Skin - "The Jack of All Trades"

Progress Check 1

Question 1

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

Answer

The four ways in which the skin serves as a protective layer for our body are:

1. It protects the underlying tissues from mechanical shocks.
2. It holds the body fluids inside and prevents excessive loss of water by evaporation.
3. It prevents harmful substances or disease-causing germs from entering our body.
4. It protects the body against excess ultraviolet light which is potentially very harmful.

Question 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

Respiration, storage of glycogen, digestion and secretion of hormone are not the functions of the human skin.

Progress Check 2

Question 1

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

Answer

1. Stratum corneum (Cornified outermost layer)
2. Granular layer (middle layer)
3. Malpighian stratum (Malpighian layer or Germinative layer)

Question 2

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

1. Stratum corneum is made of dead cells having keratin.
2. The malpighian layer is hard and resistant to bacterial invasion.
3. The pigment melanin which imparts colouration to the skin is found in the malpighian layer.
4. The dermis is very thick on palms and soles.

Answer

1. True
2. False
   Corrected statement— The cornified layer is hard and resistant to bacterial invasion.
3. True
4. True

Progress Check 3

Question 1

Match the items in Column I with those in Column II

Answer

Question 2

How do hairs provide the sensation of touch?

Answer

Hairs provide the sensation of touch because nerve fibres extend up to their bases.

Question 3

How is the outer surface of the skin made waterproof?

Answer

The oily secretion (sebum) of sebaceous gland makes the skin waterproof.

Progress Check 4

Question 1

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

1. All mammals are ectothermal.
2. Hibernation is also known as summer sleep.
3. Human body temperature normally is 98.6°F (37°C).
4. Vigorous activity in a cold day overheats you.
5. The principal heat-regulating centre is located in the thyroid.
6. Increased body heat causes vasoconstriction.
7. Facial hair in humans contributes to sex differences.

Answer

1. All mammals are endothermal.
2. Hibernation is also known as winter sleep.
3. Human body temperature normally is 98.6°F (37°C).
4. Vigorous activity in a cold day warms you.
5. The principal heat-regulating centre is located in the hypothalamus.
6. Increased body heat causes vasodilation.
7. Facial hair in humans contributes to sex differences.

Multiple Choice Type

Question 1

If for some reason the sebaceous glands fail to function:

1. the body will not be able to regulate the body temperature
2. the skin will turn darker with more melanin
3. the hairs will fail to grow
4. the skin will turn dry and rough

Answer

the skin will turn dry and rough

Reason — The sebaceous gland keeps the skin oily and conserves moisture in the body.

Question 2

Which one of the following pairs includes the abnormal conditions of skin pigmentation?

1. Leukoderma, Ringworm
2. Albinism, Leukoderma
3. Baldness, Albinism
4. Rickets, Baldness

Answer

Albinism, Leukoderma

Reason — In Leukoderma, skin pigmentation (melanin) is lost from smaller or larger patches at different regions of the body. In Albinism, complete loss of pigmentation occurs all over the body.

Question 3

Which one of the organs listed below, functions in regulating our body temperature most actively?

1. Heart
2. Lungs
3. Skin
4. Stomach

Answer

Skin

Reason — The skin prevents loss of heat in cold weather and facilitates loss of heat in hot weather.

Question 4

Sweat glands are situated in :

1. Epidermis
2. Dermis
3. Both
4. None of these

Answer

Dermis

Reason — Sweat glands are present in the dermis.

Question 5

The epidermis is highly thickened in:

1. Eyelid
2. Thigh
3. Lip
4. Palm

Answer

Palm

Reason — Palm and sole have highly thickened epidermis.

Question 6

The sense organ which belongs to the integumentary system of our body is :

1. Eyes
2. Tongue
3. Ears
4. Skin

Answer

Skin

Reason — Skin is the largest sense organ which forms the integument of our body.

Question 7

Which of the following tissues stores fat in the lower parts of dermis?

1. Stratified epithelium
2. Connective tissue
3. Adipose tissue
4. Muscular tissue

Answer

Adipose tissue

Reason — Adipose tissue is special type of tissue that stores fat.

Question 8

The visible part of the hair is:

1. Hair bulb
2. Hair follicle
3. Hair papilla
4. Hair shaft

Answer

Hair shaft

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

Question 9

The principal heat-regulating centre of our body is located in:

1. Hypothalamus
2. Cerebrum
3. Thalamus
4. Cerebellum

Answer

Hypothalamus

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

Question 10

The activity of the mammary glands is related to which reproductive hormone:

1. Progesterone
2. Prolactin
3. Oestrogen
4. Testosterone

Answer

Prolactin

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

Very Short Answer type

Question 1

Name:

(a) Two principal components of mammalian skin.

(b) Two main layers of skin proper.

(c) Three regions/sublayers of epidermis.

(d) Five derivatives of skin.

(e) Two abnormal conditions of skin pigmentation.

Answer

(a) Skin proper and derivatives of skin.

(b) Epidermis and dermis.

(c) Three regions/sublayers of epidermis are :

1. Stratum corneum (Cornified outermost layer)
2. Granular layer (middle layer)
3. Malpighian stratum (Malpighian layer or Germinative layer)

(d) Five derivatives of skin are :

1. Hair
2. Nail
3. Mammary gland
4. Sweat gland
5. Sebaceous gland.

(e) Albinism, Leukoderma

Question 2

Complete the following sentences:

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

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

(c) ............... of the skin is composed of flattened dead cells.

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

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

Answer

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

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

(c) Cornified layer 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.

Question 3

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

(a) Keratin protects us from ultraviolet rays.

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

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

(d) Ceruminous glands are modified sweat glands.

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

Answer

(a) Melanin protects us from ultraviolet rays.

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

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

(d) Ceruminous glands are modified sebaceous glands.

(e) The optimum temperature for enzymatic activity in our body is 35°C to 40°C.

Short Answer Type

Question 1

Define

(a) Skin

(b) Piloerection

(c) Heatstroke

(d) Perspiration

(e) Stratum malpighi

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 2

Distinguish 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.

Answer

(a) Difference between Leukoderma/Vitiligo and Albinism :

(b) Difference between Cold blooded and Warm blooded animals :

(c) Difference between Vasodilation and Vasoconstriction :

(d) Difference between Hibernation and Aestivation :

(e) Difference between Pimples and Black heads :

Question 3

Write the exact location of the following:

(a) Melanin

(b) Keratin

(c) Hypothalamus

(d) Granular layer

(e) Matrix

Answer

(a) Melanin — Malpighian layer (stratum malpighi) which is the innermost layer of the epidermis.

(b) Keratin — Nail.

(c) Hypothalamus — Fore brain.

(d) Granular layer — Middle layer of epidermis present below the outer cornified layer (stratum corneum).

(e) Matrix — Below the surface of the skin at the base of the nail.

Question 4

Write the important role(s) of:

(a) Cerumen

(b) Sebum

(c) Keratin

(d) Melanin

(e) Secretion of meibomian glands

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 5

Give 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.

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 6

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

Answer

The two functions of the mammalian skin are-

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

Question 7

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

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.

Long Answer Type

Question 1

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

Answer

The different structures found in the epidermis and dermis of the human skin are:

Question 2

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

Answer

Vasodilation — It is the dilation of blood vessels in the skin that leads to an increase in the blood supply.

Vasoconstriction — It is the narrowing of the blood vessels causing reduction in the blood supply to the skin.

Temperature Regulation:
In Cold Weather — When temperature is low, the blood vessels get narrowed. This reduces the blood supply to the skin. As a result, there is less loss of heat by convection, conduction and radiation and also less loss of it through vaporization of sweat because with reduced blood supply, the sweat gland secrete less sweat.
In Hot Weather — When outside temperature is high, there is vasodilation which results in greater loss of heat by radiation etc. and also by vaporization of sweat which is now produced in larger quantities due to the rich system of blood to the skin. Air movements over the body help to speed up evaporation of sweat leading to cooling effect on our body.

Question 3

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

1. Entry of germs

2. Excessive loss of heat in severe cold

3. Entry of harmful ultra-violet rays.

Answer

It provides protection in the following ways:

1. Entry of germs — The skin checks the entry of toxic substances or the agents causing infection into the body.

2. Excessive loss of heat in severe cold — The skin prevents loss of heat in cold weather and facilitates loss of heat in hot weather.

3. Entry of harmful ultra-violet rays — It protects the body against excess ultra violet light which is potentially very harmful.

Structured / Application / Skill Type

Question 1

Draw a labelled diagram of the generalized vertical section of mammalian skin.

Answer

Below diagram shows the generalized vertical section of mammalian skin:

Question 2

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

(a) Label the parts numbered 1 to 9

(b) State one main function of each of the following parts:

1. Part 2.
2. Part 3.
3. Part 4.
4. Part 9.

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

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

Answer

(a) The labels are as follows:

• 1 → Sweat-pore
• 2 → Sebaceous gland
• 3 → Sweat gland
• 4 → Fat
• 5 → Dermis
• 6 → Stratum Malpighian
• 7 → Stratum corneum
• 8 → Epidermis
• 9 → Hair

(b)

1. In the given figure, Part 2 is sebaceous gland. Its main function is to produce sebum to help keep the skin moist.
2. In the given figure, Part 3 is sweat gland. It secretes a transparent liquid (sweat) containing water and salts from the body in order to regulate body temperature.
3. In the given figure, Part 4 is Fat. The skin stores food in the form of a fat layer.
4. In the given figure, Part 9 is hair. Hair provides a touch sensation. It can be also used in the forensic study.

(c) From the above parts, the one which has atleast three functions is Sebaceous gland. Its functions are the following:

1. Protects skin
2. Produces sebum that lubricates hair and skin of mammals.
3. Sebum also protects from bacterial and fungal infections.

(d) In the given figure, Part 4 is fat. Fat accumulation in body plays a major role in determining if a person is overweight, underweight or just the right weight for both males and females. Person with balanced body weight is considered healthy. So, the right amount of fat at right places of body gives nice appearance and figure to both males and females.

Question 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.

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

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

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

Answer

(a) The process/condition shown in figures A and B are :

• A → Vasoconstriction
• B → Vasodilation

(b) Vasoconstriction occurs in cold climatic conditions. Vasodilation occurs in hot climatic conditions.

(c) The facial appearance of a person becomes pale or bluish during vasoconstriction and reddish during vasodilation.

(d) These situations may occur due to fright, nervousness or sudden emotion.