Have you ever climbed up to a higher elevation and found it a bit harder to breathe?
Humans are made to live at sea-level where the air pressure allows you to breathe in oxygen efficiently (essentially 100% of the oxygen in the air is available to you). At higher elevations, the oxygen is more spread out, making it difficult for your body to breathe in enough oxygen with each breath. Humans begin to experience “mountain sickness,” characterized by dizziness, nausea, fatigue and shortness of breath, at about 1,500 meters (4,900 ft) above sea-level.
Llamas, and their relatives, regularly hang out at altitudes of 7,400-12,800. This means their bodies are equipped to deal with extremely low available oxygen levels in the air. Differences in their red blood cells (RBCs), among other adaptations, help them survive in the mountains.
How do red blood cells work?
RBCs (also called erythrocytes) are essential components in your blood – actually in all vertebrate’s blood. They make up almost half of your blood volume (40-45%) and a quarter of all the cells in your body. RBCs pick up oxygen in the lungs (or gills if you are a fish) and deliver it to the tissues in your body. On the return trip to the lungs, they carry waste products like carbon dioxide.
They can do this because they contain hemoglobin, a protein that also contains iron. Iron likes oxygen and the oxygen diffuses into the RBC and sticks to the iron. Each hemoglobin protein can bind four oxygen molecules. As the RBCs are pumped throughout your vessels (thank you heart), the oxygen diffuses back out of the cell in tissues where oxygen concentrations are low. Human RBCs saturate easily with oxygen at sea level. FYI- the iron in hemoglobin is why your blood is red.
Human RBCs are abnormally shaped, which makes them highly recognizable. They are flatter than most cells and are concave, with a dimple in the middle. This shape allows them to squeeze through capillaries to deliver oxygen.
How do llamas survive?
Llama blood is specially adapted to higher elevations.
First, their blood has a higher percentage of RBCs when compared to animals that live at lower altitudes. This lets the blood carry more oxygen overall.
Second, llama RBCs are more efficient at distributing oxygen throughout the body, due to their ability to bind oxygen. For example, at lower pressures, llama RBCs bind more oxygen. This is illustrated in the following graph that shows percent of oxygen in the blood at different pressures of oxygen (different altitudes) :
In addition to binding oxygen easier, llama RBCs release oxygen more readily when they get to tissues.
Further, unlike human RBCs, llama RBCs are small and oval shaped, which also allows them to take in more oxygen. All together, these properties of llama RBCs make an extremely efficient oxygen extraction and delivery system.
All these changes to RBCs have a down side: llama blood is thicker than other blood and it is harder to push around the body. Their bodies have more work to do to circulate their blood. To compensate for this, llamas have a faster heart rate and a higher blood pressure. In addition, while they can live at both low and high elevations, their bodies work more efficiently higher up. When we bring them down to our level, we run the risk of decreasing their life span.
Fortunately, I think we make up for it with our tender lloving care.
Blogging my way from A to Z as part of the 2016 April A to Z Challenge! My theme for this year: Llama mama. R for Red Blood Cells.
Photo courtesy of Ryan Somma.