The cardiovascular system consists of the heart, blood vessels, and the approximately 5 liters of blood that the blood vessels transport. Responsible for transporting oxygen, nutrients, hormones, and cellular waste products throughout the body.
The cardiovascular system is powered by the body's hardest-working organ the heart, which is only about the size of a closed fist. Even at rest, the average heart easily pumps over 5 liters of blood throughout the body every minute.
The Heart
The heart is a muscular pumping organ located medial to the lungs along the body's midline in the thoracic region. The bottom tip of the heart, known as its apex, is turned to the left, so that about 2/3 of the heart is located on the body's left side with the other 1/3 on right. The top of the heart, Known as the heart's base, connects to the great blood vessels of the body: the aorta, vena Cava, pulmonary trunk, and pulmonary veins.
Blood Vessels
Blood vessels are the body's highways that allow blood to flow quickly and efficiently from the heart to every region of the body and back again. The size of blood vessels corresponds with the amount of blood that passes through the vessel. All blood vessels contain a hollow area called the lumen through which blood is able to flow.
Around the lumen is the wall of the vessel, which may be thin in the case of capillaries or very thick in the case of arteries.
All blood vessels are lined with a thin layer of simple squamous epithelium known as the endothelium that keeps blood cells inside of the blood vessels and prevents clots from forming. The endothelium lines the entire circulatory system, all the way to the interior of the heart, where it is called the endocardium.
There are three major types of blood vessels: arteries, capillaries and veins. Blood vessels are often named after either the region of the body through which they carry blood or for nearby structures.
Blood
The average human body contains about 4 to 5 liters of blood. As a liquid connective tissue, it transports many substances through the body and helps to maintain homeostasis of nutrients, wastes, and gases. Blood is made up of red blood cells, white blood cells, platelets, and liquid plasma.
Functions of the Cardiovascular System
The cardiovascular system has three major functions: transportation of materials, protection from pathogens, and regulation of the body's homeostasis.
Transportation:
The cardiovascular system transports blood to almost all of the body's tissues. The blood delivers essential nutrients and oxygen and removes wastes and carbon dioxide to be processed or removed from the body.
The cardiovascular system protects the body through its white blood cells. White blood cells clean up cellular debris and fight pathogens that have entered the body. Platelets and red blood cells form scabs to seal wounds and prevent pathogens from entering the body and liquids from leaking out.
Blood also carries antibodies that provide specific immunity to pathogens that the body has previously been exposed to or has been vaccinated against.
Regulation:
The cardiovascular system is instrumental in the body's ability to maintain homeostatic control of several internal conditions. Blood vessels help maintain a stable body temperature by controlling the blood flow to the surface of the skin.
Blood vessels near the skin's surface open during times of overheating to allow hot blood to dump its heat into the body's surroundings. In the case of hypothermia, these blood vessels constrict to keep blood flowing only to vital organs in the body's core.
The HeartBeat
Each contraction of the heart, termed systole is followed by a relaxation phase, diastole during which the chambers fill. Each time the heart beats, both atria contract and immediately thereafter both ventricles contract.
The wave of increased pressure produced in the vessels each time the ventricles contract is the pulse. Contractions are stimulated by a built-in system that regularly transmits electrical impulses through the heart. They include the sinoatrial (SA) node, called the pacemaker because it sets the rate of the heartbeat, the atrioventricular (AV) node, the AV bundle (bundle of His), the left and right bundle branches, and Purkinje fibers.