General Overview

Integumentary System

The body’s outer layer, comprising of skin, hair, nail, and associated glands

Cutaneous Membrane

Known as the skin that covers the body’s external surface

Cutaneous Membrane: Feature

Skin is the largest organ of the body that has an area of $2m^2$ and weighs 5kg

Cutaneous Membrane: Layers

• Epidermis: The superficial layer of skin that’s made up of avascular stratified squamous epithelium

• Dermis: The deep layer of skin that’s made up of vascular dense irregular connective tissues

• Hypodermis: The lowermost layer that’s made up of adipose and areolar tissues

  • Technically not a layer of skin

Integumentary: Functions

• Thermoregulation

• Blood Reservoir

• Protection

• Sensation

• Excretion and Absorption

• Synthesis of Vitamin D

Thermoregulation

A biological process by which an organism maintains its internal temperature through the fluctuations of blood vessels and secretions of sweat glands

Thermoregulation: Blood Vessels

• When body temperature increases, blood vessels will widen for greater blood flow to increase the amount of heat loss

• When body temperature decreases, blood vessels will constrict for lesser blood flow to decreases the amount of heat loss

Thermoregulation: Sweat Glands

• When body temperature increases, sweat production increases to create momentary evaporation to lower body temperature

• When body temperature decreases, sweat production decreases to conserve heat

Thermoregulation: Skeletal Muscle

The contraction of skeletal muscles can metabolically generate heat (shivering)

Blood Reservoir

The dermis houses a network of blood vessels that carry 8-10% of the total blood flow

Protection

• Keratin: Provides a physical barrier against microbes, abrasions, heat, and chemicals

• Lamellar Granules: Secretes lipid-rich secretion that makes the skin water-resistant to prevent dehydration

• Sebaceous Gland: Secretes oil that hydrates the skin and inhibits bacteria growth

• Melanocytes: Produces melanin that shields against the damaging effects of UV rays

• Dendritic Cells: Acts as the immune system

Sensation

The ability to perceive external stimuli of touch, pressure, pain, vibration, and temperature

Sensation: Free Nerve Endings

Numerous nonencapsulated sensory corpuscles that can detect temperature and pain

• Nociceptor: Senses pain

• Thermoreceptor: Senses temperature change

Sensation: Merkel Cell

Specialized mechanoreceptor in the basal layer of the epidermis that allows for light touch

Sensation: Meissner’s Corpuscles (Tactile Corpuscles)

Specialized mechanoreceptor in the papillary dermis that allows for light touch and low-frequency vibration

Sensation: Pacinian Corpuscles

Specialized mechanoreceptor in the reticular dermis that allows for deep pressure and high-frequency vibration

Secretion and Absorption

Secretion: The elimination of substances from the body

Absorption: The passage of materials from the external environment into body cells

Vitamin D Synthesis

Sunlight activates hormone calcitriol from enzymes in liver and kidneys that allows for Vitamin D to be made

Vitamin D Synthesis: Function

A fat-soluble vitamin that’s essential for calcium absorption, immune system, bone health

• Calcium Absorption: Absorbs calcium from foods in the gastrointestinal tract

• Immune System: Enhance innate defense mechanisms

• Bone Health: Strengthen bone matrix

Skin: Layer

• Thin (Hairy) Skin: Covers all body surfaces except hand and feet

• Thick (Hairless) Skin: Covers the hand and feet