Question

5. What are rugae? Where are thy located? 6. What type of waste does the digestive tract dispose of? 7. What type of wastes does the excretory system dispose of? 8. What is the functional unit of a kidney? 9. Where are wastes stored before elimination from the body? 10. What is the primary type of nitrogenous waste made by mammals? On

Answer 1

1. Mechanical breakdown or digestion of food occurs in several parts of the alimentary canal.

• Mechanical digestion in mouth occurs from the chewing of food, also called as mastication. This is performed by the grinding, tearing and cutting action of teeth. The masticated food mixes with saliva in the mouth.
• Mechanical digestion in stomach occurs due to the peristaltic movements (mixing waves). These movements cause the mixing of food with the chemical secretions by the gastric glands of the stomach. As a result of the mechanical breakdown in stomach, a liquid is formed which is known as chyme.
• Mechanical digestion in the small intestine occurs due to peristaltic movements (segmentations) and migrating motility complexes. Segmentations are contractions that cause mixing of the chyme with enzymes and also aids in absorption of the digested food. Migrating motility complexes begin in the pyloric region of the stomach and pushes the chyme forward.
• Mechanical digestion in the large intestine occurs due to a gastroileal reflex that forces the chyme into the cecum. The repeated distension and squeezing of the haustra of large intestine cause the contents to pass from one haustra to another. This movement is called haustral churning. A mass peristaltic movement occurs that finally pushes the contents into the rectum for egestion.