ANAPHY LESSON 2 (INTEGUMENTARY SYSTEM)

thermoregulation, protection, sensory reception, blood storage, excretion/absorption, vitamin D synthesis

Main functions of the integumentary system?

Skin (~4.5–5 kg; ~7% of body weight

Largest organ of the body by weight?

~2 m² (22 ft²)

Average surface area of skin?

0.5 mm (eyelids) to 4 mm (heels); average 1–2 mm

Skin thickness range?

Epidermis → Dermis → Subcutaneous layer

Layers of the skin from superficial to deep?

Provides a protective barrier

Function of the epidermis?

Provides strength, elasticity, blood supply, houses glands, hair, and sensory structures

Function of the dermis?

Anchors skin, stores fat, contains large blood vessels

Function of the subcutaneous layer?

Keratinocytes, melanocytes, Langerhans (intraepidermal macrophages), Merkel (tactile) cells

Main cell types in the epidermis?

keratinocytes

Produce keratin and lamellar granules; protect from abrasion, heat, microbes, chemicals

melanocytes

Produce melanin, determine skin color, absorb UV radiation, protect DNA

Langerhans cells

Immune defense; recognize and destroy microbes

Merkel cells

Detect touch; associated with sensory neurons

Stratum basale → stratum spinosum → stratum granulosum → stratum corneum

Layers of thin skin?

Stratum basale → stratum spinosum → stratum granulosum → stratum lucidum → stratum corneum.

Layers of thick skin?

stratum basale

Stem cells produce new keratinocytes

stratum spinosum

Provides strength and flexibility; contains Langerhans and melanocyte projections

stratum granulosum

Cells die, form keratin and lipid barrier; transition from living to dead cells

stratum lucidum

Adds extra toughness; only in thick skin

stratum corneum

Protects from injury/microbes, resists friction, continuously shed and replaced

Dense irregular connective tissue with collagen and elastic fibers

Dermis is composed of?

Papillary dermis features

1/5 thickness; thin collagen/elastic fibers, dermal papillae, capillary loops, Meissner corpuscles, free nerve endings

Reticular dermis features

4/5 thickness; dense irregular connective tissue, thick collagen, elastic fibers, houses glands, hair, vessels, nerves

dermis

Provides strength, elasticity, houses blood vessels, nerves, glands, and hair follicles

Melanin, hemoglobin, carotene

Skin color determinants?

melanin

Protects DNA, absorbs UV, determines skin color

hemoglobin

Contributes reddish/pink skin tones

carotene

Yellow-orange pigment from diet; vitamin A precursor

Function of hair

Protection, sensation, heat regulation

Medulla → Cortex → Cuticle

Hair structure layers?

sebaceous glands

Secrete sebum; lubricates hair/skin, prevents water loss, inhibits bacterial growth

eccrine sweat glands

Thermoregulation, minor waste excretion, emotional sweating

apocrine sweat glands

Emotional/sexual activity; odorless sweat metabolized by bacteria produces body odor

ceruminous glands

Produce earwax; waterproof, protect against foreign bodies/infection

Nail matrix

Nail growth originates from?

lunula

Covers nail matrix; appears whitish

hyponychium

Secures nail to fingertip

Sweating, vasodilation

Mechanisms of heat loss via skin?

Reduced sweat, vasoconstriction, shivering

Mechanisms of heat conservation via skin?

Skin functions in excretion and absorption

excretes water, salts, urea, ammonia; absorbs lipid-soluble substances (vitamins, drugs, gases)