Skin — "The Jack of All Trades" - Questions & Answers

1. List the four ways in which the skin serves as a protective layer for our body.

Answer: (i) It protects the underlying tissues from mechanical shocks.
(ii) It holds the body fluids inside and prevents excessive loss of water by evaporation.
(iii) It prevents harmful substances or disease-causing germs from entering our body.
(iv) It protects the body against excess ultraviolet light which is potentially very harmful.

2. Cross out the items in the following list which are not the functions of the human skin :
Sensation, respiration, storage of glycogen, excretion, digestion, temperature regulation, synthesis of vitamin D, secretion of hormone

Answer: The items to cross out are: respiration, storage of glycogen, digestion, and secretion of hormone.

1. Name the three sub-layers of the epidermis from outer to inner.

Answer: (a) Cornified layer (stratum corneum), (b) Granular layer, and (c) Malpighian layer (stratum malpighi or germinative layer).

2. Write True (T) or False (F) for the following statements :

(i) Stratum corneum is made of dead cells having keratin.

Answer: T

(ii) The malpighian layer is hard and resistant to bacterial invasion.

Answer: F

(iii) The pigment melanin which imparts colouration to the skin is found in the malpighian layer.

Answer: T

(iv) The dermis is very thick on palms and soles.

Answer: T

1. Match the items in Column I with those in Column II.

Column I
(i) Air spaces
(ii) Mammary glands
(iii) "Goose-flesh"
(iv) Traces of urea
(v) More numerous sweat pores
(vi) Oily secretion

Column II
a. Hairs are lifted
b. Sebaceous glands
c. Rudimentary in males
d. Races of hot countries
e. Grey hair
f. Sweat

Answer:
(i) Air spaces - e. Grey hair
(ii) Mammary glands - c. Rudimentary in males
(iii) "Goose-flesh" - a. Hairs are lifted
(iv) Traces of urea - f. Sweat
(v) More numerous sweat pores - d. Races of hot countries
(vi) Oily secretion - b. Sebaceous glands

2. How do hairs provide the sensation of touch ?

Answer: Hairs provide a sensation of touch because nerve fibres extend up to their bases.

3. How is the outer surface of the skin made waterproof?

Answer: The outer surface of the skin is made oily and waterproof by a secretion called sebum, which is produced by the sebaceous glands.

The statements given below have some parts printed in bold face. In case these parts are incorrect, rewrite these in correct form.

(Note: Bold parts inferred from context)

1. All mammals are ectothermal.

Answer: All mammals are endothermal (warm-blooded).

2. Hibernation is also known as summer sleep.

Answer: Hibernation is also known as winter sleep.

3. Human body temperature normally is 98.6°F (37°C).

Answer: Correct as is.

4. Vigorous activity on a cold day overheats you.

Answer: Vigorous activity on a cold day warms you.

5. The principal heat-regulating centre is located in the thyroid.

Answer: The principal heat-regulating centre is located in the hypothalamus.

6. Increased body heat causes vasoconstriction.

Answer: Increased body heat causes vasodilation.

7. Facial hair in humans contributes to sex differences.

Answer: Correct as is.

1. Choose the correct answer from the options given below :

(i) If for some reason the sebaceous glands fail to function :
(a) the body will not be able to regulate the body temperature
(b) the skin will turn darker with more melanin
(c) the hairs will fail to grow
(d) the skin will turn dry and rough

Answer: (d) the skin will turn dry and rough

(ii) Which one of the following pairs includes the abnormal conditions of skin pigmentation ?
(a) Leukoderma, Ringworm
(b) Albinism, Leukoderma
(c) Baldness, Albinism
(d) Rickets, Baldness

Answer: (b) Albinism, Leukoderma

(iii) Which one of the organs listed below, functions in regulating our body temperature most actively ?
(a) Heart
(b) Lungs
(c) Skin
(d) Stomach

Answer: (c) Skin

(iv) Sweat glands are situated in :
(a) Epidermis
(b) Dermis
(c) Both
(d) None of the above

Answer: (b) Dermis

(v) The epidermis is highly thickened in :
(a) Eyelid
(b) Thigh
(c) Lip
(d) Palm

Answer: (d) Palm

(vi) The sense organ which belongs to the integumentary system of our body is :
(a) Eyes
(b) Tongue
(c) Ears
(d) Skin

Answer: (d) Skin

(vii) Which of the following tissues stores fat in the lower parts of dermis ?
(a) Stratified epithelium
(b) Connective tissue
(c) Adipose tissue
(d) Muscular tissue

Answer: (c) Adipose tissue

(viii) The visible part of the hair is :
(a) Hair bulb
(b) Hair follicle
(c) Hair papilla
(d) Hair shaft

Answer: (d) Hair shaft

(ix) The principal heat-regulating centre of our body is located in :
(a) Hypothalamus
(b) Cerebrum
(c) Thalamus
(d) Cerebellum

Answer: (a) Hypothalamus

(x) The activity of the mammary glands is related to which reproductive hormone :
(a) Progesterone
(b) Prolactin
(c) Oestrogen
(d) Testosterone

Answer: (b) Prolactin

(xi) The fibrous structural protein, keratin is found in (P) ................... and a pigment melanin is contained in (Q) ................... of the epidermis.
(a) P - Malpighian layer, Q - Cornified layer
(b) P - Stratum malpighi, Q - Granular layer
(c) P - Stratum corneum, Q - Germinative layer
(d) P - Granular layer, Q - Cornified layer

Answer: (c) P - Stratum corneum, Q - Germinative layer

(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 :
Glands: P / Functions: Lubricate the margins of the eyelids.
Glands: Q / Functions: Protect the delicate eardrum from dust particles and germs.
Identify the correct pair of glands.
(a) P - Meibomian glands, Q - Salivary glands
(b) P - Ceruminous glands, Q - Meibomian glands
(c) P - Salivary glands, Q - Ceruminous glands
(d) P - Meibomian glands, Q - Ceruminous glands

Answer: (d) P - Meibomian glands, Q - Ceruminous glands

1. Name :

(a) Two principal components of mammalian skin

Answer: Epidermis and Dermis

(b) Two main layers of skin proper

Answer: Epidermis and Dermis

(c) Three regions/sublayers of epidermis

Answer: Cornified layer (stratum corneum), Granular layer, and Malpighian layer (stratum malpighi or germinative layer)

(d) Five derivatives of skin

Answer: Hair, Nails, Sebaceous glands, Sweat glands, and Mammary glands

(e) Two abnormal conditions of skin pigmentation

Answer: Leukoderma (Vitiligo) and Albinism

2. Complete the following sentences :

(a) The contraction of erector (arrector) muscle pulls the hair to a somewhat vertical position.

(b) The oily secretion sebum makes the skin waterproof.

(c) The cornified layer (stratum corneum) of the skin is composed of flattened dead cells.

(d) The hard outer part of the nail is termed as plate.

(e) Meibomian glands open on the margins of the eyelids.

3. Correct the following statements by changing only the first or the last word.

(a) Keratin protects us from ultraviolet rays.

Answer: Melanin protects us from ultraviolet rays.

(b) Vitamin E can be synthesized when skin is exposed to sunlight.

Answer: Vitamin D can be synthesized when skin is exposed to sunlight.

(c) Black heads are caused due to hormonal influence and inflammation of the sebaceous gland.

Answer: Acne are caused due to hormonal influence and inflammation of the sebaceous gland.

(d) Ceruminous glands are modified sweat glands.

Answer: The statement is already correct as given.

(e) The optimum temperature for enzymatic activity in our body is 41°C to 45°C.

Answer: The optimum temperature for enzymatic activity in our body is 35°C to 40°C.

1. Define :

(a) Skin

Answer: Skin is the outermost covering of the body, stretched all over in the form of a layer, which serves as an almost impermeable protective barrier and performs multiple vital functions.

(b) Piloerection

Answer: Piloerection is the lifting of hair to a somewhat vertical position, caused by the contraction of the erector muscle during cold or emotion, giving the skin a "goose flesh" appearance.

(c) Heatstroke

Answer: Heatstroke (sunstroke) is a potentially fatal condition in which sweat production is unable to keep pace with its evaporation in very hot winds, resulting in a dangerous rise in body temperature (fever).

(d) Perspiration

Answer: Perspiration (sweating) is the excretion of fluid consisting of water, salts, and urea by the sweat glands, serving primarily to lose body heat through evaporation.

(e) Stratum malpighi

Answer: Stratum malpighi (germinative layer) is the innermost region of the epidermis whose cells actively divide to produce new cells and which contains the pigment melanin.

2. Distinguish between :

(a) Leukoderma/Vitiligo and Albinism .

Answer: Leukoderma is a condition where skin pigmentation (melanin) is lost from smaller or larger patches at different regions of the body. Albinism is a genetic condition causing complete loss of pigmentation all over the body, including hair, eyebrows, eyelashes, and iris.

(b) Cold blooded and Warm blooded animals.

Answer: Cold-blooded (ectothermal) animals have a body temperature that fluctuates with the environmental temperature. Warm-blooded (endothermal) animals maintain a more or less constant body temperature regardless of outside temperature.

(c) Vasodilation and Vasoconstriction.

Answer: Vasodilation is the dilation (widening) of blood vessels in the skin to increase blood supply and enhance heat loss during hot weather. Vasoconstriction is the narrowing of blood vessels in the skin to reduce blood supply and conserve body heat during cold weather.

(d) Hibernation and Aestivation.

Answer: Hibernation is "winter sleep," an inactive state some organisms enter to escape extreme cold. Aestivation is "summer sleep," an inactive state used to escape extreme heat.

(e) Pimples and Black heads.

Answer: Pimples are boils resulting from the bacterial infection of accumulated, nutritive sebum. Blackheads occur when open pores get clogged with dead skin cells and sebum, which turns black upon oxidation by the air.

3. Write the exact location of the following :

(a) Melanin

Answer: Contained in the cells of the malpighian layer (stratum malpighi) of the epidermis and in hair follicles.

(b) Keratin

Answer: Found in the outermost cornified layer (stratum corneum) of the epidermis, as well as in nails and hair.

(c) Hypothalamus

Answer: Located in a portion of the fore-brain.

(d) Granular layer

Answer: Located in the middle of the epidermis, between the outermost cornified layer and the innermost malpighian layer.

(e) Matrix

Answer: Located just below the skin surface at the base of the nail.

4. Write the important role(s) of :

(a) Cerumen

Answer: Lubricates and protects the delicate eardrum from dust particles and germs.

(b) Sebum

Answer: Makes the hair and the outer surface of the skin oily and waterproof, keeping the epidermis supple and preventing moisture loss by evaporation.

(c) Keratin

Answer: Makes the cornified layer of skin tough, offering resistance to mechanical damage, bacterial infection, and water loss.

(d) Melanin

Answer: Imparts colouration to the skin and hair, and acts like an "umbrella" to protect inner body parts from the harmful ultraviolet rays of sunlight.

(e) Secretion of meibomian glands

Answer: Lubricates the margins of the eyelids and prevents the overflow of tears.

5. Give reasons/Explain :

(a) Skin can be considered as an accessory excretory organ.

Answer: The skin assists in the process of excretion (through sweating) by eliminating water, salts, and to a very limited extent, traces of urea from the body.

(b) A normal healthy young person can start perspiring even when the outside atmosphere is intensely cold.

Answer: This is known as "cold sweat" and may be due to psychic influences such as fright and nervousness, or it may accompany nausea and severe pain.

(c) Hairs can be used in forensic investigation.

Answer: Hairs from different parts of the body show subtle differences unique to individuals, which helps in crime detection (forensic) investigations.

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

Answer: 1. Protection against mechanical shocks, disease-causing germs, and ultraviolet light. 2. Sensation, acting as a sense organ for touch, pain, pressure, and heat.

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

Answer: "Goose-flesh" is a somewhat contracted and wrinkled appearance of the skin with lifted hair (piloerection). It is brought about during winter or emotional stress when the erector (arrector) muscle of the hair contracts, pulling the hair vertically and depressing the epidermis at the other end.

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

Answer:

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

Answer: Vasodilation refers to the dilation (widening) of blood vessels in the skin. In hot weather, it increases blood supply to the skin, maximizing heat loss by radiation and sweat evaporation to cool the body down. Vasoconstriction refers to the narrowing of blood vessels in the skin. In cold weather, it reduces the blood supply to the skin, which cuts down the loss of heat by convection, conduction, and radiation, thus conserving body heat.

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

(a) Entry of germs.

Answer: The outermost cornified layer of the epidermis consists of tough, dead cells made of keratin which act as a physical barrier resisting bacterial infection.

(b) Excessive loss of heat in severe cold.

Answer: The skin reduces heat loss via vasoconstriction (narrowing of blood vessels) and has a subcutaneous layer of fat beneath the dermis that acts as a heat insulator. Hair can also stand up (piloerection) to trap a layer of warm air.

(c) Entry of harmful ultra-violet rays.

Answer: The malpighian layer contains the pigment melanin, which acts like an "umbrella" absorbing and protecting the inner body parts from harmful ultraviolet rays.

1. Draw a labelled diagram of the generalised vertical section of the mammalian skin.

Answer: (Students should draw the diagram referring to Fig. 14.1 showing layers like Stratum corneum, Malpighian layer, Sebaceous gland, Sweat gland, Hair follicle, etc., as AI cannot generate hand-drawn images.)

2. Given below is a diagrammatic sketch of the vertical section of the human skin.

(a) Label the parts numbered from 1 to 9.

Answer: 1. Hair shaft 2. Sebaceous gland 3. Sweat gland 4. Hair papilla/bulb 5. Blood vessels 6. Erector muscle 7. Dermis 8. Epidermis 9. Sweat pore

(b) State one main function of each of the following parts : (i) Part 2. (ii) Part 3. (iii) Part 4. (iv) Part 9.

Answer: (i) Part 2 (Sebaceous gland): Secretes sebum to keep the skin and hair oily and waterproof. (ii) Part 3 (Sweat gland): Secretes sweat to lose body heat by evaporation. (iii) Part 4 (Hair papilla/bulb): Contains capillary blood supply and is responsible for hair growth. (iv) Part 9 (Sweat pore): Serves as an outlet on the skin surface to release sweat.

(c) Name any one of the above parts which has at least three functions.

Answer: Epidermis (Part 8) - It provides protection (mechanical and from UV rays), prevents water loss, and houses the germinative layer that replaces worn-out cells.

(d) Part 4 may add to one's good appearance or the "figure". State one example of this function which may be common to both men and women.

Answer: Hair on the scalp (head hair) adds to the good appearance and aesthetic features common to both men and women.

3. The figures A and B given below represent the ways of heat regulation in our body with the help of blood vessels. Study the figures and answer the following questions.

(a) Name the process/condition shown in figures A and B.

Answer: Figure A represents Vasoconstriction. Figure B represents Vasodilation.

(b) During what climatic conditions, do these processes occur in our body ?

Answer: Vasoconstriction (A) occurs during cold climatic conditions. Vasodilation (B) occurs during hot climatic conditions.

(c) What colour change do we see in the facial appearance of a person during these situations?

Answer: During vasoconstriction (A), the face looks pale or bluish. During vasodilation (B), the face appears red or flushed.

(d) Do these situations occur due to emotional causes ? If yes, name them.

Answer: Yes, vasoconstriction can occur due to fright or nervousness. Vasodilation can also be triggered by emotional causes.

4. Rohit and Rahman are suffering from two abnormal conditions of skin pigmentation. Their images are shown below as figures (A) and (B) respectively.

(a) Rohit has ........................ whereas Rahman is suffering from ........................ .

Answer: Rohit has Leukoderma (Vitiligo) whereas Rahman is suffering from Albinism.

(b) Write one difference between the above two abnormal conditions of the skin.

Answer: Leukoderma involves the loss of melanin from specific patches of the skin, whereas Albinism is a complete loss of pigmentation all over the body, including the hair, eyelashes, and iris, due to genetic inheritance.

(c) Mention the exact location of the pigment involved in the above conditions.

Answer: The pigment (melanin) is located in the cells of the malpighian layer (stratum malpighi) of the epidermis.

(d) What is the name of the above pigment ? Write its one important role in human body.

Answer: The pigment is Melanin. Its important role is to act like an "umbrella" protecting the inner parts of the body from the harmful effects of ultraviolet rays of sunlight.

(e) How does this pigment affect our complexion?

Answer: The different quantities of melanin pigment present in the skin lead to the formation of very light-brown to dark colouration, determining the individual's complexion.

(Choose the answer based on the codes given below.)
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

(i) Assertion (A) : Adipose cells of the skin stores reserve food in the form of fat which can be used during starvation.
Reason (R) : Adipose cells are located in the lowest part of the dermis.

Answer: (b) Both A and R are true but R is not the correct explanation of A.

(ii) Assertion (A) : Keratin is the fibrous structural protein located in the stratum corneum of the epidermis.
Reason (R) : Keratin makes the skin tough and impervious and offers resistance to mechanical damage.

Answer: (b) Both A and R are true but R is not the correct explanation of A. (It lists function rather than explaining the exact cause of location).

(iii) Assertion (A) : Leather obtained from the hides of animals is actually the epidermis of the skin.
Reason (R) : Dermis is tough and flexible which is made up of a thick layer of connective tissue with elastic fibres.

Answer: (d) A is false but R is true. (Leather is actually the dermis part).

(iv) Assertion (A) : Skin is the largest sense organ which is concerned with the sensation of pressure, pain, heat and cold.
Reason (R) : Skin is the main organ of integumentary system concerned with the protection of the body against mechanical, thermal and physical injury; and perspiration.

Answer: (b) Both A and R are true but R is not the correct explanation of A.

(v) Assertion (A) : Vasoconstriction is the phenomenon in which the blood vessels become narrow and supply less amount of blood to the skin.
Reason (R) : Vasoconstriction normally occurs during cold climatic conditions or when a person becomes nervous.

Answer: (b) Both A and R are true but R is not the correct explanation of A.

1. Aarav has recently started getting pimples on his face. He feels awkward in school and avoids looking at himself in the mirror. He worries that everyone is ...

(Note: The remainder of this case study and its associated questions are truncated in the scanned document and cannot be answered.)