Human Anatomy and Physiology: The Circulatory System and Circulatory Diseases
By: Arjun Arunkumar
Tags: Circulatory System, Biology, Anatomy, Science, Heart

The circulatory system is one of the most important systems of our body. Its the system responsible for bringing oxygen to your body’s cells and taking away waste products. It works in tandem with the respiratory system in order to work effectively.

Parts of the Circulatory System

The Heart

The heart is in the center of the chest. It is made up of four chambers and numerous valves that work together to handle the blood flow of your body. These four chambers are known as the right atrium, left atrium, right ventricle and left ventricle.

The upper chambers of the heart are known as the atria. The right atrium recieves deoxygenated blood from the body through the superior and inferior vena cavas. The left atrium recieves the oxygen rich blood that is transported from the lungs. The valves that connect the atriums to their respective ventricles are called the atrioventricular valves. They are the tricuspid valve on the right atrium and the mitral valve on the left atrium. Ventricles are the chambers which are found on the lower regions of the heart. The right ventricle receives the deoxygenated blood that the right atrium collected from the body and sends it to the lungs through the pulmonary arteries. The left ventricle receives the oxygen rich blood from the left atrium and sends it to the aorta so it can be sent back out to the body.

The wall of the heart is made of three different layers. The outermost later is known as the epicardium, then the myocardium and the innermost layer is known as the endocardium. In the three layers, the inner and the outer layers are thin while the myocardium is thick as it is made up of cardiac muscle fibres.

The heart and the circulatory system consist of two types of blood vessels. These are veins and arteries. While these are both blood vessels, they have a number of key differences. Your arteries are responsible for carrying oxygen rich blood to your cells. On the other hand, veins carry the blood back to your heart to absorb more oxygen. About 75% of all the blood in your body is in your veins. One key difference is that veins have valves while arteries do not. Veins often need to push blood against gravity in order to get the blood back to your heart. The one way valves in your veins open for blood going towards the heart but don’t allow the blood to flow back.‌

The Lungs

As you know, the blood brings oxygen and takes away the carbon dioxide waste from the cells. Once the oxygen has been dropped off and the carbon dioxide is picked up, the blood can be considered used blood. The used blood is then transported to the lungs so it can be replenished.

In the alveoli of the lungs, the oxygen the respiratory system has brought in is swapped for the carbon dioxide in the used blood. The alveoli are incredibly thin and are surrounded by capillaries. The used blood goes through these capillaries and then the oxygen and carbon dioxide are swapped. Then as you exhale, the carbon dioxide is expelled.

Stages of the Circulatory System

The circulatory system starts with the oxygenated blood being pumped out to your body through your aorta. The oxygenated blood then goes to your body’s cells to drop off oxygen and collect carbon dioxide. The reason we need the oxygen is so our cells can go through cellular respiration and get energy. The carbon dioxide your blood picks up is a byproduct of cellular respiration. The deoxygenated blood enters your right atrium through the superior and inferior vena cava.

The blood then goes through the tricuspid valve in order to reach the righ ventricle. Your right ventricle then pumps deoxygenated blood through the pulmonary valve up to your pulmonary artery. The pulmonary artery then takes the deoxygenated blood to the lungs.

The deoxygenated blood becomes oxygenated and drops off waste

at the alveoli, which are little sacks storing the oxygen that we inhale. Oxygen is transferred into the blood and waste is transferred out of the blood through the capillaries. The newly oxygenated blood leaves the lungs and returns to the heart through the pulmonary veins and enters the left atrium, ready to return to the cells of the body.

The left atrium pumps blood through the mitral valve to the left ventricle. From here, the blood is pumped to the aorta. The aorta then starts the cycle all over again, sending the blood out to your body. Over the course of the day, more than 2000 gallons of blood are cycled through the heart.

Common Illnesses and Disorders

Coronary heart disease and Angina

Over time, through a process called atherosclerosis, your artery walls can get clogged up with fatty deposits that are called atheroma. If this build up causes your arteries to become too narrow, your blood supply will be completely blocked. Coronary heart disease is the term used to refer to this occurrence.

If a coronary artery is fully blocked, a heart attack may occur. However, if it is only partially blocked, chest pains known as angina may occur.

Stable angina is a symptom of coronary heart disease. It can range from a slight uncomfortable feeling in your chest to a feeling of tightness that starts in your chest and could spread to your arms, jaw or back. Breathlessness is also a potential side effect. These symptoms usually go away after around 15 minutes.

Arrhythmia

Your heart rhythm is naturally controlled by the sinus node in your right atrium. The sinus node produces electrical impulses that normally start each heartbeat. These impulses cause the atria muscles to contract and pump blood into the ventricles. The electrical impulses then run into the atrioventricular node that delays the sending of the impulses. This gives the ventricles time to fill up before the electrical impulses makes them send the blood out. In a typical heart, this would result in a heartbeat of around 60–100 bpm.

Arrythmia is the term used to describe your heart beating at an irregular pace. This includes when your heart beats too fast (tachycardia), too slow (bradycardia),or just generally in an irregular way. Tachycardia is when your resting heart rate exceeds that of 100 bpm. Bradycardia is when your resting heart rate is lower than 60 bpm.

Some common causes of arrhythmia include:

Coronary heart disease

Having high blood pressure

Potential complication of heart surgery or heart attacks

There are different variations of arrhythmia and some are normal while some can be very serious. For example, occasional tachycardia is a form of arrhythmia that can be caused by caffeine if things like coffee or soda.