Bone - MCAT Biological and Biochemical Foundations of Living Systems
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An individual with long cancer is advised to undergo radiation therapy. The radiation therapy destroys all of his bone marrow. Which of the following will be deficient in this individual?
An individual with long cancer is advised to undergo radiation therapy. The radiation therapy destroys all of his bone marrow. Which of the following will be deficient in this individual?
The primary function of red bone marrow is to make red blood cells in the process known as erythropoiesis. If all bone marrow is destroyed, then an individual will lose the ability to make red blood cells.
Myogenesis is performed by muscle fibers and satellite cells. Osteogenesis is performed by osteoblasts. Neurogenesis primarily occurs during early development and is performed by neural stem cells.
The primary function of red bone marrow is to make red blood cells in the process known as erythropoiesis. If all bone marrow is destroyed, then an individual will lose the ability to make red blood cells.
Myogenesis is performed by muscle fibers and satellite cells. Osteogenesis is performed by osteoblasts. Neurogenesis primarily occurs during early development and is performed by neural stem cells.
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Hematopoietic stem cells are the cells that are targeted in bone marrow transplants. These stem cells are found in the red marrow of the bone. Which part of a long bone would be targeted in order to extract hematopoietic stem cells for a transplant?
Hematopoietic stem cells are the cells that are targeted in bone marrow transplants. These stem cells are found in the red marrow of the bone. Which part of a long bone would be targeted in order to extract hematopoietic stem cells for a transplant?
Red bone marrow is filled with hematopoietic stem cells. Red bone marrow is found in the heads, or epiphyses, of long bones. Yellow marrow fills the medullary cavity and consists mostly of fats. The diaphysis contains the medullary cavity and therefore contains no red marrow. The periosteum has no marrow in it at all.
Red bone marrow is filled with hematopoietic stem cells. Red bone marrow is found in the heads, or epiphyses, of long bones. Yellow marrow fills the medullary cavity and consists mostly of fats. The diaphysis contains the medullary cavity and therefore contains no red marrow. The periosteum has no marrow in it at all.
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Hypoxia would result in which of the following?
Hypoxia would result in which of the following?
Since red bone marrow is a site of red blood cell and platelet production, hypoxia (low oxygen) would result in an increase in red marrow and therefore RBC concentration. Yellow bone marrow (typcially adipocyte-filled) can be converted into red bone marrow under conditions of low oxygen or blood loss.
Since red bone marrow is a site of red blood cell and platelet production, hypoxia (low oxygen) would result in an increase in red marrow and therefore RBC concentration. Yellow bone marrow (typcially adipocyte-filled) can be converted into red bone marrow under conditions of low oxygen or blood loss.
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What is the main function of red bone marrow?
What is the main function of red bone marrow?
Red bone marrow is primarily located in flat bones (such as the sternum and pelvis) and in the epiphyses of long bones. It is responsible for producing red blood cells, a process known as erythropoiesis. At birth, all bones of the human skeleton carry out erythropoesis, but many bones stop this function as the newborn ages.
It is important to note that yellow bone marrow is found in the medullary cavity within the diaphyses of long bones and assists in fat storage.
Red bone marrow is primarily located in flat bones (such as the sternum and pelvis) and in the epiphyses of long bones. It is responsible for producing red blood cells, a process known as erythropoiesis. At birth, all bones of the human skeleton carry out erythropoesis, but many bones stop this function as the newborn ages.
It is important to note that yellow bone marrow is found in the medullary cavity within the diaphyses of long bones and assists in fat storage.
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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?
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?
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.
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.
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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?
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?
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.
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.
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Which of the following is true relating cartilage to the skeletal system?
Which of the following is true relating cartilage to the skeletal system?
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.
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.
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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?
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?
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.
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.
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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?
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?
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.
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.
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What type of bone cell is responsible for resorbing bone tissue?
What type of bone cell is responsible for resorbing bone tissue?
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.
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.
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How do bones maintain a functional weight as they grow?
How do bones maintain a functional weight as they grow?
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.
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.
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Where are osteocytes located?
Where are osteocytes located?
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.
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.
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The diaphysis is able to grow in length because of thin layers of cartilage cells located in which of the following regions?
The diaphysis is able to grow in length because of thin layers of cartilage cells located in which of the following regions?
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.
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.
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Which cells are responsible for building bone?
Which cells are responsible for building bone?
Osteoblasts form bone by crystalizing calcium phosphate around collagen.
Osteoblasts form bone by crystalizing calcium phosphate around collagen.
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A normally active man is in a coma after a major car accident. He remains hospitalized until he wakes up three weeks later. After waking, he finds himself unable to return immediately to his previous activity level. Tests show that he has experienced a decrease in muscle tone and bone mass.
During the man's hospitalization, which of the following cells was likely most active?
A normally active man is in a coma after a major car accident. He remains hospitalized until he wakes up three weeks later. After waking, he finds himself unable to return immediately to his previous activity level. Tests show that he has experienced a decrease in muscle tone and bone mass.
During the man's hospitalization, which of the following cells was likely most active?
Osteoclasts are responsible for bone resorption and osteoblasts are responsible for bone re-formation. While bed-ridden, this man will have a decrease in osteoblast production since he was not moving during the three weeks he was in a coma. His osteoclast production, however, would probably stay the same as it was before the accident (and therefore the man would experience atrophy during his time of being immobile).
Osteoclasts are responsible for bone resorption and osteoblasts are responsible for bone re-formation. While bed-ridden, this man will have a decrease in osteoblast production since he was not moving during the three weeks he was in a coma. His osteoclast production, however, would probably stay the same as it was before the accident (and therefore the man would experience atrophy during his time of being immobile).
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Parathyroid hormone (PTH) is responsible for increasing blood calcium levels in the body. Which cell in the bones would be stimulated by PTH in order to increase blood calcium levels?
Parathyroid hormone (PTH) is responsible for increasing blood calcium levels in the body. Which cell in the bones would be stimulated by PTH in order to increase blood calcium levels?
Osteoclasts are responsible for resorbing bone matrix and releasing key minerals, including calcium, back into the bloodstream. They are stimulated by parathyroid hormone when blood calcium levels are low.
Osteoblasts build bone matrix and later differentiate into osteocytes, which preserve the bone tissue.
Osteoclasts are responsible for resorbing bone matrix and releasing key minerals, including calcium, back into the bloodstream. They are stimulated by parathyroid hormone when blood calcium levels are low.
Osteoblasts build bone matrix and later differentiate into osteocytes, which preserve the bone tissue.
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Which of the following cell types would be inhibited in the event of hypercalcemia?
Which of the following cell types would be inhibited in the event of hypercalcemia?
In the event of hypercalcemia the body has elevated blood calcium levels. As a result, osteoclasts, which are responsible for the resorption of bone matrix and the release of calcium into the bloodstream, would experience reduced function.
Osteoblasts, in contrast, help to synthesize bone and would be stimulated by high blood calcium levels to remove calcium from the blood and sequester it in bone. Osteocytes, sometimes known as osteogenitor cells, are the progenitor cells to osteoblasts.
In the event of hypercalcemia the body has elevated blood calcium levels. As a result, osteoclasts, which are responsible for the resorption of bone matrix and the release of calcium into the bloodstream, would experience reduced function.
Osteoblasts, in contrast, help to synthesize bone and would be stimulated by high blood calcium levels to remove calcium from the blood and sequester it in bone. Osteocytes, sometimes known as osteogenitor cells, are the progenitor cells to osteoblasts.
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Which of the following would increase blood calcium concentration?
Which of the following would increase blood calcium concentration?
This question requires a strong understanding of factors affecting bone resorption and bone re-formation.
Bone re-formation takes place when osteoblasts use calcium and phosphate from the blood to form bone. Calcitonin stimulates osteoblasts to form bone. Parathyroid hormone (PTH), on the other hand, stimulates bone resorption and causes osteoclasts to break down bone, causing blood calcium and phosphate levels to increase.
Of the possible answers, only increased osteoclast activity would result in higher blood calcium levels. Increased osteoblast activity, decreased parathyroid hormone, and increased calcitonin would all result in lower blood calcium levels.
This question requires a strong understanding of factors affecting bone resorption and bone re-formation.
Bone re-formation takes place when osteoblasts use calcium and phosphate from the blood to form bone. Calcitonin stimulates osteoblasts to form bone. Parathyroid hormone (PTH), on the other hand, stimulates bone resorption and causes osteoclasts to break down bone, causing blood calcium and phosphate levels to increase.
Of the possible answers, only increased osteoclast activity would result in higher blood calcium levels. Increased osteoblast activity, decreased parathyroid hormone, and increased calcitonin would all result in lower blood calcium levels.
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function to synthesize bone tissue and function to reabsorb bone tissue.
function to synthesize bone tissue and function to reabsorb bone tissue.
Bones consist of two types of cells that regulate bone growth: osteoblasts and osteoclasts. Osteoblasts lay down collagen and other important organic substances that are required to synthesize bone tissue, whereas osteoclasts reabsorb existing bone tissue. The activity of both cells is important for repair, growth, and maintenance of bone tissue.
Note that a third type of cell, osteocytes, is also found in bone, but does not play as much of an active role in maintaining bone structure.
Bones consist of two types of cells that regulate bone growth: osteoblasts and osteoclasts. Osteoblasts lay down collagen and other important organic substances that are required to synthesize bone tissue, whereas osteoclasts reabsorb existing bone tissue. The activity of both cells is important for repair, growth, and maintenance of bone tissue.
Note that a third type of cell, osteocytes, is also found in bone, but does not play as much of an active role in maintaining bone structure.
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Several tests reveal that a unknown hormone reverses the effects of parathyroid hormone. What can you conclude about this unknown hormone?
Several tests reveal that a unknown hormone reverses the effects of parathyroid hormone. What can you conclude about this unknown hormone?
The question states that the unknown hormone has the opposite effect of parathyroid hormone. Recall that parathyroid hormone functions to increase blood calcium levels; therefore, this unknown hormone must decrease blood calcium levels.
When blood calcium levels increase due to parathyroid hormone, osteoclasts in bones break down the bone matrix and release the calcium into the blood. This means the activity of the unknown hormone must inhibit the activity of osteoclasts to decrease blood calcium levels. This hormone is most likely released to prevent bone loss.
The unknown hormone in this question would most likely be calcitonin. Calcitonin decreases blood calcium levels and is very important in menopausal and pregnant women who have a higher risk of having excessive bone loss.
The question states that the unknown hormone has the opposite effect of parathyroid hormone. Recall that parathyroid hormone functions to increase blood calcium levels; therefore, this unknown hormone must decrease blood calcium levels.
When blood calcium levels increase due to parathyroid hormone, osteoclasts in bones break down the bone matrix and release the calcium into the blood. This means the activity of the unknown hormone must inhibit the activity of osteoclasts to decrease blood calcium levels. This hormone is most likely released to prevent bone loss.
The unknown hormone in this question would most likely be calcitonin. Calcitonin decreases blood calcium levels and is very important in menopausal and pregnant women who have a higher risk of having excessive bone loss.
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