Chapter 5 Checkpoint Questions and My Own Answers

Checkpoint Questions and MY own answers: 1. What structures are included in the integumentary system? - integumentary system includes the skin, hair, oil and sweat glands, nails and sensory receptors. 2. 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.” 3. What are the structural and functions differences between the epidermis and dermis? 4. How are epidermial ridges formed? - They 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 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 hand or foot by increasing friction. 5. What are the three pigments in the skin and how do they contribute to skin color? - Melanin: the amount of melanin causes the skin’s colour to vary from pale yellow to reddish-brown to black. The number of melanocytes is about the same in all people, differences in skin colour are due mainly to the amount of pigment the melanocytes produce and transfer to keratinocytes. Freckles are melanin that accumulates in certain areas. These people are genetically predisposed. Age (liver) spots are similar to freckles in that they are accumulations of melanin. They are darker than freckles and are a result of sun exposure and do not fade away over winter months like freckles do. More common In adults over 40 years. A mole is a benign localized overgrowth of melanocytes and usually develops in childhood, and is called a nevus or a mole. Melanin serves as a protective function by absorbing UV radiation and preventing damage to DNA in epidermal cells, and neutralizes free radicals that form in the skin following damage by UV radiations. - Hemoglobin: the reddish colour to skin tones. “Dark-skinned individuals have large amounts of melanin in the epidermis, so their skin colour ranges from yellow to reddish-brown to black. Light-skinned indiciduals have little melanin in the epidermis. Thus, the epidermis appears translucent, and skin colour ranges from pink to red depending on the oxygen content of the blood moving through capillaries in the dermis. The red colour is due to hemoglobin, the oxygen-carrying pigment in red blood cells. - Carotene: Is the yellow-orange pigment. This is a 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. 6. What is a tattoo? What are some potential problems associated with body piercing? - tattooing is a permanent colouration of the skin in which a foreign pigment is deposited with a needle into the dermis. - Potential complications of body piercing are infections, allergic reactions, and anatomical damage (such as nerve damage or cartilage deformation). Body piercing jewelry may interfere with certain medical procedures such as masks used for resuscitation, airway management procedures, urinary catheterization, radiographs, and delivery of a baby. 7. Describe the structure of a hair. What causes “goose bumbs”? - shaft is the superficial portion of the hair, which projects above the surface of the skin. - the root is the portion of hair deep to the shaft that penetrates into the dermis, and sometimes into the subcutaneous layer. The shaft and root consist of three concentric layers of cells: medulla (inner), cortex (middle) and cuticle (outer) of the hair. -Hair follicle surrounds the root of the hair, which is made up of an external root sheath and an internal root sheath, together referred to as an epithelial root sheath. -The external is the downward continuation of the epidermis. -The internal is produced by the matrix and forms a 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. The dense dermis surrounding the hair follicle is called the dermal root sheath. -The bulb is the base of each hair follicle and its surrounding dermal root sheath is an onion shaped structure. This structure houses a nipple-shaped indentation, the papilla of the hair, which contains areolar connective tissue and many blood vessels that nourish the growing hair follicle. The bulb also contains a germinal layer of cells called the hair matrix. The hair matrix cells arise from the stratum basale, the site of cell dicision. Hence, hair matrx cells are responsible for the growth of existing aris, 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 internal root sheath. - sebaceous (oil) glands and a bundle of smooth muscle cells are also associated with hairs. The smooth muscle is the arrector pili. It extends from the superficial dermis of the skin to the dermal root sheath around the side of the hair follicle. In its 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. - Surrounding each hair follicle are dendrites of neurons that form a hair root plexus which is sensitive to touch. The hair root plexuses generate nerve impulses if their hair shafts are moved. 8. Contrast the locations and functions of sebaceous (oil) glands, sudoriferous (sweat) glands, and ceruminous glands. - sebaceous (oil) glands are simple, branched acinar (rounded) glands. The secreting portion of a sebaceous gland lies in the dermis and usually opens into the neck of a hair follicle. Sebaceous glands secrete an oily substance called sebum, a mixture of triglycerides, cholesterol, proteins, and inorganic salts. Sebum coats the surface of hairs and helps keep them from drying and becoming brittle. Sebum also prevents excessive evaporation of water from the skin, keeps the skin soft and pliable, and inhibits the growth of some (but not all) bacteria. - Sudoriferous glands: the cells of these glands release sweater, or perspiration, into hair follicles or onto the skin surgace through pores. Sweat glands are divided into two mani types, eccrine and apocrine, based on their structures and type of secretion. 9. Describe the parts of a nail. Explained from top to bottom of nail. - Free edge: extends past the finger or toe - Nail body (plate): Is the visible portion of the nail, pinkish in colour due to the underlying capillaries in the dermis. - Nail Bed: Is the skin below the nail plate - Lunula: Is the thick white crescent-shaped area of the proximal end of the nail body. - Eponychium (cuticle): the stratum corneum of the epidermis. - Nail Root: the portion that is not visible/ buried in a fold of skin underneath. - Nail Matrix: is the epithelium proximal to the nail root. It contains dividing cells, which produce new nails. 10. What criteria are used to distinguish thin and thick skin? - Thin (hairy) skin - thick (hairless) skin -The greatest contributor to epidermal thickness is the increased number of layers in the stratum corneum. This arises in response to the greater mechanical stress in regions of thick skin. - thin skin is lacking in stratum lucidum (thinner strata spinosum and corneum) - Thick skin has stratum lucidum present (thicker strat spinosum and corneum). Table 5.4 on page 156 compares think and thick skin 11. In what two ways does the skin help regulate body temperature? - By liberating sweat at its surface and by adjusting the flow of blood in the dermis. 12. How does the skin serve as a protective barrier? - Keratin protects underlying tissues from microbes, abrasion, heat, and chemicals, and the tightly interlocked keratinocytes resist invasion by microbes. - Lipids inhibit evaporation of water from the skin surface, thus guarding against dehydration. - Oily sebum keeps skin and hairs from drying out. - Pigment melanin helps shield against the damaging effects of ultraviolet light. - Intraepidermal macrophage alert the immune system to the presence of potentially harmful microbial invaders by recognizing and processing them. - Macrophages in the dermis phagocytize bacteria and viruses that manage to bypass the intraepidermal macrophages of the epidermis. 13. What sensations arise from stimulation of neurons in the skin? - Cutaneous sensations are the sensations that arise in the skin, including tactile sensations – touch, pain, pressure, vibration, and tickling – as well as thermal sensations such as warmth and coolness. 14. What types of molecules can penetrate the stratum corneum? - about 400 mL of water evaporates through it daily. (H2O) - Lipid soluble materials penetrate the skin ( Vitamins ADEK) toxic material such as acetone (nail polish remover), carbon tetrachloride (dry-cleaning fluid) and salts of heavy metals such as lead, mercury, and arsenic as well as the substances in poison oak/ivy. 15. Why doesn’t epidermal wound healing result in scar formation? - Because the epidermal wound is avascular, bleeding does not occur and therefore does not need scar tissue. 16. Which structures develop as downgrowths of the stratum basale? - Sudoriferous (sweat) glands are derived from downgrowths (buds) of the stratum basale of the epidermis into the dermis. 17. What factors contribute to the susceptibility of aging skin to infection? - Intraepidermal macrophages decrease in number and become less-efficient phagocytes, therefore decreasing the skins immune responsiveness. Moreover, decreased size of sebaceous glands leads to dry and broken skin that is more susceptible to infection. - production of sweat decreased which (probably) contributes to the increased incidence of heat stroke in the elderly. -Theres a decrease in the number of functioning melanocytes, resulting in gray hairs and atypical skin pigmentation. Notes: - Functions of the integumentary system: 1. Regulates body temperature 2. stores blood 3. Protects body from external environment 4. Detects cutaneous sensations 5. Excretes and absorbs substances 6. Synthesizes Vitamin D - Epidermis (composed of epithelial tissue) is avascular; the dermis (composed of thicker and deeper connective tissue) is vascular. - In most regions of the body the epidermis has four strata or layers – stratum basale, stratum spinosum, stratum granulosum, and a thin stratum corneum; this is called thin skin. Where exposure to friction is greatest, such as fingertips, palms, and soles, the epidermis has five layers – stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and a thick stratum corneum; this is called thick skin. - stratum lucidum is the extra 5th layer in “thick skin” - The stratum lucidum consists of four to six layers of flattened clear, dead keratinocytes that contain large amounts of keratin and thickened plasma membranes. - The stratum nasale is also known as the stratum germinativum to indicate its role in forming new cells. - Psoriasis is a common and chronic skin disorder in which keratinocytes divide and ove more quickly than normal from the stratum basale to the stratum corneum. They are shed prematurely in as little as 7 to 10 days. The immature keratinocytes make an abnormal keratin, which forms flaky, silvery scales at the skin surface, most often on the knees, elbows, and scalp (dandruff). Effective treatments – carious topical ointments and ultraviolet phototherapy- suppress cell division, decrease the rate of cell growth, or inhibit keratinization. - Table 5.1 on page 147 has a summary of the epidermal strata (basale, spinosum, etc). - Lanugo is very fine, non-pigmented downy hair that cover the body of the fetus, by the 5th month hair follicles produce lanugo. Prior to birth the lanugo of the eyebrows, eyelashed and scalp are shed and replaced by long, coarse, heavily pigmented hairs called terminal hairs. The Lanugo of the rest of the body are replaced by vellus hairs, commonly referred to as “peach fuzz” which are short, fine, pale hairs that are barely visible to the naked eye. - During adulthood, about 95% of body hair on males is terminal hair and 5% is vellus hair; on females, about 35% of body hair is terminal hair and 65% is vellus hair. - In contrast to eccrine sweat glands, apocrine sweat glands are not active during thermoregulatory sweating and, therefore, do not play a role in thermoregulation. - Table 5.3 on page 154 has a summary of skin glands (sebaceous, eccrine, apocrine, ceruminous glands). - Calcitriol is the most active form of Vitamin D… Calcitriol is a hormone that aids in the absorption of calcium from foods in the gastrointestinal tract into the blood. Vitamin D is believed to enhance phagocytic activity, increase the production of antimicrobial substances in phagocytes, regulate immune functions, and help reduce inflammation. - Vernix caseosa is the substance that covers and protects the skin of the fetus from the constant exposure to the amniotic fluid in which it is bathed. It also facilitates the birth of the fetus because it is slippery in nature and protects the skin from being damaged by the nails. - the epidermis develops from ectoderm and the dermis develops from mesoderm. - First degree burn only involves the epidermis. Characterized by mild pain and erythema (redness) but no blisters. - Second degree burn destroys the epidermis and part of the dermis. Some skin functions are lost. Redness, blister formation, edema, and pain result. - First and second degree burns are collectively referred to as partial-thickness burns. - A third degree burn or full-thickness burn destroys the epidermis, dermis and subcutaneous layer. Most skin functions are lost. These burns appear marble-white to mahogany coloured to charred, dry wounds. There is marked edema, and the burned region is numb because sensory nerve endings have been destroyed.