Chapter 5: The Integumentary System

What are the parts of the integumentary system?

1. The skin

2. Accessory organs

   1. Hair

   2. Oil glands

   3. Sweat glands

   4. Nails

   5. Arrector pili muscles

   6. Mammary gland

What are the 4 functions?

1. Protection

2. Sensory function

3. Thermoregulation

4. Vitamin D synthesis

What types of tissues does the skin have?

• Epithelial

• Connective

What happens when it is hot and you are exercising?

• Dermal blood vessels dilate to lose heat

• Blood circulates close to surface in capillaries

• Sweat glands release sweat to cool the skin

What happens when it is cold?

• Dermal blood vessels constrict to preserve heat

• Blood circulation avoids the skin surface

What are the 3 layers of the skin?

1. Epidermis

2. Dermis

3. Hypodermis

Epidermis

• Outermost layer of the sun

• Keratinized, stratified squamous epithelium

• 4-5 layers

• Avascular

Dermis

• Middle layer of the skin

• Fibrous connective tissue

• 2 layers

Hypodermis (subcutaneous layer)

• Deepest layer of the skin

• Loose connective tissue (areolar connective and fat tissue)

• Vascularized

What are the 5 layers of the epidermis?

1. Stratum corneum

2. Stratum lucidum

3. Stratum granulosum

4. Stratum spinosum

5. Stratum basale

Stratum Corneum

• 15-30 layers of dead cells

• Sheds off as new cells come

• Renewed in a month

Stratum Lucidum

• Only present in thick skin

• Only in palms, soles, and digits

• Dead, flattened cells

Stratum Granulosum

• 3-5 layers

• Flatter cells

• Large amounts of proteins accumulate in lamellar granules = “keratinization“

  • Keratin and keratohyalin

Stratum Spinosum

• Shiny in appearance in histology

• Desmosomes between the cells

Stratum Basale

• Deepest

• Single layer of basal cells (stem cells)

• New cells push others upward

What are the cells of the epidermis?

1. Keratinocytes

2. Melanocytes

3. Dendritic cells/Langerharns cells

4. Tactile cells

5. Merkel cells

Keratinocytes

• Produce keratin

• Protect and waterproof

Melanocytes

• Produce melanin

• Protects keratinocytes from UV damage

Dendritic cells/Langerharns cells

• Immune cells

• Phagocytose foreign material

Tactile cells

• Sensory reception

Merkel cells

• Have mechanoreceptors

Cleavage lines

• Formed by collagen fibers

• Consideration for surgeries

What are the 2 layers of the dermis?

1. Papillary layer

2. Reticular layer

Papillary layer

• Loose connective tissue (areolar)

• Capillary loops, free nerve endings

Reticular layer

• Dense, fibrous connective tissue

• Well vascularized

• Has…

  • Hair follicles

  • Eccrine (sweat) glands

  • Sebaceous (oil) glands

  • Nerves

  • Blood and lymphatic vessels

Meissner corpuscle

Light touch

Pacinian corpuscle

Pressure

Merkel cells (nerve)

Touch

Ruffini corpuscle

Touch, pressure

Free nerve endings

Pain, itch, temperature

Eccrine sweat gland

• Thermoregulation

• Sudoriferous glands - water sweat glands

• Hypotonic and mostly water, salt, antibodies, traces of metabolic waste, dermicidin (an antimicrobial peptide)

Apocrine sweat gland

• Pheromone response

• Water, salts, organic compounds that make the sweat thicker (bacteria decompose it and smell) in armpits and genitals

Ceruminous

• Modified sweat gland

• Found in lining of ear canal

• Secrete cerumen

  • Sebum and dead epithelial cells

  • Protective function

Acne

• Over-productive sebaceous glands

• On areas of the skin rich in sebaceous glands (face and back)

• Puberty associated hormonal changes

Pallor

• Unusual paleness of the skin

• Low RBC count (anemia), low blood pressure

Cyanosis

• Low oxygenation of hemoglobin

• Lung/airway disorders

Jaundice

• Heme turnover bilirubin buildup

• Liver disorders

Erythema

• Unusual reddening of the skin

• Allergy, skin inflammation, fever, high BP

Bruises

• Clotted blood under the skin

• Broken capillaries due to bumps/falls

Arrector pili muscle

• Smooth muscle attached to hair root

• Contract to cause piloerection

• Causes goosebumps

• Used for thermoregulation and defense

Sebaceous glands

• Produces sebum

• Sebum —> waterproofs hair, slow bacterial growth

Hair anatomy

Hair follicle in epidermis includes..

• Hair shaft at surface

• Hair root below the surface

Functions of the hair

• Protects the skull from the sun (head)

• Traps particles, allergies, microbes (eyelashes, nose)

• Prevents sweat from dripping into the eyes (eyebrows)

• Detection of insects and substances

• Insulates

Lanugo

Fetal hair

Vellums

Fine, thin body hair

Terminal hair

• Eyebrows, eyelashes, and hair on scalp

• Axillary and pubic hair

• Adult males: facial hair of trunks and limbs

Fingernails

• Accessory structure

• Protects the ends of digits

• Dig, scratch, claw, and grab

Moles

• Large masses of melanocytes

• Range from benign accumulations of melanocytes to melanomas

Melanoma

• Uncontrolled growth of melanocytes

• Develops from a mole

• Most fatal of all skin cells

Squamous cell carcinoma

• Affects the keratinocytes of the stratum spinosum

• Found on the scalp, ears, and hands

Basal cell carcinoma

• Affects stem cells in the stratum basale of the epidermis

• Found on the head, neck, arms, and back due to sun exposure

• Readily cured if caught early and treated

1st degree burn

• Burn that affects epidermis

2nd degree burn

• Burn that affects epidermis and a portion of the dermis

• Swelling, painful blistering

3rd degree burn

• Burn that extends into epidermis and dermis

• Destroys the tissues, nerve endings, and sensory function

4th degree burn

• Most severe burn, affecting the underlying muscle and bone

• Cannot be repaired by the body

• Excision, amputation, skin grafting