Digestive System - Questions & Answers

1. Given below is a jumbled sequence of the different parts of the human alimentary canal. Rewrite them in correct sequence.
Stomach, Oesophagus, Large intestine, Small intestine, Pharynx.
Pharynx, Oesophagus, Stomach, Small intestine, Large intestine.

3. Give the technical names for the following types of teeth in humans (on each side, in each jaw)
(i) The three last grinders.
Molars
(ii) The pointed tooth for holding and tearing.
Canines
(iii) The broad sharp cutting teeth.
Incisors
(iv) The two temporary (deciduous) grinding teeth.
Premolars

4. Name the following parts of a tooth :
(i) Part exposed above the gum.
Crown
(ii) The hard substance making the covering of the tooth.
Enamel
(iii) The soft connective tissue contained in the central space of the tooth.
Pulp
(iv) Bone-like structure fixing the root in position.
Cementum
(v) Slight constriction between the root and the crown.
Neck

1. Mention if the following statements are true (T) or false (F) :
(i) Saliva moistens and lubricates food.
True (T)
(ii) Saliva contains a protein-digesting enzyme.
False (F)
(iii) Saliva tends to destroy germs in the mouth.
True (T)
(iv) Peristalsis occurs through all regions of the gut.
True (T)
(v) The food in stomach stays for about 10 hours.
False (F)
(vi) Gastric juice is alkaline.
False (F)
(vii) Gastric juice contains pepsinogen.
True (T)

2. Name the three salivary glands.
Parotid glands, Submandibular glands, and Sublingual glands.

1. Mention if the following statements are true (T) or false (F) :
(i) Intestinal villi have a lymph vessel called lacteal.
True (T)
(ii) Intestine is narrow for fast movement of food.
False (F)
(iii) Large intestine secretes no enzymes.
True (T)
(iv) Bile neutralizes the acid content of the food received from the stomach.
True (T)
(v) Pancreatic juice has enzymes to digest all the major components of food.
True (T)
(vi) The anus is surrounded by circular muscles.
True (T)

2. Name the following :
(i) The three subdivisions of the small intestine.
Duodenum, Jejunum, Ileum.
(ii) The three subdivisions of the large intestine.
Caecum, Colon, Rectum.

3. Name the enzyme which digests :
(i) starch in the mouth
Ptyalin (Salivary amylase)
(ii) fats in the ileum
Intestinal Lipase
(iii) protein in duodenum
Trypsin
(iv) sucrose in the ileum
Sucrase (Invertase)

4. What are the end-products of digestion of :
(i) Proteins
Amino acids
(ii) Fats
Fatty acids and glycerol
(iii) Starch
Maltose (and eventually glucose)
(iv) Sucrose
Glucose and fructose

Fill in the blanks.
(i) Liver stores glucose as glycogen .
(ii) Liver produces red blood cells only in embryo.
(iii) Urea is produced in liver by the deamination of extra amino acids .
(iv) For testing the action of saliva on starch, the material has to be kept at a temperature of about 38 °C.

Mention the constituent of food if the end result of the test shows :
(i) White to yellow and yellow to orange colour.
Protein
(ii) Turning blue-black after adding iodine solution.
Starch
(iii) Blue green to deep red with appearance of precipitate.
Glucose (Sugar)
(iv) Ash that does not burn after continued heating.
Minerals

1. Choose the correct answer from the options given below :
(i) Pylorus is an opening from :
(a) oesophagus into stomach
(b) mouth cavity into oesophagus
(c) stomach into intestine
(d) intestine into rectum
(c) stomach into intestine

(ii) Gastric juice contains :
(a) HCl and pepsin
(b) pepsin and trypsin
(c) trypsin and HCl
(d) amylopsin and pepsin
(a) HCl and pepsin

(iii) The water from the digested food is mainly absorbed by :
(a) stomach
(b) duodenum
(c) colon
(d) rectum
(c) colon

(iv) Which one of the following pairs of types of teeth perform one common function as stated against it?
(a) Incisors, canines — Holding
(b) Canines, premolars — Tearing
(c) Premolars, molars — Grinding
(d) Molars, incisors — Tearing
(c) Premolars, molars — Grinding

(v) The hardest substance in the human body is :
(a) Bone
(b) Enamel
(c) Cement
(d) Dentine
(b) Enamel

(vi) Which of the following teeth is bicuspid ?
(a) Molars
(b) Incisors
(c) Premolars
(d) Canines
(c) Premolars

(vii) The temperature range within which enzymes can act best is :
(a) 20° to 30°C
(b) 35° to 40°C
(c) 40° to 45°C
(d) 35° to 50°C
(b) 35° to 40°C

(viii) Heterodont dentition is found in :
(a) Humans
(b) Snake
(c) Frog
(d) Lizards
(a) Humans

(ix) Which of the following enzymes is not found in pancreatic juice ?
(a) Sucrase
(b) Trypsinogen
(c) Amylopsin
(d) Steapsin
(a) Sucrase

(x) The process of conversion of excess glucose into glycogen is termed as :
(a) Glycolysis
(b) Glycogenesis
(c) Glycogenolysis
(d) Defaecation
(b) Glycogenesis

(xi) Name the salivary glands P, Q and R based on their location given below :
P: Beneath the ears
Q: Below the tongue
R: Beneath the lower jaw
P — Parotid, Q — Sublingual, R — Submandibular

(xii) A biology teacher asked her students to give two examples of enzymes which act on different forms of carbohydrates.
Nishtha said : Amylopsin and invertase.
Ankur said : Steapsin and Maltase.
Prakriti said : Ptyalin and Amylopsin.
Aakash said : Maltase and Erepsin.
Who were correct ?
(a) Ankur and Aakash
(b) Nishtha and Prakriti
(c) Nishtha and Ankur
(d) Nishtha and Aakash
(b) Nishtha and Prakriti

1. What is the dental formula of a normal human adult?
2, 1, 2, 3 / 2, 1, 2, 3

2. Mention two reflexes which occur when a person chews and swallows food.
1. Increased flow of saliva (watering of mouth) upon chewing.
2. Closing of the windpipe by the epiglottis during swallowing.

3. Match the terms given in column A with those of column B.
Column A: (a) Ptyalin (b) Rennin (c) Erepsin (d) Steapsin (e) Pepsin
Column B: (i) Proteins and peptides (ii) Emulsified fat (iii) Protein (iv) Starch (v) Casein
(a) Ptyalin — (iv) Starch
(b) Rennin — (v) Casein
(c) Erepsin — (i) Proteins and peptides
(d) Steapsin — (ii) Emulsified fat
(e) Pepsin — (iii) Protein

4. Consider the following two statements A & B and select the statements from (i)-(iv) that hold true.
A. Small intestine is shorter than large intestine.
B. Small intestine is wider than large intestine.
Options :
(i) Both the statements are correct.
(ii) Both the statements are wrong.
(iii) Statement A is correct, B is wrong.
(iv) Statement B is correct, A is wrong.
(ii) Both the statements are wrong.

5. Name these :
(a) Two main divisions of the digestive system.
Alimentary canal and digestive glands.
(b) Three digestive glands
Salivary glands, Liver, Pancreas.
(c) Three pairs of salivary glands
Parotid glands, Submandibular glands, Sublingual glands.
(d) Three parts of small intestine
Duodenum, Jejunum, Ileum.
(e) Three parts of large intestine
Caecum, Colon, Rectum.

6. Given below is the "Internal structure of a tooth". Match the structures marked (a) to (e) with their characteristics or functions given in the table.
Example : (e)-5 : The soft connective tissue.
Characteristics/Functions:
1. Covers and fixes the root in position.
2. Hardest substance in the body.
3. The exposed part of the tooth.
4. Forms the bulk of the tooth.
5. The soft connective tissue.
6. The embedded part of the tooth.
(a) Enamel — 2. Hardest substance in the body.
(b) Dentine — 4. Forms the bulk of the tooth.
(c) Cementum — 1. Covers and fixes the root in position.
(d) Root — 6. The embedded part of the tooth.
(f) Crown — 3. The exposed part of the tooth.

7. Choose the odd one out and write the category of the remaining terms :
(a) Pepsin, Trypsin, Steapsin, Erepsin
Odd one: Steapsin. Category: Protein digesting enzymes.
(b) Lactase, Peptidase, Invertase, Maltase
Odd one: Peptidase. Category: Carbohydrate digesting enzymes.
(c) Glucose, Fructose, Galactose, Starch
Odd one: Starch. Category: Simple sugars (monosaccharides).
(d) Ileum, Colon, Duodenum, Jejunum
Odd one: Colon. Category: Parts of the small intestine.
(e) Palate, Crown, Root, Neck
Odd one: Palate. Category: Parts of a tooth.

1. Define the terms :
(a) Digestion
Digestion is the breakdown of naturally occurring foodstuffs into a soluble, diffusible form that can be absorbed through the cell membranes of the gut.
(b) Enzymes
Enzymes are proteins that act as catalysts in the body, which affect the rate of chemical reactions and speed them up.
(c) Peristalsis
Peristalsis is the wave of constrictions caused by the circular muscles of the gut pushing the food along.
(d) Dentition
Dentition refers to the arrangement and types of teeth present in the mouth.
(e) Defaecation
Defaecation is the expulsion of the undigested remains of the food from the alimentary canal.
(f) Assimilation
Assimilation is the conversion of the absorbed digested food into body material.

2. What are the end-products of the digestion of : starch, proteins and fats respectively ?
Starch: Glucose. Proteins: Amino acids. Fats: Fatty acids and glycerol.

3. Write the exact locations of the following :
(a) Liver
Located in the upper right side of the abdomen just below the diaphragm.
(b) Submandibular gland
Lying close to the inner side of the lower jaw on each side.
(c) Pylorus
The opening of the stomach into the intestine (duodenum).
(d) Pancreas
Located behind the stomach.
(e) Caecum
Situated at the junction of the small and large intestines.

4. Write the important roles of the following :
(a) Rectum
Temporarily stores undigested food and wastes before defaecation.
(b) Gastric juice
Kills germs in food via HCl and provides pepsin to digest proteins into peptides.
(c) Epiglottis
Closes the opening of the windpipe during swallowing to prevent food from entering it.
(d) Small intestine
Serves for both the final digestion of food and the absorption of digested nutrients into the blood and lymph.
(e) Tongue
Manipulates food during chewing, helps in swallowing, tasting, cleaning teeth, and speaking.

5. Give reasons/explain :
(a) Only animals require a digestive system and not plants.
Animals consume complex solid food that must be broken down into simple absorbable forms, whereas plants synthesize their own simple, readily usable food.
(b) There are no enzymes to digest vitamins.
Vitamins are already simple, absorbable molecules that do not require further breakdown to be utilized by the body.
(c) Thorough chewing of food in mouth is helpful in digestion.
Chewing cuts and breaks food into smaller bits, increasing the surface area for enzymes to act upon for better and faster digestion.
(d) Bile juice does not contain any enzyme but is still important in digestion.
Bile neutralizes stomach acid to make chyme alkaline for pancreatic enzymes to work, and it emulsifies fats (breaks them into droplets) to increase surface area for enzyme action.
(e) The inner layer of small intestine has a large number of finger-like projections called villi.
Villi enormously increase the inner surface area of the intestine, facilitating maximum absorption of digested food.

6. What is roughage ? Give two examples.
Roughage is the undigestible solid portion of food (like cellulose from plant material) that provides bulk to the faeces. Examples: Green leafy vegetables and fruit skins.

7. Mention two ways in which the ileum of a mammal is adapted for the absorption of digested food.
1. It is very long, providing more surface area.
2. It has a large number of finger-like projections called villi which further immensely increase the surface area for absorption.

8. The stomach secretes gastric juice, which contains hydrochloric acid. What is its function ?
Hydrochloric acid kills any germs which may have entered along with the food and it activates inactive pepsinogen into active pepsin to act on proteins.

1. What are the main characteristics of an enzyme ?
1. It is a protein and is destroyed by heating.
2. It is specific, acting only on one kind of substance (substrate).
3. It always forms the same end-product(s).
4. It only affects the rate of a chemical reaction.
5. It acts like a catalyst and can be used again and again.
6. It acts best at a particular pH (degree of acidity or alkalinity).
7. It functions best within a narrow temperature range (usually 35°C to 40°C), called the optimum temperature.

2. Why is the small intestine the most important organ of the digestive system ?
The small intestine is the most important organ because it serves a dual function: it is the site where final digestion of all major food components occurs (via bile, pancreatic, and intestinal juices), and it is the primary site for the absorption of these digested nutrients into the bloodstream and lymphatic system through its villi.

3. How is the liver an important organ in our body ?
The liver is crucial because it produces bile to aid fat digestion, regulates blood sugar levels by storing excess glucose as glycogen, controls amino acid levels via deamination, synthesizes foetal red blood cells, stores essential minerals (iron, copper) and vitamins (A & D), detoxifies drugs and alcohol, and produces important blood clotting factors like fibrinogen and prothrombin as well as the anticoagulant heparin.

4. List the enzymes and their action on food in the stomach and intestine.
In the Stomach:
- Pepsin: Converts proteins into peptides.
- Rennin: Converts soluble milk protein (casein) into insoluble paracasein.
In the Intestine:
- Amylopsin (Pancreas): Converts leftover starch into maltose.
- Trypsin (Pancreas): Converts proteins and polypeptides into smaller peptides and amino acids.
- Steapsin (Pancreas): Converts emulsified fats into fatty acids and glycerol.
- Erepsin (Intestinal juice): Converts peptides into amino acids.
- Maltase (Intestinal juice): Converts maltose into glucose.
- Sucrase (Intestinal juice): Converts sucrose into glucose and fructose.
- Lactase (Intestinal juice): Converts lactose into glucose and galactose.
- Intestinal Lipase (Intestinal juice): Converts fats into fatty acids and glycerol.

5. You have been supplied with a sample of food. How will you perform tests for the presence of starch and proteins in it ?
Test for Starch: Shake a little of the food sample in a test tube with water and boil it. Once cooled, add a few drops of iodine solution. If the solution turns blue-black, starch is present.
Test for Protein: Place a piece of the food in a test tube. Add a few drops of concentrated nitric acid and heat gently. The color changes from white to yellow. Cool the test tube and add ammonium hydroxide. If the color changes from yellow to orange, protein is present.

1. Draw a labelled diagram to show the internal structure of a mammalian tooth with two roots.
[Students are required to draw a premolar or lower molar showing the crown, neck, root, enamel, dentine, pulp cavity, gums, and cementum, identical to Fig 12.4 B in the textbook.]

2. Complete the following table by filling in the blanks 1 to 8.
1 - Stomach
2 - Proteins
3 - Peptides
4 - Ptyalin (Salivary amylase)
5 - Starch
6 - Ileum (or Small intestine)
7 - Maltase
8 - Glucose

3. Study the diagram given alongside and then answer the questions that follow :
(a) Name the parts labelled 1, 2, 3, 4, 5 and 6.
1. Enamel, 2. Dentine, 3. Pulp cavity, 4. Gum, 5. Crown, 6. Cementum (or Periodontal membrane).
(b) Identify the tooth and give a reason to support your answer.
It is a Canine tooth. Reason: It has a single root and a conical, pointed crown designed for holding and tearing.
(c) Describe the structure of the part labelled '3'.
The pulp is the soft connective tissue contained in the central space of the tooth, consisting of blood capillaries, lymph vessels, and nerve fibres.
(d) Give the total number of the type of tooth mentioned in 'b' above, in the mouth of an adult and state its function.
Total number: 4 (2 in upper jaw, 2 in lower jaw). Function: Holding and tearing food.

4. Study the following dental formula and then answer the questions that follow :
i 3/4 c 0/0 pm 0/1 m 1/1
(a) What is the total number of teeth in the (i) upper jaw and (ii) lower jaw ?
(i) Upper jaw = (3+0+0+1) × 2 = 8 teeth. (ii) Lower jaw = (4+0+1+1) × 2 = 12 teeth.
(b) State the total number of teeth present in the dentition.
Total number = 8 + 12 = 20 teeth.
(c) Give the dental formula of an adult human being.
2, 1, 2, 3 / 2, 1, 2, 3

5. The figures (A, B, C and D) shown below represent different kinds of teeth in humans. Study the figures and answer the following questions :
(a) What kind of teeth do A, B, C and D represent ?
A: Incisor, B: Canine, C: Premolar, D: Molar.
(b) Write one structural feature/shape of each.
A: Broad and sharp like a chisel. B: Conical and sharply pointed. C: Has two hill-like projections (cusps). D: Larger surface than premolars with multiple roots.
(c) Mention the number of teeth of each kind in one jaw with their specific position.
Incisors: 4, placed in the centre front. Canines: 2, one on either side of the incisors. Premolars: 4, two on each side next to the canines. Molars: 6, the last three teeth on each side.
(d) Name two minerals present in teeth.
Calcium and Phosphorus.
(e) What do you mean by 'Wisdom tooth' ?
The wisdom tooth is the last molar on each side in each jaw, so named because it appears last at an age of about 17-20 years when the human body is reaching maturity.

6. Draw a neat diagram of the "Microscopic structure of an intestinal villus" and label the parts given below :
(i) Epithelium (ii) Capillaries (iii) Lacteals
[Students are expected to draw a structure similar to Fig 12.6, showing an elongated projection covered by single-celled epithelium, containing a central lacteal surrounded by a network of capillaries.]
Answer the following questions :
(a) What is the advantage of having a large number of villi on the inner surface of small intestine ?
They enormously increase the inner surface area of the intestines to facilitate the absorption of digested food.
(b) Write the important role of lacteals.
Lacteals absorb fatty acids and glycerol to enter the lymphatic system.
(c) Name the juice secreted from the glandular cells of small intestine.
Intestinal juice.
(d) Name the specific secretions of : (1) Salivary gland (2) Stomach (3) Liver (4) Pancreas
(1) Saliva (2) Gastric juice (3) Bile (4) Pancreatic juice.

7. Vedika observed the following structure in a biology chart showing the digestive system.
(a) Name the structure which stores bile juice.
Gall Bladder.
(b) Mention the gland which secretes bile juice.
Liver.
(c) What are the three enzymes found in the pancreatic juice which can act over proteins, carbohydrates and emulsified fats?
Trypsin (acts on proteins), Amylopsin (acts on carbohydrates/starch), and Steapsin (acts on emulsified fats).

(i) Assertion (A) : The last molar on each side of both the jaws is called the wisdom tooth as it is responsible for the intelligence of a person.
Reason (R) : The wisdom teeth are so called because they appear at an age of about 17-20 years when the human body is reaching maturity.
(d) A is false but R is true.

(ii) Assertion (A) : Dentine forms the bulk of the tooth.
Reason (R) : Dentine is a bone-like structure which covers and fixes the root of a tooth in position.
(c) A is true but R is false.

(iii) Assertion (A) : Both ptyalin and amylopsin are the same with respect to their enzymatic activity.
Reason (R) : Both of these enzymes convert starch into maltose.
(a) Both A and R are true and R is the correct explanation of A.

(iv) Assertion (A) : Pylorus is the structure which prevents the entry of food from the small intestine to the stomach.
Reason (R) : Pylorus has a ring of muscles to keep the opening of the stomach closed like a valve. It is located at the back end of the stomach.
(a) Both A and R are true and R is the correct explanation of A.

(v) Assertion (A) : Bile juice is produced in the liver and is stored in the gall bladder.
Reason (R) : Bile juice is poured in duodenum through the common bile duct. It converts the acidic pH of the food to alkaline and enables the pancreatic enzymes to act.
(b) Both A and R are true but R is not the correct explanation of A.

(vi) Assertion (A) : The length of the small intestine is shorter than the large intestine.
Reason (R) : Small intestine is highly coiled and folded in the abdomen.
(d) A is false but R is true.

1. During lunch break, Akshay bit into a slice of cake his friend brought from home. Almost instantly, his mouth filled with a fluid, even though he hadn't started chewing yet. Later he learned that there is some gland in the buccal cavity which responds not just to food in the mouth but also to the sight and taste of tangy or appetizing foods.
(a) Name the fluid secreted in the mouth and the gland which has secreted it.
The fluid is Saliva, secreted by the Salivary glands.
(b) Name the three pairs of above mentioned gland.
Parotid glands, Submandibular glands, and Sublingual glands.
(c) Mention any three constituents of the fluid secreted in the mouth.
Water, salts, mucus (and the enzyme salivary amylase/ptyalin).
(d) Does this fluid help in digestion ? If yes, write its enzymatic equation with the specific substrate.
Yes. Starch + Ptyalin (Salivary amylase) → Maltose.
(e) Write two more functions of the fluid answered in (a) above other than digestion.
1. Moistens and lubricates the inner lining of the oral cavity and food to facilitate speaking and swallowing.
2. Cleans the mouth and tends to destroy germs to prevent tooth decay.

Write the correct word for the items (i) to (viii).
(i) A predator:
GRIET
TIGER

(ii) Deficiency of Folic acid (B9) produces:
MIAAEN
ANAEMIA

(iii) A digestive enzyme:
ENPISP
PEPSIN

(iv) A part of tooth:
TEEDINN
DENTINE

(v) Fatty acids are absorbed into :
TACLELAS
LACTEALS

(vi) Maltase acts on:
LESOMAT
MALTOSE

(vii) Excess amino acids are broken down in:
RIVEL
LIVER

(viii) An enzmye which digests starch :
YEALMAS
AMYLASE