RBSE Solutions For Class 12 Biology Chapter 21: Integumentary System of Human | Textbook Important Questions & Answers

RBSE Class 12 Biology Chapter 21- Integumentary System of Humans. In this chapter, students can learn in detail about the human skin, its different parts, functions. It includes detailed explanations about the two layers of the skin- dermis and epidermis, different derivatives of the skin, functions of the skin, mammary glands, stratum corneum, stratum granulosum, stratum spinosum, stratum lucidum, sebaceous Glands, sweat glands and a lot more.

These important questions help students to perform exceptionally well in their exams. By practising these important questions, students can analyze their preparation, get a thorough knowledge about all the important terminologies and at the same time, it builds students confidence towards the exam and their preparations.

RBSE Solutions for Class 12 are the best study material for both class assignments and other board examinations. By practising these important questions, students can gain deep knowledge about the topics explained in this chapter and also help them to be well prepared for their upcoming examinations.

RBSE Class 12 Biology Chapter 21 Important Questions

RBSE Biology Chapter 21: MCQ Type Questions

Q.1. Human skin originates from ___________.

(a) Mesoderm.

(b) Ectoderm.

(c) Ectoderm and Endoderm.

(d) Mesoderm and Ectoderm

Sol:(d). Mesoderm and Ectoderm

Q.2. The outermost layer of skin is ___________.

(a) Stratum Corneum.

(b) Stratum Granulosum.

(c) Stratum Spinosum.

(d) Stratum Lucidum.

Sol:(a) Stratum Corneum.

Q.3. Eleiden protein is found in ___________.

(a) Stratum Corneum.

(b) Stratum Spinosum.

(c) Stratum Lucidum.

(d) Stratum Granulosum.

Sol: (c) Stratum Lucidum.

Q.4. Kertatohyaline protein is found in ___________.

(a) Stratum Corneum.

(b) Stratum Granulosum.

(c) Stratum Germinatium.

(d) Stratum Spinosum.

Sol: (c) Stratum Germinatium.

Q.5. Which of the following are skin derivatives?

(a) Nails.

(b) Sebaceous Glands.

(c) Sweat glands.

(d) All of the above.

Sol:(d) All of the above.

Q.6. The Sebaceous gland is an example of ___________.

(a) Apocrine glands.

(b) Mesocrine glands.

(c) Holocrine glands.

(d) Apocrine glands.

Sol: (c) Holocrine glands.

Q.7. A barrier layer of the skin is called ___________.

(a) Stratum Granulosum.

(b) Stratum Lucidum.

(c) Stratum Corneum.

(d) Stratum Spinosum.

Sol: (b) Stratum Lucidum.

Q.8. The melanin pigment present in our hairs is found in ___________.

(a) Cuticle.

(b) Cortex.

(c) Medulla.

(d) All of the above.

Sol: (b) Cortex.

Q.9. The fat layer found below the skin helps in ___________.

(a) Storing fat.

(b) Temperature resistant.

(c) Providing shape to the body.

(d) All of the above.

Sol: (d) All of the above.

Q.10. The epidermis has ___________ sub layers.

(a) Five.

(b) Three.

(c) Four.

(d) Six.

Sol: (a) Five.

RBSE Biology Chapter 21: Short Answer Type Questions.

Q.1. Which vitamin is synthesized within the skin?

Sol. Vitamin D is the only vitamin which is synthesized within the skin.

Q.2. Where are the meibomian glands found in the human body?

Sol. The meibomian glands are holocrine type exocrine glands, found within or the inner side of the eyelid.

Q.3. Which gland has been modified to become a mammary gland in mammals?

Sol. Mammary glands are derived from a modification of sweat glands or modified sebaceous glands.

Q.4. What type of glands are human mammary glands?

Sol. Human mammary glands are grouped into an Apocrine gland and are found mainly in the breasts of all lactating mammals. They function by secreting fat droplets into the breast milk and are also responsible for secreting breast milk.

Q.5. What are Apocrine glands?

Sol. Apocrine glands are a subtype of exocrine secretory glands, mainly found in the skin, breast ear and also within the eyelids. These glands function by secreting viscous fluid. In the breast it secretes milk, in the ear, it forms earwax, in the skin, it functions as scent glands.

Q.6. Why is the skin called “Jack of all trades”?

Sol. The skin performs almost all the body functions, therefore it is called the “Jack of all trades”.

Q.7. Name the pigment which imparts the colour to the skin.

Sol. Melanin pigment. It is a natural pigment, which functions by giving colour to the human skin, hair, and eyes.

Q.8. Where does the dermis originate from?

Sol. The dermis is the layer of skin present between the epidermis and subcutaneous tissues. It originated from Embryonic Mesoderm.

Q.9. Which proteins are found in the dermis?

Sol. Collagen and elastin proteins are found in the dermis. They are insoluble proteins, which gives the skin power and resilience.

Q.10. Name the oily substances secreted by the sebaceous glands.

Sol. Sebum. It is a pale yellow, oily substance, which is secreted by the sebaceous glands. The sebum functions by keeping the skin and hair moisturized.

Q.11. Name the muscles which are responsible for the movement of hair on the human skin.

Sol. Arrector pili. They are the small muscles, which are attached to the base of hair follicles, which is involved in the movement of hair by contraction of their muscles.

Q.12. What is Dermis?

Sol. The layer present beneath the epidermis of the skin is called the dermis. The dermis consists of blood vessels, collagen, fat and fibres. The dermis consists of two main layers:

Papillary layer and Reticular layer.

Q.13. What are the different layers of the skin?

Sol. There are three different layers of the skin, which include:

  1. Epidermis – The outermost layer that acts as a barrier.
  2. Dermis – The middle layer comprising sweat glands, hair follicles and connective tissues.
  3. Hypodermis – The innermost layer made of fat and connective tissues.

Also Read: Structure and Function of Skin

Q.14. How does the skin get its colour?

Sol. The skin gets its colour from a pigment called melanin which is synthesised in the epidermis. The skin colour can vary from very pale to very dark.

Q.15. What is Epidermis?

Sol. The epidermis is the outermost layer of the skin, which is composed of cells called keratinocytes – made of a protein called keratin. The epidermis is made of four main layers and functions by protecting and safeguarding the internal cells and tissues.

Also Read: Difference Between Epidermis & Dermis

Q.16. How is the skin important?

Sol. Among the five important sense organs, the skin is one of the important sense organs of a human body, which is involved in the sense of touch. It is also involved in:

  1. Helps to regulate body temperature.
  2. Functions as a barrier to the outside world.
  3. Removes excess waste in the form of sweat.
  4. Acts as the first defence against harmful microbes.

Q.17. What are the functions of dermis?

Sol. The dermis is the layer, which is found beneath the epidermis of the skin. It is mainly involved in :

  1. The regulation of body temperature.
  2. The synthesis of Vitamin D on exposure to sunlight.
  3. It acts as a lubricant and protects the skin by acting against the microbes.

Q.18. What are the functions of the skin?

Sol. The primary functions of the skin are:

  1. Storage.
  2. Sensation.
  3. Excretion.
  4. Regulation of Temperature.
  5. Protection from the external environment.

Q.19. Define Zeis glands.

Sol. The Zeis glands are the glands formed by the modification of sebaceous glands. These glands are present with the follicles of the eyelashes and functions by secreting oil substances which help to keep eyelashes smooth and clean.

Q.20. What is Cortex?

Sol. Cortex is the middle layer of the skin. It comprises several layers of cells and also includes pigmented particles, which functions by providing colour to the hair. Deficiency of these pigmented particles causes the formation of grey or white hairs.

RBSE Biology Class 12: Long Answer Type Questions

Q.1. Draw a neatly labelled diagram of the vertical section of human skin.

Sol. A vertical section of human skin.

A vertical section of human skin.

Q.2. Write the difference between dermis and epidermis of the skin.

Sol. The dermis and epidermis together form the basic body covering of the skin and both perform the function of protecting internal organs from dehydration, infectious diseases and other damages. The differences between dermis and epidermis are:

Dermis

Epidermis

A layer of living cells below epidermis consisting of nerve endings, blood vessel, sweat glands and hair follicle.

An outermost layer of cells that cover the body of an organism.

Comprises a thin network of vessels known as capillaries.

Doesn’t contain blood vessels.

Comprises nerves that conduct nerve impulses from the central nervous system towards the brain.

No nerves present in the epidermis.

Found in animals only.

Found in both plants and animals.

Obtains oxygen and nutrients from the blood capillaries.

Obtains essential nutrients and oxygen by diffusion from the dermis.

Q.3. Brief out the structure of the subdermis.

Sol. Sub-dermis is an extra layer, which is present below the dermis. It is divided into two different layers.

Stratum Adipose.

  1. It is also called the panniculus Ipsum.
  2. It consists of adipose tissue, which stores extra food and it also functions as a heat resistant layer.

Stratum Carnosus.

  1. It is also called a panniculus caucus.
  2. It consists of alveolar connective tissue, which functions by connecting the skin with the rest of the body.
  3. It consists of adipose tissue, which stores extra food and it also functions as a heat resistant layer.

Q.4. What is the Integumentary System?

Sol. An integumentary system is defined as an organ system that includes skin, hair, nails, and exocrine glands.

  1. Skin: It is the outermost and the largest organ of the human body. It protects the body from chemicals, UV rays, and other physical damage.
  2. Hair: It is an accessory organ of the skin and helps in insulating the body. It also prevents the harmful UV rays from striking the skin.
  3. Nails: These organs are made of sheets of hard keratinocytes and are present on the distal ends of fingers and toes.
  4. Exocrine Glands: The exocrine glands secrete substances by means of ducts on the epithelial surface. Sweat glands, mammary glands, salivary glands, sebaceous glands are some of the exocrine glands.

Q.5. Brief out the layers of the skin epidermis.

Sol. The epidermis is the outermost layer of the skin, which originates from the embryonic ectoderm. It is the thickest layer found in the body, which is subjected to wear and tear such as soles and palm. It is very thin in eyelids and cornea. The epidermis lacks nerves and blood vessels. It is a stratified epithelium and consists of five main types of the epidermis :

Stratum Malpigh or Stratum germinativum.

  1. It is the innermost, living layer of the epidermis.
  2. It is composed of a single layer of columnar cells.
  3. This layer also consists of some melanocytes.
  4. This cell divides constantly to form upper layers of the epidermis.
  5. This layer pushes into the dermis. This pushing is called the rete pegs.
  6. These cells contain melanin pigments, which function by imparting colour to the skin.

Stratum Spinosum.

  1. This layer is situated outside the stratum Malpighi.
  2. These cells bear hook-like structures.
  3. This layer provides strength to the skin.
  4. It consists of many layers of branched polyhedral cells.

Stratum granules.

  1. It is situated outside the Stratum spinosum.
  2. It includes about 5 to 6 layers of the cells having granules of keratohyalin protein.

Stratum Lucidum.

  • It is situated outside the Stratum granules.
  • It consists of 3 to 4 layers of the living and flat cells.
  • The cells of this layer are enucleated and translucent.
  • It is waterproof, therefore it is also called the barrier layer.
  • These cells contain a protein called Elieidin, which is formed by Keratohyalin.

Stratum corneum.

  1. It is the outermost layers sloughed off constantly.
  2. It is the outermost layer, which is made up of flat squamous cells.
  3. These cells are dead because of the presence of dead keratin protein.
  4. It is the thickest layer of the epidermis and consists of 8 to 10 layers of cells.

Keratinization.

The process of the formation of keratin protein in the epidermis is called the Keratinization. This process results in the formation of hair, nails, etc.

Q.6. What is hair? Describe the structure and functions of the hair.

Sol. Hair is found in the skin of all mammals which are ectodermal in origin. It is situated within the hair follicle, which is formed as an invagination of the stratum germinativum. The base of hair follicles is an everted, cup-like structure, which encloses a hair papilla or dermal papilla. The hair papilla is composed of blood vessels and the nerves.

The hair consists of two main parts: Hair shaft and Hair roots.

The cells of these hair roots divide constantly causing the growth of the hair follicle.

The parts of the hair shaft, present inside the hair follicle is covered by two sheaths:

Huxley’s Sheath- It is the outer layer of the inner root sheath of the hair consisting of one or two layers of horny, flattened, nucleated cells.

Henle’s sheath – It is the inner layer and made up of cuboidal cells and consists of three main parts:

  1. Cuticle: Outermost layer made up of squamous cells.
  2. Cortex: It is the outer parts, which contains melanin pigments.
  3. Medulla: It is the central part of the hair follicle.

Structure of the hair on Mammalian skin.

Structure of the hair on Mammalian skin.

Q.7. What are sweat glands?

Sol. Sweat glands are also called the Sudorphic or Sudorific glands.

They are coiled, tubular glands, which are open outside. They secrete sweat, which contains 95 per cent of water and other 5 percent of other substances, such as salts, urea, ammonia, lysozymes, etc. The sweat lowers the body temperature and excretes an excess of salts present in our body. The lysozymes found in this sweat acts as bactericidal.

In humans, most of the sweat glands are eccrine or merocrine. but the sweat glands found in the armpits, eyelids, are apocrine in function. Sweat can be called diluted urine. In the rabbit, the sweat glands are found only at the margins of the lips. There are many myoepithelial cells present around the coiled part of the gland. The sweat is released main;y because of the contraction of these cells.

Q.8. What are Sebaceous glands?

Sol. The sebaceous glands are found near the hair roots and hair follicles, which are formed from the folding of the epithelium of the follicles. These glands open in the follicle.

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

Q.9. Describe human mammary glands.

Sol. Mammary glands are active only in females and secrete milk for the nourishment of the child.

These pair of glands are present within the thoracic part below the dermis. Their structure is compound, tubular alveolar type. These glands are apocrine type. The growth and other functions of the mammary glands are controlled by progesterone and estrogen hormones.

In Prototheria, human beings and other primitives the mammary glands are modified apocrine sweat glands. In remaining mammals, these glands are modified compound alveolar sebaceous glands. Each mammary glands has a teat through which the mammary gland opens out. The area around the teat is dark pigmented, which is called areola mammary. The milk secreted by these glands mainly contains the carcinogen, lactoglobulin, lactalbumin, lactose and fats.

Q.10. What is the skin? List out the functions of the skin.

Sol. Skin is the outermost layer of the human body, which serves as the body’s initial barrier against foreign particles. It is the largest organ of the human body and functions as a barrier between outside and inside environment. Skin is composed of different layers, cells, and tissues.

Functions of the Skin.

  1. It provides shape to the body.
  2. It helps to regulate body temperature.
  3. Being elastic, the skin helps in locomotion.
  4. The perineal gland secretes a sex attractant pheromone.
  5. It protects the body from the pathogens and keeps them away so that they do not enter into the skin and cause any harm.
  6. The skin acts as a respiratory organ, sensory organ, absorptive organ, secretory organ, nutritive organ, excretory organ, storage organ, synthetic organs, etc.

Q.11. Describe the glands associated with eyes and ears.

Sol. The different glands associated with eyes and ears are:

Meibomian glands.

  1. They are modified sebaceous glands and are also called tarsal glands.
  2. They are found within the inner side of the eye-lids.
  3. They secrete an oil substance, which keeps the eye moist.

Glands of sizes.

  1. They are modified sebaceous glands.
  2. They are associated with the hair follicles of the eyelashes.
  3. Their oily secretion lubricates the eyelashes.

Ceruminous glands.

  1. They are modified sweat glands.
  2. The cerumen is a type of carbohydrates.
  3. The cerumen makes the tympanums waterproof.
  4. They are found in the external auditory meatus and they secrete ear wax, which is also called the cerumen.

Q.12. What are scent glands? Explain where these glands are found along with their functions.

Sol. Scent glands are exocrine glands found in most mammals. These scent glands are found near the rectum in the perineal region of the Perineal glands, such as the skin, breast ear and also within the eyelids.

These glands function by secreting viscous fluid, which contains pheromones and other semiochemical compounds. In the breast it secretes milk, in the ear, it forms earwax, in the skin, it functions as scent glands. It is formed by the modification of the sebaceous glands and function by secreting a pheromone, which acts as a sex attractant.

Q.13. Brief out the structure of the dermis.

Sol. The layer present beneath the epidermis of the skin is called the dermis. It originates from the embryonic parietal mesoderm. It is situated below the epidermis and it is 2 to 3 times thicker than the epidermis. It is composed of collagen fibres and yellow elastic fibres, which are made up of fibrous connective tissues. The dermis consists of blood vessels, collagen, nerves, fat, and smooth muscle fibres, hair follicles, cutaneous receptors, etc.

The dermis consists of two main layers:

Papillary layer

  1. It is the outer layer of the dermis.
  2. It forms rete pegs within the epidermis.
  3. The collagen fibres are less in the papillary layer.
  4. It contains blood vessels and other sense organs.

Reticular layer.

  1. It keeps the skin stretched.
  2. It has more collagen fibres.
  3. It is situated below the papillary layer.

Q.14. Define the following terms: Hair follicle, Hair root, Hair papilla and Hair shaft.

Sol.

Hair follicle.

The basal part of the hair, embedded in the dermis and forms sac-like structure. This is known as the hair follicle. The wall of the follicle composed of two main layers:

Outer fibrous layers of the dermis and Inner cellular layer of the epidermis.

Hair root.

The basal cells of the hair follicle divide actively and the root of hairs are formed by them. The hair root is embedded in the dermis.

Hair papilla.

A hollow pit is found at the base of the hair follicle in which the blood capillaries of the dermis form a dense bunch. This bunch is known as hair papilla. The supply of nutrients to the roots are carried by the blood capillaries of this papilla. Inside the follicle, the upper root part of the papilla is swollen as a tumour to form a bulb.

Hair shaft.

The solid part of the hair coming out from the dermis is known as the hair shaft. It is the dead part of the hair because reaching up to this part, the hair cells become keratinized. Cuticle, Cortex and Medulla are three parts of the hair shaft.

Q.15. Define Perineal glands, sebaceous glands and ceruminous glands.

Perineal glands.

Sol. These are the modified glands of the sebaceous glands. These glands are formed near the anus and urogenital aperture. This is an apocrine type of gland. They function by secreting odour substance, or these are known as a scent glands.

Sebaceous glands.

The sebaceous glands are found near the hair roots and hair follicles, which are formed from the folding of the epithelium of the follicles. These glands open in the follicle.

These oil glands are found all over the body but are absent on palms and soles.

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

Ceruminous glands.

These glands are found in the skin of external auditory meatus. They are coiled, tubular and modified sweat glands. These glands combine with the sebaceous glands and secrete earwax, which is called the cerumen. It protects the ear from the tympanum

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