Integumentary system- Checkpoint

Describe the structure of a hair. What causes "goose bumps"?

Each hair is composed of columns of dead, keratinized epidermal cells bonded together by extracellular proteins. In its normal position, hair emerges at an 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", because the skin around the shaft forms slight elevations.

Why doesn't epidermal wound healing result in scar formation?

Even though the central portion of an epidermal wound may extend to the dermis, the edges of the wound usually involve only slight damage to superficial epidermal cells. OR Not enough layers are damaged. Epidermis is avascular. If wound bleeds you have damaged the dermis. No need for scar tissue in epidermal wound.

What are the three pigments in the skin and how do they contribute to skin color?

Melanin, hemoglobin, and carotene are three pigments that impart a wide variety of colors to skin. The amount of melanin causes the skin's color to vary from pale yellow to reddish brown to black. The red color of the blood is due to hemoglobin, the oxygen-carrying pigment in red blood cells. Carotene is a yellow-orange pigment that gives egg yolk and carrots their color. This precursor of vitamin A, which is used to synthesize pigments needed for vision, is stored in the stratum corneum and fatty areas of the dermis and subcutaneous layer in response to excessive dietary intake.

Describe the parts of a nail.

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.

How does the process of keratinization occur?

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, a process called keratinization. Then they undergo apoptosis. Eventually the keratinized cells slough off and are replaced by underlying cells that in turn become keratinized. The whole process by which cells form in the stratum basale, rise to the surface, become keratinized, and slough off takes about four weeks in an average epidermis of 0.1 mm in thickness.

What are the function of dermis?

Papillary layer ■ Contains capillaries that nourish the stratum germinativum Hair (follicles) ■ Eyelashes and nasal hair keep dust out of eyes and nasal cavities ■ Scalp hair provides insulation from cold for the head Nails (follicles) ■ Protect ends of fingers toes from mechanical injury Receptors ■ Detect changes that are felt as the cutaneous senses: touch, pressure, heat, cold, itch, and pain Sebaceous glands ■ Produce sebum, which prevents drying of skin and hair and inhibits growth of bacteria Ceruminous glands ■ Produce cerumen, which prevents drying of the eardrum Eccrine sweat glands ■ Produce watery sweat that is evaporated by excess body heat to cool the body Arterioles ■Dilate in response to warmth to increase heat loss ■ Constrict in response to cold to conserve body heat ■ Constrict in stressful situations to shunt blood to more vital organs

Contrast the locations and functions of sebaceous (oil) glands, sudoriferous (sweat) glands, and ceruminous glands.

Sebaceous glands ■ Produce sebum, which prevents drying of skin and hair and inhibits growth of bacteria Eccrine sweat glands ■ Produce watery sweat that is evaporated by excess body heat to cool the body Ceruminous glands ■ Produce cerumen, which prevents drying of the eardrum

What are the functions of epidermis?

Stratum corneum (keratin) ■ Prevents loss or entry of water ■ If unbroken, prevents entry of pathogens and most chemicals Stratum germinativum (stratum basale) ■ Continuous mitosis produces new cells to replace worn-off surface cells ■ Produces antimicrobial defensins ■ Cholesterol is changed to vitamin D on exposure to UV rays Langerhans cells ■ Phagocytize foreign material and stimulate an immune response by lymphocytes Merkel cells ■ Receptors for sense of touch Melanocytes ■ Produce melanin on exposure to UV rays Melanin ■ Protects living skin layers from further exposure to UV rays

What structures are included in the integumentary system?

The integumentary system consists of the skin, hair, oil and sweat glands, nails, and sensory receptors.

In what two ways does the skin help regulate body temperature?

The skin participates in thermoregulation by liberating sweat at its surface and by adjusting the flow of blood in the dermis.

How does the skin serve as a protective barrier?

The skin provides physical, chemical, and biological barriers that help protect the body. Chemical- Keratin protects underlying tissues from microbes, abrasion, heat, and chemicals and the tightly interlocked keratinocytes resist invasion by microbes. Physical - Lipids released by lamellar granules inhibit evaporation of water from the skin surface, thus guarding against dehydration; they also retard entry of water across the skin surface during showers and swims. The oily sebum from the sebaceous glands keeps skin and hairs from drying out and contains bactericidal chemicals that kill surface bacteria. The acidic pH of perspiration retards the growth of some microbes. Biological - The pigment melanin helps shield against the damaging effects of ultraviolet light. Two types of cells carry out protective functions that are immunological in nature. Epidermal Langerhans cells alert the immune system to the presence of potentially harmful microbial invaders by recognizing and processing them, and macrophages in the dermis phagocytize bacteria and viruses that manage to bypass the Langerhans cells of the epidermis.

How are epidermal ridges formed?

These epidermal ridges are produced during the third month of fetal development as downward projections of the epidermis into the dermis between the dermal papillae of the papillary region. The epidermal ridges increase the surface area of the epidermis and thus increase the grip of the hand or foot by increasing friction. Because the ducts of sweat glands open on the tops of the epidermal ridges as sweat pores, the sweat and ridges form fingerprints (or footprints) upon touching a smooth object.

What sensations arise from stimulation of neurons in the skin?

Touch, pressure, vibration, tickling, warmth, coolness and pain Cutaneous sensations are sensations that arise in the skin, including tactile sensations—touch, pressure, vibration, and tickling And thermal sensations - warmth and coolness. Another sensation is pain, usually is an indication of impending or actual tissue damage.