Chapter 7- Skeletal System Test

Name six types of synovial joints. (examples for each)

Ball-and-socket joint: shoulder and hip Condyloid joint: between metacarpals and phalanges Gliding joints: joints formed by ribs Hinge Joint: elbow and phalanges Pivot Joint: proximal ends of radius and ulna Saddle Joint: carpal (trapezium) and the metacarpal of the thumb

Name three major bones.

Bones shape, support, and protect body structures. They also aid body movements, house tissue that produce blood cells, and store various inorganic salts.

What terms describe movements possible at synovial joints? (8 terms and description of the general movement of each).

Flexion- bending parts a joint so that the angle between them decreases and the parts come closer together Extension- straightening parts at a joint so that the angle between them increases and the parts move farther apart Dorsiflexion- Bending the foot at the ankle toward the shin (bending foot forward) Plantar Flexion- bending the foot at the ankle toward the sole (being the foot downward) Hyperextension- excess extension of the parts at a joint, beyond the anatomical position (bending the head back beyond the upright position) Abduction- Moving a part away from the midline Adduction- Moving a part toward the midline Rotation- Moving a part around an axis (twisting head from side to side)

Describe the microscopic structure of compact bone.

In compact bone, the osteocytes and layers of intercellular material concentrically clustered around an osteonic canal form a cylinder-shaped unit called on osteon. Many of these unite cemented together form for the substance of compact bone.

Explain how an endochondral bone develops.

Most of the bones of the skeleton are endochondral bones. They develop from masses of hyaline cartilage shaped like future bony structures. These cartilaginous models grow rapidly for a time, and then being to extensively change. At about the same tie, a periosteum forms from connective tissue that encircles the developing diaphysis. Blood vessels and osteoblasts from the periosteum invade the disintegrating cartilage, and spongy bone forms in its place.

Distinguish between the functions of red marrow and yellow marrow.

Red marrow functions in the formation of red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). Red marrow occupies the cavities of most bones in an infant. With increasing age, however, yellow marrow replaces much of it. Yellow marrow stores fat and is inactive in blood cell production.

Describe the characteristics of the three major types of joints.

The FIBROUS JOINTS lie between bones that closely contact one another. A thin layer of dense connective tissue joins the bones at such joints, as in the case of a suture between a pair of flat bones of the skull. No appreciable movement takes place at a fibrous joints. Disks of fibrocartilage or hyaline cartilage connect the bones of CARTILAGINOUS JOINTS. The disk absorbs shocks and helps equalize pressure between adjacent vertebrae when the body moves. Due to slight flexibility of the disks, cartilaginous joints allow limited movement. Most joints within the skeletal system are SYNOVIAL JOINTS and allow free movement. They are more complex structurally than fibrous or cartilaginous joints.

List the bones of the appendicular skeleton.

The appendicular skeleton consists of: the pectoral girdle—scapula and clavicle; the upper limbs—humerus, radius, ulna, carpals, metacarpals, and phalanges; the pelvic girdle—coxal bones; and the lower limbs—the fibula, patella, tarsals, metatarsals, and phalanges.

Distinguish between the axial and appendicular skeletons.

The axial skeleton consists of the bony and cartilaginous part that supports the organs of the head, neck, and trunk. The appendicular skeleton consists of the bones of the upper and lower limbs and the bones that anchor the limbs to the axial skeleton.

List the bones of the axial skeleton.

The axial skeleton includes: the skull—cranium and the facial bones; the hyoid bone; vertebral column—intervertebral disks, sacrum, coccyx; and the thoracic cage—ribs and sternum.

Describe the development of an intramembranous bone.

The broad, flat bones of the skull are intramembranous bones. During their development, membrane-like layers of connective tissues appear at the sites of the future bones. Then, some of the primitive connective tissue cells enlarge and differentiate into bone-forming cells called osteoblasts. The osteoblasts become active within the membranes and deposit bony matrix around themselves. As a result, spongy bone tissue forms in all directions within the layers of primitive connective tissues. Eventually, cells of the membranous tissue that persist outside the developing bone give rise to the periosteum.

List the substances normally stored in bone tissue.

The intracellular matrix of bone tissue is rich in calcium solts, mostly in the form of calcium phosphate. Bone tissue contains lesser amounts of magnesium, sodium, potassium, and carbonate ions. Bones also accumulate certain harmful metallic elements such as lead, radium, or strontium which are not normally present in the body but are sometimes ingested accidentally.

List five major parts of a long bone.

The major parts of a long bone include epiphysis, articular cartilage, diaphysis, periosteum, medullary cavity, endosteum, and marrow.

Explain how osteoclasts and osteoblasts remodel bone.

The osteoblasts become active within the membranes and deposit bony matrix around themselves. As a result, spongy bone tissue forms in all directions within the layers of primitive connective tissues. In time, large, multinucleated cells called osteoclasts break down the calcified matrix. Osteoclasts secrete an acid that dissolves the inorganic component of the calcified matrix, bone-building osteoblasts invade the region and deposit bone tissue in place of the calcified cartilage.

How do compact and spongy bone differ in structure?

The wall of the diaphysis is mainly composed of tightly packed tissue called compact bone. This type of bone has a continuous matrix with no gaps. The epiphyses, in contrast, are composed largely of spongy bone with thin layers of compact bone on their surfaces. Spongy bone consists of numerous branching bony plates.