Digestive System

Progress Check 1

Question 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.

Answer

Pharynx → Oesophagus → Stomach → Small intestine → Large intestine

Question 2

Give the technical names for the following types of teeth in humans (on each side, in each jaw)

1. The three last grinders.
2. The pointed tooth for holding and tearing.
3. The broad sharp cutting teeth.
4. The two temporary (deciduous) grinding teeth.

Answer

1. Molars
2. Canine
3. Incisors
4. Premolar

Question 3

Name the following parts of a tooth :

1. Part exposed above the gum.
2. The hard substance making the covering of the tooth.
3. The soft connective tissue contained in the central space of the tooth.
4. Bone-like structure fixing the root in position.
5. Slight constriction between the root and the crown.

Answer

1. Crown
2. Enamel
3. Pulp
4. Cementum
5. Neck

Progress Check 2

Question 1

Mention if the following statements are true or false:

1. Saliva moistens and lubricates food.
2. Saliva contains a protein-digesting enzyme.
3. Saliva tends to destroy germs in the mouth.
4. Peristalsis occurs through all regions of the gut.
5. The food in stomach stays for about 10 hours.
6. Gastric juice is alkaline.
7. Gastric juice contains pepsinogen.

Answer

1. True
2. False
   Corrected Statement — Saliva contains a starch-digesting enzyme.
3. True
4. True
5. True
6. False
   Corrected Statement — Gastric juice is acidic.
7. False
   Corrected Statement — Gastric juice contains pepsin and renin.

Question 2

Name the three salivary glands.

Answer

1. Parotid glands
2. Sub-mandibular glands
3. Sublingual glands

Progress Check 3

Question 1

Mention if the following statements are true (T) or false (F)

1. Intestinal villi have a lymph vessel called lacteal.
2. Intestine is narrow for fast movement of food.
3. Large intestine secretes no enzymes.
4. Bile neutralizes the acid content of the food received from the stomach.
5. Pancreatic juice has enzymes to digest all the major components of food.
6. The anus is surrounded by circular muscles.

Answer

1. True
2. False
   Corrected Statement — Intestine is narrow for slow movement of food.
3. True
4. True
5. True
6. True

Question 2

Name the following :

1. The three subdivisions of the small intestine.
2. The three subdivisions of the large intestine.

Answer

1. Duodenum, Jejunum, Ileum
2. Caecum, Colon, Rectum

Question 3

Name the enzyme which digests :

1. starch in the mouth
2. fats in the ileum
3. protein in duodenum
4. sucrose in the ileum

Answer

1. Salivary amylase or Ptyalin
2. Intestinal lipase
3. Trypsin
4. Sucrase/invertase

Question 4

What are the end-products of digestion of :

1. Proteins
2. Fats
3. Starch
4. Sucrose

Answer

1. Amino acid
2. Fatty acid and Glycerol
3. Maltose
4. Glucose and Fructose

Progress Check 4

Question 1

Fill in the blanks.

1. Liver stores glucose as ............... .
2. Liver produces ............... only in embryo.
3. Urea is produced in ............... by the deamination of extra............... .
4. For testing the action of saliva on starch, the material has to be kept at a temperature of about ............... °C.

Answer

1. Liver stores glucose as glycogen .
2. Liver produces RBC only in embryo.
3. Urea is produced in liver by the deamination of extra amino acid .
4. For testing the action of saliva on starch, the material has to be kept at a temperature of about 38°C.

Progress Check 5

Question 1

Mention the constituent of food if the end result of the test shows :

1. White to yellow and yellow to orange colour.
2. Turning blue-black after adding iodine solution.
3. Blue green to deep red with appearance of precipitate.
4. Ash that does not burn after continued heating.

Answer

1. Protein
2. Starch
3. Glucose
4. Minerals

Multiple Choice Type

Question 1

Pylorous is an opening from

1. oesophagus into stomach
2. mouth cavity into oesophagus
3. stomach into intestine
4. intestine into rectum

Answer

stomach into intestine

Reason — The opening of the stomach into intestine is called pylorus. It has a ring of muscles (sphincter).

Question 2

Gastric juice contains

1. HCl and pepsin
2. pepsin and trypsin
3. trypsin and HCl
4. amylopsin and pepsin

Answer

HCl and pepsin

Reason — Gastric juice is acidic and contains HCl and pepsin.

Question 3

The water from the digested food is mainly absorbed by

1. stomach
2. duodenum
3. colon
4. rectum

Answer

colon

Reason — Colon absorbs most of the water and left-over nutrients.

Question 4

Which one of the following pairs of types of teeth perform one common function as stated against it?

1. Incisors, canines — Holding
2. Canines, premolars — Tearing
3. Premolars, molars — Grinding
4. Molars, incisors — Tearing

Answer

Premolars, molars — Grinding

Reason — Premolars and molars carry out grinding of food.

Question 5

The hardest substance in the human body is :

1. Bone
2. Enamel
3. Cement
4. Dentine

Answer

Enamel

Reason — Enamel, which forms outer most covering of teeth is hardest substance of the human body.

Question 6

Which of the following teeth is bicuspid ?

1. Molars
2. Incisors
3. Premolars
4. Canines

Answer

Premolars

Reason — Premolar has two hill-like projections or cusps on its surface.

Question 7

The temperature range within which enzymes can act best is :

1. 20° to 30°C
2. 35° to 40°C
3. 40° to 45°C
4. 35° to 50°C

Answer

35° to 40°C

Reason — 35° to 40°C is the optimum temperature range when enzymes act best.

Question 8

Heterodont dentition is found in :

1. Humans
2. Snake
3. Frog
4. Lizards

Answer

Humans

Reason — Mammals have teeth of different shapes.

Question 9

Which of the following enzymes is not found in pancreatic juice ?

1. Sucrase
2. Trypsinogen
3. Amylopsin
4. Steapsin

Answer

Sucrase

Reason — Sucrase is present in intestinal juice.

Question 10

The process of conversion of excess glucose into glycogen is termed as :

1. Glycolysis
2. Glycogenesis
3. Glycogenolysis
4. Defaecation

Answer

Glycogenesis

Reason — The excess glucose present in our body is converted into glycogen by liver.

Very Short Answer Type

Question 1

What is the dental formula of a normal human adult?

Answer

Human adult: $\dfrac{2, 1, 2, 3}{2, 1, 2, 3} = 32$ (permanent teeth with 4 wisdom teeth added)

Question 2

Mention two reflexes which occur when a person chews and swallows food.

Answer

The two reflexes which occur when a person chews and swallows food are-

1. Reflex when a person chews — Secretion of saliva.
2. Reflex when a person swallows — The tongue presses upward and back against the roof (palate) of the mouth and this forces the bolus (the ball of chewed food ) into the throat or the pharynx.

Question 3

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.

Answer

The statement that holds true is:

(ii) Both the statements are wrong.

Reason — Small intestine is longer than the large intestine. It is about 7 meters longer while large intestine is about 1.5 meters long. Large intestine is wider than the small intestine.

Question 4

Match the terms given in column A with those of column B.

Answer

Question 5

Name these:

1. Two main divisions of the digestive system
2. Three digestive glands
3. Three pairs of salivary glands
4. Three parts small intestine
5. Three parts of large intestine

Answer

1. Alimentary canal and digestive glands.
2. Salivary gland, liver and pancreas.
3. Parotid glands, sub-mandibular glands and sublingual glands.
4. Duodenum, Jejunum, Ileum.
5. Caecum, Colon, Rectum.

Question 6

Choose the odd one out and write the category of the remaining terms :

1. Pepsin, Trypsin, Steapsin, Erepsin
2. Lactase, Peptidase, Invertase, Maltase
3. Glucose, Fructose, Galactose, Starch
4. Ileum, Colon, Duodenum, Jejunum
5. Palate, Crown, Root, Neck

Answer

1. Steapsin is odd one out. Remaining terms (Pepsin, Trypsin and Erepsin) are protein digesting enzymes.
2. Peptidase is odd one out. Lactase, Invertase and Maltase are sugar digesting enzymes.
3. Starch is odd one out. Glucose, Fructose and Galactose are simple sugar.
4. Colon is odd one out. Ileum, Duodenum and Jejunum are parts of small intestine.
5. Palate is odd one out. Crown, Root and Neck are parts of teeth.

Short Answer Type

Question 1

Define the following terms:

(a) Digestion

(b) Enzymes

(c) Peristalsis

(d) Dentition

(e) Defaecation

(f) Assimilation

Answer

(a) Digestion — Digestion is any change which makes the food soluble and of such chemical nature that it can be absorbed readily through living membranes.

(b) Enzymes — An enzyme is a protein that acts on a specific substance to form a specific end product. It best acts at a particular temperature and pH.

(c) Peristalsis — It is defined as the rhythmic contraction and relaxation of the muscles of the alimentary canal which pushes the food along the gut.

(d) Dentition — The arrangement of teeth in a particular species is called dentition.

(e) Defaecation — The expulsion of undigested remains of food from the alimentary canal is called defaecation.

(f) Assimilation — It is the conversion of the absorbed digested food into body material.

Question 2

What are the end-products of the digestion of: starch, proteins and fats respectively?

Answer

The end products are as follows:

Starch — Maltose
Proteins — Small peptides and amino acids
Fats — Glycerol and fatty acids

Question 3

Write the exact locations of the following :

(a) Liver

(b) Sub-mandibular gland

(c) Pylorus

(d) Pancreas

(e) Caecum

Answer

(a) located in upper right side of abdomen just below the diaphragm.

(b) below the tongue.

(c) between stomach and small intestine.

(d) located behind the stomach.

(e) at junction of large and small intestine.

Question 4

Write the important roles of the following :

(a) Rectum

(b) Gastric juice

(c) Epiglottis

(d) Small intestine

(e) Tongue

Answer

(a) Rectum temporarily stores undigested food and wastes, to be defaecated through the anus.

(b) Gastric juice plays two key roles (i) it kills any germs which may have entered along with the food (ii) it activates pepsinogen to act on proteins.

(c) Epiglottis closes the opening of wind pipe.

(d) Most of the digestion and absorption of nutrition occur in small intestine.

(e) Tongue helps in mixing of food in buccal cavity and pushes it through pharynx.

Question 5

Give reasons/explain :

(a) Only animals require a digestive system and not plants.

(b) There are no enzymes to digest vitamins.

(c) Thorough chewing of food in mouth is helpful in digestion.

(d) Bile juice does not contain any enzyme but is still important in digestion.

(e) The inner layer of small intestine has a large number of finger-like projections called villi.

Answer

(a) Animals are heterotrophs. They obtain their nutrients by consuming organic matter, such as other organisms or plant material. Hence, they need a digestive system to break down complex molecules, such as proteins, carbohydrates, and lipids, into smaller, absorbable forms. In contrast, plants are autotrophs, capable of synthesizing their own food through photosynthesis. Hence, they don't require a digestive system.

(b) Vitamins do not need digestion. They are absorbed directly through the intestine wall.

(c) Chewing of food breaks the food into small particles which helps in easy digestion.

(d) Bile contains a lot of sodium bicarbonate which neutralises the acid content of the food received from the stomach and makes it alkaline so that pancreatic and intestinal enzymes can act on it.

(e) The villi enormously increase the inner surface area of the intestines which facilitates the absorption of digested food.

Question 6

What is roughage? Give two examples.

Answer

Roughage is the undigestible portion of the diet. It is a dietary fibre that majorly contains cellulose. Examples – Green leafy vegetables, fruits, beans, nuts.

Question 7

Mention two ways in which the ileum of a mammal is adapted for the absorption of digested food.

Answer

The two ways in which the ileum of mammals is adapted for the absorption of digested food are:

1. Very long to provide much more surface area for absorption.
2. Ileum has numerous villi which further causes the surface area to increase thereby increasing the quantity of absorption of digested food.

Question 8

The stomach secretes gastric juice, which contains hydrochloric acid. What is its function?

Answer

Hydrochloric acid performs the following functions in the stomach-

1. It kills any germs which may have entered along with the food.
2. It activates pepsin to act on proteins. Pepsin digests proteins into peptides.

Long Answer Type

Question 1

What are the main characteristics of an enzyme?

Answer

Main characteristics of enzymes are-

1. It is a protein and is, therefore, destroyed by heating.
2. It acts only on one kind of substance called the substrate i.e. it is specific.
3. It always forms the same end-product(s) from the substrate.
4. It only affects the rate of a chemical reaction and always speeds up the reaction.
5. Like a catalyst, it can be used again and again.
6. It acts best only at a particular pH,i.e. at a particular degree of acidity or alkalinity.
7. It acts best within a narrow temperature range, usually between 35°and 40°C which is also called the optimum temperature.

Question 2

Why is the small intestine the most important organ of the digestive system?

Answer

The small intestine serves two important functions of digestion and absorption. In the duodenum, it receives two digestive juices:

1. The bile
2. The pancreatic juice

Both the juices virtually complete the process of digestion of proteins, starch, carbohydrates etc. Once the food is broken down, the small intestine is responsible to absorb simple particles such as amino acids, glucose etc.

Question 3

How is the liver an important organ in our body?

Answer

The liver is the largest gland of the body and it performs the following functions:

1. Controls amino acid levels
2. Produces foetal red blood cells
3. Produces heparin and fibrinogen
4. Checks blood volume
5. Destructs dead red blood cells
6. Detoxifies
7. Produces bile
8. Generates heat
9. Controls blood sugar levels
10. Storage of minerals and vitamins
11. Excretes metallic and toxic substances

Question 4

List the enzymes and their action on food in the stomach and intestine.

Answer

The table below shows the different regions, enzymes and the action of the enzymes on the food -

Question 5

You have been supplied with a sample of food. How will you perform tests for the presence of starch and proteins in it?

Answer

The following tests can be carried out:

Test for starch:

Aim — To detect the presence of starch in the sample

Procedure and Inference —

1. Add some starch powder to a test tube containing water, shake well. Boil well to make a solution.
2. Add some drops of iodine solutions when the solution cools down.
3. Iodine solution can be prepared by dissolving 1g iodine with 1g potassium iodide in 100ml of distilled water, dilute this solution before using.
4. The solution in the test tube would turn blur-black indicating the presence of starch.

Test for proteins:

Aim — To detect the presence of proteins in the given sample

Procedure and Inference—

1. In a test tube add a few pieces of the sample (hard-boiled egg)
2. Add a few drops of dilute nitric acid so as to seal the food
3. Gently heat the test tube, rinsing off the acid with water, to this add ammonium hydroxide
4. Observe the changes – from the initial white, color changes to yellow
5. After adding ammonium hydroxide – the color changes from yellow to orange.

Structured / Application / Skill Type

Question 1

Draw a labelled diagram to show the internal structure of a mammalian tooth with two roots.

Answer

Below labelled diagram shows the internal structure of a mammalian tooth with two roots :

Question 2

Complete the following table by filling in the blanks 1 to 8.

Answer

1 – Stomach

2 – Proteins

3 – Polypeptides

4 – Amylase

5 – Starch

6 – Ileum

7 – Maltase

8 – Glucose

Question 3

Study the diagram given below and then answer the questions that follow:

(a) Name the parts labeled 1, 2, 3, 4, 5 and 6.

(b) Identify the tooth and give a reason to support your answer.

(c) Describe the structure of the part labeled '3'.

(d) Give the total number of the type of tooth mentioned in '1' above, in the mouth of an adult and state its function.

Answer

(a) The parts are-

• 1 → Enamel
• 2 → Dentine
• 3 → Pulp
• 4 → Gum
• 5 → Crown
• 6 → Cement

(b) The type of teeth shown in the given figure has only one root. Hence it is a canine or incisor that is used to bite or pierce.

(c) The part labelled '3'(Pulp) is a soft connective tissue present in the pulp cavity of the tooth. It consists of blood capillaries, lymph vessels and nerve fibres. From the crown of the tooth, the pulp opens through the pulp cavity at the base of the root.

(d) The type of teeth mentioned in the figure and its function are as follows:

Question 4

Study the following dental formula and then answer the questions that follow:

$i\dfrac{3}{4} \enspace c\dfrac{0}{0} \enspace pm\dfrac{0}{1} \enspace m\dfrac{1}{1}$

(a) What is the total number of teeth in the (i) upper jaw and (ii) lower jaw?

(b) State the total number of teeth present in the dentition.

(c) Give the dental formula of an adult human being.

Answer

(a) The total number of teeth in the upper jaw are 8 and lower jaw are 12.

(b) The total number of teeth present in the given dentition are 20 teeth.

(c) The dental formula of an adult is as follows:

Human adult: $\dfrac{2, 1, 2, 3}{2, 1, 2, 3} = 32$ (permanent teeth with 4 wisdom teeth added)

Question 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 ?

(b) Write one structural feature/shape of each.

(c) Mention the number of teeth of each kind in one jaw with their specific position.

(d) Name two minerals present in teeth.

(e) What do you mean by 'Wisdom tooth'?

Answer

(a)

• A → Incisor
• B → Canine
• C → Premolar
• D → Molar

(b)

• A → Broad and sharp
• B → Conical and sharply pointed
• C → Two hill-like projections(bicuspid)
• D → Large grinding surface

(c)

• A → Four, centre of each jaw
• B → Two, one on each side of incisor
• C → Four, two on side of each canine
• D → Six, three on each side

(d) Calcium and phosphorous.

(e) Last molar on each side of jaw is called wisdom teath.

Question 6

Draw a neat diagram of the "Microscopic Structure of an intestinal villus" and label the parts given below :

1. Epithelium
2. Capillaries
3. Lacteals

Answer the following questions :

(a) What is the advantage of having a large number of villi on the inner surface of small intestine ?

(b) Write the important role of lacteals.

(c) Name the juice secreted from the glandular cells of small intestine.

(d) Name the specific secretions of:

1. Salivary gland
2. Stomach
3. Liver
4. Pancreas

Answer

Below is the labelled diagram of the "Microscopic Structure of an intestinal villus":

(a) A large number of villi enormously increase the inner surface area of the small intestine which facilitates the absorption of digested food.

(b) The fatty acids and glycerol are absorbed into the lacteals to enter the lymphatic system which forms a network all over the body to ultimately empty its contents into the blood stream.

(c) Intestinal juice

(d)

1. Salivary gland - Saliva (amylase)
2. Stomach - Gastric juice
3. Liver - Bile
4. Pancreas - Pancreatic juice

Question 7

Write the correct word for the items (i) to (viii).

(i) A predator:

$\boxed{\text{GRIET}} \quad$ ...............

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

$\boxed{\text{MIAAAEN}} \quad$ ...............

(iii) A digestive enzyme:

$\boxed{\text{ENPISP}} \quad$ ...............

(iv) A part of tooth:

$\boxed{\text{TEEDINN}} \quad$ ...............

(v) Fatty acids are absorbed into:

$\boxed{\text{TACLELAS}} \quad$ ...............

(vi) Maltase acts on:

$\boxed{\text{LESOMAT}} \quad$ ...............

(vii) Excess amino acids are broken down in:

$\boxed{\text{RIVEL}} \quad$ ...............

(viii) An enzyme which digest starch:

$\boxed{\text{YEALMAS}} \quad$ ...............

Answer

(i) A predator:

$\boxed{\text{GRIET}} \quad$ TIGER

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

$\boxed{\text{MIAAAEN}} \quad$ ANAEMIA

(iii) A digestive enzyme:

$\boxed{\text{ENPISP}} \quad$ PEPSIN

(iv) A part of tooth:

$\boxed{\text{TEEDINN}} \quad$ DENTINE

(v) Fatty acids are absorbed into:

$\boxed{\text{TACLELAS}} \quad$ LACTEALS

(vi) Maltase acts on:

$\boxed{\text{LESOMAT}} \quad$ MALTOSE

(vii) Excess amino acids are broken down in:

$\boxed{\text{RIVEL}} \quad$ LIVER

(viii) An enzyme which digest starch:

$\boxed{\text{YEALMAS}} \quad$ AMYLASE