Gross Anatomy of Bone: Bone Marrow: Videos & Practice Problems

Bone marrow consists of two types: red marrow, responsible for hematopoiesis (the formation of blood cells), and yellow marrow, which stores triglycerides (fat). In adults, red marrow is found in spongy bone, while yellow marrow predominates, located in both spongy bone and the medullary cavity of long bones. Red marrow produces platelets, red blood cells, and white blood cells, crucial for maintaining blood health. As individuals age, yellow marrow can revert to red marrow if increased blood production is needed, highlighting the dynamic nature of bone marrow's function.

Bone Marrow

Bone marrow is a vital component of the skeletal system, filling the spaces within bones and serving essential functions through two distinct types of tissues: red marrow and yellow marrow. Red marrow is primarily responsible for hematopoiesis, the process of blood cell formation, which includes the production of platelets, red blood cells, and white blood cells. In adults, red marrow is located exclusively in spongy bone, particularly at the ends of long bones, such as the femur. In infants, red marrow is the predominant type, as they require a higher production of blood to support their rapid growth.

As individuals age, the need for constant blood production decreases, leading to a gradual transition from red marrow to yellow marrow. Yellow marrow serves a different purpose; it is primarily a site for triglyceride storage, which is why it appears yellow due to the fat content. Yellow marrow is found in both spongy bone and the medullary cavity, the hollow center of long bones. This cavity is where yellow marrow is often observed when bones are examined or consumed, such as in marrow bones given to pets.

Interestingly, yellow marrow is not static; it can revert to red marrow if the body requires an increased blood supply, demonstrating the dynamic nature of these tissues. In adults, yellow marrow becomes the predominant type, reflecting the body's changing needs over time. Overall, understanding the roles of red and yellow marrow highlights the complex functions of bone marrow in maintaining health and supporting bodily functions.

Gross Anatomy of Bone: Bone Marrow Example 1

Myelodysplastic syndrome (MDS) is a group of disorders characterized by ineffective hematopoiesis, which is the process of blood cell formation in the bone marrow. In individuals with MDS, the bone marrow does not produce healthy blood cells, leading to various blood-related issues. This condition primarily affects the red bone marrow, which is responsible for producing red blood cells, white blood cells, and platelets.

When a patient requires a blood transfusion, it often indicates a deficiency in one or more types of blood cells, particularly red blood cells, which can result from the impaired function of the red marrow. The red marrow, located in the epiphysis of long bones like the femur, is essential for generating these critical components of blood. In contrast, yellow marrow, found in the diaphysis, primarily serves as a fat storage area and does not contribute to blood cell production.

Thus, in the case of Priyanka, the need for a blood transfusion suggests that her red marrow is affected by myelodysplastic syndrome, leading to inadequate production of healthy blood cells. This understanding highlights the importance of red marrow in maintaining proper blood health and the implications of disorders like MDS on overall well-being.

Which of the following could be a reason why babies have relatively more red marrow than adults?

• A. Babies require red blood cells to be produced quickly to accommodate growth.
• B. The red marrow will aid in heat production keeping babies warm.
• C. Red marrow is located in spongy bone and babies' bones need to be softer than adults'.
• D. The triglycerides in red marrow aid in brain development.

Answer: (A)

In 1820, George Pollard and Charles Ramsdell were rescued after 93 days at sea in a small whaling boat after a sperm whale charged and sank their ship in what would become the inspiration for the novel Moby Dick. The two men were found adrift, sucking on the broken long bones of their dead shipmates. What nutrients were they receiving by sucking on the bones?

• A. Glucose and glycogen from the marrow.
• B. Triglycerides from adipose tissue.
• C. Protein and amino acids from epithelial tissue.
  
• D. NaCl from the bone matrix.

Answer: (B)

Here’s what students ask on this topic:

What is the primary function of red bone marrow?

The primary function of red bone marrow is hematopoiesis, which is the formation of blood cells. This includes the production of red blood cells, white blood cells, and platelets. Red marrow is crucial for maintaining blood health and is predominantly found in the spongy bone of adults. In infants, red marrow is more widespread, reflecting their higher need for blood cell production due to rapid growth. As individuals age, some red marrow converts to yellow marrow, but it can revert back if increased blood production is needed.

Where is yellow bone marrow found in adults?

In adults, yellow bone marrow is primarily found in the medullary cavity of long bones and also in some spongy bone. The medullary cavity is the hollow central part of the shaft of long bones. Yellow marrow stores triglycerides (fat), which serve as an energy reserve. While red marrow is responsible for blood cell production, yellow marrow's main function is nutrient storage. However, yellow marrow can revert to red marrow if the body requires increased blood cell production.

How does bone marrow change from infancy to adulthood?

In infancy, bone marrow is predominantly red, reflecting the high demand for blood cell production to support rapid growth. As individuals age, a significant portion of red marrow converts to yellow marrow, which stores fat. By adulthood, most bone marrow is yellow, found in the medullary cavity of long bones and some spongy bone. However, the body retains the ability to convert yellow marrow back to red marrow if increased blood production is needed, demonstrating the dynamic nature of bone marrow.

Can yellow bone marrow revert to red bone marrow?

Yes, yellow bone marrow can revert to red bone marrow if the body requires increased blood cell production. This process is essential during situations like severe blood loss or certain diseases where the demand for new blood cells rises. The ability to switch between yellow and red marrow highlights the dynamic and adaptive nature of bone marrow, ensuring that the body can meet its hematopoietic needs as required.

What types of cells are produced by red bone marrow?

Red bone marrow produces three main types of blood cells: red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). Red blood cells are responsible for carrying oxygen throughout the body. White blood cells play a crucial role in the immune system by fighting infections. Platelets are essential for blood clotting and wound healing. This production process, known as hematopoiesis, is vital for maintaining overall blood health and function.