Chapter 5: Integumentary System

Key study point: - Functions of the Integumentary system - Components of Integumentary system - Components of the Epidermis - Components of the Dermis - Types of Perspiration - Types of Glands - Types of Cells - Types of Proteins - Accessory Structures - Abnormalities and Skin Conditions - Clinical/Medical Applications

What are the functions of the Integumentary System?

1. Protection

2. Excretion

3. Temperature maintenance

4. Nutrient storage: stores

5. Vitamin D3 synthesis

6. Sensory detection

Characteristics of the Integumentary system

• largest organ

• selectively permeable

Vitamin D synthesis:

• ultra violent light from the sun hits the skin

• passes through the melanin sunscreen

• and causes chemical change in blood.

• leading to the formation of Vitamin D

★ Vitamin D is necessary for the body to absorb calcium

What does the integumentary system consist of?

1. The cutaneous membrane

2. Accessory structures

3. Subcutaneous layers

What does Cutaneous Membrane consist of?

Epidermis and Dermis

Hypodermis

Adipose tissue that absorbs shock & insulates

• Subcutaneous layer below the skin

• Not part of skin

• Anchors skin to underlying structures (muscles)

What is the Epidermis? Why is it called that?

Keratinized stratified squamous epithelium

• Skin cells are usually called stratified squamous cells, but in the Epidermis they are filled with keratin (a waxy protein) and are called Keratinized epithealium.

What are the Layers of the Epidermis?

1. Stratum Corneum (superficial)

2. Stratum Lucidum (only in thick skin)

3. Stratum Granulosum

4. Stratum Spinosum

5. Stratum Basale/Germinativum (deepest)

Stratum Corneum (Horny layer)

20 to 30 layers (thick layer) of dead keratinocytes

• superficial

Functions:

• Protect deeper cells from environment and water loss (water resistant)

• Protect from abrasion and penetration

• Barrier against biological, chemical, and physical assaults

Stratum Lucidum (clear layer)

Few rows of dead keratinocytes

• Only in thick skin

• Superficial to the Granulosum

Stratum Granulosum (granular)

Consists of alive keratinocytes that are undergoing a great deal of physical changes, turning them into the tough outer cells of the epidermis

• Cells above this layer die

Stratum Spinosum (prickly layer)

Thick cell layers that contain keratinocytes, melanin granules, and has the highest concentration of dendritic cells and desmosomes

Stratum Basale/Germinativum (basal layer)

Deepest epidermal layer and is the site of mitosis.

• A single row of stem cells that are actively mitotic

• attached to the dermis

Apoptosis

Controlled cellular suicide

• Nucleus and Organelles break down, Plasma Membrane thickens

• Cells change from Stratum Basale to Stratum Corneum

Cells of the Epidermis

Melanocytes: epithelial cells that synthesize the pigment melanin

Keratinocytes: produce the fibrous protective protein called keratin

Dendritic cells: macrophages that help activate the immune system

Tactile/Merkel cells: associated with sensory nerve endings

Dermis

strong, flexible connective tissue and is well supplied with blood vessels, nerves, and lymphatic vessels

Layers of the Dermis

1. The Papillary Layer

2. The Reticular Layer

The Papillary Layer

Superficial layer that contains blood vessels and nerves

• forms dermal papillae that give rise to fingerprints

• very thin

Dermal papillae

Superficial projections

• contain capillary loops, touch receptors, & free nerve endings

The Reticular Layer

Contains bundles of collagen and elastic fibers responsible for the strength of the skin

• very thick

• forms cleavage and flexure lines

Elastin in Elastin fibers

a protein that permits stretching and recoiling of the skin

Collagen fibers

cause cleavage lines that are important to surgeons

• Incisions parallel to cleavage lines gap less and heal more

  readily

What is skin color determined by?

melanin, carotenes, and hemoglobin

Melanin

A pigment synthesized by Melanocytes

Carotene

Yellow to orange pigment that can be converted to vitamin A

• gathers in stratum corneum

Cyanosis

Oxygen starved skin

• Blue skin color

• Low oxygenation of hemoglobin in the skin

Erythema

redness

• Fever, hypertension, inflammation, allergy

Pallor

blanching (pale skin)

• Anemia, low blood pressure

Jaundice

yellow skin coloration

Bruises

clotted blood beneath skin

What is insensible perspiration?

water loss due to evaporation of fluid that has penetrated the skin

What is sensible perspiration?

water excreted by sweat glands

An albino lacks the ability to produce what?

melanin

Appendages/Accessories of the Skin

• Hairs and hair follicles

• Nails

• Sweat glands

• Sebaceous (oil) glands

Hair

Composed of the shaft and the root

• has 3 layers of keratinized cells:

  • medulla: inner core

  • cortex: middle layers

  • cuticle: outer layer

Shaft

Visible part of hair that sticks out of the skin

Root

Part of hair embedded in the skin

Hair follicle

where hairs originate

• composed of the root and shaft

Hair cuticle

layer of hard keratin that coats the hair

• a dead protective layer

Hair bulb

Hair follicle receptor with sensory nerve endings (touch receptors)

• The hair matrix:

Different hair colors are caused by what?

Melanocytes

Nails

Made of hard keratin

• have free edge, a nail plate attached to the skin, and root embedded in the skin

Where does nail production occur?

The nail root

The nail cuticle

overlies the root

The nail bed and the nail matrix

The nail matrix is located in the nail bed and is responsible for nail growth

Eccrine/Merocrine sweat glands

Produce true sweat

• abundant on palms of hand, forehead, and soles of feet

• Secretion of these glands are sympathetic nervous system

• Used to prevent overheating

Apocrine sweat glands

Produce a fat and protein-rich true sweat

• Become active at puberty

Ceremonious glands

Modified apocrine glands found lining the ear canal

• secrete earwax aka cerumen

Mammary glands

Modified sweat glands that secrete milk

Sebaceous (Oil) Glands

Secrete sebum and are all over the body, except soles and palms

• function as Holocene glands: they secrete oil into hair follicle or to a pore

Keratin

A waxy, protective protein of hair, nails, and skin

Dermatitis

Skin inflammation that involves the papillary layer

Scar tissue is the result of..

Large numbers on Collagen fibers and very few blood vessels in an injured area

Skin can regenerate because of what?

Stem cells in both the epithelial and connective-tissue after injury

Stretch marks occur when…

the skin is so stretched that it exceeds its elastic limits

Dendritic cells

help activate the immune system

Keratinocytes

produce the fibrous protective protein called keratin

Tactile/Merkel cells

associated with sensory nerve endings