The heart
The ribs protect the heart. below the heart and lungs is the diaphragm. this space is called the thorax.
Systemic flow: constant blood flow removes waste from cells and delivers oxygen and nutrients to them. the heart pumps blood to achieve this.
vein: blood goes in ex. superior and inferior vena cava
artery: blood goes out ex aorta
Pulmanory Flow: the heart sends blood to the lungs, then gets pushed back to heart, and then gets squeezed out of the aorta.
coronary vessels: veins and arteries serve the heart muscle itself. part of systemic flow
Layers of the heart
Atrioventricular valves: two valves between the atrium and ventricles. they are tetherd to the heart’s walls. chordae tendinae keep the valves from flipping backward. papillary muscles: muscles within the ventricles of the heart. They play a crucial role in heart valve function by preventing backflow of blood during systole
tricuspid
mitral
interventricular septum:
membranous: a lot of babies are born with holes in the membranous part of the interventricular septum (VSD)
muscular
three layers to heart muscle
endocardium (all the way on the inside) very similar to inner lining of blood vessels. very thin, red blood cells bump up against.
myocardium is thick layer where contractile muscle is and where energy is used up
pericardium (all the way on the outside) thin layer that has an inner (visceral/epicardium) and outer (parietal) layer with a fluid containing gap in between.
Flow through the heart
the heart is a pump.
vein → blood towards the heart. comes from arms, legs, and head.
artery —> blood out of heart
blood coming in comes to the right atrium from the superior vena cava and the inferior vena cava. then, it flows into the right ventricle. it gets there by passing through a valve called the tricuspid valve. then, it goes through the pulmonary valve and splits into the left and right pulmonary arteries and the blood goes into the lungs to pick up oxygen and get rid of carbon dioxide. the blood comes back and dumps into the left atrium. it goes down into the left ventricle through the mitral valve. the final valve is the aortic valve, which divides the left ventricle from the aorta. blood goes through aorta to the rest of the body.
two circulations in the body
pulmonary trunk - blood heading towards the lungs goes through the pulmonary trunk, then into either the left or right pulmonary arteries. pulmonary veins drain blood into left atrium. this is called pulmonary circulation.
blood starts at the left venrticle through the aorta and goes to tissues and organs, then comes back into the right atrium through the inferior or superior vena cava. this is the systemic circulation.
Red blood cells don’t have mitochondria so they don’t use oxygen. they also don’t have nuclei. they simply carry oxygen around.
the heart gets blood from the coronary vessels in the systemic circuit. the veins drain blood into the right atrium.
the lungs get their oxygen from the systemic circuit via vessels going to right and left lungs called bronchial vessels. blood from various source mixes in lungs and a lot of the blood ends up going into the pulmonary circuit.
heart sounds
“lub dub”
blood going from right atrium to right ventricle is accompanied by blood going from left atrium to left ventricle. two chambers are full of blood simultaneously. to get blood into the ventricles, the valves had to open. if blood flows backwards, the valves will close down and not allow the blood to pass. when mitral and tricuspid valves are open, pulmonary and atrial are closed. when the pulmonary and ortic valves are open, the tricuspid and mitral valves shut.
when tricuspid and mitral valves shut and pulmonary and aortic valve open, the first heart sound/”lub” is made (S1)
systole - blood going out into body
the “dub” or the second heart sound (s2) is made when the pulmonary and aortic valve snap shut, and the tricuspid and mitral valves open.
diastole - blood going back into ventricles
the sounds themselves are caused by the valves snapping shut, not opening.