Chapter 1: Digestive System

Select the correct answer:

1. Emulsification of fat will not occur in the absence of:

A) lipase

B) bile pigment

C) pancreatic juice

D) gastric juice

Answer: B) bile pigment (Note: More accurately, bile salts perform emulsification, but among the options, bile pigment represents bile.)

Explanation: Bile salts (found in bile) emulsify fats, breaking them into smaller droplets to increase the surface area for lipase action.

2. The enzyme, substrate and pH conditions are needed for the digestion of food in the stomach?

D Protease Protein High

Answer: C (Protease enzyme, Protein substrate, Low pH)

Explanation: The stomach secretes pepsin (a protease) which digests proteins. It works optimally at a low pH (around 2) due to hydrochloric acid.

3. Bile is formed in:

A) liver

B) gall bladder

C) pancreas

D) duodenum

Answer: A) liver

Explanation: Bile is produced by the liver and stored in the gall bladder.

4. Glycogen is stored in:

A) gall bladder

B) spleen

C) liver

D) pancreas

Answer: C) liver

Explanation: Glycogen is stored in the liver (and muscles) and is broken down into glucose when needed.

5. Common passage for swallowing food and breathing is:

A) pharynx

B) larynx

C) esophagus

D) mouth

Answer: A) pharynx

Explanation: The pharynx (throat) is a common passage for both food and air.

6. Most of the digestion of starch and protein is carried out by:

A) gastric juice

B) pancreatic juice

C) intestinal juice

D) bile

Answer: B) pancreatic juice

Explanation: Pancreatic juice contains amylase, protease, and lipase, which complete the digestion of starch, proteins, and fats in the small intestine.

7. If the mucous lining covering the stomach breaks down and stomach tissues are damaged by:

A) diarrhea

B) dysentery

C) ulcer

D) colon

Answer: C) ulcer

Explanation: A peptic ulcer occurs when the protective mucous lining of the stomach or duodenum is damaged, allowing digestive juices to irritate the underlying tissue.

8. Part of the digestive system, which is not in contact with food, is:

A) small intestine

B) liver

C) caecum

D) stomach

Answer: B) liver

Explanation: The liver produces bile but does not come into direct contact with food. It is an accessory organ.

9. The diet component which prevent constipation is:

A) fibre

B) protein

C) minerals

D) vitamin

Answer: A) fibre

Explanation: Dietary fiber (roughage) adds bulk to the stool and helps prevent constipation.

10. Fats are broken down by:

A) lymph vessel

B) villi

C) blood capillaries

D) hepatic portal vein

Answer: A) lymph vessel (Note: Fats are absorbed into lacteals, which are lymph vessels in the villi.)

Explanation: Fatty acids and glycerol are absorbed into the lacteals (lymph vessels) in the villi and then enter the lymphatic system.

11. Which secretion, released into the alimentary canal, contains no enzymes but speeds up fat digestion?

A) bile

B) pancreatic juice

C) saliva

D) gastric juice

Answer: A) bile

Explanation: Bile contains no digestive enzymes but emulsifies fats, increasing the surface area for lipase to act.

12. Enzyme trypsinogen is changed to trypsin by:

A) gastrin

B) enterokinase

C) secretin

D) hydrochloric acid

Answer: B) enterokinase

Explanation: Enterokinase, secreted by the duodenal mucosa, converts inactive trypsinogen to active trypsin.

13. How does food move through your digestive tract?

A) by gravity

B) by wavelike muscle contractions

C) by cilia

D) by chemical absorption

Answer: B) by wavelike muscle contractions

Explanation: Peristalsis is a series of wave-like muscle contractions that move food through the digestive tract.

14. Where the majority of the water from the indigestible food is absorbed?

A) small intestine

B) large intestine

C) stomach

D) pancreas

Answer: B) large intestine

Explanation: The large intestine absorbs water and electrolytes from the remaining indigestible food matter, forming feces.

1. Write the functions of the following parts of alimentary canal: mouth, pharynx, esophagus, stomach, small intestine, villi, bile, gall bladder, pancreas

Answer:

Mouth: Ingests food, chews (mechanical digestion), and begins starch digestion via salivary amylase. Forms bolus. Pharynx: Common passage for food and air; initiates swallowing reflex.

Esophagus: Transports food from pharynx to stomach via peristalsis. Stomach: Stores food, churns it with gastric juices (HCl, pepsin) to form chyme; begins protein digestion. Small Intestine: Primary site for chemical digestion and absorption of nutrients. Composed of duodenum, jejunum, and ileum. Villi: Finger-like projections in the small intestine that increase surface area for absorption. Bile: Emulsifies fats, neutralizes chyme, and aids in absorption of fat-soluble vitamins. Produced by liver. Gall Bladder: Stores and concentrates bile; releases it into the duodenum. Pancreas: Produces pancreatic juice containing enzymes (amylase, lipase, proteases) and bicarbonate to neutralize chyme.

2. Draw and label longitudinal section of villus.

Answer: (Diagram Description)

A finger-like projection from the intestinal wall. Labels: Epithelium (with microvilli), Lacteal (lymph vessel), Blood capillaries, Nerve, Artery, Vein. Function: The structure increases surface area for absorption of nutrients into blood (glucose, amino acids) and lacteals (fats).

3. Why is pepsin formed in inactive form pepsinogen?

Answer: Pepsin is formed as inactive pepsinogen to prevent it from digesting the proteins of the stomach cells themselves. If pepsin were produced in its active form, it would break down the cellular proteins of the stomach lining, causing damage and ulcers. Pepsinogen is activated to pepsin only when it comes into contact with hydrochloric acid in the stomach lumen, where it is needed for digestion.

4. Why must digested food be distributed by blood in man and other animals?

Answer: Digested food must be distributed by blood because:

Transport: Nutrients (glucose, amino acids, vitamins, minerals) are absorbed into the blood and transported to all cells of the body. Energy: Cells need nutrients for cellular respiration to produce ATP. Growth and Repair: Cells need nutrients for building new tissues and repairing damaged ones. Storage: Excess nutrients are transported to the liver and fat cells for storage. Blood acts as the transport medium to ensure all cells receive essential nutrients.

5. What would happen if pancreatic juice did not reach your small intestine?

Answer: If pancreatic juice did not reach the small intestine:

Incomplete Digestion: Carbohydrates, proteins, and fats would not be fully digested. Amylase, proteases, and lipase from the pancreas would be missing. Malabsorption: Nutrients would not be absorbed properly, leading to malnutrition. Acidic Chyme: Without bicarbonate from pancreatic juice, the acidic chyme from the stomach would not be neutralized, damaging the intestinal lining. Health Issues: This condition (e.g., blocked pancreatic duct) can lead to severe digestive problems and weight loss.

6. Why oxygen is needed to perform this process (respiration) in our small intestine?

Answer: Oxygen is needed in the small intestine for cellular respiration to produce ATP. The cells of the small intestine are highly active, constantly absorbing nutrients, synthesizing enzymes, and maintaining ion gradients (e.g., sodium-potassium pumps). This requires a significant amount of energy (ATP). Aerobic respiration, which requires oxygen, is the most efficient way to produce ATP.

Without oxygen, these cells would not have enough energy to function, and nutrient absorption would be impaired.

7. What body system will the small intestine come in contact with?

Answer: The small intestine comes in contact with several body systems:

Digestive System: It is a part of it. Circulatory System: Nutrients are absorbed into blood capillaries. Lymphatic System: Fats are absorbed into lacteals (lymph vessels). Nervous System: Regulates intestinal motility and secretion. Endocrine System: Hormones like secretin and CCK regulate its function.

8. Some cells of the stomach secrete mucus to protect from stomach wall. Suggest what will happen if the stomach does not produce such a secretion?

Answer: If the stomach did not produce mucus:

Ulcers: The hydrochloric acid and pepsin in the stomach would digest the stomach's own lining, causing peptic ulcers. Pain and Bleeding: This would lead to severe pain, bleeding, and potentially perforation of the stomach wall. Inflammation: Gastritis (inflammation of the stomach lining) would occur. Digestive Issues: Digestion would be impaired, and the stomach could be severely damaged.

9. Following table shows the names of three enzymes found in alimentary canal. Complete the table by writing names of substrate and product for each enzyme.

Answer:

12. Write the function of each type of teeth.

Answer:

Incisors: Front teeth, sharp, for cutting and biting food. Canines: Pointed teeth, for tearing food. Premolars: Flat teeth, for crushing and grinding food. Molars: Large flat teeth, for crushing and grinding food.

13. Describe digestion in oral cavity.

Answer: Digestion in the oral cavity (mouth) involves both mechanical and chemical processes:

Mechanical Digestion: Teeth chew and grind food into smaller pieces, increasing surface area. The tongue mixes food with saliva and forms a bolus. Chemical Digestion: Salivary glands secrete saliva containing the enzyme salivary amylase. Amylase begins the breakdown of starch into maltose. Saliva also contains mucus, which lubricates food for easy swallowing, and lysozyme, which kills bacteria. Result: The food is formed into a bolus and swallowed.

14. Differentiate between mechanical and chemical digestion.

Answer:

1. Describe the structures of alimentary canal and its associated organs.

Answer: The human digestive system consists of the alimentary canal (a continuous tube) and associated glands.

Alimentary Canal:

1. Mouth (Oral Cavity): Contains teeth, tongue, and salivary glands. It is the site of ingestion, mechanical digestion (chewing), and initial chemical digestion (starch).

2. Pharynx (Throat): A muscular tube that connects the mouth to the esophagus. It serves as a common passage for food and air.

3. Esophagus (Food Pipe): A muscular tube that transports food from the pharynx to the stomach via peristalsis.

4. Stomach: A J-shaped muscular organ. It stores food, mixes it with gastric juices (HCl, pepsin, mucus), and begins protein digestion. It forms chyme.

5. Small Intestine: A long, coiled tube (6-7 meters) divided into duodenum, jejunum, and ileum. It is the primary site for chemical digestion and absorption of nutrients. It contains villi and microvilli.

6. Large Intestine: About 1.5 meters long, divided into caecum, colon, and rectum. It absorbs water and electrolytes, forms feces, and houses beneficial bacteria.

7. Anus: The external opening through which feces is expelled.

Associated Organs (Accessory Glands):

1. Salivary Glands: Secrete saliva containing amylase, mucus, and lysozyme.

2. Liver: Produces bile, stores glycogen, and detoxifies blood.

3. Gall Bladder: Stores and concentrates bile.

4. Pancreas: Produces pancreatic juice containing amylase, lipase, proteases, and bicarbonate.

In summary, the alimentary canal and associated organs work together to digest food, absorb nutrients, and eliminate waste.

2. Describe the process of swallowing of food in man.

Answer: Swallowing (deglutition) is a complex process involving both voluntary and involuntary actions.

1. Oral Phase (Voluntary):

Food is chewed and mixed with saliva to form a bolus. The tongue pushes the bolus to the back of the mouth (pharynx).

2. Pharyngeal Phase (Involuntary):

The bolus enters the pharynx. The soft palate rises to close off the nasopharynx, preventing food from entering the nasal cavity. The epiglottis folds down to cover the larynx, preventing food from entering the trachea (windpipe). The upper esophageal sphincter relaxes.

3. Esophageal Phase (Involuntary):

The bolus enters the esophagus. Peristalsis (wave-like muscle contractions) pushes the bolus down the esophagus. The lower esophageal sphincter (cardiac sphincter) relaxes, allowing food to enter the stomach.

In summary, swallowing involves coordinated muscle movements to safely transport food from the mouth to the stomach.

3. Explain the process of ingestion of food in man.

Answer: Ingestion is the process of taking food into the body through the mouth. It is the first step in digestion.

Steps:

1. Selection of Food: The individual selects food based on hunger, taste, and availability.

2. Entry into Mouth: Food enters the oral cavity.

3. Mechanical Breakdown: Teeth chew and grind food into smaller pieces (mastication).

4. Mixing with Saliva: The tongue mixes food with saliva secreted by salivary glands.

5. Bolus Formation: Food is formed into a soft, moist mass called a bolus.

6. Swallowing: The tongue pushes the bolus to the pharynx to initiate swallowing.

In summary, ingestion involves taking food into the mouth, chewing it, mixing it with saliva, and forming a bolus for swallowing.

4. Explain the process of digestion in stomach.

Answer: Digestion in the stomach involves both mechanical and chemical processes.

1. Mechanical Digestion:

The stomach's muscular walls contract (churning) to mix food with gastric juices. This breaks food into smaller particles and forms chyme.

2. Chemical Digestion:

Hydrochloric Acid (HCl): Denatures proteins, kills bacteria, and activates pepsinogen to pepsin. Pepsin: Breaks down proteins into peptides. Gastric Lipase: Begins the digestion of fats (minor role). Mucus: Protects the stomach lining from acid and enzymes.

3. Regulation:

Gastrin (hormone) stimulates gastric secretion. The vagus nerve stimulates motility and secretion.

In summary, the stomach mechanically churns food and chemically digests proteins, forming chyme that is slowly released into the small intestine.

5. Draw the structure of small intestine in longitudinal section.

Answer: (Diagram Description)

A long, coiled tube with a folded inner lining. Labels: Lumen, Villi, Epithelium, Lacteal, Blood Capillaries, Submucosa, Muscularis. Function: The structure increases surface area for absorption.

6. Draw and describe the structure of villus.

Answer: (Diagram Description)

A finger-like projection from the intestinal wall. Labels: Epithelium (with microvilli), Lacteal (lymph vessel), Blood capillaries, Nerve, Artery, Vein.

Structure:

Epithelium: Single layer of cells with microvilli, increasing surface area. Lacteal: A central lymph vessel for fat absorption. Blood Capillaries: Network for absorbing glucose and amino acids.

Function: The villus increases surface area for efficient absorption of nutrients.

7. State the role of liver.

Answer: The liver performs numerous vital functions:

Bile Production: Produces bile for fat emulsification. Metabolism: Regulates carbohydrate, protein, and lipid metabolism. Storage: Stores glycogen, vitamins (A, D, B12), and minerals (iron). Detoxification: Removes toxins, drugs, and alcohol from the blood. Protein Synthesis: Synthesizes plasma proteins (albumin, fibrinogen). Excretion: Excretes bile pigments and cholesterol. Immune Function: Contains Kupffer cells that destroy old RBCs and pathogens.

8. State the causes, treatment and prevention of the following disorder of the digestive system.

a. diarrhea

Answer:

Causes: Viral/bacterial infections, contaminated food/water, food intolerance, medications. Treatment: Oral rehydration solution (ORS), rest, bland diet, antibiotics (if bacterial). Prevention: Good hygiene, safe drinking water, proper food handling.

b. constipation

Answer: Causes: Low fiber diet, dehydration, lack of exercise, certain medications. Treatment: Increase fiber and water intake, exercise, laxatives (if needed). Prevention: High-fiber diet, adequate hydration, regular physical activity.

c. ulcer

Answer: Causes: H. pylori infection, long-term NSAID use, excess acid production. Treatment: Antibiotics (for H. pylori), acid reducers (PPIs), antacids, avoiding irritants. Prevention: Avoid NSAIDs, manage stress, treat H. pylori infection.