Human Digestion and Respiration Processes
Digestive Process
Enzymes are unseen substances produced by the body that mix with food. In the digestive tract, a series of chemical reactions take place, called chemical digestion.
Mastication: Mechanical process of crushing food into smaller pieces.
Tongue: Involved in moving food to other teeth.
Salivation: When we put food in our mouth, salivary glands produce saliva, a liquid that mixes with food to form the food bolus. Saliva has three functions:
- Starts the chemical digestion of carbohydrates (starch) with salivary amylase (ptyalin).
- Destroys bacteria in food (bactericidal function).
- Facilitates the passage of the bolus into the pharynx and esophagus.
Swallowing: The bolus passes through the pharynx and esophagus thanks to the tongue. Peristaltic movements (contractions of muscle layers) propel the bolus.
Stomach: The bolus enters the stomach, mixing with gastric juice (containing pepsin and hydrochloric acid) for 3-4 hours, forming chyme.
Small Intestine: Chyme enters the small intestine (duodenum), mixing with digestive secretions from the liver, pancreas, and intestinal glands. Peristaltic movements continue.
Vomiting: Expulsion of chyme from the stomach through the esophagus and pharynx.
Liver: Secretes bile (containing bile salts) into the duodenum, emulsifying fats and destroying toxic molecules.
Pancreas: Secretes pancreatic juice (containing enzymes for digesting fats, carbohydrates, and proteins) and bicarbonate (neutralizing chyme acidity) into the duodenum.
Digestion Summary: Food (saliva) → Food bolus (gastric juices) → Chyme (pancreatic juice, bile) → Chyle (water absorption) → Feces.
- Carbohydrates: Broken down by amylase from saliva.
- Lipids: Broken down into fatty acids and glycerin in the small intestine.
- Proteins: Broken down into amino acids in the stomach and small intestine.
- Vitamins and minerals: Absorbed in the small intestine.
- Water: Absorbed.
- Fiber and fat: Not digested.
Respiratory Process
In addition to nutrients, cells need oxygen for cellular respiration. The respiratory system captures oxygen from the air and transports it to body cells via blood, expelling carbon dioxide.
Gas exchange occurs by diffusion, from areas of higher concentration to lower concentration. Oxygen passes from the alveoli into the blood, while carbon dioxide passes from the blood into the alveoli.
Pulmonary Ventilation: Continuous renewal of air in the alveoli for effective gas exchange.
Inhale: Air enters the lungs due to muscle contractions in the ribcage and diaphragm, increasing thorax capacity.
Exhale: Air moves out of the lungs as the ribcage and diaphragm relax, decreasing thorax volume and forcing the lungs to contract.