Anat and Physio 2: Integumentary System

Skin layers

1. Epidermis

a) Keratinized stratified squamous epithelium

• Four cell types present in the epidermis

– Keratinocytes

– Melanocytes

– Dendritic (Langerhans) cells

– Tactile (Merkel) cells

b) Epidermis consists of four or five distinct layers

– Stratum basale: deepest

• single row of stem cells

• also called stratum germinativum (cell undergo rapid division)

– Stratum spinosum: prickly

• Cells contain web-like system of intermediate prekeratin filaments attached to desmosomes

• Abundant melanosomes and dendritic cells

– Stratum granulosum: granular

• Thin, 3 to 6 cell layers in which the cells flatten

• Keratinization begins (cells accumulate granules)

• Cells above this layer begin to die

– Stratum lucidum (only in thick skin)

– Stratum Corneum: rough

• 20–30 rows of dead, flat, keratinized membranous sacs

• Three-quarters of epidermal thickness

• Functions

  • Waterproofs

  • Protect from abrasion and penetration

  • Barrier against biological, chemical, and physical assaults

2. Dermis

a) Strong, flexible connective tissue, but the primary tissue found is dense irregular connective tissue (reticular)

b) Cells

• Fibroblasts, macrophages, and occasionally mast cells and white blood cells

c) Two layers:

• Papillary: Makes up about 10-20% of the dermis

  • Areolar connective tissue full of blood vessels and nerves

• Reticular: Makes up about 80-100 of the dermis

  • Dense irregular connective tissue

  • Lots of collagen fibers for strength

  • Lots of elastic fibers for stretch

3. Hypodermis

Subcutaneous tissue not part of skin

Q: A patient taking a drug that inhibits cell division (such as certain chemotherapy drugs) would expect which layer of the epidermis to be affected first?: stratum basale

Q: The principal tissue found in the dermal layer is: dense irregular connective tissue (dermis- reticular part)

Epidermis cont.

Q: Touch sensors of the epidermis: tactile cells

Q: The principal role of melanin is to: shield the nucleus from damage by ultraviolet radiation

Q: The most important role of the eccrine sweat gland is: body temperature regulation

Q: One critical function of sebum, in addition to roles in skin softening, is that it protects against: harmful bacteria

1. Skin pigments

a) Melanin: Gives you brown color

• Made by melanocytes

• Transported to keratinocytes and forms pigment shields

• Melanin sits on top of keratinocytes and protects DNA from damage by UV

b) Carotene: Carrots! Pigment is yellow/orange (palms or soles of feet)

c) Hemoglobin: Protein in red blood cells that carries O2

• Responsible for pinkish hue of skin

2. Appendages of the Skin

a) hair

• Dead keratinized cells of hard keratin

• More durable than soft keratin of skin

• Not in palms, soles, lips, nipples, portions of external genitalia

• Functions include:

• Warn of insects on skin

• Physical trauma

• Heat loss

• Sunlight

• Hair pigments

• Melanins (yellow, rust, brown, black)

• Gray/white hair: decreased melanin production, increased air bubbles in shaft

b) nails

• Scalelike modifications of epidermis

• Protective cover for distal, dorsal surface of fingers and toes

• Contain hard keratin

c) sweat glands

• Eccrine (merocrine): Found everywhere especially in the palms, soles of feet, and forehead

  • Function: to cool the body (thermoregulation)

  • Mainly composed of water and salts (electrolytes)

• Apocrine: Found in axillary (armpit) and anogenital (anus)

  • Tend to be stinky

  • Ducts connect to hair follicles

  • Specialized ones:

    • Ex: ceruminous glands= secrete cerumin (ear wax)

    • Ex: mammary glands= secrete milk

d) sebaceous oil glands

• Widely distributed

• Most develop from hair follicles and secrete into hair follicles

• Become active at puberty

• secrete sebum

  • Oily secretion that softens hair and skin; is also bactericidal

Skin Cancer

a) Most skin tumors are benign (not cancerous) and do not metastasize (spread)

b) Risk factors

• Overexposure to UV radiation

• Frequent irritation of skin

c) Some skin lotions contain enzymes that can repair damaged DNA

d) Three major types of skin cancer

• Basal cell carcinoma

• Squamous cell carcinoma

• Melanoma

e) abcd rule

• asymmetry

• border irregularity

• color

• diameter

Burns

a) Tissue damage caused by heat, electricity, radiation, certain chemicals

• Denatures proteins and kills cells

b) Partial-thickness burns

– First degree: Only affects the epidermis

• Localized area that has redness, swelling, and pain

– Second degree: Involves epidermis and upper dermis

• Ex: blister

c) Full-thickness burns

– Third degree: Full thickness of the skin

• Not painful at first bc you kill your pain receptors

• Burn areas appear gray, white, or blackish

Q: loss of one’s skin such as with severe burn leads to increased risk of

a. bacterial infection

b. inadequate body temperature maintenance

c. dehydration

d. all of the above