Integumentary System Flashcards
The skin has two distinct layers.
The superficial layer is a sheet of keratinized stratihed squamous epithelium called the
epidermis
The epidermis is itself divided into distinct histological regions or strata (meaning “layers”):
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum
is the deepest stratum of the epidermis. It consists of a single sheet of columnar cells that continue to divide. As the daughter cells are formed, they are pushed upward, becoming part of the next stratum.
Stratum Basale
is noted for its multilayer of distorted (“spined”) cells. The cells become distorted as they are pushed up from the deeper stratum basale.
Stratum spinosum
Stratum Basale & stratum spinosum together are often called
stratum germinativum.
is superficial to stratum spinosum.
It contains flattened cells pushed up from the deeper strata.
As the cells are pushed up through this stratum, they form the protein granules that give it the name ___. By the time the cells leave this stratum, they have died.
Stratum granulosum
(meaning “light layer”) is a very thin layer present only in thick skin.
Thick skin is found only in high-wear areas such as the palms and soles.
The more flexible thin skin is found over most other areas of the body.
This stratum’s name comes about because it is translucent, allowing light to pass through it easily.
Stratum lucidum
is the layer of dead, keratinized tissue already
is extremely thick in thick skin, providing a great deal of protection.
It protects deeper tissues from mechanical injury, from inward or outward diffusion of water and other molecules, and from invasion by microorganisms.
Stratum corneum
The layer of skin deep to the epidermis is a sheet of irregular fibrous connective tissue called the
dermis
has a scattering of blood vessels and nerves. The blood vessels supply both the dermis and epidermis.
Because blood cools when it travels through the skin, the body varies the amount of blood sent to the skin to regulate loss of heat by the entire body.
Dermis
There are two regions of the dermis:
Reticular layer
Papillary layer
The ___ of the dermis is a thick region of irregularly arranged protein fibers. Most of the fibers are collagenous, but a few are made of elastin.
reticular layer
The ____ is the bumpy superficial portion of the dermis attached to the epidermis.
The bumps, called ___ (meaning “nipples”), form regular rows in thick skin but are rather irregularly arranged in thin skin. For this reason, thick skin can be observed to have distinct ridges, such as fingerprints. These ridges give the hands and feet better gripping ability.
papillary layer
papillac
Deep to the skin is a layer of subcutaneous tissue, sometimes called the ____ or ___. Although not a part of the skin, it is often studied along with skin.
hypodermis, superficial fascia
is loose, fibrous (areolar) connective tissue that connects the skin to underlying muscles and bone. Some of the areolar tissue has been modified to become adipose tissue. Adipose tissue’s protective and insulating characteristics complement the protection and temperature regulation roles of the skin.
Subcutaneous tissue
The skin has a variety of accessory structures, including ?
Hair & nails
Both hair and nails are modified forms of _____ or keratinized tissue.
stratum corneum
is a cylinder of compact keratinized material
hair
is a plate of compact keratinized material
nail
Each hair is formed within a separate.
The ____ is a sheath-like indentation of the epidermis
hair follicle
At the bottom of the follicle, a ___ covered with stratum germinativum produces the hair.
Hair papilla
The portion of each hair within the follicle is called the
hair root
the portion that has been pushed out of the follicle is called the
hair shaft.
The hair has a very dense ___ and a less dense __.
cortex, medulla
Attached to each follicle is an
This gland produces the fatty substance, sebum, that coats the hair and skin.
exocrine (ducted) sebaceous gland
prevents moisture loss and conditions the hair and skin so that they do not become brittle and easily broken.
Sebum
The ___ is a strap of smooth muscle tissue connecting the side of a follicle to the superficial surface of the dermis.
When contracted, the muscle pulls the follicle so that it is nearly perpendicular to the skin’s surface. This increases the air spaces among the hairs, improving their insulation quality.
Contraction of this also dimples the epidermis, raising a ridge at the edge of the follicle (a “goose pimple” or “goose bump”).
arrector pili muscle
The toenail or fingernail is also formed by a modified portion
stratum germinativum
In the case of either hair or nail, this modified tissue is often called
matrix
A portion of the nail bed (skin under the nail) is matrix that produces the
nail plate
Part of the matrix may be visible through the nail as a pale crescent, or ___.
lunula
Nail formation begins under a fold of
The portion of the nail under the fold is the root, and the visible portion is the nail body.
epidermis
A ___ may extend from the fold onto the nail body
cuticle, or eponychium
They are exocrine glands that produce a watery solution, sweat, that coats the skin.
Sweat glands
serves primarily to improve heat loss by the skin through evaporation.
Sweat
____ produce thin, watery sweat in many areas of the body.
Eccrine sweat glands
found in the axillary and pubic regions, and starting at puberty, secrete a thicker sweat that is rich in complex organic molecules.
Apocrine sweat glands
