed and used by the body.
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Molecules need to be small enough to diffuse across
plasma membranes of the cells lining the intestinal wall
through the process of absorption.
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Digestion includes all the processes that chemically and
mechanically break down food into nutrients
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Begins immediately after food is ingested
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Includes Mechanical and Chemical digestion
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Mechanical digestion is mechanical
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changes of the physical state of the food by ,
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Mastication in the mouth– reducing the food
particle size through chewing, and mixes food
with saliva
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Deglutition
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Churning of the contents in the GI lumen
(stomach and intestinal movement so they are
well mixed with the GI juices
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Propelling food through the digestive tract
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Chemical digestion: changes in chemical composition of food as it
travels through the digestive tract; these changes are the result of
hydrolysis by Digestive enzymes
Digestive enzymes are characterized by
Extracellular, organic (protein) catalysts follows the Principles of
enzyme action which are
A. Specific in their action as proteinases hydrolysis protein ,Lipases
hydrolysis fat and saccaridase hydrolysis disaccarides
B. Function optimally at a specific pH
C. Enzymes are continually being destroyed or eliminated from the
body and must continually be synthesized
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Ingestion : is the consumption of or taking in of nutrients
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Mastication: chewing. Breaking down of food in the mouth
with the help of teeth
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Deglutition: swallowing of solids or liquids
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Digestion: breaking down of large nutrient molecules into
smaller ones so that they may be absorbed
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Absorption: transfer of medium and small sized nutrient
molecules from GIT lumen into blood
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Defecation: passage of stools/ faeces from the rectum to the
exterior
 Gastrointestina
l (Gl) tract
(Alimentary
canal)
Accessory
structures Not in
tube path
1.
Mouth
1. Salivary gland
2.
Oral Cavity
2. Liver
3.
Pharynx
4.
Esophagus
5.
Stomach
6.
Small intestine
7.
Large intestine
8.
Anus
3. Gall bladder
4. Pancreas
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Three pairs:
1. PAROTID :on side of face (swell with the mumps)
2. SUBLINGUAL: (below tongue) and
3. SUBMANDIBULAR: both in lower jaw
produce saliva
Functions of Salivary
1. Lubrication : to facilitate mastication of
food and make it slides easily through
the
2.Saliva coats the oral cavity and esophagus
3.Solubilises dry food: in order to be tasted,
the molecules in food must be disolved
4.Oral hygiene: The oral cavity is almost
constantly flushed with saliva, which
floats away food debris and keeps the
mouth relatively clean
J-shaped pouch of the Located slightly left of center in the body with
Capacity: about 1 litre has two opening
a. Cardiac Sphincter:Muscle that surrounds the esophagus at its
junction with the stomach , Opens to admit food into the stomach
b. Pyloric sphincter : Muscle that surrounds the stomach at its
junction with the small intestine: Opens to admit CHYME into the
small intestine
Functions
a. Storage area for ingested food
(empties in 2-6 hours)
b. Place for digestive enzymes (pepsin
and salivary amylase) to work
c. Main place for protein digestion
d.
Absorption of small molecules
(e.g. H2O, ethanol)
3 meters or  10 feet in length, Walls highly convoluted to  S.A.
Interior folds covered with villi: tiny fingerlike projections that further  S.A.
Divided into 3 parts:
a. Duodenum (first 25 cm): Produces digestive enzymes: lactase, peptidase, maltase,
nuclease
b. Jejunum
c. Ileum
Functions:
1.
2.
Completes digestion
Absorption of nutrients
a. monosaccharides, amino acids, short
peptides, fatty acids are transported into
intestinal cells, and diffuse into
bloodstream
b. Fats diffuse into intestinal cells and are
deposited in the lacteal (lymph vessel in
the villus)
Blood Supply For Gastrointestinal Tract
Synthesize and secerte bile that act as detergent –
emulsifies fats thus facilitate fate digestion
2. Detoxifies/removes toxic substances as Drugs and Alcohol
3. Stores Gycolgen, Vitamins (A, D, E, K), Fe, other minerals
and Cholesterol
4. Activates vitamin D
5. Formation of Fetal RBC
6. Formation of plasma protein: albumin, globulin and
fibrinogen
7. Stimulate bone marrow to form RBCs in adult through
secretion of erythropoietin hormone
8. Metabolizes absorbed food molecules
1.
Carbohydrates
2.
Proteins
3.
Lipids
1.
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Has exocrine function through
Production of pancreatic juice
(digestive enzymes and sodium
bicarbonate to neutralize acidic
chyme)
Has Endoocrine functions
through Production of insulin, a
hormone that
influences the
cells’ uptake of glucose from the
bloodstream , and Glucagon
hormone that share with insulin
to adjust blood sugar
5 parts
Ascending colon
Transverse colo
Descending colon
Rectum - stores feces
Anus- muscles close the
rectum until release of feces
is appropriate
Functions
Reabsorption of water
Formation of feces
Manufacture of some amino acids,
growth factors, vitamins B's and K by
E.coli)