Skin Structure and Functions

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Questions and Answers

What is the outermost superficial region of the skin?

Subcutaneous Tissue

Dermis

Epidermis (correct)

Hypodermis

What is the function of the skin that involves receptors for temperature, touch, pain, and more?

Thermoregulation

Sensation (correct)

Vitamin D synthesis

Nonverbal communication

What is the percentage of body weight composed by the skin?

20%

15% (correct)

10%

What is the deepest region of the skin?

Hypodermis Signup and view all the answers

What is the function of the skin that involves the production of vitamin D?

Vitamin D synthesis Signup and view all the answers

What is the layer of tissue below the dermis, but not part of the skin?

Subcutaneous Tissue Signup and view all the answers

What is the function of the skin that involves facial expressions and social acceptance?

Nonverbal communication Signup and view all the answers

What is the total area covered by the skin?

1.5 to 2.0 m2 Signup and view all the answers

What is the function of melanocytes in the epidermis?

To produce the brown pigment melanin Signup and view all the answers

What is the main characteristic of thick skin?

Thick epidermis with no hair follicles or sebaceous glands Signup and view all the answers

What is the function of Langerhans' cells in the epidermis?

To help activate the immune system Signup and view all the answers

What is the main characteristic of the papillary layer of the dermis?

Thin zone of areolar tissue with rich blood vessels Signup and view all the answers

What is the outermost layer of the hair?

Cuticle Signup and view all the answers

What is the main characteristic of the reticular layer of the dermis?

Dense, irregular connective tissue Signup and view all the answers

What is the function of Merkel cells in the epidermis?

To function as touch receptors Signup and view all the answers

What is the consequence of stretching the skin due to pregnancy or obesity?

Tears in the collagen fibers Signup and view all the answers

What is the function of the bulge in the hair structure?

It is the attachment site for the arrector pili muscle Signup and view all the answers

What is the main function of nails?

To improve grooming and picking apart food Signup and view all the answers

Which type of sweat gland is most numerous in adult skin?

Merocrine sweat glands Signup and view all the answers

What is the function of sebum?

To keep skin and hair from becoming dry, brittle, and cracked Signup and view all the answers

What is the function of ceruminous glands?

To produce earwax Signup and view all the answers

What is the main function of mammary glands?

To produce milk for nursing Signup and view all the answers

Where are apocrine sweat glands typically located?

In the axilla and groin areas Signup and view all the answers

What is the purpose of the acid mantle of the skin?

To inhibit bacterial growth Signup and view all the answers

What is the difference between insensible perspiration and diaphoresis?

Insensible perspiration is not visible, while diaphoresis is Signup and view all the answers

What is the function of the piloerector muscle?

To contract and cause hair to stand upright Signup and view all the answers

Study Notes

Skin (Integument)

Consists of three major regions: Epidermis, Dermis, and Hypodermis
Functions of the skin:
- Resistance to trauma and infection (Keratin, Defensins, Acid mantle)
- Barrier functions (water, UV radiation, harmful chemicals)
- Vitamin D synthesis (skin carries out the first step, liver and kidneys complete the process)
- Sensation (skin is an extensive sense organ, receptors for temperature, touch, pain, and more)
- Thermoregulation (thermoreceptors, vasoconstriction/vasodilation, perspiration)
- Nonverbal communication (facial expression, importance in social acceptance and self-image)

Skin Tissue

The skin is the body's largest and heaviest organ
Covers 1.5 to 2.0 m2, composes 15% of body weight
Layers:
- Epidermis: stratified squamous epithelium
- Dermis: deeper connective tissue layer
- Hypodermis: connective tissue layer below dermis (not part of skin, but associated with it)
Skin thickness ranges from 0.4mm on the eyelid to 6.0 mm on the heels of the feet

Cells of the Epidermis

Types of cells:
- Keratinocytes: produce the fibrous protein keratin
- Melanocytes: produce the brown pigment melanin
- Langerhans' cells: epidermal macrophages that help activate the immune system
- Merkel cells: function as touch receptors in association with sensory nerve endings

The Dermis

Papillary layer: superficial zone of dermis, allows for mobility of leukocytes and other defense cells
Reticular layer: deeper and thicker layer of dermis, consists of dense, irregular connective tissue
Stretch marks (striae): tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity

Structure of the Hair and Follicle

Three layers of the hair in cross-section:
- Medulla: core of loosely arranged cells and air spaces
- Cortex: constitutes bulk of the hair, consists of several layers of elongated keratinized cells
- Cuticle: composed of multiple layers of very thin, scaly cells that overlap each other
Hair is divisible into three zones along its length:
- Bulb: a swelling at the base where hair originates in dermis or hypodermis
- Root: the remainder of the hair in the follicle
- Shaft: the portion above the skin surface

Nails

Fingernails and toenails: clear, hard derivatives of stratum corneum
Composed of thin, dead cells packed with hard keratin
Functions:
- Improve grooming, picking apart food, other manipulations
- Provide a counterforce to enhance sensitivity of fleshy fingertips to tiny objects

Cutaneous Glands

Five types of glands:
- Merocrine sweat glands
- Apocrine sweat glands
- Sebaceous glands
- Ceruminous glands
- Mammary glands
Merocrine sweat glands:
- Most numerous skin glands (3-4 million in adult skin)
- Especially dense on palms, soles, and forehead
- Simple tubular glands
- Watery perspiration that helps cool the body
Apocrine sweat glands:
- Locations: groin, anal region, axilla, areola, beard area in men
- Inactive until puberty
- Ducts lead to nearby hair follicles
- Produce sweat that is milky and contains fatty acids
- Respond to stress and sexual stimulation
- Believed to secrete pheromones—chemicals that can influence behavior of others
Sebaceous glands:
- Flask-shaped and have short ducts opening into hair follicles
- Holocrine secretion style
- Sebum: oily secretion of sebaceous glands
- Keeps skin and hair from becoming dry, brittle, and cracked
Ceruminous glands:
- Simple, coiled, tubular glands in external ear canal
- Their secretion combines with sebum and dead epithelial cells to form earwax (cerumen)
- Keeps eardrum pliable, waterproofs the canal, kills bacteria, and makes guard hairs of ear sticky to help block foreign particles from entering auditory canal
Mammary glands:
- Milk-producing glands that develop only during pregnancy and lactation
- Modified apocrine sweat glands
- Rich secretion released through ducts opening at nipple

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Description

This quiz covers the three major regions of the skin, including the epidermis, dermis, and hypodermis, as well as the skin's functions such as resistance to trauma and infection, barrier functions, and vitamin D synthesis.