Human Body : The Digestive System
Exercise
AECTION I
A. Name the following.
1. The tubular structure extending from mouth to stomach.
= Oesophagus;
2. The enzyme that acts on starch in mouth.
= Amylase;
3. The largest gland in the body.
= Liver;
4. Finger-like projections on the inner walls of small intestine.
= Villi;
5. The part of small intestine that receives the bile.
= Duodenum;
B. Choose the correct option.
1. The digestion of food begins here.
a. Mouth. [ ]
b. Stomach. [ ]
c. Oesophagus. [ ]
d. Intestine. [✓]
2. The teeth used for biting fruits such as guava and apple.
a. Incisor. [ ]
b. Canine. [ ]
c. Molar. [ ]
d. Premolar. [✓]
3. The semi-digested food in the mouth ready to be swallowed.
a. Chime. [ ]
b. Chime. [ ]
c. Soup. [ ]
d. Bolus. [✓]
4. The organ that secretes bile.
a. Stomach. [ ]
b. Gall bladder. [ ]
c. Liver. [✓]
d. Small intestine. [ ]
5. The process of elimination of undigested food waste from the body.
a. Egestion. [✓]
b. Ingestion. [ ]
c. Excretion. [ ]
d. Absorption. [ ]
C. Choose the correct option to fill in the blanks.
1. A wave of muscular contraction and relaxation that occurs throughout the length of alimentary canal is called peristalsis(peristalsis/phagocytosis).
2. The enzymes pepsin converts proteins in stomach into proteoses( proteoses/amino acids).
3. Pharynx(Pharynx/Epiglottis) is a common passage for food and air.
4. Pancreatic enzymes work best in an alkaline(acidic/alkaline) medium.
5. The part of alimentary canal that absorbs digested nutrients is small intestine(small intestine/large intestine).
D. Choose the odd term in each of the following sets and write down the category to which the other three belong.
Example: eye, nose, heart, ear; Odd term: Heart;
Category: Sense organs;
1. Mouth, Stomach, Intestine, Pancreas.
= Odd term: Pancreas;
Category: Digestive organs;
2. Duodenum, Caecum, Jejunum, Ileum.
= Odd term: Caecum;
Category: Parts of small intestine;
3. Pancreas, Liver, Salivary gland, Stomach.
= Odd term: Stomach;
Category: Digestive glands;
4. Teeth, Oesophagus, Tongue, Salivary gland.
= Odd term: Oesophagus;
Category: Located in mouth;
5. Ingestion, Egestion, Respiration, Digestion.
= Odd term: Respiration;
Category: Food digestion process;
E. Write T for true and F for false. Correct the false statement by changing the last word/s.
1. Semi-digested food in the stomach is converted into chyme by the action of gastric juice. [T]
2. The final product of fat digestion is fatty acid and alcohol. [F]
= The final product of fat digestion is fatty acid and glycerol.
3. Assimilation is completed in the small intestine. [F]
= Assimilation is completed in the liver.
4. Villi is present in the large intestine. [F]
= Villi is present in the small intestine.
5. Hydrochloric acid is secreted in the stomach. [T]
F. State the main function of the following.
1. Salivary gland.
= Salivary glands secret saliva, a watery fluid, containing the enzymes, salivary amylase. This enzyme helps in the digestion of carbohydrates, mainly starch.
2. Molar.
= Chewing food, crushing and grinding food.
3. Lipase.
= Digest fat.
4. Liver.
= It secrets a greenish-yellow fluid called bile. Bile is temporarily stored in a small pouch, located below the liver, called gall bladder.
5. Rectum.
= The rectum opens to the exterior through the anus. Anus expels the undigested food waste called faeces to the exterior.
G. Give the exact location of the following.
1. Pharynx.
= It is located at the posterior of the oral cavity.
2. Stomach.
= It at located on the left side of the abdominal cavity, at the end of the oesophagus.
3. Salivary gland.
= In the oral cavity, there are three pairs of salivary glands located beneath the ears, along the sides and below the lower jaw.
4. Small intestine.
= It is a narrow and extremely coiled tube present behind the stomach.
5. Colon.
= Colon is the largest part of the large intestine.
SECTION II
H. Give reasons for the following.
1. Digestion of food begins in the mouth.
= Digestion of food begins in the mouth because saliva, secreted by the salivary glands in the mouth, contains an enzyme called salivary amylase. It breaks down the starch present into smaller molecules of sugar.
2. No digestion takes place in the oesophagus.
= No digestion takes place in the oesophagus because there is no glands to secrete digestive juice. It has longitudinal and circular muscles in its walls that help in pushing the food down into the stomach.
3. It is important for the hydrochloric acid to be released in the stomach.
= It is important for the hydrochloric acid to be released in the stomach because hydrochloric acid creates and acidic medium in the stomach, and kills the bacteria that enter along with food.
4. The small intestine is thrown into finger like projections.
= The small intestine is thrown into finger like projections to increase the surface area for absorption of digested nutrients.
5. We should not eat late night.
= We should not eat late night because long gaps between lunch and dinner make us eat more during the dinner. This shortens the sleep duration and upsets the body's natural clock. Over a period of time, it can cause indigestion, hyperacidity, weight gain, and an increased risk of obesity.
I. Define the following.
1. Nutrition.
= Nutrition is the process of obtaining food and utilising it for growth, repair of the body, and for obtaining energy.
2. Digestion.
= Digestion is the process of breaking down the food so that it can be absorbed in the body.
3. Peristalsis.
= Peristalsis is a wave of coordinated muscular contractions and relaxations that occur throughout the length of the alimentary canal.
4. Assimilation.
= Digested food molecules that have been absorbed through the villi are transported through the blood vessels to the liver, and finally, all the body cells. Here, they are utilized for building new protoplasm for producing energy and for repair. This process is called assimilation.
5. Chyme.
= Stomach muscles churn the bolus with gastric juices to form a pulpy fluid called chyme.
J. Differentiate between the following.
1. Nutrients and nutrition.
= The food we eat provides us with substances essential for the growth and development of our body. These nourish our body and are called nutrients.
Nutrition is the process of obtaining food and utilising it for growth, repair of the body, and for obtaining energy.
2. Incisor and canine.
= Incisor is chisel-like teeth for biting food. But canine is pointed, sharp teeth for tearing food.
3. Ingestion and egestion.
= Ingestion is the process of taking in of food into the mouth. But egestion is the expulsion of undigested wastes out of the body.
4. Salivary amylase and pepsin.
= Salivary amylase is released in mouth and it turns starch into maltose. But pepsin is released in stomach and it turn proteins into proteoses and peptones.
5. Bolus and chyme.
= After thorough chewing and mixing with saliva, a semi-solid mass of food, called bolus, is formed.
Stomas muscles churn the bolus with gastric juices to form a pulpy fluid called chyme, which then passes into the small intestine.
K. Short answer questions.
1. List the parts of alimentary canal in correct sequence.
= The parts of alimentary canal in correct sequence is - pharynx, oesophagus, stomach, small intestine, large intestine, and anus.
2. What is the role of saliva in digestion.
= Saliva helps in the digestion of carbohydrates, mainly starch. It breaks down the starch present into smaller molecules of sugar (maltose).
3. What are enzymes and how do they function?
= Enzymes are chemical substances that work as catalysts. Catalysts are substances that speed up a chemical reaction.
Digestive enzymes break down carbohydrates, fats, and proteins into smaller and simpler components so that they are easier to absorb by the body cells.
4. Name the parts of small intestine and large intestine.
= The parts of small intestine are - duodenum, jejunum and ileum.
The parts of large intestine are - caecum, colon, and rectum.
5. List the end products of carbohydrate, protein, and fat digestion.
= The end product of carbohydrate is maltose.
The end product of protein is peptides.
The end product of fat is fatty acid and glycerol.
6. Give any two functions of bile.
= Two functions of bile are -
i) Bile emulsifies fats by breaking down large fat globules into smaller droplets.
ii) Bile also provides an alkaline medium in the duodenum.
7. What is indigestion?
= Indigestion is a condition of nausea, pain, or discomfort in the upper abdominal area due to inability to digest the food properly.
L. Long answer questions.
1. Name the nutrients present in food and state their functions.
= There are five types of food present in food - carbohydrates, proteins, fats, vitamins and minerals.
Carbohydrates and fats are the energy-giving foods.
Proteins are the body building food needed for the body's growth and repair of tissues.
Vitamins and minerals are called protective foods. They help to maintain good health and protect us from diseases.
A lack of nutrients in our food over a large period can cause various kinds of deficiency diseases.
2. Give an account of structure, function, and the number of each type of teeth found in an adult human.
= An adult human being has 32 permanent teeth. These are of four different types: incisors, canines, premolars, and molars.
|
Type of tooth |
Structure |
Function |
Number in each jaw |
|---|---|---|---|
|
Incisor |
Chisel-like |
Biting |
4 |
|
Canine |
Pointed, Sharp |
Tearing |
2 |
|
Premolar |
Flat surface, wide and uneven |
Chewing and grinding |
4 |
|
Molar |
Large surface, wide and uneven |
Chewing, crushing and grinding |
6 |
3. Describe the role of teeth, tongue, and salivary glands in oral digestion.
= The oral cavity is important for the ingestion of food, and to a certain extent, its digestion. The teeth, tongue, and salivary glands are present in the oral cavity. An adult human being has 32 permanent teeth. These are of four different types: incisors, canines, premolars, and molars. The tongue enables food to be mixed with saliva. It also helps in tasting the food.
Salivary glands secrete saliva, a watery fluid, containing the enzyme, salivary amylase. This enzyme helps in the digestion of carbohydrates, mainly starch.
4. Give examples of any four digestive enzymes and their mode of action.
= Any four digestive enzymes and their mode of action are -
i) Salivary amylase - It is produced in salivary gland. It is released in the mouth. It turns starch into maltose.
ii) Pepsin - It is produced in gastric gland. It is released in stomach. It turns proteins into proteoses and peptones.
iii) Trypsin - It is produced in pancreas. It is released in duodenum. It turns proteins into peptides.
iv) Lipase - It is produced in pancreas. It is released in duodenum. It turns emulsified fat into fatty acid and glycerol.
5. Draw a neat, labelled diagram of the digestive system.
=
The Digestive System
6. Explain the process of digestion and absorption in small intestine.
= Partially digested soupy chyme reaches the first part of the small intestine, the duodenum. Duodenum receives bile juice from the gall bladder and pancreatic juice from the pancreas. Bile emulsifies fats by breaking down large fat globules into smaller droplets. Bile also provides an alkaline medium in the duodenum for the pancreatic enzymes to act. The pancreas secretes digestive enzymes that chemically break down complex food molecules into simpler ones. These enzymes include pancreatic amylase (for carbohydrate digestion), trypsin (for protein digestion), and lipase (for fat digestion).
From the duodenum, the chyme passes into the jejunum and then into ileum. Cells lining the ileum secrete an intestinal juice that contains a number of enzymes. These are erepsin, maltase, sucrase, and lactase. Food is acted upon by these enzymes and is completely digested.
7. State any four unhealthy food habits.
= Four unhealthy food habits are -
i) Overeating : The stomach can expand and hold up to 1.5 litres of food. Consuming more food can make you feel uncomfortable. It can put pressure on the stomach causing stomach ache. It can bring about a feeling of lethargy.
ii) Eating late at night : Long gaps between lunch and dinner make us eat more during the dinner. This shortens the sleep duration and upsets the body's natural clock. Over a period of time, it can cause indigestion, hyperacidity, weight gain, and an increased risk of obesity.
iii) Munching on high calorie food while doing other activities : You are unable to estimate how much you ate if you are in a habit of eating while watching TV, reading books, or browsing the Internet. This results in overeating.
iv) Following crash diets or food fads : Crash diets may lead to drastic weight loss in the short term, but they may also result in a much higher weight gain, and other health problems in the long term, by creating an imbalance in the process of digestion.
PICTURE STUDY
1. Observe the figure and answer the questions.
a. Label the parts numbered 1-5 in the figure.
= 1- Liver;
2 - Stomach;
3 - Gall Bladder;
4 - Small Intestine;
5 - Large Intestine;
b. Give the names of all protein digesting enzymes released by part 2 and 4.
= Protein digesting enzyme released by 2 is pepsin.
Protein digesting enzyme released by 4 is trypsin.
c. What is the end product of protein digestion?
= The end product of protein digestion is amino acid.
d. Name the juice that is stored in part 3.
= Bile is stored in part 3.
e. On which side of your body is the stomach located?
= The stomach is located on the right side of our body.
2. The pictures A and B show the digestive glands of the human digestive system. Study the same and answer the questions that follow.
a. Identify the glands present in A and B. What are their secretions called?
= A - Salivary gland; It secretes saliva.
B - Pancreas; It secretes pancreatic juice.
b. Label the parts numbered 1 and 2 in B.
= 1 - Gall Bladder;
2 - Duodenum;
c. What is the function of the part labelled 1?
= Gall bladder temporarily stores bile.
d. Explain the process of digestion in mouth.
= Saliva, secreted by the salivary glands in the mouth, contains an enzyme called salivary amylase. It breaks down the starch present into smaller molecules of sugar (maltose). After thorough chewing and mixing with saliva, a semi-solid mass of food, called bolus, is formed. This is then swallowed.