The skin is a remarkably versatile organ that acts as the body’s primary shield. Its most crucial role is to serve as a protective barrier, safeguarding our internal tissues from physical harm, the invasion of harmful germs, and the damaging effects of ultraviolet radiation from the sun. Furthermore, the skin is vital for preventing excessive water loss, keeping our body from drying out, and it houses numerous nerve endings that provide us with the essential sense of touch, allowing us to perceive sensations like pressure, pain, and temperature. This combination of protection and sensory input makes the skin our first line of defense against the external world.
Beyond being a simple barrier, the skin is a master regulator of the body’s internal temperature. When the body becomes too warm, the sweat glands produce sweat. As this moisture evaporates from the skin’s surface, it draws away heat, creating a powerful cooling effect. Simultaneously, the blood vessels near the skin’s surface widen in a process called vasodilation, allowing more blood to flow and release excess heat. Conversely, in cold conditions, these blood vessels constrict to conserve heat, and tiny muscles attached to body hairs contract, causing “goosebumps” in a vestigial response to trap a layer of insulating air.
The skin also performs several other critical functions that are often overlooked. It acts as a minor excretory organ, removing small amounts of water, salts, and urea through sweat. Additionally, the skin plays a role in synthesis; when exposed to sunlight, it produces Vitamin D, which is essential for calcium absorption and bone health. Its layers, the outer protective epidermis and the inner, thicker dermis, work in perfect harmony. The epidermis constantly regenerates and contains melanin for UV protection, while the dermis is a living hub of blood vessels, nerves, glands, and hair follicles, all collaborating to maintain the body’s overall health and equilibrium.
Multiple choice type
Question 1.
If for some reason the sebaceous glands fail to function
- the body will not be able to regulate the body temperature
- the skin will turn darker with more melanin
- the hairs will fail to grow
- the skin will turn dry and rough
Question 2.
Which one pair of two conditions includes both as abnormal conditions of skin pigmentation?
- Leucoderma, Ringworm
- Albinism, Leucoderma
- Baldness, Albinism
- Rickets, Baldness
Question 3.
Which one out of the organs listed below, most actively functions in regulating our body temperature?
- Heart
- Lungs
- Skin
- Stomach
Question 4.
Sweat glands are situated in:
- Epidermis
- Dermis
- Both
- None of the above
Question 5.
The epidermis is highly thickened in:
- Eyelid
- Thigh
- Lip
- Palm
Very short answer type
Question 1.
Name the principal body heat regulating centre in our brain.
Ans:
The principal body heat regulating center in our brain is the hypothalamus .
It functions as the body’s thermostat, monitoring blood temperature and initiating responses (like shivering or sweating) to maintain the core body temperature within a narrow, set range (homeostasis).
Question 2.
Name any one modified sweat gland and any one modified sebaceous gland.
Ans:
The human body has several glands that are modifications of the basic sweat or sebaceous glands to perform specialized functions:
- Modified Sweat Gland: Ceruminous Glands (found in the ear canal, they produce earwax, or cerumen).
- Modified Sebaceous Gland: Meibomian Glands (found in the eyelids, they secrete an oily substance that lubricates the eye and prevents tear evaporation).
Question 3.
Name the skin glands which when inflamed cause acne.
Ans:
The skin glands which, when inflamed, cause acne are the sebaceous glands (oil glands).
Acne occurs when these glands become overactive and the ducts that release sebum (oil) become clogged with dead skin cells and excess oil, leading to inflammation and the growth of bacteria.
Short answer type
Question 1.
State any two functions of the mammalian skin other than those concerned with heat regulation.
Ans:
Here are two important functions of mammalian skin, apart from heat regulation:
- Protection (Barrier Function): The skin acts as the body’s primary physical barrier against the external environment.
- It prevents the entry of harmful microorganisms (bacteria, viruses, fungi) and foreign substances.
- It protects deeper tissues from injury, dehydration (loss of water), and the damaging effects of UV radiation through the production of melanin.
- Sensory Reception: The skin is a major sense organ, packed with millions of specialized sensory receptors (nerve endings).
- These receptors detect various external stimuli, allowing us to perceive sensations such as touch, pressure, pain, and temperature (though temperature perception is distinct from temperature regulation).
Question 2.
1. What is “goose-flesh”?
2. How is goose-flesh brought about?
Ans:
- “Goose-flesh” (or goosebumps, piloerection) is the temporary appearance of numerous small, raised bumps on the skin, resembling that of a plucked goose.
- Goose-flesh is brought about by the contraction of tiny muscles attached to the base of hair follicles.
Mechanism of Goose-Flesh
Goose-flesh is a reflex action triggered by the autonomic nervous system, primarily in response to cold or intense emotional stress (like fear or excitement).
- Muscle Contraction: Each hair follicle has a small, involuntary muscle called the arrector pili muscle.
- Piloerection: When stimulated by nerve signals, these muscles contract, pulling the hair follicle upright and simultaneously raising the surrounding skin into a small bump.
- Evolutionary Purpose: In furry mammals, this reflex fluffs up the coat, trapping an insulating layer of air near the skin to retain heat. For humans, the reflex is vestigial (no longer serving its original purpose) but still occurs in response to the same stimuli.
Question 3.
What is the difference between leucoderma and albinism?
Ans:
| Feature | Leucoderma (Vitiligo) | Albinism |
| Nature | Acquired (develops later in life). | Hereditary/Genetic (present from birth). |
| Cause | An autoimmune condition where the body’s immune system destroys the melanocytes (pigment cells) in affected skin areas. | A genetic mutation that prevents the body from producing melanin or from transporting it correctly. |
| Pigment Loss | Localized/Patchy: Affects specific areas of the skin, resulting in distinct, often spreading, white patches. | Generalized/Total: Affects the entire body, leading to a complete or near-complete absence of pigment in the skin, hair, and eyes. |
| Effect on Eyes | Pigmentation in the eyes is usually normal. | Pigmentation in the iris and retina is usually severely reduced, often leading to vision problems and light sensitivity. |
Question 4.
Name any two glands found in the human skin. State their functions.
Ans:
The human skin contains several types of glands. Two primary glands and their functions are:
- Sweat Glands (Sudoriferous Glands)
- Function: Their main function is thermoregulation (cooling the body). They secrete sweat, a fluid primarily composed of water and salts. As sweat evaporates from the skin’s surface, it removes excess heat, cooling the body down.
- Sebaceous Glands
- Function: They secrete an oily substance called sebum. Sebum lubricates and waterproofs the skin and hair, keeping them supple and preventing them from drying out. It also has mild antibacterial and antifungal properties.
Question 5.
An otherwise normal healthy young man started perspiring while it was intensely cold outside. What could have been one reason for it?
Ans:
An otherwise normal, healthy young man perspiring (sweating) while it was intensely cold outside suggests an issue where his body temperature either rose sharply or his body’s thermoregulation center was triggered by a non-thermal stimulus.
Here is the most likely reason for this occurrence:
The most probable reason is vigorous physical activity, such as intense exercise, running, or heavy labor.
Explanation
When a person engages in strenuous activity, their muscles generate a large amount of metabolic heat as a byproduct of increased cellular respiration (ATP production).
- Core Temperature Rise: Even if the air outside is cold, this massive internal heat generation causes the core body temperature to rise quickly.
- Hypothalamus Trigger: The hypothalamus (the brain’s thermostat) detects this rising internal temperature.
- Sweating Response: To prevent overheating (hyperthermia), the hypothalamus initiates the cooling mechanism: perspiration. The evaporation of sweat is intended to dissipate the excess heat, regardless of the surrounding cold air temperature.
In this scenario, the body is reacting to an internal thermal stress (exercise heat) rather than the external cold environment.
Long answer type
Question 1.
Enumerate in a tabular form the different structures found in the epidermis and dermis of the human skin respectively.
Ans:
| Epidermis (Outer Layer) | Dermis (Inner Layer) |
| Keratinocytes (Main cell type) | Collagen and Elastin Fibers (Provide strength and elasticity) |
| Melanocytes (Produce melanin/pigment) | Blood Vessels (Supply nutrients and regulate temperature) |
| Langerhans Cells (Immune function) | Nerve Endings/Sensory Receptors (Detect touch, pain, temperature) |
| Merkel Cells (Tactile/touch reception) | Hair Follicles (Pocket housing the hair root) |
| Pores (Openings of sweat ducts) | Sebaceous Glands (Produce oil/sebum) |
| Stratum Basale (Innermost layer) | Sweat Glands (Produce sweat/perspiration) |
| Stratum Corneum (Outermost layer) | Arrector Pili Muscles (Cause “goosebumps”) |
| Fat Cells (Adipose tissue) |
Question 2.
Explain the terms “vasodilation” and “vasoconstriction”. How do these processes contribute to temperature regulation of the body?
Ans:
Vasodilation and vasoconstriction are processes that involve the change in the diameter of blood vessels, primarily arterioles, and they are critical mechanisms the body uses to regulate its internal temperature (thermoregulation).
Definitions
- Vasodilation : This is the process where the smooth muscles in the walls of the blood vessels relax, causing the vessels to widen (increase in diameter).
- Vasoconstriction : This is the process where the smooth muscles in the walls of the blood vessels contract, causing the vessels to narrow (decrease in diameter).
Contribution to Temperature Regulation
These processes control the amount of blood flow near the surface of the skin, thereby regulating heat exchange with the environment.
1. Vasodilation (When the Body is Too Hot)
When the body’s core temperature rises above the set point (e.g., during exercise or in a hot environment), the body initiates vasodilation:
- Effect: Blood vessels near the skin widen.
- Heat Loss: This increases the volume of warm blood flowing close to the skin’s surface. Since the surrounding air is usually cooler than the blood, heat is rapidly lost from the blood to the environment via radiation, convection, and conduction.
- Result: This process efficiently cools the body down and helps bring the core temperature back to normal.
2. Vasoconstriction (When the Body is Too Cold)
When the body’s core temperature drops below the set point (e.g., in a cold environment), the body initiates vasoconstriction:
- Effect: Blood vessels near the skin narrow.
- Heat Conservation: This dramatically reduces the blood flow near the skin’s surface.
- Result: Less warm blood reaches the extremities, minimizing heat transfer to the environment. This action conserves heat within the body’s core organs, helping to raise the core temperature back to the set point.
Question 3.
1. How does our skin provide protection to our body against the following?
Entry of germs ____________
2. How does our skin provide protection to our body against the following?
Excessive loss of heat in severe cold ____________
3. How does our skin provide protection to our body against the following?
Entry of harmful ultra-violet rays ____________
Ans:
Here is how your skin protects your body against the specified factors:
- Entry of germs: The skin’s outermost layer, the epidermis, provides a tough, multi-layered physical barrier made of dead, keratinized cells. This unbroken surface is generally impenetrable to most microorganisms. The skin’s surface is also slightly acidic (the acid mantle), which inhibits the growth of many bacteria and fungi.
- Excessive loss of heat in severe cold: The skin conserves heat primarily through vasoconstriction. The blood vessels in the dermis layer narrow (constrict), which reduces blood flow to the skin’s surface. Less blood near the surface means less heat is lost to the cold external environment, keeping the vital organs warmer. Subcutaneous fat tissue beneath the skin also acts as an insulating layer.
- Entry of harmful ultra-violet rays: The skin produces the dark pigment melanin within specialized cells called melanocytes in the epidermis. Melanin acts as a natural sunscreen, absorbing and scattering UV radiation before it can penetrate and damage the DNA in deeper skin cells.
Structured/Application/Skill type
Question 1.
Draw a labelled diagram of the generalized vertical section of the mammalian skin.
Ans:
Question 2.
1. Given below is a diagrammatic sketch of the vertical section of the human skin.
Label the parts numbered from 1 to 9.
2. Given below is a diagrammatic sketch of the vertical section of the human skin.
State one main function of each of the following parts:
Part 2 ___________
Part 3 ___________
Part 4 ___________
Part 9 ___________
Name any one of the above parts which has at least three functions.
3. Given below is a diagrammatic sketch of the vertical section of the human skin.
Part 4 may add to one’s good appearance or the “figure”. State one example of this function which may be common to both men and women.
Ans:
Based on the provided diagram of the vertical section of human skin:
1. Label the Parts Numbered from 1 to 9
- Pore (or Duct Opening)
- Sweat Gland (Coiled secretory part)
- Blood Vessel (Capillary or Artery/Vein)
- Adipose Tissue (Fat layer/Subcutaneous fat)
- Dermis (Layer containing blood vessels, glands, and nerves)
- Epidermis (Outer layer of the skin)
- Stratum Corneum (Dead, outermost layer of the epidermis)
- Hair Follicle (The sheath surrounding the hair root)
- Sebaceous Gland (Oil gland)
2. State Main Function and Multifunctional Part
Here are the main functions of the specified parts:
| Part | Name | Main Function |
| 2 | Sweat Gland | Produces sweat (perspiration) for cooling the body (thermoregulation). |
| 3 | Blood Vessel | Transports nutrients and oxygen to skin cells and regulates body temperature via vasoconstriction/vasodilation. |
| 4 | Adipose Tissue | Insulation (retaining body heat) and energy storage (as fat). |
| 9 | Sebaceous Gland | Secretes sebum (oil) to lubricate the skin and hair, preventing dryness. |
Name any one of the above parts which has at least three functions:
The part that has at least three functions is Part 3: Blood Vessel.
- Transport of Nutrients/Oxygen
- Removal of Waste Products
- Heat Regulation (via widening/narrowing to release/conserve heat)
3. Function of Part 4 in Appearance
Part 4 is Adipose Tissue (Subcutaneous Fat).
Part 4 may add to one’s good appearance or the “figure” by providing contour and smooth curves to the body’s silhouette (e.g., hips, buttocks, and breasts), contributing to the perceived “figure” or body shape.
