Skin The Jack of All Trades Long Answer Biology Class-9 ICSE Selina Publishers

Skin The Jack of All Trades Long Answer Biology Class-9 ICSE Selina Publishers Solutions Chapter-13. Step By Step ICSE Selina Concise Solutions of Chapter-13 Skin The Jack of All Trades with Exercise-13 including MCQs, Very Short Answer Type, Short Answer Type, Long Answer Type and Structured/Application Questions Solved Visit official Website CISCE for detail information about ICSE Board Class-9.

Skin The Jack of All Trades Exe-13 Long Answer Biology Class-9 ICSE Concise Selina Publishers

Board ICSE
Publications Selina Publication
Subject Biology
Class 9th
Chapter-13 Skin The Jack of All Trades
Book Name Concise
Topics Solution of D. Long Answer Type
Academic Session 2023-2024

D. Long Answer Type 

Skin The Jack of All Trades Class-9 Biology Concise Solutions  

Page 142

Question 1.

Enumerate in a tabular form the different structures found in the epidermis and dermis of the human skin .

Answer:

Epidermis Dermis
1. Stratum

 corneum:

It is the outermost layer having layers of flattened dead cells made up of horny protein called keratin.

It consists of elastic fibres, blood vessels, nerves, etc.
2. Granular
layer:
 It is very thin middle layer having two or three sublayers of flattened cells.
3. Malpighian
layer:
 It is the innermost region of the epidermis. The cells can actively divide to produce new cells.

 

Question 2.

Explain the terms “vasodilation” and “vasoconstriction”. How do these processes contribute in temperature regulation of the body?

Answer:

Vasodilation:

 Dilation of blood vessels in the skin leading to an increase in the blood supply.

Vasoconstriction:

 Narrowing of blood vessels leading to reduction in the blood supply to the skin.

Temperature regulation in cold weather:

At low temperature, the blood vessels get narrowed or vasoconstriction. This reduces the blood supply to the skin.

There is less loss of heat by convection, conduction and radiation. There is less loss of heat through vaporization as reduced blood supply lowers the secretion of sweat by sweat glands.

Temperature regulation

Temperature regulation in hot weather:
  1. At high temperature, the blood supply to the skin is increased by vasodilation or dilation of blood vessels in the skin.
  2. This results in greater loss of heat by convection, conduction and radiation.There is more loss of heat through vaporization as more sweat is secreted due to rich supply of blood to the skin.

Question 3.

How does our skin provide protection to our body against the following?

(a) Entry of germs ………….

(b) Excessive loss of heat in severe cold ………….

(c) Entry of harmful ultra-violet rays …………….

Answer:

(a) Entry of germs: Skin prevents the entry of harmful substances or infectious agents inside the body.

(b) Excessive loss of heat in severe cold: Skin prevents energy loss from the body. It conserves body heat in cold weather and facilitates loss of heat in hot weather.

(c) Entry of harmful ultra-violet rays: Skin protects the body against harmful ultraviolet light.

—  : End of Skin The Jack of All Trades D. Long Answer Class-9 ICSE Biology Solutions :–

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