Integumentary System- weight and area
→ Is the largest system of the body
→ 16% of body weight
→ 1.5 to 2 m2 in area
How many parts makeup the integumentary system?
→ The integument is made up of two parts
→ 1. Cutaneous membrane (skin)
→ 2. Accessory structures
Describe the Cut...
→ Cardiovascular system- By blood vessels in the dermis
→ Nervous system- By sensory receptors that detect stimuli for pain, touch, and
temperature
Is the hypodermis part of the Integumentary system?
→ No, Located below the dermis
→ -Composed of loose connective tissue: separates integument from the deep fascia
around organs
→ - Location of hypodermic injections
5 main functions of the Integumentary System?
→ 1. Protection of underlying tissues and organs
→ 2. Excretion of salts, water, and organic wastes (glands)
→ 3. Maintenance of body temperature (insulation and evaporation)
→ 4. Production of melanin, keratin, vitamin D3, and storage of lipids
→ 5. Detection of touch, pressure, pain, and temperature
→ PEMPD
Describe the Epidermis
→ Is avascular stratified squamous epithelium
→ Nutrients and oxygen diffuse from capillaries in the dermis
→ Dominated by keratinocytes (most abundant type of epithelial cells) -contain large
amounts of the protein keratin
Thin skin: location and layers
→ Covers most of the body
→ Has four layers of keratinocytes
→ Covers the palms of the hands and soles of the feet
→ Has five layers of keratinocytes
What are the 5 strata of keratinocytes in thick skin
→ 1. Stratum basale
→ 2. Stratum spinosum
→ 3.Stratum granulosum
→ 4. Stratum lucidum (missing in thin skin)
→ 5.Stratum corneum
→ Bottom to top
What is the Stratum Basale?
→ -Is attached to basement membrane by hemidesmosomes
→ -Forms a strong bond between epidermis and dermis
→ -Forms epidermal ridges (basis of fingerprints)
→ -Dermal papillae (tiny mounds)- projections from the dermis-Increase the area of
basement membrane and ttrengthen attachment between epidermis and dermis
→ -Has many basal cells, or germinative cells
What determines fingerprints?
→ Determined by genetics and
→ uterine environment during fetal development.
→ 1. Merkel cells- specialized epithelial tactile cells
→ Found in hairless skin
→ Respond to touch (trigger nervous system)
→ 2. Melanocytes
→ Contain the pigment melanin
→ Scattered throughout stratum basale
What is the Stratum Spinosum?
→ "the "spiny layer"
→ -Produced by division of stratum basale
→ -Eight to ten layers of keratinocytes bound by desmosomes
→ -Cells shrink until cytoskeletons stick out (looks spiny) - under normal histological
preperations
→ -Continue to divide, increasing thickness of epithelium
→ -Contain dendritic (Langerhans) cells, active in immune response - defend against
microorganisms that get past superficial layers of epidermis and defend against
superficial skin cancers
Describe the Stratum Granulosum layer
→ -the "grainy layer", Stops dividing, starts producing:
→ 1. Keratin
→ A tough, fibrous protein
→ Makes up hair and nails
→ 2. Keratohyalin
→ Dense granules
→ Cross-link keratin fibers
→ Note: as keratin accumulates, the cell flatten and its plasma membrane thickens and
becomes less permeable
Describe the Stratum Lucidum
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