The key difference between blood and hemolymph is that blood contains red blood cells, and it transports oxygen while hemolymph does not contain red blood cells and is not involved in oxygen transport.
Blood and hemolymph are two different types of circulating fluids found in organisms. Blood is the fluid circulating in vertebrates while hemolymph is the fluid circulating in most invertebrates. Hemolymph is analogous to blood in vertebrates. Both blood and hemolymph distribute nutrients and hormones throughout the body. Blood flows inside blood vessels while hemolymph flows in an open space or is present in a body cavity called haemocoel. Blood consists of red blood cells or erythrocytes which transport oxygen. However, hemolymph does not contain red blood cells. Moreover, unlike blood, hemolymph contains a high concentration of free amino acids.
CONTENTS
1. Overview and Key Difference
2. What is Blood
3. What is Hemolymph
4. Similarities Between Blood and Hemolymph
5. Side by Side Comparison – Blood vs Hemolymph in Tabular Form
6. Summary
What is Blood?
Blood is the fluid that circulates in the vertebrate body via blood vessels. It delivers oxygen and nutrition to body parts. It transports waste of metabolic processes away from the cells and tissues. There are several types of blood cells suspended in blood plasma. Therefore, blood contains red blood cells, white blood cells, platelets and blood plasma.
From the total volume of blood, red blood cells account for 45% while the plasma account for about 54.3% and white cells content is about 0.7%. It also has glucose and other dissolved nutrients. The average density of blood is around 1060 kg/m3. Moreover, blood has coagulation factors or elements. The pH of the normal blood is around 7.2. An average person has 5 litres of blood.
What is Hemolymph?
Hemolymph is the fluid that is analogous to the blood in vertebrates. It is the fluid that fills the haemocoel of most invertebrates. Haemocoel is a body cavity. Hence, it is an open circulatory system. Unlike blood, hemolymph does not contain red blood cells and haemoglobin. Hence, it is not used to transport oxygen. But in certain species, hemolymph plays some role in respiration.
The main component of hemolymph is water. It also contains ions, carbohydrates, lipids, amino acids, hormones, some cells (hemocytes) and pigments. Hemolymph contains a high concentration of free amino acids. It is a colourless fluid and passes more or less freely throughout the tissues. Hence, hemolymph is in direct contact with animal tissues all the time. Hemolymph works as a water storage pool as well. Furthermore, it plays important roles in the immune system and in the transport of hormones, nutrients, and metabolites in invertebrates.
What are the Similarities Between Blood and Hemolymph?
- Hemolymph is a fluid that is analogous to the blood in vertebrates.
- Both fluids distribute nutrients and hormones.
- They also help in removing waste.
What is the Difference Between Blood and Hemolymph?
Blood is a fluid that circulates throughout the body inside the circulatory system, while hemolymph is the fluid analogous to blood and fills the haemocoel of invertebrates. Blood contains red blood cells, while hemolymph does not contain red blood cells. So, this is the key difference between blood and hemolymph. Plasma and different cells and cell fragments called platelets are the major components of blood while water, ions, carbohydrates, lipids, amino acids, hormones, some cells (hemocytes) and pigments are the components of hemolymph. Moreover, blood has haemoglobin, and it transports oxygen while hemolymph does not contain haemoglobin and does not transport oxygen.
The below infographic tabulates more differences between blood and hemolymph.
Summary – Blood vs Hemolymph
Blood and hemolymph are two types of fluids circulating the body. In vertebrates, blood is the fluid that transports oxygen, carbon dioxide, nutrients and hormones throughout the body. In most invertebrates, hemolymph is the circulating fluid that is analogous to blood. However, unlike blood, hemolymph does not contain red blood cells and haemoglobin. It circulates within an open circulatory system, which is a body cavity called haemocoel. Moreover, unlike blood, hemolymph is in direct contact with animal tissues. Thus, this summarizes the difference between blood and hemolymph.
Reference:
1. “Components of the Blood.” Components of the Blood | OpenStax Biology 2e, 7 Mar. 2018, Available here.
2. “Hemolymph.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., Available here.
Image Courtesy:
1. “Human Heart and Circulatory System” By Bryan Brandenburg – (CC BY-SA 3.0) via Commons Wikimedia
2. “Open Circulatroy” By Mdunton16 – Own work (CC BY-SA 4.0) via Commons Wikimedia