RBSE Solutions for Class 12 Biology Chapter 21 Human Integumentary System

Rajasthan Board RBSE Class 12 Biology Chapter 21 Human Integumentary System

RBSE Class 12 Biology Chapter 21 Multiple Choice Questions

Question 1.
The human skin originate from –
(a) Mesoderm
(b) Ectoderm
(c) Ectoderm and Mesoderm
(d) Ectoderm and Endoderm
Answer:
(c) Ectoderm and Mesoderm

Question 2.
The outermost layer of skin is stratum –
(a) corneum
(b) granulosa
(c) spins
(d) Ludum
Answer:
(a) corneum

Question 3.
Eleiden protein is found in stratum –
(a) granulosum
(b) spinosum
(c) corneum
(d) lucidum
Answer:
(d) lucidum

Question 4.
Keratohyaline protein is found in stratum –
(a) spinosum
(b) granulosum
(c) gerniinativum
(d) corneum
Answer:
(b) granulosum

Question 5.
Skin derivatives are –
(a) Nails
(b) Sweat glands
(c) Sebaceous glands
(d) All the above
Answer:
(d) All the above

Question 6.
Sebaceous glands are –
(a) Apocrine
(b) Mesocrine
(c) Holocrine
(d) Acrine
Answer:
(c) Holocrine

Question 7.
A barrier layer of the skin is stratum –
(a) corneum
(b) Ludum
(c) granules
(d) spins
Answer:
(b) Ludum

Question 8.
Sweat glands are –
(a) Apocrine
(b) Merocrine
(c) Acrine
(d) None of the above
Answer:
(c) Acrine

Question 9.
Melanin pigments in the hair are found in –
(a) Cortex
(b) Cuticle
(c) Medulla
(d) All of the above
Answer:
(a) Cortex

Question 10.
The fat layer found below the skin helps in –
(a) body shape
(b) Temperature resistant
(c) fat storage
(d) All of the above
Answer:
(d) All of the above

RBSE Class 12 Biology Chapter 21 Very Short Answer Type Questions

Question 1.
Which vitamin is synthesized in the skin?
Answer:
Vitamin D.

Question 2.
Where the meibomian glands are found in human skin?
Answer:
The inner side of the eyelids.

Question 3.
Mammary glands in man are the modification of which gland?
Answer:
Modified sebaceous gland.

Question 4.
Human mammary glands are of which type?
Answer:
Apocrine in human beings.

Question 5.
Why skin is called as “Jack of all trades”?
Answer:
The skin performs almost all the body functions. Hence, they are called “Jack of all trades”.

Question 6.
Which pigment imparts colour to the skin?
Answer:
Melanin pigment.

Question 7.
The dermis originates from which layer?
Answer:
Embryonic mesoderm.

Question 8.
Which protein is found in the dermis?
Answer:
Collagen protein.

Question 9.
Name the oily substance secreted by sebaceous glands.
Answer:
Sebum.

Question 10.
Name the muscle responsible for hair movement.
Answer:
Arrector pili.

RBSE Class 12 Biology Chapter 21 Short Answer Type Questions

Question 1.
Describe the various layers of skin epidermis.
Answer:
Epidermis:

It originates from the embryonic ectoderm.
It is thickest in the body regions subjected to wear and tear such as soles and palm.
It is very thin in eyelids and cornea.
The epidermis is without nerves and blood vessels.
It is a stratified epithelium and consists of five types of layers.
They are as follows from inside to outside.

Stratum Malpighi or stratum germinativum:

It is the innermost layer of the epidermis which is living.
It is made up of one layer of columnar cells.
These cells divide constantly to form upper layers of the epidermis.
This layer pushes into the dermis.
These pushing are called as rete pegs.
This layer also contains some melanocytes.
These cells contain melanin pigments which impart colour to the skin.

Stratum spinosum:

This layer is situated outside the stratum Malpighi.
It consists of many layers of branched polyhedral cells.
These cells bear a hook-like structure.
This layer provides strength to the skin.

Stratum granules:

It is situated outside the stratum spinosum.
It includes 5 – 6 layers of cells having granules of keratohyalin protein.

Stratum lucidum:

It is situated outside the stratum granulosum. It consists of 3 – 4 layers of living and flat cells.
These cells contain a protein called Elieidin which is formed by keratohyalin.
The cells of this layer are enucleated and translucent.
It is waterproof and also called a barrier layer.

Stratum corneum:

It is the outermost layer which is made up of flat squamous cells.
These cells are dead because of the presence of dead Keratin protein.
It is the thickest layer of the epidermis and consists of 8 – 10 layers of cells.
It’s outermost layers sloughed off constantly.

Keratinization:
The process of formation of Keratin protein in the epidermis is called Keratinization. This process leads in the formation of hair, nails etc.

Question 2.
Draw a labelled diagram of V.S. of skin.
Answer:
RBSE Solutions for Class 12 Biology Chapter 21 Human Integumentary System 1

Question 3.
Give an account of the structure of the hair. Write its function.
Answer:
Hair:

The hair is found only in the skin of mammals which are ectodermal in origin.
The hair is situated in a hair follicle which is formed as in invagination of the stratum germinativum.
The base of the hair follicle is everted cup-like which encloses a hair papilla or dermal papilla. The hair papilla is made up of blood vessels & the nerves.
The hair consists of two parts viz.-hair shaft & hair root.
The cells of the hair root divide constantly causing the growth of the hair follicle.

The part of the hair shaft inside the hair follicle is covered by two sheaths viz.

Huxley’s sheath – Outer
Henle’s sheath – Inner & made up of cuboidal cells
The exposed part of the hair shaft is dead due to the deposition of the keratin protein.
Structurally, the hair shaft consists of three parts viz.
1. Cuticle – Outermost & made up of squamous cells.
2. Cortex – It is the outer part which contains melanin pigments. The melanin pigments are absent in the hair of the rabbit.
3. Medulla – It is the central part of the hair follicle. The lanugo is without medulla.
There is an erector pili muscle which is attached between the epidermis & the hair follicle.
The contraction of this muscle results in raising of hair which is a reflex action and called as goose flesh or cutis Isernia.
This process is stimulated by the adrenalin hormone. The grey hair is without melanin pigments and its medulla develops air cavities which provide shine to the hair.

Question 4.
Describe sweat glands.
Answer:
Sweat or Sudorphic glands:

They are coiled tubular glands which open outside directly.
They secrete sweat which contains 95% water and 5% other substances (e.g. lysozyme, salt, ammonia, urea etc.).
The sweat lowers the body temperature & excretes an excess of salts. The lysozyme found in it acts as bacteriocidal.
The sweat glands in the rabbit are apocrine.
In human beings, most of the sweat glands are eccrine or merocrine. But the sweat glands found in armpits, teats, eyelids are apocrine in function.
Sweat can be called as diluted urine. In the rabbit, the sweat glands are found only at the margins of the lips.
There are myoepithelial cells around the coiled part of the gland. The sweat is released due to the contraction of these cells.

Question 5.
Describe the sebaceous glands found in the skin.
Answer:
Sebaceous glands:

- They are compound alveolar glands which are formed as an outgrowth of the hair follicle.
- They are holocrine in function & open outside through the hair follicle.
- They secrete an oily substance called sebum.
- The sebum makes the skin & hair waterproof. The sebum has ergosterol which forms vitamin – D in presence of U-V rays of sun-light.

Question 6.
Describe human mammary glands.
Answer:
Mammary glands:

In Prototheria, human beings and other primates, the mammary glands are modified apocrine sweat glands. In remaining mammals, they are modified compound alveolar sebaceous glands.
Each mammary gland has a teat through which the mammary gland opens out. The area around the teat is darkly pigmented which is called as areola mammary.
The mammary glands secrete the milk. The milk contains mainly carcinogen, lactoglobulin, lactoalbumin, lactose and fats. In human beings, there is a pair of mammary glands on the thorax.

Question 7.
Write five functions of the skin.
Answer:

Being elastic, the skin helps in locomotion.
The skin acts as a respiratory organ, sensory organ, absorptive organ, secretory organ, nutritive organ, excretory organ, storage organ & synthetic organ etc.
It provides shape to the body.
The perineal glands secrete a sex attractant pheromone.
The certain process of the tympanum.

Question 8.
What is Keratinization? Write the names of the structures formed by it.
Answer:
The process of formation of dead Keratin protein in the stratum corneum of the dermis is called Keratinization. Its derivatives are nails, hair etc.

Question 9.
Write in brief about erector pili muscle.
Answer:
They are special muscles consists of smooth muscle fibres. They remain attached between the epidermis and the hair follicle. Their contraction causes the raising of hair.

Question 10.
Describe the glands associated with eyes & ears.
Answer:
1. Meibomian glands:

They are modified sebaceous glands and are also called as tarsal glands.
They are found on the inner side of the eye-lids.
They secrete an oily substance which keeps the eyes moist.

2. Glands of Sizes:

They are modified sebaceous glands.
They are associated with the hair follicles of the eyelashes.
Their oily secretion lubricates the eye-lashes.

3. Ceruminous glands:

They are modified sweat glands.
They are found in external auditory meatus and they secrete ear wax which is also called as cerumin. The cerumin is a type of carbohydrate.
The cerumin makes the tympanums waterproof.

Question 11.
Where the scent glands are found? Write their role.
Answer:
Perineal glands:

It is formed by the modification of the sebaceous glands.
They are also called as scent glands or inguinal glands.
They are situated near the rectum in the perineum region.
They secrete a pheromone which acts as a sex attractant.

RBSE Class 12 Biology Chapter 21 Essay Type Questions

Question 1.
Explain the structure of human skin. Give labelled diagrams.
Answer:
Histology of skin:
The skin consists of two layers –

Epidermis.
Dermis.

1. Epidermis:

It originates from the embryonic ectoderm.
It is thickest in the body regions subjected to wear and tear such as soles and palm.
It is very thin in eyelids and cornea.
The epidermis is without nerves and blood vessels.
It is a stratified epithelium and consists of five types of layers.
They are as follows from inside to outside.

Stratum Malpighi or stratum germinativum:

It is the innermost layer of the epidermis which is living.
It is made up of one layer of columnar cells.
These cells divide constantly to form upper layers of the epidermis.
This layer pushes into the dermis.
These pushing are called as rete pegs.
This layer also contains some melanocytes.
These cells contain melanin pigments which impart colour to the skin.

Stratum spinosum:

This layer is situated outside the stratum Malpighi.
It consists of many layers of branched polyhedral cells.
These cells bear a hook-like structure.
This layer provides strength to the skin.

Stratum granules:

It is situated outside the stratum spinosum.
It includes 5 – 6 layers of cells having granules of keratohyalin protein.

Stratum lucidum:

It is situated outside the stratum granulosum. It consists of 3 – 4 layers of living and flat cells.
These cells contain a protein called Elieidin which is formed by keratohyalin.
The cells of this layer are enucleated and translucent.
It is waterproof and also called a barrier layer.

Stratum corneum:

It is the outermost layer which is made up of flat squamous cells.
These cells are dead because of the presence of dead Keratin protein.
It is the thickest layer of the epidermis and consists of 8 – 10 layers of cells.
It’s outermost layers sloughed off constantly.

Keratinization:
The process of formation of Keratin protein in the epidermis is called Keratinization. This process leads in the formation of hair, nails etc.

2. Dermis:

It originates from the embryonic parietal mesoderm. It is situated below the epidermis and it is 2 – 3 times thicker than the epidermis. It is elastic and made up of fibrous connective tissues.
It consists of collagen fibres, yellow elastic fibres, blood vessels, nerves, smooth muscle fibres, cutaneous receptors, hair follicles etc.
It is divisible into two parts:
Papillary layer:
1. It is the outer layer of the dermis which forms ręte pegs with the epidermis.
2. It contains blood vessels and the sense organs.
3. The collagen fibres are less in this layer.
Reticular layer:
1. It is situated below the papillary layer.
2. It has more collagen fibres.
3. It keeps the skin stretched.

Sub-dermis:

It is an extra layer which is situated below the dermis.
It is divisible into two layers:
Stratum adipose:
1. It is also called as panniculus Ipsum.
2. It consists of adipose tissues which store extra food & it functions as heat resistant layer.
Stratum Carnosus:
1. It is also called as panniculus caucus.
2. It consists of areolar connective tissue which connects the skin with the rest body.
3. It consists of adipose tissues which store extra food & its functions as heat resistant layer.

Question 2.
Describe various derivatives of human skin.
Answer:
Derivatives of the skin:
The structures of the skin which originate from the skin itself are called derivatives. Such as hair, cutaneous glands, cutaneous receptors etc.
1. Hair:

The hair is found only in the skin of mammals which are ectodermal in origin.
The hair is situated in a hair follicle which is formed as in invagination of the stratum germinativum.
The base of the hair follicle is everted cup-like which encloses a hair papilla or dermal papilla. The hair papilla is made up of blood vessels & the nerves.
The hair consists of two parts viz.-hair shaft & hair root.
The cells of the hair root divide constantly causing the growth of the hair follicle.
The part of the hair shaft inside the hair follicle is covered by two sheaths viz.
1. Huxley’s sheath – Outer
2. Henle’s sheath – Inner & made up of cuboidal cells
The exposed part of the hair shaft is dead due to the deposition of the keratin protein.
Structurally, the hair shaft consists of three parts viz.
1. Cuticle – Outermost & made up of squamous cells.
2. Cortex – It is the outer part which contains melanin pigments. The melanin pigments are absent in the hair of the rabbit.
3. Medulla – It is the central part of the hair follicle. The lanugo is without medulla.
There is an erector pili muscle which is attached between the epidermis & the hair follicle.
The contraction of this muscle results in raising of hair which is a reflex action and called as goose flesh or cutis Isernia.
This process is stimulated by the adrenalin hormone. The grey hair is without melanin pigments and its medulla develops air cavities which provide shine to the hair.

2. Cutaneous glands:

The skin has many types of glands.
These glands originate from the stratum germinativum of the epidermis but they are situated in the dermis. All the skin glands are exocrine and they secrete various secretions.
The mammalian skin has the following glands.

Sweat or Sudorphic glands:

They are coiled tubular glands which open outside directly.
They secrete sweat which contains 95% water and 5% other substances (e.g. lysozyme, salt, ammonia, urea etc.).
The sweat lowers the body temperature & excretes an excess of salts. The lysozyme found in it acts as bacteriocidal.
The sweat glands in the rabbit are apocrine.
In human beings, most of the sweat glands are eccrine or merocrine. But the sweat glands found in armpits, teats, eyelids are apocrine in function.
Sweat can be called as diluted urine. In the rabbit, the sweat glands are found only at the margins of the lips.
There are myoepithelial cells around the coiled part of the gland. The sweat is released due to the contraction of these cells.

Sebaceous glands:

They are compound alveolar glands which are formed as an outgrowth of the hair follicle.
They are holocrine in function & open outside through the hair follicle.
They secrete an oily substance called sebum.
The sebum makes the skin & hair waterproof. The sebum has ergosterol which forms vitamin – D in presence of U-V rays of sun-light.

Ceruminous glands:

They are modified sweat glands.
They are found in external auditory meatus and they secrete ear wax which is also called as cerumin. The cerumin is a type of carbohydrate.
The cerumin makes the tympanum waterproof.

Mammary glands:

In Prototheria, human beings and other primates, the mammary glands are modified apocrine sweat glands. In remaining mammals, they are modified compound alveolar sebaceous glands.
Each mammary gland has a teat through which the mammary gland opens out. The area around the teat is darkly pigmented which is called as areola mammary.
The mammary glands secrete the milk. The milk contains mainly carcinogens, lactoglobulin, lactoalbumin, lactose and fats. In human beings, there is a pair of mammary glands on the thorax.

Perineal glands:

It is formed by the modification of the sebaceous glands.
They are also called as scent glands or inguinal glands.
They are situated near the rectum in the perineum region.
They secrete a pheromone which acts as a sex attractant.

Meibomian glands:

They are modified sebaceous glands and are also called as tarsal glands.
They are found on the inner side of the eye-lids.
They secrete an oily substance which keeps the eyes moist.

Glands of Sizes:

They are modified sebaceous glands.
They are associated with the hair follicles of the eyelashes.
Their oily secretion lubricates the eye-lashes.

3. Cutaneous Receptors:

The skin receptors originate from the embryonic ectoderm but they are found in the dermis. They are lacking in the epidermis to avoid unnecessary stimulation.
The various skin receptors are as follows:

(1) Free Nerve endings:

They are naked or non-capsulated ends of the nerves which form a network.
They are algae-receptors i.e. sensory to the pain.

(2) Meissner’s Corpuscles:

They are capsulated corpuscles which are found in the dermal papilla. They are somewhat cylindrical.
They are tango-receptor and particularly sensory to the surface texture.
They are more in the skin of teats, external genitalia & tips of the fingers.

(3) Merkel’s discs:

They are non-capsulated & cup-like.
They are found in the reticular layer of the dermis.
They are tango-receptors & particularly sensory to continuous touch.

(4) Pacinian corpuscles:

They are bulb-like corpuscles which are encapsulated. Their capsule is comparatively thick.
They are found deep in the dermis.
They are pressure-receptors & also known to receive vibrations.

(5) Kraus end bulbs:

They are encapsulated & found deeply in the dermis.
They are frigid-receptors i.e. sensory to cold.

(6) Ruffini’s end organs:

They are non-capsulated & found deeply in the dermis.
They are thermoreceptors or coreceptors i.e. sensory to heat.

Question 3.
Describe various cutaneous glands found in the human skin.
Answer:
Cutaneous glands:

The skin has many types of glands.
These glands originate from the stratum germinativum of the epidermis but they are situated in the dermis. All the skin glands are exocrine and they secrete various secretions.
The mammalian skin has the following glands.