The Cardiovascular System: Anatomy & Physiology

Updated: May 27

The Cardiovascular System is made up of two fundamental parts:

  1. The Heart

  2. The Blood Vessels

The heart acts as a pump by pushing out blood; The blood vessels receive this blood, transport it around the body, and eventually bring it back to the heart.

This cycle works like a filtration system: It pushes new blood rich in Oxygen and Nutrients into the Organs, but at the same time it pulls out Carbon Dioxide which is the By Product (waste) produced by the Tissues.

Now that you know the most essential thing about the Cardiovascular System, it is time to delve deeper and learn about its structures. Don’t start stressing! I will guide you step by step into understanding the Anatomy and Physiology of the Cardiovascular System.

Cardiovascular System Anatomy & Physiology – Part 1


Typically, the heart is found in the Mediastinum (the centre of the Chest Cavity). It has a cone-like shape slightly tilted to the left, and it is roughly the same size as a person’s fist. Just below the heart is the Diaphragm (a vital muscle in breathing), behind it is the Vertebral Column, and in front of it is the Sternum (aka. Breast Bone). The heart is squeezed in between the Lungs and shielded by the Ribs.

Now that you know where the heart is located, we will move on to understand it’s surroundings.

The heart is found inside a pocket of fluid that has two walls, together these walls are known as The Serous Pericardium. The outer wall is the Parietal Layer, it is attached firmly to another layer known as the Fibrous Pericardium. The Fibrous Pericardium is made up of strong, dense Connective Tissue, it’s job is to keep the heart in place, and prevent it from overfilling with blood.

The inner wall is the Visceral Layer, and it is attached firmly to the heart. Together with the heart, this creates the Epicardium (aka. the outer layer of the heart).

Great! By now, you should know all about the outer layers of the heart.  Let’s find out what it looks like from the inside.

We left off at the Epicardium, so moving in, the next layer is the Myocardium. The Myocardium is made up of Cardiac Muscle Cells which contract and pump blood.  Along with the cardiac muscle cells, there are Connective Tissue Fibers made of Collagen. Together, the cardiac muscle cells and connective tissue fibres form the Fibrous Cardiac Skeleton, which keeps the rigid shape of the heart.


The Myocardium makes up the majority of the heart tissue, so it is considered to be a VIP. Because of this, it has specific blood vessels known as Coronary Vessels that bring in fresh blood directly to it. Ultimately, the innermost layer of the heart is the Endocardium. The Endocardium is built by a skinny layer of Endothelium Cells, and it covers the heart chambers and valves.


Ok! That is it on Layers! My Grandma’s sponge cake has fewer layers than that. But anyway, now we will move on to understand how blood enters the heart.

Cardiovascular System Anatomy & Physiology – Part 2

Take a look at this picture, and you will see that the heart has 4 “Rooms”: The Right Atrium and Right Ventricle, the Left Atrium and Left Ventricle.

Ps. When we refer to pictures of the heart we look at it in a mirror view (so the left side on paper is the right side of the heart)

It’s important to understand that blood flows from the right atrium into the right ventricle, and from the left atrium into the left ventricle. To make sure that it does not flow the other way round, the heart has 2 valves called The Atrioventricular Valves.

Do you understand what I said so far? If not, then go back and reread it.

 If you think you’ve got the hang of it, then let’s see how blood actually moves around now

There are two main entries for Deoxygenated Blood to go into the heart:

  1. The Superior Vena Cava: A blood vessel at the TOP of the right atrium

  2. The Inferior Vena Cava: A blood vessel at the BOTTOM of the right atrium

There’s also a ‘secret back door’ for deoxygenated blood to enter the heart, and that is through the Coronary Sinus in the Right Atrium.


As we already mentioned, the deoxygenated blood will flow into the right atrium past a valve to enter the right ventricle. This valve is known as the Tricuspid Valve, as it has 3 small flaps attached to the Papillary Muscle. When the Heart contracts the Papillary Muscle pulls on the flaps, this allows blood to flow into the right ventricle and prevents regurgitation (backflow) of blood back into the atrium.


At the same time, the contraction pushes blood out of the Pulmonary Valve into the Pulmonary Artery. The pulmonary artery then transports the blood AWAY from the heart into the lungs.

Ok Let’s ReCap:

Blood flows into the Right Atrium through the Superior Vena Cava, Inferior Vena Cava or the Coronary Sinus. The heart contracts, pushing blood through the Tricuspid Valve into the Right Ventricle, and through the Pulmonary Valve into the Pulmonary Artery.

Got it? Good! Mela, the next step is for the blood to travel through the Pulmonary Artery into the Lungs.

Cardiovascular System Anatomy & Physiology – Part 3

Up until now, the blood has been Deoxygenated (meaning filled with Carbon Dioxide). The carbon dioxide makes the blood look darker, so many pictures draw deoxygenated blood as blue.

When Deoxygenated blood arrives in the lungs, it will exchange the carbon dioxide for oxygen. So, the lungs take up the carbon dioxide and push oxygen into the blood. This process makes the Blood Oxygenated and gives it a bright red colour.


From here, Oxygenated Blood will travel through the Pulmonary Veins which leads to the Left Atrium of the heart.


If you paid attention, you would notice that:

Blood has left the heart from the Right Ventricle; made it’s way through the Pulmonary Artery into the Lungs to exchange CO2 and O2, and found it’s way back to the heart through the pulmonary vein. This cycle is known as Pulmonary Circulation.

Cardiovascular System Anatomy & Physiology – Part 4


By now, the blood is in the Left Atrium. When the heart contracts, the blood leaves the Left Atrium goes through the Mitral Valve and arrives in the Left Ventricle. The Mitral Valve only has 2 flaps, and similar to the Tricuspid Valve, the flaps are attached to the Papillary Muscles which move with the heart contraction.


The last step is for the blood in the Left Ventricle to go through the Aortic Valve into the Aorta, which is the largest artery in the body. The aorta divides into several small branches which will deliver the oxygenated blood to organs and tissues.


When the oxygenated blood reaches the organs and tissues, it will push oxygen into the organs or tissues and take carbon dioxide instead. This makes the Blood Deoxygenated again, and so the cycle starts over again.

So put it all together:

The Oxygenated Blood leaves the Left Ventricle through the Aorta, which transports it around the body to collect Carbon Dioxide. The now Deoxygenated Blood travels back through the one of the Vena Cava into the Right Atrium. This cycle is called Systemic Circulation

And that’s it! That is the whole Cardiovascular System Congrats! There’s plenty more to learn about it, but we can get into that later.


 


Did you find this article helpful? Make sure to read the rest of my Anatomy and Physiology notes

If you have any questions send me a message on my Instagram Account Nurse.Miriana


References:

  • Rehman I, Rehman A. Anatomy, Thorax, Heart. [Updated 2021 Sep 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470256

  • Mori, S., Tretter, J. T., Spicer, D. E., Bolender, D. L., & Anderson, R. H. (2019). What is the real cardiac anatomy?. Clinical anatomy (New York, N.Y.), 32(3), 288–309. https://doi.org/10.1002/ca.23340

  • Buckberg, G. D., Nanda, N. C., Nguyen, C., & Kocica, M. J. (2018). What Is the Heart? Anatomy, Function, Pathophysiology, and Misconceptions. Journal of cardiovascular development and disease, 5(2), 33. https://doi.org/10.3390/jcdd5020033

  • Buckberg, G. D., Nanda, N. C., Nguyen, C., & Kocica, M. J. (2018). What Is the Heart? Anatomy, Function, Pathophysiology, and Misconceptions. Journal of cardiovascular development and disease, 5(2), 33. https://doi.org/10.3390/jcdd5020033

  • Hinkle, Janice. Brunner & Suddarth's Textbook of Medical-Surgical Nursing . Wolters Kluwer Health. Kindle Edition.




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