Circulatory System
Prepared by: Maria Johanna Baguio Testa
Circulatory System [Circulation (การไหลเวียน)]
A circulatory system (ระบบไหลเวียน) has four (4) basic characteristics (ลักษณะเฉพาะ) :
- Circulating fluid (ของเหลวหมุนเวียน)
The circulating fluid is called blood. Blood transports useful (Oxygen, hormones, nutrients, etc) and waste materials (CO2). (RBC, WBC, platelets, plasma)
- Pumping device (อุปกรณ์สูบน้ำ)
The pumping device is the heart. Blood is moved through the body by muscular contractions of the heart.
- Blood vessels (หลอดเลือด)
A complex network of blood vessels carries materials to the tissues and back to the heart. There are three main types of blood vessels, namely (arteries (oxygenated except for pulmonary arteries), veins (deoxygenated except for pulmonary veins), and capillaries).
- Valves (วาล์ว)
Valves are present in some blood vessels to prevent backflow (หลอมเหลว) and ensure that blood flows in one direction only. (Pulmonary valve, tricuspid valve (right heart), mitral valve (bicuspid valve) (left heart), Aortic valve)
The internal (inside) transport system is called circulatory system because useful materials as well as waste materials circulate the body.
Double Circulation
The human circulatory system is a double circulatory system. This means that in each complete circuit of the body, the blood must flow to the heart twice.
The human double circulatory system consists of:
- The pulmonary (lungs) circulation which transports blood between the heart and the lungs.
- The systemic (body) circulation which transports blood between the heart and all other parts of the body.
The advantage of having a double circulatory system is that it increases the pressure of the blood and the rate of flow, thereby speeding up the delivery of materials (oxygen, nutrients, hormones, stc) to the tissues.
Circulating Blood
Blood - is the transport (การขนส่ง) medium (กลาง) in the circulatory system.
Blood - transports oxygen, water, and nutrients needed by our body and waste materials such as carbon dioxide.
Blood is made up of:
- Red blood cells (RBC)
- White blood cells (WBC)
- Platelets
- Plasma
Structure of the Human Heart
The heart is a muscular organ with walls made of cardiac muscles. The coronary arteries supply nutrients and oxygen to the muscles while the coronary veins remove wastes from the muscles.
*Coronary - of, relating to, or being the coronary arteries or veins of the heart
broadly : of or relating to the heart
The heart is divided into four chambers:
- The upper chambers
Auricles or atria (singular: atrium)
- The lower chambers
Ventricles
Septum - divides the heart into the right and left halves.
When the auricles contract (สัญญา), blood is pushed into the ventricles below.
The right ventricle pumps blood to the lungs, which lie next to the heart. The left ventricle has to pump blood from the heart to the rest of the body.
The right auricle/atrium is connected to the right ventricle by the tricuspid valve. The left auricle/atrium is connected to the left ventricle by the bicuspid or mitral valve.
Semilunar valves (pulmonary valve and aortic valve) are situated at the center of the aorta and the pulmonary artery to prevent backflow (หลอมเหลว) of blood into the ventricles. The chordeae tendineae prevent the valves from turning inside out when the ventricles contract.
https://www.imaios.com/en/e-anatomy/thorax/heart
The Blood Vessels
There are three types of blood vessels:
- Arteries
Arteries are blood vessels which carry blood away from the heart. They deliver oxygenated blood, except the pulmonary artery.
- Veins
Veins are blood vessels which carry blood back to the heart. They deliver the deoxygenated (less oxygen) blood, except the pulmonary veins.
- Capillaries
Capillaries are tiny blood vessels which connect arteries and veins. They have walls which are only one cell thick.
*Diffusion is the movement of a substance from an area of high concentration to an area of low concentration.
A summary of the differences of artery, vein and capillary is given in the table below:
The Path of Blood Flow
Heart Rate
END