Integumentary System

(Hypodermis)

Integumentary System Skin Hair Nails Associated Structures (vessels, nerves, glands)

Functions of Skin Protection Sensation Excretion Vitamin D (steroid) production – needed to absorb calcium Immunity Healing Wounds Body temperature homeostasis vasoconstriction & vasodilation

Integumentary System Skin (cutaneous membrane) Main layers – superficial to deep Epidermis Dermis Hypodermis (not always considered part of skin) (Hypodermis)

Epidermal Dendritic Cell Stratum Corneum Stratum Granulosum Page 26 Epidermis Diagram Desmosomes Keratinocytes Epidermal Dendritic Cell Stratum Corneum Stratum Granulosum Stratum Spinosum Stratum Basale Dermis Sensory Nerve Melanin Melanocyte

Dermal Papillae Pore Eccrine Sweat Gland Arrector Pili Muscle Page 28 Skin Diagram Hair Shaft Epidermis Papillary Layer Dermis Reticular Layer Hypodermis Sensory Nerve Lamellar Corpuscle Hair follicle receptor Dermal Papillae Pore Eccrine Sweat Gland Arrector Pili Muscle Sebaceous Gland Hair follicle Hair root

Pg 26 Epidermis Diagram D. E. F. G. H.

Skin Structure

Pg 27 “Epidermis Functions” On top skin Epidermis – outer layer Tissue: Keratinized stratified squamous epithelium Avascular (no blood vessels in this layer) Renews itself ~ every 45 days (goes through mitosis) layered thin & flat

Epidermis – cell types within B.) Keratinocytes (~90% of the epidermis) produce keratin – waterproof tough flexible protein accelerated in areas of friction Callus – thickened skin Produce hair and nails

Epidermis – cell types within K.) Melanocytes Produce melanin- brown, yellow brown, or black pigment Prevents DNA mutation from the UV radiation

A.) Desmosomes Form a tight junction to help layers stay together

5 Layers of the Epidermis (superficial to deep) Pneumonic: Come Lets Get Sun Burned Stratum Corneum Stratum Lucidum Stratum Granulosum Stratum Spinosum Stratum Basale

D.)Stratum Corneum (top layer) Outermost (15-30 layers of cells) Also completely keratinized Tough, waterproofing protection Dead cells (attached by desmosomes) Flat cells

D.)Stratum Corneum FUN FACTS Dead cells stay on top for about 2 weeks before they are shed off This layer is very dry so most bacteria cannot survive

Stratum lucidum (2nd Layer) ONLY found in thicker epidermis – palms, soles, callus Completely keratinized (and dead!) Flattened and closely packed

D.)Stratum Granulosum (3-5 layers of cells) Produce a large amount of Keratin The cell becomes thinner because their cell membranes are thick because of the tough keratin and substances cannot diffuse in

F.)Stratum Spinosum (8-10 layers of cells) Several layers of many sided cells (looks spiny) Contains Langerhan’s macrophages Slightly Mitotic Cytoplasm shrank b/c of chemicals by the cytoskeleton remained

G.)Stratum Basale/Germinativum (deepest layer) Highly Mitotic (produce new skin layers) (WHY?) Melanocytes Merkel cells: detect light touch Epidermal Ridges: attach the epidermis to the dermis Form our fingerprints