A&P Lesson 7 - Integumentary System

Dermatology

Scientific study and treatment of the integumentary system

What is the most vulnerable organ?

skin because it is exposed to radiation, trauma, infection, and injurious chemicals

Integumentary system

Cutaneous membrane of the skin and accessory structures like hair, nails, and glands

skin

Largest/heaviest organ of the body

Two layers of the skin

1. Epidermis

2. Dermis

Is the hypodermis part of the skin?

No the superficial fascia/subcutaneous layer is not

How thick is skin?

0.5 to 6 mm

Thick skin

Covers palms, soles, and corresponding surfaces of fingers and toes (0.5 mm thick epidermis)

Thin skin

Covers the rest of the body (0.1 mm thick)

Differences between thick vs thin skin

1. Thick skin has sweat glands

2. Thin skin has hair follicles, and sebaceous glands

Functions of skin

1. Protection against trauma and infection through KERATIN

2. Vitamin D synthesis

3. Sensation

4. Thermoregulation through blood flow

5. Nonverbal communication

Features of the epidermis

1. Keratinized stratified squamous epithelium

2. Avascular and depends of the dermis

3. Contains sparse nerve endings for touch and pain

4. The most superficial layer

Types of epidermal cells

1. Keratinocytes that make up most cells and synthesizes keratin

2. Stem cells deepest layer

3. Melanocytes synthesize melanin

4. Tactile touch receptors associated with dermal nerve fibers

5. Dendritic phagocytic immune cells

Stratum basale

the basement layer of the epidermis that has some melanocytes and tactile cells

Stratum spinosum

multiple layers of keratinocytes joined by desmosomes/tight junctions that contains defense cells

Stratum granulosum

3-5 layers of fat that kills keratinocytes

Stratum lucidum

Thin layer of thick skin with keratinocytes and eleidin proteins

Stratum corneum

up to 30 layers of dead, keratinized cells to resist absorption/penetration/water loss

How are keratinocytes produced?

Mitosis of stem cells in stratum basale or deep stratum spinosum

lamellar granules

lipid filled formed by flattened keratinocytes

Death of a keratinocyte

After 30-40 days the keratinocyte will reach the surface and exfoliate as dander/dandruff when combined with oil

Calluses

Thick accumulation of dead keratinocytes on hands/feet

epidermal water barrier

in the stratum granulosum formed from lipids from keratinocytes held together by tight junctions

Features of the dermis

1. Connective layer 0.2-4 mm thick

2. Composed of collagen and elastic fibers

3. Has blood vessels, sweat glands, oil glands, and nerve endings

4. Houses hair follicles and nail roots

5. Facial expression muscles attach to the dermis

6. Wavy boundary between this and the epidermis

Dermal papillae

upward finger like dermal extensions

epidermal ridges

downward waves of epidermis

Zones of the dermis

papillary layer and reticular layer

Papillary layer

blood vessel dense zone of thin areolar tissue near the dermal papillae; mobility of defense cells

Reticular layer

Thicker dermis layer made of irregular connective tissue

Striae

stretch marks; tears in the collagen fibers caused by skin stretching

Fibers in the dermis

1. Collagen fibers that are strong and flexible

2. Elastic fibers that allow for flexibility with recoil

Skin turgor

flexibility and resilience of skin caused by H2O content of the skin

Dermatitis

Inflammation of the papillary layer; characterized by pain/itchiness and caused by irritants

Decubitus ulcers

bedsores caused by issues with dermal circulation caused by compression of superficial blood vessels

Melanin

Produced by melanocytes and stored in melanosomes to provide color to the skin

How is UV radiation absorbed?

Melanosomes transfer to keratinocytes so melanosomes cluster around the nucleus

Eumelanin

Dark brown and black skin color

Pheomelanin

Reddish and yellow skin tones

External factors that contribute to skin color

1. UV radiation stimulates melanin synthesis

2. Degree of show-through vessels and white collagen

3. Accumulation of carotene from yellow and orange vegetables

Carotene

Found in yellow/orange vegetables; accumulates in epidermal cells and dermis fatty tissue, produces vitamin A

Nyctalopia

night blindness caused by vitamin A deficiency

Erythema

redness of the skin due to capillary dilation

Pallor

paleness due to decreased blood flow

Albinism

a genetic condition characterized by a deficiency or the absence of pigment in the skin, hair, and irises of the eyes

Vitiligo

white patches on the skin caused by the destruction of melanocytes associated with autoimmune disorders

Jaundice

yellowing of the skin because of bilirubin in blood

Friction ridges

fingerprints formed from dermal papillae; enhances sensitivity and improves grip

Flexion lines

lines on the flexor surfaces of the digits, palms, wrists, elbows; where joint bending occurs

freckles

flat, melanized patches

Mole

elevated, melanized patch, often with hair, that should be monitored as indication of skin cancer

Hemangiomas

Birth marks; patches of discolored skin caused by benign tumors of the dermal capillaries.

Hypodermis

subcutaneous tissue; layer of connective tissue beneath the skin

Characteristics of the hypodermis

1. Contains more areolar and adipose tissue

2. Pads on body and binds skin to below tissue

3. Common site of drug injection b/c of amount of blood vessels

4. Subcutaneous fat composed of adipose tissue

Subcutaneous Fat

subcutaneous tissue that is comprised predominantly of adipose tissue

Characteristics of Subcutaneous Fat

1. energy reservoir

2. thermal insulation

3. thicker in females; thinner in babies and elderly

Accessory organs of the skin

hair, nails, and cutaneous glands

Soft keratin

Makes up stratum corneum of skin

Hard keratin

Makes hair and nails; tougher because of disulfide bridges

Skin turgor test

1. Pinch skin on back of hand

2. Wait for a few seconds to watch for recoil

3. If skin remains elevated that indicates dehydration

Functions of hair

1. Hair receptors alert to parasites

2. Hair on trunk and limbs is vestigial

3. Scalp hair retains heat and protects from sun

4. Pubic and axillary hair indicates sexual maturity

5. Guard hairs protect nasal and ear canals

6. Eyelashes/eyebrows enhance facial expression and nonverbal communication

Vibrissae

Guard hairs in the nostril and ears

Pilus/pili

hair

Hair follicle

Filament of keratinized cells growing from a tube in the skin

What accounts for variation in hair growth?

Difference in texture and pigment

Where does hair not cover?

1. palms

2. soles

3. lateral surfaces and distal segments on fingers and toes

4. lips

5. nipples

6. parts of genitals

Types of hair

1. Downy hair/lanugo

2. Vellus hair

3. Terminal hair

Downy hair

fine, unpigmented hair on fetus in the last 3 months of development

Vellus hair

Fine hair that replaces luango by birth (2/3 of hair of female 1/10 for male)

Terminal hair

Long, coarse, pigmented hair that makes

• eyelashes, eyebrows, and scalp hair

• axillary and pubic hair

• body hair on males

Hair structure

Shaft above the skin, root below, and dilated bulb at the end

Hair root bulb

grows around dermal papillae that provides hair nutrition

Hair matrix

mitotically active cells above the papilla that allows for hair growth

Hair layers

1. Medulla

2. Cortex

3. Cuticle

Medulla

core of loosely arranged cells and air spaces

Cortex

bulk of the hair; layers of elongated cells

Cuticle

outermost region consisting of multiple layers of thin, scaly cells that overlap like roof shingles

Epithelial root sheath

extension of the epidermis near the hair root that widens into a bulge; source of stem cells

Connective tissue root sheath

derived from dermis but a bit denser, surrounds epithelial root sheath

Arrector muslce

smooth muscle attaching the follicle and dermis to cause piloerection

High concentration of eumelanin causes what?

Brown and black hair

High concentration of pheomelanin causes what?

Red hair

Intermediate amounts of pheomelanin and little eumelanin causes what?

Blonde hair

Little to no melanin causes what?

Grey and white hair

Cross-sectional shape of hair textures

1. Straight hair is round

2. Wavy hair is oval

3. Curly hair is flat

Characteristics of nails

1. Clear, hard derivatives of stratum corneum

2. Composed of thin dead cells packed with keratin

3. Allow for external manipulations

4. Acts as a counterforce to fingertips

Nail plate

Hard part of the nail including the free edge, nail body, and nail root

Nail fold

skin around the nail separated by the nail groove

Nail bed

Skin under the nail

Nail matrix

growth zone at proximal end of nail; its thickness obscures underlying vessels and appears as white lunule

Cuticle

Zone of dead skin overhanging the proximal end of nail

What do sweat glands use for their mode of secretion?

exocytosis

Apocrine sweat glands

1. In the groin, anal region, axilla, areola, and beard in males

2. Ducts lead to hair follicles

3. Produce milky sweat with fatty acids

4. Inactive until puberty

5.Not for thermoregulation

Bromhidrosis

Foul smelling body odor/ perspiration

Eccrine/merocrine sweat glands

Numerous glands producing watery perspiration to cool the body; found on palms, soles, and forehead

Simple tubular glands

produce watery perspiration that helps cool the body; thermoregulation

Myoepithelial cells

In apocrine and eccrine glands that react to stimulation from the sympathetic nervous system

Composition of sweat

1. 99% water

2. pH of 4-6

3. Starts as protein-free filtrate of blood plasma produced by secretory portion of glands

4. Some drugs are excreted by sweat

Insensible perspiration

not noticeable; does not produce visible wetness of skin; 500 ml/day lost

Cutaneous transpiration

water loss from skin not due to sweating; water diffuses between keratinocytes and evaporates from skin surface

Diaphoresis

sweating with wetness of the skin; 1 L or more sweat lost during exercise