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THE DIGESTIVE SYSTEM
The digestive tract & other organs that aid in the body’s digestion & absorption of food make up the digestive system. It is a protracted, twisted tile that originates at the mouth & esophagus & travel via stomach,small & large intestines and the anus. The digestive system breaks down food into nutrients like proteins,lipids & carbohydrates.The body can utilise them for energy ,growth, & repair after these nutrients are absorbed into the bloodstream. Unused materials are discarded as excrement. The gallbladder,liver, & pancreas are further digestive system organs.
- Fig 1: Digestive system Function:-
- Ingest food
- Breakdown food into nutrient molecules
- Absorb molecules into the bloodstream
- Rid the body of indigestible remains
Mechanism of digestion:- Mouth :- The teeth break down food into tiny pieces when you eat. Saliva is produced by glands in the cheeks and under the tongue. Saliva coats the food and facilitates chewing and swallowing. Enzymes further break down the carbohydrates in food and are also present in saliva. Esophagus :- The muscular tube known as the esophagus transports food from the mouth to the stomach after swallowing it. To allow food to enter the stomach, a muscle ring at the end of the oesophagus relaxes and tightens to stop stomach contents from returning to the oesophagus. Stomach :- Proteins are digested by the gastric juice, which is made by the stomach wall and contains hydrochloric acid and enzymes. The stomach works like a concrete mixer to create a thick, soupy liquid called chyme by churning and combining food and gastric juice. Small intestine :- When digestive fluids from the pancreas and bile from the gallbladder empty into the upper portion of the small intestine, they break down fat and protein into amino acids and fatty acids, respectively. Along with sugars, vitamins, and minerals, these tiny particles are absorbed into circulation through the small intestine’s membrane. Although it has a 3.5cm diameter, it is around 5m long to provide a large surface area for absorption. Proteins, carbohydrates and lipids (fats) are generally digested in the small intestine. Large intestine & anus :- The lining of the large intestine absorbs water, salts from minerals and vitamins. Undigested fibre is combined with mucus and bacteria, which partially breaks down the fibre, to sustain the large intestine wall cells and maintain health. Before leaving the body through the anus, faeces are produced and stored in the rectum, the final section of the large intestine. Mouth :-
- Oral cavity or buccal cavity : Lining : thick stratified squamous epithelium
- It is formed by Cheeks Hard palate Soft palates Tongue
Fungiform papillae :- These papillae get their name from their mushroom like shape. Located mostly on the sides and tip of the tongue. Fungiform papillae consist of approximately 1,600 taste buds. Foliate :- Located on each side of the back portions of the tongue. The foliate papillae look like rough folds on tissue. Each person has about 20 foliate papillae,which contain several hundred taste buds Fig 2 : papillae of tongue How do taste buds work :- Taste buds are clusters of nerve cells that transmit sensory messages to brain. There are five basic tastes that stimulate the taste buds, including :
- Sweet
- Salty
- Bitter
- Sour
- Savory
