Question 1

Question 3How does our skin provide protection to our body against the following?Entry of germsExcessive loss of heat in severe coldEntry of harmful ultra-violet rays.

Accepted Answer

It provides protection in the following ways:Entry of germs — The skin checks the entry of toxic substances or the agents causing infection into the body.Excessive loss of heat in severe cold — The skin prevents loss of heat in cold weather and facilitates loss of heat in hot weather.Entry of harmful ultra-violet rays — It protects the body against excess ultra violet light which is potentially very harmful.

Question 2

Question 1(viii)The visible part of the hair is:Hair bulbHair follicleHair papillaHair shaft

Accepted Answer

Hair shaftReason — Hair shaft is the part which projects from the skin and may extend slightly below the surface of the epidermis.

Question 3

Question 1(ix)The principal heat-regulating centre of our body is located in:HypothalamusCerebrumThalamusCerebellum

Accepted Answer

HypothalamusReason — Hypothalamus, present in the fore brain is the principal heat-regulating centre of our body.

Question 4

Question 1(x)The activity of the mammary glands is related to which reproductive hormone:ProgesteroneProlactinOestrogenTestosterone

Accepted Answer

ProlactinReason — Prolactin is the hormone that is responsible for production of milk.

Question 5

Question 1(xi)The fibrous structural protein, keratin is found in (P) ............... and a pigment melanin is contained in (Q) ............... of the epidermis.P — Malpighian layer, Q — Cornified layerP — Stratum malpighi, Q — Granular layerP — Stratum corneum, Q — Germinative layerP — Granular layer, Q — Cornified layer

Accepted Answer

P — Stratum corneum, Q — Germinative layerReason — Keratin is a fibrous structural protein that provides protection and waterproofing to the skin. It is found in the stratum corneum, the outermost layer of the epidermis, made up of dead, keratinized cells.Melanin is the pigment responsible for skin color and UV protection. It is present in the germinative layer, the innermost layer of the epidermis.

Question 6

Question 1(xii)Abraham tried to match the modified sweat glands and sebaceous glands with their functions in the human body.He tabulated two pairs as follows:GlandsFunctionsPLubricate the margins of the eyelids.QProtect the delicate eardum from dust particles and germs.Identify the correct pair of glands.P — Meibomian glands, Q — Salivary glandsP — Ceruminous glands, Q — Meibomian glandsP — Salivary glands, Q — Ceruminous glandsP — Meibomian glands, Q — Ceruminous glands

Accepted Answer

P — Meibomian glands, Q — Ceruminous glandsReason — Meibomian glands are modified sebaceous glands located along the margins of the eyelids. Their function is to secrete an oily substance that lubricates the eyelids.Ceruminous glands are modified sweat glands found in the ear canal. They produce cerumen (earwax), which traps dust and germs, protecting the delicate eardrum.

Question 7

Question 1Define(a) Skin(b) Piloerection(c) Heatstroke(d) Perspiration(e) Stratum malpighi

Accepted Answer

(a) Skin — Skin is the outermost covering of the body stretching all over in the form of a layer. It is the largest organ of our body.(b) Piloerection — In Piloerection, the hair is lifted due to contraction of the erector muscle and the surface of the skin presents a somewhat contracted and wrinkled appearance.(c) Heatstroke — Heatstroke or sunstroke is a condition in which sweat production is unable to keep pace with its evaporation in very hot winds.(d) Perspiration — The process of sweating out as a result of thermoregulation is called perspiration.(e) Stratum malpighi — The innermost germinative layer of epidermis is called stratum malpighi.

Question 8

Question 2Distinguish between:(a) Leukoderma/Vitiligo and Albinism.(b) Cold blooded and Warm blooded animals.(c) Vasodilation and Vasoconstriction.(d) Hibernation and Aestivation.(e) Pimples and Black heads.

Accepted Answer

(a) Difference between Leukoderma/Vitiligo and Albinism :Leukoderma/VitiligoAlbinismSkin pigmentation is lost from smaller or longer patches at different region of the body.Complete loss of pigmentation all over the body including hair, eyebrows, eyelashes and even the iris.Exact cause of Leukoderma is not yet known.Albinism is a recessive trait caused due to inheritance.(b) Difference between Cold blooded and Warm blooded animals :Cold blooded animalsWarm blooded animalsBody temperature of cold-blooded animals changes with the temperature of their surroundings.Body temperature of warm-blooded animals remains constant and is not affected by the temperature of their surroundings.Cold blooded animals undergo aestivation or hibernation.Warm blooded animals do not undergo aestivation or hibernation.Example: ReptilesExample: Mammals(c) Difference between Vasodilation and Vasoconstriction :VasodilationVasoconstrictionDilation of blood capillaries near the skin.Constriction of blood capillaries near the skin.Caused due to increase in temperature.Caused due to decrease in temperature.Leads to loss of body heat.Conserves body heat.(d) Difference between Hibernation and Aestivation :HibernationAestivationHibernation is a state of reduced metabolic activity and lowered body temperature that animals enter during winter (winter sleep) or periods of food scarcity.Aestivation is a state of dormancy that animals enter during hot and dry seasons (summer sleep), typically in response to extreme heat or drought.The main purpose of hibernation is to conserve energy and survive unfavorable conditions.The main purpose of aestivation is to avoid excessive water loss and survive in arid environments.Animals that hibernate experience a significant drop in metabolic rate, heart rate, and body temperature.Animals undergoing aestivation also reduce their metabolic rate and activity, but the reduction is not as extreme as in hibernation.(e) Difference between Pimples and Black heads :PimplesBlack headsPimples are caused by growth of bacteria due to sebum accumulation.Black heads are caused due to open pores getting clogged with dead skin cells and sebum.Pimples appear as red, inflamed bumps on the skin.Black heads appear black and dark due to oxidation by the air.

Question 9

Question 4Write the important role(s) of:(a) Cerumen(b) Sebum(c) Keratin(d) Melanin(e) Secretion of meibomian glands

Accepted Answer

(a) Cerumen — Wax like substance which protects and lubricates the delicate eardrum from dust particles and germs.(b) Sebum — It makes the hair and outer surface of skin oily and waterproof.(c) Keratin — In nails, Keratin forms the nail plate which provides a hard, protective covering over the nail bed.(d) Melanin — It is responsible for colouration of the skin. It also protects the inner parts of the body from harmful ultraviolet rays of the Sun.(e) Secretion of meibomian glands — It lubricates the margins of the eyelids and prevents the overflow of tears.

Question 10

Question 5Give reasons/Explain:(a) Skin can be considered as an accessory excretory organ.(b) A normal healthy young person can start perspiring even when the outside atmosphere is intensely cold.(c) Hairs can be used in forensic investigation.

Accepted Answer

(a) Skin assists in the process of excretion of water, salts and to a very limited extent, urea through sweating. Since sweating occurs mainly for temperature regulation hence skin can be considered as an accessory excretory organ.(b) A normal healthy young person can start perspiring even in cold atmosphere due to psychic influences such as fright or nervousness. This is referred to as "cold sweat".(c) Hairs from different part of body show subtle differences. Hair follicles, found at the root of the hair, have the highest concentration of DNA, making them particularly valuable for DNA analysis. Therefore, hairs can be used in forensic investigation.

Question 11

Question 6State any two functions of the mammalian skin other than those concerned with heat regulation.

Accepted Answer

The two functions of the mammalian skin are-The primary function of skin is to provide protection through four different means:Mechanical shocks.Prevention of excessive water loss.Prevents entry of diseases.Protects the body against excess ultraviolet light.The skin stores reserve food in the form of a layer of fat contained in special cells.

Question 12

Question 7What is "goose-flesh"? How is it brought about?

Accepted Answer

"Goose-flesh" is the term used to describe the contracted and wrinkled appearance of the skin that occurs during winter or in response to certain emotions. It is caused by the contraction of the erector muscles, located between the hair follicles and the outer part of the dermis. These muscles pull the hair upright, causing the skin to appear rough and forming bumps on the surface.

Skin - "The Jack of All Trades"

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