If you’ve ever wondered whether snakes have blood flowing through their veins, you’re not alone. Snakes are strange and mysterious creatures to many people. Their legless bodies and ability to unhinge their jaws to swallow prey whole can be unsettling.
If you’re short on time, here’s a quick answer to your question: Yes, snakes do have blood. Like all vertebrates, snakes have a complex circulatory system that pumps blood throughout their bodies.
In this detailed article, we’ll take a close look at snakes’ anatomy to understand their circulatory system and blood. We’ll examine how their blood and circulatory system are adapted for their unique physiology as reptiles.
Read on to learn more about the blood that flows through these fascinating creatures!
Snakes Have Closed Circulatory Systems Like Other Vertebrates
Like humans and other vertebrates, snakes have a closed circulatory system.
Snakes, like humans and all other vertebrates, have a closed circulatory system (also called a cardiovascular system). This means the heart pumps blood through a network of blood vessels that form a closed loop throughout the body.
The blood flows through arteries and capillaries, delivering oxygen and nutrients to tissues and organs, before returning to the heart through veins. Unlike some invertebrates such as insects, the snake’s circulatory system is sealed and the blood remains inside the system, having no direct contact with bodily tissues.
Their circulatory system is made up of a heart, blood vessels, and blood.
The main components of a snake’s circulatory system are:
- Heart – Snakes have a three-chambered heart with two atria and one ventricle. The heart pumps blood throughout the circulatory system.
- Blood vessels – Arteries carry oxygenated blood away from the heart to the body, while veins return deoxygenated blood back to the heart. Capillaries are small vessels that facilitate gas and nutrient exchange.
- Blood – Snake blood is generally red, owing to the presence of hemoglobin, which carries oxygen. Blood also contains white blood cells, platelets, and other components.
Having a closed circulatory system with a dedicated heart and network of blood vessels allows snakes to efficiently deliver oxygen and nutrients to tissues and remove waste products. This enables their active, predatory lifestyles.
Oxygenated and deoxygenated blood flow separately in the circulatory system.
Snakes, like us, have pulmonary circulation and systemic circulation that keeps oxygenated and deoxygenated blood separate. This allows for optimal gas exchange.
- Pulmonary circulation – Deoxygenated blood returns from the body to the heart, where it is pumped to the lungs to become oxygenated. Oxygenated blood then flows back to the heart.
- Systemic circulation – Oxygenated blood is pumped from the heart to the muscles and organs of the body through arteries. As oxygen is delivered, the blood becomes deoxygenated and returns to the heart through veins.
This dual circulation allows the heart to pump oxygen-rich blood to where it is needed, while keeping waste-filled blood isolated for filtering by the lungs. The separation maximizes oxygen delivery for energy production.
Snake Blood Has Unique Adaptations for Reptile Physiology
Snake blood contains nucleated red blood cells unlike mammalian blood.
One of the most striking differences between snake blood and the blood of mammals like humans is the presence of nucleated red blood cells (RBCs). In humans, RBCs lack a nucleus and are biconcave discs optimized for transporting oxygen.
Snake RBCs contain a nucleus like white blood cells and are elliptical in shape, which reduces their flexibility.
It was long thought that nucleated RBCs were a more primitive trait, but they offer advantages for reptiles. The nucleus allows production of RNA and proteins that support metabolism. Snake RBCs also live much longer than mammalian RBCs, with lifespans of up to 600 days compared to 120 days in humans.
The blood is colder than human blood since snakes are cold-blooded.
One of the defining features of snakes as reptiles is that they are cold-blooded or ectothermic. This means a snake’s body temperature matches its environment, unlike warm-blooded mammals that maintain a constant internal temperature.
Consequently, a snake’s blood is cooler than a human’s resting 98.6°F body temperature. A snake’s blood may be as low as 60°F or up to 20°F higher after basking to absorb heat. The viscosity and delivery of oxygen is affected by colder blood, hence snakes move and digest food much slower than mammals.
Clotting factors allow snakes’ blood to coagulate quickly.
An important adaptation in snakes is their blood’s ability to coagulate rapidly compared to human blood. While humans takes 2-6 minutes to begin clotting, snake blood can start clotting within seconds.
This rapid coagulation prevents blood loss in the event of injury, which is especially crucial for snakes as they lack the ability to actively apply pressure on wounds. The quick clotting is due to higher levels of clotting factors like fibrinogen and thrombin in snake blood.
How Snake Hearts Pump Blood Through the Circulatory System
Snakes have a three-chambered heart with two atria and one ventricle.
Unlike the four-chambered hearts of mammals and birds, snakes and other reptiles have a three-chambered heart consisting of two atria and one ventricle. The right atrium receives deoxygenated blood from the body while the left atrium receives oxygenated blood from the lungs.
Both atria empty into the single ventricle which pumps blood into the circulatory system.
The heart circulates blood from the lungs and body separately.
Although snakes have a single ventricle, their circulatory system keeps oxygenated and deoxygenated blood separate. When the ventricle contracts, it pushes deoxygenated blood toward the lungs and oxygenated blood back to the body due to specialized adaptations:
- The ventricle wall has ridges that direct blood to different areas.
- Valves within the ventricle ensure blood flows in the proper direction.
- Venous and arterial blood remains isolated.
This separation allows adequate oxygenation despite having a three-chambered heart.
Valves in the heart prevent mixing of oxygenated and deoxygenated blood.
Snakes have two main valves within the heart that prevent mixing of oxygenated and deoxygenated blood:
- The sinus venosus valve separates the right and left atrium.
- The spiral valve divides the ventricle itself into two channels.
Together, these valves force blood to flow in the proper direction. When the ventricle contracts, the blood is pushed either toward the lungs or body, ensuring oxygen-rich and oxygen-poor blood do not mix. This allows snakes to sufficiently oxygenate tissues with just one ventricle.
Unique Adaptations in Snakes’ Blood Vessels
Arteries carry oxygenated blood, veins carry deoxygenated blood.
Like all vertebrates, snakes have a closed circulatory system with arteries that carry oxygenated blood from the heart to tissues, and veins that return deoxygenated blood back to the heart and lungs. But snakes have evolved unique adaptations related to their blood vessels.
For example, snakes have higher blood pressures than mammals, averaging 30-40 mm Hg systolic arterial pressure compared to 120 mm Hg for humans. This allows their blood to continue flowing even when their peripheral blood vessels are constricted during periods of stress or digestion (Mackessy, 2017).
Snakes have abdominal veins to cool blood going to the stomach after eating.
One unique adaptation is the abdominal vein found along the ventral midline of snakes. This vein is thought to provide a route for blood returning from the snake’s stomach to be cooled as it passes close to the surface before being recirculated back to the heart (O’Shea, 2022).
This helps prevent overheating of internal organs during digestion. After consuming large prey relative to their body size, a tremendous amount of blood flow is shunted to the stomach and small intestine to aid in digestion and absorption of nutrients.
Cooling this blood before it returns to the heart likely prevents organ damage from getting too hot.
Portal veins carry blood between digestive organs and the liver.
The portal vein system in snakes includes veins draining from the stomach and intestines into the liver. From the liver, blood continues back to the heart in the hepatic veins. This portal circulation allows absorbed nutrients to be processed by the liver before the blood circulates systemically (Secor, 2022).
Interestingly, specialized sphincter valves in the portal veins help partition blood flow between the snake’s left and right liver lobes after feeding. This allows each liver lobe to specialize in different functions – the right lobe focuses more on bile production to aid digestion, while the left lobe synthesizes serum proteins (Cox, 2021).
Importance of Circulatory System for Snakes’ Survival
Circulatory system delivers oxygen and nutrients to snake’s tissues.
The circulatory system of snakes plays a vital role in transporting oxygen and nutrients throughout their body to sustain life (Reptiles Magazine). Oxygen attaches to the hemoglobin proteins in a snake’s red blood cells and is circulated to tissues and organs via arteries and capillaries.
Nutrients absorbed from the digestive system are also transported in the blood plasma to supply cells and enable functions like muscle contraction.
Without an efficient circulatory system to disperse oxygen and nutrients, a snake’s organs and tissues would fail to receive the essential components they need to operate. Nerve impulses, muscle contractions, cell growth and repair, and other metabolic processes rely on these deliveries through the cardiovascular network.
Removes waste like carbon dioxide and lactic acid from muscles.
In addition to deliveries, a core job of the circulatory system is waste removal. As snakes perform strenuous activity, their muscles build up lactic acid, which causes fatigue and soreness. Their blood collects this waste and transports it to the liver for detoxification before the blood re-circulates.
Carbon dioxide is another toxic waste produced through cell respiration that must be cleared. Snakes frequently hold their breath while hunting and constricting prey. Without an effective circulatory system to carry away carbon dioxide, it would accumulate to dangerous levels in tissues and blood over time.
Helps regulate body temperature of cold-blooded snakes.
One unique aspect of a snake’s circulatory system is that it aids thermoregulation. Since snakes are ectothermic or “cold-blooded,” they rely on external heat sources to reach optimal body temperatures.
When ambient temperatures rise, snakes can circulate more blood near the skin, releasing heat through the scales to prevent overheating. Likewise, less blood flows near the surface in cold conditions to conserve heat.
According to research, the circulatory system enables precise control over body temperature in snakes, maintaining it within a narrow optimal range for metabolism and function (Dmi’el 1972). Without these intricate adjustments, snakes would be susceptible to freezing or overheating depending on environmental conditions.
Conclusion
Snakes may appear alien to us with their legless, scaly bodies, but a peek inside reveals they share much in common with other vertebrates. Like all animals with backbones, snakes have a sophisticated circulatory system to pump blood throughout their bodies.
While snake blood has some unique adaptations for their physiology, its vital function remains the same. The blood delivers oxygen and nutrients while ferrying away waste to support the snake’s cells. Without a functioning circulatory system pumping blood, snakes would quickly die.
The next time you see a snake slither by, remember the network of blood vessels and pumping heart that keeps its strange body alive. Learning about snakes’ anatomy can make them less mysteriously frightening and help us appreciate the biodiversity of life on Earth.
