BIO40A Activity 8

The trabeculae of spongy bone rearrange themselves as an infant learns to walk so as to be oriented along the lines of stress he bones are subject to. True or False?

True

By which process, as an individual grows to adulthood, is the thickness (diameter) of bone increased?

Appositional growth

During the process of bone formation in a fetus, a primary ossification center develops in the epiphysis of a cartilage model of a long bone. True or False?

False

In primary ossification, the first type of bone that forms and replaces the cartilage model is compact bone. True or False?

False

In the activities of secondary ossification centers, the medullary cavity forms later and is much smaller. True or False?

False

Osteocytes within lacunae are only found in compact bone and not within the trabeculae of spongy bone. True or False?

False?

Bone grows in diameter by adding new layers to the outside surface of the bone, while the medullary cavity is enlarged by the activity of cells on the inside surface.

True

Bone remodeling, especially bone resorption, plays a role in the maintenance of proper levels of calcium in the blood. True or False?

True

Which is NOT a part of the events that result in parathyroid hormone's control of blood calcium levels?

** DOUBLE CHECK ANSWER** PTH increases the number and activity of osteoclasts which dissolve bone matrix and release Ca²⁺ to diffuse into the bloodstream

Which is the proper sequence of steps in the healing of a fracture?

1. A fracture hematoma forms and bone cells in the region of the fracture die 2. Phagocytes and osteoclasts begin to remove the dead cells and damaged tissues around the hematoma 3. Fibroblasts and chondrocytes form the periosteum from the fibrocartilage callus 4. Osteoblasts from trabecular bone that joins together the fractured ends of the bone and bony callus replace fibrocartilage callus. 5. Bone remodeling occurs and compact bone replaces the spongy bone around the periphery of the fracture site.

Which of the following best describes the process of bone resorption in bone remodeling?

Acids and enzymes released by osteoclasts degrade collagen and dissolve away minerals, which diffuse through the interstitial fluid into nearby blood capillaries.

Which two minerals are stored in major quantities in bone tissue?

Calcium and phosphorus

When bones increase in thickness (diameter) as an individual grows to adulthood, which tissue or cells of the bone begin this growth process?

Cells of the periosteum differentiating into osteoblasts

Long bones adds to its length at the epiphyseal plate. In this region which type of cells proliferate, become calcified, and are eventually replaced with mature bone cells, thereby adding to the bone's length?

Chondrocytes

Which of the following hormones in both adult males and females, ultimately ends growth of long bones at the epiphyseal plate? (This happens sooner in women than in men, and so men on average are taller than women).

Estrogen

As long bones form in the fetus, the formation of the medullary cavity occurs because of the actions of osteoblast cells. True or False?

False

The process of intramembranous oddification generated bone within a pre-existing template composed of mesenchymal tissue. In contrast, endochondral ossification generates bone within a pre-existing template composed of _______.

Hyaline cartilage

Most of the bones of the skull are formed by this process.

Intramembranous ossification

Once osteoblasts have surrounded themselves with the extracellular matrix of bone tissue, they remain inside little chambers called _______________ where they carry on the metabolic functions that maintain bone tissue. At this point, the cells are called osteocytes.

Lacunae

Which is formed from the fusion of as many as 50 monocytes (a type of white blood cell)

Osteoclast

Which represents the correct sequence of development of bone cells?

Osteogenic cells > Osteoblasts > Osteocytes

Bone tissue stores 99% of the body's calcium. Calcium plays important roles beyond the mineralization of bones. The exchange of calcium between bone and body fluids (especially the blood0 is regulated by several hormones. Which of the following is the most important hormone regulating calcium exchange?

Parathyroid Hormone (PTH)

Compact bone is composed of units called osteons. In contrast, spongy bone is composed of ________.

Trabeculae

During a needle biopsy of a person's bone marrow, maybe to test for the presence of cancer, pain is felt when the needle passes through the periosteum because it is richly supplied with nerves. True or False?

True

In a newborn, all bone marrow is red, which means all of the infant's marrow can make blood cells. True or False?

True

Parathyroid hormone (PTH) is able to regulate calcium levels in the blood through a series of steps that provide control through a negative feedback system. True or False?

True

you would expect to find osteocytes active in bone building on the outside surface and osteoclasts active in dissolving bone on the medullary surface inside the bone. True or False?

True

In terms of bone health, why would a physician advise an older patient to do more weight-bearing activity such as walking, jogging, or use of moderate weights?

it promotes normal bone remodeling, osteoblasts deposit more mineral salts and collagen fibers as a response to mechanical stress, being sedentary (not physically active) promotes bone loss through resorption by osteoclasts, and bone formation in stressed bones is stimulated by the tug of muscles (when exercising)

With aging, bones can become more brittle. This brittleness is due to which factor?

with aging, there is a reduction in collagen synthesis by osteoblasts, which means a loss of tensile strength.