Bio 226 Chapter 5

Front 1

Epidermis

Back 1

superficial region

Front 2

Dermis

Back 2

middle region

Front 3

Hypodermis (superficial fascia)

Back 3

deepest region

Front 4

Keratinocytes

Back 4

•produce fibrous protein keratin

Front 5

Melanocytes

Back 5

* 10–25% of cells in lower epidermis

* Produce pigment melanin

Front 6

Epidermal dendritic (Langerhans) cells

Back 6

macrophages that help activate immune system

Front 7

Tactile(Merkel) cells

Back 7

•touch receptors

Front 8

Stratum corneum

Back 8

Most superficial layer; 20–30 layers of dead cells represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space.

Front 9

Stratum granulosum

Back 9

Three to five layers of flattened cells,

organelles deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules.

Front 10

Stratum spinosum

Back 10

Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin.

Front 11

Stratum basale

Back 11

Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers.

See occasional melanocytes and epidermal dendritic cells.

Front 12

Layers of the Epidermis: Stratum Spinosum(Prickly Layer)

Back 12

•Cells contain a weblike system of intermediate prekeratin filaments attached to desmosomes

•Abundant melanin granules and dendritic cells

Front 13

Dermis

Back 13

•Strong, flexible connective tissue

•Cells include fibro-blasts, macrophages, and occasionally mast cells and white blood cells

•Two layers:

•Papillary

•Reticular

Front 14

Papillary layer

Back 14

•Areolar connective tissue with collagen and elastic fibers and blood vessels

Front 15

•Reticular layer

Back 15

•~80% of the thickness of dermis

•Collagen fibers provide strength and resiliency

•Elastic fibers provide stretch-recoil properties

Front 16

1.Melanin

Back 16

•Yellow to reddish-brown to black, responsible for dark skin colors

•Produced in melanocytes; migrates to keratinocytes where it forms “pigment shields” for nuclei

•Frecklesand pigmented moles

•Local accumulations of melanin

Front 17

2.Carotene

Back 17

•Yellow to orange, most obvious in the palms and soles

Front 18

3.Hemoglobin

Back 18

•Responsible for the pinkish hue of skin

Front 19

1.Eccrine(merocrine) sweat glands—abundant on palms, soles, and forehead

Back 19

•Sweat: 99% water, NaCl, vitamin C, antibodies, dermcidin, metabolic wastes

•Ducts connect to pores

•Function in thermoregulation

Front 20

2.Apocrine sweat glands—confined toaxillary and anogenitalareas

Back 20

•Sebum: sweat + fatty substances and proteins

•Ducts connect to hair follicles

•Functional from puberty onward (as sexual scent glands?)

Front 21

•Specializedapocrine glands

Back 21

•Ceruminousglands—in external ear canal; secrete cerumen

•Mammaryglands

Front 22

Sebaceous (Oil) Glands

Back 22

•Widelydistributed

•Mostdevelop from hair follicles

•Becomeactive at puberty

•Sebum

•Oilyholocrine secretion

•Bactericidal

•Softenshair and skin

Front 23

•Arrectorpili

Back 23

•Smoothmuscle attached to follicle

•Responsiblefor “goose bumps”

Front 24

Vellus

Back 24

pale, fine body hair of children and adult females

Front 25

Terminal

Back 25

•coarse, long hair of eyebrows, scalp, axillary, and pubic regions (and face and neck of males)

Front 26

1.Protection—three types of barriers

Back 26

•Chemical

•Low pH secretions (acid mantle) and defensins retard bacterial activity

Front 27

•Physical/ mechanical barriers

Back 27

•Keratin and glycolipids block most waterand water- soluble substances

•Limited penetration of skin bylipid-soluble substances, plant oleoresins (e.g., poison ivy), organicsolvents, salts of heavy metals, some drugs

Front 28

•Biological barriers

Back 28

•Dendritic cells, macrophages, and DNA

Front 29

2.Body temperature regulation

Back 29

•~500ml/day of routine insensible perspiration (at normal body temperature)

•Atelevated temperature, dilation of dermal vessels and increased sweat glandactivity (sensible perspirations) cool the body

Front 30

3.Cutaneous sensations

Back 30

•Temperature,touch, and pain

Front 31

4.Metabolic functions

Back 31

•Synthesisof vitamin D precursor and collagenase

•Chemicalconversion of carcinogens and some hormones

Front 32

Blood reservoir

Back 32

5.up to 5% of body’s blood volume

Front 33

Excretion

Back 33

6.nitrogenous wastes and salt in sweat

Front 34

•Basalcell carcinoma

Back 34

•Least malignant, most common

Front 35

•Squamouscell carcinoma

Back 35

Secondmost common

Front 36

•Melanoma

Back 36

•Most dangerous

Front 37

Ectoderm

Back 37

•epidermis

Front 38

Mesoderm

Back 38

•dermisand hypodermis

Front 39

Lanugo coat:

Back 39

•covering of delicate hairs in 5th and 6th month

Front 40

Vernixcaseosa

Back 40

•sebaceousgland secretion; protects skin of fetus