If you’ve ever wondered whether snakes have hearts, you’re not alone. Snakes are fascinating yet mysterious creatures, and their anatomy can seem perplexing compared to mammals. Keep reading to learn everything you need to know about snake hearts and circulatory systems.
If you’re short on time, here’s a quick answer to your question: Yes, snakes do have hearts. A snake’s heart is quite different from a human heart, but it serves the same vital purpose of circulating blood and oxygen throughout the snake’s body.
The Basic Structure and Function of a Snake Heart
Single Ventricle Heart
Most snakes have a three-chambered heart consisting of two atria and one ventricle, referred to as a “single ventricle heart.” This means oxygenated and deoxygenated blood mix together before being pumped to the lungs and body.
Having just one ventricle allows snakes to attain smaller heart sizes to fit their elongate bodies.
Three Chambered Heart
While over 2,700 snake species have single ventricle hearts, a few exceptions like pythons and boas possess three-chambered hearts, containing two atria and two ventricles. Their hearts separate oxygenated and deoxygenated blood, being more similar to mammalian hearts.
But their ventricles remain partly mixed. This likely provides more efficient circulation for their larger bodies.
How a Snake Heart Works
A snake’s heart functions by utilizing muscular contractions to pump blood:
Interestingly, a snake’s heart grows as the snake grows longer. A 1-foot garter snake heart may be just a few millimeters, while 10+ foot python hearts can be bigger than a human fist! Their sizable hearts circulate blood throughout lengthy vascular networks, supplying oxygen and nutrients to distant tissues.
| Heart Type | Structure | Blood Flow |
|---|---|---|
| Single ventricle heart | 2 atria, 1 ventricle | Mixed oxygenated and deoxygenated blood |
| Three chambered heart | 2 atria, 2 ventricles | Partly separated oxygenated and deoxygenated blood |
To learn more about snake cardiovascular systems, check out this authoritative snake anatomy overview.
Key Differences Between Snake Hearts and Mammal Hearts
Cold-Blooded Circulatory System
One of the biggest differences between snake hearts and mammal hearts relates to body temperature regulation. Mammals like humans are warm-blooded, meaning they maintain a consistent internal body temperature.
Snakes, however, are cold-blooded animals, so their body temperature varies based on external temperatures.
Because they are cold-blooded, a snake’s circulatory system works differently than a mammal’s. A snake’s heart only has to pump blood a short distance to capillaries to exchange oxygen and carbon dioxide before returning to the heart. Mammals rely on their circulatory system to disperse heat throughout the body in addition to exchanging gases.
Lower Blood Pressure
Another key difference is that snakes have lower blood pressure than mammals. The average blood pressure for a snake is around 10/5 mmHg compared to 120/80 mmHg for an average human.
Lower blood pressure is possible in snakes because their blood doesn’t have to circulate as far as in tall mammals. Their hearts beat at a slower rate with less pressure to pump blood through shorter distances.
Slower Heart Rate
Speaking of heart rate, a snake’s heart beat significantly slower than a mammal’s. The average heart rate for a snake is around 60-90 beats per minute, while the average for humans is 60-100. However, a snake’s heart can slow down to just a few beats per minute when resting.
Their slower heart rate works in line with their cold-blooded metabolism. With slower internal processes, their circulatory system can pump at a more relaxed pace.
The Role of the Heart in a Snake’s Circulatory System
Arterial and Venous Systems
Snakes have a closed circulatory system with both arterial and venous systems that transports blood throughout their bodies. The arterial system carries oxygenated blood from the heart to tissues, while the venous system returns deoxygenated blood to the heart (Source).
The snake heart has two ventricles and two atriums to keep these systems separated.
Systemic and Pulmonary Circulation
There are two circuits in a snake’s circulatory system: systemic circulation and pulmonary circulation.
Systemic circulation transports oxygenated blood from the heart to tissues in the rest of the body before returning deoxygenated blood back to the heart. The pulmonary circuit takes deoxygenated blood from the heart to the lungs, oxygenates it, and returns oxygenated blood back to the heart to pump through the body again (Source).
Oxygenation and Blood Flow
A snake’s heart pumps blood in one direction: from the atriums to the ventricles and then out to the body or lungs through arteries.
The right atrium receives deoxygenated blood from the body through veins. This flows to the right ventricle, which pumps it to the lungs through the pulmonary artery. In the lungs, the blood loads up on oxygen.
The oxygenated blood then flows back through the pulmonary vein to the left atrium. From there, the left ventricle pumps the blood out through aortic arteries to oxygenate tissues throughout the body. The cycle then repeats.
| Heart rate range for snakes | 30 – 180 beats per minute |
| Blood flow rate | 9 cm/s |
This system allows for efficient oxygen delivery to power a snake’s cells and remove waste (Source) 🐍.
Unique Adaptations in Some Snake Species
Venomous Snakes
Venomous snakes have evolved specialized fangs and venom glands to subdue prey and deter predators. Some remarkable adaptations in venomous snakes include:
- Hinged hollow fangs that can be folded back when not in use – found in vipers and elapids.
- Rotationally versatile maxillae bones that allow vipers to orient their fangs forward for a quick strike – unique among snakes.
- Highly toxic neurotoxic or hemotoxic venom containing a complex cocktail of proteins and enzymes – allows rapid subjugation of prey.
- Heat-sensing pit organs that help vipers accurately strike at warm-blooded prey – the iconic “pit viper” trait.
- Rattles on rattlesnakes that serve as a warning to deter large animals from accidentally stepping on the snake.
These adaptations make venomous snakes extremely effective predators. However, venom research has also led to medical advances, with some snake venoms containing compounds that can treat heart conditions or pain (National Geographic).
Sea Snakes
Sea snakes exhibit incredible adaptations that allow them to thrive in marine environments, including:
- Flattened paddle-shaped tails that propel them effortlessly through the water.
- Valves in their nostrils and mouths that keep out saltwater while diving.
- Ability to excrete excess salt from a specialised gland under their tongue.
- Increased lung capacity and cutaneous respiration that allows extended underwater stays.
- Giving live birth to young rather than laying eggs – protects the eggs from marine predators.
These modifications make sea snakes only truly marine reptiles. They can spend hours underwater hunting fish and are found throughout tropical Indo-Pacific oceans (LiveScience).
Sidewinders
Sidewinders are a type of rattlesnake found in deserts of the southwestern United States. They have unique adaptations for dealing with scorching sand, including:
- Specialised scales on their belly that provide traction to prevent sinking into loose sand.
- Sideways looping locomotion that keeps contact with hot ground to a minimum.
- Increased thermal tolerance and ability to burrow underground to avoid extreme desert heat.
- Nocturnal habits and infrared-sensing pit organs to hunt rodents at night.
- Horned scales above their eyes that help shade their eyes from the sun.
These traits allow sidewinders to thrive in environments where most snakes cannot. Their unique movement even inspired early robotics designs for navigating sand (National Geographic).
Evolution of Snake Hearts and Circulation
The cardiovascular system of snakes has evolved over millions of years to meet the unique demands of their elongated bodies and underground lifestyles. Let’s explore some of the key adaptations of the snake heart and circulatory system.
Transition to Three Chambered Heart
While primitive snakes had four-chambered hearts like other reptiles, most modern snakes have transitioned to a three-chambered heart. This consists of two atria and one ventricle, which allows blood to mix to some degree.
This adaption allows snakes to maximize oxygenation when oxygen levels are low, such as during hibernation or while constricting prey.
Development of Venom
Venomous snakes have further adapted their cardiovascular system to accommodate the production and delivery of venom. Their hearts have developed thicker muscular walls to handle the demands of circulating venom.
Some snakes like cobras have also evolved a specialized venom delivery system using enlarged fangs connected to venom glands.
Adaptations for Habitat
A snake’s habitat has driven other circulatory adaptations. Aquatic snakes like sea snakes have capillaries concentrated near their lungs to facilitate oxygen exchange in water. Fossorial snakes that burrow underground tend to have lower blood pressure and heart rates to conserve oxygen in their sealed burrows.
Arboreal tree snakes have higher blood pressure to pump blood against gravity when climbing tall trees.
Conclusion
While a snake’s cardiovascular system is very different from a human’s, it is just as perfectly adapted to serve the snake’s needs. A heart is absolutely vital for circulating blood and oxygen to power all of a snake’s movements and activities.
Snakes have undergone remarkable evolutionary adaptations related to their hearts and circulation. Understanding the form and function of snake hearts provides fascinating insight into snake anatomy and physiology.
