Integumentary System Questions in English

(C) Snakes periodically shed the outer scaly layer of their skin,which is known as moulting or ecdysis. This process involves the shedding of the cornified cells of the epidermis. The entire skin is often shed in a single piece.

(C) Coverts are small feathers located at the base of the flight feathers (remiges) on the wings and tail of a bird. Their primary function is to cover the gaps between the bases of the larger feathers,providing a smooth aerodynamic surface and insulation.

(B) The subdermal fat,also known as the subcutaneous layer or hypodermis,is composed primarily of adipose tissue.
Its primary function in mammals is to act as a heat-insulating layer (thermal insulation) to prevent heat loss from the body,thereby helping to maintain a constant body temperature (homeostasis).
While it also provides some cushioning against mechanical shocks,its most significant physiological role in endothermic animals is thermoregulation.

(B) The correct answer is $B$.
In the $stratum \text{ } lucidum$ layer of the epidermis, $keratohyaline$ granules are dissolved and transformed into a protein called $eleiden$.
$Eleiden$ is a clear, oily substance that makes the cells appear semitransparent, shiny, and waterproof.

(A) Nails,hair,and the epidermis of the skin are derivatives of the $Ectoderm$ germ layer.
During embryonic development,the $Ectoderm$ gives rise to the nervous system,the outer layer of the skin (epidermis),and associated structures like nails,claws,and hair.
Therefore,the correct option is $A$.

(C) In a zonary placenta,the chorionic villi are restricted to one or two transverse bands or zones around the middle of the blastocyst.
This type of placenta is characteristic of carnivores (e.g.,cats,dogs,tigers,lions) and some herbivores (e.g.,elephants).
Therefore,both $(a)$ and $(b)$ are correct.

(D) Juvenile hormone,when present at the late stage of larval development,prevents metamorphosis into the adult form.
Instead,the larva continues to grow,resulting in the development of a giant larva (an immature adult form).
These giant larvae are unable to undergo normal maturation and typically die without reaching the reproductive adult stage.

(C) The $Stratum$ $germinativum$, also known as the $Stratum$ $basale$, is the deepest layer of the epidermis.
This layer consists of a single row of cuboidal or columnar cells that are actively undergoing mitosis.
These cells continuously divide to produce new cells that are pushed outward to replace the cells shed from the surface of the skin.

(C) The correct answer is $C$.
Keratin is a tough,fibrous,and insoluble structural protein.
As cells in the $stratum$ $corneum$ move toward the outer surface of the skin,they undergo a process of keratinization where the cytoplasm is replaced by keratin,which provides strength and waterproofing to the skin cells.

(D) The fat layer located below the dermis is known as the hypodermis or subcutaneous layer.
This layer consists primarily of adipose tissue,which acts as an excellent insulator against heat loss,helping the body maintain a stable internal temperature.
Therefore,the correct option is $D$.

(B) The correct answer is $(b)$.
The dermis is divided into two layers: the papillary layer and the reticular layer.
The papillary layer is the upper,folded part of the dermis that consists of minute,finger-like projections known as dermal papillae.
These dermal papillae project into the epidermis,creating an interlocking mechanism that increases the surface area for nutrient exchange and provides mechanical stability between the dermis and the epidermis.

(C) The term '$Jack$ of all trades' refers to someone or something that is capable of performing many different tasks or functions. The integumentary system (skin and its derivatives) is called the '$Jack$ of all trades' because it performs a wide variety of essential physiological functions,including protection,thermoregulation,sensory reception,excretion,and synthesis of vitamin $D$.

(D) The skin performs multiple vital functions in the human body:
$1$. It acts as a thermoregulatory organ by controlling heat loss through sweating and vasodilation/vasoconstriction.
$2$. It aids in the excretion of metabolic waste products like urea,salts,and water through sweat glands.
$3$. While it does not store food in the same way as adipose tissue,it is involved in the synthesis of Vitamin $D$ and acts as a protective barrier.
Given the options provided,the skin is involved in both thermoregulation and excretion,making $D$ the most comprehensive answer.

(D) The skin is the largest organ of the body and acts as a complex system.
$1$. Maintenance of body shape is supported by the structural integrity of both the epidermis and dermis.
$2$. Protection from foreign harmful bodies (pathogens,$UV$ radiation,mechanical injury) is provided by the stratified squamous epithelium of the epidermis and the connective tissue of the dermis.
$3$. Secretion (such as sweat and sebum) is carried out by glands located within the skin layers.
Therefore,these functions are collectively performed by the skin as a whole.

(C) $Melanin$ is a dark or brown pigment that occurs naturally in the hair,skin $(stratum \, germinativum)$,and in the iris and the choroid of the eye. Therefore,it is found in both the $stratum \, germinativum$ layer of the epidermis and the hair.

(D) The mammalian skin consists of the epidermis and the dermis. The dermis is further divided into the papillary layer and the reticular layer. The deeper part of the dermis,often referred to as the hypodermis or subcutaneous layer,is composed of loose connective tissue and is heavily infiltrated with adipose tissue (fat cells).

(C) . Adipose tissue acts as an insulator because it is a poor conductor of heat. It forms a layer of fat beneath the skin that reduces heat loss from the body to the external environment,thereby helping to maintain body temperature.

(D) The correct answer is $D$. The skin is often referred to as the "Jack of all trades" because it performs a wide variety of essential physiological functions.
These functions include protection against pathogens and mechanical injury, regulation of body temperature (thermoregulation), excretion of waste products through sweat, synthesis of Vitamin $D$, and sensory perception (touch, pain, temperature).

(B) Taxidermy is a process in which the whole skin,including both epidermis and dermis,is preserved by using certain chemicals. This technique is commonly used to preserve the outer appearance of animals for display or study purposes.

(A) The epidermis is the outermost layer of the skin. It is composed of several layers of cells. The $Stratum \text{ } corneum$ is the most superficial layer of the epidermis, consisting of dead, keratinized cells that provide a protective barrier against the environment.

(B) The correct answer is $B$. When a person performs hard manual labor with their hands,the constant friction and mechanical stress stimulate the basal layer of the epidermis to increase cell division. This leads to the formation of a thickened layer of keratinized cells,known as the stratum corneum,which acts as a protective barrier against further injury. Therefore,such individuals develop a thick epidermis on their palms.

(C) Brown adipose tissue,also known as brown fat,is a specialized type of adipose tissue that plays a crucial role in thermogenesis (heat production).
It is found in human babies to help them maintain body temperature,as they have a high surface-area-to-volume ratio and limited shivering capacity.
It is also found in hibernating animals,such as certain rodents,to provide warmth during periods of dormancy.
Therefore,both $(a)$ and $(b)$ are correct.

(A) Perspiration in higher animals is helpful in maintaining body temperature at a constant level by losing heat at a high environmental temperature. Essentially,perspiration is a process that serves as a method for cooling the body.

(D) The integumentary system,which includes the skin and its derivatives,serves several vital functions in an organism.
$1$. Protection: It acts as a physical barrier against mechanical injury,pathogens,and ultraviolet radiation.
$2$. Excretion: It helps in the elimination of metabolic wastes through sweat glands.
$3$. Absorption: It can absorb certain substances,such as lipid-soluble compounds,and plays a role in the synthesis of Vitamin $D$ upon exposure to sunlight.
Therefore,all the listed options are functions of the integument.

(B) The term $Corium$ is a synonym for the $Dermis$,which is the thick layer of living tissue below the $Epidermis$. It forms the true skin,containing blood capillaries,nerve endings,sweat glands,hair follicles,and other structures.

(B) The correct answer is $(b)$. The dermis is the vascular layer of the skin. It contains a dense network of capillary blood vessels and has rich vasomotor innervation,which helps in thermoregulation and providing nutrients to the overlying epidermis,which is avascular.

(A) The hair follicle consists of several layers. The inner root sheath of the hair follicle is composed of three layers: the Henle's layer (outermost),the Huxley's layer (middle),and the cuticle of the inner root sheath (innermost). Therefore,Huxley's layer is a component of the wall of the hair follicle.

(A) The $Stratum$ $germinativum$,also known as the $stratum$ $basale$,is the deepest layer of the $epidermis$ of the skin.
It consists of a single layer of cuboidal or columnar stem cells that are actively dividing by $mitosis$ to produce new keratinocytes.
These cells continuously migrate upward to replace the cells shed from the surface of the skin.

(D) The correct answer is $D$. The skin plays a vital role in the regulation of water and body temperature through the process of sweating (perspiration). Sweat glands secrete water,salts,and small amounts of urea,which helps in maintaining water balance and cooling the body.

(A) The $Stratum Malpighii$, also known as the $Stratum basale$ or basal layer, is the deepest layer of the $Epidermis$ in the skin.
It consists of a single layer of cuboidal or columnar cells that are actively dividing to produce new skin cells.

(B) The Pacinian corpuscles (also known as $Vater-Pacinian$ corpuscles) are specialized sensory receptors found in the skin and other tissues.
These corpuscles act as mechanoreceptors that are primarily sensitive to deep pressure and high-frequency vibration.
Therefore,they are responsible for detecting pressure stimuli.

(D) The correct answer is $D$. The epidermis of the skin,specifically the $stratum$ $germinativum$ (basal layer),is highly regenerative. This layer contains stem cells that continuously divide to produce new cells. These new cells migrate upward to replace the cells in the upper layers of the epidermis that are lost due to constant friction and wear and tear.

(C) Antlers are branched structures that are primarily composed of true bone. They develop from the pedicles on the frontal bone of the skull. While the velvet covering the growing antler is skin (dermis and epidermis),the mature antler itself is a solid structure of bone.

(B) The stratum germinativum,also known as the stratum basale or stratum malpighi,is the deepest layer of the epidermis.
It rests directly on the basement membrane.
It is composed of a single layer of actively dividing columnar or cuboidal epithelial cells.
Therefore,the correct option is $B$.

(D) The skin of mammals consists of two main layers: the epidermis and the dermis.
The epidermis is derived from the ectoderm,while the dermis is derived from the mesoderm.
Since none of the options ($A$,$B$,or $C$) correctly identify the mesodermal origin of the dermis,the correct answer is $D$.

(D) The correct answer is $D$. The $stratum \text{ } corneum$ is the outermost layer of the epidermis, consisting of dry, dead, keratinized cells. These cells are packed with the protein keratin, which is a tough, water-resistant (waterproof) substance. This layer acts as a barrier that prevents excessive water loss from the body through evaporation and protects underlying tissues from dehydration.

(C) The fur of a $Rabbit$ acts as an insulating layer that traps air,which is a poor conductor of heat. This layer helps in maintaining the body temperature by preventing excessive heat loss to the environment. If the $Rabbit$ is fully shaved,this insulating layer is removed,causing the animal to lose body heat rapidly. Consequently,the skin will have difficulty in regulating body temperature,leading to potential hypothermia.

(A) Adipose tissue is a specialized type of loose connective tissue.
It consists of adipocytes (fat cells) that are specialized for the storage of fats.
These cells are found primarily in the subcutaneous layer (beneath the skin),around internal organs,and in the bone marrow.
Therefore,they are classified as connective tissues.

(A) The $Malpighian$ layer,also known as the $stratum$ $basale$ or $stratum$ $germinativum$,is the deepest layer of the epidermis.
It consists of actively dividing cells that possess the power of mitosis.
These cells continuously divide to produce new cells,which then migrate upward to replace the cells lost from the surface of the skin.
Therefore,the correct option is $A$.

(A) The term 'scaled epithelium' refers to squamous epithelium.
$(a)$ The skin is covered by stratified squamous cornified epithelium,which provides protection against mechanical injury and desiccation.
$(b)$ Bowman's capsule is lined by simple squamous epithelium,but it is not typically described as 'scaled' in the same context as the skin.
$(c)$ The wall of the alimentary canal is primarily lined by columnar epithelium.
$(d)$ The windpipe (trachea) is lined by pseudostratified ciliated columnar epithelium.
Therefore,the most appropriate answer in the context of 'scaled' (stratified squamous) epithelium is the skin.

(C) The muscles attached to hair follicles are called $arrector$ $pili$ muscles. When these muscles contract,the hair stands erect (piloerection). This action traps a layer of air near the skin surface. Since air is a poor conductor of heat,this trapped layer acts as an insulator,helping to reduce heat loss from the body and preserve body heat in cold conditions.

(C) $Metachrosis$ is the capability in some animals,including amphibians,to change the intensity of skin colour to blend with the environment. This physiological process allows organisms to camouflage themselves against their surroundings to avoid predators or to facilitate hunting.

(C) $Meissner's$ corpuscles are specialized sensory nerve endings located in the dermis of the skin,particularly in the hairless areas such as the fingertips,lips,and nipples.
These corpuscles function as mechanoreceptors that are sensitive to light touch and gentle pressure.

(A) The epidermis of thick skin,found on the palms of the hands and the soles of the feet,consists of five layers: $Stratum$ $basale$,$Stratum$ $spinosum$,$Stratum$ $granulosum$,$Stratum$ $lucidum$,and $Stratum$ $corneum$.
Among these,the $Stratum$ $lucidum$ is a clear,thin layer of dead cells that is uniquely present only in thick skin (palms and soles) and is absent in thin skin.
However,the $Stratum$ $corneum$ is the outermost layer and is significantly thicker in the palms and soles compared to other parts of the body to provide protection against mechanical stress and friction.
Therefore,the $Stratum$ $corneum$ is the layer that is best developed (thickest) in these regions.

(A) The $Stratum$ $spinosum$ layer of the epidermis is also known as the prickle cell layer.
It consists of $6$ to $7$ layers of polyhedral cells.
These cells possess short,thorn-like cytoplasmic processes that connect adjacent cells,giving them a 'prickly' appearance under a microscope.
Therefore,prickle cells are found in the skin.

(C) The $Panniculus adiposus$ refers to the subcutaneous layer of the skin, which is primarily composed of adipose (fat) tissue. This layer acts as an insulator, a shock absorber, and an energy reserve. Therefore, it is defined as a subcutaneous layer rich in fatty connective tissue.

(C) The whitening or greying of hair occurs because the production of the pigment melanin in the hair follicles stops.
As melanin production ceases,minute air bubbles accumulate in the cortex of the hair shaft in place of the pigment.
Since these air bubbles reflect light,the hair appears white or grey.

(B) The correct answer is $B$. Mammalian skin,particularly the epidermis,is largely impermeable to water. This property is primarily due to the presence of keratin and lipids in the stratum corneum and the transformation of keratohyaline granules into eleidin in the stratum lucidum,which creates a waterproof barrier. This adaptation is crucial for terrestrial mammals to prevent excessive water loss through evaporation.

(A) Collagen is the most abundant structural protein in the human body,forming the primary component of the extracellular matrix in the skin.
It provides structural support,strength,and elasticity to the skin.
When collagen fibres weaken,the skin loses its elasticity and becomes prone to stretching or sagging.
Since collagen is a protein,consuming a diet rich in high-quality protein provides the necessary amino acids (such as glycine,proline,and hydroxyproline) required for the synthesis and maintenance of collagen fibres.
Therefore,protein is the correct dietary component for maintaining skin integrity.

(A) Albinism is a genetic disorder characterized by the partial or complete absence of the pigment $Melanin$ in the skin,hair,and eyes.
$Melanin$ is responsible for providing colour to these structures.
Due to the deficiency of $Melanin$ production,the skin,hair,and iris appear very light-coloured or white.