Difference Between Red and Yellow Bone Marrow

The key difference between red and yellow bone marrow is that the red bone marrow is responsible for the creation of new blood cells every minute in our body while the yellow bone marrow is responsible for the fat storage.

Bone marrow occupies in the spaces between the trabeculae of bones and generally consists of several elements, including blood vessels, nerves, mononuclear phagocytes, stem cells, blood cells at different stages of maturation and fat. It is the fourth biggest organ system of the human body when compared to its body weight. Accordingly, the main role of bone marrow is to provide red blood cells, white blood cells, and platelets, based on the body’s requirements. Apart from that, it also acts as fat reserves in the body. In adult humans, active bone marrow is present in the pelvic bones, vertebrae, cranium and mandible, sternum and ribs, and proximal ends of the humerus and femur. According to the composition, there are two types of bone marrow; yellow bone marrow and red bone marrow. The purpose of this article is to discuss the difference between red and yellow bone marrow.

CONTENTS

1. Overview and Key Difference
2. What is Red Bone Marrow
3. What is Yellow Bone Marrow
4. Similarities Between Red and Yellow Bone Marrow
5. Side by Side Comparison – Red vs Yellow Bone Marrow in Tabular Form
6. Summary

What is Red Bone Marrow?

Red marrow composes a delicate, highly vascular, fibrous tissue containing hematopoietic stem cells. These stem cells produce the cellular components including red blood cells, white blood cells, and platelets to meet the requirements for oxygenation, coagulation and immunity in organisms. Red bone marrow also contributes to the destruction of old red blood cells in the body. At birth, only red marrow is present in the body.

However, with birth, conversion of the red marrow to yellow marrow begins immediately, and it progresses from the peripheral to the central parts of the skeleton. In higher vertebrates such as mammals, blood formation in adults takes place mainly in the red bone marrow. But in lower vertebrates, some other organs such as liver and spleen may also produce blood cells.

What is Yellow Bone Marrow?

Yellow bone marrow contains more fat (80%) and is haematopoietically inactive. It is found in the medullary cavity and the hollow interior of the middle portion of long bones. Yellow bone marrow mainly serves as storage sites of fat and may be converted to red bone marrow under certain conditions such as severe blood loss or fever.

Normally these fat cells are the last resorts for body’s energy requirements and can be used in the event of extreme hunger. But, its main function is the conversion into red marrow upon any requirement by the body. The yellow marrow can convert itself within 1 to 2 hours to take over the role of red marrow.

What are the Similarities Between Red and Yellow Bone Marrow?

• Both types of bone marrow are enriched with blood vessels and capillaries.
• Also, both contain two types of stem cells; mesenchymal and hematopoietic stem cells.

What is the Difference Between Red and Yellow Bone Marrow?

The key difference between red and yellow bone marrow depends on the main function of each bone marrow. Red bone marrow creates new blood cells while yellow bone marrow stores fat. Furthermore, red bone marrow contains 40% water, 40% fat, and 20% proteins and is highly vascularized. In contrast, yellow bone marrow contains 15% water, 80% fat, and 5% protein and is poorly vascularized. Thus, it is another difference between red and yellow bone marrow.

Moreover, in adults, the peripheral skeleton contains yellow bone marrow, whereas red bone marrow is confined to the spine, the ribs, proximal femur and humerus and the skull. Hence, it is also a difference between red and yellow bone marrow. One more significant difference between red and yellow bone marrow is that the red bone marrow is composed of leucocytes and platelet precursors and is haematopoietically active, whereas yellow bone marrow is haematopoietically inactive. Besides, the amount of red marrow continues to decrease while the amount of yellow marrow continues to increase throughout the lifetime. Therefore, we can consider this also as a difference between red and yellow bone marrow.

Summary – Red vs Yellow Bone Marrow

There are two types of bone marrow namely red bone marrow and yellow bone marrow. Red bone marrow contains hematopoietic stem cells and is responsible for the formation of new blood cells such as red blood cells, white blood cells and platelets. On the other hand, yellow bone marrow contains mesenchymal stem cells and is responsible mainly for fat storage. Furthermore, red bone marrow is a highly vascularized tissue while yellow bone marrow is poorly vascularized. Also, the amount of red bone marrow decreases with ageing while the amount of yellow bone marrow increases with ageing. Thus, this summarizes the difference between red and yellow bone marrow.

Reference:

1. Nichols, Hannah. “Bone Marrow: Function, Diseases, Transplants, and Donation.” Medical News Today, MediLexicon International, 15 Dec. 2017. Available here  

Image Courtesy:

1.”619 Red and Yellow Bone Marrow”By OpenStax College – Anatomy & Physiology, Connexions Web site. Jun 19, 2013., (CC BY 3.0) via Commons Wikimedia  
2.”603 Anatomy of Long Bone”By OpenStax College – Anatomy & Physiology, Connexions Web site.  Jun 19, 2013., (CC BY 3.0) via Commons Wikimedia