What is the function of osteoblasts?
Osteoblasts secrete an acid that breaks down the epiphyseal plate.
Osteoblasts are large multinucleated cells that break down the calcified bone matrix.
Osteoblasts deposit bone matrix around themselves and become osteocytes when they are isolated in lacunae
Osteoblasts secrete collagen fibers and then mature into osteoclasts.
The Correct Answer is C
Bone is a living connective tissue that undergoes continuous growth, repair, and remodeling throughout life. These processes are carried out by specialized bone cells, including osteoblasts, osteocytes, and osteoclasts. Osteoblasts are the primary bone-forming cells responsible for synthesizing and secreting the organic components of bone matrix. As they become surrounded by the matrix they produce, they differentiate into osteocytes, which maintain the mature bone tissue.
A. Osteoblasts secrete an acid that breaks down the epiphyseal plate: osteoblasts are bone-forming cells, not bone-resorbing cells. The secretion of acids and proteolytic enzymes to dissolve mineralized tissue is a function of osteoclasts. Additionally, the epiphyseal plate is composed of cartilage, and its closure occurs through endochondral ossification rather than acid-mediated destruction.
B. Osteoblasts are large multinucleated cells that break down the calcified bone matrix: This describes osteoclasts rather than osteoblasts. Osteoclasts are large multinucleated cells derived from the monocyte-macrophage lineage and are specialized for bone resorption. They release hydrochloric acid and lysosomal enzymes to dissolve mineralized bone and degrade collagen fibers. Osteoblasts, in contrast, are mononuclear cells responsible for bone formation.
C. Osteoblasts deposit bone matrix around themselves and become osteocytes when they are isolated in lacunae: osteoblasts synthesize osteoid, the unmineralized organic matrix of bone composed primarily of type I collagen and ground substance. As mineralization occurs, some osteoblasts become trapped within the matrix they have secreted. Once enclosed in small spaces called lacunae, they differentiate into osteocytes, which maintain bone tissue and regulate mineral exchange. This transformation is a normal part of bone growth and remodeling.
D. Osteoblasts secrete collagen fibers and then mature into osteoclasts: osteoblasts and osteoclasts arise from different cellular lineages and do not transform into one another. Osteoblasts originate from mesenchymal stem cells, whereas osteoclasts develop from hematopoietic stem cells of the monocyte-macrophage lineage. Although osteoblasts do secrete collagen fibers as part of osteoid formation, they mature into osteocytes, not osteoclasts.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
The marked structure is the temporal lobe, one of the four major lobes of the cerebral cortex located on the lateral and inferior aspect of each cerebral hemisphere, beneath the lateral (Sylvian) fissure. It is structurally composed of multiple gyri and sulci that increase cortical surface area for higher processing capacity. The temporal lobe plays a crucial role in auditory processing, language comprehension (Wernicke’s area in the dominant hemisphere), memory formation via the hippocampal connections, and emotional responses through limbic system integration.
A. Occipital lobe: The occipital lobe is located at the posterior aspect of the cerebral hemispheres and is primarily responsible for visual processing. It contains the primary visual cortex (V1), which interprets input from the retina via the optic pathways. Unlike the temporal lobe, it does not process auditory information or language comprehension. Its position at the back of the brain also distinguishes it from the lateral location of the temporal lobe.
B. Frontal lobe: The frontal lobe is located in the anterior portion of the cerebral hemisphere and is responsible for executive functions such as reasoning, planning, voluntary motor control, and speech production (Broca’s area). It also regulates personality, judgment, and emotional control. Compared to the temporal lobe, it is more anterior and superior, and is not primarily involved in auditory perception or memory consolidation.
C. Parietal lobe: The parietal lobe is located superiorly on the cerebral hemisphere and is mainly responsible for somatosensory processing, including touch, temperature, pain, and proprioception. It integrates sensory input to form spatial awareness and body orientation. Unlike the temporal lobe, it is positioned superiorly and is not directly involved in auditory processing or memory systems.
D. Temporal lobe: The temporal lobe is located on the lateral aspect of the brain, inferior to the lateral sulcus. It contains the primary auditory cortex and is essential for processing sound, language comprehension, and memory encoding via hippocampal connections. It also plays a role in emotional regulation through limbic system interactions. Since the marked area is lateral and associated with auditory and language functions, it corresponds to the temporal lobe.
Correct Answer is D
Explanation
The marked structure is the sagittal suture, a fibrous immovable joint (synarthrosis) located between the two parietal bones along the midline of the superior skull. It runs anteroposteriorly from the coronal suture anteriorly to the lambdoid suture posteriorly. The sagittal suture plays a key role in skull growth during childhood by allowing expansion of the cranial vault to accommodate brain development. It later ossifies progressively in adulthood, becoming more rigid.
A. Coronal suture: The coronal suture is located between the frontal bone and the paired parietal bones. It runs transversely across the skull from side to side, separating the anterior cranial vault from the superior region. It allows growth of the skull in the anterior-posterior direction during early development. Unlike the sagittal suture, it is not located along the midline but rather forms a horizontal junction.
B. Lambdoid suture: The lambdoid suture is found at the posterior aspect of the skull, where the parietal bones meet the occipital bone. It has a characteristic inverted “V” or lambda shape. It plays a role in posterior cranial expansion during development. Compared to the sagittal suture, it is posterior and not located along the midline of the skull.
C. Squamous suture: The squamous suture is located laterally between the temporal bone and the parietal bone. It is curved and relatively flat, forming part of the lateral skull wall. It allows articulation between these bones and contributes to cranial stability. It is not midline like the sagittal suture and is instead positioned on the sides of the skull.
D. Sagittal suture: The sagittal suture is a fibrous joint located along the midline between the two parietal bones. It extends from the coronal suture anteriorly to the lambdoid suture posteriorly. It is a key growth site during infancy and childhood, allowing expansion of the skull to accommodate brain growth. Since the circled structure lies centrally between the parietal bones, it corresponds to the sagittal suture.
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