CH9 Flashcards
Digestion in mouth
Chemical digestion
Presence of food stimulate salivary gland to secrete salivary amylase
Salivary Amylase hydrolyse starch into maltose
Physical digestion
Food is chewed in mouth into bolus
Swallowing allow bolus to enter oesophagus
Peristaltic action and secretion of mucus by mucous gland of oesophagaeal wall facilitate movemt of bolus along the oesophagus
Digestion in stomach
Gastric glands at stomach walls secrete gastric juices that contain Hydrochloric acid, Pepsinogen and mucus
Hydrochloric acid functions to:
Provide acidic medium to stop action of salivary amylase, to provide optimum pH value of enzymatic action of pepsin and kills bacteria in food
Activate pepsinogen into pepsin
Mucus protect wall of stomach from acidity oh Hydrochloric acid
Pepsin catalyses hydrolysis of protein into polypeptides
Food is kept in stomach for a few hours
Enzymatic action and peristaltic action of stomach wall muscles change bolus into chyme
Entrance of chyme into duodenum is regulated by pyloric sphincter muscle.
As pyloric sphincter muscle relax, chyme slowly enter the duodenum
5 Bile related terms
Bile ; neutralises acidic chyme, provide alkaline medium for enzymatic action in duodenum and emulsify lipids (breaking down lipid into tiny droplets)
Gallbladder; stores bile
Liver produce biles
Bile duct carries bile into duodenum
Digestion in Duodenum
Pancreas secrete pancreatic juices;
Lipase hydrolyse lipid > glycerol and fatty acid
Pancreatic amylase hydrolyse starch > maltose
Trypsin hydrolyse Polypeptides > peptides
Intestinal gland secrete intestinal juice;
Maltase hydrolyse maltose > glucose
Lactase hydrose Lactose > glucose + galactose
Sucrase hydrolyse sucrose > glucose + fructose
Erepsin hydrolyse Peptide > amino acids
Adaptation of small intestines for absorption
5-6 meter long in adult; allow longer digestion and absorption periods
Inner wall is covered with villi projections; increase surface area for absorptions of food
Damp inner surface; allow nutrients to dissolve
Villus is lined with epithelial cells; facilitate absorption of nutrients into blood capillaries or lacteal
Consist of blood capillary; transport digestive products to body tissues and organ
Consist of lacteal; transport droplets of fatty acid and glycerol
Consist of goblet cells; secrete mucus to lubricate movement of undigested food
Epithelial layer of villus is one cell thick; accelerate nutrient absorption
Microvillus on villus epithelium; increase surface area for nutrient absorptions
Assimilation in liver
Amino acids
Excess amino acids undergoes deamination to produce urea
Amino acids is converted to glucose when glucose supply is insufficient
Glucose
Insulin convert glucose into glycogen when glucose level is high
Glucagon covert glycogen into glucose when glucose level is low
When glycogen supply has reached maximum level, excess glucose is converted to lipids
Assimilation in body cells
Amino acids are used to synthesise new protoplasm, hormones and enzyme and repair damaged tissues
Glucose is oxidised through cellular respiration to produce atp, water, carbon dioxide.
excess glucose is kept as glycogen in muscles
Excess fats are kept in adipose tissue
Formation of faece
After water is absorbed, the remaining waste is called faece
Faece contains dead cell of inner layer of intestines and waste products
Walls of large intestine secrete mucus to facilitate movement of faece
Faece accumulates in the rectum until pressure inside rectum increases
Rectum muscles contract to expel faece
