MCAT Biology : Bone Development and Growth

Study concepts, example questions & explanations for MCAT Biology

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : Bone

A doctor oberves a teenager who noticed that one of his legs is about two inches longer than the other. He also sees that the patient had broken one of his legs when he was 8 years old, but the patient's notes don't indicate which leg. What conclusion is the doctor likely to come to?

Possible Answers:

The patient broke the longer leg on the periosteum.

The patient broke the shorter leg on the epiphyseal plate.

The patient broke the shorter leg on the diaphysis.

The patient broke the longer leg on the epiphyseal plate.

The patient broke the longer leg in the diaphysis.

Correct answer:

The patient broke the shorter leg on the epiphyseal plate.

Explanation:

The epiphyseal plate is the site of longitudinal growth in bones. The patient likely broke the leg along the plate, which caused it to grow less than the other leg.

Example Question #1 : Bone Development And Growth

A fetal rat's femoral cartilage is injected with a marker prior to endochondral ossification. The marker becomes deactivated as the cartilage is converted to bone. In which part of the femur would we expect to see a high concentration of the marker once the rat reaches adulthood?

Possible Answers:

Within the medullary cavity

In the compact bone of the diaphysis

On the articular surface of the bone

In the spongy bone of the diaphysis

Correct answer:

On the articular surface of the bone

Explanation:

The first important concept to understand for this question is the process of endochondral ossification. In this process, cartilage is converted into bone during the early life of an organism. Since the question specifies that the rat has reached adulthood, it must refer to the parts of the final bone product that remain as cartilage once endochondral ossification is complete.

Spongy bone and compact bone in the diaphysis have already ossified, and the medullary cavity contains bone marrow and adipose. To find cartilage in any of these regions would indicate a developmental abnormality.

The ends of bones that are in contact with other bones are protected from frictional damage by articular cartilage. Articular cartilage is essential to maintaining healthy joint function. Deterioration of this cartilage results in arthritis, or inflammation in the joints.

Example Question #2 : Bone Development And Growth

Which of the following is true relating cartilage to the skeletal system?

Possible Answers:

Cartilage is an intermediate that is stiffer than muscle, but softer than bone

Cartilage has the ability to regenerate

Cartilage is produced via the breakdown of muscle and bone

There are two types of cartilage

Cartilage is not found in joints and vertebral discs

Correct answer:

Cartilage is an intermediate that is stiffer than muscle, but softer than bone

Explanation:

Cartilage is a flexible, avascular connective tissue. It is less flexible than muscle, but softer and more flexible than bone. These properties make it an ideal candidate for joints, providing a medium between the muscles and bones that enact forces on the joint. Cartilage is found on the epiphyses of long bones and between certain bones, such as vertebrae, to cushion the motion of the joints.

Due to its avascular nature, cartilage does not easily regenerate. It is formed by chondroblasts (cartilage cells) in a chondrin matrix. In endochondral ossification, cartilage can be used as a precursor to bone, but will never be formed as a result of bone breakdown. Finally, there are three types of cartilage: elastic cartilage, hyaline cartilage, and fibrous cartilage.

Example Question #2 : Bone

The diaphysis is able to grow in length because of thin layers of cartilage cells located in which of the following regions?

Possible Answers:

Medullary cavity

Epiphyseal plate

Periosteum

Haversian canal

Marrow

Correct answer:

Epiphyseal plate

Explanation:

Thin layers of cartilage cells in the epiphyseal plate enable the diaphysis (bone shaft) to grow in length. The epiphyseal line forms when growth stops and ossification occurs, permanently fusing the diaphysis and epiphysis.

The periosteum is a tough connective tissue sheath that covers the outer surface of bones. The medullary cavity is a hollow cylinder inside the diaphysis. The medullary cavity contains bone marrow, which contains blood cells in different stages of development. The Haversian canals perforate bony structure and contain blood vessels, lymph vessels, and nerves. 

Example Question #3 : Bone

What type of bone cell is responsible for resorbing bone tissue?

Possible Answers:

Lacunae

Osteoclasts

Cartilage

Osteoblasts

Osteocytes

Correct answer:

Osteoclasts

Explanation:

Osteoclasts are bone cells that are responsible for resorbing—or breaking down—bone tissue. Osteoblasts, on the other hand, deposit bone tissue.

Cartilage is not a type of bone cell at all; it is a type of connective tissue consisting of chondrocytes suspended in an avascular matrix. Lacunae are small cavities within the bone matrix that house osteocytes; osteocytes are mature bone cells.

Example Question #5 : Bone Development And Growth

How do bones maintain a functional weight as they grow?

Possible Answers:

Osteoblasts secrete acidic compounds, which dissolve some of the adjoining matrix

Osteoblasts creates new lacuna to surround bone cells

Osteocytes form long fibers around the medullary cavity

Osteoclasts lining the medullary cavity remove interior layers of matrix

Osteocytes create new Haversian systems to limit the bone weight

Correct answer:

Osteoclasts lining the medullary cavity remove interior layers of matrix

Explanation:

Osteoclasts dissolve bony matrix and repatriate calcium as the bone grows. This expands the meduallary cavity and maintains a manageable mass for the bones, while allowing the body to recycle valuable calcium deposits.

Example Question #4 : Bone

Where are osteocytes located?

Possible Answers:

The lining of the medullary cavity

The lacunae of Haversian systems

Surrounding the growth plates

Throughout the hydroxyapatite matrix

Beneath the periosteum

Correct answer:

The lacunae of Haversian systems

Explanation:

Osteoytes, the long-lived star-shaped cells found in established bones, are primarily found within Haversian systems—the target-shaped tubes of bone matrix. They are encased in a bubble of interstitial fluid known as a lacuna.

Example Question #1 : Bone Development And Growth

An adolescent girl is suffering from reduced longitudinal bone growth in her humerus. Which of the following bone regions should be examined closely in order to determine the cause of the growth deficiency?

Possible Answers:

The periosteum

The diaphysis

Articular cartilage

The epiphyseal plate

Correct answer:

The epiphyseal plate

Explanation:

Longitudinal bone growth occurs at the epiphyseal plate through the process of endochondral ossification. Cartilage cells undergo rapid mitosis in this region forming the structure that is later replaced by bone tissue.

Example Question #8 : Bone Development And Growth

In childbirth, the child’s skull is flexible due to fontanelles, or soft regions that are composed of connective tissue. Through what process does the connective tissue of the infant’s skull become bone?

Possible Answers:

Endochondral ossification

Intramembranous ossification

Bony secretion

Compact bone resorption

Correct answer:

Intramembranous ossification

Explanation:

Intramembranous ossification is the process in which bones are formed within dermal tissue. This process is responsible for forming the flat bones of the skull, as well as the clavicle. Other bones of the body are formed by the process of endochondral ossification, in which cartilage is replaced by bone tissue.

Learning Tools by Varsity Tutors

Incompatible Browser

Please upgrade or download one of the following browsers to use Instant Tutoring: