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Flashcards in The Integumentary System CH 7 Deck (42):
1

Skin, Integument

is considered an organ system because of its extent and complexity.

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Skin has two distinct regions

The superficial epidermis composed of epithelium and an underlying connective tissue, the dermis.

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deep to the dermis

is the hypodermis or superficial fascia which is not considered part of the skin. it consists primarily of adipose tissue.

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Stratum Corneum

(Horny layer) Most superficial layer, 20-30 layers of dead cells, essentially flat membranous sacs filled with keratin. constantly rubbing off and being replaced by division of the deeper cells. Glycolipids in extracellular space.

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Stratum Granulosum

One to five layers of flattened cells, organelles deterioration, cytoplasm full of lamellar granules (release lipids) and keratohyaline granules.

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Stratum spinosum

Several layers of keratinocytes joined by desmosomes. Cells contain thick web like bundles of intermediate filaments made of pre-keratin protein. The stratum spinosum cells appear spiky (hence their name) because as the skin tissue is prepared for histological examination, they shrink but their desmosomes hold tight. Immediately superficial to the basal layer.

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Stratum basale

Deepest epidermal layer, one row of actively mitotic stem cells, some newly formed cells become part of the more superficial layers. Immediately adjacent to the dermis.

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Stratum lucidum

(Clear layer) A very thin translucent band of flattened dead keratinocytes with indistinct boundaries. it is not present in regions of thin skin.... present in thick skin

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Keratinocytes

(literally, keratin cells) The most abundant epidermal cells, their main function is to produce keratin fibrils.

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Keratin

is a fibrous protein that gives the epidermis its durability and protective capabilities. Keratinocytes are tightly connected to each other by desmosomes.

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Melanocytes

Spidery black cells that produce the brown-to-black pigment called melanin. the melanin provides a protective pigment umbrella over the nuclei of the cells in the deeper epidermal layers this shielding their genetic material (DNA) from the damaging effects of ultraviolet radiation. A concentration of melanin in one spot is called a freckle.

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Dendritic cells

Also called Langerhans cells, these cells paly a role in immunity.

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Tactile (Merkel) cells

Occasional spiky hemispheres that, in combination with sensory nerve endings, form sensitive touch receptors called tactile or Merkel discs located at the epidermal-dermal junction.

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Dermis

The dense irregular connective tissue making up the dermis consists of two principal regions -- the papillary and reticular areas.

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Papillary layer

The more superficial dermal region composed of areolar connective tissue. It is very uneven and has fingerlike projections from its superior surface, the dermal papillae, which attach it to the epidermis above. these projections lie on top of the larger dermal ridges. In the palms of the hands and soles of the feet, they produce the fingerprints, unique patterns of epidermal ridges.

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Reticular layer

The deepest skin layer. It is composed of dense irregular connective tissue and contains many arteries and veins, sweat and sebaceous glands, and pressure receptors (lamellar corpuscles).

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Accessory Organs of the Skin

Cutaneous glands, hair and nails are all derivatives of the epidermis, but they reside in the dermis. They originate from the stratum basale and grow downward into the deeper skin regions.

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Nails

hornlike derivatives of the epidermis

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Nails: Body

The visible attached portion.

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Nails: Free Edge

The portion of the nail that grows out away from the body. The tip.

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Nail: Hyponychium

the region beneath the free edge of the nail. where the skin connects to bottom of nail.

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Nail: Root

The part that is embedded in the skin and adheres to an epithelial nail bed.

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Nail: Nail folds

Skin folds that overlap the borders of the nail. along both sides of the nail

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Nail: Eponychium

The thick proximal nail fold commonly called the cuticle.

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Nail: Nail Bed

Extension of the stratum basale beneath the nail

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Nail: Nail Matrix

The thickened proximal part of the nail bed containing germinal cells responsible for nail growth. As the matrix produces the nail cells, they become heavily keratinized and die. Thus nails, like hairs, are mostly nonliving material.

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Nail: Lunule

the proximal region of the thickened nail matrix, which appears as a white crescent. Everywhere else, nails are transparent and nearly colorless, but the appear pink because of the blood supply in the underlying dermis.

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Hair

Structure consisting of a medulla, a central region surrounded first by the cortex and then by a protective cuticle.

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Hair Root

The portion of the hair enclosed within the follicle is called the root.

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Hair Shaft

The portion projecting from the scalp surface

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Hair Bulb

is a collection of well-nourished germinal epithelial cells at the basal end of the follicle.

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Hair Follicle

A structure formed from both epidermal and dermal cells. Its inner epithelial root sheath, with two parts (internal and external), is enclosed by a thickened basement membrane, the glassy membrane, and a peripheral connective tissue (or fibrous) sheath, which is essentially dermal tissue.

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Hair Papilla

A small nipple of dermal tissue protrudes into the hair bulb from the peripheral connective tissue sheath and provides nutrition to the growing hair.

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Arrector pili muscle

Small bands of smooth muscle cells connect each hair follicle to the papillary layer of the dermis. When the muscles contract (during cold or fright), the slanted hair follicle is pulled upright, dimpling the skin surface with goose bumps. The activity of the arrector pili muscles also puts pressure on the sebaceous glands surrounding the follicle, causing a small amount of sebum to be released.

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Cutaneous Glands

The cutaneous glands fall primarily into two categories the sebaceous glands and the sweat glands.

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Sebaceous (Oil) Glands

The sebaceous glands are found nearly all over the skin, except for the palms of the hands and the soles of the feet. Their ducts usually empty into a hair follicle, but some open directly on the skin surface.

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Sebum

Is 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 and keeps the hair from becoming brittle. the sebaceous glands become particularly active during puberty when more male hormones (androgens) begin to be produced; this the skin tends to become oiler during this period of life.

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Blackheads

are accumulations of dried sebum, bacteria, and melanin from epithelial cells in the oil duct.

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Acne

is an active infection of the sebaceous glands

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Sweat (Sudoriferous) Glands

These exocrine glands are widely distributed all over the skin. Outlets for the glands are epithelial openings called pores. Sweat glands are categorized by the composition of their secretions.

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Eccrine Glands also called Merocrine Sweat Glands

These glands are distributed all over the body. They produce clear perspiration consisting primarily of water, salts (mostly NaCL), and urea. eccrine sweat glands, under the control of the nervous system, are and important part of the body's heat-regulating apparatus. They secrete perspiration when the external temperature or body temperature is high. When this water-based substance evaporates, it carries excess body heat with it. thus evaporation of greater amounts of perspiration provides and efficient means of dissipating body heat when the capillary cooling system is not sufficient or is unable to maintain body temperature homeostasis.

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Apocrine Glands

Found predominantly in the axillary and genital areas, these glands secrete the basic components of eccrine sweat plus proteins and fat-rich substances. Apocrine sweat is an excellent nutrient medium for the microorganisms typically found on the skin. This sweat is odorless, but when bacteria break down its organic components, it begins to smell unpleasant. The function of apocrine glands is not known, but since their activity increases during sexual foreplay and the glands enlarge and recede with the phases of a woman's menstrual cycle, they may be the human equivalent of the sexual scent glands of other animals.