Chapter 5 Flashcards
Integumentary system
System composed of the skin, hair, oil and sweat glands, nails, and sensory receptors.
Skin
AKA cutaneous membrane; covers the external surface of the body and is the largest organ of the body in weight.
What are the two main parts that skin consists of?
Epidermis and dermis
Epidermis
The superficial, thinner portion, which is composed of epithelial tissue; is avascular (therefore, if you cut the epidermis, there is no bleeding); composed of keratinized stratified squamous epithelium.
What are the four principle types of cells found in the epidermis?
Keratinocytes, melanocytes, intraepidermal macrophages, and tactile epithelium
Keratinocytes
~90% of epidermal cells; arranged in four or five layers and produce the protein keratin and lamellar granules.
Keratin
A tough fibrous protein that helps protect the skin and underlying tissues from abrasions, heat, microbes, and chemicals.
Lamellar granules
Release a water-repellent sealant that decreases water entry and loss and inhibits the entry of foreign materials
Melanocytes
~8% of epidermal cells; develop from the ectoderm of a developing embryo and produce the pigment melanin. Their long, slender projections extend between the keratinocytes and transfer melanin granules to them. Once inside the keratinocytes, the melanin granules cluster to form a protective veil over the nucleus, on the side towards the skin surface. They do this to shield the nuclear DNA from damage by UV light. Although their melanin granules effectively protect keratinocytes, melanocytes themselves are particularly susceptible to damage by UV light.
Melanin
A yellow-red, or brown-black pigment that contributes to skin color and absorbs damaging ultraviolet (UV) light.
Intraepidermal macrophages
AKA Langerhans cells; arise from red bone marrow and migrate to the epidermis, where they constitute a small fraction of the epidermal cells; they participate in immune responses mounted against microbes that invade the skin and are easily damaged by UV light; their role in the immune response is to help other cells of the immune system recognize an invading microbe and destroy it.
Tactile epithelium
AKA Merkel cells; are the least numerous of the epidermal cells; they are located in the deepest layer of the epidermal cells, where they contact the tactile discs (AKA Merkel’s disks); tactile epithelial cells and tactile disks detect touch sensations.
Subcutaneous layer
AKA the hypodermis; deep to the dermis, but not part of the skin; this layer consists of areolar and adipose tissues. Fibers that extend from the dermis anchor the skin to the subcutaneous layer, which in turn attaches to underlying fascia, the connective tissue around muscles and bones; the subcutaneous layer serves as a storage depot for fat and contains large blood vessels that supply the skin.
Lamellated corpuscles
AKA Pacinian corpuscles; nerve endings that are sensitive to pressure; the subcutaneous layer, and sometimes the dermis, contain these.
What are the layers of the epidermis?
Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.
Stratum basale
Deepest layer, composed of single row of cuboidal or columnar keratinocytes that contain scattered keratin intermediate filaments (tonofilaments); stem cells undergo cell division to produce new keratinocytes; melanocytes and tactile epithelial cells associated with tactile discs are scattered among keratinocytes.
Stratum spinosum
Eight to ten rows of many-sided keratinocytes with bundles of keratin intermediate filaments; contains projections of melanocytes and intraepidermal macrophages.
Stratum granulosum
Three to five rows of flattened keratinocytes, in
which organelles are beginning to degenerate; cells contain the protein keratohyalin (converts keratin intermediate filaments into keratin) and lamellar granules (release lipid-rich, water-repellent secretion).
Stratum lucidum
Present only in skin of fingertips, palms, and soles; consists of four to six rows of clear, flat, dead keratinocytes with large amounts of keratin.
Stratum corneum
Few to 50 or more rows of dead, flat keratinocytes that contain mostly keratin.
Callus
An abnormal thickening of the stratum corneum.
Keratinization
A process in which newly formed cells in the stratum basale are slowly pushed to the surface. As the cells move from one epidermal layer to the next, they accumulate more and more keratin. Then they undergo apoptosis. Eventually the keratinized cells slough off and are replaced by underlying cells that in turn become keratinized; process takes between four to six weeks.
Epidermal growth factor (EGF)
Hormonelike proteins that play a role in regulating growth of the epidermis.
Dermis
The deeper, thicker connective tissue portion; is vascular (therefore, if a cut penetrates to the dermis, there is bleeding); is composed of dense irregular connective tissue containing collagen and elastic fibers. This network of fibers has great tensile strength (resists pulling or stretching forces); the dermis also has the ability to stretch and recoil easily; it is much thicker than the epidermis.
What are the two regions that the dermis can be divided into?
Papillary region and reticular region
Papillary region
Superficial portion of dermis (about one-fifth); consists of areolar connective tissue with thin collagen and fine elastic fibers; contains dermal ridges that house blood capillaries, corpuscles of touch, and free nerve endings.
Dermal papillae
Small, nipple-shaped structures that project into the undersurface of the epidermis and increase the surface area of the papillary region.
Capillary loops
Blood vessels; all dermal papillae contain them.
Corpuscles of touch
AKA Meissner corpuscles; nerve endings that are sensitive to touch; some dermal papillae contain them.
Free nerve endings
Dendrites that lack any apparent structural specialization; different free nerve endings initiate signals that give rise to sensations of warmth, coolness, pain, tickling, and itching; some dermal papillae contain them.
Reticular region
Deeper portion of dermis (about four-fifths); consists of dense irregular connective tissue with bundles of thick collagen and some coarse elastic fibers. Spaces between fibers contain some adipose cells, hair follicles, nerves, sebaceous glands, and sudoriferous glands.
Extensibility
The ability to stretch; the combination of collagen and elastic fibers in the reticular region allows for this.
Elasticity
The ability to return to original shape after stretching; the combination of collagen and elastic fibers in the reticular region allows for this. (Eg. Seen around joints and in pregnancy and obesity).
Epidermal ridges
Found on the palms, fingers, soles, and toes, and appear either as either as straight lines or as a pattern of loops and whorls; epidermal ridges create a strong bond between the epidermis and dermis in a region of high mechanical stress; the epidermal ridges also increase the surface area of the epidermis and thus increase the grip of the hand or foot by increasing friction; finally, the epidermal ridges greatly increase surface area. Which increases the number of corpuscles of touch and thus increase tactile sensitivity; because the ducts of sweat glands open on the top of epidermal ridges as sweat pores, the sweat and ridges form fingerprints (or footprints) on touching a smooth object.
Explain the basis for different skin colors
Melanin, hemoglobin, and carotene are three pigments that impact a wide variety of colors of skin. The amount of melanin causes the skin’s color to vary from pale yellow to reddish-brown to black. The number of melanocytes, the melanin-producing cells, is about the same in all people, so differences in skin color are due mainly to the amount of pigment the melanocytes produce and transfer to keratinocytes
Hairs
Genetic and hormonal influences largely determine the thickness and the pattern of the hair distribution; hair on the head guards the scalp from injury in the sun’s rays. It also decreases heat loss from the scalp; eyebrows/eyelashes protect the eyes from foreign particles, similar to the way hair in the nostrils and in the external ear canal defends those structures; touch receptors (hair root plexuses) associated with hair follicles are activated whenever a hair is moved even slightly. Thus, hairs also function in sensing light touch.
Hair shaft
Superficial portion of the hair, which projects above the surface of the skin.
Hair root
Portion of the hair deep to the shaft the penetrates into the dermis, and sometimes into the subcutaneous layer.
What three layers do the shaft and root of the hair consist of?
Medulla, cortex, and cuticle of the hair
Medulla (of the shaft and root of the hair)
Inner layer; may be lacking in thinner hair; composed of two or three rows of irregular shaped cells that contain large amounts of pigment granules in dark hair, small amounts of pigment granules in gray hair, and lack pigment granules and the presence of air bubbles in white hair.
Cortex (of the shaft and root of the hair)
Middle layer; forms the major part of the shaft and consists of elongated cells.
Cuticle of the hair
Outermost layer; consists of a single layer of thin, flat cells that are most heavily keratinized. Cuticle cells on the shaft are arranged like shingles on the side of a house, with their free edges pointing toward the end of the hair.
Hair follicle
Made up of an external root sheath and an internal root sheath; external root sheath is a downward continuation of the epidermis; the internal root sheath is produced by a matrix and forms cellular tubular sheath of epithelium between the external root sheath and the hair.
Together, the external and internal root sheath are referred to as the ______.
Epithelial root sheath
Dermal root sheath
Dense dermis surrounding hair follicle.
Hair bulb
Onion-shaped structure that are at the base of each hair follicle and its surrounding dermal root sheath.
Papilla of the hair
Nipple-shaped indentation which contains areolar connective tissue and many blood vessels that nourish the growing hair follicle.
Hair matrix
A germinal layer of cells in the hair bulb; the hair matrix cells arise from the stratum basale, the site of cell division; hence, hair matrix cells are responsible for the growth of existing hairs, and they produce new hairs when old hairs are shed; this replacement process occurs within the same follicle; hair matrix cells also give rise to the cells of the internal root sheath.
Arrector pilli
Smooth muscle cells associated with hairs; extends from the superficial dermis in the skin to the dermal root sheath around the side of the hair follicle; in it’s normal position, hair emerges at a less than 90-degree angle to the surface of the skin. Under physiological or emotional stress, such as cold or fright, autonomic nerve endings stimulate the arrector pili muscles to contract, which pulls the hair shafts perpendicular to the skin surface. This action causes “goose bumps” or “gooseflesh” because the skin around the shaft forms slight elevations.
Hair root plexus
Dendrites of neurons surrounding each hair follicle; are sensitive to touch. Generate nerve impulses if their hair shafts are moved.
What three things do nails consist of?
Nail body, free edge, and nail root
Nail body
AKA plate; is the visible portion of the nail; comparable to the stratum corneum of the epidermis of the skin, with the exception that its flattened, keratinized cells fill with a harder type of keratin and the cells are not shed; below the nail body is a region of epithelium and a deeper layer of dermis; most of the nail body appears pink because of blood flowing through the capillaries in the underlying dermis.
Free edge
Part of the nail body that may extend past the distal end of the digit; the free edge is white because there are no underlying capillaries.
Nail root
Portion of the nail that is buried in a fold of skin; the whitish crescent-shaped area of the proximal end of the nail body is called the lunula. It appears whitish because the vascular tissue underneath does not show through due to a thickened region of epithelium in the area.
Hyponychium
Thickened region of the stratum corneum that is just beneath the free edge; junction between the free edge and skin of the fingertip and secures the nail to the fingertip.
Nail bed
Skin below the nail plate that extends from the lunula to the hyponychium; the epidermis of the nail bed lacks a stratum granulosum.
Eponychium
AKA cuticle; narrow band of epidermis that extends from and adheres to the margin (lateral border) of the nail wall; it occupies the proximal border of the nail and consists of stratum corneum. A hangnail has nothing to do with the nail itself, it is a small torn piece if skin at the side or base of a fingernail or toenail, usually caused by the dryness of the eponychium.
Nail matrix
The portion of the epithelium proximal to the nail root. The superficial nail matrix cells divide mitotically to produce new nail cells. The growth of nails is determined by the rate of mitosis in matrix cells, which is influenced by factors such as a person’s age, health, and nutritional status. Nail growth also varies according to the season, the time of day, and environmental temperature. The growth rate is somewhat slower in toenails. The longer the digit the faster the nail grows.
