Unit 1: Human Digestive System — Short Questions

Ans. (i) In oral cavity, partial chemical digestion of carbohydrates is done by three pairs of salivary glands.
(ii) These glands are attached with oral cavity and secrete saliva - a mixture of water, mucus, and a digestive enzyme called salivary amylase.
(iii) Water and mucous moisten the food pieces.
(iv) Salivary amylase breaks down the starch present in food into maltose.

Ans. After the physical and partial chemical digestion, the food mass in oral cavity is called bolus.
(a) Swallowing
(i) Food (bolus) is swallowed by pushing it into the pharynx.
(ii) For swallowing, the tongue moves the bolus to the back of the oral cavity. The swallowed food enters the pharynx.
(iii) During swallowing, the palate (roof of oral cavity) moves upward to close the opening of the nasal cavity.
(b) Peristalsis
When food enters oesophagus, successive waves of contraction are generated in its muscular walls. These waves of contractions move food along the oesophagus to the stomach. These waves of muscular contraction are called peristalsis.

Ans. (i) HCl in gastric juice converts pepsinogen into an active enzyme pepsin. Pepsin breaks large proteins into shorter chains of amino acids called peptides.
(ii) Hydrochloric acid also kills pathogenic bacteria present in food.

Ans. Secretion of pancreas i.e., pancreatic juice enters duodenum through pancreatic duct, which joins the common bile duct before entering duodenum.
(i) Pancreatic juice contains many enzymes e.g., trypsin, pancreatic amylase and lipase.
(ii) These enzymes digest proteins, carbohydrates and lipids respectively.
(iii) Pancreatic juice also contains sodium bicarbonate that neutralizes the acidity of chyme.

Ans. The inner walls of small intestine are highly folded. Moreover, these folds have millions of finger-like projections called villi (singular: villus). Villi increase the surface area for absorption of food.

Ans.
(a) Introduction: Peptic ulcers are sores that develop in the walls of alimentary canal.
(b) Types of Ulcers
(i) Ulcer usually develops in the walls of stomach and is called gastric ulcer
(ii) However, ulcers may also develop in duodenum (duodenal ulcer).
(iii) The ulcer of oesophagus is called oesophageal ulcer
(c) Signs and Symptoms: Burning stomach pain, rush of saliva after regurgitation, loss of appetite, weight loss, blood vomiting (in severe cases).
(d) Causes: Infection due to Helicobacter pylori bacteria, long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs), excessive alcohol consumption, smoking, stress (though not a direct cause, it can make symptoms worse).
(e) Treatment: Antibiotics to clear H. pylori infection, other medicines called antacids and proton pump inhibitors are also used to cure ulcer
Prevention: Avoiding excessive use of painkillers (NSAIDs), avoiding spicy foods, eating a balanced diet.

Ans. Nutrition is how organisms get and use nutrients. It helps them to grow, stay healthy and repair

Ans.
Digestion: i. Breaking food into smaller parts the body can absorb.
ii. This process happens inside our digestive system (oral cavity, stomach, and small intestine)

Absorption i. Moving nutrients from the digested food into the blood or lymph.
ii. This takes place through villi (small intestine).

Ans. If pancreatic juice is not secreted by pancreas into the small intestine no completion of digestion of food take place.

Ans. Pepsin is an enzyme that functions optimally in the acidic environment of the stomach. When it reaches the small intestine, the alkaline pH (created by the pancreas) and bicarbonate secretion inactivates pepsin. Protein digestion in the small intestine is then taken over by other enzymes such as pancreatic enzymes.

Ans. The gall bladder stores and concentrates bile from the liver, and then releases it into the duodenum in the small intestine to help in digestion of fats.

Ans. Gastric mucus is a gel-mucous barrier secreted by epithelial cells and glandular cells in the stomach wall. It acts as part of a barrier that protects the stomach wall from the acid and digestive enzymes within the stomach lumen.

Ans.
Name of enzyme | Substrate | Product
Protease | Protein | Amino acids
Amylase | Starch | Maltose and Glucose
Lipase | Lipids/fats | Fatty acids and glycerol

Ans.
Mechanical digestion:
(i) Mechanical digestion breaks down food physically into smaller pieces.
(ii) Enzymes are not involved.
(iii) Examples: Chewing, stomach churning

Chemical digestion (i) Chemical digestion uses enzymes to breakdown food molecules into smaller, absorbable molecules.
(ii) Examples: Amylase (Oral cavity and intestine)

Ans.
Bolus:
(i) After the process of chewing, lubrication and partial digestion, the pieces of bread and mutton are rolled up by tongue into small, slippery, spherical mass called bolus.
(ii) It is alkaline.
(iii) It is formed in oral cavity.
(iv) It is formed by tongue and grinding action of teeth.

Chyme (i) Semi-solid mass of partly digested food by gastric secretions and which passes from stomach into small intestine.
(ii) It is acidic.
(iii) It is formed in stomach.
(iv) It is formed by churning and gastric secretions.

Ans. Stomach has two sphincters (openings which are guarded by muscles). The cardiac sphincter is between stomach and oesophagus.

Ans. Large intestine has 3 parts, caecum, colon and rectum. Colon is the second part of it. from colon water, electrolyte and vitamins are absorbed into the blood.

Ans. Duodenum is part of small intestine and is about 20-25cm long. Bile duct from gall bladder, hepatic duct from liver and pancreatic duct from pancreas empties its secretions, in the duodenum.

Ans. Saliva contains an enzyme salivary amylase, which aids in the partial digestion of starch.

Ans. When food enters stomach, the gastric gland found in the stomach wall are stimulated to secrete gastric juice. It is composed chiefly of mucous, HCl and a protein digesting enzyme pepsinogen.

Ans.
Diarrhea:
Diarrhoea is characterized by frequent, loose, or watery stools. Diarrhoea can lead to dehydration, especially in children and the adults.

Signs and Symptoms

• Frequent, loose, or watery stools
• Abdominal cramps or pain
• Bloating
• Dehydration (thirst, dry mouth, dark urine).

Causes Infections (bacterial, viral, or parasitic), food allergies, stress, certain medications (e.g., antibiotics).

Constipation Constipation is a condition in which faeces are not eliminated from the body at regular intervals.

Signs and Symptoms

• Infrequent or difficult bowel movements (less than 3 times a week)
• Hard and dry stools
• Abdominal discomfort
• Bloating

Causes Lack of fibre in diet, dehydration, lack of physical activity, certain medicines (e.g., painkillers, iron supplements), other diseases (e.g., diabetes).

Ans.
(a) Introduction: Peptic ulcers are sores that develop in the walls of alimentary canal.
(b) Types of Ulcers
(i) Ulcer usually develops in the walls of stomach and is called gastric ulcer
(ii) However, ulcers may also develop in duodenum (duodenal ulcer).
(iii) The ulcer of oesophagus is called oesophageal ulcer
(c) Signs and Symptoms: Burning stomach pain, rush of saliva after regurgitation, loss of appetite, weight loss, blood vomiting (in severe cases).
(d) Causes: Infection due to Helicobacter pylori bacteria, long-term use of nonsteroidal anti-inflammatory drugs (NSAIDs), excessive alcohol consumption, smoking, stress (though not a direct cause, it can make symptoms worse).

Ans. Someone with liver disease has trouble in digesting fats primarily because the damaged liver cannot produce or secrete sufficient bile which is essential for breaking down dietary fats in the intestine.

Ans. Maintaining a healthy gut bacteria balance is crucial because:

• These microbes aid digestion, produce essential vitamins, train immune system, fight Pathogens.
• They influence mood and mental health by producing neurotransmitters.
• An imbalance can trigger inflammation leading to digestive issues, allergies and systemic health problems.

Ans. A malfunction in the cardiac sphincter can lead to acid reflux because the sphincter in the muscle that acts as a valve between the oesophagus and the stomach. When it malfunctions, stomach contents including acid can flow backward into the oesophagus.

Ans. Bile is stored and concentrated in the gallbladder before release to ensure it is potent enough to effectively digest fats.