A&P 2.3-2.6

Epidermis

Most superficial layer of skin. Replaced every 4-6 weeks

Keratinocytes

The most abundant epidermal cells, they function mainly to produce keratin.

Melanocytes

Spidery black cells that produce the brown-to-black pigment called melanin.

Dermis

Dense, irregular connective tissue consisting of two regions - the papillary and the reticular areas.

Sebaceous Glands

Ducts that empty into hair follicles, excreting oily substances.

Sebum

The product of sebaceous glands. It is a mixture of oily substances and fragmented cells that acts as a lubricant to keep the skin soft and moist.

Eccrine Glands

These glands produce watery, thin sweat.

Apocrine Glands

Secrete milky protein that acts as a nutrient medium for the microorganisms found on the skin; causes odorous sweat

Keratin

Fibrous protein that is responsible for the strength and water resistance of the skin surface.

Collagen

A protein that is a main constituent of connective tissue.

Melanin

A natural pigment that protects the cells in the skin and in deeper layers from the hazardous effects of UV radiation by absorbing sunlight.

Hypodermis

Layer of the skin made up of connective tissue and fat that acts as insulation and padding for the skin.

stratum corneum

the most superficial layer of the epidermis consisting of dead cells

stratum basale

deepest epidermal layer made of a single row of cells that undergo rapid cell division

stratum spinosum

a layer of the epidermis that provides strength and flexibility to the skin just above the stratum basale

stratum granulosum

"Grainy layer"

Stops dividing and starts producing keratin and keratohyalin

stratum lucidum

a layer of the epidermis found only in the thick skin of the fingers, palms, and soles

dermal papillae

Found in the upper layers of the dermis, they create your fingerprint pattern

Hypodermis (subcutaneous layer)

Deep to the dermis; not technically part of the skin; made of adipose tissue; helps insulate

lunule

an opaque white crescent at proximal end of nail

nail

outgrowth of the skin, composed of keratin, at the end of each finger and toe

hair

outgrowth of the skin composed of keratin

hair follicle

a small tubular cavity containing the root of a hair

hair matrix

actively dividing area of the hair bulb that produces the hair

connective tissue

Animal tissue that functions mainly to bind and support other tissues, having a sparse population of cells scattered through an extracellular matrix.

ground substance

unstructured material that fills the space between the cells and contains the fibers

collagen fibers

provide flexibility and strength

elastic fibers

Flexible and "stretchy" fibers that allow tissues to stretch and return to their original shape

reticular fibers

Fibers made of collagen fibers that are very thin and branched to form a net-like pattern within tissues

ground substance

unstructured material that fills the space between the cells and contains the fibers

bone tissue

Most rigid connective tissue, Internally supports body structures, very active tissue, heals much more rapidly than cartilage

areolar connective tissue

Has a large amount of empty space within; collagen fibers going in all directions; soft packaging material that cushions and protects body organs

adipose tissue

Mostly cells and little ECM; stores lipids in vacuoles

reticular tissue

Composed of net-like protein fibers; forms internal supporting framework of soft organs such as the spleen

dense regular connective tissue

Consists of collagen fibers in a parallel arrangement; resists stretching; makes up tendons and ligaments

dense irregular connective tissue

Collagen fibers arranged in many directions; is able to withstand tension exerted in many directions; makes up fibrous capsules of organs and joints and dermis of the skin

elastic connective tissue

Connective tissue made from elastic fibers that allows stretching (found in the lungs, artery walls, vocal cords)

hyaline cartilage

Cartilage type with no visible fibers and a glassy appearance of the ground substance; found on the ends of long bones, ribs, and nose

Fibrocartilage

cartilage that contains fibrous bundles of collagen, such as that of the intervertebral discs in the spinal cord.

elastic cartilage

cartilage with abundant elastic fibers; more flexible than hyaline cartilage

blood

Connective tissue made of plasma, erythrocytes, leukocytes, and platelets.

Chondrocytes

cartilage cells

Lacunae

small cavities that contain osteocytes in bone or chondrocytes in cartilage

-cyte

suffix meaning "cell"

osteocyte

bone cell

fibrocyte

cells that produce and maintain fibrous connective tissue

osseous tissue

Latinized name for bone tissue

connective tissue proper

a grouping that contains both loose connective tissue and dense connective tissue

Histology

study of tissues

Tissues

Groups of cells with a common structure and function.

nervous tissue

A body tissue that carries electrical messages back and forth between the brain and every other part of the body.

muscle tissue

A body tissue that contracts or shortens, making body parts move.

epithelial tissue

A body tissue that covers the surfaces of the body, inside and out

epithelial tissue

Sheets of tightly packed cells that line organs and body cavities

simple squamous epithelium

single layer of flattened cells

stratified squamous epithelium

many layers of flattened cells

simple columnar epithelium

Made up of a single layer of tall cells that fit closely together

simple cuboidal epithelium

single layer of cube shaped cells

pseudostratified columnar epithelium

tissue that consists of a single layer of irregularly shaped and sized cells that give the appearance of multiple layers

transitional epithelium

multiple layers of many-shaped epithelial cells which can contract and expand in order to adapt to the degree of distension needed

stratified cuboidal epithelium

tissue that consists of two or more layers of cube-shaped cells, found in some ducts

stratified columnar epithelium

multiple layers or tall cells; small amounts in male urethra and in large ducts of some glands

basement membrane

Cells at the base of an epithelial layer are attached to this

keratinized stratified squamous epithelium

layers of flat cells, the outermost of which are dead but remain to form a protein-filled, protective layer

apical surface

an upper free surface exposed to the body exterior or the cavity of an internal organ

basal surface

The bottom layer of epithelial tissue that attaches to the basement membrane

squamous

flat cells

cuboidal cells

cube shaped cells

columnar cells

tall and column shaped cells