Anatomy: Chapter 6 Check Point Quiz

In endochondral ossification, what is the original source of osteoblasts?

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

Compare the structures and functions of compact bone and spongy bone

compact bone consists of osteons (Haversian systems) with little space between 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.

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

- osteocytes - osteoblasts -osteoclasts

At which point in fracture repair would you find an external callus?

they form early in the healing process, when cells from the endosteum and periosteum migrate to the area of the fracture

List the steps involved in fracture repair, beginning at the onset of the bone break

- extensive bleeding occurs at the site of the injury - a large blood clot called a fracture hematoma develops - an internal callus forms as a network of spongy bone unites the inner edges, and an external callus of cartilage and bone stabilizes the outer edges - cartilaginous external callus is eventually replaced by bone, and the struts of spongy bone now unite the broken ends. - swelling that initially marks the location of the fracture is remodeled - little evidence that a break occurred

Name the 5 primary functions of the skeletal system

- support -storage of minerals and lipids - blood cell reproduction -protection -leverage

Identify the 6 broad categories for classifying a bone according to shape

-flat bones -irregular bones -long bones -sesamoid bones -short bones -sutural bones

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 at the kidneys.

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

Parathyroid hormone (PTH) stimulates osteoclasts to release calcium ions from bone. Increased PTH secretion would result in an increase in the level of calcium ions in the blood.

Define bone marking (surface feature)

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

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 reduced mineral content (less mass); as a result, it would also be weaker

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

estrogens play an important role in moving calcium into bones. After menopause, the level of these hormones decrease dramatically - older women have difficulty replacing the calcium in bones that is being lost due to normal aging. In men, the level of sex hormones do not increase until much later in life.

During intramembranous ossification, which type(s) of tissue is (are) replaced by bone?

fibrous connective tissue is replaced by bone

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 occurs 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 individual will be when growth is completed.

Define osteopenia

inadequate ossification and is common to the aging process - decrease of osteoblast activity with normal osteoclast activity

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 individual 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 not the bone has reached its adult length.

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

parathyroid hormone (PTH) influences osteoclast activity to cause a release of stored calcium ions from bone. Under the influence of calcitonin, osteoclast activity is inhibited, while osteoblasts continue to lock calcium ions in the bone matrix. Therefore, 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.

Explain how heavy-metal ions could be incorporated into bone matrix

the biochemistry of some heavy-metal ions, such as strontium, cobalt, uranium, and plutonium, is very similar to that of calcium. Osteoblasts cannot differentiate these abnormal heavy-metal ions from normal calcium ions, so the heavy-metal ions become incorporated into the bone matrix. Over time, these dangerous ions can be released into circulation during normal bone remodeling.

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

the bone would become less strong (and more flexible)

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.

Why would you expect the arm bones of a weight lifter 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.

Describe bone remodeling

the process whereby old bone is continuously being destroyed by osteoclasts while new bone is being constructed by osteoblasts