Holes Essentials 14e Accessible Ch 06 Accessible PDF

Ch 06: The integumentary system, Skin? © McGraw Hill 1 Learning Objectives 1. Describe the five layers (strata) of the epidermis. 2. Differentiate between thick skin and thin skin. 3. Explain what causes differences in skin color. 4. Characterize the two laye...

Ch 06: The integumentary system, Skin? © McGraw Hill 1 Learning Objectives 1. Describe the five layers (strata) of the epidermis. 2. Differentiate between thick skin and thin skin. 3. Explain what causes differences in skin color. 4. Characterize the two layers of the dermis.. 6. Describe how dermal blood vessels function in temperature regulation. 7. List the functions of the skins. 8. Name ways in which the epidermis protects the body and prevents water loss. 9. Describe the integument’s the Healing of a Deep Wound © McGraw Hill 2  6.1: Introduction to the Integumentary System Skin is the largest organ in the body by weight Accessory structures of the skin: hair, nails, glands, sensory receptors The skin and its accessory organs make up the integumentary system Skin acts as a barrier between internal and the external environment’ Skin has 2 layers:  Epidermis: thin, outer layer of stratified squamous epithelium Dermis: thicker, inner layer of connective tissue, blood vessels, smooth muscle, and nervous tissue Subcutaneous layer (hypodermis): Layer underneath dermis, consisting of areolar and adipose tissues Binds skin to underlying tissues, but is not part of the skin Adipose tissue insulates to conserve body heat 3 © McGraw Hill  The Layers of the Skin and Hypodermis © McGraw Hill (b): Al Telser/McGraw-Hill Education 4  The Epidermis 1 Characteristics of the epidermis: Consists of stratified squamous epithelium Lacks blood vessels Consists of 4 layers in thin skin , 5 layers in thick skin Stratum Basale (or stratum germinativum) is the deepest layer; it consists of dividing cells; it is well-nourished by dermal blood vessels As basal cells divide, older cells, called keratinocytes (due to accumulation of fibrous protein, keratin), migrate toward skin surface As keratinocytes migrate outward, they harden, dehydrate, and die, in a process called keratinization © McGraw Hill 5  The Epidermis 2 The epidermis is important because it protects against water loss, mechanical injury, chemicals, and microorganisms. These 4 layers of the epidermis are found in all areas of the body: Stratum basale: innermost layer, dividing layer Stratum spinosum Stratum granulosum Stratum corneum: outermost layer; dead, flattened, keratinized cells; these are continually being shed from the outer skin surface This layer is found only in the thick skin of the palms and soles: Stratum lucidum: layer between the stratum granulosum and the stratum corneum © McGraw Hill 6  The Epidermis of Thick Skin Access the text alternative for slide images. © McGraw Hill (b): Al Telser/McGraw-Hill Education 7  The Epidermis 3 Melanocytes: Special cells that produce the pigment, melanin Found in deepest layer of epidermis and in dermis Melanin protects DNA of skin cells against damaging effects of UV radiation from the sun Melanin pigment provides skin and hair color; the more melanin is present, the darker the skin or hair will be Eumelanin is brownish-black, and pheomelanin (found in areas such as the lips) is reddish-yellow © McGraw Hill 8  Melanocytes and Melanin Pigment © McGraw Hill (a): Don W. Fawcett/Science Source 9  Skin Color 1 All people have about the same number of melanocytes Skin color is genetically determined and involves the amount of melanin that the melanocytes produce. Its color results from a combination of genetic, environmental, and physiological factors. Genetic differences in skin color result from differing amounts of melanin produced, and in the size and distribution of melanin granules. Exposure to sunlight, UV light from sun lamps, and X-rays cause darkening of skin, due to an increase in melanin. Circulation within dermal blood vessels affects skin color Well-oxygenated blood has a pinkish color, due to hemoglobin Poorly oxygenated blood looks blue, due to deep red tone of the hemoglobin; called cyanosis Yellowish skin color can come from eating too many orange foods with carotene, or from jaundice due to liver disease. © McGraw Hill 10  The Dermis The dermis: Binds the epidermis to underlying tissues Border between epidermis and dermis is uneven, due to epidermal ridges (which extend down toward dermis) and dermal papillae (which extend upward toward epidermis) Genetically determined pattern of friction ridges formed by dermal papillae provide for unique fingerprints The dermis consists of areolar and dense connective tissue, with collagen and elastic fibers within a gel-like ground substance The fibers provide toughness and elasticity to skin Dermal blood vessels carry nutrients to upper layers of skin, to help regulate body temperature The dermis also contains nerve fibers, sensory receptors, hair follicles, sebaceous glands, and sweat glands © McGraw Hill 11  Figure 5.4a Dermal modifications result in characteristic skin markings. Fingerprint. friction Openings of sweat gland Friction ridges: ducts ridges Friction ridges of fingertip (SEM 12×) © McGraw Hill © 2016 Pearson Education, Inc. 12  6.3: Accessory Structures of the Skin Nails: Protective coverings over the ends of fingers and toes Consist of a nail plate overlying a layer of skin surface, called the nail bed Lunula: half-moon-shaped structure at base of nail plate; most actively growing region of the nail root As new cells are produced, older ones are pushed outward and become keratinized, just as in other parts of the skin Keratin of nails is harder than that of the stratum corneum of the rest of the skin © McGraw Hill 13  Longitudinal & Dorsal View of a Nail © McGraw Hill 14  Hair & Hair Follicles Hair can be found in nearly all regions of the skin except palms, soles, lips, nipples, and portions of external genitalia Each hair develops from epithelial stem cells at the base of a tube-like depression called the hair follicle Hair follicles dip down into the dermis or sometimes the subcutaneous layer The deepest part of the hair root is called the hair bulb; it is located at the base of the hair follicle As new cells are formed in the bulb, old cells are pushed outward and become keratinized, and die forming the hair shaft Hair is composed of dead, keratinized epithelial cells © McGraw Hill 15  Hair Follicles Access the text alternative for slide images. © McGraw Hill (b): Al Telser/McGraw-Hill Education 16  Hair Emerging from a Hair Follicle © McGraw Hill CNRI/SPL/Science Source 17  Hair Color and Properties Hair color is determined by genetics Melanin produced by melanocytes is responsible for most hair colors; type and amount of melanin are factors Dark hair contains eumelanin (brownish-black), while blonde and red hair contain more pheomelanin (reddish-yellow) Genetic lack of melanin, or older age, causes albinism (white) Mixture of pigmented and unpigmented hair is gray A bundle of smooth muscle cells, called an arrector pili muscle, attaches to each hair follicle; when it contracts in response to cold temperature or emotional upset, it causes goose bumps © McGraw Hill 18  Skin Glands Sebaceous glands: Holocrine glands; entire cells filled with secretion are released Associated with hair follicles Secrete an oily substance called sebum, that waterproofs and moisturizes the hair shafts and skin Sweat (sudoriferous) glands: Merocrine glands; secretions exit cells via exocytosis 2 types of sweat glands: Eccrine: merocrine glands that respond to body temperature; more abundant type; many found on forehead, neck, back; secrete onto skin surface Apocrine: merocrine glands (incorrectly named) which become active at puberty; respond to fear, emotional upset, pain, or sexual arousal; most numerous in axilla and groin; sweat contains proteins & fats that produce body odor; secrete into hair follicles © McGraw Hill 19  Sebaceous Glands Secrete into Hair Follicles © McGraw Hill Alvin Telser/ McGraw-Hill Education 20  Modified Sweat Glands Ceruminous glands: secrete wax in the ear canal, to trap dust and pathogens Mammary glands: secrete milk to nourish a baby © McGraw Hill 21 6.4: Skin Functions Functions of the skin: Important for maintaining homeostasis Protective covering; prevents many substances and pathogenic microorganisms from entering body Waterproof; slows down water loss by diffusion Melanin pigment protects against UV radiation from the sun Houses sensory receptors for touch, pressure, pain, temperature Excrete wastes Conducts part of the process for making vitamin D Body temperature regulation, via sweat gland activation, and vasodilation or vasoconstriction of dermal blood vessels Protection of underlying tissues © McGraw Hill 22  Role of Skin in Body Temperature Regulation Proper temperature regulation is vital to maintaining optimal metabolic reaction rates The skin plays a major role in temperature regulation, with the hypothalamus controlling the process Active cells, such as those of the heart and skeletal muscle, and the liver, produce heat Heat may be lost to the surroundings from the skin through radiation © McGraw Hill 23  Skin’s Response to Body Temperature Change Responses to excess heat (hyperthermia): Vasodilation of dermal blood vessels; more blood enters skin and is released from the body Sweat glands are activated; as sweat is released, it evaporates, cooling the skin Responses to excess cooling (hypothermia): Vasoconstriction of dermal blood vessels, keeping blood in core Inactivation of the sweat glands Shivering, an involuntary form of skeletal muscle contraction, which causes an increase in cellular respiration; this releases heat as a byproduct © McGraw Hill 24  6.5: Healing of Wounds Inflammation, in which blood vessels dilate and become more permeable, causing tissues to become red and swollen, is the body's normal response to injury Dilated blood vessels bring in fluids, oxygen, nutrients, and immune cells to aid in healing Superficial cuts are filled in by reproducing epithelial cells Deeper injuries, extending into the dermis or subcutaneous layer, require a more extensive response © McGraw Hill 25  The Characteristics of Inflammation TABLE 6.1 Inflammation Symptom Cause Redness Vasodilation, more blood in area Heat Large amount of blood accumulating in area and as a by-product of increased metabolic activity in tissue Swelling Increased permeability of blood vessels, fluids leaving blood go into tissue spaces (edema) Pain Injury to neurons and increased pressure from edema © McGraw Hill 26  The Healing of a Deep Wound 1 The response to a deep injury, extending into the dermis or subcutaneous layer: Involves the formation of a blood clot from the released blood The blood clot and dried tissue fluids form a scab to cover the wound Fibroblasts migrate into the area, and secrete collagen fibers to bind the edges of the wound together Phagocytic cells remove debris and dead cells Damaged tissue is replaced and the scab sloughs off © McGraw Hill 27  The Healing of a Deep Wound 2 Extensive collagen fiber production in the area may form an elevated area called a scar Large wounds leave scars and healing may be accompanied by the formation of rounded masses called granulations: A new branch of a blood vessel grows into the area The vessel is accompanied by a cluster of fibroblasts that begin producing collagen fibers and repairing the wound Eventually, blood vessels are reabsorbed, and the fibroblasts leave, which leaves a scar of collagen fibers. © McGraw Hill 28  Stages in Wound Healing Access the text alternative for slide images. © McGraw Hill 29