Revision Notes: Digestion & Absorption - NEET PDF Download

 Page 1


Points To Remember
Digestion : The process in alimentary canal  by which the complex food is 
converted mechanically and biochemically into simple substances suitable for 
absorption and assimilation in the body of animals/organisms.
Food : A substance which is taken and digested in the body to provide 
material for growth, repair & energy for reproduction and resistance from disease 
or regulation of body processes.
Thecodont : The teeth embedded in the sockets of the jaw bone, e.g., in 
mammals.
Diphyodont : The teeth formed twice in life time e.g., in mammals.
Heterodont : Different types of teeth. An adult human has 32 permanent 
teeth which are of four different types.
Different Types of Teeth
(a) Canine—for tearing
(b) Incisors—for cutting
(c) Premolars for grinding
(d) Molars for churning and grinding
Crown
Root
Page 2


Points To Remember
Digestion : The process in alimentary canal  by which the complex food is 
converted mechanically and biochemically into simple substances suitable for 
absorption and assimilation in the body of animals/organisms.
Food : A substance which is taken and digested in the body to provide 
material for growth, repair & energy for reproduction and resistance from disease 
or regulation of body processes.
Thecodont : The teeth embedded in the sockets of the jaw bone, e.g., in 
mammals.
Diphyodont : The teeth formed twice in life time e.g., in mammals.
Heterodont : Different types of teeth. An adult human has 32 permanent 
teeth which are of four different types.
Different Types of Teeth
(a) Canine—for tearing
(b) Incisors—for cutting
(c) Premolars for grinding
(d) Molars for churning and grinding
Crown
Root
Dental formula of man :
Permanent Teeth)
1 C PM M
32 = 2 × 2 1 2 3 Upper Jaw
2 1 2 3 Lower Jaw
Dental formula of man :
(Milk Teeth)
1 C PM 
20 = 2 × 2 1 2 Upper Jaw
2 1 2 Lower Jaw
Peristalsis : The involuntary moveent of the gut by which the food bolus 
is pushed forward. 
Deglutition : The process of swallowing of food bolus. It is partly voluntary 
and partly involuntary.
Ruminants : The herbivours animals (e.g., cow, buffalo etc.) which have 
symbiotic bacteria in their rumen of their stomach which synthesize enzymes to 
hydrolyse cellulose into monosaccharides.
Diarrhoea : The abnormal frequent discharge of semisolid or fluid faecal 
matter from the bowel.
Vomitting : The ejection of stomach contents through the mouth, caused 
by antiperistalsis.
Dysentery : Frequent watery stools often with blood and mucus and with 
pain, fever and causes dehydration.
Chyme : The semifluid mass into which food is converted by gastric secretion 
and which passes from the stomach into the small intestine.
Gastric : Anything associated with stomach is given a prefix ‘gastric’.
Proenzyme : The inactive forms of enzymes.
Sphincter : A flap like structure at various junctions of the alimentary canal  
which facilities one way traffic (movement of material) in the alimentary canal.
Bolus : The masticated food mixed with saliva.
Page 3


Points To Remember
Digestion : The process in alimentary canal  by which the complex food is 
converted mechanically and biochemically into simple substances suitable for 
absorption and assimilation in the body of animals/organisms.
Food : A substance which is taken and digested in the body to provide 
material for growth, repair & energy for reproduction and resistance from disease 
or regulation of body processes.
Thecodont : The teeth embedded in the sockets of the jaw bone, e.g., in 
mammals.
Diphyodont : The teeth formed twice in life time e.g., in mammals.
Heterodont : Different types of teeth. An adult human has 32 permanent 
teeth which are of four different types.
Different Types of Teeth
(a) Canine—for tearing
(b) Incisors—for cutting
(c) Premolars for grinding
(d) Molars for churning and grinding
Crown
Root
Dental formula of man :
Permanent Teeth)
1 C PM M
32 = 2 × 2 1 2 3 Upper Jaw
2 1 2 3 Lower Jaw
Dental formula of man :
(Milk Teeth)
1 C PM 
20 = 2 × 2 1 2 Upper Jaw
2 1 2 Lower Jaw
Peristalsis : The involuntary moveent of the gut by which the food bolus 
is pushed forward. 
Deglutition : The process of swallowing of food bolus. It is partly voluntary 
and partly involuntary.
Ruminants : The herbivours animals (e.g., cow, buffalo etc.) which have 
symbiotic bacteria in their rumen of their stomach which synthesize enzymes to 
hydrolyse cellulose into monosaccharides.
Diarrhoea : The abnormal frequent discharge of semisolid or fluid faecal 
matter from the bowel.
Vomitting : The ejection of stomach contents through the mouth, caused 
by antiperistalsis.
Dysentery : Frequent watery stools often with blood and mucus and with 
pain, fever and causes dehydration.
Chyme : The semifluid mass into which food is converted by gastric secretion 
and which passes from the stomach into the small intestine.
Gastric : Anything associated with stomach is given a prefix ‘gastric’.
Proenzyme : The inactive forms of enzymes.
Sphincter : A flap like structure at various junctions of the alimentary canal  
which facilities one way traffic (movement of material) in the alimentary canal.
Bolus : The masticated food mixed with saliva.
Hepatic : Anything associated with liver is given a prefix ‘hepatic’.
Goblet cells : The cells of intestinal mucosal epithelium which secrete 
muscus.  
Glisson’s capsule : The connective tissue sheath which covers the hepatic 
lobules of liver.
Hepatic lobules : The structural and functional units of liver containing 
hepatic cells which are arranged in the form of cords.
Sphincter of Oddi : The sphincter which guard the opening of common 
hepatopancretic duct.
Villi : The small finger-like folding in the small intestine which increase the 
surface area for absorption of digested food.
Crypts of Lieberkuhn–pits of intestine 
Success entericus—Intestinal juices.
Types of Nutrition
Autotrophic Heterotrophic
Photoautotrophic Chemoautrophic 1. Saprophytic (e.g., yeast)
(e.g., green plants (e.g., Nitrosomonas 2. Holotrophic (e.g., man, lion)
& Euglena etc.) & Nitrobacter 3. Parastic (e.g., Ascaris)
Page 4


Points To Remember
Digestion : The process in alimentary canal  by which the complex food is 
converted mechanically and biochemically into simple substances suitable for 
absorption and assimilation in the body of animals/organisms.
Food : A substance which is taken and digested in the body to provide 
material for growth, repair & energy for reproduction and resistance from disease 
or regulation of body processes.
Thecodont : The teeth embedded in the sockets of the jaw bone, e.g., in 
mammals.
Diphyodont : The teeth formed twice in life time e.g., in mammals.
Heterodont : Different types of teeth. An adult human has 32 permanent 
teeth which are of four different types.
Different Types of Teeth
(a) Canine—for tearing
(b) Incisors—for cutting
(c) Premolars for grinding
(d) Molars for churning and grinding
Crown
Root
Dental formula of man :
Permanent Teeth)
1 C PM M
32 = 2 × 2 1 2 3 Upper Jaw
2 1 2 3 Lower Jaw
Dental formula of man :
(Milk Teeth)
1 C PM 
20 = 2 × 2 1 2 Upper Jaw
2 1 2 Lower Jaw
Peristalsis : The involuntary moveent of the gut by which the food bolus 
is pushed forward. 
Deglutition : The process of swallowing of food bolus. It is partly voluntary 
and partly involuntary.
Ruminants : The herbivours animals (e.g., cow, buffalo etc.) which have 
symbiotic bacteria in their rumen of their stomach which synthesize enzymes to 
hydrolyse cellulose into monosaccharides.
Diarrhoea : The abnormal frequent discharge of semisolid or fluid faecal 
matter from the bowel.
Vomitting : The ejection of stomach contents through the mouth, caused 
by antiperistalsis.
Dysentery : Frequent watery stools often with blood and mucus and with 
pain, fever and causes dehydration.
Chyme : The semifluid mass into which food is converted by gastric secretion 
and which passes from the stomach into the small intestine.
Gastric : Anything associated with stomach is given a prefix ‘gastric’.
Proenzyme : The inactive forms of enzymes.
Sphincter : A flap like structure at various junctions of the alimentary canal  
which facilities one way traffic (movement of material) in the alimentary canal.
Bolus : The masticated food mixed with saliva.
Hepatic : Anything associated with liver is given a prefix ‘hepatic’.
Goblet cells : The cells of intestinal mucosal epithelium which secrete 
muscus.  
Glisson’s capsule : The connective tissue sheath which covers the hepatic 
lobules of liver.
Hepatic lobules : The structural and functional units of liver containing 
hepatic cells which are arranged in the form of cords.
Sphincter of Oddi : The sphincter which guard the opening of common 
hepatopancretic duct.
Villi : The small finger-like folding in the small intestine which increase the 
surface area for absorption of digested food.
Crypts of Lieberkuhn–pits of intestine 
Success entericus—Intestinal juices.
Types of Nutrition
Autotrophic Heterotrophic
Photoautotrophic Chemoautrophic 1. Saprophytic (e.g., yeast)
(e.g., green plants (e.g., Nitrosomonas 2. Holotrophic (e.g., man, lion)
& Euglena etc.) & Nitrobacter 3. Parastic (e.g., Ascaris)
Basic Steps of Holozoic Nutrition :
 (1) Ingestion : Intake of food.
 (2) Digestion : Breaking down of complex organic food materials into simpler, 
smaller water soluble molecules.
 (3) Absorption and assimilation : Absorption of digested food into blood or 
lymph and its use in the body cells for synthesis of complex components.
 (4) Egestion : Elimination of undigested food as faeces :
 Digestive glands : (A) Salivary gland—3 types are (1) Parotids (cheek)
(ii) Sublinguals (Below the tongue) (iii) Submaxillary or submandibular 
(lower jaw) Secrete saliva which contains ptyalin (Salivary Amylase).
 (B) Pancreas : A dual gland that secretes pancreatic juice and also secretes 
Hormones. 
 Malnutrition—When a person is not getting enough food or getting 
unbalanced diet.
PEM—Protein Energy Malnutrition
Kwashiorkar Marasmus
 The word means ‘rejected child’                 Word marasmus means working  
 away
  ? It is a disorder found in children ? Child remaining under-nourished  
1-5 years of age, where child is  suffer from marasmus. Usually 
weaned off mother’s milk very early .  found in children below the age
 of 1 year.
  ? Children get low protein and low ? It is caused by deficiency of 
carbohydrate diet are affe cted.  protein & carbohydrate & fat.
Page 5


Points To Remember
Digestion : The process in alimentary canal  by which the complex food is 
converted mechanically and biochemically into simple substances suitable for 
absorption and assimilation in the body of animals/organisms.
Food : A substance which is taken and digested in the body to provide 
material for growth, repair & energy for reproduction and resistance from disease 
or regulation of body processes.
Thecodont : The teeth embedded in the sockets of the jaw bone, e.g., in 
mammals.
Diphyodont : The teeth formed twice in life time e.g., in mammals.
Heterodont : Different types of teeth. An adult human has 32 permanent 
teeth which are of four different types.
Different Types of Teeth
(a) Canine—for tearing
(b) Incisors—for cutting
(c) Premolars for grinding
(d) Molars for churning and grinding
Crown
Root
Dental formula of man :
Permanent Teeth)
1 C PM M
32 = 2 × 2 1 2 3 Upper Jaw
2 1 2 3 Lower Jaw
Dental formula of man :
(Milk Teeth)
1 C PM 
20 = 2 × 2 1 2 Upper Jaw
2 1 2 Lower Jaw
Peristalsis : The involuntary moveent of the gut by which the food bolus 
is pushed forward. 
Deglutition : The process of swallowing of food bolus. It is partly voluntary 
and partly involuntary.
Ruminants : The herbivours animals (e.g., cow, buffalo etc.) which have 
symbiotic bacteria in their rumen of their stomach which synthesize enzymes to 
hydrolyse cellulose into monosaccharides.
Diarrhoea : The abnormal frequent discharge of semisolid or fluid faecal 
matter from the bowel.
Vomitting : The ejection of stomach contents through the mouth, caused 
by antiperistalsis.
Dysentery : Frequent watery stools often with blood and mucus and with 
pain, fever and causes dehydration.
Chyme : The semifluid mass into which food is converted by gastric secretion 
and which passes from the stomach into the small intestine.
Gastric : Anything associated with stomach is given a prefix ‘gastric’.
Proenzyme : The inactive forms of enzymes.
Sphincter : A flap like structure at various junctions of the alimentary canal  
which facilities one way traffic (movement of material) in the alimentary canal.
Bolus : The masticated food mixed with saliva.
Hepatic : Anything associated with liver is given a prefix ‘hepatic’.
Goblet cells : The cells of intestinal mucosal epithelium which secrete 
muscus.  
Glisson’s capsule : The connective tissue sheath which covers the hepatic 
lobules of liver.
Hepatic lobules : The structural and functional units of liver containing 
hepatic cells which are arranged in the form of cords.
Sphincter of Oddi : The sphincter which guard the opening of common 
hepatopancretic duct.
Villi : The small finger-like folding in the small intestine which increase the 
surface area for absorption of digested food.
Crypts of Lieberkuhn–pits of intestine 
Success entericus—Intestinal juices.
Types of Nutrition
Autotrophic Heterotrophic
Photoautotrophic Chemoautrophic 1. Saprophytic (e.g., yeast)
(e.g., green plants (e.g., Nitrosomonas 2. Holotrophic (e.g., man, lion)
& Euglena etc.) & Nitrobacter 3. Parastic (e.g., Ascaris)
Basic Steps of Holozoic Nutrition :
 (1) Ingestion : Intake of food.
 (2) Digestion : Breaking down of complex organic food materials into simpler, 
smaller water soluble molecules.
 (3) Absorption and assimilation : Absorption of digested food into blood or 
lymph and its use in the body cells for synthesis of complex components.
 (4) Egestion : Elimination of undigested food as faeces :
 Digestive glands : (A) Salivary gland—3 types are (1) Parotids (cheek)
(ii) Sublinguals (Below the tongue) (iii) Submaxillary or submandibular 
(lower jaw) Secrete saliva which contains ptyalin (Salivary Amylase).
 (B) Pancreas : A dual gland that secretes pancreatic juice and also secretes 
Hormones. 
 Malnutrition—When a person is not getting enough food or getting 
unbalanced diet.
PEM—Protein Energy Malnutrition
Kwashiorkar Marasmus
 The word means ‘rejected child’                 Word marasmus means working  
 away
  ? It is a disorder found in children ? Child remaining under-nourished  
1-5 years of age, where child is  suffer from marasmus. Usually 
weaned off mother’s milk very early .  found in children below the age
 of 1 year.
  ? Children get low protein and low ? It is caused by deficiency of 
carbohydrate diet are affe cted.  protein & carbohydrate & fat.
Symptoms
 Kwashiorkar  Marasmus
 1. Stunted growth 1. Low body weight
2. Dry & scaly skin 2. Wasting of muscles
3. Odema (retention of water in tissues) 3. Prominent ribs
4. Match stick lags 4. Sunken Eyes
5. Protruted Belly 5. Lean body with thin limbs
6. Mental retardation
Cure
 Feeding the child with protein rich Child  should  be  given  protein 
diet  including milk, soyabean, diet with enough quantity of
egg etc.   carbohydrates & fats.
Calorific Value : Amount of heat energy released by 1 gm of substrate after 
complete Oxidation.
Calorific value of Carbohydrates is 4.1 k.cal/g = 17.1 kj/g
Protein is 5.6 kcal/g = 23.4 kj/gm
Fats is 9.4 kcal/g (app.) = 39.2 kj/gm