Bio Exam 2 Part 1

Functions of the integumentary systems

Protection - against UV light, microorganisms, water lost Sensation - Sensory Receptors Temperature Regulation Vitamin D Excretion

Integument or Skin

Most accessible organ system Has two major components Cutaneous Accessory Structures

Cutaneous Membrane Layers

Epidermis - Stratified squamous epithelium Dermis - Papillary layer, Reticular layer Hypodermis - Not part of integument, separates integument from deep fascia, loose connective tissue and adipose that connects skin to structures below it

Accessory Structures

Hair shaft and follicle Sweat gland Tactile and lamellated corpuscles Sebaceous gland Arrector pili muscle Nerve fibers Cutaneous plexus (Network of blood vessels)

Epidermis

Avascular - nourished by diffusion from capillaries of the papillary layer of the dermis Dominated by keratinocytes Form several layers or strata

Deep layers form Epidermal Ridges

Blind to dermal papilla of dermis Most of body covered with four strata (thin skin) Palms of hands and soles of feet have five strata (thick skin) Separated from dermis by basement membrane

Dermal papilla

Increase the surface area between epidermis and dermis for attachment Diffusion of nutrients to the avascular epidermis Creates fingerprints and footprint in thick skin

Thick and Thin Skin

Thick skin Has all 5 epithelial strata Found in areas with pressure or friction Fingerprints and footprints Thin skin Composed of 4 strata (No stratum lucidum) More flexible then thick Covers rest of body Most has hair except lips and external genitalia Callus - increase in numbers of layers in the stratum corneum. When this happens over a bony prominence, a corn forms.

Epidermal Cell Type Part 1

Keratinocytes - most cells, produce keratin for strength. Keratin - protein that makes cells water proof Melanocytes - contribute skin color Melanin - protein that give skin color Langerhans cells - part of the immune system Phagocytic cell - patrols epidermis for pathogen entry

Epidermal Cell Type Part 2

Merkel cells - part of the nervous system Sensory receptors - sensitive to light touch, and pressure Keratinization - Cell moves outward they fill with keratin, die, and serve as a layer that resists abrasion and forms permeability layer.

Strata layers of the Epidermis Part 1

Stratum Corneum (cornum, horn) Outermost protective layer 15-30 layers of keratinized cells (filled with keratin) All dead cells attach with desmosomes Stratum Lucidum (clear layer) Separates stratum corneum from underlying layers Flattened dead cells filled with keratin and keratohyalin Not in thin skin

Strata layers of the Epidermis Part 2

Stratum Granulosum (grainy layer) 3-5 layers of keratinocytes Cells that start making keratin and keratohyalin Membrane become less preamble Stratum Spinosum (spiny layer) 8-10 layers of live keratinocytes bound by desmosomes Dendritic cells found here (Defend against pathogens and cancers)

Strata layers of the Epidermis Part 3

Stratum Basale Basal cells attached to basal lamina with hemidesmosomes Merkel cells found here (touch receptors)

Skin Color

Influenced by Presence of pigments (melanin and carotene) Degree of dermal circulation Keratinization of epidermis UV radiation Genetically

Melanocytes

Make melanin from amino acid tyrosine. Colored brown to black, may be yellow or reddish. Genetically determined Package melanin in vesicles (melanosomes) Usually about 1000 melanocytes

Temporary Factors that Affect Skin Color

Carotene Orange-Yellow pigment Accumulates in epidermis and fatty tissues of hypodermis Found in variety of orange vegetables Blood Supply Red coloration from red blood cells with red hemoglobin pigment Dilation of dermal blood vessels also affects observed skin coloration UV Radiation Stimulate melanocytes to produce more melanin

Skin Cancers

Basal Cell Carcinoma Most common skin cancer Due to UV radiation Most people survive Squamous Cell Carcinoma Second most common UV exposed areas Can be deadly if not treated Malignant Melanoma Cancerous melanocytes Lymphatic system Not detected 5 year survival is 14%

Conditions affecting skin color

Albinism Genetic mutation causes lack of melanin production or melanin that is light color Vitiligo Loss of melanocytes usually due to an autoimmune response