HW Chapter 5 (part 2) PDF

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HOMEWORK #5 Chapter 5 part 2 NAME:

BIOL 1303

Tra Nguyen

1. List the two layers of the dermis. For each layer, name the specific type of tissue that makes up the layer, and give a description of the features of that layer.  

The papillary layer consists of areolar tissue. It contains the capillaries, lymphatic vessels, and sensory neurons that supply the surface of the skin. The reticular layer lies deep to the papillary layer. It consists of an interwoven meshwork of dense irregular connective tissue containing both collagen and elastic fibers. Bundles of collagen fibers extend superficially beyond the reticular layer to blend into those of the papillary layer, so the boundary between the two layers is indistinct. Collagen fibers of the reticular layer also extend into the deeper hypodermis. In addition to extracellular protein fibers, the dermis contains all the cells of connective tissue proper.

2. List some of the structures that are found in the dermis. Accessory structures of epidermal origin, such as hair follicles and sweat glands, extend into the dermis. In addition, the reticular and papillary layers of the dermis contain networks of blood vessels and nerve fibers. 3. Describe what epidermal ridges are. Describe what dermal papillae are. What is the significance of these two structures?

 Epidermal ridges are any of the ridges of the epidermis of the palms and soles, where the sweat pores open. Papillae lie atop larger mounds called dermal ridges, which in turn cause the overlying epidermis to form epidermal ridges. The ridge pattern is significant because they are unique to the individual.  Dermal papillae are an important part of skin anatomy. They contain the vascular loops and capillaries that transport oxygen and nutrients from the blood system to the epidermis, while simultaneously removing waste products from the epidermal layer. The epidermis mainly functions as a protective, exterior layer and has no nerve cells of its own, but the dermal papillae has specialized nerve endings that are extremely sensitive and provide vital sensory input from this outermost stratum of skin. Moreover, dermal papillae are important in the formation of hair follicles, and are involved in the cycle of hair growth and shedding. 4. Describe cleavage lines and their medical significance. Most of the collagen and elastic fibers at any location are arranged in parallel bundles oriented to resist the forces applied to the skin during normal movement. The resulting pattern of fiber bundles in the skin establishes cleavage lines. Cleavage lines are clinically significant. A cut parallel to a cleavage line will usually remain closed and heal with little scarring. A cut at right angles to a cleavage line will be pulled open as severed elastic fibers recoil, resulting in greater scarring. For these reasons, surgeons choose to make incisions parallel to cleavage lines. 5. What types of tissue make up the hypodermis? What are some of the functions of the hypodermis?

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The hypodermis is quite elastic. It consists of areolar tissue and adipose tissue. The hypodermis is not a part of the integument, but it is important in stabilizing the position of the skin in relation to underlying tissues, such as skeletal muscles or other organs, while permitting independent movement. 6. What is the name of the collection of blood vessels found near the junction of the dermis and hypodermis? What is the name of the collection of blood vessels that travel from the hypodermis/dermis junction, through the reticular layer of the dermis, and into the dermal papillae? Hemoglobin. 7. With regards to melanin production, what accounts for the differences in skin tone exhibited by different individuals? The differences in skin pigmentation among individuals do not reflect different numbers of melanocytes, but rather, different levels of melanin synthesis. 8. For each of the following alterations to skin coloration, give a brief description of the condition and describe what causes it:

a. Cyanosis:  Bluish skin tint.  Caused by severe reduction in blood flow or oxygenation. b. Jaundice:  Buildup of bile produced by liver.  Yellow color. c. Albinism:  Caused by the defective genes in the result of a reduced amount or absence of melanin production.  Little or no color. 9. Describe each of the following types of skin markings: a. Hemangiomas – A birthmark often appearing as a rubbery, bright red nodule of extra blood vessels. A hemangioma grows during the first year of life, and then recedes over time. It can appear on the face, scalp, chest, or back. b. Freckles – Small, pigmented areas on relatively pale skin. These spots typically have an irregular border. They represent the areas serviced by melanocytes that are producing larger-than-average amounts of melanin. Freckles tend to be most abundant on surfaces such as the face, probably due to its greater exposure to the sun. c. Nevi (moles) – Small, pigmented spots on the skin that usually appear during childhood or adolescence, although they are sometimes present at birth. They are composed of clusters of pigmented cells called melanocytes. People may develop more moles during adolescence and pregnancy, and existing ones may enlarge or darken somewhat during these times.

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10. List three functions of hair. Be sure to indicate (if applicable) which specific collections of hair carry out these functions. The hairs and hair follicles on your body have important functions. The 500,000 or so hairs on your head protect your scalp from ultraviolet radiation, help cushion light impacts to the head, and insulate the skull. The hairs guarding the entrances to your nostrils and external ear canals help keep out foreign particles and insects. Your eyelashes do the same for the surface of the eye. Eyebrows are important because they help keep sweat out of your eyes. Hairs are also extremely important as sensory receptors. 11. When looking at a cross section of a hair, which of the three layers of the hair contains the keratinocytes? Stratum spinosum and stratum granulosum.

12. Describe the makeup of a hair follicle. What layer of the integument is the follicle derived from? The hair follicle:  Is located deep in dermis.  Produces nonliving hairs.  Is wrapped in a dense connective tissue sheath.  Base is surrounded by sensory nerves (root hair plexus). 13. Describe the features and functions of arrector pili muscles. A bundle of smooth muscle cells forms the arrector pili muscle. It extends from the papillary layer of the dermis to the connective tissue sheath surrounding the hair follicle. When stimulated, the arrector pili muscle contracts, pulling on the follicle and forcing the hair to stand erect. Contraction may be the result of emotional states, such as fear or rage, or a response to cold, producing “goose bumps.” In a furry mammal, this action increases the thickness of its insulating coat. Humans do not receive any comparable insulating benefits, but the response persists. 14. What stratum of the epidermis are nails produced from? What substance are nails composed of? What specific structure gives rise to the nails? Nails are keratinized epidermal cells that produced from stratum corneum. Nails protect the exposed dorsal surfaces of the tips of the fingers and toes. They also help limit distortion of the digits from mechanical stress. 15. List the four types of exocrine glands found in the integument. What layer of the integument are these glands housed in? What layer of the integument are these glands all derived from? 

Sebaceous glands (oil glands):

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 Holocrine glands.  Secrete sebum. Sweat glands: 3

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 Two types: apocrine glands and merocrine (eccrine) glands.  Watery secretions. Mammary glands: Produce milk. Ceruminous glands:  Produce cerumen (earwax).  Protect the eardrum.

16. What secretory mechanism do sebaceous glands use? List three functions of sebum. Sebaceous glands release the lipid product through holocrine secretion, a process that involves the rupture of the secretory cells. The secreted lipid product, called sebum, is a mixture of triglycerides, cholesterol, proteins, and electrolytes. Sebum inhibits the growth of bacteria, lubricates and protects the keratin of the hair shaft, and conditions the surrounding skin. 17. List the two types of sweat glands. For each gland type, give a description of the contents of the sweat they produce. 

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Apocrine sweat glands:  Found in armpits, around nipples, and groin.  Secrete products into hair follicles.  Produce sticky, cloudy secretions.  Break down and cause odors.  Surrounded by myoepithelial cells:  Squeeze apocrine gland secretions onto skin surface.  In response to hormonal or nervous signal. Merocrine (Eccrine) sweat glands:  Widely distributed on body surface.  Especially on palms and soles.  Coiled, tubular glands.  Discharge directly onto skin surface.  Sensible perspiration.  Water, salts, and organic compounds.

18. What is the purpose of merocrine sweat glands? Where do the ducts of merocrine sweat glands deliver their sweat to? What mechanism of secretion do merocrine sweat glands make use of?  

Merocrine sweat glands are coiled, tubular glands that discharge their secretions directly onto the surface of the skin. The functions of merocrine sweat gland activity include:  Cooling the surface of the skin to reduce body temperature.  Excreting Water and Electrolytes.  Providing protection from environmental hazards by flushing microorganisms and harmful chemicals from skin.

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19. What is the function of apocrine sweat glands? Where do the ducts of apocrine sweat glands deliver their sweat to? Why is the term apocrine sweat gland misleading? In the armpits (axillae), around the nipples, and in the pubic region, apocrine sweat glands secrete their products into hair follicles. These coiled, tubular glands produce a sticky, cloudy, and potentially odorous secretion. The name apocrine was originally chosen because it was thought the gland cells used an apocrine method of secretion. We now know that they rely on merocrine secretion, but the name has not changed. 20. Where are the ceruminous glands located? List three functions of cerumen. Ceruminous glands are modified sweat glands in the passageway of the external ear. Their secretions combine with those of nearby sebaceous glands, forming a mixture called cerumen, or earwax. Together with tiny hairs along the ear canal, earwax helps trap foreign particles, preventing them from reaching the eardrum. 21. For each of the following types of burns, give a description of the burn, be sure to indicate if the is a partial-thickness or full-thickness burn, and whether the burn is potentially fatal: a. First-degree burn: First-degree burns cause minimal skin damage. They are also call “superficial burns” because they affect the outermost layer of skin. Signs of a first-degree burn include redness, minor inflammation or swelling, pain, dry, peeling skin occurs as the burn heals. Since this burn affects the top layer of skin, the signs and symptoms disappear once the skin cells shed. First-degree burns usually heal within 7 to 10 days without scarring. b. Second-degree burn: Second-degree burns are more serious because the damage extends beyond the top layer of skin. This type burn causes the skin to blister and become extremely red and sore. Some blisters pop open, giving the burn a wet or weeping appearance. Over time, thick, soft, scab-like tissue called fibrinous exudate may develop over the wound. Some second-degree burns take longer than three weeks to heal, but most heal within two to three weeks without scarring, but often with pigment changes to the skin. c. Third-degree burn: Third-degree burns are the most severe. They cause the most damage, extending through every layer of skin. There is a misconception that third-degree burns are the most painful. However, with this type of burn the damage is so extensive that there may not be any pain because of nerve damage. Depending on the cause, the symptoms third-degree burns can exhibit include waxy, white color, char, dark brown color, raised and leathery texture, blisters that do not develop. 22. Describe the rule of nines. How can the rule of nines be used to potentially help a burn victim? Rule of nines: A formula for estimating the percentage of adult body surface covered by burns by assigning 9% to the head and each arm, twice 9% (18%) to each leg and the anterior and posterior trunk, and 1% to the perineum. This is modified in infants and children because of the proportionately larger head size.

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