The Integumentary System

Skin, Hair, Glands, Nails

Anatomy & Physiology Ch. 5

Learning Targets

• Identify the anatomical structures of the integumentary system.

• Explain the role of skin and all of its accessory organs.

• Describe the diseases/disorders

of the integumentary system.

Human skin…..

• is the largest organ.

• it serves as a protective covering.

• it helps regulate body temp.

• it prevents water loss.

• it houses sensory receptors.

• it excretes wastes.

Integumentary System• Three layers

– Skin

1. Epidermis 2. Dermis

3. Hypodermis (Subcutaneous layer)

• Adipose

– Accessory Structures

• Hair - Nails -sebaceous glands

• sweat glands (4 types)

• The skin is composed of 3 layers; the epidermis (superficial), the dermis (middle) and the hypodermis (deep).

Epidermis

• composed of stratified squamous.• lacks blood vessels – no vascularization.• prevents water loss by secreting protein,

keratin.• keratinization of cells takes about 2 weeks.• No innervation – lacks nerves.

Keratinized stratified squamous

Epidermis (cont)

• Contains cells called melanocytes that produce melanin (absorbs light energy & protects deeper cells); melanin gives skin its color.

Melanocyte

Skin Color

• All people have similar numbers of melanocytes.

• Skin colors result from differences in the amount of melanin that melanocytes produce and the distribution & size of the melanin granules.

• Albinism - inability to produce melanin.

Dermis• Is made up of two layers.

• Top layer (papillary layer) composed of areolar or loose connective tissue.

• Bottom layer (reticular layer) composed of dense connective tissue.

• Well vascularized & innervated.

• Also contains accessory structures such as; hair follicles, sebaceous glands, and sweat glands.

Hypodermis

• Made of adipose tissue and some loose connective tissue.

• Insulates body from losing too much heat.

• Also known as the subcutaneous layer.

• Men and women store subcutaneous fat differently.

Hair…• Composed of epidermal cells that have

keratinized and died .

• Hair color is determined by the type and amount of pigment the melanocytes produce.

• Arrector pili muscle - surrounds hair follicle & contracts when a person is cold or frightened. What are “goose bumps’?

Sebaceous Glands…

• a gland located around the hair follicle which secretes its contents when contracted by the arrector pili.

• secrete an oily mixture of fat and cellular debris called sebum which keeps the hair and skin soft, pliable, and waterproof.

• this is why hair gets oily when not washed.

Nails…• Composed of dead stratified squamous

epithelial cells which are extremely keratinized.

• Nail production occurs at the nail root which is underneath the skin and proximal to the visible nail.

• Nails are basically clear and appear pink over skin because of underlying blood vessels.

Sweat Glands (Exocrine Glands)

1. Eccrine Glands…

• respond to elevated body temp. due to heat or exercise.

• cool by allowing water to be evaporated from skin lowering temp.

• common on forehead, neck, and back.

Sweat Glands (Exocrine Glands)

• release fluids thru pores.

• gland located in dermis but releases fluid through tube onto the top of the epidermis.

• sweat = water + salts (mainly sodium chloride) and other wastes.

Where do you have the most eccrine glands?

Sweat glands (cont.)

2. Apocrine glands….

• active when a person is emotionally upset, frightened, or in pain.

• found under the armpits and in the groin.

• sweat is food for bacteria, which just increases the bad smell.

Other Integumentary Glands

- Ceruminous glands - secrete ear wax to trap foreign particles before reaching the ear drum.

Why does ear wax smell bad?

- Mammary glands - secrete milk.

Regulation of Body Temperature• Regulation is important b/c heat affects

the rate of metabolic reactions.

• When temp rises above the set point, dermal blood vessels dilate (get larger) and glands secrete sweat.

• When temp drops below the set point, dermal blood vessels constrict (get smaller) and glands become inactive.

WHAT TYPE OF FEEDBACK IS THIS?

Healing of Wounds• Skin injuries trigger inflammation; blood vessels

dilate and become more permeable, forcing fluids to leave the blood vessels and enter the damaged tissues. WHAT TYPE OF FEEDBACK IS THIS?

• Dilated blood vessels supply the damaged cells with more oxygen and nutrients; this speeds healing.

• More platelets are supplied to clot blood.• More white blood cells needed to fight infection.

Page 170-1

Skin cancer• There are three main types of skin cancer; basal

cell carcinoma, melanoma, and squamous cell carcinoma.

• Both UVA and UVB contribute to skin cancer.

• Basal cell carcinoma is the most prevalent affecting over 2 million Americans a year.

• Basal cell carcinoma develops in the cells of the basement membrane typically due to sun exposure.

Melanoma• Melanoma is the most deadly form of skin cancer

while also being the most rare.

• 120,000 new cases are diagnosed in the U.S. each year.

• If caught early it is usually treatable, however if it spreads to other parts of the body treatment becomes much more difficult.

• Melanoma develops in the melanocytes located in the epidermis.

• Melanoma usually appears black or brown.

Squamous cell carcinoma• Squamous cell carcinoma is the second

most prevalent type of skin cancer.

• It originates in squamous cells of the epidermis.

• It is more prevalent in areas exposed to the sun and in people with lighter skin.

• Twice as many men as women develop this type of skin cancer.

• http://www.skincancer.org/skin-cancer-video.html