RBSE Solutions Class 12 Biology Chapter 22 Man-Digestive System

RBSE Class 12 Biology Chapter 22 Multiple Choice Questions

 

Question 1. Which part secretes renin?
(a) Liver
(b) Colon
(c) Stomach
(d) Rectum
Answer: (c) Stomach
In simple words: Renin is an enzyme, and it is released by the stomach. It helps in the digestion process.

🎯 Exam Tip: Remember key enzymes and the organs that produce them, as this is a common topic in digestive system questions.

 

Question 2. Pancreatic juice is -
(a) Acidic
(b) Alkaline
(c) Neutral
Answer: (b) Alkaline
In simple words: Pancreatic juice is not acidic or neutral; it is alkaline, which means it helps to neutralize the stomach acid.

🎯 Exam Tip: Know the pH nature (acidic, alkaline, neutral) of different digestive juices and why they are important for digestion.

 

Question 3. Kupffer's cells are found in -
(a) Pancreas
(b) Small intestine
(c) Large intestine
(d) Liver
Answer: (d) Liver
In simple words: Kupffer's cells are special cells that clean the blood in the liver by eating up old cells and harmful things.

🎯 Exam Tip: Associate specific cell types with their respective organs and primary functions in the body.

 

Question 4. Amylase enzyme acts on which substrate -
(a) Protein
(b) Carbohydrate
(c) Fatty acid
(d) Fat
Answer: (b) Carbohydrate
In simple words: The amylase enzyme helps to break down carbohydrates, like starches, into simpler sugars.

🎯 Exam Tip: Match each enzyme to its specific substrate (what it acts upon) and the type of molecule it digests.

 

Question 5. Which converts inactive pepsinogen into active pepsin -
(a) Ptyalin
(b) HCL
(c) Bile
(d) Renin
Answer: (b) HCL
In simple words: Hydrochloric acid (HCL) in the stomach changes pepsinogen, which is inactive, into active pepsin to help digest proteins.

🎯 Exam Tip: Understand how zymogens (inactive enzymes) are activated, often by an acid or another enzyme, to begin their function.

 

Question 6. How many salivary glands are found in a man?
(a) 5 pairs
(b) 2 pairs
(c) 4 pairs
(d) 3 pairs
Answer: (d) 3 pairs
In simple words: Humans have three pairs of salivary glands that make saliva, which starts digestion in the mouth.

🎯 Exam Tip: Remember the number and names of the major glands associated with digestion, such as salivary glands and pancreas.

 

Question 7. Lier cells synthesize -
(a) Bile juice
(b) Trypsin
(c) Amylopsin
(d) Lipase
Answer: (a) Bile juice
In simple words: Liver cells, also called hepatocytes, are responsible for making bile juice, which helps in digesting fats.

🎯 Exam Tip: Know the specific secretions produced by different organs and their roles in the digestive system.

 

Question 8. Where the islet of Langerhans are found -
(a) Pancreas
(b) Ileum
(c) Colon
(d) Liver
Answer: (a) Pancreas
In simple words: The islet of Langerhans are tiny groups of cells inside the pancreas that make hormones like insulin.

🎯 Exam Tip: Distinguish between the endocrine (hormone-producing) and exocrine (enzyme-producing) functions of organs like the pancreas.

 

Question 9. Vitamin which helps in maturation of RBC -
(a) D
(b) A
(c) B
(d) B12
Answer: (d) B12
In simple words: Vitamin B12 is very important for making sure red blood cells grow properly and become mature.

🎯 Exam Tip: Learn the key vitamins and their specific roles, especially in processes like blood cell formation or bone health.

 

Question 10. The part of the alimentary canal which bears villi -
(a) Stomach
(b) Ileum
(c) Oesophagus
(d) Rectum
Answer: (b) Ileum
In simple words: The ileum, which is part of the small intestine, has tiny finger-like folds called villi that help absorb nutrients into the blood.

🎯 Exam Tip: Identify structures that increase surface area for absorption in the digestive tract and their location.

 

Question 1. Where Kupffer's cells are found?
Answer: Kupffer's cells are found in the liver.
In simple words: These special cells are located in the liver.

🎯 Exam Tip: State the exact location of specialized cells when asked, as precision is important in biology.

 

Question 2. What role of vitamin K?
Answer: Vitamin K plays a crucial role in blood clotting. It helps the liver produce prothrombin, a protein essential for the clotting process.
In simple words: Vitamin K helps your blood to clot and stop bleeding, by helping the liver make a special protein for it.

🎯 Exam Tip: When describing the role of a vitamin, mention the specific function and any key proteins or processes involved.

 

Question 3. Which organ synthesizes and stores glycogen?
Answer: The liver synthesizes and stores glycogen.
In simple words: The liver makes glycogen (stored sugar) and keeps it for when your body needs energy.

🎯 Exam Tip: Recognize the liver's dual role in both synthesizing (making) and storing important biological molecules.

 

Question 4. Deficiency of Vitamin D causes deficiency of which mineral in the body?
Answer: Deficiency of Vitamin D causes a deficiency of calcium in the body.
In simple words: If you don't have enough Vitamin D, your body will also lack calcium, which is bad for bones.

🎯 Exam Tip: Understand the interrelationship between vitamins and minerals, as many vitamins are required for mineral absorption.

 

Question 5. Name the disease caused by protein deficiency.
Answer: The diseases caused by protein deficiency are Kwashiorkor and Marasmus.
In simple words: When a person doesn't get enough protein, they can get diseases called Kwashiorkor and Marasmus.

🎯 Exam Tip: Be able to name specific deficiency diseases and the nutrient whose lack causes them.

 

Question 6. Where the digested fat is absorbed?
Answer: The digested fat is primarily absorbed in the ileum, which is part of the small intestine.
In simple words: Digested fats are mostly taken into the body in the ileum, a part of the small bowel.

🎯 Exam Tip: Know the specific parts of the digestive system responsible for the absorption of different types of nutrients.

 

Question 9. What is bolus?
Answer: Bolus is the soft, rounded mass of chewed food mixed with saliva. It is formed in the mouth after salivary digestion and is then swallowed.
In simple words: A bolus is a soft ball of food that you chew and mix with spit in your mouth before you swallow it.

🎯 Exam Tip: Define key terms clearly and accurately, explaining both what they are and where they are formed or used.

 

Question 10. What are Brunner's glands?
Answer: Brunner's glands are multicellular glands located in the submucosa region of the duodenum. They secrete an alkaline mucus, which helps to protect the duodenal lining from acidic chyme.
In simple words: Brunner's glands are tiny glands in the first part of your small intestine (duodenum) that make a protective slimy fluid.

🎯 Exam Tip: For glands, specify their location, structure (multicellular, unicellular), and the main substance they secrete along with its function.

 

Question 11. What do you understand by Peyer's patches?
Answer: Peyer's patches are clusters of lymphoid tissue (lymph glands) found in the mucosa layer of the small intestine, especially in the ileum. They play a role in the immune surveillance of the gut.
In simple words: Peyer's patches are small groups of immune cells in the small intestine that help protect against germs.

🎯 Exam Tip: When defining anatomical structures, include their location and their primary physiological function.

 

Question 12. What is the sphincter of Odi?
Answer: The sphincter of Oddi is a muscular valve that controls the flow of bile and pancreatic juice from the common bile duct and pancreatic duct into the duodenum. It regulates when these digestive fluids enter the small intestine.
In simple words: The sphincter of Oddi is a muscle that opens and closes to control when bile and pancreatic juice flow into the first part of the small intestine.

🎯 Exam Tip: For sphincters, explain what they control (which substances) and where they are located, emphasizing their regulatory role.

RBSE Class 12 Biology Chapter 22 Short Answer Questions

 

Question 1. Write the functions of the liver.
Answer: The liver performs many vital functions in the body:

• It produces bile juice, which helps in fat digestion and is constantly made in the liver cells.
• The liver detoxifies the body by breaking down many harmful toxins.
• It synthesizes important proteins for the body, such as albumin, fibrinogen, and globulin.
• Urea, a waste product, is formed in the liver through the ornithine cycle.
• It is a key site for glucose metabolism, including glycogenesis (glycogen formation), glycogenolysis (glycogen breakdown), and gluconeogenesis (glucose formation from non-carbohydrate sources).
• The liver also deaminates amino acids and is involved in lipogenesis (fat synthesis).
• It produces heparin, a natural anticoagulant that prevents blood clotting.

In simple words: The liver does many important jobs: it makes bile to digest fats, cleans toxins from the body, makes proteins, and helps manage sugar and fat in the body. It also makes a substance that stops blood from clotting too much.

🎯 Exam Tip: When asked for functions of an organ, try to list a variety of roles (digestive, metabolic, excretory, protective) to show comprehensive understanding.

 

Question 2. What is emulsification? Write its importance.
Answer: Emulsification is the process where large fat globules are broken down into smaller fat droplets, typically with a diameter of about 1 µm. This process occurs due to bile salts present in the bile juice. It is important because the smaller fat droplets have a much larger surface area, allowing the enzyme lipase to act more efficiently and digest the fats.
In simple words: Emulsification is like breaking big drops of fat into many tiny ones with the help of bile. This is important because it makes it easier for fat-digesting enzymes to work on the fat.

🎯 Exam Tip: Define the process clearly, explain how it occurs (the agent), and then state its significance or importance in digestion.

 

Question 3. What are Chylomicrons?
Answer: Chylomicrons are small, round packets formed within the cells of the intestinal mucosa, specifically in the ileum. After fatty acids and glycerol are absorbed into these cells in the presence of bile salts, they are re-synthesized into triglycerides and then packaged into these chylomicrons, which have a diameter of 1-3.5 µm. Chylomicrons are then released into the lacteals (lymphatic vessels) by exocytosis for transport throughout the body.
In simple words: Chylomicrons are tiny bundles of fat that are made inside your gut cells after you digest fat. They help carry fat from your gut into your body through the lymphatic system.

🎯 Exam Tip: For biological particles, explain their composition (what they are made of), where they are formed, and their primary function or transport pathway.

 

Question 4. What is Kwashiorkar disease? Write its symptoms.
Answer: Kwashiorkor disease is a severe form of malnutrition caused by a deficiency of protein, typically affecting children up to 5 years old who consume less than 1 gram of protein per kilogram of body weight per day. This condition can lead to several serious health problems. Some common symptoms include:

• Significant loss of body weight and a lack of desire to eat.
• The skin may become scaly and turn black.
• Oedema (swelling) in the body due to water retention, leading to a swollen belly.
• Hair becomes thin, sparse, and may lose its color, turning greyish.

In simple words: Kwashiorkor is a serious sickness in children caused by not eating enough protein. Symptoms include losing weight, scaly skin, a swollen belly from too much water, and thin, dull hair.

🎯 Exam Tip: When describing a disease, always include its cause, the affected population (if specific), and a clear list of its observable symptoms.

RBSE Class 12 Biology Chapter 22 Essay Type Questions

 

Question 1. Describe the alimentary canal of man. Give a labelled diagram.
Answer: The human alimentary canal is a long, muscular tube that extends from the mouth to the anus. It is responsible for the digestion and absorption of food. This tube shows many modifications along its length to perform different functions. It develops from both embryonic ectoderm and endoderm and is approximately 9 meters long in an adult. The main parts of the alimentary canal are:

Divisions of the Alimentary Canal:

1. Mouth and Buccal Cavity:

• The mouth is a transverse, slit-like opening.
• The buccal cavity contains the tongue and teeth.
• The ventral side of the buccal cavity is occupied by a flat, muscular tongue.
• The tongue has taste buds that are sensitive to sour, salty, sweet, and bitter tastes.
• Human tongues have three types of taste buds: Circumvallate, Fungiform, and Filiform. Foliate taste buds are absent in humans.
• Functions of the tongue include: acting as a gusto-receptor (for taste), aiding in mastication (chewing) of food, helping in swallowing the bolus, cleaning the teeth, and assisting in human speech.
• The buccal cavity contains upper and lower jaws, which are fitted with teeth. The arrangement of teeth on the jaws is called dentition.

Salient Features of Teeth:

• Mammalian teeth are thecodont, meaning they are embedded in sockets of the jawbone.
• They are diphyodont, having two sets of teeth in a lifetime: milk (deciduous) teeth (20 in number) and permanent (non-deciduous) teeth (32 in number).
• Mammalian teeth are heterodont, consisting of four different types: Incisors (for cutting), Canines (for tearing), Premolars (for grinding), and Molars (for grinding). The last four molars are called wisdom teeth.
• The dental formula represents the position, number, and type of teeth in the jaws. A full set of teeth can be calculated by doubling the dental formula for half of one jaw.

1.2. Pharynx:

• The buccal cavity opens into the pharynx, which is less distinct in mammals.
• The dorsal part is called the nasopharynx, and the ventral part is the oropharynx.
• The pharynx is lined with stratified squamous epithelium.
• Posteriorly, the pharynx has two openings: the gullet (leading to the oesophagus) and the glottis (leading to the trachea). The oropharynx opens into the oesophagus through the gullet.

1.3. Oesophagus:

• The oesophagus is mainly made of smooth muscles.
• Its wall consists of four layers: Serosa (outermost), Musculature (outer longitudinal and inner circular muscles), Submucosa (connective tissues, blood vessels, nerves, lymph ducts), and Mucosa (innermost, stratified squamous epithelium).

1.4. Stomach:

• The stomach is a bag-like structure located in the upper left part of the abdominal cavity, just below the diaphragm.
• It has a fundus (anterior), body (middle), and pyloric part (posterior).
• There is a cardiac sphincter between the oesophagus and the stomach.
• The basal opening of the stomach is controlled by a pyloric sphincter.
• The main body forms 80% of the stomach and secretes most of the gastric juice.

Histology of Stomach: The stomach wall layers, from outside to inside, are:
(1) Serosa: This is the outermost modified visceral peritoneum, made of squamous epithelium.
(2) Musculature: It has an outer longitudinal and an inner circular muscle layer, with an Auerbach plexus between them. The stomach also has an additional oblique muscle layer.
(3) Sub-mucosa: This is the most developed layer, containing connective tissues, blood vessels, nerves, lymph vessels, and gland cells. Meissner's plexus is found in the sub-mucosa.
(4) Muscularis mucosa: This innermost layer is made of columnar epithelium and contains many Goblet cells that secrete mucus. It also has oxyntic/parietal cells that secrete dilute HCl and zymogen/peptic/chief cells that secrete gastric enzymes.

1.5. Intestine:

• The intestine is the longest part of the alimentary canal, measuring 7 to 8 meters in humans.
• It is divided into four parts: duodenum, jejunum, ileum (forming the small intestine) and the large intestine.
• The pylorus of the stomach opens into the intestine.
• The small intestine is about 7.5 meters long and has three parts:

(1) Duodenum: This is the anterior-most, U-shaped part, about 15 cm long. The gall bladder's bile duct, also called the duodenum, enters here. The pancreas, irregular in shape, is situated between the limbs of the duodenum. Its histology is similar to the stomach's, but it lacks oblique muscles in its musculature. The submucosa has special Brunner's glands that secrete mucus, and the mucosa forms many crypts of Lieberkühn with many argentaffin cells.
(2) Jejunum: This is the middle and smaller part of the small intestine.
(3) Ileum: This is the longest and coiled part of the intestine, kept in place by mesenteries. Its musculature lacks oblique muscles, and its submucosa is without Brunner's glands. The mucosa has many villi and crypts of Lieberkühn. The connective tissues in the villi, called lamina propria, contain blood vessels and lymph vessels. Peyer's patches (lymph nodes with lymphocytes) are found in the submucosa. It is about 6.5 meters long, and its inner cavity has special longitudinal folds called folds of Kackring.

1.5.2. Large Intestine:

• The large intestine is shorter than the small intestine but has a larger diameter.
• It includes the caecum, colon, and rectum.

(1) Caecum: This special structure is found in herbivorous animals for digesting cellulose. In humans, it forms the vestigial vermiform appendix, whose opening is closed by a sphincter. The ileocaecal valve is also vestigial, incorporated into the wall, and contains lymph nodes that form lymphocytes.
(2) Colon: Its length is 1.5 to 2 meters in humans. The human colon has four parts: Ascending colon, Transverse colon, and Descending colon.
In simple words: The alimentary canal is a long tube in your body that takes food from your mouth to your anus. It has many different parts like the mouth, pharynx, esophagus, stomach, and intestines, each doing a special job to break down food and take in nutrients. The small intestine is very long and coiled, while the large intestine is shorter but wider.

🎯 Exam Tip: For descriptive questions like this, organize your answer with clear headings and bullet points for each section of the alimentary canal. Include key features, functions, and any associated cells or glands for full marks.

 

Question 2. Describe the structure of human tooth giving labelled diagram.
Answer:
The structure of a human tooth is complex. Mammalian teeth are thecodont, meaning they are set deeply into sockets in the jawbone. They are also diphyodont, which means there are two sets of teeth during a lifetime: milk (deciduous) teeth and permanent teeth. Milk teeth number 20, while permanent teeth number 32. Lastly, human teeth are heterodont, meaning there are four different types of teeth: incisors, canines, premolars, and molars. The last four molars are sometimes called wisdom teeth.
The tooth originates from ectomesoderm and has three main parts:

• **Crown:** This is the visible part of the tooth. It is chisel-shaped in incisors, pointed in canines, and broad and flat in the cheek teeth (premolars and molars).
• **Neck:** This is the middle part of the tooth, typically covered by the gums.

The tooth remains embedded in the bony socket and is surrounded by a periodontal membrane. It is mainly composed of dentine, which contains canaliculi. The crown is covered by enamel, the hardest substance in the body (95% inorganic substances). The root is covered by cement, secreted by cementocytes. Each tooth has a pulp cavity filled with pulp, containing connective tissues, blood capillaries, nerves, and odontoblasts. This cavity closes off through an apical pore later in life.
The dental formula shows the position, number, and type of teeth in the jaws. For half of the jaws, the formula is used, and the total number of teeth is found by doubling it. For infants, the dental formula is: Infant \( \rightarrow \) I 2/2, C 1/1, Pm 0/0, M 2/2 \( \implies \) 10 \( \times \) 2 \( \implies \) 20.
In simple words: Human teeth are firmly fixed in the jaw, grow in two sets, and come in four different shapes. They have a visible crown, a neck covered by gums, and a root. The visible part is covered by very hard enamel.

🎯 Exam Tip: Remember the three key terms for mammalian teeth: thecodont, diphyodont, and heterodont, and be able to explain each one for full marks.

 

Question 3. Where & how the digested food is absorbed in human beings.
Answer:
Digested food is primarily absorbed in the ileum, which is part of the small intestine. This absorption happens into the bloodstream through a process called active transport. The inner lining of the ileum has many small, finger-like folds called villi, which greatly increase the surface area for absorption. There are about 45 lakh villi in the human ileum. A hormone called Millikin helps increase the movement of these villi, further aiding absorption. Monosaccharides (like glucose, galactose, fructose, and mannose) and amino acids are absorbed directly into the blood, also through active transport, with the help of water. Alcohol is absorbed by simple diffusion throughout the entire alimentary canal.
After digestion, chylomicrons (small fat packets formed in the mucosal cells of the ileum from absorbed fatty acids and glycerol) are released into lymphatic vessels called lacteals via exocytosis. From the lymph, these chylomicrons eventually enter the bloodstream where the subclavian and jugular veins meet. Water-soluble vitamins are absorbed into the blood by diffusion, while vitamin B12 needs a special substance called a castle factor for its absorption. Fat-soluble vitamins are absorbed with the help of bile salts. On average, about 20 liters of water can be absorbed in the human intestine each day.
In simple words: Most digested food is taken into the blood in the small intestine, especially in the ileum, which has tiny folds called villi to soak up nutrients. Fats go into lymph first, and water is absorbed throughout the intestine.

🎯 Exam Tip: Remember that villi are key for increasing surface area in the small intestine, and active transport moves many nutrients against their concentration gradient.

 

Question 4. Explain intestinal digestion in human beings.
Answer:
Intestinal digestion in humans involves several digestive juices and enzymes working in the small intestine.
First, **Bile Juice** is produced by the liver, about 1 liter per day. Its composition includes:

• Water: 89.0%
• Bile salts (Taurocholate & Glycocholate): 6.0%
• Bile pigments (Bilirubin and Biliverdin): 3.5%
• Cholesterol: 0.8%
• Inorganic salts: 0.7%

Functions of bile juice:

• It neutralizes the acidic food mixture (chyme) coming from the stomach.
• It emulsifies fats, breaking large fat globules into smaller ones so enzymes can act on them.
• It acts as a bactericidal agent, helping to kill bacteria.
• It helps absorb fatty acids.
• It helps excrete excess cholesterol and bile pigments (from hemoglobin breakdown).

Next, **Pancreatic Juice** is released from the pancreas. It is a clear, alkaline fluid with a pH of 8. It contains 98.5% water and 1.5% solids. About 0.5 to 1 liter is secreted daily. Pancreatic juice has two main parts:
(1) **Salt Part:**

• It is controlled by the secretin hormone.
• It contains chlorides, carbonates, and bicarbonates of sodium, potassium, and calcium.
• It makes the chyme alkaline.

(2) **Enzymatic Part:**

• This part is controlled by the pancreas.
• It includes several main enzymes:
1. Trypsinogen: Active trypsin and chymotrypsin break down proteins into peptones and proteoses. Trypsin specifically breaks peptide bonds with arginine and lysine, while chymotrypsin targets peptide bonds with aromatic amino acids.

(3) **Pancreatic Amylase:**

• Also known as amylopsin.
• It converts complex carbohydrates (polysaccharides) into simpler disaccharides.

(4) **Lipase:**

• Also called steapsin.
• It converts emulsified fats into fatty acids and glycerol.

Digestion in the duodenum leads to the formation of chyle, which then moves into the ileum. In the ileum, the entry of chyle triggers the release of two hormones: Enterokinin and Villikrinin. Enterokinin stimulates the intestinal glands to secrete intestinal juice, also known as succus entericus. This intestinal juice is also alkaline (pH 8) and contains 98.5% water and 1.5% solids. It has many enzymes that continue digestion:

• Sucrase: Sucrose \( \rightarrow \) Glucose + Fructose
• Maltase: Maltose \( \rightarrow \) Glucose + Glucose
• Lactase: Lactose \( \rightarrow \) Glucose + Galactose
• Lipase: Emulsified fats \( \rightarrow \) Fatty acids + Glycerol
• Aminopeptidases: Peptones \( \rightarrow \) Amino acids & Protcoses (Proteins and Proteoses)

In the ileum, almost all substances are completely digested, except for cellulose.
In simple words: Intestinal digestion uses bile juice to break down fats, pancreatic juice with enzymes to break down proteins and carbs, and intestinal juice to finish breaking down everything else into tiny parts that the body can use.

🎯 Exam Tip: When explaining digestion, always mention the key digestive juices (bile, pancreatic, intestinal), their primary functions, and the main enzymes involved at each stage.