BIOL20 - Ch 5 The Integumentary System

Add together to study Unit 1 Lecture Exam

Organs include

• skin

• its accessory structures

  • hair

  • nails

  • glands

  • blood vessels

  • muscles

  • nerves

Functions of the skin

1. protection

2. thermoregulation: maintains temp

3. converts inactive vitamin D —> active

4. provides sensory info

5. maintains homeostasis

Structure: layers

1. Epidermis - most superficial layer

2. Dermis - a layer deep to the epidermis

3. Hypodermis - subQ (subcutaneous layer), not a layer of skin, composed of areolar and adipose skin

Epidermis

4 major types of cells:

1. keratinocytes - waterproof skin

2. melanocytes - give pigment to absorb UV light

3. intraepidermal macrophages (aka langerhans cell) - eat big debris/germs

4. tactile epithelial cells (aka Merkel cell) - tell body when something is pushing through epidermis

Layers of the skin - Thin skin

4 layers

1. Stratum corneum

2. Stratum granulosum

3. Stratum spinosum

4. Stratum basale

Layers of the epidermis - thick skin

1. Stratum corneum

2. Stratum lucidum

3. Stratum granulosum

4. Stratum spinosum

5. Stratum basale

Stratum corneum

• dead flat layer of keratinocytes

• thick in thick skin, thin in thin skin

Stratum lucidum

ONLY in thick skin (eg. palms, feet)

• doesn’t grow hair

• layer lacks cell nuclei + organelles

• dark line layer

Stratum granulosum

has lamellar granules

Stratum spinosum

• 3-10 layers of keratinocytes

• cells have intermediate filaments w/ keratin

• attached by desmosomes

• largest epidermal layer

Stratum basale

• deepest layer, rests on basal lamina

• cell division primarily occurs here

• formed daughter cells undergo keratinization + move up to superficial layer

Thick skin

covers the palms, palmar surfaces of digits and soles

• hairless skin

Thin skin

covers all body regions excepts the palms, palmar surfaces of digits, and soles

• hairy skin

Skin pigments

Melanin - produced by melanocytes in the stratum basale

Hemoglobin - red pigment in RBC

Carotene - yellow-orange pigment stored in corneum and adipose tissue

Dermis

composed of CT containing collagen + elastic fibers

• contains blood vessels, lymph vessels, nerves, and other structures like hair follicles and sweat glands

Layers of dermis

1. Papillary layer - areolar CT

2. reticular layer - dense irregular CT

Hypodermis

• subQ layer

• attaches skin —> underlying tissue + organs

• consist of well-vascularized, loose, areolar CT, and adipose tissue

Hair + 3 types

composed of dead, keratinized epidermal cells

• have sensory mechanisms

1. Lanugo - covers fetus

2. terminal - long, coarse, heavily pigmented hairs (normal hair)

3. vellus - short, fine, pale hairs (peach fuzz)

Hair structures

• shaft - above skin surface

• follicle - below level of skin

• root - penetrates into dermis

  • epithelial root sheath

  • dermal root sheath

• arrector pili muslce

Skin glands - 4 types

1. Sebaceous (oil) gland

2. eccrine sweat glands

3. Apocrine sweat gland

4. cerumious glands

Sebaceous (oil) glands

connected to hair follicles

• look like popcorn bubble

Eccrine v. Apocrine sweat glands

Eccrine - the most numerous, all over body

Apocrine - located mainly in hairy skin areas, stinky sweat

Ceruminous gland

modified sweat glands in ear canal

Nails

• made of keratinized epidermal cells

• extension of epidermis

• protects furthest extensions of body (digits)

Integumentary system’s role in homeostasis

• regulating body temperature through sweating and blood vessel dilation/constriction

• protecting the body from environmental damage

• preventing water loss

• synthesizing vitamin D

• providing sensory information to the nervous system to respond to external stimuli