Chapter 6

What major effects of parathyroid hormone oppose those of calcitonin?

Parathyroid hormone stimulates osteocast activity, increases the rate of intestinal absorption of calcium ions and decreases the rate of exreation of calcium ions

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 systems (kidneys) 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 change in the dietary supplies of these ions.

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

The lack of stress during inactivity leads to the removal of calcium salts from bones. Up to 1/3 of the bone mass can be lost in this manner, causing bones to become thin and brittle.

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.

what nutritional factors are essential for normal bone growth and maintenance

calcium salts, phosphate salts, vitamin A,C,D3

List the organic components of the bone matrix

collagen

two-thirds of the weight of bone is accounted for by

crystals of calcium phosphate

List the inorganic components of the bone matrix

hydroxypatite crystals

What are the 5 primary functions of the skeletal system

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

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

C and D

what is the primary difference between endochondral ossification and intermembranous ossification?

IO bone develops from mesenchyme or fibrous connective tissue. EO bone develops from a cartilage model

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 into the surface of the tabeculae

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 tends to be stronger and thicker than normal at the fracture site.

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

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

What hormonal factors are necessary for normal bone growth and maintenance

calcitriol, growth hormone, thyroxine, estrogens (in females) or androgens (in males), calcitonin, and parathyroid hormone (PTH)

Which 3 organs or tissues interact to assist in the regulation of calcium ion concentration in body fluids?

bones, intestinal tract and kidneys

The hormones that coordinate the storage, absorption, and excretion of calcium ions are

calcitonin and parathyroid hormone

what are the primary parts of a typical long bone

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

The process of bone growth at the epiphysiseal cartilage is similar to

endochondral ossification

The presence of an epiphyseal line indicates

epiphyseal growth has ended

List 4 distinctive cell populations of osseous tissue

osteocytes, osteoblasts, osteoclasts, osteoprogenitor cells

the nonpathologic loss of bone that occurs with aging is called

osteomalacia

The basic functional unit of compact bone is the Haversian system or

osteon

The membrane found wrapping the bones, except at the joint cavity, is the

periosteum

Blood cell formation occurs in

red bone marrow

the primary reason that osteoporosis accelerates after menopause in women is

reduced levels of circulating estrogens