Human Anatomy: Integumentary System

integumentary layers

epidermis

dermis

hypodermis

epidermis

keratin

stratified squamous epithelial tissue

layers (stratum basale, spinosum, granulosum, corneum)

stratum basale

deepest- attached to dermis

includes stem cells that are constantly undergoing mitosis

stratum spinosum

visible extensions of keratinocytes (attachment points)

bundles of intermediate filaments made of pre-keratin

stratum granulosum

flattened keratinocytes that have keratohylin and lamellated granules

keratohylin granules- keratin production

lamellated granules- contain glycolipids (waterproofing)

stratum lucidum

only in thick skin

flat dead keratinocytes

stratum corneum

external layer

dead keratinocytes (contain keratin and intermediate filaments)

epidermis cell types

keratinocytes

melanocytes

tactile epithelial cells

dendritic cells

keratinocytes

originate in stratum basale

(soft) keratin production

produce detoxifying agents (antibiotics and enzymes)

melanocytes

in stratum basale

derived from neural crest cells

melanin production

melanin

pigmentation

transferred to keratinocytes (superficial side)

shields nuclei from UV

can be digested by lysosomes

tactile epithelial cells

in stratum basale

act as receptors (respond to touch, have sensory nerve ending)

dendritic cells

in stratum spinosum

star-shaped

immune function (receptor-mediated endocytosis, can migrate to lymph nodes)

dermis

second layer

two layers: papillary and reticular

innervated and vascularized

plexuses (collection/network of vessels): subpapillary (superficial) or dermal (hypodermis and lower dermis)

papillary layer

areolar connective tissue (elastic and collagen fibers)

dermal papillae: finger-like projections that increase surface area between dermis and epidermis

epidermal and dermal ridges (create fingerprints)

reticular layer

dense irregular connective tissue (network of collagen fibers), allows for stretch and recoil

features or dense irregular CT: cleavage lines, striae, flexure lines

cleavage line

areas of less dense collagen bundles

longitudinal in limbs and head

circular in neck and trunk

cut parallel for faster healing

striae

torn collagen (stretch marks)

flexure lines

wrinkles

fingers, palms, wrists, heels, toes

dermal plexus

temperature regulation by vasoconstriction (conserve heat) and vasodilation (release heat)

hypodermis (aka superficial fascia or subcutaneous layer)

composed of loose areolar and loose adipose connective tissue

insulation, energy storage, cushioning

thickness fluctuates with weight

appendages of integument

nail

hair

hair follicles

glands

nails

hard keratin

parts: free body, body, root

body

rests on nail bed (epidermis lacking strateum corneum)

root

nail matrix- actively growing, thickness comes from lunule

nail folds- form eponychium (cuticle)

hair

dead cells with hard keratin

three layers: medulla, cortex, cuticle

medulla

center

large cells, air spaces

cortex

middle layer

layer of flattened cells

cuticle

external layer

single layer of overlapping cells

separates hair from other hairs

hair color

melanin

made by melanocytes at follicle base

transferred to hair root

hair follicle

extends to dermis

parts: hair bulb, hair follicle wall, arector pili muscles

hair bulb

expanded area

root hair plexus (nerve endings): touch receptors

hair papilla (blood supply): capillaries

hair matrix:epithelial cells that form hair shaft

hair follicle wall

two root sheaths: outer connective tissue root sheath and inner epithelial root sheath

glassy membrane

outer connective tissue root sheath

derived from dermis

inner epithelial root sheath

derived from epidermis

internal root sheath formed by matrix cells

external root sheath formed by epidermal cells and includes stem cells

glassy membrane

outer connective tissue root sheath meets inner epithelial root sheath

arector pili muscle

skeletal muscle

contract to make hair stand up

glands

endocrine or exocrine

unicellular or multicellular

duct+secretory unit=gland

endocrine gland

hormones

mostly epithelial

ductless (released within)

exocrine gland

ducts (released to outside)

ex. sweat glands

unicellular gland

scattered through epithelial sheets

Goblet cells of GI tract (mucin+water=mucus)

multicellular gland

extend into connective tissue underneath

connective tissue fibrous capsule forms lobes

duct

simple (unbranched) vs. compound (branched)

secretory unit

tubular (coiled tube)

alveolar (grape cluster)

glands of integument

sebaceous or sodoriferous

sebaceous gland

alveolar with no lumen [central cavity]

Holocrine secretion: cells burst to release sebum

most trap dirt, condition hair, and slow water loss in hair follicles

sodoriferous (sweat) gland

composed of filtrate (water, salts, metabolic waste)

three types: eccrine, apocrine, modified sweat glands

eccrine sweat glands

function whole life

cover whole body

simple tubular shape

open at pore

apocrine sweat glands

start around puberty

axillary and groin area

open in hair follicle

sweat contains lipids and proteins

modified sweat glands

ceruminous glands: make ear wax

mammary glands