Integumentary System

Stratum basale

• Deepest layer of epidermis (closest to dermis)

• Gets nutrients from dermis

• Growing keratinocytes and melanocytes

Stratum spinosum

• Bundles of pre-keratin substances in cells

• Limited mitosis

Stratum granulosum

• Cells flatten and organelles deteriorate

• Contains fibers of kertain and shriveled nuclei

Stratum lucidum

• Thin, clear layer

• Only exists in lips, palms, soles

Stratum corneum

• 20-30 cell layers thick (uppermost layer)

• Keratinized, dead, and flattened cells connected by desmosomes

Melanin

• Gives hair and skin color

• Produced by malnocytes in stratum basal

• Protects from bacterial/viral and can activate lympathic system

Keratinocytes

• Produces keratin (fibrous protein)

• Keratin provides a waterproof, protective layer

• Kertainization occurs which hardens layers

Cutaneous glands

• Exocrine (release secrtion on skin surface)

• Consists of sebaceous and sweat glands

Sebaceous (oil) glands

• Releases sebum (oil + fragmented cells) on hair follicles

• Found everywhere except for palms of hands and feet

• Lubricates skin, keeps hair from becoming dry

Eccrine sweat glands

• Produce sweat (water, salts, metabolic waste)

• Found everywhere except for palms, soles, forehead

Apocrine sweat glands

• Found in armpits and genital areas

• Release sweat on hair follicles (sweat is milkly, yellowish)

Hair

• Fastest growing cells

• Consists of root, shaft, bulb, follicle

• Protects from particles and provides insulation

Hair bulb

• Deepest part of follicle

• Supplied blood by dermal region

• Part where new hair cells are made (hair matrix) and pushes them upward

Hair follicle

• Composed of epithelial root sheath and fibrous sheath

• Anchors hair into skin

• Extends from epidermis into dermis and hypodermis

Hair shaft

• Cells become keratinized + die to form shaft

• Consists of core called medulla and outer cortex layer surrounded by cuticle

• Cuticle keeps hair part

Arrector pili muscle

• Connects hair to hair follicle

• Pulls hair upright when cold or frightened (goose bumps)

• Sits in dermis layer

Nails

• Heavily keratinized and scalelike modification of epidermis

• Includes free edge, body (attached portion), nail folds, cuticle (proximal edge)

• Grows from nail matrix

Serous (serosa) membrane

• Double membrane, containing simple squamous epithelium + areolar (loose) CT

• Lines body cavities not open to exterior

• Secretes serous fluid (lubricant)

• Peritoneum (abdominal cavity), pleurae (around lungs), pericardia (around heart)

Parietal layer

• Lines walls of body cavities

• Outer layer of serous membrane

Visceral layer

• Covers outside surface of organs themselves

• Inner layer of serous membrane

Synovial membrane

• No epithelial tissue, only areolar CT

• Surrounds + cushions major body joints/organs

• Secretes synovial fluid (lubricate joints)

• Bursae (small sacs) lined with membranes

Dermis layer

• Under epidermis, above hypodermis

• Two major regions: papillary and reticular layer

• Made of connective tissue (collagen + elastic fiber)

• Helps supply nutrients, has pain/touch receptors

• Genetically predetermines fingerprints

Reticular layer

• Deepest layer of skin

• Comprised of dense irregular CT

• Blood vessels, sweat/oil glands, lamellar corpuscles (deep pressure receptors)

Papillary layer

• Upper layer of dermis

• Areolar CT

• Papillae, pain receptors, Meissner’s corpuscles (touch)

Athlete’s Foot

• Caused by Tinea pedis (fungal infection)

• Itchy, red peeling skin between toes

Boils (furnucles) and carbuncles

• Boils caused by inflammation of hair follicles

• Carbuncles are clusters of boils caused by bacteria infection

Cold sores (fever blisters)

• Caused by virus

• Blisters and itching

• Frequency/growth can be increased by exposure to sun/heat

Contact dermatitis

• Caused by exposure to chemicals that provoke allergic reactions

Impetigo

• Caused by bacterial infection

• Pink, fluid filled raised lesions around mouth/nose

Psoriasis

• Triggered by trauma, infection, hormonal changes, or stress

• Red, epidermal lesions covered with dry, silvery scales

• Itch, burn, crack, bleed

First-degree burn (superficial)

• Superficial burn

• Only epidermis is damage

• Skin is red and swollen (sunburn)

Second-degree burn (partial-thickness)

• Partial-thickness burn

• Epidermis + superficial part of dermis is damage

• Skin is red, painful, blisters (can regrow epidermis)

Third-degree burn (full-thickness)

• Destroys epidermis + dermis

• Burned area is painless (no pain receptors)

• Needs skin grafts (regeneration not possible)

Fourth-degree burn (full-thickness)

• Extends to deeper tissue (bone, muscle, tendon)

• Appears dry/leathery

• Amputation is possible and sometimes required

Nociceptors

• Free nerve endings for pain

• Found in skin, joint capsules, blood vessels, bone coverings

• Detects temperature, mechanical damage, chemicals

Thermoreceptors

• Free nerve endings in dermis, skeletal muscles

• Cold and hot receptors (detects changes in temperature)

Mechanoreceptors

• Sensitive to stretching, compression, twisting

• Consists of tactile receptors (sensitive to touch) and root hair plexus (hair displacement)

Merkel’s disc

• Fine touch and pressure

• High % in hairless areas

Meissner’s corpuscles

• Deep pressure

• Found in fingers, genitalia, joint capsules, messenterie

Ruffini corpuscles

• Pressure and distribution of skin

• Found in deepest layers of dermis