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Anat & Phys Ch. 6
Transcript of Anat & Phys Ch. 6
Skin and the Integumentary System A. 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. Healing of Wounds and Burns A. Serous membranes line body cavities that lack openings to the outside. Types of Membranes A. The skin is a large organ responsible for maintaining
homeostasis through temperature regulation, protection of
underlying tissues, retardation of water loss, housing sensory
receptors, synthesizing certain chemicals, and excreting wastes. Skin and Its Tissues A. Nails Accessory Organs of the Skin C. Sebaceous Glands A. Proper temperature regulation is vital to maintaining metabolic reactions. Regulation of Body Temperature
A. Organs are body structures composed of two or more different tissues. Introduction: B. The skin and its accessory organs make up the integumentary system. 1. They line the thorax and abdomen and cover the organs within these cavities. 2. Serous membranes are made up of epithelium and loose connective tissue and secrete serous fluid that acts as a lubricant. CopyrightThe McGraw-Hill Companies, Inc. Permission required for reproduction or display. B. Mucous membranes line the cavities and openings that lead to the outside of the body, including the oral and nasal cavities, and openings of the digestive, reproductive, respiratory, and urinary systems. 1. They consist of epithelium and connective tissue with specialized cells that secrete mucus.
D. The cutaneous membrane consists of the skin, and is the subject of the remainder of this chapter. C. Synovial membranes line the joint cavities. 1. These membranes consist of only connective tissues and they secrete lubricating synovial fluid. C. Deeper cuts are closed off by clots, covered by scabs, and eventually filled in by fibroblasts, making connective tissue. Blood vessels extend into the area, injured tissues are replaced, and the scab falls off.
B. Superficial cuts are filled in by reproducing epithelial cells. D. Heat may be lost to the surroundings from the skin through radiation.
B. The skin plays a major role in temperature regulation with the hypothalamus controlling it.
1. Sweat glands (sudoriferous glands) are either eccrine, which respond to body temperature, or apocrine, which respond to body temperature, stress, and sexual arousal.
1. Sebaceous glands (holocrine glands) are associated with hair follicles and secrete sebum that waterproofs and moisturizes the hair shafts. 5. Hair color is determined by genetics; melanin from melanocytes is responsible for most hair colors. Dark hair has eumelanin while blonde and red hair have pheomelanin. B. Hair Follicles 1. The epidermis is made up of stratified squamous epithelium and lacks blood vessels. B. The skin consists of an outer epidermis and
a dermis, connected to underlying tissue by the
subcutaneous layer (hypodermis). 2. The layer of reproducing cells (the stratum basale), which lies at the base of the epidermis, is well-nourished by dermal blood vessels. C. Epidermis 3. 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.
6. Melanocytes pass melanin to nearby cells through cytocrine secretion. 4. The epidermis is important because it protects against water loss, mechanical injury, chemicals, and microorganisms. 5. 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. 4. Circulation within dermal blood vessels affects skin color. D. Skin Color 1. Skin color results from a combination of genetic, environmental, and physiological factors. 2. Genetic differences in skin color result from differing amounts of melanin and in the size of melanin granules. 3. Exposure to sunlight causes darkening of skin as melanin production increases. 2. The dermis consists of connective tissue with collagen and elastic fibers within a gel-like ground substance. E. Dermis 1. The dermis binds the epidermis to underlying tissues. Epidermal ridges and dermal papillae cause the border to be uneven. 3. Dermal blood vessels carry nutrients to upper layers of skin and help to regulate temperature. 4. The dermis also contains nerve fibers, sensory fibers, hair follicles, sebaceous glands, and sweat glands. F. Subcutaneous Layer 3. No sharp boundary exists between the dermis and subcutaneous layer. 2. It binds the skin to underlying organs and contains the blood vessels that supply the skin. 1. The subcutaneous layer (hypodermis) is composed of loose connective tissue and insulating adipose tissue. 3. As new cells are produced, older ones are pushed outward and become keratinized. 2. Nails consist of stratified squamous epithelial cells overlying the nail bed, with the lunula as the most actively growing region of the nail root. 1. Nails are protective coverings over the ends of fingers and toes. 3. As new cells are formed, old cells are pushed outward and become keratinized, and die forming the hair shaft. 2. Individual hairs develop from cells at the base of the hair follicle, an invagination of the lower epidermis that dips down into the dermis. 1. Hair can be found in nearly all regions of the skin. 4. 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. D. Sweat Glands 3. Mammary glands, another modified type of sweat glands, secrete milk. 2. Modified sweat glands, called ceruminous glands, secrete wax in the ear canal. C. Active cells, such as those of the heart and skeletal muscle, produce heat. F. The body responds to excessive cooling by constricting dermal blood vessels, inactivating sweat glands, and shivering. E. The body responds to excessive heat by dilation of dermal blood vessels and sweating. D. Large wounds leave scars and healing may be accompanied by the formation of granulations.