Integumentary System

Sites used http://www. meddean. luc http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Integumentary/Integum.htm

Skin ~9 lbs. (4.1 kgs) Covers S.A. of 15-20 ft2 (1.4 to 1.9 m2) Every square inch contains 15’ blood vessels, 12’ nerves, 650 sweat glands, 100 oil glands, 1500 sensory receptors, & 3 million cells Thickness varies from 1/32” to 1/8” Skin cells die & replaced continuously 3 layers = epidermis, dermis & hypodermis

Skin-Major Functions Protects Excretion/Secretion Helps regulate body temperature Sensation (Cutaneous sensation) Promotes vitamin D synthesis Acts as reservoir for blood

Protects 3 ways Chemically Physically Biologically

Protects-Chemically Acidic skin secretions inhibit bacteria from multiplying Substances in sebum (oil) kill some bacteria Melanin-shield skin from UV rays

Protects-Physically Keratinized cells-ex.epidermis, hair and nails Barrier to invading organisms

Protects-Biologically Dermal macrophages-2ndline of defense against bacteria Epidermis contains macrophage like Langerhan’s cells = immunity

Excrete/Secrete Sweat-nitrogenous waste, sodium chloride Sebum-secreted by sebaceous glands

Regulate Body Temp. Evaporation of sweat Dermal blood vessels dilate and constrict

Cutaneous Sensation Sensory receptors-Meissner’s, Pacinian, Ruffini’s, Krauses, free nerve endings

Vitamin D Synthesis. Exposed to UV-skin converts cholesteral molecules to Vitamin D

Reservoir for blood Shunted from skin to general circulation ex. To working muscles

Skin 3 layers Epidermis Dermis Hypodermis

1. Epidermis Most superficial layer of skin First barrier of protection Principle (main) cell type in epidermis = keratinocytes 4-5 layers 4 types of epidermal cells

2. Dermis Contains sebaceous and sweat glands Sensors: 2-A) Pacinian corpuscle – heavy touch & vibratiions 2-B) Meissner’s corpuscle – light touch

3. Hypodermis Most of the blood flow (arteries & veins) Contains fat for insulation & cushioning

4. Hairs Protection Decrease heat loss Errector pilius – pulls hair errect during stress

Common Disorders: Eczema Psoriasis Freckles/Moles Athelete’s Foot/Jock Itch Melanoma Calluses/Corns Bruising Impetigo

Epidermal Cells Keratinocytes: compose most of epidermis; make protein keratin Keratin: waterproofs and protects skin Melanocytes:synthesize melanin Melanin protects against UV damage Merkel cells: associated with sensory receptors (touch) Langerhan’s cells: macrophages used in defense against microorganisms

Skin thick, All layers

Stratified Squamous Epithelium

Epidermis Layers

Stratum Germinativum

Stratum Spinosum

Close Up of Stratum Spinosum

Stratum Spinosum

Stratum Granulosum

Stratum Lucidum

Stratum Corneum

Skin thick, All Epidermis Layers

Skin Thin All epidermis layers

Dermis

Skin thin Dermis all layers

Skin Thick Dermis All Layers

Papillary Dermis

Reticular Dermis

Skin Appendages

Hairy Skin with intact and disintegrating sebum containing secretory cells

Hairy Skin with Sebaceous Gland

Skin with hair follicles

Hair Follicle

Hair Follicle with labels

Thick Skin with excretory duct and secretory tubulus

Thick skin with merocrine sweat gland