Bones and Skeletal Tissues

Chapter 6

Bones and Skeletal Tissues

I. Cartilages (pp. 125–126, Fig. 6.1)

A.Cartilages are resilient, avascular tissues that lack innervation.

B.Cartilages are located in the human body in the following sites:

1.External ear and nose

2.The epiglottis, larynx, larger respiratory tubes (trachea and bronchi), articular cartilages, costal cartilages, and embryonic

3.Intervertebral discs, pubic symphysis, and menisci

C.The three types of cartilage are elastic, hyaline (most abundant), and fibrocartilage.

D.Cartilages grow in two ways: appositional growth and interstitial growth.

E.Cartilage stops growing in the late teens and regenerates poorly after that time.

F.Calcified cartilage is a sign of aging; however, it remains a distinct tissue and is not bone.

II. Bones (pp. 126–140, Figs. 6.2–6.14)

A.Bones of the skeleton are considered organs because they contain different types of tissues.

B.Functions of bones include the following:

1.Support (give the body shape)

2.Movement (serve as levers for muscles to pull on)

3.Protection (protect soft organs)

4.Mineral storage (store calcium and phosphate)

5.Blood-cell formation (contain bone marrow, hematopoietic tissue, that makes blood cells)

C.Classification of bones is based on shape: long, short, flat, or irregular. (pp. 128–129, Fig. 6.2)

1.Long bones are longer than wide with a definite diaphysis and two epiphyses; all limb bones except patellas, carpals, and tarsals are long bones.

2.Short bones are somewhat cube-shaped and include the carpals and tarsals. Sesamoid bones, including the patellas, are a special type of short bone that forms within tendons.

3.Flat bones are thin, flattened, often curved bones that include most skull bones, the sternum, scapulae, and ribs.

4.Irregular bones do not fit any of the other categories and have complicated shapes. Vertebrae and coxae are irregular bones.

D.Gross anatomy of bones (pp. 129–131, Figs. 6.3–6.5, Table 6.1)

1.Compact bone is the dense outer layer of bone; internal to this is spongy bone.

2.Structures of typical long bones:

a.Diaphysis forms the “shaft” of a long bone; epiphyses form the proximal and distal ends of a long bone.

b.Blood vessels feed bone tissue through the nutrient foramen.

c.The medullary cavity is located along the center of a long bone and contains yellow bone marrow.

d.Periosteum is a connective tissue covering the external surface of the diaphysis of a long bone; endosteum covers the internal surface of a long bone.

3.Structures of short, irregular, and flat bones are similar to those of long bones, though they have no diaphysis. They contain marrow, but have no marrow cavity.

4.Bone design reflects the stresses placed upon it.

a.Strong, compact bone tissue occurs in the external portion of bone.

b.Lack of bone tissue at a bone’s center does not impair its strength.

c.Spongy bone is exquisitely organized along stress lines.

d.Superficial surfaces of bones have distinct bony markings.

5.Bony markings provide significant information about the function of bone and muscle.

a.Many bony markings are sites for muscle attachment. (Chapter 11)

b.Other bony markings form joints.

c.Openings within bones (e.g., foramina) are the passageways for blood vessels and nerves.

E.Compact bone and spongy bone differ microscopically. (pp. 131–135, Figs. 6.6–6.8)

1.The osteon is the important structural unit of compact bone. Osteons are structures unique to compact bone and include lamellae, the central canal, lacunae containing osteocytes, and canaliculi.

2.Spongy bone is formed from osteocytes and lamellae organized in trabeculae. However, spongy bone lacks the structural complexity of compact bone.

F.Bone tissue has both organic and inorganic components.

1.Organic components of bone tissue are cells, fibers, and ground substance.

2.The inorganic components of bone tissue are mineral salts, primarily calcium phosphate.

G.The process of bone-tissue formation is named osteogenesis or ossification. (pp. 135–137, Figs. 6.9–6.10)

1.Intramembranous ossification forms membrane bone from fibrous connective tissue membranes, and results in the cranial bones and clavicles.

2.Endochondral ossification bone tissue replaces hyaline cartilage; all bones, except the skull bones and clavicles, form this way.

H.Anatomical examination of epiphyseal growth areas reveals growing cartilage organized in several zones; this organization permits the rapid growth of bone. (p. 137, Fig. 6.10)

I.Endochondral bones lengthen during youth and widen through appositional growth.

J.Bone remodeling is accomplished by deposition and resorption of new bone tissue in response to hormonal and mechanical stimuli and occurs throughout life.

K.Repair of bone fractures is accomplished by open or closed reduction. (p. 140, Fig. 6.14)

III. Disorders of Bones (pp. 140–143, Fig. 6.15)

A.Examples of diseases of bone are osteoporosis, osteomalacia, rickets, Paget’s disease, and osteosarcoma.

IV. The Skeleton Throughout Life (p. 143, Fig. 6.16)

A.Beginning with bone formation in the fetus, ossification occurs in a predictable manner and in consistent stages until death of the skeleton.

Supplemental Student Materials to Human Anatomy, Fifth Edition

Chapter 6: Bones and Skeletal Tissues

To the Student

During your study of Chapter 6, you will find out about the amazing structure and functions of bone tissue and cartilage. Together they form your skeleton. You will gain insight as to how an individual bone functions as an organ in its own right. The important relationship of cartilage to bone during development is explained. Understanding the basics in this chapter prepares you for succeeding chapters, where you will learn the bones forming the axial and appendicular skeletons, how joints form, attachments of muscles to bones, and movements.

Step 1: Understanding cartilage.

-Define cartilage.

-Identify major locations of cartilage in the adult human body.

-Explain the functional properties of cartilage as a tissue.

-List three major kinds of cartilage tissue.

-Prepare a comparison chart of the kinds of cartilage, including notes on structure, functions, and locations.

-Describe how cartilage grows.

-Define perichondrium.

Step 2: Understanding bone tissue.

-Describe why a bone may be considered an organ.

-Summarize several main functions of the bony skeleton.

-Describe the gross anatomy of a typical long bone.

-Describe the gross anatomy of a flat bone.

-Explain how bones withstand tension and compression.

-Analyze different bony markings based upon their locations and functions.

-Draw and label an osteon. Describe histological features.

-Describe differences between compact bone tissue and spongy bone tissue.

-Describe the chemical composition of bone and distinguish between its organic and inorganic components.

-Distinguish between intramembranous and endochondral ossification as types of bone formation.

-Explain how bone is remodeled in the skeleton.

-Name some common types of fractures.

-Explain basic steps in the repair of a fracture.

Step 3: Explore bone disorders and changes of bone tissue throughout life.

-List symptoms of osteoporosis.

-Name two ways aged bone differs from young bone.