The Integumentary System Anatomy and Physiology

SOME FACTS ABOUT THE SKIN THAT YOU ARE IN… Its Waterproof, Stretchable,Washable, yet Tough! Its automatically repairs small cuts, rips & burns & is guaranteed to last a lifetime It weighs 7% of your body weight!

What Is The Structure of Skin? 3 Layers: Epidermis Composed of epithelial tissue (stratified squamous) avascular Dermis – underlies the epidermis Tough leathery layer composed of fibrous connective tissue Good supply of blood Hypodermis (a.k.a subcutaneous layer -not considered skin) Made of adipose and loose connective tissue Stores fat, anchors skin, protects against blows

Epidermis Dermis Basement membrane

What are the different types of cells in the epidermis? 1. Keratinocytes Make the protein keratin = tough & water resistant Are formed in lowest levels & push up by production of new cells below Become dead and scale-like, millions rub off everyday FYI: Everything you see on a person is dead! Outer 20-30 cells thick. Average person sheds 40 pounds of these in a lifetime!

What are the different types of cells in the epidermis? 2. Melanocytes Make pigment melanin (melan = black) it can transfer the pigment to keratinocytes Absorbs ultraviolet light so skin is not damaged melanocyte Melanin in keratinocytes

What are the different types of cells in the epidermis? 3. Langerhans’ cells Formed in bone marrow & Move to the skin Langerhans’ cell They are a type of Macrophage (White blood cell),which patrol & eat bacteria/viruses

What are the different types of cells in the epidermis? 4. Merkel Cells Connected to nerve cells from dermis Function as sensory receptors for touch.

What causes the color of skin? 3 pigments contribute to skin color 1. Melanin Range in color from yellow to reddish-brown to black Everyone has the same # of melanocytes but make varying amounts & colors Sunlight increases production! 2. Carotene-yellow to orange pigment found in foods. Most in the palms or soles. 3. Hemoglobin- Red blood (from dermal layer)gives a pinkish hue to fair skin

Characteristics of the Dermis Connective tissue has lots of collagen & elastic fibers - gives skin strength Thickest = Palms/soles Thinnest = Eyelids Extensibility = able to stretch (elbow skin) Elasticity = able to return to its original shape after extension/contraction (pregnancy & swelling)

More Characteristics… Sense Receptors: touch receptors (Meissner’s Corpuscles) & pressure receptors (Pacinian Corpuscles) Ridges formed from papillary layer form finger prints. http://bio.rutgers.edu/~gb102/lab_5/104bm.html

What are the major structures in Dermis? Sweat glands Sebaceous glands Hairs Nails

Sweat Glands 1. Merocrine (common sweat glands) 2. Apocrine (“funky”) Watery sweat Heat & waste loss (all over skin - lots on palms/soles) 2. Apocrine (“funky”) Milky/yellow thick sweat - thought to be scent glands Starts at puberty Armpits & groin 3. Ceruminous - make ear wax! 4. Mammary - make milk!

Sweat glands

Sebaceous Glands Blackheads - built up sebum Oil glands (sebum) - around hair follicles, none on palms/soles Softens and lubricates hair and skin Slows water loss and kills bacteria Blackheads - built up sebum Pimples - Built up sebum is a nutrient for bacteria (puss!)

Hair Made of dead keratinized skin cells 2 parts = shaft & root Function = Protection! FYI on Hair: You have about 100,000 hairs on your head You lose about 100/day It grows ~0.5 in/month - goes through cycles Hirsutism = excessive hair growth (often in women due to disease)

Hair Follicles

Hair Follicles

NAILS A scale-like modification of the epidermis Made of tightly compressed keratinized cells Useful tools to pick up small objects or scratch an itch. Nail matrix is the region responsible for nail growth. FYI: Nails & Hair DON’T grow after death - skin just shrinks!

Hypodermis (Subcutaneous) Loose connective Stabilizes skin position - loosely connected to dermis above & muscle below Lots of fat cells for padding & insulation

Functions of the Integumentary System 1. Protection: provides 3 types of barriers Chemical barriers: low pH of secretions slows bacterial growth (ring tarnish!) B. Biological: Macrophages C. Physical barriers: few things able to enter: Some Fat-soluble substances Poisons (poison ivy) Solvents- paint thinner Heavy metals- lead & mercury FYI: Transdermal patches are soaked in oils/solvents to carry drug Across - nicotine, birth control & motion sickness!

Functions 2. Temperature Regulation 3. Vitamin D Synthesis - sunlight converts cholesterol in dermis to Vit. D3 which is needed for calcium uptake 4. Sensation - touch, pressure, pain & temp 5. Storage - fats 6. Excretion (wastes) & Secretions (milk)

Aging Skin (A billion dollar industry!) Major Age-Related Changes Injury and infection increase Immune cells decrease Sun protection diminishes Skin becomes dry, scaly Hair thins, grays Sagging, wrinkles occur Heat loss decreases Repair slows = loses melanin & fills with air!

Skin Injury & Repair

Skin Injury & Repair

Skin Cancer Benign lesions such as warts and moles are not serious. Malignant tumors can start on the skin and invade other body areas. Crucial risk factor- overexposure to UV radiation

Types of Skin Cancer Basal cell carcinoma- most common, 30% of all white skin people get it. 99% curable if caught early Dome shaped nodules that form an ulcer in the center. Squamous Cell carcinoma- Grows rapidly and metastasizes if not removed Small red rounded elevation on the skin

Basal Cell Carcinoma

Squamous cell carcinoma

Lesion removed from patient Basal Cell Carcinoma

Skin Cancer Types cont. Melanoma Cancer of melanocytes (very dangerous) 5% of skin cancers but rising fast Can arise from preexisting moles Appears as a spreading brown or black patch Chance of survival is poor if the lesion is greater than 4 mm thick

Melanoma

What is the ABCD rule? Used for recognizing melanoma

What are the 3 types of burns? First-degree burns: only the epidermis is damaged. Redness, swelling and pain are common. (sunburn) 2-3 days to heal Second-degree burns: epidermis and upper layers of dermis. Blistering can occur. 3-4 weeks to heal. Third-degree burns: involves the entire thickness of the skin.

Burns

Second-degree burns Third-degree burn