Chapter 6: The Skeletal System

The femur can withstand ________ times the body's weight without breaking.

10 to 15

________ accounts for almost two-thirds of the weight of bone.

Calcium phosphate

Through the action of osteoclasts,

bony matrix is dissolved.

Part complete A rib is an example of a ________ bone.

flat

A small rough bump on bone where a tendon attaches is called a

tuberosity.

Which of the following bones is classified as "irregular" in shape?

vertebra

________ fractures are completely internal; they do not break through the skin.

Closed or simple

Define intramembranous ossification. (Module 6.8A)

Intramembranous ossification is bone formation within connective tissue without the prior development of a cartilage model.

What structure allows a bone to grow in length?

epiphyseal cartilages

The articular cartilage of a typical long bone covers portions of what part of the bone?

epiphysis

Put the following steps of fracture repair into the correct order. 1. Extensive bleeding occurs. 2. An internal callus forms from a network of spongy bone. 3. Hematoma is formed to close off blood flow. 4. Remodeling continues by osteoblasts and osteoclasts leaving little evidence of the break. 5. Osteoblasts replace the central cartilage of the callus.

1,3,2,5,4

The following are important steps in the process of endochondral ossification. 1. Blood vessels grow around the edges of the cartilage and perichondrium differentiates into osteoblasts. 2. Capillaries and osteoblasts migrate to the epithyses forming the secondary ossification centers. 3. Chondrocytes enlarge and the surrounding matrix begins to calcify. 4. Remodeling continues and the shaft becomes thicker. 5. Blood vessels penetrate the cartilage and invade the central region forming the primary ossification center. What is the correct order for these events?

3, 1, 5, 4, 2

Define open fracture and closed fracture. (Module 6.12B)

An open fracture is one where the bone pierces the skin; a closed fracture is one where no bone pierces the skin.

Define osteon. (Module 6.5A)

An osteon is the functional unit of compact bone.

Where is articular cartilage found, and how is it nourished? (Module 6.3C)

Articular cartilage is found covering both epiphyseal portions of articulating bone and nutrients diffuse from synovial fluid within the joint.

Why is pituitary growth failure less common today in the United States? (Module 6.9A)

Because children can be treated with synthetic human growth hormone if they are deficient.

A transverse fracture of the wrist that may be comminuted is called a ________ fracture.

Colles

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.

Which of the following statements about Marfan's syndrome is false?

It results in short, stubby fingers.

________ free calcium from bone to maintain blood calcium levels.

Osteoclasts

A fracture at the ankle involving both lower leg bones is often called a ________ fracture.

Pott's

Describe the axial and appendicular divisions of the skeleton. (Module 6.1A)

The axial skeleton consists of the bones of the skull, vertebral column, and thorax. The appendicular skeleton consists of the bones of the limbs, pectoral girdle and pelvic girdle.

How would denaturing collagen from the bone matrix affect the physical properties of a bone?

The bone would be more brittle.

How would the compressive strength of a bone be affected if the ratio of collagen to hydroxyapatite increased? (Module 6.4C)

The compressive strength would decrease and the bone would become more flexible.

As a bone increases in diameter, what happens to the medullary cavity? (Module 6.6B)

The medullary cavity increases in diameter because bone matrix is removed by osteoclasts.

Which of the following statements regarding the homeostasis regulation of blood calcium is FALSE?

The three main organs that serve as the site for the regulation of blood calcium levels are the bones, the intestines, and the pancreas. (kidney)

When testosterone is increased in males at puberty, epiphyseal plates

accelerate rapidly

In compact bone, the osteons are

arranged in concentric lamellae.

The central canal of an osteon contains

blood vessels.

Which of the following is formed by intramembranous ossification?

both the roof of the skull and the clavicle

Which of the following hormones is currently thought to decrease plasma calcium levels in pregnant women and children?

calcitonin

PTH promotes the formation of which hormone?

calcitriol

Which hormone works directly in the intestine to increase plasma calcium levels?

calcitriol

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

calcium.

The most abundant mineral in the human body is

calcium.

The narrow passageways that contain cytoplasmic extensions of osteocytes are called

canaliculi.

In appositional growth, successive layers of what structure are added to the outer surface of the bone?

circumferential lamellae

A ________ fracture produces shattered bone fragments.

comminuted

An open, or ________, fracture projects through the skin.

compound

The fracture of vertebrae subjected to extreme vertical stress is called a ________ fracture.

compression

The hormone calcitonin

decreases the level of calcium ion in the blood.

After a fracture of the diaphysis has healed, the thickened region that results is called the

external callus.

Identify the six broad categories for classifying a bone according to shape. (Module 6.2A)

flat, sutural, long, irregular, sesamoid, short

A rounded hole through a bone is termed a

foramen.

A shallow depression on a bone is termed a

fossa.

List the steps involved in fracture repair, beginning just after the fracture occurs. (Module 6.12A)

fracture hematoma formation, callus formation, spongy bone formation, compact bone formation

Damage to a bone because of extreme load, sudden impact, or stresses applied from an unusual direction is called a

fracture.

In a ________ fracture, one side of the shaft is split and the other side is bent.

greenstick

The expanded articular end of an epiphysis that is separated from the shaft by a narrower neck is termed a

head.

While on a school skiing trip in Colorado, Heidi falls and breaks her tibia and fibula in a Pott's fracture. What would you expect as a prominent part of her clinical assessment several hours after the fall?

hematoma

A hard ossified bone in an adult actually begins within the embryo as a miniature version composed of __________.

hyaline cartilage

In bone, the calcium phosphate forms crystals of

hydroxyapatite.

Which of the following would NOT be a way that parathyroid hormone (PTH) could alter plasma calcium levels? (Which one of the following is FALSE?)

increase osteoblasts on bone

When the epiphyseal plate is replaced by bone,

long bones have reached their adult length.

The medullary cavity of bones contains

marrow.

Which of the following best matches osteocyte?

mature bone cell

The narrow region between the head and diaphysis of a long bone is called the

neck.

The opening in the diaphysis through which blood vessels provide oxygen to osteons is named the ________ foramen.

nutrient

During the process of ________, an existing tissue is replaced by bone.

ossification

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

osteoblasts and begin to deposit bone matrix

Which is greater?

osteoclast activity when calcitonin is absent

The structural units of mature compact bone are called

osteons.

Identify the hormone that stimulates the release of calcium ions from bone matrix. Explain its mechanism of action. (Module 6.11A)

parathyroid hormone; increases osteoclast break down of bone matrix

A ________ fracture is produced by twisting stresses applied to the bone.

spiral

Small, oddly shaped bones that fill gaps between bones of the skull are called ________ bones.

sutural

Which of the following is not a function of the skeletal system?

temperature regulation

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

A fracture of the bone across its long axis is called a(n) ________ fracture.

transverse