Human Nutrition
Short Questions
1. What is nutrition?
Answer: Nutrition is the process by which organisms consume and utilize food to meet dietary needs, including energy, growth, and tissue repair.
2. What is the role of salivary amylase?
Answer: Salivary amylase breaks down starch into maltose in the mouth.
3. Why is human dentition called thecodont?
Answer: Each tooth is fixed in a socket in the jawbone by a gomphosis joint.
4. What is the function of the epiglottis?
Answer: The epiglottis prevents food from entering the trachea during swallowing.
5. What is peristalsis?
Answer: Peristalsis is the rhythmic contraction of muscles that propels food through the alimentary canal.
6. What is the role of bile salts?
Answer: Bile salts emulsify fats and neutralize chyme acidity in the small intestine.
7. What is chyme?
Answer: Chyme is the semifluid, acidic mass of partially digested food formed in the stomach.
8. What are villi in the small intestine?
Answer: Villi are finger-like projections that increase the surface area for nutrient absorption.
9. What is the function of Kupffer cells in the liver?
Answer: Kupffer cells phagocytose toxic substances, dead cells, and microorganisms in the liver.
10. What is the dental formula of an adult human?
Answer: The dental formula is ( \frac{2,1,2,3}{2,1,2,3} ), representing 32 teeth.
11. What is the role of the pyloric sphincter?
Answer: The pyloric sphincter regulates the flow of chyme from the stomach to the duodenum.
12. What is egestion?
Answer: Egestion is the expulsion of undigested waste (faeces) through the anus.
13. What causes Kwashiorkor?
Answer: Kwashiorkor is caused by protein deficiency in children aged 1-3 years.
14. What is the function of mucus in the stomach?
Answer: Mucus protects the stomach lining from damage by HCl and pepsin.
15. What is the role of secretin hormone?
Answer: Secretin inhibits gastric juice secretion and stimulates bile and pancreatic juice release.
Long Questions
1. Explain the structure of a tooth.
Answer: A tooth consists of a crown (visible, enamel-covered), a root (embedded, cementum-covered), and a neck (junction). The dentin forms the bulk, enclosing the pulp cavity with nerves and blood vessels, and the root canal extends into the root. Enamel is the hardest substance, protecting the tooth, while cementum anchors it to the gum socket.
2. Why is human dentition described as diphyodont and heterodont?
Answer: Human dentition is diphyodont because it includes two sets of teeth: milk (deciduous) and permanent. It is heterodont due to four types of teeth—incisors, canines, premolars, and molars—each with distinct shapes and functions. This allows humans to perform varied tasks like cutting, tearing, and grinding food.
3. Describe the role of the pancreas in digestion.
Answer: The pancreas, a heterocrine gland, has exocrine acinar cells that secrete pancreatic juice containing amylase, lipase, and trypsinogen for digesting carbohydrates, fats, and proteins. Its endocrine islets of Langerhans release insulin, glucagon, and somatostatin to regulate blood sugar. Pancreatic juice is delivered to the duodenum via the pancreatic duct.
4. How does bile juice contribute to digestion?
Answer: Bile juice, secreted by the liver, contains bile salts that emulsify fats, increasing their surface area for lipase action. It neutralizes acidic chyme, creating an alkaline environment for enzymatic activity in the small intestine. Bile pigments (bilirubin, biliverdin) impart color to faeces.
5. What is the significance of villi in the small intestine?
Answer: Villi are finger-like projections in the small intestine that increase the surface area for nutrient absorption. They contain capillaries for absorbing glucose, amino acids, and water-soluble vitamins, and lacteals for lipids and fat-soluble vitamins. Villi enhance the efficiency of nutrient transport into the bloodstream and lymph.
6. Explain the process of protein digestion in the stomach.
Answer: In the stomach, pepsinogen is activated to pepsin by HCl, which provides an acidic medium (pH 1.8). Pepsin breaks down proteins into peptones and proteoses, while mucus protects the stomach lining from acid damage. In infants, rennin curdles milk proteins for further digestion by pepsin.
7. What are the causes and symptoms of marasmus?
Answer: Marasmus is caused by prolonged protein and calorie deficiency in infants under one year, often due to poverty or early weaning. Symptoms include loss of subcutaneous fat, prominent ribs, thin limbs, dry/wrinkled skin, and weight loss. Digestion and absorption stop due to atrophy of digestive glands, without oedema.
8. How is digestion regulated by hormones?
Answer: Hormones like gastrin stimulate gastric juice secretion, while secretin and cholecystokinin (CCK) inhibit it and promote bile and pancreatic juice release. Gastric inhibiting peptide (GIP) also reduces gastric secretion, and CCK induces satiety. These hormones ensure digestive juices are secreted at the right time and place.
9. Describe the histological structure of the alimentary canal.
Answer: The alimentary canal has four layers: mucosa (innermost, with goblet cells and glands), submucosa (connective tissue with vessels), muscularis (smooth muscles for movement), and serosa (outermost, epithelial layer). The mucosa forms villi in the small intestine and rugae in the stomach. These layers vary by organ to support specific digestive functions.
10. What is jaundice, and how does it develop?
Answer: Jaundice is characterized by yellowing of the skin and conjunctiva due to abnormal bilirubin metabolism. It develops from excessive red blood cell breakdown, high bilirubin levels overwhelming the liver, or bile flow obstruction. Supportive care and rest are provided, as there is no specific treatment.
Leave a Reply