Bone Marrow and Erythropoiesis
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MCAT Biological and Biochemical Foundations of Living Systems › Bone Marrow and Erythropoiesis
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?
The epiphysis
The diaphysis
The periosteum
The medullary cavity
Explanation
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.
Hypoxia would result in which of the following?
Yellow bone marrow being converted to red bone marrow for increased red blood cell production
Red bone marrow being converted to adipocytes for increased energy storage
Blood vessel density being increased through the spongy bone for increased oxygen delivery
The ratio of spongy bone to compact bone being increased to accommodate storage of red blood cells
Explanation
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.
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?
Erythropoiesis
Epithelial tissue synthesis
Myogenesis
Neurogenesis
Osteogenesis
Explanation
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.
What is the main function of red bone marrow?
It carries out erythropoesis
It helps with immunity
It breaks down worn out red blood cells
It creates osteoblasts
It stores fat cells
Explanation
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.