Explain why a membrane is an organ. Define integumentary organ system. Distinguish between serous and mucous membranes. List six functions of skin.

Distinguish between the epidermis and the dermis. Describe the subcutaneous layer.

Explain what happens to epidermal cells as they undergo keratinization.

List the layers of the epidermis.

Describe the function of melanocytes.

Describe the structure of the dermis.

Review the functions of dermal nervous tissue.

Explain the functions of the subcutaneous layer.

Distinguish between a hair and a hair follicle.

Review how hair color is determined.

Describe how nails are formed.

Explain the function of sebaceous glands.

17. Distinguish between eccrine and apocrine sweat glands.

18. Explain the importance of body temperature regulation.

19. Describe the role of the skin in promoting the loss of excess body heat.

20. Explain how body heat is lost by radiation.

21. Distinguish between conduction and convection.

22. Describe the body's responses to decreasing body temperature.

23. Review how air saturated with water vapor may interfere with body temperature regulation.

24. Explain how environmental factors affect skin color.

25. Describe three physiological factors that affect skin color.

26. Distinguish between the healing of shallow and deeper breaks in the skin.

27. Distinguish among first-, second-, and third-degree burns.

28. Describe possible treatments for a third-degree burn.

29. List three effects of aging on skin.

chapter objectives

After you have studied this chapter, you should be able to

1. Classify bones according to their shapes, and name an example from each group.

2. Describe the general structure of a bone, and list the functions of its parts.

3. Distinguish between intramembranous and endochondral bones, and explain how such bones grow and develop.

4. Describe the effects of sunlight, nutrition, hormonal secretions, and exercise on bone development.

5. Discuss the major functions of bones.

6. Distinguish between the axial and appendicular skeletons, and name the major parts of each.

7. Locate and identify the bones and the major features of the bones that comprise the skull, vertebral column, thoracic cage, pectoral girdle, upper limb, pelvic girdle, and lower limb.

8. Describe life-span changes in the skeletal system.

meat-, passage: auditory meatus—canal of the temporal bone that leads inward to parts of the ear. odont-, tooth: odontoid process—toothlike process of the second cervical vertebra. poie-, make, produce:

hematopoiesis—process by which blood cells are formed.

Understanding ^Vo rds ax-, axis: axial skeleton—upright portion of the skeleton that supports the head, neck, and trunk. -blast, bud, a growing organism in early stages: osteoblast— cell that will form bone tissue.

canal-, channel: canaliculus—

tubular passage. carp-, wrist: carpals—wrist bones.

-clast, break: osteoclast—cell that breaks down bone tissue.

clav-, bar: clavicle—bone that articulates with the sternum and scapula. condyl-, knob, knuckle:

condyle—rounded, bony process. corac-, a crow's beak: coracoid process—beaklike process of the scapula. cribr-, sieve: cribriform plate— portion of the ethmoid bone with many small openings. crist-, crest: crista galli—bony ridge that projects upward into the cranial cavity. fov-, pit: fovea capitis—pit in the head of a femur. gladi-, sword: gladiolus—middle portion of the bladelike sternum. glen-, joint socket: glenoid cavity—depression in the scapula that articulates with the head of a humerus. inter-, among, between:

intervertebral disk— structure located between adjacent vertebrae. intra-, inside: intramembranous bone—bone that forms within sheetlike masses of connective tissue. lamell-, thin plate: lamella—thin bony plate.

lifton Martin, a sixty-four-year-old New York City busl-

Cness owner, had to wear a surgical mask whenever he left his house, to hide the bright red tissue protruding from his nostrils. The tissue was from a tumor that had been growing behind his nose and mouth for two decades. Although the tumor was benign and hadn't spread, It had done enough damage where It was, weaving Into the man's sinuses and throughout the area behind his face.

Martin's plight began with nosebleeds that gradually worsened. Over the years, many surgeons had refused to operate, citing the tumor's proximity to the brain and the difficulty of reaching it without destroying the face. Two biopsies had led to extensive bleeding. In 1997, Martin found a surgeon who could remove such tumors. Dr. Ivo Janecka, of Harvard Medical School, had so thoroughly studied the bones of the face that he had compiled his own atlas to supplement existing texts. His specialty was the skull base, which is a thick basin of bone extending from the back of the head around the ears and nose. The skull base supports the brain and also has minute passageways for nerves and blood vessels leading to the face.

For years surgeons had skillfully skirted the skull base. Neurosurgeons operated above it, head and neck surgeons beneath it. In contrast, Dr. Janecka's approach, called "facial translocation," creates flaps of bone in and around the face. He carefully divides the face into sectors, then gently moves aside pieces of skin, fat, and bone to get to the tumor. It is a little like slowly taking apart an intricate puzzle, then reassembling the pieces.

Facial translocation takes from ten to twenty hours and requires a large team of surgeons with different specialties who take turns as their area of expertise is revealed. The procedure is possible, Dr. Janecka says, because of this cooperation, coupled with more complete information on facial anatomy and the location of tumors derived from MRI and CT scans. The surgeons map out the path to a particular patient's tumor ahead of time, then practice on cadavers.

Clifton Martin's surgery took ten hours. Dr. Janecka peeled back the left side of the face, including the lip area, cheek, nose, and eyelid, to reveal the tumor—the size of a small apple, behind the mouth and nose, snaking into the sinuses and touching the skull base. After removing the tumor, Dr. Janecka reassembled Martin's facial bones, using small plates and screws made of the biocompatible metal titanium.

Nonliving material in the matrix of bone tissue makes the whole organ appear to be inert. A bone also contains very active, living tissues. An individual bone is composed of a variety of tissues: bone tissue, cartilage, dense connective tissue, blood, and nervous tissue.

Bone Structure

The bones of the skeletal system differ greatly in size and shape, but they are similar in their structure, development, and functions.

Bone Classification

Bones are classified according to their shapes—long, short, flat, or irregular (fig. 7.1).

Long bones have long longitudinal axes and expanded ends. Examples are the forearm and thigh bones.

Short bones are somewhat cubelike, with their lengths and widths roughly equal. The bones of the wrists and ankles are examples of this type.

Flat bones are platelike structures with broad surfaces, such as the ribs, scapulae, and some bones of the skull.

Irregular bones have a variety of shapes and are usually connected to several other bones. Irregular bones include the vertebrae that comprise the backbone and many facial bones.

In addition to these four groups of bones, some authorities recognize a fifth group called sesamoid bones, or round bones (see fig. 7.47b). These bones are usually small and nodular and are embedded within tendons adjacent to joints, where the tendons are com-

pressed. The kneecap (patella) is an example of a sesamoid bone.

Parts of a Long Bone

The femur, a long bone in the thigh, illustrates the structure of bone (fig. 7.2). At each end of such a bone is an expanded portion called an epiphysis (e-pif 'i-sis) (pl., epiphyses), which articulates (or forms a joint) with another bone. On its outer surface, the articulating portion of the epiphysis is coated with a layer of hyaline cartilage called articular cartilage (ar-tik'u-lar kar'ti-lij). The shaft of the bone, which is located between the epiphy-ses, is called the diaphysis (di-af'i-sis).

Except for the articular cartilage on its ends, the bone is completely enclosed by a tough, vascular covering of fibrous tissue called the periosteum (per"e-os'te-um). This membrane is firmly attached to the bone, and the periosteal fibers are continuous with ligaments and tendons that are connected to the membrane. The periosteum also functions in the formation and repair of bone tissue.

A bone's shape makes possible its functions. Bony projections called processes, for example, provide sites for attachment of ligaments and tendons; grooves and openings are passageways for blood vessels and nerves; a depression of one bone might articulate with a process of another.

The wall of the diaphysis is mainly composed of tightly packed tissue called compact bone (kom'pakt bon) (cortical bone). This type of bone has a continuous matrix with no gaps (fig. 7.3a).

The epiphyses, on the other hand, are largely composed of spongy bone (spun'je bon) (cancellous

Epiphyseal plates


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