Flashcards For NEET Biology - Digestion and Absorption

Thecodont

The base of the tooth in the socket of bone

Diphyodont

Two successive sets of teeth

Heterodont

Different types of teeth

Incisors, canine, premolars and molars

Dental formula 2123

2123

Tongue

Attached to the oral cavity by the frenulum

Papillae- small projections, some have taste buds

Epiglottis

Cartilaginous flap, which prevents food from entering glottis

Pyloric sphincter

Guards opening of the stomach into the duodenum

Caecum

Hosts symbiotic microorganisms

Vermiform appendix arise fro caecum

Serosa

The outermost layer of the alimentary canal

Thin mesothelium and some connective tissues

Muscularis

Comes after serosa

Inner circular and outer longitudinal

Made up of smooth muscles

Submucosa

Made up of loose connective tissues

Contains nerves, blood and lymph vessels

Brunner’s glands in the duodenum are present in sub-mucosa

Mucosa

The innermost wall of the alimentary canal, lines the lumen

Forms irregular folds rugae in stomach

Goblet cells- secrete mucus

Contains gastric glands

Villi

Finger-like foldings in the intestine and increase absorption surface

Supplied by blood capillaries and a large lymph vessel called lacteals

Salivary Glands

Parotid- cheek

Submaxillary/ submandibular- lower jaw

Sublingual- below the tongue

Salivary amylase

Source- salivary glands

Function- carbohydrate digestion starts here

Starch (30%) is converted to disaccharide, maltose. Optimum pH 6.8

Lysozyme

Source- saliva

Function- antibacterial and protects from infection

Pepsin

Source- Peptic or chief cells of the stomach as proenzyme pepsinogen

Function- Proteolytic, converts proteins to peptides

HCl

Source- Parietal or oxyntic cells

Function- converts pepsinogen to pepsin and provides acidic pH (1.8) for the action of pepsin

Rennin

Source- chief cells of infants as prorennin

Function- digestion of milk protein casein

Intrinsic factor

Source- Parietal or oxyntic cells

Function- Absorption of vitamin B₁₂

Enterokinase

Source- Intestinal mucosa

Function- converts trypsinogen to active enzyme trypsin

Bile

Source- Produced by liver, stored in gallbladder and released into duodenum by hepatopancreatic duct

Contains- Bilirubin, biliverdin, cholesterol, phospholipids, bile salts, no enzymes

Function- Emulsification of fats and activation of pancreatic lipases

Brunner’s glands

Present in- Submucosal layer of duodenum

Function- Protects intestinal mucosa from acid content of chyme and provides an alkaline medium for enzyme activity (pH=7.8)

Chyme

Semifluid acidic mass of partly digested food which enters duodenum from the stomach

Secretin

Source- A hormone secreted by S-cells of the duodenum (enteroendocrine cells)

Function- Stimulates secretion of pancreatic bicarbonate, regulation of gastric acid secretion and osmoregulation

Cholecystokinin

Source- Secreted in the duodenum by I cells

Function- Stimulates gallbladder to secrete bile juice and stimulates enzyme production by the pancreas

Sphincter of Oddi

Guards the opening of the hepatopancreatic duct into the duodenum

Goblet cells

Present in- the intestinal mucosal epithelium

Secrete- mucus containing a glycosylated protein called mucin

Function- Lubrication and protection of the intestinal mucosa from acid

Trypsin

Source- Pancreas as a proenzyme trypsinogen

Function- Activates other proenzymes of pancreatic juice and proteolytic enzyme

Chymotrypsin

Source- Pancreas as a proenzyme chymotrypsinogen

Function- proteolytic enzyme, converts polypeptides to dipeptides

Crypts of Lieberkuhn

Crypts at the bases of villi in the mucosa layer of the intestine

Carboxypeptidase

Source- Pancreas as a proenzyme procarboxypeptidase

Function- Protease enzyme, hydrolyses carboxy-terminal of a protein or peptide

Pancreatic amylase

Source- Pancreas

Function- Polysaccharide into a disaccharide

Pancreatic lipases

Source- Pancreas

Function- Digestion of fats to di and monoglycerides

Nucleases

Source- Pancreas

Function- Converts nucleic acids to nucleotides and nucleosides

Succus entericus

Intestinal juice (alkaline)

Secreted by- glands of the intestinal wall (goblet cells, brush-border epithelium)

Contains- Mucus, Enzymes- enterokinase, dipeptidases, nucleosidases, lipases, disaccharidases (maltase, lactase, etc.)

Gastric lipases

Source- Peptic cells or chief cells of the stomach

Function- small amount ~1% of emulsified fat in the food is digested to fatty acid and glycerol

Dipeptidase

Source- Small intestine

Function- Dipeptides to amino acids

Maltase

Source- Small intestine

Function- Maltose to glucose

Sucrase

Source- Small intestine

Function- Sucrose to glucose and fructose

Lactase

Source- Small intestine

Function- Lactose to glucose and galactose

Nucleotidases

Source- Small intestine

Function- Nucleotides to nucleosides

Nucleosidases

Source- Small intestine

Function- Nucleosides to sugar and bases

Lipases

Source- Small intestine

Function- Mono and diglycerides to fatty acids and glycerol

Physiologic Calorific value

Fats- 9 kcal/g

Carbohydrates- 4 kcal/g

Proteins- 4 kcal/g