Lesson 6.4-6.12

Bill, age 15, is still growing, but his older sister Andrea, age 19, has stopped. What has changed in Andrea's bones?

Her epiphyseal plates have ossified.

All of the following are characteristics of periosteum:

It provides a route for the blood and nervous supply. It actively participates in bone growth and repair. It has two layers, an inner layer and an outer layer.

All of the following result in decreased calcium levels in the bloodstream, except:

PTH stimulation of osteoclasts.

To form perforating fibers, osteoblasts from the cellular layer of the periosteum cement collagen fibers from tendons, ligaments, and joint capsules into which structures?

circumferential lamellae

Which type of fracture occurs in vertebrae that are subjected to extreme stresses?

compression fracture

Remnants of osteons whose matrix components have been almost completely recycled by osteoclasts are known as which of the following?

interstitial lamellae

Which component is not present in spongy bone?

osteons

The trabeculae of spongy bone

are organized along stress lines.

Bone plays a central role in the regulation of blood levels of

calcium.

What characteristic may cause life-threatening issues in individuals with Marfan syndrome?

genetic mutation that affects the structure of connective tissue throughout the body

At which point during embryonic development can most of the bones of the adult skeleton be identified?

16 weeks

The following are major steps in the process of intramembranous ossification. 1. Clusters of osteoblasts form osteoid that becomes mineralized. 2. Osteoblasts differentiate within mesenchymal connective tissue. 3. Spicules of bone radiate out from the ossification centers. 4. Mesenchymal cells aggregate. What is the correct order for these events?

4, 1, 2, 3

Which of the following describes spiral fractures?

fractures that are produced by twisting stresses that spread along the length of the bone

Cells of the perichondrium need to take on a new role as ossification begins. They will become __________.

osteoblasts and begin to deposit bone matrix

At puberty

osteoblasts begin producing bone faster than chondrocytes are producing new epiphyseal cartilage.

Cells that secrete the organic components of the bone matrix are called

osteoblasts.

The process of osteolysis is performed by which cell population?

osteoclasts

Blood is distributed from the surface of a bone to deeper central canals through channels known as

perforating canals.

As blood vessels extend into the spaces left by dying chondrocytes, the models begin to ossify internally. Where does internal ossification begin?

the primary ossification center in the diaphysis