In this class we’ll develop an anatomic-physiological description of the cardiovascular system. We will be interested in describing the cardiac cycle and the heart’s mechanical activity. Besides we will also introduce the concept of arterial pressure and related pathologies.
Heart’s Generalities
The heart possesses four compartments: 2 auricles (left and right) and 2 ventricles. At the center exists a structure of great importance, the septum which divides the heart in two compartments, the right or venous and the left or arterial heart.
The right auricle receives venous blood from the Superior Cave Vein and the Inferior Vein Cave.
The left auricle receives 4 vessels from the lung veins, and these carry blood of the arterial type with a large oxygen saturation level.
The left ventricle expels blood towards the aorta while the right ventricle will do the same towards the lung artery.
The lung artery transports venous blood , or with a low oxygen saturation level, which means that is more correct to describe them as discarded elements than as Carbon Dioxide. This is a remark necessary so we may reach a conceptual look. When we talk about venous blood we prefer to describe it as blood with low oxygen saturation since Carbon Dioxide in reality exists in every structure just as the discarded elements are. If we are to analyze this with a “large circulation” and “small circulation” criterion, the Superior and Inferior Cave Veins and the Aorta belong to the “large” one whereas the lung artery and the lung veins belong to the “small” or lung circulation.
Mainly, or using general concepts the Superior Vein Cave drains blood from the body’s superior half whereas the Inferior one will do the same with the inferior half.
The Aorta will be a great exit out of the heart towards the rest of the body, a great way of blood distribution towards the whole system.
Its diameter, thus, is very considerable and deals with very high pressures. In that sense it is important to remark a first difference between large and small circulation: the pressure difference. The left heart will expel blood through the aorta with a pressure which allows it to reach the toes while through the lung artery it will have to get out to reach the alveolus, to the lung. Pressure differences, in consequence, will be great between the lung artery and the aorta.
I will now offer to you some data about pressure differences. These are quite useful and some of them are very necessary to our knowledge. They are measured in mmHg which is a pressure unity.
Right Auricle 4.5
Left Auricle 8.0
Right Ventricle 4.5 a 10
Left Ventricle 9.5 a 125
Lung Artery 10 a 25
Aorta 80 a 120
It is undoubted that the left heart requires a higher pressure and this is because it needs to propel blood into a larger surface thus requiring handling higher pressures.
Blood Circulation in the Hearth
The lung vein will receive oxygenated blood from the heart. The lung veins end in the left auricle. They pass to the left auricle through a valve, the mitral valve which corresponds to the right side tricuspid valve. Both are auricle-ventricle valves. The tricuspid separates right auricle from right ventricle and the mitral valve the left ones. We then find the Lung Artery (to the right) and the Aorta (to the left). Between both ventricles and these two great vessels we can find sigmoid valves named according to those vessels (lung valve and aortic valve). If we follow the path: blood arrives from the periphery. If it arrives from the inferior part of the body (inferior members, for example) it arrives through the Inferior Cave Vein, and if it comes from the superior parts (let us say head, superior members, thorax) it makes it through the Superior one. It enters through the right auricle, passes through the tricuspid valve and it enters the right ventricle. It passes through the sigmoid valves that at this level are denominated lung valves. It rises through the lung artery trunk and later on it divides itself into right and left lung artery which will end in the lung. These arteries will go to the lung, will oxygen themselves at the lung level and will return as lung veins. The lung veins will drain in the Left Auricle. They are 4 of them. Their names are right superior, left superior, right inferior and left inferior since they are disposed square-wise that way. The important thing is that now arterial blood enters the Left Auricle from the lung vein. This arterial blood goes through the mitral valve (auricle-ventricle) and will finally enter the Left Ventricle.
From the Left Ventricle passes through the aortic valves towards the Aorta describing a large curve named as aortic key. The aortic key will finally form the aorta and this formation will repeat in the whole body. The first aortic ramifications: those organs which receive blood from these ramifications will be organs receiving more oxygenated blood since this has just left the heart. They are the brain and the heart itself. This means that Anatomy is organized in such a way that takes care of those organs which might be sensible to any possible oxygen diminution thus giving them blood which recently left the heart and which possesses major oxygen saturation. The brain, therefore, also forms part of the coronary vascular process.
Being aware of this system, which are the names of the valves and what type of vessel comes out of each side of the heart we are now ready to continue with other topics.
Capillary Concept
The vessels which we call arteries branch inside the body, they form arterioles and then smaller structures and at a capillary level these vessels begin to acquire every time weaker structures, thinner walls finally easing the gaseous exchange tissues need. This means that next to the heart, if we are to analyze a vessel’s structure, we will observe that they have a great amount of elastic fibers, of muscular walls, whereas as you reach the capillary the structure will be much thinner. This is due to the gaseous exchange through which the capillary will yield Oxygen to the tissues and receive Carbon Dioxide and discarded elements from them. In order for this process to take place the vessels structure need to be small, thin and permeable to these gases. That is what we call capillary. Not always the organism keeps this model artery-capillary-vein. This very same thing happens in the lung: lung arteries which carry low oxygen saturation blood reach the alveolus and the capillary are finally created but in this case the capillary instead of yielding oxygen receive it and exactly the opposite takes place with carbon dioxide. It saturates with oxygen and returns as lung veins this time full of oxygen. However, this scheme of artery-capillary-vein continues, this time at a lung level.
Cardiac Innervations
Within the heart it is necessary to comprehend two systems: one is the vascular which we just have reviewed. There is a second one which we need to analyze which is the nervous system. We know that the heart is a pump which will contract in a synchronic, rhythmic way and that it will need some sort of nervous system able to regulate that type of contraction. If this fails to happen, pathologies appear. This system is denominated as cardio-connector system. It is an innervation’s intrinsic system which the heart possesses. When we study sympathetic and Para-sympathetic we learn that there exists an extrinsic influence, which means that this happens out of the heart thus enabling to regulate the stress situations and other physiological situations as well. The cardio-connector, however, is a heart intrinsic system which will regulate its contraction ability. We are going to find the Sino-auricular nodule and the auricle-ventricular nodule, which we will find on the floor of the right auricle within the separation between the auricle and the ventricle. We see haceks inter-nodules (its existence is still argued). We see the Has de hiss trunk with a left and a right branch. Because we assert that the left heart is the one that is in charge of carrying all this blood, the left ventricle’s size is larger than the right and besides will have greater and more profuse innervations at the pirkinje fiber level. It is notoriously larger, and that is why any pathology will concentrate at that level. The left ventricle’s wall is very important. The thickness will reach great importance in what is denominated cardiac hypertrophy and also regarding its contraction capacity. The cardio-connector will mainly gather the capacity of step-marker. Many organs in the body have that activity: within the digestive tube, the muscular fibers and also within some central structures. In the heart there is a type of fiber with a special regulation which will discharge before the others and will mark the beat of discharge for the rest of the neurons. Since its discharge rhythm is oldstronger, the rest will follow. This is the Sino-auricular nodule (san). And will mark the beat at a discharge frequency of 70 to a 100 discharges per minute. If san fails the rest of the cardiac system will follow the group of neurons which might have the second fastest rate: the auricular-ventricular nodule (avn) which will mark a frequency of 40 to 50 discharges per minute. A failure at this level will provoke that the Has de Hiss trunk will lead the frequency at a 35 to 40 level, almost a life compatibility one.
Generally, before reaching these values the step-marker inactivity is tried to be substituted by an electrical one, introducing within the heart a devise which might produce a discharge more similar to the san’s one. The important question here is to point out that each of the fibers will make its discharge in an independent fashion, with its own frequency, but will abandon that frequency to follow the one that might have a faster frequency. They will always mate that which might have a higher discharge speed. Any muscular cell, isolated, has its own discharge frequency, but when facing other cell stimulus it discharges sooner and produces a normal discharge cycle which would produce otherwise. However, it will mate in such a way that without getting into histological details we are going to comprehend the cells the same way we analyze the skeleton muscle ones, they are muscular cells, and conform the cardiac muscle. They have different characteristics but they will also develop as an outstanding particularity a high permeability between them because they are highly coordinated to one another since it is very important that the heart might contract in a synchronic and synergic manner in order to act as a pump and propel blood towards the periphery.
Bradycardia: Slow rhythm.
Tachycardia: fast rhythm-
Arrhythmia: the heart rhythm does not keep regular intervals but it continues contracting generally in a collective manner.
A pathology produced by imbalances is the fibrillation. This is linked with channels that allow information permeability regarding what is going on in the previous cell discharge.
If we are to analyze this with a “large circulation” and “small circulation” criterion, the Superior and Inferior Cave Veins and the Aorta belong to the “large” one whereas the lung artery and the lung veins belong to the “small” or lung circulation.
Generally, before reaching these values the step-marker inactivity is tried to be substituted by an electrical one, introducing within the heart a devise which might produce a discharge more similar to the san’s one. The important question here is to point out that each of the fibers will make its discharge in an independent fashion, with its own frequency, but will abandon that frequency to follow the one that might have a faster frequency. They will always mate that which might have a higher discharge speed. Any muscular cell, isolated, has its own discharge frequency, but when facing other cell stimulus it discharges sooner and produces a normal discharge cycle which would produce otherwise. However, it will mate in such a way that without getting into histological details we are going to comprehend the cells the same way we analyze the skeleton muscle ones, they are muscular cells, and conform the cardiac muscle. They have different characteristics but they will also develop as an outstanding particularity a high permeability between them because they are highly coordinated to one another since it is very important that the heart might contract in a synchronic and synergic manner in order to act as a pump and propel blood towards the periphery. 
