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Chapter 5

Terms in this set (57)

5.1 Structure of the Skin
1. The integumentary system consists of the skin, hair, oil and sweat glands, nails, and sensory
receptors.
2. The skin is the largest organ of the body in surface area and weight. The principal parts of the skin
are the epidermis (superficial) and dermis (deep).
3. The subcutaneous layer (hypodermis) is deep to the dermis and not part of the skin. It anchors the dermis
to underlying tissues and organs, and it contains pacinian (lamellated) corpuscles.
4. The types of cells in the epidermis are keratinocytes, melanocytes, Langerhans cells, and Merkel cells.
5. The epidermal layers, from deep to superficial, are the stratum basale, stratum spinosum, stratum granulosum,
stratum lucidum (in thick skin only), and stratum corneum (see Table 5.1). Stem cells in the
stratum basale undergo continuous cell division, producing keratinocytes for the other layers.
6. The dermis is composed of dense irregular connective tissue containing collagen and elastic fibers. It
is divided into papillary and reticular regions. The papillary region contains thin collagen and fine elastic
fibers, dermal papillae, and Meissner corpuscles. The reticular region contains bundles of thick collagen
and some coarse elastic fibers, fibroblasts and macrophages, adipose tissue, hair follicles, nerves,
sebaceous (oil) glands, and sudoriferous (sweat) glands. (See Table 5.2.)
7. Epidermal ridges provide the basis for fingerprints and footprints.
8. The color of skin is due to melanin, carotene, and hemoglobin.
9. In tattooing, a pigment is deposited with a needle in the dermis. Body piercing is the insertion of jewelry
through an artificial opening.
5.2 Accessory Structures of the Skin
1. Accessory structures of the skin—hair, skin glands, and nails—develop from the embryonic epidermis.
2. A hair consists of a shaft, most of which is superficial to the surface, a root that penetrates the dermis
and sometimes the subcutaneous layer, and a hair follicle.
3. Associated with each hair follicle is a sebaceous (oil) gland, an arrector pili muscle, and a hair root
plexus.
4. New hairs develop from division of hair matrix cells in the bulb; hair replacement and growth occur
in a cyclical pattern consisting of growth, regression, and resting stages.
5. Hairs offer a limited amount of protection—from the sun, heat loss, and entry of foreign particles into
the eyes, nose, and ears. They also function in sensing light touch.
Anatomy Overview - The Skin
Figure 5.2 - Cells in the
Epidermis
Figure 5.3 - Layers of
the Epidermis
Anatomy Overview - Hair
Anatomy Overview - Nails
Figure 5.4 - Hair
Review Resource
Hives Reddened elevated patches of skin that are often itchy. Most
commonly caused by infections, physical trauma, medications,
emotional stress, food additives, and certain food allergies. Also
called urticaria (u¯ r-ti-KAR-e¯ -a).
Keloid (KE¯ -loid; kelis tumor) An elevated, irregular darkened area
of excess scar tissue caused by collagen formation during healing.
It extends beyond the original injury and is tender and frequently
painful. It occurs in the dermis and underlying subcutaneous tissue,
usually after trauma, surgery, a burn, or severe acne; more
common in people of African descent.
Keratosis (ker'-a-TO¯ -sis; kera- horn) Formation of a hardened
growth of epidermal tissue, such as solar keratosis, a premalignant
lesion of the sun-exposed skin of the face and hands.
Laceration (las-er-A¯ -shun; lacer- torn) An irregular tear of the skin.
Lice Contagious arthropods that include two basic forms. Head lice
are tiny, jumping arthropods that suck blood from the scalp. They
lay eggs, called nits, and their saliva causes itching that may lead
to complications. Pubic lice are tiny arthropods that do not jump;
they look like miniature crabs.
Papule (PAP-u¯ l; papula pimple) A small, round skin elevation less
than 1 cm in diameter. One example is a pimple.
Pruritus (proo-RI¯-tus; pruri- to itch) Itching, one of the most common
dermatological disorders. It may be caused by skin disorders
(infections), systemic disorders (cancer, kidney failure), psychogenic
factors (emotional stress), or allergic reactions.
Psoriasis (so¯-RI¯-a-sis) A common and chronic skin disorder in which keratinocytes
divide and move more quickly than normal from the stratum
basale to the stratum corneum. As a result, the surface cells
never get a chance to cycle into the later keratinizing stages. The surface
cells are shed immaturely and on the scalp are called dandruff.
Tinea corporis (TIN-e¯-a KOR-po-ris) A fungal infection characterized
by scaling, itching, and sometimes painful lesions that may appear
on any part of the body, also known as ringworm. Fungi thrive in
warm, moist places such as skin folds of the groin, where it is
known as tinea cruris (KROO-ris) (jock itch) or between the toes,
where it is called tinea pedis (PE-dis) (athlete's foot).
Topical In reference to a medication, applied to the skin surface
rather than ingested or injected.
Wart Mass produced by uncontrolled growth of epithelial skin cells;
caused by a papillomavirus. Most warts are noncancerous.
CHAPTER REVIEW AND RESOURCE SUMMARY 179
Review Resource
6. Lanugo of the fetus is shed before birth. Most body hair on males is terminal (coarse, pigmented);
most body hair on females is vellus (fine).
7. Sebaceous (oil) glands are usually connected to hair follicles; they are absent from the palms and soles.
Sebaceous glands produce sebum, which moistens hairs and waterproofs the skin. Clogged sebaceous
glands may produce acne.
8. There are two types of sudoriferous (sweat) glands: eccrine and apocrine. Eccrine sweat glands have
an extensive distribution; their ducts terminate at pores at the surface of the epidermis. Eccrine sweat
glands are involved in thermoregulation and waste removal and are stimulated during emotional stress.
Apocrine sweat glands are limited to the skin of the axillae, groin, and areolae; their ducts open into
hair follicles. Apocrine sweat glands are stimulated during emotional stress and sexual excitement. (See
Table 5.3.)
9. Ceruminous glands are modified sudoriferous glands that secrete cerumen. They are found in the external
auditory canal (ear canal).
10. Nails are hard, dead keratinized epidermal cells over the dorsal surfaces of the distal portions of the
digits. The principal parts of a nail are the nail body, free edge, nail root, lunula, eponychium, and nail
matrix. Cell division of the nail matrix cells produces new nails.
5.3 Types of Skin
1. Thin skin covers all parts of the body except for the palms, palmar surfaces of the digits, and the soles.
2. Thick skin covers the palms, palmar surfaces of the digits, and soles. (See Table 5.4.)
5.4 Functions of the Skin
1. Skin functions include body temperature regulation, blood storage, protection, sensation, excretion and
absorption, and synthesis of vitamin D.
2. The skin participates in thermoregulation by liberating sweat at its surface and by adjusting the flow
of blood in the dermis.
3. The skin provides physical, chemical, and biological barriers that help protect the body.
4. Cutaneous sensations include tactile sensations, thermal sensations, and pain.
5.5 Maintaining Homeostasis: Skin Wound Healing
1. In an epidermal wound, the central portion of the wound usually extends down to the dermis; the
wound edges involve only superficial damage to the epidermal cells.
2. Epidermal wounds are repaired by enlargement and migration of basal cells, contact inhibition, and
division of migrating and stationary basal cells.
3. During the inflammatory phase of deep wound healing, a blood clot unites the wound edges, epithelial
cells migrate across the wound, vasodilation and increased permeability of blood vessels enhance
delivery of phagocytes, and mesenchymal cells develop into fibroblasts.
4. During the migratory phase, fibroblasts migrate along fibrin threads and begin synthesizing collagen
fibers and glycoproteins.
5. During the proliferative phase, epithelial cells grow extensively.
6. During the maturation phase, the scab sloughs off, the epidermis is restored to normal thickness, collagen
fibers become more organized, fibroblasts begin to disappear, and blood vessels are restored to
normal.
5.6 Development of the Integumentary System
1. The epidermis develops from the embryonic ectoderm, and the accessory structures of the skin (hair,
nails, and skin glands) are epidermal derivatives.
2. The dermis is derived from mesodermal cells.
5.7 Aging and the Integumentary System
1. Most effects of aging begin to occur when people reach their late forties.
2. Among the effects of aging are wrinkling, loss of subcutaneous adipose tissue, atrophy of sebaceous
glands, and decrease in the number of melanocytes and Langerhans cells.
Anatomy Overview - The Integument
and Disease Resistance
Animation - Nonspecific Disease
Resistance
Figure 5.6 - Skin Wound
Healing