Circulatory System Meet the Heart!: The Thorax includes the area inside the ribs that is above the diaphragm (includes the lungs and the heart) Cells that are living need flow of blood in order to obtain O2/nutrients and discard wastes, such as CO2 (otherwise it will die) Systemic flow goes to all of the cells/areas of the body while Pulmonary flow refers to flow towards/away from the lungs Coronary vessels provides nutrients and release waste from the heart directly (is a part of the system circuit) 1. 2. 3. Layers of the Heart: Tricuspid valve is between the right atrium and right ventricle (an AV Valve) Bicuspid/Mitral valve is between the left atrium and left ventricle (an AV valve) Chordae tendineae and papillary muscles help to maintain blood flow in the correct direction (controls the valves) 3 Layers of the Heart Muscle: Endocardium is the innermost layer of the heart and is a very thin layer Myocardium is the middle layer and is the largest chunk of the heart muscle. This is where all the contractile muscle is located and is where the O2 is used up Pericardium is the outermost layer and has 2 layers with a gap in between (visceral → AKA epicardium which is inner and parietal which is the outer part) Flow Through the Heart: Veins means blood going toward the heart and arteries means blood going away from the heart Lub Dub: “Lub” occurs when the tricuspid and mitral valves (AKA atrioventricular valves) snap shut “Dub” occurs when the pulmonary and aortic valves (AKA semilunar valves) snap shut 1. Layers of a Blood Vessel: 3 Main Layers: Tunica Interna/Interna → made up of endothelial cells and an outer basement membrane 2. Tunica Media → made up of smooth muscle (thickest in arteries) 3. Tunica Externa → sometimes has blood vessels (known as vasa vasorum) and can also be composed by nerve endings (largest in the veins) Elastin is found in the tunica media of large/medium sized arteries (helps make the artery more elastic for high pressures) Small arteries/arterioles don’t really have elastin but still have a shit ton of muscle in the tunica media Also veins have valves not veins Capillaries can sometimes have 1 cell that make up the entire tube and do not have smooth muscle or the differing layers like the veins/arteries do Thermoregulation in the Circulatory System: Capillaries near the surface of the skin will dilate if you need to release heat and constrict of you need to conserve heat Extra Notes: Order of average pressure in different vessels: Aorta > Artery > Arteriole > Capillary > Venule > Vein