Skin Anatomy PDF

Anatomy & Physiology: The Skin Anatomy Dr. Heather Jones [email protected] 866-8133  Overview The skin is the largest organ (12-15% of body weight) and has 2 layers i. Epidermis is a keratinized stratified squamous epithelium ii. Dermis is a conn...

Anatomy & Physiology: The Skin Anatomy Dr. Heather Jones [email protected] 866-8133  Overview The skin is the largest organ (12-15% of body weight) and has 2 layers i. Epidermis is a keratinized stratified squamous epithelium ii. Dermis is a connective tissue layer Hypodermis is another connective tissue layer but is not part of the skin – it is mostly subcutaneous fat. Functions i. Boundary between external and internal environment ii. Vitamin D synthesis iii. Other functions: temperature regulation, sensory perception, excretion of wastes and salts, protection from trauma and bacteria Anatomy  Anatomy Epidermis ✓ Main cells are keratinocytes  Anatomy Cells and Layers of the Epidermis ✓ Thin skin (4 layers) versus thick skin (5 layers)  Anatomy Cells and Layers of the Epidermis ✓ Stratum Basale: hemidesmosomes, ridges & dermal papilla ▪ Basal cells: germ cell which replace superior keratinocytes ▪ Merkel cells: sensory cells ▪ Melanocytes: pigment cells  Anatomy Cells and Layers of the Epidermis ✓ Stratum Spinosum: dividing keratinocytes from bs move into this layer ▪ Dendritic cells: Immune cells against microorganisms and cancers ✓ Stratum Granulosum: grainy layer of non-dividing keratinocytes ▪ Keratin ▪ Keratohyalin  Anatomy Cells and Layers of the Epidermis ✓ Stratum Lucidum: only in think skin, flatten non-dividing keratinocytes ✓ Stratum Corneum: 15-30 layers of keratinocyte fibers ▪ Keratinization: the formation of protective layer of cells filled with keratin ▪ Strong connections ▪ Dry surface ▪ Help with water loss  Anatomy Cells of the dermis ✓ Collagen fibers ✓ Elastin fibers ✓ Fibroblasts  Anatomy Cells and Layers of the dermis ✓ Papillary layer: areolar tissue near epidermis, loose tissue allows for immune cell migration, lots of blood vessels ✓ Reticular layer: dense layer of collagen and elastic fibers  Anatomy Hypodermis (subcutaneous tissue): not considered “skin” ✓ Composed of areolar and adipose tissue ✓ Stabilizes skin in location to underlying organ ✓ Thermal insulation and energy supply ✓ Abundant blood supply good for subcutaneous injection (“hypodermic” needle)  Blood Flow Capillaries of the skin Cutaneous plexus Papillary plexus Contusions caused by trauma to the skin ruptures dermal blood vessels Functions: Temperature regulation, low leads to cyanosis  Neural Innervation Sensory receptors found in the skin Detect: touch, vibration, temperature, moisture, ect  Skin Color Skin Pigments: Carotene: Orange-yellow pigment which accumulates in the stratum corneum of the epidermis and subcutaneous layer ✓ Corns and callouses thicker layer more prominent Melanin: brown/black darker pigment produced by melanocytes in stratum basale ✓ Melanin packaged into melanosomes which are taken up by keratinocytes ✓ Darker skin: melanosome transfer in upper layers ✓ UV exposure: melanosomes are concentrated around nucleus to protect DNA from UV light, UV increases melanocyte activity  Cutaneous Glands Sweat glands (sudoriferous): ✓ Apocrine: armpits, nipples, pubic region ▪ Extend deep into dermis ▪ Tubular glands producing odorous, milky, sticky sweat ✓ Merocrine: widely distributed, more prevalent, found on palms and soles of the feet ▪ Not as deep in the dermis ▪ Secretion is mainly water/salts: vaporization Myoepithelial cells activated by nervous system increase secretions  Cutaneous Glands Sebaceous Glands: secrete oily lipid secretion into a hair follicle Sebum: triglycerides, proteins, electrolytes and cholesterol ✓ Functions to inhibit bacteria growth, lubricate and condition Clogged sebaceous glands leads to inflammation and acne  Hair Accessory organs of the skin made of hard keratin: non-living Slender filament of keratin produced in a hair follicle Functions: ✓ Protection and cushion (mainly scalp) ✓ Prevent foreign body entry (nostrils and ears) ✓ Sensory Anatomical Features ✓ Shaft ▪ Medulla: soft keratin ▪ Cortex: keratinized cells ▪ Cuticle: thin layer ✓ Bulb: bundle of epithelial cells ✓ Root hair plexus: sensory nerves ✓ Arrector pili muscle: papillary layer dermis, goose bumps