Circulatory System

• Main functions of the circulatory system include: transporting of oxygen and carbon dioxide, distributing of nutrients, discarding wastes, maintaining body temperature, and the circulation of hormones
• The two types of circulatory systems are the open circulatory system and the closed circulatory system
• Open circulatory systems are often found in invertebrates where blood flows freely through the cavities of the body without the use of blood vessels
• Closed circulatory systems are found in vertebrates where blood is always contained within vessels
• The human circulatory system is also known as the cardiovascular system.
• The cardiovascular system consists of the heart ( cardiovascular ), the lungs ( pulmonary ), and arteries, veins, coronary and vessels (Systemic)
• The right side of the system deals with de-oxygenated blood
• The left side of the system deals with oxygenated blood
• The human circulatory system is called a double circulatory system because blood passes through the heart twice per circuit
• The circulatory system consists of the heart, blood, and blood vessels
• The heart is protected by the ribcage, sternum, and spine
• The top two chambers of a heart are called the atria and are thin-walled
• The bottom two chambers of a heart are called the ventricles and are thick-walled
• Blood flows from the left atrium to the left ventricle via the bicuspid valve
• Blood flows from the right atrium to the right ventricle via the tricuspid valve
• Blood flows from the right ventricle into the pulmonary arteries via the pulmonary semilunar valve
• The structure that separates the left and right side of the lungs is called the septum
• De-oxygenated blood enters the right atrium via the superior vena cava and inferior vena cava
• The pulmonary circuit is a low pressure system
• The systemic circuit is a high pressure system
• The pulmonary trunk, which divides the left and right pulmonary arteries take de-oxygenated blood to the lungs
• Blood flows from atria to ventricles
• Arteries leave the heart while veins return to the heart
• Oxygenated blood is carried from the left ventricle to the aorta through the aortic semilunar valve
• Left ventricular walls are two times thicker than the right ventricle
• Pulmonary trunk splits into the right and left pulmonary artery
• The walls of the heart are called the endocardium, the myocardium, and the pericardium
• The endocardium lines the hollow chamber of the heart and is continuous with the valves
• The myocardium, myo- meaning muscle, is the thickest layer which contracts the heart and pumps blood
• The pericardium is composed of two parts: the visceral pericardium and the serous pericardium
• The serous pericardium secretes serous fluid to lubricate the heart in order to minimize friction
• The aorta branches into smaller systemic arteries, arterioles, and capillaries
• Capillaries rejoins as venules and then veins
• Arteries are strong and elastic to withstand the high pressure blood, and therefore are made of thick muscle and elastic tissue
• Valves prevent backflow of blood by allowing only one direction of flow
• Veins have thin walls because they do not need to withstand high pressures like arteries
• The walls of capillaries are only a single-cell thick and permeable
• Semilunar valves are located between arteries and ventricles
• Both the pulmonary and aortic semilunar valve prevents blood from flowing back into the ventricles when relaxed
• Both the tricuspid and bicuspid valve prevent blood from flowing back into the atrium when the ventricle contracts