RBSE Solutions 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
In simple words: Human skin is made up of cells that come from both the ectoderm and mesoderm layers during development. These two layers work together to form all parts of the skin.

🎯 Exam Tip: Remember that different body tissues develop from specific embryonic layers. For skin, the ectoderm forms the epidermis, and the mesoderm forms the dermis.

 

Question 3. Eleiden protein is found in stratum –
(a) granulosum
(b) spinosum
(c) corneum
(d) lucidum
Answer: (d) lucidum
In simple words: The protein eleidin is found in the stratum lucidum layer of the skin. This layer is often seen in thick skin areas like palms and soles.

🎯 Exam Tip: Knowing the unique proteins and characteristics of each skin layer helps identify its specific role and location.

 

Question 4. Keratohyaline protein is found in stratum -
(a) spinosum
(b) granulosum
(c) germinativum
(d) corneum
Answer: (b) granulosum
In simple words: The protein keratohyaline is present in the stratum granulosum layer of the skin. It helps in the process of keratinization, which makes the skin tough.

🎯 Exam Tip: Keratohyaline granules are important for forming keratin, a key protein that gives skin its strength and waterproof properties.

 

Question 5. Skin derivatives are -
(a) Nails
(b) Sweat glands
(c) Sebaceous glands
(d) All of the options
Answer: (d) All of the options
In simple words: Nails, sweat glands, and sebaceous glands are all special parts that grow out of the skin. They are called skin derivatives because they come from the skin itself.

🎯 Exam Tip: Skin derivatives are structures that develop from the epidermis and play various roles, including protection, lubrication, and thermoregulation.

 

Question 6. Sebaceous glands are -
(a) Apocrine
(b) Mesocrine
(c) Holocrine
(d) Acrine
Answer: (c) Holocrine
In simple words: Sebaceous glands are holocrine glands, which means their cells burst to release the oily secretion called sebum. The whole cell forms part of the secretion.

🎯 Exam Tip: Understanding the type of secretion (holocrine, apocrine, merocrine) helps distinguish between different gland functions and structures in the body.

 

Question 7. A barrier layer of the skin is stratum -
(a) corneum
(b) Ludum
(c) granules
(d) spins
Answer: (b) Ludum
In simple words: The stratum lucidum acts as a barrier layer in the skin. It is a clear layer that helps protect the skin.

🎯 Exam Tip: The stratum lucidum is particularly prominent in areas of thick skin, providing extra protection and water resistance.

 

Question 8. Sweat glands are -
(a) Apocrine
(b) Merocrine
(c) Acrine
(d) None of the options
Answer: (c) Acrine
In simple words: Acrine is another name for eccrine sweat glands, which are the most common type of sweat gland. They release a watery fluid directly onto the skin surface to help cool the body.

🎯 Exam Tip: Differentiate between acrine (eccrine), apocrine, and merocrine glands based on their secretion method and primary locations in the body.

 

Question 9. Melanin pigments in the hair are found in -
(a) Cortex
(b) Cuticle
(c) Medulla
(d) All of the options
Answer: (a) Cortex
In simple words: Melanin, the pigment that gives hair its color, is mainly found in the cortex layer of the hair shaft. The amount and type of melanin here determine hair color.

🎯 Exam Tip: The cortex is the primary structural component of hair, and its pigment content is crucial for hair color, while the cuticle provides outer protection.

 

Question 1. Which vitamin is synthesized in the skin?
Answer: Vitamin D.
In simple words: Our skin can make Vitamin D when it is exposed to sunlight.

🎯 Exam Tip: Always specify "Vitamin D" as the full name; just "D" might be unclear to an examiner.

 

Question 2. Where the meibomian glands are found in human skin?
Answer: The inner side of the eyelids.
In simple words: Meibomian glands are located inside our eyelids.

🎯 Exam Tip: Mention the specific location "inner side of the eyelids" to demonstrate precise anatomical knowledge.

 

Question 3. Mammary glands in man are the modification of which gland?
Answer: Modified sebaceous gland.
In simple words: In humans, mammary glands developed from sebaceous glands.

🎯 Exam Tip: Clearly state that mammary glands are modified sebaceous glands, indicating their evolutionary origin.

 

Question 4. Human mammary glands are of which type?
Answer: Apocrine in human beings.
In simple words: Human mammary glands are a type of apocrine gland.

🎯 Exam Tip: Specify "apocrine" as the type of gland, as this classification relates to how their secretions are released.

 

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”.
In simple words: Skin does many different jobs for the body, so it is called a "Jack of all trades."

🎯 Exam Tip: When explaining why skin is called "Jack of all trades," briefly mention some of its diverse functions like protection, temperature regulation, and sensation.

 

Question 6. Which pigment imparts colour to the skin?
Answer: Melanin pigment.
In simple words: Melanin is the pigment that gives skin its color.

🎯 Exam Tip: The key term "Melanin pigment" is essential for full marks, as it directly answers the question.

 

Question 7. The dermis originates from which layer?
Answer: Collagen protein.
In simple words: The dermis layer of the skin is largely made up of a strong protein called collagen.

🎯 Exam Tip: While collagen is a major component, remember that the dermis *originates* from the mesoderm, not collagen itself.

 

Question 9. Name the oily substance secreted by sebaceous glands.
Answer: Sebum.
In simple words: Sebaceous glands make an oily substance called sebum.

🎯 Exam Tip: Sebum is a key term, responsible for lubricating and waterproofing skin and hair.

 

Question 10. Name the muscle responsible for hair movement.
Answer: Arrector pili.
In simple words: The arrector pili muscle makes hair stand up, causing goosebumps.

🎯 Exam Tip: The arrector pili muscles are small muscles attached to hair follicles that contract in response to cold or fear.

 

RBSE Class 12 Biology Chapter 21 Short Answer Type Questions

 

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

• It starts from the embryonic ectoderm.
• It is thickest in body parts that experience a lot of rubbing, like the soles of feet and palms of hands.
• It is very thin in areas like the eyelids and cornea.
• The epidermis does not have nerves or blood vessels.
• It is a stratified epithelium and has five layers.
• These layers are arranged from the inside to the outside as follows.

Stratum Malpighi or stratum germinativum:

• This is the innermost living layer of the epidermis.
• It is made up of a single layer of tall, column-shaped cells.
• These cells constantly divide to create the upper layers of the epidermis.
• This layer pushes into the dermis.
• These inward pushes are called rete pegs.
• This layer also contains some melanocytes, which produce pigment.

Stratum spinosum:

• This layer is located outside the stratum Malpighi.
• It has many layers of branched, multi-sided cells.
• These cells have a hook-like structure.
• This layer helps provide strength to the skin.

Stratum granules:

• It is located just outside the stratum spinosum.
• It consists of 5 to 6 layers of cells that contain granules of keratohyalin protein.

Stratum lucidum:

• It is located outside the stratum granulosum and is made of 3 to 4 layers of living, flat cells.
• These cells contain a protein called eleidin, which is formed from keratohyalin.
• The cells in this layer have no nucleus and are clear.
• It is waterproof and is also known as a barrier layer.

Stratum corneum:

• This is the outermost layer, made up of flat, scale-like cells.
• These cells are dead because they contain dead keratin protein.
• It is the thickest layer of the epidermis, consisting of 8 to 10 layers of cells.
• Its outermost layers are shed continuously.

Keratinization:
The process of forming keratin protein in the epidermis is called keratinization. This process leads to the creation of structures like hair and nails.
In simple words: The epidermis has five main layers, from the deepest living layer (stratum germinativum) that makes new cells, through layers like stratum spinosum, granulosum, and lucidum, to the outermost dead, protective layer (stratum corneum). Keratinization is how skin makes the tough protein keratin.

🎯 Exam Tip: Remember the five layers of the epidermis in order (from deep to superficial or vice versa) and a key characteristic for each, such as cell type or protein content. For diagram questions, draw clearly and label accurately.

 

Question 2. Draw a labelled diagram of V.S. of skin.
Answer:
A labelled diagram of the V.S. (Vertical Section) of mammalian skin is shown in the source as "Fig. 21.1 : Mammalian skin". It depicts various layers of the skin, including the epidermis (with its sub-layers like stratum corneum, lucidum, granulosum, spinosum, and germinativum), the dermis, and associated structures such as hair follicles, sebaceous glands, and sweat glands, along with blood vessels and nerves. Due to the complexity of anatomical drawings, an inline SVG cannot be generated from the given template.
In simple words: The answer shows a detailed drawing of skin layers and parts like hair and glands. It helps us see how skin is built inside.

🎯 Exam Tip: For diagrams, ensure all key structures are clearly drawn and labelled correctly. Practice sketching the V.S. of skin to identify the epidermis, dermis, hair follicle, sebaceous gland, and sweat gland.

 

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

• Hair is found only in the skin of mammals and originates from the ectoderm.
• Hair is located in a hair follicle, which is formed as an invagination (inward growth) of the stratum germinativum layer.
• The base of the hair follicle is shaped like an everted cup, enclosing a hair papilla or dermal papilla. This papilla contains blood vessels and nerves.
• Hair consists of two main parts: the hair shaft and the hair root.
• The cells of the hair root continuously divide, causing the hair follicle to grow.

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

• Huxley's sheath - This is the outer sheath.
• Henle's sheath - This is the inner sheath and is made up of cuboidal cells.
• The exposed part of the hair shaft is dead due to the deposition of keratin protein.

Structurally, the hair shaft has three parts:

1. Cuticle - This is the outermost layer, made up of squamous (flat) cells.
2. Cortex - This is the outer part that contains melanin pigments, which give hair its color. In rabbits, melanin pigments are absent from the hair.
3. Medulla - This is the central part of the hair follicle. The lanugo (fine, soft hair) does not have a medulla.

• The contraction of the arrector pili muscle causes hair to stand upright, a reflex action known as goose flesh or cutis anserina.
• This process is stimulated by the adrenalin hormone.
• Grey hair lacks melanin pigments, and its medulla develops air cavities, which give the hair a shiny appearance.

In simple words: Hair grows from a follicle in the skin. It has a root and a shaft, with inner layers like the medulla and cortex (which gives color) and an outer cuticle. A small muscle makes hair stand up, causing goosebumps.

🎯 Exam Tip: When describing hair structure, ensure you include both the follicular components (papilla, sheaths) and the shaft components (cuticle, cortex, medulla), as well as the function of the arrector pili muscle.

 

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

• These are coiled, tube-shaped glands that open directly to the outside of the skin.
• They secrete sweat, which is mostly water (95%) and 5% other substances like lysozyme, salt, ammonia, and urea.
• Sweat helps to lower body temperature and remove excess salts. The lysozyme in sweat acts as a germ-killer.
• In rabbits, the sweat glands are apocrine.
• In humans, most sweat glands are eccrine or merocrine, but those in the armpits, nipples, and eyelids are apocrine in function.
• Sweat can be thought of as diluted urine. In rabbits, sweat glands are found only at the edges of the lips.
• There are myoepithelial cells around the coiled part of the gland. Sweat is released when these cells contract.

In simple words: Sweat glands are tiny tubes that release sweat onto the skin. Sweat is mostly water, and it helps cool the body down and remove some waste. Some sweat glands also kill germs.

🎯 Exam Tip: When describing sweat glands, highlight their structure (coiled tubular), composition of sweat, and primary functions like thermoregulation and antibacterial action.

 

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

• They are compound alveolar glands that form as an outgrowth from hair follicles.
• They function as holocrine glands, meaning they open to the outside through the hair follicle by releasing whole cells.
• They secrete an oily substance called sebum.
• Sebum makes the skin and hair waterproof. Sebum contains ergosterol, which forms vitamin D when exposed to UV rays from sunlight.

In simple words: Sebaceous glands are small glands connected to hair follicles. They make an oily substance called sebum, which keeps skin and hair soft and waterproof. Sebum also helps make Vitamin D from sunlight.

🎯 Exam Tip: Focus on the holocrine nature of sebaceous glands, the name of their secretion (sebum), and its dual functions: waterproofing and involvement in Vitamin D synthesis.

 

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

• In Prototheria, humans, and other primates, mammary glands are modified apocrine sweat glands. In other mammals, they are modified compound alveolar sebaceous glands.
• Each mammary gland has a nipple (teat) through which the milk gland opens. The dark area around the nipple is called the areola mammary.
• The mammary glands produce milk. Milk mainly contains carcinogens, lactoglobulin, lactoalbumin, lactose, and fats.
• In human beings, there is a pair of mammary glands on the chest.

In simple words: Human mammary glands are special apocrine sweat glands that make milk. Each gland has a nipple for milk release, surrounded by a dark area called the areola. Milk has proteins, sugars, and fats.

🎯 Exam Tip: Note that mammary glands are modified sweat glands and describe their key components (teat/nipple, areola) and the primary content of the milk they produce.

 

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

• Being flexible, the skin aids in movement.
• The skin functions as a respiratory organ, sensory organ, absorptive organ, secretory organ, nutritive organ, excretory organ, storage organ, and synthetic organ.
• It provides shape to the body.
• The perineal glands secrete a sex attractant pheromone.
• The skin is involved in certain processes of the tympanum.

In simple words: Skin helps us move, breathe a little, feel things, and release substances. It shapes our body and helps in scent communication.

🎯 Exam Tip: List at least five distinct functions of the skin, such as protection, sensation, temperature regulation, excretion, and vitamin D synthesis, to demonstrate comprehensive knowledge.

 

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.
In simple words: Keratinization is the process where skin cells make a tough, dead protein called keratin. This process helps form structures like nails and hair.

🎯 Exam Tip: Define keratinization by mentioning the formation of keratin protein and its location in the stratum corneum. Provide examples of common derivatives.

 

Question 9. Write in brief about erector pili muscle.
Answer:
1. Meibomian glands:

• They are modified sebaceous glands, also known as tarsal glands.
• They are found on the inner side of the eyelids.
• They secrete an oily substance that 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 eyelashes.

3. Ceruminous glands:

• They are modified sweat glands.
• They are found in the external auditory meatus and secrete ear wax, also called cerumen.
• Cerumen is a type of carbohydrate.
• Cerumen makes the eardrums waterproof.

In simple words: This answer describes different glands, not the erector pili muscle. Meibomian glands keep eyes moist. Glands of Zeis lubricate eyelashes. Ceruminous glands make earwax to waterproof the eardrum.

🎯 Exam Tip: When faced with a discrepancy between the question and the provided answer, present the answer content accurately. For this question, remember the function and location of Meibomian, Zeis, and Ceruminous glands.

 

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

• They are formed by the modification of the sebaceous glands.
• They are also called scent glands or inguinal glands.
• They are located near the rectum in the perineal region.
• They secrete a pheromone, which acts as a sex attractant.

In simple words: Scent glands, like perineal glands, are found near the rectum. They release a special smell called a pheromone that attracts mates.

🎯 Exam Tip: For scent glands, specify their location (perineal region) and their primary role in secreting pheromones for communication.

 

RBSE Class 12 Biology Chapter 21 Essay Type Questions

 

Question 1. Explain the structure of human skin. Give labelled diagrams.
Answer:
1. Epidermis:

• It originates from the embryonic ectoderm.
• It is thickest in body areas prone to friction, such as the soles and palms.
• It is very thin in delicate areas like the eyelids and cornea.
• The epidermis lacks nerves and blood vessels.
• It is a stratified epithelium with five types of layers.
• These layers are arranged from the inside to the outside.

Stratum Malpighi or stratum germinativum:

• It is the innermost living layer of the epidermis.
• It consists of a single layer of columnar cells.
• These cells constantly divide to form the upper layers of the epidermis.
• This layer pushes down into the dermis.
• These inward projections are called rete pegs.
• This layer also contains melanocytes, which produce melanin pigment.
• These cells contain melanin pigments that give color to the skin.

Stratum spinosum:

• This layer is located above the stratum Malpighi.
• It is composed of many layers of branched polyhedral cells.
• These cells have 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 containing granules of keratohyalin protein.

Stratum lucidum:

• 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 rete 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 & its functions as heat resistant layer.

In simple words: Human skin has three main layers: the top epidermis (which has five sub-layers like stratum corneum and germinativum), the middle dermis (with papillary and reticular layers), and the bottom sub-dermis (containing fat). Each layer has special cells and structures that protect, sense, and regulate the body.

🎯 Exam Tip: For an essay on skin structure, clearly differentiate between the epidermis, dermis, and sub-dermis. Detail the sub-layers of the epidermis and the components of the dermis. While the question asks for diagrams, provide a comprehensive text description if diagrams are not available in the source. If you were to draw, label all key layers and features clearly.

 

Question 3. Describe various cutaneous glands found in the human skin.
Answer: Cutaneous glands are special glands found in the skin. They include:

• Sweat or Sudorific Glands: These glands are shaped like coiled tubes and open directly onto the skin surface. They release sweat, which is mostly water (95%) and a little bit of other things like salts, ammonia, and a substance called lysozyme. This sweat helps cool the body down and remove extra salts. The lysozyme in sweat kills harmful bacteria. For example, rabbits have apocrine sweat glands. In humans, most sweat glands are eccrine or merocrine types. However, glands in areas like armpits, around nipples, and eyelids are apocrine. Sweat is sometimes compared to very diluted urine. In rabbits, these glands are found mainly around the edges of their lips. Special muscle-like cells (myoepithelial cells) surround the coiled part of the gland. When these cells squeeze, they push the sweat out.
• Sebaceous Glands: These glands are complex, sac-like structures that grow out from hair follicles. They work by releasing their whole cells filled with secretion (holocrine), which then break open. They also open out through the hair follicle. They produce an oily substance called sebum. Sebum makes skin and hair waterproof. It contains ergosterol, which turns into Vitamin D when exposed to sunlight's UV rays. This process shows ergosterol in sebum changes into Calciferol (Vitamin D) when exposed to sunlight.
• Ceruminous Glands: These are sweat glands that have changed their structure. They are located in the outer ear canal and produce ear wax, also known as cerumin. Cerumin is a type of sugar molecule (carbohydrate). This ear wax helps make the eardrum (tympanum) waterproof.
• Mammary Glands: In some animals like Prototheria, humans, and other primates, mammary glands are changed apocrine sweat glands. In other mammals, they are modified compound sebaceous glands with many small sacs. Each mammary gland has a nipple (teat) for milk release. The dark area around the nipple is called the mammary areola. Mammary glands produce milk. Milk mostly has various proteins, sugar (lactose), and fats. Humans typically have one pair of mammary glands on the chest.
• Perineal Glands: These glands are changed sebaceous glands. They are also known as scent glands or inguinal glands. They are found near the rectum, in the perineal area. They release a special chemical (pheromone) that attracts mates.
• Meibomian Glands: These are sebaceous glands that have been changed and are also called tarsal glands. They are located on the inside of the eyelids. They produce an oily liquid that keeps the eyes moist.
• Glands of Zeis (Glands of Sizes): These are also modified sebaceous glands. They are connected to the hair follicles of eyelashes. Their oily release helps lubricate the eyelashes.

In simple words: The human skin has different kinds of glands like sweat glands for cooling, sebaceous glands for oil, earwax glands for ear protection, and mammary glands for milk. Each gland has a special job to keep the body healthy and working.

🎯 Exam Tip: When describing glands, always mention their location, type, and the substance they secrete, along with its function. This covers the key aspects an examiner looks for.

 

Question 4. Why skin is called "Jack of all trades"? Explain.
Answer: The skin is called the "Jack of all trades" because it is the body's largest organ and performs many different important functions. Here are its main functions:

• Protection: The skin protects soft body parts from germs, harmful radiation, and physical injuries.
• Prevents Dehydration: It stops the body from losing too much water, which prevents dehydration.
• Temperature Control: It controls body temperature. When the body gets hot, blood vessels in the skin widen (vasodilation) to release heat. When it's cold, vessels narrow (vasoconstriction) to keep heat in. These actions are controlled by nerves and hormones like adrenaline.
• Secretion of Pheromones: Perineal glands release special chemicals (pheromones) that attract mates.
• Ear Protection: Earwax (cerumin) helps protect the eardrum.
• Eye Protection: Glands like meibomian, Zeis, and lacrymal glands work together to protect the eyes.

In simple words: Skin is called a "Jack of all trades" because it does many jobs for the body, like protecting us, keeping us hydrated, controlling body temperature, and even helping with communication and protecting our senses.

🎯 Exam Tip: To explain why skin is a "Jack of all trades," focus on listing and briefly explaining its diverse and vital functions, such as protection, temperature regulation, and sensory roles.