Human Skin Receptors and Vitamin D

Questions and Answers

What is the primary function of sebaceous glands in the skin?

They secrete keratin for skin strength.

They protect against UV radiation.

They lubricate the skin surface and hair. (correct)

They help regulate body temperature.

Which sensory receptor is primarily responsible for detecting light touch within the skin?

Merkel’s Corpuscle (correct)

Hair follicle receptors

Free nerve endings

Pacinian Corpuscle

What role do Langerhans cells play in the skin?

They support skin hydration.

They synthesize vitamin D.

They initiate an immune response. (correct)

They store fat for insulation.

How is vitamin D synthesized in the body?

From ergosterol when exposed to UV light Signup and view all the answers

Which of the following is NOT a function of the skin?

Producing red blood cells. Signup and view all the answers

What process occurs in the skin to help regulate increased body temperature?

Blood vessels in the dermis dilate Signup and view all the answers

Why does the skin act as a blood reservoir?

It houses 1/3 of blood vessels in the body. Signup and view all the answers

Which of the following statements about the skin's role in excretion is true?

Skin does not contribute to excretion. Signup and view all the answers

What can cause rickets in children, related to skin function?

Inadequate exposure to sunlight for vitamin D production. Signup and view all the answers

Which type of materials can penetrate the skin effectively?

Lipid-soluble materials Signup and view all the answers

What is the role of the hypodermis?

It provides insulation and stores fats. Signup and view all the answers

What is the primary pigment responsible for skin color variation?

Melanin Signup and view all the answers

Which body process is NOT directly regulated by the skin?

Circulation of blood Signup and view all the answers

Which of the following statements about the skin's immune function is true?

Epidermal dendritic cells prevent the entrance of harmful elements. Signup and view all the answers

In response to cold temperatures, which change occurs in the skin?

Blood vessels constrict to retain heat. Signup and view all the answers

What component of sweat contributes to its role in thermoregulation?

Water Signup and view all the answers

Where is melanin primarily located in the body?

Epidermis Signup and view all the answers

Which statements about the absorption of substances through the skin are correct?

Lipid-soluble materials and toxins can penetrate the skin. Signup and view all the answers

What contributes to the yellow-orange pigment in the skin?

Carotene Signup and view all the answers

What condition results from the inability to produce melanin?

Albino Signup and view all the answers

Which factor does NOT influence melanin production?

Dietary habits Signup and view all the answers

What skin condition involves the loss of melanocytes and causes irregular white spots?

Vitiligo Signup and view all the answers

What pigment in red blood cells contributes to the red color of the skin?

Hemoglobin Signup and view all the answers

In which of the following conditions would individuals have a tendency to burn easily when exposed to sunlight?

Albinism Signup and view all the answers

What is the primary function of the stratum basale?

To produce keratinocytes through cell division Signup and view all the answers

Which of the following characteristics applies to the stratum spinosum?

It has 8-10 layers of polyhedral keratinocytes with spines Signup and view all the answers

What happens to the nuclei and organelles in keratinocytes undergoing apoptosis?

They degenerate and the cells can no longer perform metabolic functions Signup and view all the answers

Which type of cells are primarily found in the stratum basale?

Stem cells Signup and view all the answers

What type of cells provide strength and flexibility in the stratum spinosum?

Keratinocytes with desmosomes Signup and view all the answers

What is the role of melanocytes in the epidermis?

To produce melanin, which contributes to skin pigmentation Signup and view all the answers

What structure connects the keratinocytes in the stratum basale to the basement membrane?

Hemidesmosomes Signup and view all the answers

What is the state of cells in the outermost layer of the epidermis?

They are fully dead and lack organelles Signup and view all the answers

Which of the following is not a derivative of the skin?

Hairs Signup and view all the answers

Which of the following is not a function of hair?

Initiates sweat glands Signup and view all the answers

Which of the following structures do not make up the major regions of the hair shaft?

Hair follicle Signup and view all the answers

What structure is located at the base of each hair follicle and houses the hair papilla?

Bulb Signup and view all the answers

What piece of muscle contracts to pull the hair shaft during cold or fright, causing goosebumps?

Arrector pili muscle Signup and view all the answers

Which layer of the hair shaft is the outermost layer?

Cuticle Signup and view all the answers

Which part of the hair is immediately deep to the shaft and penetrates the dermis?

Root Signup and view all the answers

What is the primary composition of hair?

Dead, keratinized epidermal cells Signup and view all the answers

Study Notes

Sensory Receptors in Skin

Free nerve endings in the epidermis and dermis detect pain, heat, and cold.
Pacinian corpuscles are responsible for sensing deep pressure and vibration.
Merkel’s corpuscles are sensitive to light touch.
Hair follicle receptors detect hair movement, contributing to the sensory function of the skin.

Vitamin D Production

Ultraviolet (UV) rays activate a precursor molecule in the skin to synthesize Vitamin D.
Enhanced absorption of calcium and phosphate in the intestines supports bone metabolism and muscle function.
Ergosterol in the skin converts to calcitriol, the active form of Vitamin D, after synthesis in the liver.

Temperature Regulation

Skin maintains a normal body temperature of 37°C.
Increased body temperature causes dermal blood vessels to dilate, facilitating heat loss via radiation, convection, conduction, and evaporation (sweating).
Decreased body temperature leads to blood vessel constriction, reducing blood flow and conserving heat.

Excretion and Absorption

Sweat includes water, salt, and trace amounts of urea, uric acid, and ammonia; the skin does not significantly contribute to excretion.
It absorbs lipid-soluble substances efficiently (e.g., vitamins A, D, E, K, oxygen, carbon dioxide).
Toxic materials, such as organic solvents and heavy metals, can be absorbed through the skin.

Secretion

The skin secretes substances such as sebum, an oily material from sebaceous glands, which lubricates skin and hair.
Sweating cools the body through sensible perspiration.

Immunity

The epidermis contains immune cells, specifically epidermal dendritic cells (Langerhans cells), which phagocytize pathogens and cancer cells, helping initiate immune responses.

Blood Reservoir

Skin contains approximately one-third of the body's blood vessels, acting as a blood reservoir.

Skin Functions Overview

Skin protects against microbial invasion and environmental damage, prevents dehydration, acts as a sensory organ, regulates temperature and electrolyte balance, and synthesizes Vitamin D.
The hypodermis stores fat and acts as a cushion, providing insulation.

Layers of the Epidermis

Stratum corneum consists of dead keratinocytes undergoing apoptosis, marking the transition to living layers.
Stratum spinosum contains multiple layers of keratinocytes with thorn-like spines contributing to skin strength and flexibility.
Stratum basale is the deepest layer, featuring stem cells and melanocytes that produce melanin, determining skin color.

Skin Pigmentation

Melanin creates skin color variations from pale yellow to black; primarily produced by melanocytes.
Carotene, a yellow-orange pigment and precursor of Vitamin A, contributes to the color found in the stratum corneum and underlying layers.
Blood flow and hemoglobin contribute to skin tone; all races have a similar number of melanocytes.

Albinism and Vitiligo

Albinism is the inability to produce melanin, resulting in pale skin, hair, and eyes, and increases sensitivity to sunburn.
Vitiligo involves loss of melanocytes, leading to irregular white patches on the skin, possibly due to immune system issues.

Hair Structure

Hair comprises columns of dead, keratinized epidermal cells.
The hair shaft is the visible part of the hair, while the root penetrates deeper into the skin.
Hair follicles consist of internal and external root sheaths, housing the hair bulb where growth occurs.
Arrector pili muscles cause hair to stand upright (goosebumps) during stress or cold.

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Description

Explore the fascinating world of human skin receptors that detect various stimuli such as pain, heat, and touch. This quiz will also cover the synthesis of Vitamin D in the skin activated by sunlight. Test your knowledge on these crucial functions of the skin.