Integumentary system

surface ectoderm becomes

epidermis

mesoderm becomes

Dermis and hypodermis

stratum basale

Single layer of stem cells, melanocytes, and merkels; keratinocytes reproduce bere

stratum spinosum

Several cells thick of keratinocytes, melanocytes, and langerhans

Tonifibrils develop to support cells (give "spiny" appearance)

stratum granulosum

Keratin is produced, and forms dark staining keratohyalin granules. High lipid production makes cells water resistant (but kills them)

stratum lucidum

Only found in thick skin, does not stain well. Several layers of flat parallel keratin filaments

stratum corneum

Flat, dead, dry cells with no organelles, thickest layer

Thick skin

Palmer and planter, all five layers

Thin skin

No stratum lucidum

Epidermis

5 layers

Hypodermis

Consists of areolar and adipose CT

No distinct boundaries

Adipose is insulator

Houses major blood vessels and nerves

Dermis

Papillary layer (areolar CT)

Reticular layer (dense irregular CT)

vellus hair

Peach fuzz

Terminal hair

Thicker with darker pigment

Each hair consists of layers of keratinized epithelium

Cuticle

Cortex

Medulla

root hair plexus

Sensory neurons surrounding follicle that detects hair movement

arrector pili

a smooth muscle attached to hair follicles that causes "goose bumps" to appear on the skin when contracted

Sevaceous glands

Simple alveolar gland

Holocrine secretion

Without hair, the gland is a sebaceous follicle

eccrine sweat glands

Coiled, tubular simple gland

USE MEROCRINE SECRETION

no hair follicle

Sensible perspiration: water, NaCl, urea

apocrine sweat glands

Coiled tubular simple gland

MEROCRINE SECRETION

hair follicle

Axilla, groin, nipple region only

Active at puberty

mammary glands

modified apocrine sweat glands

Under nipple, secrete milk

ceruminous glands

Modified appocrine sweat glands

External ear, secrete cerulean

Mix with sebum and dead cells to create ear wax

Keeps out water and particles

Nails

Keratinized plate of epithelium growing from distal digits

Nail body

keratinized, plate-like structure

nail bed

Surface of skin covered by nail body

nail root

source of nail production

lunula

Whitish, half-noon region at base of nail plate due to obscured blood vessels