The circulatory system is made up of the heart, the blood vessels, and the blood, which is contained in the blood vessels.

C. heart, blood, and blood vessels

Atria are the upper chambers where the blood enters into the heart.

D. atria

The blood which is pumped out of the heart passes through a large artery called aorta.

A. aorta

White blood cells help fight infection by destroying the invaders in our body, such as pathogens, bacteria, and viruses.

D. white blood cells

A network of thin blood vessels which brings nutrients and oxygen to the different tissues in the body is called capillaries.

B. capillaries

Hemoglobin, which is a protein molecule found in red blood cells, carries oxygen throughout the body.

A. hemoglobin

The diagram shows some fibrin filaments, which are released by cell fragments called platelets, that are trapping the blood cells from leaving a damaged or ruptured blood vessel. This event prevents loss of blood by causing a clot.

C. platelets

Gas exchange takes place in the small air spaces called alveoli.

A. alveoli

Larynx, which is known as the voice box, houses the vocal cords.

A. larynx

Diaphragm is the flat muscle that separates the chest cavity and the abdominal cavity of the body. It plays a vital role in the process of respiration.

C. diaphragm

In a closed circulatory system, the blood does not flow freely in the body cavity. Instead, the blood is contained within the blood vessels as it circulates around the body.

The **pulmonary circulation** transports the deoxygenated blood from the right ventricle of the heart to the lungs and then returns oxygenated blood to the left atrium of the heart. The **systemic circulation**, on the other hand, pumps oxygen-rich blood to all parts of the body through the arteries and picks-up carbon dioxide and waste materials from the body through the veins.

The **systemic circulation** pumps oxygen-rich blood to all parts of the body through the arteries and picks-up carbon dioxide and waste materials from the body through the veins.

The valves found in the heart ensures that there is no backward flow of blood. The mitral and tricuspid valves prevent the backflow of blood from the atria to the ventricles, whereas the aortic and pulmonary valves control the flow of blood that exits from the ventricles.

Mitral valve is found between the left atrium and left ventricle, while the tricuspid valve is at the right atrium and right ventricle. On the other hand, the pulmonary valve is found between the right ventricle and the pulmonary artery, whereas the aortic valve is located between the left ventricle and the aorta.

The valves found in the heart ensures that there is no backward flow of blood. Mitral valve is found between the left atrium and left ventricle, while the tricuspid valve is at the right atrium and right ventricle. On the other hand, the pulmonary valve is found between the right ventricle and the pulmonary artery, whereas the aortic valve is located between the left ventricle and the aorta.

The pacemaker is a device used to control abnormal heart rhythms. It sends impulses to the atria to ensure that the wave of muscle contractions in the heart is in the normal pace.

The pacemaker generates electrical impulses to the muscle fibers in the atria. Then, the impulses are brought to the ventricles by the atrioventricular node. As soon as the impulses are received, the muscle fibers in the atria and ventricles start to contract to ensure an efficient blood flow in and out of the heart.

Blood vessels are pathways or channels that function to transport blood from the heart to the body’s tissues, and vice versa. There are three types of blood vessels called the arteries, veins, and capillaries.

**Three types of blood vessels**:

– **Arteries**- transport blood away from the heart. These blood vessels carry oxygen-rich blood, that is why they have relatively thick walls that help them withstand the strong pressure from the contraction of the heart.

– **Veins** – brings back blood from the body tissues to the heart. It carries deoxygenated blood, and it has thinner walls compared to the arterial walls.

– **Capillaries** – are the smallest type of blood vessel, and they are only one cell thick. They connect the veins and the arteries and their main function in the circulatory system is to bring nutrients and absorb carbon dioxide is done in these vessels.

The top or first number in the blood pressure is called the systolic pressure. It measures the pressure within the blood vessels when the ventricles contract. The diastolic pressure, which is the bottom or second number, measures the pressure felt in the blood vessels when the ventricles relax.

**Physical exercise** can improve cardiovascular function because it improves the ability of the muscles to get oxygen out of the blood, reducing the burden on the heart to pump blood into the muscles. It also reduces the stress hormone in the body, and it also lowers blood pressure. This is the reason why exercise helps in improving someone’s physical and emotional state.

The **blood** is a specialized connective tissue that is composed of the following: red blood cells, white blood cells, platelets, and plasma. This tissue plays an important role in the transport of oxygen and nutrients to the body, and in waste removal.

**Functions of the different blood components:**

– Plasma- carries breakdown materials, nutrients, hormones, and signals body activities. Moreover, it regulates the amount of water in the blood, fights diseases, and forms blood clots.
– Red blood cells – carry oxygen to all of the cells in the body.
– Platelets – cell fragments that have an important role in blood clotting.
– White blood cells – are important in the immune system. It recognizes, disease-causing organisms, and chemicals that are potential invaders of the body.

**Hemophilia** is a genetic disease characterized by the inability of an individual to clot blood properly due to the lack of clotting proteins in the blood. This disorder can result in spontaneous bleeding, and it is very fatal.

People with hemophilia must avoid any injury, cuts, or bruises because it can damage their tissues and organs, due to the spontaneous bleeding.

**Lymphatic system** is a system under the circulatory system composed of various networks of vessels, tissues, and organs that function in the maintenance of body fluid through collecting the extracellular fluid and transporting them back into circulation. Moreover, the lymphatic system also initiates the immune response.

**Breathing** is defined as the travel of air into and out of the lungs. It is an important function controlled by our nervous system, specifically our **medulla oblongata**. The autonomic nerves present in this organ and our diaphragm creates the contraction that regulates our breathing process.

medulla oblongata

The harmful substances in a tobacco smoke are nicotine, carbon monoxide, and tar.

Nicotine is a kind of stimulant drug that makes the heart rate and blood pressure increase.

Carbon monoxide blocks the oxygen in the hemoglobin, which results to deprivation of oxygen in the body.

Tar increases the risk of getting a cancer.

Emphysema is a lung disease that is characterized by the impairment of the air sacs in the lung tissues. Because of this disease, a person experiences shortness of breath or difficulty in breathing since the lung tissues, which are involved in the gas exchange, are damaged.

After a physical activity, our heart needs time to recover in order to return to its normal heart rate. To know the amount of time needed to resume to the normal heart rate, here is a sample experiment:

Materials:
a. Paper and pen
b. Stopwatch
c. Calculator (optional)

Steps:
1. Ensure that you are rested for 10 minutes.
2. Get and record your resting heart rate (beats per minute).
3. Jog in place for about two minutes.
4. Once the two minutes are up, get and record the heart rate again.
5. Start the stopwatch and record your heart rate every minute until 5 minutes have passed.
6. See if the last recorded heart rate has reached your resting heart rate. If not, continue to record until it reaches the resting heart rate.
7. Check the results and determine the amount of time for the recovery until the normal heart rate has returned.

After a physical activity, our heart needs time to recover in order to return to its normal heart rate. To know the amount of time needed to resume to the normal heart rate, click to see the sample experiment.

A blood clot inside the blood vessels is fatal because it can block the blood flow to the major organs. It can lead to angina, stroke, heart attack, or paralysis.

**Hemoglobin** is the substance found in the red blood cells which plays an important role in the transport of oxygen and carbon dioxide in the body. Therefore, it is important to note that we need to have an adequate amount of red blood cells and hemoglobin in the blood.

When a disease, infection, or condition causes a *sudden drop in hemoglobin and RBCs*, our body may not get enough oxygen, and we may not excrete enough carbon dioxide out of the body—this will result in a feeling of always being weak and tired.

**Artherosclerosis** is a disorder in which lipid deposits build plaque along the inner walls of the arteries. This can cause a formation of blood clots and may interrupt in the flow of blood from the heart to the body. One of the major consequences of atherosclerosis is *stroke*.

A **stroke** is a life-threatening condition that can occur when the blood supply for the brain areas is cut-off or blocked due to a blood clot. The brain cells may gradually die due to the lack of oxygen supply, thus some brain functions may be lost. Therefore, because *Aspirin* reduces the clot-forming capability of the blood, it is prescribed by some doctors to those patients that experienced a stroke– to prevent further blood clots in the central nervous system area.

These valves are not needed in arteries as arteries carry blood away from the heart and to the rest of the body, so they have the advantage of gravity. **Veins** need the valves because **they are working against gravity.**

Organs are composed of cells that require oxygen to perform its function and to maintain homeostasis. The uptake of oxygen in other organs depends on the blood since it carries the oxygen from the lungs. The reason why there are differences in the percentage of blood flow in the human organs is due to their specific metabolic needs. Some organs would have to demand a higher percentage of oxygen uptake due to their specific functions.

However, the blood flow is different when the body is at rest or doing a physical activity. According to the table, there is an increase in the blood flow in the skeletal muscles during an exercise. This is because the heart pumps rapidly to produce more blood in order to compensate for the oxygen required by the body, particularly the muscles.

Since a respiratory care practitioner knows the particular position and functions of the organs in the respiratory system and the nature of the diseases, he or she will be able to respond quickly on how to treat a person who suffers asthma and other respiratory diseases. They know which emergency procedures to perform, equipment to use and medicines to give in order to ease the difficulty of breathing of patients.

The lymphatic system includes the lymph nodes, thymus, and the spleen that filter and remove the damaged cells found in the blood and blood vessels. They also cleanse the circulatory system by trapping and fighting any harmful bacteria and microorganisms. If these organs are removed, the body will have a reduced immunity against certain diseases due to the inability to cleanse the blood from toxins, pathogens, and other foreign invaders that attack the body.

Hemophilia is a disorder wherein a person suffers from a deficiency of blood-clotting proteins. Because of this, they are highly prone to internal bleeding. By injecting concentrates of clotting proteins into the veins, it helps compensate for the insufficient supply of clotting factors.