Yellow bone marrow consists mostly of:
red blood cells
fat
white blood cells
cartilage
The Correct Answer is B
Rationale:
A. Red blood cells are primarily produced in red bone marrow, not yellow bone marrow. Red marrow is found mainly in flat bones (such as the pelvis, sternum, and ribs) and is the primary site of hematopoiesis (formation of blood cells).
B. Yellow bone marrow is made up largely of adipocytes (fat cells). Its main function is fat storage, which serves as an energy reserve. In adults, much of the red marrow gradually converts into yellow marrow with age, especially in the long bones.
C. Like red blood cells, most white blood cells are formed in red bone marrow, not yellow marrow. While yellow marrow can, under extreme conditions (such as severe blood loss), revert to red marrow to aid in hematopoiesis, its normal composition is primarily fat.
D. Cartilage is a connective tissue found in joints, the rib cage, ear, nose, and other structures. It is not a component of bone marrow.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Rationale:
A. Commonly called the collarbone, it is a long bone that connects the sternum to the scapula. It is not the breastbone itself.
B. The sternum, or breastbone, is a flat bone located in the center of the chest. It consists of three parts: the manubrium (upper portion), the body (middle and largest portion), and the xiphoid process (the small inferior tip). It serves as an attachment site for the ribs and clavicles, playing a vital role in protecting the heart and lungs.
C. Also called the shoulder blade, it is located on the posterior thoracic wall and does not form the breastbone.
D. This is the upper portion of the sternum, but it is not the entire breastbone.
Correct Answer is D
Explanation
Rationale:
A. Adenosine triphosphate is the energy currency of the cell and is essential for muscle contraction and relaxation, but it is not stored or released by the sarcoplasmic reticulum. Instead, ATP is produced in the mitochondria and consumed during the contraction cycle.
B. This enzyme is found in the synaptic cleft and is responsible for breaking down acetylcholine after it has transmitted a nerve impulse. It is not released from the sarcoplasmic reticulum.
C. This neurotransmitter is released from motor neurons into the neuromuscular junction to initiate muscle contraction. However, it is secreted by nerve endings, not by the sarcoplasmic reticulum.
D. When an action potential travels along the muscle fiber, it stimulates the sarcoplasmic reticulum to release stored calcium ions. Calcium then binds to troponin on the actin filaments, causing tropomyosin to shift and expose the binding sites for myosin, thus initiating the cross-bridge cycle that produces contraction.
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