DIGESTION AND ABSORPTION www sblifescience in 1 MAJOR

DIGESTION AND ABSORPTION • www. sblifescience. in • 1

MAJOR COMPONENTS OF FOOD • • www. sblifescience. in Carbohydrates Proteins Fats Vitamins Minerals Water • 2

DIGESTION • The process of conversion of complex food substances to simple absorbable form is called digestion. • www. sblifescience. in • 3

HUMAN DIGESTIVE SYSTEM Alimentary canal Associated glands • www. sblifescience. in • 4

DIGESTIVE SYSTEM OF MAN • www. sblifescience. in • 5

ORAL CAVITY (BUCCAL CAVITY) • Teeth • Tongue • Palate(roof) • www. sblifescience. in • 6

TEETH Dentition Refers the number, kinds and arrangement of teeth Thecodont Heterodont Diphyodont • www. sblifescience. in • 7

THECODONT • Teeth are placed in jaw sockets • www. sblifescience. in • 8

HETERODONT • Teeth are different types or dissimilar Incisors Canine Premolars Molars • www. sblifescience. in • 9

DIPHYODONT • Teeth appear twice in the whole life • Milk teeth • Permanent teeth • www. sblifescience. in • 10

DENTAL FORMULA The kind and number of teeth are explained in the form of formula is called dental formula. • Adult 32 permanent teeth • Incisors 2/2 • Canine 1/1 • Premolars 2/2 • Molars 3/3 • Child 20 milk teeth • Incisors 2/2 • Canine 1/1 • Premolars 0/0 • Molars 2/2 • www. sblifescience. in • 11

WISDOM TEETH • Third molar appears after the age of 20 years and hence is called wisdom teeth. • www. sblifescience. in • 12

STRUCTURE OF TOOTH Crown Neck Root Odontoblast Found in the dental pulp secrete dentine • www. sblifescience. in • 13

TONGUE • Freely movable muscular organ attached to the floor of the buccal cavity by frenulum. • www. sblifescience. in • 14

TONGUE • The upper surface of the tongue has small projections called papillae, some of which bear taste buds. • www. sblifescience. in • 15

PHARYNX • Common passage for digestive and respiratory system. • Opening of oesophagus • Opening of larynx Glottis • www. sblifescience. in • 16

GLOTTIS • Glottis is guarded by a flap of tissue called epiglottis. • When food materials pass through the pharynx the epiglottis closes the glottis. • www. sblifescience. in • 17

OESOPHAGUS • • Narrow muscular tube 30 cm long Leads to stomach Pass through the diaphragm (a muscular partition that separates thorax from abdomen). • www. sblifescience. in • 18

OESOPHAGEAL SPHINCTER (GASTRO OESOPHAGIAL SPHINCTER) • Posterior region of the oesophagus there is a ring of muscle called oesophagial sphincter. • It controls the opening of the oesophagus into the stomach. • www. sblifescience. in • 19

PERISTALSIS • The movement of food materials in the esophagus is effected by the wave like contraction and relaxation of longitudinal and circular muscles of the esophagus is known as peristalsis. • www. sblifescience. in • 20

STOMACH • Large muscular ‘J’ shaped sac. • Lying just below the diaphragm in the abdominal cavity. • Three major parts – Cardiac – Fundic – Pyloric • www. sblifescience. in • 21

PYLORIC SPHINCTER • The opening of the stomach into the duodenum is guarded by pyloric sphincter. • Controls the flow of food to the intestine. • www. sblifescience. in • 22

SMALL INTESTINE • Long, highly coiled, narrow tube • Seven metres long • 2. 5 cm diametre • Divided in to duodenum, jejunum & ileum. • www. sblifescience. in • 23

DUODENUM • • First part of SI ‘U’ shaped Area of digestion Receives common opening of the bile and pancreatic duct. • www. sblifescience. in • 24

JEJUNUM • Coiled and longer • www. sblifescience. in • 25

ILEUM • Highly coiled • Opens into the large intestine • Area of absorption • www. sblifescience. in • 26

LARGE INTESTINE • 1. 5 metres long • Differentiated into Caecum , Colon & Rectum • www. sblifescience. in • 27

CAECUM • Small blind sac (at the junction of SI &LI) • Plays no role in Nutrient absorption. • It hosts some symbiotic microorganisms. • Caecum bears a finger like out growth of unknown function known as Vermiform Appendix. • www. sblifescience. in • 28

COLON ( Pelvic colon) • www. sblifescience. in • 29

RECTUM • Temporary storage of faeces • Rectum opens out by Anus. • www. sblifescience. in • 30

HISTOLOGY OF HUMAN GUT ( Outer most ) forms a fibrous coat Smooth muscle Loose connective tissue layer with blood & lymph vessels (Inner most)-made of secretary & absorptive cells • www. sblifescience. in • 31

RUGAE • Mucosal layer forms irregular fold in the stomach called rugae. • www. sblifescience. in • 32

VILLI Villus • (Sing: - Villus) • Mucosal layer forms small finger like folding in the small intestine called Villi • A villus is about 0. 5 to 1 mm long • www. sblifescience. in • 33

VILLI • www. sblifescience. in • 34

VILLI • www. sblifescience. in • 35

VILLI • www. sblifescience. in • 36

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MICROVILLI • Each villus has numerous electron microscopic evaginations called microvilli. • Both villi & micro villi increases the surface area for digestion and absorption of food • www. sblifescience. in • 38

DIGESTIVE GLANDS • • • Salivary glands Pancreas Liver Gastric glands Intestinal glands • www. sblifescience. in • 39

DIGESTIVE ENZYMES • Carbohydrase ( amylase ) carbohydrate digesting E. g. : ptyalin, maltose etc • Hydrolyses Group of enzymes released from the cells digestive system play a major role in the extra cellular digestion in human • Proteases (protein digesting) Eg: amino peptidase, dipeptidase . Lipase (lipid digesting) • www. sblifescience. in • 40

SALIVARY GLANDS • Secrete saliva • Found in buccal cavity • Three pairs of salivary glands 1. Parotid glands (largest) 2. Sub lingual glands 3. Sub maxillary (Sub mandibular) • www. sblifescience. in • 41

SALIVA • Derived from blood plasma • Secrete 1. 5 liters of saliva per day • Slightly alkaline • Contain water & electrolyte (Na+, K+, Cl-, HCO 3 -) • Mucin, ptyalin, lyzozyme & inorganic salts • Ptyalin digest starch in to maltose • www. sblifescience. in • 42

LIVER • Largest gland in the human body • Weighs about 1. 5 kg in adult man • Bi lobed • Secrete bile • www. sblifescience. in • 43

LIVER • Each lobe is separated into numerous tiny hepatic lobules, which are the functional units. • A lobule is formed of numerous hepatic cells – bile is secreted by hepatic cells • Each lobule is covered by a thin connective tissue sheath called Glisson’s capsule • www. sblifescience. in • 44

HEPATIC LOBULES • www. sblifescience. in • 45

GALL BLADDER • Bile is stored and Concentrated in a thin muscular sac called gall bladder. • Capacity- 40 – 60 ml • Absent in whale, horses, rats etc. • www. sblifescience. in • 46

BILE • • Golden yellow or greenish fluid Alkaline nature Bile pigments (product of dead RBC) (biliverdin & bilirubin) Bile salts, cholesterol, phospholipids Bile salts play a very important role in the emulsification of fat • www. sblifescience. in • 47

GALL BLADDER • The duct of gall bladder (cystic duct) along with hepatic duct from the liver forms a common bile duct. • www. sblifescience. in • 48

GALL BLADDER • The bile duct and pancreatic duct opens together into the duodenum as common hepato - pancreatic duct, which is guarded by a sphincter called sphincter of Oddi. • www. sblifescience. in Hepato - Pancreatic duct • 49

PANCREAS • Located between stomach & duodenum • Second largest glands • Heterocrine gland (both exocrine &endocrine) • Pancreatic duct opens into the duodenum along with bile duct • Secrete pancreatic juice. • www. sblifescience. in • 50

PANCREATIC JUICE • Alkaline nature • Trypsinogen , Chymotrypsinogen Proarboxypeptidase, Amylopsin (p. amylase) • Steapsin (pancreatic lipase) • Nuclease (Nucleic acid digesting enzyme) • www. sblifescience. in • 51

GASTRIC GLANDS • Found on the wall of stomach • Formed of three kinds of cells 1. Mucous cells 2. Chief cells or Zymogen cells 3. Oxyntic cells or Parital cells • www. sblifescience. in • 52

GASTRIC GLANDS mucus secreting • www. sblifescience. in • 53

GASTRIC GLANDS • www. sblifescience. in • 54

GASTRIC SECRETIONS Name of Cell Function Mucous cells (Goblet cells) Secrete mucous Oxyntic cells or Parital cells Secretion of HCl and intrensic factor (factor essential for the absorption of vitamin B 12) Chief cells or Zymogen cells Secretion of enzymes such as pepsin , rennin, lipase etc. • www. sblifescience. in • 55

HCl • Inactivate the secretion of salivary amylase. • Kills micro organism • Lowers the p. H of the stomach (1. 5 to 2. 5) • Activate proenzyme pepsinogen to active pepsin. • www. sblifescience. in • 56

INTESTINAL GLANDS • Simple tubular glands found throughout SI • Two types Crypts of Lieberkuhn Glands of Brunner • www. sblifescience. in • 57

CRYPTS OF LIEBERKUHN villus • Goblet cells – Mucous secreting • Paneth cells – Enzyme secreting Many surface area of gastro intestinal tract are lined by evaginations of the epithelium in to sub mucosa similar to pits. These pits of the intestine are called Crypts of Lieberkuhn crypt Paneth cells Goblet cells • www. sblifescience. in • 58

GLANDS OF BRUNNER ( DUODENAL GLANDS) • Confined to the sub mucosa of the duodenum and secrete mucus only • www. sblifescience. in • 59

INTESTINAL JUICE (SUCCUS ENTERICUS) • Collective secretions of intestinal glands • Alkaline nature • Contain enzymes , mucous & inorganic salts. • Proteases Aminopeptidase, Dipeptidase • Amylase Maltase, Isomaltase Lactase, Surcease • Lipase • Enterokinase • www. sblifescience. in • 60

DIGESTION • The teeth and tongue with the help of saliva masticate and mix up the food into bolus. • The bolus is conveyed to pharynx and then to oesophagus by swallowing or deglutition. • www. sblifescience. in • 61

DIGESTION • The stomach stores the food 4 -5 hrs. The food mixes thoroughly with acidic gastric juice to form paste. - Chyme • www. sblifescience. in • 62 chyme

CARBOHYDRATE DIGESTION Buccal cavity Salivary amylase • Starch Maltose Stomach No carbohydrate digestion Small Intestine P. amylase Maltose Maltase 2 Glucose Lactase Starch Glucose + Galactose Sucrose • www. sblifescience. in Sucrase Glucose + Fructose • 63

Buccal cavity PROTEIN DIGESTION No protein digestion Stomach Pepsinogen Protein HCl Pepsin Small intestine Pepsin Peptones + Proteoses Trypsinogen Enterokinase Trypsin Chymotrypsinogen Chymotrypsin Procarboxy peptidase Proteins Peptones = larger peptides Proteoses = smaller peptides Carboxy peptidase Trypsin / Chymotrypsin Carboxy peptidase Dipeptides Proteoses • www. sblifescience. in Dipeptides Dipeptidase • 64 Amino acids

Buccal cavity FAT DIGESTION No protein digestion Stomach Gastric lipase hydrolyses only a small amount of fat Small intestine Fat Bile Fat droplets Emulsification Fat Pancreatic lipase Diglyceride Monoglycerides • www. sblifescience. in Fatty acids & Glycerol • 65

NUCLEIC ACID DIGESTION Small Intestine Nucleic acids Nucleotides Nucleosides • www. sblifescience. in Sugar + Bases • 66

END PRODUCTS OF DIGESTION Carbohydrates Proteins Fats Glucose Fructose Galactose Amino acids Fatty acids glycerol • www. sblifescience. in • 67

DIGESTION • Complete digestion of food take place in the duodenum. The fully digested food is semi fluid in nature and is known as Chyle • www. sblifescience. in • 68

ABSORPTION OF DIGESTED PRODUCTS • Absorption is the process by which the end products of digestion pass through the intestinal mucosa ( transported through the intestinal mucosa) into the blood or lymph • The end products of digestion are absorbed in the jejunum and ileum regions of small intestine. • www. sblifescience. in • 69

ABSORPTION Absorption is carried out by – Passive transport – Facilitated transport – Active transport • www. sblifescience. in • 70

PASSIVE TRANSPORT • Small amounts of monosaccharide like glucose, amino acids, and some of electrolytes like chloride ions are generally absorbed by simple diffusion. • www. sblifescience. in • 71

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FACILITATED TRANSPORT • Fructose and some amino acids are absorbed with the help of carrier ions like sodium. This mechanism is called facilitated transport. • www. sblifescience. in • 73

ACTIVE TRANSPORT • Requires energy • Various nutrients like amino acids, monosaccharide like glucose, electrolytes like Na+ are reabsorbed into the blood by active transport. • www. sblifescience. in • 74

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ABSORPTION OF FAT • Fatty acids and glycerol insoluble in water so they cannot be absorbed directly from the lumen of the intestine. • With the help of bile salts & phospholipids the fatty acids and glycerol are converted into small spherical water soluble droplets called micelles. • www. sblifescience. in • 76

ABSORPTION OF FAT Micelles are reformed into very small protein coated fat globules called chylomicrons. Which are transported in to the lymph vessels (lactales)in the villi. • www. sblifescience. in • 77

ABSORPTION OF FAT • www. sblifescience. in • 78

LARGE INTESTINE • No significant digestive activity occurs in the large intestine. Functions Absorption of water, minerals and certain drugs. Secretion of mucus which helps in adhering waste. • www. sblifescience. in • 79

LARGE INTESTINE • The undigested and unabsorbed substances (faeces) enters into the caecum of the large intestine through the ileo caecal valve, which prevents the back flow of faecal matter. • www. sblifescience. in • 80

EGESTION • The egestion of faeces to the outside through the anal opening (defaecation) is a voluntary process and is carried out by a mass peristaltic movement. • www. sblifescience. in • 81

THE SUMMARY OF ABSORPTION IN DIFFERENT PARTS OF DIGESTIVE SYSTEM Oral cavity Stomach Certain drugs Water, simple coming in sugars, alcohol contact with the mucosa of the mouth and lower side of the tongue are absorbed into the blood capillaries lining them. Small Intestine Large Intestine Glucose Fructose Fatty acids Glycerol Amino acids Water , some minerals, drugs • www. sblifescience. in • 82

DISORDERS OF DIGESTIVE SYSTEM Bacteria Tape worm • Infections of the digestive system are caused by bacteria, virus, parasites like tape worm, thread worm, round worm, hook worm, pinworm etc. • www. sblifescience. in Virus Pinworm • 83 Thread worm

VOMITING • It is the ejection of stomach content through the mouth. • www. sblifescience. in • 84

DIARRHOEA • The abnormal frequency of bowel movement and increased liquidity of faecal discharge is known as diarrhoea. • It reduces the absorption of food. • www. sblifescience. in • 85

JAUNDICE • The liver is affected, skin, eyes turn yellow due to the deposition of bile pigments. • www. sblifescience. in • 86

CONSTIPATION • The faeces are retained with in the rectum as the bowel movement occur irregularly. • www. sblifescience. in • 87

INDIGESTION • The food is not properly digested leading to the feeling of fullness. • The cause of indigestion are inadequate enzyme secretion, anxiety, food poisoning, overeating and spicy food. • www. sblifescience. in • 88