Snakes are fascinating creatures that have captured people’s imaginations for centuries. Their elongated bodies allow them to slither and coil with ease, and their forked tongues provide an extra sensory advantage. But have you ever wondered what the inside of a snake looks like?

In this comprehensive article, we will explore the anatomy and physiology inside a snake’s long torso.

If you’re short on time, here’s a quick answer: A snake’s internal organs include its heart, lungs, stomach, gallbladder, pancreas, intestines, cloaca, and gonads. Key features are its expandable jaw for swallowing prey whole, venom glands in some species for capturing food, Jacobson’s organ for detecting chemicals, and a forked tongue for picking up scent particles.

We will examine a snake’s digestive, respiratory, circulatory, nervous, and reproductive systems. You’ll learn about unique adaptations like venom glands, heat-sensing pits, and a flexible spine. Read on for an in-depth tour of the inner workings of these legless reptiles!

Mouth and Throat

Jaws and Teeth

Snakes have a very flexible lower jaw that allows them to swallow prey much larger than their head. The jaws contain backwards-curving teeth that help grip and swallow food. Snakes do not have a uvula, the piece of flesh that hangs down in the back of the throat.

Their mouth and throat are one continuous chamber, allowing them to swallow large items whole.

Forked Tongue

One of the most distinctive features of snakes is their forked tongue. The tongue has two tips which collect chemical information from the environment. As the tongue moves in and out, it transfers these molecules to the Jacobson’s organ in the roof of the mouth.

This organ analyzes the chemicals so the snake can detect prey, predators, and mates.

Salivary Glands

Snakes have two types of salivary glands – the upper and lower glands. The upper glands produce a watery, protein-rich secretion to help lubricate food for swallowing. The lower glands make venom in venomous species.

Venom is modified saliva that contains neurotoxins and other compounds to immobilize prey. While swallowed prey may still bite from inside, venom allows snakes to start digesting before swallowing.

Digestive System


The esophagus is a muscular tube connecting the mouth to the stomach that is around 25 centimeters long in most adult snakes. It passes food from the mouth down to the stomach by peristaltic contractions of its muscular wall. The inner lining of the esophagus is moist to help the passage of food.

At the lower end of the esophagus is a specialized sphincter muscle called the cardiac sphincter that controls the entrance into the stomach.


The stomach is a widened area of the digestive tract where initial digestion of food takes place. It is separated from the esophagus by the cardiac sphincter. The stomach produces strong acids and enzymes that start breaking down proteins and fats in the swallowed food.

The contractions of the stomach help to churn and mix the food with the digestive juices. At the lower end of the stomach is the pyloric sphincter which controls the passage of partly digested food into the small intestine.


The liver is a large glandular organ that produces bile, stores glycogen, detoxifies chemicals, and has many other important functions. The bile produced in the liver is transported via ducts into the small intestine, where it emulsifies fats to aid in their digestion and absorption.

The liver also helps metabolize proteins, carbohydrates, fats, and vitamins absorbed from the small intestine.


The pancreas is an elongated gland located near the stomach that produces pancreatic juice containing digestive enzymes that help breakdown food. The pancreatic juice is delivered into the small intestine via ducts.

It contains enzymes like amylase to digest carbohydrates, lipase to digest fats, and trypsin/chymotrypsin to digest proteins. The pancreas is therefore crucial for the proper digestion and absorption of nutrients.


The small intestine is where most chemical digestion and absorption of nutrients occurs. It is much longer than the large intestine, reaching over 20 feet in large snakes! The small intestinal lining has microscopic folds to increase surface area for nutrient absorption.

Here, enzymes from the pancreas and bile from the liver continue breaking down and emulsifying food. The intestinal walls contain blood and lymph vessels that transport absorbed nutrients to body tissues.

The undigested food then passes into the shorter large intestine and waste is stored in the cloaca.


The cloaca is the end of the digestive tract that serves as an exit for wastes and reproduction. It connects the large intestine with the openings for urinary and reproductive ducts. Solid wastes like feces are stored here until they can be eliminated from the body, while urine, reproductive fluids, and eggs may also pass through the cloaca.

The cloaca empties to the outside through the vent.

Circulatory System


A snake’s circulatory system is closed, meaning the blood is contained within vessels and does not come into direct contact with body tissues. The heart is located in the upper third of the body, just behind and below the head. It has three chambers – two atria and one ventricle.

The right atrium receives blood from the body while the left atrium receives blood from the lungs. Both atria empty into the single muscular ventricle, which pumps blood into the arteries.

Some key facts about a snake’s heart and circulatory system:

  • The heart beats between 60-90 times per minute on average.
  • Heart rate can increase to up to 200 beats per minute after activity or while digesting a large meal.
  • Blood pressure is generally low compared to mammals.
  • Valves in the heart prevent backflow of blood.
  • Contractions of muscles surrounding blood vessels help move blood through the snake’s body.

The powerful ventricular contractions produce pressure that pumps blood through the circulatory system. The lower blood pressure compared to mammals reduces stress on vessel walls.

Blood Vessels

Arteries carry blood away from the heart while veins return blood back to the heart. The main artery, called the dorsal aorta, runs down the length of the body above the backbone. Smaller branch arteries deliver blood to body organs.

Venous blood from the head area flows into two jugular veins that parallel the trachea on either side and connect to the right atrium.

Key facts about a snake’s blood vessels:

  • Arteries have thicker, more elastic walls than veins to withstand pressure.
  • Valves in veins prevent backflow of blood.
  • Vessels called sinuses allow pooling of blood for erection of hemipenes in males.
  • Venous blood flow relies on muscle contraction and valves, without assistance from respiration.

The branching network of smaller arteries and veins distributes blood throughout the snake’s elongated body. Valves prevent blood from flowing backward and enable one-way circulation.

Respiratory System


The trachea, also known as the windpipe, is a tube that connects the throat to the lungs and allows snakes to breathe air. It is lined with rigid rings of cartilage which prevent it from collapsing and keep it open.

The trachea runs along the neck and into the chest cavity where it splits into two branches called the primary bronchi that carry air to the right and left lungs.

When a snake inhales, air travels down the trachea and into the lungs, providing oxygen for gas exchange. As the snake exhales, carbon dioxide and other waste gases exit through the trachea. The rings of cartilage allow the trachea to flex and bend while maintaining its patency.

This is important as snakes often contort their bodies into tight spaces where the trachea needs to bend without obstructing airflow.

Some interesting facts about snake tracheas:

  • The tracheal rings are incomplete in the front to allow the esophagus to pass through.
  • Aquatic snakes like sea snakes have a trachea that can completely collapse when diving to prevent water from entering the lungs.
  • Large snakes like anacondas and pythons have an extraordinarily stretchable trachea to accommodate swallowing large prey items.


Snakes have two relatively simple sac-like lungs that are well adapted to their elongated body shape. The lungs extend almost the full length of the snake’s body cavity with the left lung being slightly shorter than the right.

This linear design provides sufficient surface area for gas exchange while avoiding the complexity of multilobed lungs found in mammals.

The outer surface of snake lungs is smooth, lacking the lobules and bronchioles found in mammalian lungs. Air flows through the trachea into the simple lung sacs which inflate like balloons. The insides of the lungs contain a spongy, vascularized tissue rich in capillaries which facilitates gas exchange between the air and bloodstream.

Being ectothermic, snakes do not require as much lung capacity and ventilation as birds and mammals. Their metabolic rates are lower, thus reducing oxygen demand. However, the linear shape and flexibility of snake lungs allow for adequate oxygenation given their tubular bodies and unique breathing mechanisms.

Here are some fascinating tidbits about snake lungs:

  • Aquatic snakes like sea snakes have lungs adapted for deep diving with more vascularization and greater oxygen storage.
  • The right lung is often larger since the left side of the body contains the enlarged heart and liver.
  • Snakes can perform something called “unidirectional ventilation” where air flows in through the trachea but out through the esophagus.

Excretory System


The kidneys are a pair of bean-shaped organs located in the lower back of snakes. They play a crucial role in the excretory system by filtering metabolic waste products and excess water from the blood. Here’s a closer look at how snake kidneys function:

  • Each kidney contains thousands of tiny filtering units called nephrons. As blood flows through the nephrons, metabolic wastes like urea and uric acid are filtered out and sent to the bladder as urine.
  • Snakes produce uric acid as their primary nitrogenous waste product instead of urea like mammals. This allows them to conserve water more efficiently.
  • The filtrate produced by the nephrons also contains vital nutrients like glucose, amino acids, vitamins and minerals. These get reabsorbed back into the bloodstream as the urine passes through each nephron.
  • Snake kidneys lack a cortex and medulla. They consist mainly of closely packed nephrons without distinct regions.
  • Some sea snakes have special salt-excreting glands near their kidneys to get rid of excess sodium chloride.


The urinary bladder is a thin-walled muscular sac that stores urine prior to elimination. Here are some key facts about the bladder in snakes:

  • The bladder receives urine from the kidneys through a pair of ureters.
  • It has elastic walls that can expand to accommodate large volumes of urine. Some snakes like pythons can store up to a quarter of their body weight in urine!
  • Powerful circular muscles called sphincters control the exit of urine from the bladder.
  • In males, the bladder connects to the cloaca – an opening used for urination, defecation and reproduction.
  • In females, the bladder has separate openings for urination (urodeum) and reproduction (cloaca).
  • When empty, the snake bladder shrinks down to a small size against the backbone.

Reproductive System


The testes of male snakes produce sperm that is stored in the epididymis until mating. The paired testes are located in the lower abdomen near the kidney region. Unlike mammals, snake testes are not contained in a scrotum outside the body wall.

Keeping the testes inside the body cavity allows snakes to conserve heat more efficiently.


The ovaries of female snakes produce eggs that pass into the oviducts. Snakes have paired ovaries located similarly to the testes, in the lower abdomen by the kidneys. Some snake species, like boas and pythons, contain vestigial pelvic spurs on each side of their cloacal vent, which are physical remnants of the legs their ancestors once possessed.


Male snakes and other squamates contain paired copulatory organs called hemipenes. The hemipenes are normally held inverted within the snake’s tail and will evert during mating to transfer sperm. Having two intromittent organs allows more efficient mating and sperm transfer – handy during snake orgies where multiple partners are involved!


The vagina in female snakes connects internally from the cloaca to the oviducts and uterus for mating and egg fertilization. Unlike with hemipenes though, the vagina is not everted outside of the cloaca.

Fun fact – some female snake species can reproduce through parthenogenesis, so they don’t require a male partner to activate their eggs!

Structure Male Female
Gonads Testes Ovaries
Gametes Sperm Eggs
Copulatory organ Hemipenes Vagina

Nervous System

The nervous system of a snake plays a crucial role in controlling all of the snake’s bodily functions and behaviors. The two main components of a snake’s nervous system are the brain and spinal cord, which work together to process sensory information and coordinate the snake’s movements.


A snake’s brain is relatively small but efficient. Located in the head region, the snake brain is made up of several interconnected structures that regulate key functions. For instance, the forebrain contains the olfactory lobes for processing smells detected by the snake’s forked tongue, allowing them to detect prey or predators.

The midbrain integrates visual inputs from the eyes to facilitate hunting and navigating terrain. Finally, the hindbrain controls essential involuntary functions like respiration, circulation, and digestion.

Spinal Cord

Extending from the brain down the length of its body is a snake’s spinal cord. This structure relays nerve signals between the brain and the rest of the snake’s anatomy. Sensory neurons bring information gathered by specialized nerve endings in the skin into the spinal cord, sending data about temperature, touch, and pain upstream to the brain.

Motor neurons then carry instructions from the brain back to the muscles, initiating movements like slithering, coiling, and striking.

Sensory Organs

To fully monitor their environment, snakes rely heavily on two paired sensory organs – their eyes and tongues. A snake’s eyes have decent visual acuity and color detection capacities. However, they primarily depend on their forked tongues, which collect chemical particles from the air and ground.

By inserting the tips of their tongues into an organ in the roof of their mouth called the Jacobson’s organ, snakes essentially “smell” these molecules, allowing them to track prey movement and identify predators or mates. This creates a 3D sensory image of their surroundings. Pretty amazing!

Altogether, the nervous system provides snakes with the speed, reflexes, and sensory capabilities that makes them such effective hunters and survivalists in the wild. Their streamlined brains may be drastically different from our own, but they’re perfectly adapted to meet the unique demands of a snake’s long, legless body.


We hope this comprehensive tour through a snake’s anatomy was enlightening! Snakes have evolved amazing internal structures and systems to suit their elongated shape and carnivorous diet. Key highlights include expandable jaws, advanced chemical receptors, and flexible backbone – all important adaptations for their survival.

While the inner workings of snakes may seem alien compared to other animals, they have all the major organ systems needed to see, digest food, circulate blood, breathe, and reproduce. Understanding the form and function inside these legless reptiles gives us appreciation for how they thrive in habitats around the world.

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