Blood travels towards the heart through these.

This major passageway for air between your lungs and mouth/nose contains strong rings of cartilage for support and strength.

The mechanical breakdown of food begins here.

Capillaries are in this system.

This is the main muscle that controls breathing.

This chamber of the heart has the most muscle surrounding it.

The left and right bronchus each branch off into these smaller passageways for air to travel.

This is the name we give to the entire passageway through which food travels from when it first enters our body to when it leaves.

The larynx is in this system.

These structures are embedded in the circulatory system to prevent blood from flowing in the opposite direction.

A deoxygenated red blood cell returning to the heart from the lower body enters through this blood vessel.

When you swallow, this flap reflexively closes off your airways so that food or liquid do not enter.

This enzyme produced by the liver helps to chemically break down fats.

The gall bladder is in this system.

This is about the number of red blood cells in one drop of blood.

These two blood vessels are known as the "Great Arteries".

These tiny sacs are covered in capillaries and deliver oxygen to the bloodstream and remove carbon dioxide from it.

These fingerlike projections in the small intestine contain capillaries and is where nutrients from digested food is absorbed into the bloodstream.

Skin is the major organ in this system.

The nasal cavity is not just part of the respiratory system, but also part of this sub-system of the nervous system that is responsible for your sense of smell.

Blood is made of plasma, red blood cells, white blood cells, and these clotting cells.

These hair-like projections trap dust and pathogens into globs of mucus and sweep it away from the lungs to be coughed up.

This process is when smooth muscle around the gastrointestinal tract contract in a rhythmic, coordinated way to push food through.

The pituitary gland, hypothalamus, and thyroid are in this system.

This is the number of bones in an adult human body (for the most part).