Digestive system
Ingestion - process of food material intake passing through alimentary canal
Mouth - food enters the gastrointestinal tract through the mouth; both chemical and mechanical digestion starts
here
Digestion - ingested food is broken down
Teeth - normal adults has 32 teeth on average
A. Incisors - 8 to cut food
B. Canine - 4 to pierce and tear food
C. Bicuspids - 8 to pierce and tear
D. Molars - crush and grind 12
Tongue - help to physically break apart food
In the mouth salivary glands produce saliva that contains the enzyme amylase - acts on starch breaking it into
maltose
Bolus - resulting ball of food in the mouth
Sphincter - a muscle that controls the opening:
1. Cardiac - esophagus and stomach
2. Pyloric - stomach and duodenum
Gastric Juices
- water - liquefy the swallowed food
- HCL - provide acid environment which is needed for action of pepsin. Fibrous tissue
- Pepsin - protein - helps in digestion of protein break them into smaller molecules
- Intrinsic factor - need for the absorption of the VITAMIN B12
- Mucus - prevent mechanical injury to the stomach wall by lubricating the content. Acts as a barrier
between stomach wall and hcl acid
Chyme - semi fluid mass pf partly digested food that is formed in the stomach and intestine during
digestion
Functions of stomach
* acts as a temporary storage of food
* Chemical digestion - pepsin break protein in to polypeptide
* Mechanical breakdown - 3 smooth muscle layer enable the stomach to act as a churn
* Preparation of iron for absorption
Small intestine
- chemical digestion of food completed and absorption of most nutrient takes place
- 2.5 cm diameter, 5 meter long
- Join the large intestine - ileocaecal valve
- Onward movement of intestinal content by parasympathetic simulation
- Completion of chemical digestion
Chemical - where many enzymes complete the digestive process
Physical - villi and microvilli help separate food particles
Chemical digestion associated with enterocytes
Peptides - breakdown polypeptides into smaller peptides & amino acids
Lipase - complete the digestion of fat to fatty acid
Sucrase, maltase, lactase - complete the digestion of carbohydrate by converting disaccharides such as
sucrose, maltose & lactose to monosaccharide
Accessory organs
Pancreas - releases sodium bicarbonate to neutralize acidic chyme - releases digestive enzyme
Pancreatic amylase - starch
Lipase - lipids
Trypsin - polypeptides
Regulates blood sugar by producing insulin
Liver - secretes bile - storage of fats
Gall bladder - small sac near liver - stores bile
