Fundamentals of Anatomy & Physiology, Chapter 6: Osseous Tissue and Bone Structure

Define bone marking.

A bone marking (surface feature) is an area on the surface of a bone structured for a specific function, such as joint formation, muscle attachment, or the passage of nerves and blood vessels.

How does calcitonin help lower the calcium ion concentration of blood?

Calcitonin lowers blood calcium levels by inhibiting osteoclast activity and increasing the rate of calcium excretion by the kidneys.

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.

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 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

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

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 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

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

(a) What nutritional factors are essential for normal bone growth and maintenance? (b) What hormonal factors are necessary for normal bone growth and maintenance?

(a) calcium salts, phosphate salts, and vitamins A, C, and D3; (b) calcitriol, growth hormone, thyroxine, estrogens (in females) or androgens (in males), calcitonin, and parathyroid hormone (PTH)

List the four distinctive cell populations of osseous tissue.

1) osteocytes; (2) osteoblasts; (3) osteoclasts; and (4) osteogenic cells

If the activity of osteoclasts exceeds the activity of osteoblasts in a bone, how will the mass of the bone be affected?

Because osteoclasts break down or demineralize bone, the bone would have a decreased mineral content (less mass); as a result, it would also be weaker.

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

Compare the structures and functions of compact bone and spongy bone.

Compact bone consists of osteons (Haversian systems) with little space be- tween them. Compact bone lies over spongy bone and makes up most of the diaphysis. It functions to protect, support, and resist stress. Spongy bone consists of trabeculae with numerous red marrow-filled spaces. Spongy bone makes up most of the structure of short, flat, and irregular bones and is also found at the epiphyses of long bones. Spongy bone functions in storing marrow and providing some support.

During intramembranous ossification,which type of tissue is replaced by bone?

During intramembranous ossification, fibrous connective tissue is replaced by bone.

Frank does not begin 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 started puberty earlier.

A child who enters puberty several years later than the average age is generally taller than average as an adult. Why?

Growth continues throughout childhood. At puberty,a growth spurt takes place and is followed by the closure of the epiphyseal cartilages. The later puberty begins, the taller the child will be when the growth spurt begins, so the taller the person will be when growth is completed.

How would the compressive strength of a bone be affected if the ratio of collagen to hydroxyapatite increased?

If the ratio of collagen to hydroxyapatite in a bone increased, the bone would become less strong (as well as more flexible).

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 endochondral ossification,what is the original source of osteoblasts?

In endochondral ossification, cells of the inner layer of the perichondrium differentiate into osteoblasts, and a cartilage model is gradually replaced by bone.

Why is osteoporosis more common in older women than in older men?

In women, the sex hormones known as estrogens play an important role in moving calcium into bones. After menopause, the level of these hormones decreases dramatically. As a result, older women have difficulty replacing the calcium in bones that is being lost due to normal aging. In men, the level of sex hormones (andro- gens) does not decrease until much later in life.

A 7-year-old child has a pituitary gland tumor involving the cells that secrete growth hormone (GH), resulting in increased levels of GH. How will this condition affect the child's growth?

Increased levels of growth hormone prior to puberty will result in excessive bone growth, making the person taller.

How could x-rays of the femur be used to determine whether a person has reached full height?

Long bones of the body, such as the femur, have an epiphyseal cartilage, a plate of cartilage that separates the epiphysis from the diaphysis so long as the bone is still growing lengthwise. An x-ray would indicate whether the epiphyseal cartilage is still present. If it is, growth is still occurring. If it is not, the bone has reached its adult length and thus, the person has reached full height.

Mature bone cells are known as _____, bone-building cells are called _____, and _____ are bone-resorbing cells.

Mature bone cells are known as osteo- cytes, bone-building cells are called osteoblasts, and osteoclasts are bone-resorbing cells.

Define osteopenia.

Osteopenia is inadequate ossification and is common during the aging process. It results from decreasing osteoblast activity accompanied by normal osteoclast activity.

What effect would increased PTH secretion have on blood calcium levels?

Parathyroid hormone (PTH) indirectly stimulates osteoclasts to release calcium ions from bone and enhances calcitriol's effect on the intestinal absorption of calcium. Increased PTH secretion would result in an increase in the level of calcium ions in the blood.

Identify the hormones involved in stimulating and inhibiting the release of calcium ions from bone matrix.

Parathyroid hormone (PTH) influences osteoclast activity, which causes a release of stored calcium ions from bone. Under the influence of calcitonin, osteoclast activ- ity is inhibited, while osteoblasts continue to lock calcium ions in the bone matrix. In this way, PTH serves to increase blood calcium levels by causing its release from bone, and calcitonin decreases blood calcium levels by causing calcium to remain in bone.

What major effects of parathyroid hormone oppose those of calcitonin?

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.

Why does a child who has rickets have difficulty walking?

The bones of children who have rickets are poorly mineralized and as a result are quite flexible. Under the weight of the body, the leg bones bend. The instability makes walking difficult and can lead to other problems of the legs and feet.

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 compen- sate for changes in the dietary supplies of these ions.

Name the five primary functions of the skeletal system.

The five primary functions of the skeletal system are support, storage of minerals and lipids, blood cell production, protection, and leverage.

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

The lack of physical stress during inactivity leads to the removal of cal- cium 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.

Why would you expect the arm bones of a weigh tlifter to be thicker and heavier than those of a jogger?

The larger arm muscles of the weight lifter would apply more mechanical stress to the bones of the upper limbs. In response to that stress, the bones would grow thicker.

A sample of bone has lamellae, which are not arranged in osteons. Is the sample most likely taken from the epiphysis or diaphysis?

The presence of lamellae that are not arranged in osteons is indicative of spongy bone, which is located in an epiphysis.

Identify the six broad categories for classifying a bone according to shape.

The six broad categories for classifying bones according to shape are sutural bones, ir- regular bones, short bones, flat bones, long bones, and sesamoid bones.

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 intestinal tract, and the kidneys

Why would a physician 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 car- tilage (plate). Measuring the width of these plates will provide clues to the hormonal control of growth in the child.

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