CH. 6

What are the primary parts of a typical long bone?

- diaphysis (shaft) - epiphysis - epiphyseal cartilage/ line - articular cartilage, medullary canal - periosteum - endosteum

List the four distinctive cell populations of bone tissue

1. osteogenic cells 2. osteoblasts 3. osteocytes 4. osteoclasts

Frank does not enter puberty until he is 16. What effect would you predict this will have on his stature? (a) Frank will probably be taller than if he had started puberty earlier. (b) Frank will probably be shorter than if he had started puberty earlier. (c) Frank will probably be a dwarf. (d) Frank will have bones that are heavier than normal. (e) The late onset of puberty will have no effect on Frank's stature.

Frank will probably be taller than if he had started puberty earlier.

What is the primary difference between endochondral ossification and intramembranous ossification?

In endochondral ossification, bone replaces a cartilage model. In intramembranous ossification, bone replaces mesenchyme or fibrous connective tissue.

In physical anthropology, cultural conclusions can be inferred from a thorough examination of the skeletons of ancient peoples. What sorts of clues might bones provide as to the lifestyles of those individuals?

The matrix of bone will absorb traces of minerals from the diet. These minerals can be identified hundreds of years later. A diet rich in calcium and vitamin B will produce denser bones than will a diet deficient in them. Cultural practices such as the binding of appendages or the wrapping of infant heads will manifest in misshapen bones. Heavy muscular activity will result in larger bone markings, indicating an athletic or physically demanding lifestyle.

Why are stresses or impacts to the side of the shaft in a long bone more dangerous than stress applied to the long axis of the shaft?

The osteons are aligned parallel to the long axis of the shaft, which does not bend when forces are applied to either end. Stresses or impacts to the side of the shaft can lead to a fracture.

How might bone markings be useful in identifying the remains of an individual who was shot and killed years ago?

Bone markings give clues as to the size, age, sex, and general appearance of an individual.

The vitamins essential for normal adult bone maintenance and repair are: (a) A and E (b) C and D3 (c) B and E (d) B complex and K.

C and D3

What are the functional relationships between the skeleton, on the one hand, and the digestive and urinary systems, on the other?

The digestive and urinary (kidneys) systems play important roles in providing the calcium and phosphate minerals needed for bone growth. In return, the skeleton provides protection and acts as a reserve of calcium, phosphate, and other minerals that can compensate for changes in the dietary supplies of these ions.

While playing on her swing set, 10-year-old Sally falls and breaks her right leg. At the emergency room, the doctor tells her parents that the proximal end of the tibia where the epiphysis meets the diaphysis is fractured. The fracture is properly set and eventually heals. During a routine physical when she is 18, Sally learns that her right leg is 2 cm shorter than her left, probably because of her accident. What might account for this difference?

The fracture might have damaged the epiphyseal cartilage in Sally's right leg. Even though the bone healed properly, the damaged leg did not produce as much cartilage as did the undamaged leg. The result would be a shorter bone on the side of the injury.

Why do extended periods of inactivity cause degenerative changes in the skeleton?

The lack of physical stress during inactivity leads to the removal of calcium salts from bones. Up to one-third of the bone mass can be lost in this manner, causing the bones to become thin and brittle.

The hormones that coordinate the storage, absorption, and excretion of calcium ions are: (a) growth hormone and thyroxine (b) calcitonin and parathyroid hormone (c) calcitriol and cholecalciferol (d) estrogens and androgens

calcitonin and parathyroid hormone

What hormonal factors are necessary for normal bone growth and maintenance?

Calcitriol, growth hormone, thyroxine, estrogen (in females) or testosterone (in males), parathyroid hormone, and calcitonin.

What nutritional factors are essential for normal bone growth and maintenance?

Calcium salts, phosphate salts, and vitamins A, C, and D3.

Two-thirds of the weight of bone is accounted for by : (a) crystals of calcium phosphate (b) collagen fibers (c) osteocytes (d) calcium carbonate.

crystals of calcium phosphate

The process of bone growth at the epiphyseal cartilage is similar to: (a) intramembranous ossification (b) endochondral ossification (c) the process of osteopenia (d) the process of healing a fracture (e) the process of calcification

endochondral ossification

The presence of an epiphyseal line indicates: (a) epiphyseal growth has ended (b) epiphyseal growth is just beginning (c) growth of bone diameter is just beginning (d) the bone is fractured at the location (e) no particular event.

epiphyseal growth has ended

List the organic and inorganic components of bone matrix

organic = collagen inorganic = hydroxyapatite crystals

The basic functional unit of compact bone is the Haversian system or: (a) osteocyte (b) osteoclast (c) osteon (d) osseous matrix (e) osseous lamellae

osteon

The nonpathologic loss of bone that occurs with aging is called: (a) osteomyelitis (b) osteoporosis (c) osteopenia (d) osteitis (e) osteomalacia.

osteopenia

The membrane found wrapping the bones, except within the joint cavity, is the: (a) periosteum (b) endosteum (c) perforating fibers (d) a, b, and c are correct.

periosteum

Blood cell formation occurs in: (a) yellow bone marrow, (b) red bone marrow (c) the matrix of bone tissue (d) the ground substance of bones.

red bone marrow

If spongy bone has no osteons, how do nutrients reach the osteocytes?

Nutrients reach the osteocytes in spongy bone by diffusing along canaliculi that open onto the surface of the trabeculae.

Why does a second fracture in the same bone tend to occur at a site different from that of the first fracture?

Once a bone fracture has been repaired, the bone at the fracture site tends to be stronger and thicker than normal.

What are the major effects of parathyroid hormone?

Parathyroid hormone stimulates osteoclast activity, increases the rate of intestinal absorption of calcium ions, and decreases the rate of excretion of calcium ions by the kidneys. These effects increase blood calcium levels.

Which three organs or tissues interact to assist in the regulation of calcium ion concentration in body fluids?

The three organs or tissues are the bones, the intestines of the digestive tract, and the kidneys.

Why would a physician be concerned about the growth patterns of a young child request an x-ray of the hand?

There are many long bones in the hand, each of which has an epiphyseal cartilage (plate). Measuring the width of these plates will provide clues to the hormonal control of growth in the child.

Which of the following conditions would you possibly observe in a child who is suffering from rickets? (a) abnormally short limbs (b) abnormally long limbs (c) oversized facial bones (d) bowed legs (e) weak, brittle bones

bowed legs

The primary reason that osteoporosis accelerates after menopause in women is: (a) reduced levels of circulating estrogens (b) reduced levels of vitamin C (c) diminished osteoclast activity (d) increased osteoblast activity.

reduced levels of circulating estrogens

Name the major functions of the skeletal system

support, storage of minerals & lipids, blood cell production, protection, and leverage