Why the circulatory system ? I mean come on, do we really need it ....
Every cell of the human body must be supplied with oxygen and nutrients and must rid itself of waste. These requirements are met by a circulatory system that transports these materials between cells and their surrounding environment.
If we didn't have the circulatory system, our cells would not be able to receive needed materials that allow it to make proteins and create ATP.
The cardiovascular system contains
a muscular heart and the vessels that transport the blood : arteries, veins and capillaries.
Functions of the circulatory system
The functions of the circulatory system include:
(1) transporting gases, nutrients, and wastes throughout the body, but also
(2) clotting to prevent loss of blood from ruptured vessels
(3) fighting invasion of the body by foreign bodies.
Arteries - what about 'em?
They carry blood away from the heart. elastic, thick-walled vessels which are capable of expanding to accommodate the larger blood volume flowing from the heart at the end of each heartbeat. Large arteries actually expand and recoil to help the heart pump blood through the systemic circulation. Small arteries called arterioles are constricted and dilated by muscles controlled by the sympathetic and parasympathetic nervous system which increases or decreases the blood pressure, respectively. This mechanism prevents you from fainting when you get out of bed each morning. Arterioles are the vessels primarily responsible for providing differing levels of “peripheral resistance” to blood flow (caused by varying blood pressure) depending on the conditions affecting the body.
Talk about capillaries ..........
The branching of arterioles causes formation of even narrower tubes called capillaries which are interconnected to form capillary beds which perform the exchange of materials with the cells of the body. The blood is collected from the capillary beds by small veins called venules many of which join to form a vein which returns the blood to the heart.
What do veins do ?
Veins carry blood back to the heart.... Veins are thinner-walled vessels which are under less pressure from the heart. For this reason veins do not have “pulses”. Only arteries, especially the ones close to the heart, should have palpable pulses. Veins have internal valves which open toward the heart and close at the end of a heart beat to prevent blood from flowing backward as the blood is returned to the heart. Because of their compliance (stretch with little recoil), the largest amount of blood in the cardiovascular system is contained in the veins.
What are the two circuits of the heart ? Which side of the heart runs each
Pulmonary Circuit - run by the right side of the heart. Pulmonary arteries will carry blood to the lungs where it will pick up oxygen. Pulmonary veins wil bring oxygenated blood back to the heart
Systemic Circuit- run by the left side of the heart. After the blood is returned to the heart from the lungs, the left side of the heart works to pump the blood out to the body
The heart is located in what area of the thoracic cavity ?
the mediastinum.( or mediastinal cavity ) between the lungs. At approx level of t5-T6 vertebrae and found between the second rib and the sixth and fith rib
1/3 of the heart will be found to the right of the median plane and 2/3 to the left
Heart is fist sized cone shaped muscular organ and about 10 oz
What is the layer of the heart that contracts?
The bulk of the heart, called the myocardium, is composed mainly of cardiac muscle and is the layer that actually contracts. The myocardium muscle fibers are highly branched and are attached by collagen connective tissue fibers which link all parts of the heart together.
What is the name of the tough, thick sac which the heart is enclosed in and anchors it to the diaphragm?
What are the layers of the pericardium ?
The inner (epicardium) and outer layers of the pericardium are covered by a smooth layer of endothelium. A special lubricating fluid between the layers allows the heart to slide around with very little friction.
The epicardium is the inner layer of the pericardium. It is also the outermost portion of the tissues that make up the "heart wall"
What makes up the heart wall?
The heart wall is made of 3 layers: epicardium, myocardium and endocardium. The thickness of the heart wall varies in different parts of the heart.
Epicardium. The epicardium is the outermost layer of the heart wall and is just another name for the visceral layer of the pericardium. Thus, the epicardium is a thin layer of serous membrane that helps to lubricate and protect the outside of the heart. Below the epicardium is the second, thicker layer of the heart wall: the myocardium.
Myocardium. The myocardium is the muscular middle layer of the heart wall that contains the cardiac muscle tissue. Myocardium makes up the majority of the thickness and mass of the heart wall and is the part of the heart responsible for pumping blood. Below the myocardium is the thin endocardium layer.
Endocardium. Endocardium is the simple squamous endothelium layer that lines the inside of the heart. The endocardium is very smooth and is responsible for keeping blood from sticking to the inside of the heart and forming potentially deadly blood clots.
What structure separates the chambers into a right and left set?
What chambers receive blood and which chambers pump the blood ?
The two upper receiving chambers are called the atria; the two lower pumping (sending) chambers are called the ventricles. The atria are smaller than and not as muscular as the ventricles which must force the blood through vessels to distant parts of the body.
What are the auricles and what is the signicance of the fossa ovalis?
The atria each have a muscular pouch on the upper surface called the auricles. There is also a shallow depression on the septum separating the atria. This depression, called the fossa ovalis, marks the place of an opening between the atria which is present in all developing fetuses. It allows fetal blood to move directly from right to left atrium, bypassing he undeveloped lungs
What are the four valves that control blood flow ?
The tricuspid valve controls blood flow between the right atrium and the right ventricle.
The bicuspid (mitral) valve connnects the left atrium to the left ventricle
The pulmonary semilunar valve controls blood flow between the right ventricle to and the lungs
The aortic semilunar valve controls blood flow between the left ventricle and the aorta.
Pathway of blood through the heart
Blood follows a path which can best be described as it returns (in a deoxygenated form) from the cells of the body entering the heart into the right atrium by way of veins called the inferior and superior vena cavae. From the right atrium blood flows through the tricuspid valve into the right ventricle which pumps the blood through the pulmonary valve into the pulmonary arteries to the lungs. After the blood is oxygenated in the capillary bed of the lungs (also losing its carbon dioxide), it is carried by the pulmonary veins to the heart entering the left atrium. This oxygenated blood flows through the bicuspid valve (mitral valve) into the left ventricle which pumps it through the aortic valve into the aorta (the largest vessel in the body) which carries it to capillary beds of the systemic trunk, supplying the cells of all body tissue with oxygen and nutrients. Deoxygenated blood is then returned to the right atrium through the vena cavae which completes the circuit.
What supplies the heart with its own blood supply?
The left and right coronary arteries, which arise from the base of the aorta and supply oxygen and nutrients to the heart tissues.
The left coronary artery runs toward the left side of the heart and divides into the anterior interventricular artery and the circumflex artery which supply the left atrium and the left ventricle.
The right coronary artery runs toward the right side of the heart and divides into the posterior interventricular artery and the marginal artery which supply the right atrium and the right ventricle.
Track the flow of blood through the heart
1. Deoxygenated blood flows toward the heart via the cranial and caudal vena cava (inferior and superior).
2. Blood passes through the right AV valve (tricuspid)
3. Blood travels into the right ventricle
4. Blood passes through the pulmonary semilunar valve
5. From here it is pumped into the lungs’ circulation via the pulmonary artery.
6. Blood picks up oxygen in the lungs.
7. The oxygenated blood travels through the pulmonary veins to the left atrium.
8. Blood passes through the left AV valve (mitral/bicuspid) and enters the left ventricle.
9. The blood passes through the aortic semi-lunar valve
10. Blood then enters the aorta where it travels into systemic circulation (to deliver oxygen and nutrients to tissues)
What is the cardiac cycle and what does it consist of ?
Consists of contractions and relaxation of the heart muscle. The term systole refers to contraction of heart chambers and the word diastole refers to relaxation of these chambers.
The heart contracts, or beats, about seventy times a minute, and each heartbeat lasts about 0.85 seconds
Each heartbeat is a cardiac cycle
What are the phases of the cardiac cycle?
Each heartbeat, or cardiac cycle, consists of the following phases:
(1) the atria contract for about 0.15 second (while the ventricles relax),
(2) the ventricles contract for about 0.30 second (while the atria relax),
(3) all chambers relax for about 0.40 second.
The short systole of the atria is understandable since the atria send blood only into the ventricles, but the ventricles pump blood into the much larger systemic or pulmonary circulatory circuits.
The contraction of the heart is intrinsic, meaning that the heart will beat independent of any nervous stimulation, but it is regulated by the nervous system which can increase or decrease the heartbeat rate.
What is systolic pressure?
Systolic pressure results from blood being forced into the arteries during ventricular systole (contraction)
What is diastolic pressure ?
the pressure in the arteries during ventricular diastole (relaxation)
What device measures blood pressure ?
a sphygmomanometer, which has a pressure cuff that measures the amount of pressure required to stop the flow of blood through an artery.
Blood pressure is stated in
millimeters of mercury. A blood pressure reading contains 2 numbers, for example, 120/80—which represents systolic and diastolic pressures, respectively.
What happens as blood flows from the aorta into the various arteries and arterioles ?
blood pressure falls. Also, the difference in pressure between systolic and diastolic gradually diminishes
Compare the flow of blood in the capillaries with the flow of blood in the veins and the arteries
In the capillaries, there is a slow, fairly even, flow of blood. Blood pressure in the veins, however, is low and can even approach zero. Arteries have the highest blood pressure because blood is actively being pumped into them by the heart
If veins have such low blood pressure, how are they able to return blood to the heart?
1) low resistance in the venous walls,
2) the presence of internal valves which prevent the backward flow of blood
3) the assistance of muscular movement in the limbs and chest, blood in the veins is able to maintain a flow rate significant enough to return the blood to the heart.
For the heart to function as a pump, it must contract and relax in a cyclical pattern.
The cycle is divided into two parts:
Systole: the heart is contracting and ejecting blood into circulation
Diastole: the heart is relaxing and filling with blood.
The cardiac cycle is the sequence of events in ONE complete heart beat.
1. Ventricular contraction (systole) causes a rise in ventricular pressure and results in the closure of the AV valve (LUB) and opening of the aortic and semilunar valves.
2. During ventricular relaxation (diastole), the AV valves open and the aortic semilunar valves close (DUB) due to back pressure in the aorta and pulmonary trunk.
First heart sound is the closure of the AV valves. (Tricuspid and Bicuspid (mitral))
Second Heart sound is the closure of the semilunar valves. (Pulmonary and aortic)
What maintains the heart's intrinsic rhythmic abilities ? Could it beat on its own?
The action of the nervous system enables the heart to respond to changes in:
an elaborate electrical system.
The contractions of the cardiac muscle begin within the heart muscle itself, making it somewhat independent of any nerve supply from the central nervous system. If removed from the body, the heart could continue to beat on its own with proper nutrients and oxygen. However, the nervous system and endocrine systems do regulate the heart rate through neurotransmitters such as norepinephrine and acetycholine. This enables the heart to respond to variations in blood pressure and emotional and physical stressors. The following is a brief description of the electrical impulse that moves through the heart during each cardiac cycle.