GSEB Solutions for Class 7 Science and Technology - Digestive System, Respiratory System and Circulatory System

GSEB Solutions for Class 7 Science and Technology – Digestive System, Respiratory System and Circulatory System (English Medium)

Solution 1(a):

Yes, the colour of the bread turns blue-black because of the presence of starch.

Solution 1(b):

The colour of the chewed bread turns into brown as the starch in the bread converts into sugar.

Exercise 83:

Solution 1(a):

Pulse is due to the expansion of an artery caused by the ejection of blood into the arterial system by the contractions of the heart.

Exercise 86:

Solution 1:

Sr.No.	Part of the system	Function
1	Nose	Contains mucus and hair that prevent entry of microorganisms by filtering the air.
2	Trachea	Transports the air a person breathes in through his nose or mouth, into the lungs.
3	Bronchus	Allow the passage of air and prevention of infection by preventing pathogens from going further into the lungs.
4	Lung	Receives air (oxygen) from the atmosphere through the nose and mouth with every inhale, and allows the transfer of oxygen to pass into the blood stream.

Sr.No.	Part of the system	Function
1	Mouth	With the help of teeth and tongue, salivary glands secrete saliva that contains ptyalin which digests starch and converts it into simple sugar.
2	Oesophagus	Transports food from the mouth to the stomach.
3	Stomach	Mixes the food with stomach acid to break it down and digests it and also uses pepsin to break down proteins in our food.
4	Small intestine	Responsible for absorbing most of the nutrients found within our food. It digests all types of food (carbohydrates, proteins, and fats) with the help of pancreatic juices. The duodenum absorbs the nutrients from the digested food and transfers them into the blood stream.
5	Large intestine	Reabsorb water and maintain the fluid balance of the body. Stool, or waste left over from the digestive process, is passed through the large intestine first in a liquid state and ultimately in a solid form.
6	Rectum	Act as a temporary storage site for faecalmatter before it is eliminated from the body through the anal canal.
7	Anus	Passage of waste out of the body that controls the expulsion of feces.

Sr. No.	Function
1	Blood is poured to the right atrium.
2	Oxygenated blood is poured in the left atrium.
3	Blood moves to the right ventricle due to contraction of the right atrium and the opening of the tricuspid valve.
4	Blood moves to the left ventricle due to contraction of the left atrium and the opening of the bicuspid valve.
5	Blood moves to the lungs.
6	Blood moves to different organs of the body due to contraction of left ventricle.