The cardiovascular system contains the Heart, Blood vessels and blood. There is approximately 5 liters of blood that course through these blood vessels as it’s pumped by the Heart. The cardiovascular system transports nutrients, oxygen, cellular waste products and hormones to the rest of the body. The heart pumps blood throughout the body every minute.
The Heart
The heart is a fist sized organ located in the thoracic region. The great blood vessels (aorta, pulmonary trunk, vena cava and pulmonary veins) are connected at the top of the heart.
There are two circulatory loops, the systemic circulatory loop and the pulmonary circulatory loop.
The systemic loop carries oxygenated blood from the left side of the heart to the body tissues and organs (except to the heart and lungs) and returns deoxygenated blood to the right side of the heart.
The systemic circulatory loop also gets rid of waste from body tissues.
The pulmonary circulation loop carries deoxygenated oxygen from the right side of the heart to the lungs where it picks up oxygen and returns it to the left side of the heart.
The heart contains four chambers: right atrium, right ventricle, left atrium, left ventricle.
Blood vessels
Blood vessels are the blood ‘highways’ of our body. The size of the vessel corresponds to the quantity of blood that goes through (arteries are thick and capillaries thin). The hollow portion of the blood vessel through which blood passes is called the lumen. Blood vessels are lined with a thin layer of epithelium known as endothelium.The endothelium prevents blood clots and protects blood cells.
There are three types of blood vessels: capillaries, arteries and veins. Blood vessels are usually named according to the region they carry blood or nearby body structures.
Arteries- They carry blood away from the heart. All arteries except the pulmonary trunk and arteries of the pulmonary circulation loop carry highly oxygenated blood to tall parts of the body. Due to the pressure of blood going through arteries they are usually thick walled, muscular and elastic.
Arterioles are small arteries that branch off from the main arteries and carry blood to capillaries.
Capillaries- They are the smallest, thinnest and most common vessels in the body. Capillaries connect to arterioles on one end and to venules on the other. Capillaries help in the exchange of gases, nutrients and waste products. The endothelium of the capillaries is very thin , it acts as a filter to allow for gases, liquids and nutrients to go through while keeping the blood cells inside the capillaries.
Veins- they carry deoxygenated blood to the heart. Veins undergo low blood pressure, their walls are therefore thin, less elastic and less muscular. Since veins do not rely on the heart to pump blood back, they rely on gravity, inertia and skeletal muscle contractions to help in blood flow. Vein contain one-way valves to prevent the blood from flowing away from the heart.
Venules are like arterioles but connect to veins.
Coronary Circulation
The heart has blood vessels that provide the myocardium with oxygen and nutrients. The left and right coronary arteries provide blood to the left and right sides of the heart. The coronary sinus is a vein that returns deoxygenated blood from the myocardium to the vena cava
Hepatic Portal Circulation
The hepatic portal vein carries blood from the stomach and small intestines to the liver. The liver removes toxins, stores sugars and processes the products of digestion before they reach other body tissues. Blood from the liver then returns to the heart through the Vena Cava.
Blood
The body carries about 5 liters of blood. Blood carries nutrients, waste and gases throughout the body. Blood is made up of red blood cells, white blood cells, platelets, and liquid plasma.
- Red blood cells- They make up 45% of blood volume. Red blood cells are produced in the red bone marrow. About 2 million are produced every second! Red blood cells look like a concave disk. This shape gives them a high surface are and helps them squeeze through the capillaries. The high surface area to volume ratio allows oxygen to be easily transferred into and out of the cells. Red bloods cells contain no DNA and are unable to repair themselves. Red blood cells transport oxygen throughout the body through the red pigment hemoglobin. Hemoglobin contains iron and proteins.
- White blood cells- white blood cells make a small percentage of blood. They help with immunity. There are two classes of white blood cells: granular leukocytes and agranular leukocytes.
- Granular leukocytes- There are three types: neutrophils, eosinophils, and basophils. Neutrophils contain digestive enzymes that neutralize bacteria. Eosinophils contain digestive enzymes for digesting viruses that have been bound to by antibodies in the blood. Basophils release histamine to intensify allergic reactions and help protect the body from parasites.
- Agranular Leukocytes- There are two types: lymphocytes and monocytes. Lymphocytes include T cells and natural killer cells that fight off viral infections and B cells that produce antibodies against infections by pathogens. Monocytes develop into cells called macrophages . They ingest pathogens and the dead cells from wounds or infections.
- Platelets- They are responsible for clotting. Platelets form in the red bone marrow. They have a short lifespan, usually about a week.
- Plasma- This is the liquid part of the blood. It contains water, proteins and dissolved substances. Plasma makes about 55% of the blood volume. The proteins in the plasma include antibodies and albumin. O dissolved in the plasma, including her substances dissolved in plasma include: oxygen, carbon dioxide, electrolytes, nutrients, and cellular waste products. The plasma functions as a transportation medium for these substances.
The cardiovascular system has three functions: transportation, regulation and protection.
Transportation- It transports blood throughout the body. The blood transports nutrients, hormones and oxygen and removes waste materials and carbon dioxide to be processed or removed from the body.
Protection- The cardiovascular system protects the body through its white blood cells. The platelets and red blood cells create protection against outside infection by creating scabs. Blood also carries antibodies that provide immunity.
Regulation- Blood vessels help maintain a stable body temperature by controlling the blood flow to the surface of the skin. Blood also helps maintain the body’s pH. The albumins in the blood help balance the osmotic concentration of the body’s cells.
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