The Integumentary System The Skin and its Appendages

The Integumentary System The Skin and its Appendages

The Skin Two main components ● Epidermis ● Dermis ● (Hypodermis)

Epidermis Cells of the Epidermis ● Keratinocytes ● Melanocytes ● Dendritic Cells (Langerhans cells)

Epidermis Layers of the Epidermis ● Thick Skin ○ ○ ○ Stratum Basale Stratum Spinosum Stratum Granulosum Stratum Lucidum Stratum Corneum ● Thin Skin ○ Absence of Stratum Lucidum

Epidermis Layers of Epidermis ● Stratum Basale (germinatum) ● Single row of stem cells ● 10 -25% melanocytes ● very small amount of tactile cells

Epidermis Layers of the Epidermis ● Stratum Spinosum ○ several cells thick ○ weblike intermediate filament network ○ melanin granules and dendritic cells present

Epidermis Layers of the Epidermis ● Stratum Granulosum ○ Keratinization Begins ○ Keratohyaline granules ○ Lamellar granules

Epidermis Layers of the Epidermis ● Stratum Lucidum ○ Only present in thick skin ○ 2 -3 rows of clear, flat, dead keratinocytes

Epidermis Layers of the Epidermis ● Stratum Corneum ○ anucleate ○ 20 -30 cells thick ○ ¾ of epidermis ○ high keratin content ○ thickened, glycoprotein covered plasma membranes ○ loses 50 k cells/min

Dermis Composition ● Connective Tissue proper ● Rich nerve and vascular supply ● contains hair follicles, glands, and sensory receptors Layers ● Papillary Layer ● Reticular Layer

Dermis Papillary Layer ● ● Thin areolar highly vascularized low density (great for phagocytes) ● Dermal papillae (form friction ridges in thin skin)

Dermis Reticular layer ● 80% of Dermis ● dense irregular connective tissue ● blood vessel network (cutaneous plexus) ● cleaveage and flexure lines

Appendages of the Skin

Appendages of the Skin Hair and Hair Follicles ● Structure of hair ● Structure of a hair follicle ● Types and growth of hair ● Hair thinning and baldness

Appendages of the skin Structure of a hair (fig 5. 5) ● Produced by hair follicles ● Conists primarily of dead keratinized cells ● cells contain hard keratin Regions ● Shaft ● Root Concentric Layers ● Medulla ● Cortex ● Cuticle

Appendages of the skin Structure of a Hair Follicle (fig 5. 5) ● Epithelium based ● Hair bulb ● Hair follicle receptor ● Hair papillae ● Peripheral connective tissue sheath ● Epithelial root sheath

Appendages of the Skin Types and Growth of Hair ● Vellus Hair ● Terminal Hair

Appendages of the Skin Hair Thinning and Baldness ● Alopecia ● True Baldness (Male Pattern)

Appendages of the Skin Nails (fig 5. 6) ● Scale-like modification of epidermis ● hard keratin ● free edge, nail plate, root ● nail bed ● nail matrix ● nail folds and cuticle

Appendages of the Skin Sweat (Sudoriferous) Glands ● Eccrine (Merocrine) Sweat Glands ● Apocrine Sweat Glands

Appendages of the Skin Sebaceous (Oil) Glands ● Simple branched alvolar glands ● secrete sebum ● holocrine type glands ● secrete into hair follicles and occasionally pores

Skin Functions Protection ● Chemical Barriers ○ acid mantle ● Physical Barriers ● Biological Barriers ○ dendritic cells, macrophages, DNA

Skin Functions Body Temperature Regulation Heat Loss ● Vaodilation ● heat loss through sweat evaporation Heat conservation ● Vasoconstriction

Skin Functions Cutaneous Sensation

Skin Functions Metabolic Functions ● Produces vitamin D precursor ● disarm cancer causing chemicals ● activate some steroid hormones

Skin Functions Blood Resevoir ● 5% of total blood volume

Skin Functions Excretion ● ammonia, uric acid, urea, salt, water.

Homeostatic Imbalances of Skin Cancer ● Basal Cell Carcinoma ● Squamous Cell Carcinoma ● Melanoma ○ ○ ○ Asymmetry Border Irregularity Color Diameter Elevation

Study Guide Will Post Wednesday