Human A&P, Ch. 5

Integumentary System

• Most visible & largest organ system

• Protection from the environment

• Thermoregulation

• Excretes some waste products

• Lipid storage

• Immune response (1st line of defense against pathogens)

• Sense stimuli: temperature, pressure, touch, & pain

The Integumentary System has _____ tissue types.

All

Keratinocytes

Dead/dying

• Most common cell

• Produce keratin

Melanocytes

• Pigment cells

• Produce melanin

What are the 4 layers of the Epidermis (thin skin)? What is the layer only found in thick skin?

1. Stratum Corneum

2. Stratum Lucidum (thick skin only)

3. Stratum Granulosum

4. Stratum Spinosum

5. Stratum Basale

Stratum Basale

The deepest, basal layer

• Melanocytes

• Merkel cells: touch sensors

• Basal cells: become keratinocytes

• Attachment to basal lamina

Stratum Spinosum

• Keratinocytes have now developed

• Melanocytes (squid-looking)

• Langerhans: trigger immune response (find & attack pathogens)

Stratum Granulosum

Last layer where cells have nuclei

• Keratinocytes start making keratin & keratohyalin

• Fully mature cells start making keratin (water-proof protein). Blocks water from coming in & leaving the cell.

• Callus formation

Stratum Lucidum

Only found in thick skin

• Stacks of dead/dying cells

• High amounts or keratin

• Cells lack organelles & nuclei

Stratum Corneum

Dead cells

• Most superficial layer

• Sebaceous & sweat glands maintain these cells

Epidermal Ridges

Finger prints

• Generated by the presence of dermal papillae

• Valleys: epidermal ridges

• Peaks: dermal papillae

What factors influence skin color?

• Thickness of stratum corneum (thicker = lighter skin)

• Dermal blood supply

  • Blushing: red color hemoglobin

  • Pallor: anemia, drop in BP

  • Bruise: hematoma in skin

• Carotene: yellow-orange (dietary)

Melanin

Brown, yellow-brown, & black

• Produced by melanocytes

• Synthesized & stored in melanosome

• Melanosome enter keratinocytes

• The more melanin you have, the more resistant you are to UV damage

What does excessive exposure to UV do? (3)

1. Sunburn

2. Skin cancer

3. Damage to fibrocytes

   1. Premature wrinkling

   2. Abnormal connective tissue (leathery skin)

What are the 2 layers of the Dermis?

1. Papillary layer

2. Reticular layer

Papillary Layer

Loose connective layer

• Dermal papillae

• Capillaries

• Axons of neurons

• Attachment to epidermis

Reticular Layer

Dense irregular connective tissue

• Hair follicles

• Sweat glands

• Sebaceous glands

Collagen fibers provide ______ ______.

Tensile strength

Elastic fibers allow skin to ______ & ______.

Stretch & recoil

What are stretch marks?

Broken reticular fibers

• Due to pregnancy & weight gain

• Skin doesn’t recoil; causes wrinkles & creases.

What are tension lines?

Collagen & elastic fibers organized in a parallel pattern.

• Making an incision along a tension line can significantly reduce scarring.

Hypodermis (Subcutaneous Layer)

Not technically considered a part of the Integumentary System

• Help stabilizes Integumentary System

• Consists of: adipose tissue & major blood vessels

• Due to location of vessels: hypodermic needles & subcutaneous injections

Hypodermis accessory structures (3)

1. Hair follicles

2. Exocrine glands

3. Nails

   1. Also includes mammary & ceruminous glands

Sub-papillary Plexus: blood vessels

Smaller blood vessels

Cutaneous Plexus: blood vessels

Main arteries & veins

Nerve fibers

• Controls blood flow to skin

• Adjusts gland secretion rates

• Monitors sensory receptors

Proprioception

Allos us to know what our limbs are doing w/o having to look at them.

Tactile corpuscles (receptor)

Light touch receptors

Ruffini corpuscles (receptor)

Stretch receptors

Lamellar corpuscles (receptor)

Deep pressure & vibration receptors

Hair follicles & hair: function

• Thermo-regulation (can dissipate sweat)

• Secondary sex characteristic

• Protection from UV light

• Insulation

• Contraction of arrector pili muscles; goose bumps

Hair shaft

Non-living, visible portion of hair

Hair root

Portion of hair in follicle being formed; anchors hair

Hair follicle

Organ that form hair

Hair papilla

Nerve & blood supply; supports matrix

Hair matrix

Basal cells that divide to become hair

Types of Hair: Vellus

Covers most of body; lacks a medulla

Types of Hair: Terminal

Head, eyebrows, eyelashes

Types of Hair: Hair Color

• More melanin → darker hair

• Decreased production → gray hair

• Lack of melanin in hair shaft → white hair

• Influenced by: genetics, hormones, & environmental factors

Types of Hair: Hair Shape

Based on follicle shape

• Circular follicle: straight

• Oval follicle: wavy

• Flat follicle: curly

Growth & replacement of hair

Active stage (2-5 years) → resting stage → stays in place → brushing hair/shedding → hair becomes a club hair → leaves head → increases productivity of follicle → regrows hair

Hair grows about ___ ___ per day

0.33 mm

What are the 2 main categories of glands in skin?

1. Sebaceous (oil) glands

2. Sweat glands

   1. Apocrine glands

      1. Ceruminous glands

      2. Mammary glands

   2. Eccrine glands

Sebaceous glands

Make sebum

• Sebum: lipid mixture

• Lubricate epidermis & hair

• Antimicrobial properties

• No glands on palms or soles

• High concentration on forehead, face, & upper back

Sebaceous follicles

Large sebaceous glands, no hair

Apocrine sweat glands

What we think of as a standard/classic sweat gland

• Active at puberty (“human musk glands”), produce an odorous secretion

• High density in armpit & areola

• Secretions can contain pheromones

• Eccrine secretion

Eccrine sweat glands

Found all over body

• High concentrations on palms & soles (b/c those areas lack sebaceous glands)

• Sweat (thermo-regulation, waste excretion, antimicrobial activity)

• Eccrine secretion

Nails

Provides protection for distal-most phalanges

• Made of keratin