Chapter 06 Lecture Outline See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes.

Chapter 6 Integumentary System 2

6.1 Introduction 3

The skin and its accessory organs make up the integumentary system. Organs are body structures composed of two or more different tissues that perform specific functions. The skin and its accessory organs make up the integumentary system. 4

6.2 Skin and its Tissues 5

Responsible for maintaining homeostasis Temperature regulation Functions of the skin Responsible for maintaining homeostasis Temperature regulation Protection of underlying tissues Retard water loss House sensory receptors Synthesize certain biochemicals Excrete wastes Part of the process to make vitamin D 6

The dermis connective tissue, blood vessels, and nervous tissue Layers of the skin An outer epidermis of avascular keratinized stratified squamous epithelium The dermis connective tissue, blood vessels, and nervous tissue The subcutaneous layer (hypodermis) of areolar and adipose tissues Insulates to conserve body heat and impedes entrance of external heat Contains major blood vessels 7

Fig 6.1 8

Epidermis The epidermis is made up of stratified squamous epithelium and lacks blood vessels. The layer of reproducing cells (the stratum basale or stratum germinativum), which lies at the base of the epidermis, is well-nourished by dermal blood vessels. 9

Fig 6.2 10

Epidermis, cont. Cells are pushed outward as new cells are formed, and become keratinized as they die. Four or five layers may be seen: stratum basale, stratum spinosum, stratum granulosum, and stratum corneum are always present and the stratum lucidum is found in the thicker palms and soles. The epidermis is important because it protects against water loss, mechanical injury, chemicals, and microorganisms. 11

Melanocytes pass melanin to nearby cells through cytocrine secretion. Epidermis, cont. Melanocytes, which lie deep in the epidermis and underlying dermis, produce a pigment called melanin that protects deeper cells from the sun's ultraviolet rays and gives color to the skin. Melanocytes pass melanin to nearby cells through cytocrine secretion. 12

Fig 6.3 13

All people have about the same number of melanocytes. Skin Color Skin color results from a combination of genetic, environmental, and physiological factors. All people have about the same number of melanocytes. Genetic differences in skin color result from differing amounts of melanin and in the size and distribution of melanin granules. Exposure to sunlight, UV light from sun lamps, and X-rays cause darkening of skin as melanin production increases. 14

Circulation within dermal blood vessels affects skin color. Skin Color, cont. Circulation within dermal blood vessels affects skin color. Well oxygenated blood gives a pinkish color Poorly oxygenated blood gives cyanosis. Yellowish skin color can come from eating too many foods with carotene or from cyanosis due to liver disease. 15

Dermis The dermis binds the epidermis to underlying tissues. Epidermal ridges and dermal papillae cause the border to be uneven. Genetically determined pattern of friction ridges formed by dermal papillae give unique fingerprints. The dermis consists of areolar and dense connective tissue with collagen and elastic fibers within a gel-like ground substance. 16

Dermis, cont. Dermal blood vessels carry nutrients to upper layers of skin and help to regulate temperature. The dermis also contains nerve fibers, sensory receptors, hair follicles, sebaceous glands, and sweat glands. 17

Fig 6.1a 18

6.3 Accessory Structures of the Skin 19

Nails are protective coverings over the ends of fingers and toes. Nails consist of a nail plate and stratified squamous epithelial cells overlying the nail bed, with the lunula as the most actively growing region of the nail root. As new cells are produced, older ones are pushed outward and become keratinized. 20

Fig 6.4 21

Hair 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. The dermis contain the hair root. As new cells are formed, old cells are pushed outward and become keratinized, and die forming the hair shaft. 22

Fig 6.5 23

Genetic lack of melanin causes albinism (white). Hair, continued Hair color is determined by genetics; melanin from melanocytes is responsible for most hair colors. Dark hair has eumelanin (brownish-black), while blonde and red hair have pheomelanin (reddish-yellow). Genetic lack of melanin causes albinism (white). A bundle of smooth muscle cells, called the arrector pili muscle, attaches to each hair follicle. These muscles cause goose bumps when cold or frightened. 24

Eccrine - which respond to body temperature Skin glands Sebaceous glands (holocrine glands) are associated with hair follicles and secrete sebum that waterproofs and moisturizes the hair shafts and skin. Sweat glands (sudoriferous glands) – merocrine; The secretions exit via a surface pore. Eccrine - which respond to body temperature Apocrine, which become active at puberty and respond to body temperature, stress, and sexual arousal. Most numerous in axilla and groin. 25

Mammary glands, another type of modified sweat gland, secretes milk. Skin glands, cont. Modified sweat glands, called ceruminous glands, secrete wax in the ear canal. Mammary glands, another type of modified sweat gland, secretes milk. 26

Fig 6.5 27

6.4 Regulation of Body Temperature 28

Heat may be lost to the surroundings from the skin through radiation. Proper temperature regulation is vital to maintaining metabolic reactions. The skin plays a major role in temperature regulation with the hypothalamus controlling it. 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. The body responds to excessive heat by dilation of dermal blood vessels and sweating. 29

Deviations from the normal temperature range can be dangerous. The body responds to excessive cooling by constricting dermal blood vessels, inactivating sweat glands, and shivering. Deviations from the normal temperature range can be dangerous. Hypothermia – core body temperature below 95°F. Hyperthermia – core body temperature over 106°F. 30

6.5 Healing of Wounds 31

Superficial cuts are filled in by reproducing epithelial cells. 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. Superficial cuts are filled in by reproducing epithelial cells. 32

The blood clot and dried tissue fluids form a scab. A deeper injury with broken blood vessels involves the formation of a blood clot. The blood clot and dried tissue fluids form a scab. Fibroblasts migrate into the area and secrete collagen fibers to bind the edges of the wound together. Phagocytotic cells remove debris and dead cells. Damaged tissue is replaced and the scab sloughs off. 33

A new branch of a blood vessel grows into the area. If the wound is deep, extensive production of collagenous fibers may form an elevation above the normal epidermal surface forming a scar. Large wounds leave scars and healing may be accompanied by the formation of granulations. A new branch of a blood vessel grows into the area. The vessel is accompanied by a cluster of fibroblasts that begin repair. 34

Fig 6.8 35