Introduction to the cardiovascular system

As a society, we rely on complex transportation networks in order to supply and transport important goods and materials.

The same idea goes for the human body.Here, the circulatory systems form a complex transportation network, which allows movement of important materials, such as oxygen, around the body.This circulatory system has two divisions: the cardiovascular system and the lymphatic system.

Now, let’s get our blood flowing and focus on the cardiovascular system!The term “cardiovascular” can be broken down into cardio-, meaning heart, and -vascular, meaning blood vessels.

So, the cardiovascular system consists of the heart and blood vessels, which together make up the blood transportation network of the body that carries nutrients, oxygen and waste products to and from cells.The heart is a muscular organ that lies in the chest, and it pumps blood through the network of blood vessels in the body.

It’s composed of four chambers: a right and left atrium, as well as a right and left ventricle.Next are the blood vessels, which are tube-like structures that carry the blood being pumped by the heart.

Arteries are the blood vessels that carry oxygen-rich blood away from the heart to supply the body with oxygen and nutrients, and veins carry carbon dioxide-rich blood and waste products from other parts of the body back into the heart.The blood running through these blood vessels also carry signaling molecules, called hormones, which allow for communication between organs and organ systems.Lastly, blood helps regulate body temperature.

For example, when it's really cold outside, the blood vessels lying close to the skin constrict to reduce blood flow, saving the heat within the body.Now, there are two main networks, called the pulmonary and systemic circulation, that allow for blood circulation between the heart and the tissues in our body.In the pulmonary circulation, oxygen-depleted blood from body tissues runs from the right atrium to the right ventricle of the heart into the right and left pulmonary arteries, which carry the blood into the right and left lungs.This is the one exception where arteries carry oxygen-depleted blood.

Here, the blood dumps carbon dioxide and receives fresh oxygen via gas exchange.Then, the blood runs back through four pulmonary veins to the left atrium, where it passes into the left ventricle.

This is the one exception where veins carry oxygen-rich blood. Now, this is where the systemic circulation begins, pumping oxygen-rich blood into the body’s largest artery, called the aorta.

Along its course, the aorta gives off smaller arteries that gradually branch into smaller vessels called arterioles.Near the body tissues, these arterioles further divide into smaller vessels called capillaries.

These capillaries form small networks called capillary beds, in which blood flow is reduced. This reduction in blood flow allows the exchange of gases, nutrients and waste products between the blood and tissues.Now, after this interchange of substances occurs, the capillaries regroup to form venules, which eventually drain into veins, and eventually into the two largest veins called the superior vena cava and the inferior vena cava, which collect blood from the entire body and empty into the right atrium.

And once more, the pulmonary circulation cycle restarts.Ok, now let’s pause for a second and see if you can identify the chambers of the heart and the course of blood through the pulmonary and systemic circulations.Awesome!

I’m gonna assume you got them all right, so let’s move on! Blood vessels often connect to each other, forming networks called anastomoses.These connections may be between an artery and a vein, called an arteriovenous anastomosis, between two arteries, called an arterioarterial anastomosis, or between two veins, called a venovenous anastomosis.Let’s start with arteriovenous anastomosis, which allows direct flow of blood from the arterial to venous side of circulation without the intervention of a capillary bed.These types of connections occur in some skin regions between arterioles and venules where they serve to retain body heat.Now, in some cases, the main blood vessel supplying a tissue can become blocked.

Here, arterioarterial and venovenous anastomoses provide possible detour routes, called collateral circulation to ensure structures distal to the blockage receive ample blood supply.An example of collateral circulation is the circle of Willis in the brain.

Sometimes, blood vessels may form an anastomosis, but it’s ineffective or insufficient. These vessels are called functional terminal arteries.Here, an obstruction to the main artery supplying a tissue may possibly cause tissue death.

An example of these arteries is the anterior spinal artery which runs on the anterior aspect of the spinal cord.Also, blood vessels may not form anastomoses at all.

These vessels are called true terminal arteries. An example of a true terminal artery is the central retinal artery of the eye.Since there is no anastomosis here, a blockage in the central retinal artery can cause blindness.

Now, blood may also flow through two capillary beds before reaching the heart. The venous system connecting these two capillary beds is called a portal venous system.The most prominent example of this system is the hepatic portal venous system, which directs the nutrient rich blood from the capillary beds of the digestive tract to the capillary beds of the liver.This allows the liver to filter the nutrients and other materials absorbed in the intestines for any toxins or harmful material before returning the blood to the heart.All right, as a quick recap, the cardiovascular system consists of the heart and the blood vessels.

It regulates the body temperature and carries oxygen and nutrient-rich blood to all tissues, and removes carbon dioxide and waste products from them.This system is broken down into the pulmonary and systemic circulations.

The pulmonary circulation is between the heart and the lungs, while the systemic circulation is between the heart and the rest of the body.Anastomoses are connections between blood vessels that serve as backup in case of an occlusion of an artery or vein.The arteriovenous anastomosis is a direct connection between the arterial and venous system, without the normal capillary bed in between.

Lastly, portal venous systems are venous systems that link two capillary beds. between lastly portal.

Venous systems are Venus systems that link,