Anatomy Sr. Assessment

Matt LaMalfa
Anatomy Final Assessment

One of the most important and complex organ systems in your body is the cardiovascular system, which includes the heart as well as all the veins and arteries of the body. The main function of the cardiovascular system is to transport blood, hormones, and cell waste. By far, the most important part of the cardiovascular system is the heart. The heart is a muscle, which weighs about one pound and is about the size of your fist. It is located around the fifth intercostal space, on the left side of your sternum. To insure the heart is protected, it is covered by a special covering called the pericardium, which looks like plastic wrap made into a sack. Inside the pericardium is serous fluid, which keeps the heart lubricated and maintains a frictionless environment for heart processes to take place. The heart is divided into three layers, the epicardium, which is the outermost layer, the myocardium, the layer in the middle, and the endocardium, which is the innermost layer. The epicardium is made up mostly of connective tissue, and its main function is protecting the heart. The myocardium has special muscle cells you can’t find anywhere else in the body. As the inner layer, the endocardium lines the chambers of the heart. All these layers are combinations of skeletal muscle, which helps to pump blood, and smooth muscle, which aids in involuntary processes.
The heart is made up of four chambers, two atria and two ventricles. The atria, which are located above the ventricles, serve as receiving chambers for blood and play no role in the pumping of blood. The ventricles serve as the pumping chambers, and are made have thick, muscular walls, unlike the atria, which have walls made up of smooth muscle. Because of these multiple parts, the heart is sometimes referred to as a double pump. One of the major jobs of the cardiovascular system is pulmonary circulation, the process when blood without oxygen is transported to the lungs, oxygenated, and then returned to the heart. Pulmonary circulation begins on the right side of the heart, when the blood returns to the right atrium after all the oxygen has been used. The heart moves from there into the right ventricle, from where the blood leaves the heart for the lungs via the left and right pulmonary arteries. After the blood picks up the needed oxygen in the lungs, it returns to the heart at the left atria. From the left atria, blood flows into the left ventricle, where it departs for the rest of the body via the aorta.
Opposite pulmonary circulation is systemic circulation, which includes carrying oxygenated blood away from the heart, to the body, and returning deoxygenated blood back to the heart. The first organ supplied with blood is, obviously, the heart, through the coronary arteries. Then we go to the aortic arch, where the first branch, the brachiocephalic, supplies the right common carotid and the right subclavian. The left common carotid branches into the internal carotid, which supplies the brain, and the external carotid, which supplies skin and muscles. The third branch of the aortic arch, the left subclavian, supplies the vertebral artery. Moving away from the aortic arch, you hit the axillary artery, which goes into the brachial artery and supplies the upper arm and then goes into the radial and ulner arteries, which take care of the lower arm. The thoracic aorta in the chest goes into the intercostal arteries, which provides blood to the muscles of the thoracic wall. In the abdomen, the abdominal aorta leads to the celiac trunk which has three major branches, the left gastric artery, splenic artery, and common hepatic artery. These arteries supply the stomach, the spleen and the liver. The superior mesenteric supplies half of the entire small intestine and half of the large intestine, the renal artery supplies the kidneys, the lumbar artery supplies the lower back, and the inferior mesenteric takes care of the remaining portion of the large intestine. The left and right common iliac arteries both split into internal iliac arteries that are responsible for supplying the pelvic region. The anterior and posterior tibial lead to the dorsalis pedis which supplies the foot.
For all this movement to happen, there has to be something in the heart regulating the flow of blood, and that is the valves. There are four sets of valves in the heart, the atria ventricular valves and the semilunar valves. The atrioventricular valves separate the atria from the ventricles and makes sure blood only flows in one direction. Semilunar valves are located in the pulmonary artery and the aorta. Valves make sure there is no backflow of blood to areas where it should not be going. If there is some backflow, leaky valves is probably the culprit, a condition that isn’t fatal, but needs to be corrected if recognized.
The heart is always working; it pumps about six quarts of blood one thousand times a day, meaning the heart pumps around six thousand quarts of blood a day. To keep the heart going, it has an internal conduction system that is split up into two parts, the autonomic nervous system and the intrinsic conduction system. The autonomic nervous system is responsible for speeding up or slowing down the heart; while the intrinsic conduction system forces the heart to beat it’s seventy plus times a minute. For the heart to beat, a nerve impulse starts in the sinoatrial node, in the upper right part of the heart. It then travels to the AV node at the bottom of the right atria, which causes the right atria to contract. After a short pause, the impulse travels to the Purkinjey fibers, which causes the ventricles to contract, and atria relax. If something happens to the SA node, a person’s heartbeat and pulse can slow down, which may cause the need to have an artificial pacemaker installed.
Since circulation is incredibly important to your survival, you probably want to monitor it, which you can do by keeping track of your vital signs: arterial pressure, the expansion and recoil of the arteries, blood pressure, the pressure against the vessels walls, respiratory rate, and finally body temperature. There are two things to consider when measuring blood pressure: the systolic pressure which measures pressure in the arteries when the ventricles are fully contracted, and the diastolic pressure, which is measured when the ventricles are relaxing. Normal systolic pressure is between 110 and 140; normal diastolic pressure is between 70 and 80. A myriad of different factors can cause blood pressure to fall outside of that range. A person is considered hypertensive if blood pressure is above 140/90, and considered hypotensive if the systolic pressure is below 100. The two things blood pressure relies on are cardiac output, the amount of blood pumped out of the left ventricle in one minute and peripheral resistance, the amount of friction encountered as blood flows. It’s also important to keep track of the pressure points on your body located at your temporal artery, facial artery, carotid artery, brachial artery, radial artery, femoral artery, popliteal artery, posterior-tibial artery, and the dorsalis-pedis artery.
Since the heart works as a double pump, it is able to complete a cardiac cycle, which is one full heartbeat and usually takes about .8 seconds to complete. This takes place in three phases with the first being mid-to-late diastole. During this part, blood flows passively into the heart, deoxygenated blood into the right atrium, and oxygenated blood into the left atrium. At the end of this phase, the blood travels to the ventricles. The second phase to begin is called ventricular systole, when the ventricles contract, the AV valve shuts, and blood flows into the relaxing atria. In the third phase, early diastole, the ventricles relax, semilunar valves close, the AV valves open, and blood flows to the atria.
A case of special circulation takes place in the Circle of Willis. Located in the brain, the Cirlce of Willis is made up as a combination of veins and arteries. Its biggest function is another pathway to the brain in case the primary one gets blocked. Another case of special circulation is in a fetus. The lungs and digestive system of a fetus are inactive, so all nutrient and gas exchanges take place through the placenta. In the umbilical cord are three blood vessels, the very large umbilical vein, which brings nutrient rich blood and two smaller umbilical arteries that get rid of waste. The ductus venosus bypasses the liver bringing the blood right into the fetuses’ placenta and the foramen ovale allows blood to bypass the lungs and enter directly into the heart.