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Unit9 DIGESTION AND ABSORPTION


 

DIGESTION AND ABSORPTION

INTRODUCTION

Food is one of the basic requirement of the living organisms. To perform various functions of the body energy is required, which is obtained from food. The process of conversion of complex food material in to simple and diffusible forms by hydrolysis is termed as Digestion. Major component of food are carbohydrates, proteins and fats, vitamins minerals are also required in small quantities

The alimentary canal is tubular structure which extends from mouth to anus. It develops from ectoderm & endoderm.
Ectoderm – up to hard palate
Endoderm – from soft palate to rectum
Ectoderm – from anal canal to Anus
The alimentary canal is divided into following parts–
(1) Mouth and Buccopharyngeal cavity, Pharynx
(2) Oesophagus
(3) Stomach
(4) Intestine


 Important Points

1.  Spoil hay of Sweet clover (melilotus indica) (Fodder and green manure) contains a substance called dicumarol. Dicumarol prevents the action of vitamin ‘K’
2. Non-secretion of HCl is called as achlorhydria condition.
3. Chalogogues are substances which cause. The contraction of gall bladder
4. Choloretic are substances which increase bile juice from liver.
5. ‘’Achalasia Cardia’’ condition is characterized by failure of cardiac sphincter to relax completely on swallowing causing accumulation of food in oesophagus and proximal oesophagus dialates.
6. One pair of vomerine teeth is found in the palate of frog.
7. Fangs are the poison teeth of snakes, these are the maxillary teeth.
8. Upper incisor teeth are modified in tusk in elephant.
9. Upper canine teeth are modified in tusk in walrus.
10. Homodont type dentition are found in toothed whale.
11. Enamel is absent in sloth and Armadillo.
12. Salivary glands are absent in whale.
13. The tongue is non-motile in whale.
14. Gall bladder is absent in lemprey, whale, rat and horse.
15. The main pancreatic duct is also known as duct of wirsung while accessory pancreatic duct is known as duct of santorini.
16. Citrin is also known as vitamin ‘P’ and controls vascular permeability.
17. Vitamin B17 – It is a recently discovered anticancer vitamin.
18. Vitamin Q – helps in blood clotting.
19. Vita B15 – It is also known as pogonic acid, deficiency causes disorder in liver.
20. Vitamin B6 also used in the treatment of tuberculosis.
21. Thecodont teeth are also found in crocodile

 Biomacromalecules in food cannot be utilised by our body in their original form. They have been broken down and conveted into simple substances in the digestive system. This proces of conversion of complex food subtances to simple absorbable forms is called digestion.
 No significant digestive activity occurs in the large intestine.“The functions of large intesitine are
(a) absorption of some water, minerals and certain drugs.
(b) secretion of mucous, which helps on adhering the waste particles together and lubricating it for an easy passage.
 The undigested, unabsorbed substances called faeces enters into the caecum of large intestine through ileocaecal value, which prevents the backflow of the faecal matter. It is temporarily store in the rectum till defaecation.
 Absorption of digested product :
 Absorption is the process by which the end products of digestion pass through the intestinal mucosa into the blood or lymph.
1. Disorders of digestive system :
 Jaundice : The liver is affected, skin and eyes tum yellow due to the deposite of bile pigments.
 Vomitting : It is the ejection of stomach contents through the mouth. This reflex action is controlled by the vomit centre in the medulla. A feeling of nausea precedes vomitting.
 Diarrhoea : The abnormal frequency of bowel movement and increased liquidity of the faecal discharge is known as diarrhoea. It reduces the absorption of food.
 Constipation : In constipation, the faeces are retained within the rectum as the bowel movements occur irregularly .
 Indigestion : In this condition, the food is not properly digested leading to a feeling of fullness. The causes of indigestion are inadequate enzyme secretion, anxiety, food poisoning, over eating and spicy food.
 When chyme enter into doudenum HCL of chyme stimulate different enteroendocrine cells of intestine to secrete following hormones.
1. Secretin - 1st discovered hormone, stimulate pancreas to synthesise and secrete nonenzymatic part of pancreatic juice.
2. Pancreozymin stimulate pancreas to synthesise and secrete enzymatic part of pancreatic juice.
3. Hepatocrinin stimulate liver cells for synthesis and secretion of bile juice.
4. Cholecystokinin stimulate liver and Gall Bladder for secretion of bile juice
 

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