RBSE Solutions for Class 12 Biology Chapter 22 Man-Digestive System

RBSE Solutions for Class 12 Biology Chapter 22 Man-Digestive System

Rajasthan Board RBSE 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

Question 2.
Pancreatic juice is –
(a) Acidic
(b) Alkaline
(c) Neutral
(d) None of the above
Answer:
(b) Alkaline

 

Question 3.
Kupffer’s cells are found in –
(a) Pancreas
(b) Small intestine
(c) Large intestine
(d) Liver
Answer:
(d) Liver

Question 4.
Amylase enzyme acts on which substrate –
(a) Protein
(b) Carbohydrate
(c) Fatty acid
(d) Fat
Answer:
(b) Carbohydrate

Question 5.
Which converts inactive pepsinogen into active pepsin –
(a) Ptyalin
(b) HCL
(c) Bile
(d) Renin
Answer:
(b) HCL

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

 

Question 7.
Lier cells synthesize –
(a) Bile juice
(b) Trypsin
(c) Amylopsin
(d) Lipase
Answer:
(a) Bile juice

Question 8.
Where the islet of Langerhans are found –
(a) Pancreas
(b) Ileum
(c) Colon
(d) Liver
Answer:
(a) Pancreas

Question 9.
Vitamin which helps in maturation of RBC –
(a) D
(b) A
(c) B
(d) B₁₂
Answer:
(d) B₁₂

Question 10.
The part of the alimentary canal which bears villi –
(a) Stomach
(b) ileum
(c) Oesophagus
(d) Rectum
Answer:
(b) ileum

RBSE Class 12 Biology Chapter 22 Very Short Answer Questions

Question 1.
Where Kupffer’s cells are found?
Answer:
Liver.

Question 2.
What role of vitamin K?
Answer:
It helps in blood clotting by forming prothrombin in the liver.

Question 3.
Which organ synthesizes and stores glycogen?
Answer:
Liver.

Question 4.
Deficiency of Vitamin D causes deficiency of which mineral in the body?
Answer:
Calcium.

 

Question 5.
Name the disease caused by protein deficiency.
Answer:
Kwashiorkor and Marasmus.

Question 6.
Where the digested fat is absorbed?
Answer:
Ileum.

Question 7.
Vitamin which can be synthesizes in the human body?
Answer:
Vitamin – D.

Question 8.
Write the dental formula of man.
Answer:
12/2, C 1/1, Pm 2/2, M 3/3 ⇒ 16 × 2 ⇒ 32.

Question 9.
What is bolus?
Answer:
The semisolid mass formed in the buccal cavity after salivary digestion is called bolus.

 

Question 10.
What are Brunner’s glands?
Answer:
They are multicellular glands which are found in the submucosa region of the duodenum. They secrete mucously.

Question 11.
What do you understand by Peyer’s patches?
Answer:
The patches of lymph glands found in the mucosa layer of the small intestine are called Peyer’s patches.

Question 12.
What is the sphincter of Odi?
Answer:
The common bile duct opens into the duodenum. It’s opening is regulated by a sphincter of Odi.

RBSE Class 12 Biology Chapter 22 Short Answer Questions

Question 1.
Write the functions of the liver.
Answer:
Functions of the Liver:

• It forms bile juice. The bile juice is synthesized in the liver cells constantly & drops into the bile canaliculi.
• The bile canaliculi unite to form cystic ducts which finally open into the gall bladder.
• The liver stores vitamins A, D & B_12.
• It synthesizes blood clotting factors.
• During the embryonic stage, it acts as a haemopoietic organ.
• It stores extra food in the form of glycogen.
• It performs detoxification of many toxins.
• It synthesizes many proteins like albumin, fibrinogen, globulin etc.
• It synthesizes urea by ornithine cycle.
• It is the site for glycogenesis, glycogenolysis, gluconeogenesis, deamination, lipogenesis etc.
• It synthesizes heparin which is an anticoagulant.

Question 2.
What is emulsification? Write its importance.
Answer:
Fats are found in large globules which can’t be acted by enzyme lipase. The bile salts found in the bile juice coverts bigger fat globules into smaller globules of lu diameter. It is called emulsification. The emulsified fat can easily be acted by the enzyme lipase.

 

Question 3.
What are Chylomicrons?
Answer:
The cells of Mucosa of ileum absorb fatty acids and glycerol in the presence of bile salts. The cells synthesize triglycerides and pack them in small round packets which are called as chylomicrons (Diameter lµ to 3, 5µ). They are released into the lacteals by exocytosis.

Question 4.
What is Kwashiorkar disease? Write its symptoms.
Answer:
Kwasikorkar disease:
It is a deficiency disease which occurs in children up to 5 years due to a deficiency of proteins. Suc children consume less than 1 gm protein per kg. body weight per day.
Symptoms:

• Loss of body weight and distaste to food.
• Skin becomes scaly and black.
• Oedema in the body due to water retention and building of belly.
• Hair becomes scanty, thin and grey.

Question 5.
What is marasmus disease? Write its symptoms.
Answer:
Marasmus:
It is a deficiency disease which occurs in children up to one year due to deficiency of proteins, carbohydrates and fats.
Symptoms:

• A sharp decrease in body weight (less than 60% of the standard bodyweight).
• The body is reduced to a skeleton, wrinkled skin, Sunken eyes etc.
• Thin limbs Ribs visible etc.

PEM can be corrected by consuming a protein-rich diet.

 

RBSE Class 12 Biology Chapter 22 Essay Type Questions

Question 1.
Describe the alimentary canal of man. Give a labelled diagram.
Answer:
Alimentary Canal:
1. The alimentary canal is a simple tube between the mouth & the anus which exhibits many modifications to perform different functions.

2. The alimentary canal originates from embryonic ectoderm & endoderm.

3. Its length is about 9 meter.

1. Mouth and Buccal Cavity:

• It is a transverse slit-like structure.
• The mouth is guarded by a pair of lips viz. upper lip and lower lip. The lips of the mammals are muscular and movable.
• The mouth opens into a buccal cavity.
• It is a cavity in the head region. Its dorsal side is made up of palate, the ventral side is made up of throat while both the lateral sides are made up of cheeks.
• The ventral side of the buccal cavity is occupied by a flat and muscular tongue.
• The tongue bears taste buds which are sensory to sour, salty, sweet and bitter tastes.
• Human tongue bears three types of taste buds. viz.,
  1. Circumuallate
  2. Fungiform
  3. Filiform
• Foliate taste buds are absent in human beings.
• Functions of the tongue
  1. It functions as gusto-receptor.
  2. It helps in the mastication of the food.
  3. It helps in the swallowing of the bolus.
  4. It acts as a brush to clean the teeth.
  5. In human beings, it helps in speech.
• The buccal cavity has upper & lower jaws which are beset with teeth.
• The arrangement of the teeth on the jaws is called dentition.

1.1. Salient Features of Teeth:

• The mammalian teeth are thecodont.
• The mammalian teeth are diphyodont i.e. there are two sets of the teeth in the life viz.,
  1. Milk or Deciduous teeth – the There number is 20.
  2. Permanent or Non-deciduous teeth – the There number is 32.
• The mammalian teeth are heterodont i.e. 4 types of teeth are found viz.,
  1. Incisors
  2. Canines
  3. Premolars
  4. Molars
• Last four molars are called wisdom teeth.
• Dental formula:
  1. The dental formula denotes position, number & type of teeth in the jaws.
  2. The dental formula denotes teeth in half of the jaws.
  3. The total number of teeth can be obtained by doubling the dental formula.
  4. The dental formula of Man
     • Infant ⇒ 12/2, C 1/1, Pm 0/0, M2/2 ⇒ 10 × 2 ⇒ 20
     • Adult ⇒ 12/2, C 1/1, Pm 2/2, M 3/3 ⇒ 16 × 2 ⇒ 32

The tooth is ectomesodermal in origin and each tooth have three parts –
(1) Crown: It is the exposed part of the tooth which is chisel-shaped in the incisors, pointed in the canines and broad & flat in the cheek teeth.

(2) Neck: It is the middle part of the tooth which is covered by the gums.

(3) Root:

• It remains embedded in the bony socket.
• The number of the root in the incisors & canines is 1 – 1, in premolars is 2 and in molars is 3 – 5.
• The root is bounded by a periodontal membrane.
• The tooth is mainly made up of dentine. It is provided with canaliculi.
• The crown part of the tooth is covered by a hard substance, the enamel which is formed by ectodermal ameloblasts.
• It is the hardest substance in the body which consists of 95% inorganic substances (calcium phosphate, Mg, Na, K, hydroxy – peptide etc.) and 5% water.
• The root of the tooth is covered by a substance called cement, it is secreted by the cementocytes.
• Each tooth has a pulp cavity which is full of pulp.
• The pulp consists of connective tissues, blood capillaries, nerves & odontoblasts.
• The pulp cavity Opens out through an apical pore which gets closed later on.

1.2. Pharynx:

• The buccal cavity opens into pharynx which is comparatively less distinct in mammals.
• The dorsal part of the pharynx is called as nasopharynx whereas its ventral part is termed as the oropharynx.
• The pharynx is lined by stratified squamous epithelium.
• Posteriorly, the pharynx has 2 openings viz., gullet and glottis.
• The oropharynx opens into the oesophagus through the gullet.

 

1.3. Oesophagus:

• The oesophagus passes through the neck & thorax. It pierces through the diaphragm and finally opens into the stomach.
• Its length depends upon the length of the neck. In man, it’s length is about 25 cm.
• Internally, it has many longitudinal folds.
• The anterior part of the oesophagus is made up of striated (Voluntary) muscles.
• Rest part is made up of smooth muscles.
• The wall of Oesophagus consists of follower layers:
  1. Serosa: Outermost layer
  2. Musculature: It includes an outer layer of longitudinal muscles and an inner layer of circular muscles.
  3. Submucosa: It is made up of connective tissues. It has blood vessels, nerves and lymph ducts.
  4. Mucosa: It is the innermost layer which is made up of stratified squamous epithelium.

1.4. Stomach:

• It is a bag-like structure which is situated in the anterior left part of the abdominal cavity. just below the diaphragm.
• Its anterior part is called the fundus, middle part as body and posterior part as pyloric.
• There is a cardiac sphincter (valve) between the oesophagus & the stomach.
• Similarly, the basal opening of the stomach is regulated by a pyloric sphincter.
• The main body forms 80% of the stomach and it secretes most of the part of the gastric juice.

Histology of Stomach:
The wall of the stomach consists of following layers from outside to inside –
(1) Serosa: It is modified visceral peritoneum which is made up of squamous epithelium.

(2) Musculature:

• It includes an outer layer of longitudinal muscles and an inner layer of circular muscles. There is an Aurabach plugin between the longitudinal and circular muscles.
• The stomach has an additional layer of oblique muscles.

(3) Sub-mucosa:

• It is the most developed layer which is made up of connective tissues. In addition, it includes blood vessels, nerves, lymph vessels & gland cells.
• There is a Meissner’s plugin the sub-mucosa.

(4)Muscularis mucosa:

• It is situated in the sub-mucosa.
• It consists of three layers viz., the outer layer of circular muscles, a middle layer of longitudinal muscles & an inner layer of circular muscles.

(5) Mucosa:
It is the innermost layer which is made up of columnar epithelium.
It includes many Goblet cells to secrete mucously.
It also contains oxyntic cells of parietal cells which secrete dilute HCl.
It also bears zymogen or peptic or chief cells which secrete gastric enzymes.

 

1.5. Intestine:

• It is the longest part of the alimentary canal. Its the length in the rabbit is 4 to 5 metre and in human beings is 7 to 8 metre.
• The intestine is divisible into four parts viz., duodenum, jejunum, ileum or small intestine & large intestine.

1.5.1.
Intestine:

• The pylorus part of the stomach opens into the intestine.
• Its length is about 7.5 meter. It consists of three parts:

(1) Duodenum:

• It is the anterior-most part of the intestine which is U – shaped & it is of 15 cm in length.
• The gall bladder gives out a bile duct which is also called a Duodenum.
• There is a pancreas in between the limbs of the duodenum which is irregular in shape.
• The pancreas opens into the middle part of the duodenum through a pancreatic duct
  which is also called as Wirsung’s duct.
• In human beings, the bile duct & the pancreatic duct open into an ampulla of Vator which in turn open into the proximal part of the duodenum. This opening is guarded by a sphincter of Odi.
• Histology of Duodenum:
• The histology of duodenum is similar to the histology of the stomach except the following:
  1. The musculature of the duodenum lack oblique muscles.
  2. The sub-mucosa layer of the duodenum is provided with special Brunner’s glands which secrete mucously.
  3. The mucosa layer of the duodenum forms many crypts of Leiberkuhn. They have a large number of argentaffin cells.

(2) Jejunum: It is a middle and smaller part.

(3) Ileum:

• It is the longest part of the intestine which is coiled. The coiled shape is maintained with the help of mesenteries.
• It’s musculature lack the oblique muscles and its submucosa is without Burner’s glands.
• Its mucosa layer forms many Villi & Crypts of Leiberkuhn. The connective tissues in the villi are called lamina propria which consists of B.Vs, & lymph vessels.
• There are Peter’s patches in the submucosa which are lymph nodes and form lymphocytes.
• Its length is about 6.5 meter.
• The intestinal cavity has special longitudinal folds which are called as folds of Kackring.
• The mucosa of the ileum has special Paneth’s cells which secrete intestinal juice or succus entericus.

1.5.2. Large Intestine:

• This pan of the intestine is shorter but its diameter is large.
• The large intestine includes caecum, colon and rectum.

(1) Caecum:

• It is a special structure which is found in herbivorous animals to digest cellulose.
• In human beings. the caecum is found in the form of the vestigial vermiform appendix. Its opening remains closed by a sphincter.
• The ileocaecal valve is also vestigial which get incorporated into the wall. It contains lymph nodes which form lymphocytes.

(2) Colon:

• Its length is 1.5 to 2 metre in human beings.
• Human colon has four parts –
  1. Ascending colon.
  2. Transverse colon.
  3. Descending colon.
  4. Sigmoid colon.
• Its outer surface has a Longitudinal muscle band which is called a taenia coil.

 

(3) Rectum:

• It is the last part of the alimentary canal. Its length is 18 – 20 cm in human beings.
• The terminal part of the rectum is called an anal canal which leads outside through the anus.
• Both the anal canal and anus are ectodermal in origin.
• The anus is controlled by an anal sphincter which is made up of striated muscles.
• The rectum is without serosa and mesenteries.

Question 2.
Describe the structure of human tooth giving labelled diagram.
Answer:
Structure of human tooth:

• The mammalian teeth are thecodont.
• The mammalian teeth are diphyodont i.e. there are two sets of the teeth in the life viz.,
  1. Milk or Deciduous teeth – the There number is 20.
  2. Permanent or Non-deciduous teeth – the There number is 32.
• The mammalian teeth are heterodont i.e. 4 types of teeth are found viz.,
  1. Incisors
  2. Canines
  3. Premolars
  4. Molars
• Last four molars are called wisdom teeth.
• Dental formula:
  1. The dental formula denotes position, number & type of teeth in the jaws.
  2. The dental formula denotes teeth in half of the jaws.
  3. A total number of teeth can be obtained by doubling the dental formula.
  4. The dental formula of Man
     • Infant ⇒ 12/2, C 1/1, Pm 0/0, M2/2 ⇒ 10 × 2 ⇒ 20
     • Adult ⇒ 12/2, C 1/1, Pm 2/2, M 3/3 ⇒ 16 × 2 ⇒ 32

The tooth is ectomesodermal in origin and each tooth have three parts –
(1) Crown: It is the exposed part of the tooth which is chisel-shaped in the incisors, pointed in the canines and broad & flat in the cheek teeth.

(2) Neck: It is the middle part of the tooth which is covered by the gums.

(3) Root:

• It remains embedded in the bony socket.
• The number of the root in the incisors & canines is 1 – 1, in premolars is 2 and in molars is 3 – 5.
• The root is bounded by a periodontal membrane.
• The tooth is mainly made up of dentine. It is provided with canaliculi.
• The crown part of the tooth is covered by a hard substance, the enamel which is formed by ectodermal ameloblasts.
• It is the hardest substance in the body which consists of 95% inorganic substances (calcium phosphate, Mg, Na, K, hydroxy – peptide etc.) and 5% water.
• The root of the tooth is covered by a substance called cement, it is secreted by the cementocytes.
• Each tooth has a pulp cavity which is full of pulp.
• The pulp consists of connective tissues, blood capillaries, nerves & odontoblasts.
• The pulp cavity Opens out through an apical pore which gets closed later on.
  

 

Question 3.
Where & how the digested food is absorbed in human beings.
Answer:
Absorption of the digested food:

• There is the absorption of the digested food in the ileum into the blood with the help of active transport.
• The villi provide an increased surface for the absorption. The Millikin in hormone enhances absorption by increasing villi movements.
• There is about 45 lakh of villi in the ileum of human beings.
• The monosaccharides (glucose, galactose, fructose, mannose etc.) are absorbed directly into the blood by active transport in the presence of water.
• The amino acids are also absorbed directly into the blood by active transport.
• Alcohol is absorbed by diffusion in the whole alimentary canal.
• The fatty acids before the absorption form an emulsion in the presence of bile salts which is called micelles.
• These micelles are taken up by the epithelial cells with the help of pinocytosis.
• The epithelial cells pack these fatty acids in small packets which are called chylomicrons.
• The diameter of the chylomicron is about 1µ. The chylomicrons are released into the lacteals by exocytosis.
• The chylomicrons from the lymph reach into the blood at the junction between subclavian & jugular veins.
• The water-soluble vitamins are absorbed directly into the blood by diffusion.
• Absorption of the vitamin B12 needs the presence of a castle factor.
• Fat-soluble vitamins are absorbed with the help of bile salts like the absorption of the fatty acids.
• About 20 litres of water can be absorbed in human intestine per day.

Question 4.
Explain intestinal digestion in human beings.
Answer:
Digestion in Duodenum:

• The entry of chyme into the duodenum results in the secretion of bile juice.
• The bile juice is greenish-yellow digestive juice which is alkaline (pH – 7 to 8). It is without any digestive enzyme. In human beings, about 1 litre of the bile juice is produced every day.
• Chemical composition of the bile-The bile juice includes the following substances –
  • Water – 89.0%
  • Bile salts – 6.0% (Taurocholate & Glycocholate)
  • Bile pigments – 3.5% (Bilirubin and Biliverdin)
  • Cholesterol – 0.8%
  • Inorganic salts – 0.7%

Functions of the bile juice:

• It neutralizes the acidic medium of the chyme.
• The bile salts perform emulsification of the fats.
• It acts as a bactericidal.
• The bile salts help in the absorption of the fatty acids.
• It excretes an excess of the cholesterol.
• It excretes bile pigments which are formed in the liver by the degradation of the haemoglobin.
• The duodenum also receives the pancreatic juice.
• The pancreatic juice is a colourless & alkaline juice (pH 8). It contains 98.5% water & 1.5% of solids. In human beings, 0.5 to 1 litre of pancreatic juice is secreted per day.

The pancreatic juice has 2 parts –
(1) Salt part:

• It is under the control of the secretin hormone.
• It contains chloride, carbonate & bicarbonates of sodium, potassium & calcium.
• It makes the chyme alkaline.

(2) Enzymatic part:

• It is secreted under the control of pancreas.
• It includes the following main enzymes –
  1. Trypsinogen
  2. Chymotrypsinogen

• Active trypsin & chymotrypsin covert the proteins completely into peptones & proteoses.
• The trypsin breaks the peptide bonds formed between the arginine and lysine amino acids.
• Similarly, the chymotrypsin breaks the peptide bonds formed between the aromatic amino acids.

(3) Pancreatic amylase:

• It is also called as amylopsin.
• It converts simple polysaccharides into disaccharides.

 

(4) Lipase:

• It is also called as steapsin.
• It converts emulsified fats into fatty acids & glycerol.
• Digestion in the duodenum results in the formation of chyle which enters into the ileum.

Digestion in Ileum:

• The entry of the chyle into ileum results in the secretion of two hormones viz., Enterokinin & Villikrinin.
• The entertaining acts on the intestinal glands & results in the secretion of intestinal juice or succus entericus.
• The intestinal juice is an alkaline juice (pH – 8). It contains 98.5% water & 1.5% solids.
• It includes many enzymes such as invertase, maltase, lactase, lipase, aminopeptidase, nuclease, nucleotidase, nucleosidase.
  1. Sucrose + Sucrase → Glucose + Fructose
  2. Maltose + Maltase → Glucose + Glucose
  3. Lactose + Lactase → Glucose + Galactose
  4. Emulcified fats + Lipase → Fatty acids + Glycerol
  5. Peptones + Amino peptidases → Amino acids & Protcoses.
• In the ileum, there is complete digestion of all substances except the cellulose.

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