Digestive enzymes Recap Starch Proteins Lipids/ Fats maltose AMYLASE Starch maltose PROTEASE Proteins amino acids LIPASE Lipids/ Fats fatty acids & glycerol

identify and describe the main regions of alimentary canal describe the functions of the parts of the human gut and the associated organs

Pathway of Digestion in Alimentary Canal Mouth ↓ Oesophagus Stomach Small Intestines Large Intestines Rectum Anus

Digestion is the process of breaking down complex, large molecules (food) into simple, soluble and diffusible molecules so that it can be absorbed by the body and be used to build and nourish cells and to provide energy.

Functions of digestive system: (1) Ingestion: taking food into the body. (2) Digestion: breakdown of food materials into smaller amounts        (i) Mechanical digestion       (ii) Chemical digestion (3) Absorption (4) Assimilation (5) Egestion

Types of digestion: (i) Mechanical digestion Break down particles into smaller pieces so as to increase the surface area for the action of enzymes. (ii) Chemical digestion Involves enzymatic reactions which digest the food into simpler chemical forms. Hydrolysis splits the large molecules by addition of water.

How is Food Digested? Mouth Ingestion is the process of taking food into the body. The tongue rolls and lubricates food with mucus and saliva. Chemical digestion of starch starts here by salivary amylase. Oesophagus It takes food down from the throat and into the stomach. Moving food by waves of muscle contraction called peristalsis.

The oesophagus The partially digested food is pushed to the stomach by wave-like contractions known as peristalsis. Circular muscles contract to push the food ball down. Circular muscles relax, and the tube widens for food to move.

The stomach Stomach The stomach lining produces mucus and gastric juices which contains: i) hydrochloric acid (acidic medium of pH 2 for enzymes and kills micro-organisms in food) ii) Pepsin: hydrolyze protein to polypeptides. iii) Rennin: hydrolyze milk caseinogen to casein. stomach

Quick Revision: What is the function of hydrochloric acid? 1) Provides an acidic medium for activation of gastric enzymes. Inactive forms Prorennin HCl Rennin Pepsinogen HCl Pepsin 2) Kills germs and potential parasites. 3) Stop the action of salivary amylase. Active forms

Case Study 1 You should: take multiple small meal at regular intervals, take less protein per meal clean and cook the food thoroughly…… Dr. Jones, I am suffering from stomach cancer & half of my stomach was removed. What should I do?

Case Study 2 Oh dear….i feel that my chest is burning after having a heavy dinner. What could have gone wrong?

Inflamed oesophagus This condition is due to the irritation of the oesophagus that is caused by too much stomach acid.

The Liver & Gall Bladder A small pear-shaped organ that is greenish-yellow in colour. Temporarily stores bile secreted by liver. QUESTION: Will bile secretion be hindered if the gall bladder is removed?

Liver and Gall Bladder Pancreas Small intestines Large Intestines THE STRUCTURE & FUNCTIONS OF … Liver and Gall Bladder Pancreas Small intestines Large Intestines Rectum and Anus

Largest gland in the body. LIVER: Largest gland in the body. Lies below diaphragm, on right side of body. Secretes bile. QUESTION: Can bile digest food? Bile is not an enzyme, so it cannot digest food but it aids in digestion of lipids.

Emulsification Bile Large oil drop Small oil droplets

The Pancreas Connected to duodenum by pancreatic duct Secretes pancreatic juice that contains digestive enzymes.

Small Intestines (Duodenum, jejunum and ileum) Major site of chemical digestion of all remaining food (carbohydrates, fats and proteins). Also, main site of absorption of nutrients occur here.

The Large Intestine Contains undigested food material. Main function is to absorb water and mineral salts. Rectum temporarily stores faeces that are egested through the anus.