Integumentary System (Skin)

Functions:

1. Protection2. Regulation of Body

Temperature/Blood reservoir3. Immunity4. Sensation5. Secretion6. Synthesis of Vitamin D

Organization Outer Layer:Epidermis (Epithelium) Inner Layer: Dermis (Connective Tissue) Subcutaneous Layer: Hypodermis

(adipose and areolar CT)

II. Hypodermis

A. Consists of connective tissue: adipose and areolar

B. Is also called the SubQ or Subcutaneous layer

C. It’s main purpose is to attach skin to underlying structures

III. SkinA. Dermis

A. Dermis

1. Reticular fibers are the main fibers present2. Reticular Layer: main layer of dermis

a. Deep or superficial:deepb. Composed of:dense irregular connective tissue, adipose, hair follicles, nerves, oil glands, ducts of sweat glands.c. Responsible for cleavage or tension lines: collagen fibersd. When the dermis ruptures it may produce stretch marks

3. Papillary Layera. named for:Dermal Papillae: contain capillaries, nerve endings touch receptors (Meisner’s corpuscles), Merkels discsPapillae are finger like projections that indent the epidermis to create finger printsb. composed of:areolar loose connective tissue

B. Epidermis1. Epidermal Cells

a. Keratinocytes: 90% of epidermal cells, produce keratin that helps to protect and waterproof skinreplaces top layer of cells every 2-4 weeks

b. Melanocytes:found in dermisproduces melanin: pigment for skin and hair

colorabsorb uv rays from sun

c. Merkel Cells:deepest layer of epidermisassociated with sensory nerve endingsfunction in touch sensation

d. Langerhans Cells:associated with immune system macrophages in epidermis

2. Stratum Basale: deepest layer of epidermis

a. This is composed of: single layer of columnar cells with 25% of the cells being melanocytes.

b. Anchors this layer to the basement membrane: collagen

c. Produces new cells by the process of mitosis

3. Stratum Spinosuma. This layer is composed of: cuboidal cells; 8-10 layers

thick,lagerhan’s and melanocytes.b. The spine like appearance of the cells is due to:desmosomes

(proteins that link plasma membranes together.

4. Stratum Granulosuma. This layer is composed of:flat

granulated cells b. Contains protein granules.c. The nucleus and organelles are

degenerating and the cell is beginning to die.

5. Stratum Luciduma. This layer consists of clear dead

squamous cells.b. Only found in palms of hands and

soles of feet. “thick skin”

6. Stratum Corneum: most superficial layera. This layer consists of dead (Keratinized) stratified

squamous epitheliumb. Keratin: a protein that “water proofs” the skin

Review

7. The epidermis consists of: 8. Most cells of the epidermis are called:9. New cells are formed in: 10. What happens to the cells as they

move superficially through the layers of the epidermis?

11. Keratinization: the process where the protein keratin builds up in a cell as it’s organelles degnerate and the cell dies.

C. Thick and thin skin

1. 5 epithelia strata/layers2. Palms and soles3. Protect and provide friction4. Stratum lucidum5. Thin6. Thin7. Separation between the layers of

the epidermis

D. Skin Color1. Melanin

a. Melanin is a pigment that determines the color of skin. There are two types one that is more red one more black/brown the combination of the two determines one’s skin color.

b. Melanin is produced by melanocytes in the epidermis (stratum basale)

c. Melanin enters keratinocytes as it is transported across a cell membrane.

d. Melanin production is determined by:1. Genetics2. Age3. Exposure to sun

e. Genetics determines the amount and color of melanin produced.f. Hormones usually increase melanin production during pregnancy.g. Exposure to UV light increases production and amount of melanin

in skin.

2. Carotene

a. Is a orange/yellow pigment commonly found in vegetables/carrots

b. Excess carotene accumulates in the skins palms and soles.

c. This gives the skin a yellow discoloration.

3. Hemoglobin

a. Blood flowing through the skin gives it a red/rosy color.

b. Cyanosis: bluish coloration of skin due to lack of oxygen.

IV. Accessory StructuresA. Hair

1. Define terms:a. Lanugo: fine hair that develops on an unborn

baby covering the entire body. It is shed approx. 4 weeks before they are born

b. Vellus hairs: short thin colorless hairs, typically 1cm long (top of lip, hands, feet)

c. Terminal hairs: hair on head, in men sometimes over other parts of body due to increased hormones

2. Hair structure

a. Hair shaft is found above the skins surface.

b. Hair root is below the surface.

3. Hair Growth

a. During the growth stage: Terminal hair on your head grows approx. 1.25 cm per month

b. At the end of resting stage: a new hair pushes through the follicle and the old hair is shed.

4. Hair Color

a. Color is due to the amount of melanin

b. As we age we stop producing melanin in our hair root. Genetics determines when this occurs.

B. Muscles1. Arrector pili: a bundle of smooth muscle

that is associated with hair2. When arrector pili contract hair stands on

end causing goose bumps3. Arrector pili contract when you are cold or

from the stress of fright4. This responses aides animals in keeping

warm and in scaring away whatever frightens them (evolutionary adaptation)

C. Glands1. Sebaceous Glands (oil gland)

a. All over body except for palms and soles, associated with hair follicles.

b. Structurally they are simple epitheliumc. These glands produce oil/sebum which is rich in fat

(triglycerides)d. Sebum functions

1. Minimize water loss, preventing brittle hair and cracked skin

2. Inhibit bacterial growth

e. Black Heads: enlarged sebaceous glands due to excess sebum; occur during puberty due to increased activity

2. Sweat glands/Sudoriferous glands

a. Two types of sweat glands1. Eccrine (Merocrine) glands2. Apocrine glands

b. Eccrine glands are most common.c. Eccrine glands are found through out skin except for lips,

nail bedsd. Sweat regulates body temperature.e. Apocrine glands are found in armpit, pubic region, areolar

of breast.f. Apocrine glands become active under emotional stress and

sexual excitement.g. Body odor from sweat is a result of a mixture of water,

salt, urea, sugar, amino acids, ammonia

3. Ceruminous Glands

a. Located in external auditory meatus (ear canal= outside ear to ear drum)

b. Secrete wax/cerumin to provide protection

D. Nails: densely packed keritinized cells.

1. Two functions of nails:a. protect fingersb. help manipulate objects

V. Summary of Integumentary system

A.Describe six ways that the integumentary system is involved in protection.1. Keratincytes protect & waterpr00f cells 2. Sebaceous glands-minimize water l0ss and inhibit bacterial gr0wth3. Sweat glands pr0duce sweat to regulate b0dy temp4. Cerumion0us glands secrete wax to pr0tect ear canal5. Fingernails pr0tect fingers.6. Skin layers pr0tect deeper tissues, bl00d vessels, and 0rgans underneath.

B. Sensations Touch/Pressure Receptors : Merkel’s

discs/cells Pain Receptors: Nerve Endings Heat and cold receptors: Nerve

Endings

C. Temperature Regulation (Homeostasis)

Increased Environmental Temperature/Exercise

1. Thermorecpetors detect stimulus

2. Brain (hypothalamus)

3. Sweat glandsBlood vessels

Message sent to

Sends message to

Increase rate of perspiration

Blood vessels in dermis dilate

Increase rate of heat loss

Decrease metabolic rate

Decreased environmental temperature

Blood vessels constrict in dermis Skeletal muscles contract

involuntarily (shivering) Increased metabolic rate

All of these assist in increasing body temperature

D. Vitamin D production

1. Raises blood levels of a. calciumb. phosphorus

2. Vitamin D requires the skin to be exposed to sun.

E. Excretion

1. Waste products in sweat:a. waterb. urea (form of ammonia)c. salt

2. The quantity of waste products in sweat is variable depending on a persons hydration.

VI. Effects of Aging on the I.S.

A. Two reasons the skin is more easily damaged as we age:

1. Fewer Langerhan cells are produced, decreased immunity

2. Death of cappillaries and blood vessels in the area.

Effects of Aging on the I.S. B. Skin sags and wrinkles due to decrease

in elastin and collagen production.C. Skin becomes drier due to decrease

sebum/oil, sweat production.D. The number of functioning melanocytes

typically decreases: Gray hair, more susceptible to burn

E. Age Spots: due to UV exposure.