Anatomy Unit 3 - Cardiovascular System 1

The bicuspid valve ________ a. is located on the left side of the heart b. is located on the right side of the heart c. guards the entrance to the aorta d. guards the entrance to the pulmonary trunk e. regulates blood flow from the superior vena cava in to the right atrium

a. is located on the left side of the heart

How many structures open into the right atrium? a. 2 b. 3 c. 4 d. 5

b. 3

identify the correct sequence of blood flow through the chambers of the heart a. lungs, right ventricle, left ventricle, right atrium, left atrium b. right ventricle, left ventricle, left atrium, lungs, right atrium c. left atrium, left ventricle, right ventricle, right atrium, lungs d. right atrium, right ventricle, lungs, left atrium, left ventricle e. left ventricle, left atrium, lungs, right ventricle, right atrium

d. right atrium, right ventricle, lungs, left atrium, left ventricle

What is the pericardium? what are its layers?

•The pericardium is a fibroserous, fluid filled sack that surrounds the muscular body of the heart and the roots of the great vessels (the aorta, pulmonary artery & vein and the superior & inferior vena cava). •It has an outer layer of dense connective tissue called the fibrous pericardium. •And an inner serous part that includes a parietal layer and a visceral layer. •The serous part is in the form of an enclosed sac with a potential space between the parietal and visceral layers called the pericardial cavity. •The pericardial cavity contains a thin film of fluid that enables the heart to move and beat in a relatively frictionless environment. Visceral layer - the inner layer of an enveloping sac or bursa that lines the outer surface of the enveloped structure, as opposed to the parietal layer that lines the walls of the occupied space or cavity. The pericardium is very similar with regards to having layers as did the lungs. There is a visceral layer of connective tissue that is applied right to the heart itself which is called the visceral pericardium. Then there is a serous layer (parietal layer). The difference between the lungs and the heart is that we add a third layer on the outside. So if we are going from most superficial too deep we have the outer most layer called the fibrous pericardium which is a non-stretchy sac essentially that the heart sits in. We will talk later about what is does for us. It is lined on the inside by the parietal layer of serous pericardium, which is analogous to the parietal layer of the pleura. Then the heart itself has a layer of visceral pericardium. In between those layers is a little space which is the pericardial cavity, and just like the pleural cavity in the lungs, it has a little bit of serous fluid in it. This fluid serves the same purpose as it did in the lungs. It allow the heart as it fills and contracts to be able to more in the pericardial cavity effortlessly with no friction. So in the picture we should have 3 layers. Fibrous pericardium, parietal layer of serous pericardium, visceral layer of the serous pericardium, a then a space between called the pericardium cavity filled with fluid.

Which of the following layers of the pericardium is innervated by the phrenic nerve? 1. outer wall 2. inner wall 3. visceral pericardium 4. pericardial cavity 5. fibrous pericardium

5. fibrous pericardium

What occurs in Mitral Value Prolapse? what can it lead to?

Can result in enlargement of the Left atrium The image is showing us what we might see if a pt has Mitral Value Prolapse. If there is significant left AV valve prolapse, it can cause enlargement of the left atrium, as there is some portion of blood that is always back flowing into it.

How is cardiac tamponade treated?

Cardiac tamponade is treated with a Pericardiocentesis surgery. Pericardiocentesis is the aspiration of fluid from the pericardial space. This procedure can be life saving in patients with cardiac tamponade. cardiac tamponade can be treated with a Pericardiocentesis. A needle of tube is inserted into the pericardial space. This is very hard to too in an alive individual as the heart is constantly beating and moving. The needle is inserted on the left side of the xiphoid process aiming towards mid clavicle where you insert it, hoping that you get into the pericardial cavity, without hitting the heart muscle itself. If this is done successfully, you can withdraw some of that fluid, significantly reducing the pressure in the heart, helping to restore the expanding function of the heart.

What are the 3 things that open into the right atrium? what opens into the left atrium? how does blood travel out of the heart?

INPUT TO HEART The venous input into the heart comes from the superior vena cava, inferior vena cava, and coronary sinus. These are the 3 things that open into the right atrium The pulmonary veins open into the left atrium OUTPUT OF HEART The output is either the pulmonary truck on the right side or the aorta on the left side.

What is the function of the chordae tendineae? papillary muscles?

In the image we can see the interventricular septum, the AV valve, papillary muscles, and all of the little white strings are the chordae tendineae. The chordae tendineae are attached to large projections that come out of the of the ventricular walls called papillary muscles. The chordae tendineae and the papillary muscles function together to keep the AV valve cusp closed when the heart contracts in systole. The muscle on along the wall itself would be the trabeculae carneae.

Which of the following is not a role of the pericardium? a. it facilitates heart contractions b. in prevents overfilling of the heart with blood c. in anchors the heart to surrounding structures d. in protects the heart

a. it facilitates heart contractions

The structure located in green is the: a. aorta b. pulmonary trunk c. superior vena cava d. inferior vena cava

c. superior vena cava

What are the names of the internal smooth muscular ridge that divides the right atrium? fossa ovalis crista terminalis right auricle sulcus terminalis septum primum

crista terminalis

The trabeculae carneae are located in the: a. endocardium b. atrium c. epicardium d. ventricles

d. ventricles

The sinoatrial node is located within that walls of which of the following chambers? left atrium left ventricle right atrium right ventricle

right atrium

What are the four functions of the Pericardium?

1. fixes the heart into position 2. prevents overfilling 3. lubrication 4. protection from infection

talking another look at the conduction system of the heart - what is the pathway? what occurs in a transplanted heart?

Just looking at the conduction system again. It starts in the SA node. It is sent to the AV node, to the bundle, and then to the bundle branches, and then to little fibers out in the walls of the ventricles called purkinje fibers. Because of this conduction system, the heart does not need to be innervated by nerves. It does not have to have autonomic innervation. When a heart is taken out of one person and place in another is will still beat, but it will not be able to respond to physiological changes that occur using autonomic innervation. It can still respond to medications and hormones, but there is no parasympathetic or sympathetic innervation to that transplanted heart. But if the electrical conducting system of the heart is still functions then the pt with the transplanted heart should be relatively okay.

What supplies the left atrium with blood? Does it receive oxygenated blood or deoxygenated blood? what is the structure of the left atrium?

The left atrium receives oxygenated blood from the lungs via four pulmonary veins. The left atrium has a smooth interior except for pectinate muscles in the left auricle. The walls of the embryonic pulmonary vein and four of its tributaries are incorporated into the smooth part of the left atrium, whereas the left side of the embryonic atrium contributes to the development of the muscular portion. Oxygenated blood enters the heart through the pulmonary veins and is dumped into the left atrium. The left atrium is completely smooth, except for the auricle where you do have a little bit of pectinate muscle. The left atrium does not really have the ability to contract. Its position and gravity do most of the work for the heart. Therefore, the left atrium is usually not very big. It is a filling chamber.

The left ventricle receives blood from? how does blood enter the left ventricle? what is the difference in size between the right and left ventricle? why are they different sizes? what is the aortic vestibule? how does blood exit the left venticle?

The left ventricle receives blood from the left atrium through the left atrioventricular orifice. - Guarded by the mitral valve. The internal surface of the left ventricle is also characterized by the presence of trabeculae carneae, but they are finer and more numerous than the RV. The wall of the left ventricle is two times as thick as the wall of the right ventricle. The part that leads into the aorta is smooth-walled and called the aortic vestibule. The aortic valve is a semilunar valve guarding the ascending aorta. Blood flowing through the left ventricle takes two right turns (around the anterior cusp) resulting in a 180° change in direction. Blood travels from the left atrium down into the left ventricle through the left atrioventricular orifice which is the opening of the mitral valve (also called the left AV valve or the bicuspid valve). The left ventricle also has trabeculae carneae in it, which tends to be finer and higher in quantity than in the right ventricle. The left ventricle tends to be twice the size as the right side as the right ventricle is only pumping to the lungs, and unless the individual has some sort of lung diseases, it is pumping against a lot less resistance than the left side. The left ventricle is pumping blood to the entire body, therefore there is a lot more resistance than on the right side. So blood comes in through the left AV valve, down where it almost has to make a 180 degree turn to get up and out. The part of the left ventricle that is sort of cone shaped leading up to the aorta is called the aortic vestibule. blood travels through it and out of the aortic valves. Looking at the difference between the shape of the AV valves and aortic valves (which are also shaped like the pulmonary valves) you can see there is a difference in shape.

What is the structure of the fibrous pericardium? parietal serous layer? what is the other name for the parietal serous layer? does it surround the entire heart?

•The fibrous pericardium is inelastic and functions to retain the heart in position and limit its distension—it prevents sudden overfilling. •The parietal layer of the serous pericardium is closely adherent to the fibrous pericardium. •The visceral layer of the serous pericardium is more loosely bound to the heart and is also called the epicardium. •The heart is completely invested in epicardium except the posterior, irregular area between the venae cavae and pulmonary vv. where myocardium contacts fibrous pericardium. Here we are looking at a higher magnification of the layers. We can see the fibrous pericardium. As she mentioned it is not very stretchy. One of its jobs is to keep the heart it position. It is actually tied down to the diaphragm and at the top to the tunica adventitia which is the otter layer of the great vessels, which are things that are coming into and out of the heart. At the top it becomes continuous in a way with the connective tissue that surrounds the aorta, pulmonary trunk, and superior vena cava. The fibrous layer also prevents the heart from overfilling. You do not want to get so much blood into the heart that when it contracts you can't pump it out. You want to get almost all of the blood out with each contraction. Therefore the fibrous layer holds the heart into its position and prevents overfilling. The parietal serous layer is stuck to the undersurface of the fibrous layer. They are very difficult to separate. The parietal layer then wraps around and it reflects onto the heart as the visceral serous layer. The other name of this layer is the epicardium. It is a layer that had some fat in it. And all of the little vessels that supply the heart itself, which we will talk about next week, as well as little branches of nerves that are going to the heart are out in the epicardium. The epicardium completely covers the heart except for one area on the back of the heart where the two vena cava are coming in. In this area on the back of the heart, you do not have that visceral serous layer (epicardium). Instead, you have the heart muscle itself (the myocardium), right in contact with the fibrous pericardium. This is an artifact of how the heart folds when it develops.

How is the interatrial septum formed? what occurs when the baby is born and the lungs inflate? what is a atrial septum defect?

1.In the fetus, lungs are not inflated 2.Formation of 1st septum (septum primum) 3.Formation of opening (foramen or ostium primum) before septum primum fuses 4.Formation of septum secundum & foramen/ostium secundum (foramen ovale) 5.A "flap valve" is created 6.Blood can pass from right atrium to left atrium and bypass the lungs Let's talk a little about how the interartial septum is developed. Looking at the top left image. If we think back to the box. We can see the endocardial cushion. And we would like to build a wall that connects to it from above to divide the right and left atrium. We will also do the same thing for the ventricles that attaches to the endocardial cushion from below. We want to separate these areas so that the right side pumps to the lungs and the left side pumps to the body. The problem is in utero, you have to figure out a way to prevent sending blood to the lungs as they are not being inflated. Therefore, when building this septum between the two atrium, you have to build it with a hole in the middle so that blood can travel between the two atrium, preventing blood from being sent to the lungs. This hole makes the wall very hard to build. Since we need a hole in the interatrial septum we build it in two stages. We start by building the septum primum, which is the 1st septum (or first wall). We cannot let this septum primum conntinue all the way down to the endocardial cushion as blood would not be able to get from the right atrium to the left atrium, and it would completely defeat the purpose. As we are building the septum primum and it starts to approach the endocardial cushion, we want to form a hole in it. In the inital development of this wall the opening between the septum primum and the endocardial cushion is called the ostium primum. Ostium means opening. As the septum primum is being built, we are wanting to make the ostium primum smaller and smaller and essentially are wanting to get rid of it all together so that there can be an attachment to the endocardial cushion. But in order to do this we need to replace the ostium primum with something so that blood can still get from the right atrium to the left atrium. To do this we punch a second hole in it called the ostium secundum. We then let the septum primum connect to the endocardial cushion, so that the only place blood can get through the two atrium is through the ostium secundum. So now blood can come into the right atrium from the mother, and travel through the ostium secundum, which is the hole in the middle of the septum primum, and travel into the left atrium to be sent to the left ventricle and then to the rest of the fetus's body. We then build a second septum called the septum secundum which creates this little flap valve. So that when blood comes into the right atrium it can come in through the foramen ovale where is can push the septum primum backwards so that blood can travel to the left atrium. And this is essentially what happens in the fetus's hard in utero. This is awesome in utero. But now we have a second problem. Once the baby is born and the lungs now need to inflate we now need to shut this hole as we do not want blood to travel backwards through the foramen ovale into the right atrium and mix with what will now be deoxygenated blood. once the baby is born we do NOT want blood traveling from left side to right side or vise versa. We need to shut the foramen ovale. Were we run into challeneges with closing the foramen ovale is when the second septum (septum secundum) is too short. When the septum secundum is being build there should be overlap over then the ostum secundum, so that when the baby is born and the lungs inflate, the pressure change can push the septum primum and the septum secundum together fusing the two, closing the foramen ovale and ostium secundum, closing off the opening between the right and left atrium. If the septum secundum is build too short, and there is no overlap over the ostum secundum, when the lungs inflate once the baby is born, the opening is unable to be closed, leaving the baby with a hole between the right and left atrium. This is known as a atrial septum defect.

What is a Ventricular Septal Defects (VSDs)? when does it require surgical intervention?

25% of all congenital heart defects Opening between L & R ventricles, associated shunting of blood Most VSDs occur in muscular portion (these spontaneously close) Membranous defects are more commonly corrected surgically A Ventricular Septal Defects is a hole in the Interventricular Septum. It accounts for 25% of congenital heart defects. If the hole is big enough that there is a lot of mixing of blood between the two ventricles it will need to be surgically closed. Most of the kids that have a VSD, the hole is found in the muscular part of the Interventricular Septum. These holes, unless they are huge, tend to close on their own. If the VSD is up in the membranous part of the Interventricular Septum, it has to be surgically closed, as they do not seem to have the capacity to repair themselves. Muscle can hypertrophy (grow), but the membranous part cannot.

A 24-year-old man presents to the emergency room with a stab wound to the left chest at the 4th intercostal space. The patient is hemodynamically unstable, and the trauma attending is concerned that there is penetrating trauma to the heart. Which cardiovascular structure is most likely to be affected by such a wound? 1. Left atrium 2. Left ventricle 3. Right atrium 4. Right ventricle 5. Aorta

4. Right ventricle DO NOT be tricked into choosing the left ventricle since the stab is to the left of the midline. Remember that the right side of the heart is oriented towards the front. The left ventricle sits mostly towards the back of the heart.

What are the two parts of the Interventricular Septum?

Again we have that Interventricular Septum between the two ventricles. Most of which is the muscular part. There is a little bit of membranous part of Interventricular Septum towards the top. the membranous part would be the part in that is attached to the endocardial cushion, to make the Interventricular Septum. If a hole forms in the Interventricular Septum between the two ventricles it is called a Interventricular Septum defect. Next week we will talk extensively about these defects.

What is a patent foramen ovale? what occurs in the hole is small? large? what does are the consequences of a large patent foramen ovale?

As many as 25% of individuals have an atrial septal defect. If it is too large, it allows O2 blood to be shunted to the right atrium and resulting in an overloading of the pulmonary system. Subsequently, the right atrium, right ventricle and pulmonary trunk will become enlarged. Some children are born with a "hole in their heart". Sometimes this hole is a atrial septal defect. 25% of children born with congenital heart abnormalities are born with a atrial septal defect. There are different types of atrial septal defects. One type is called a parent foramen ovale. The foramen ovale does not close, therefore blood mixes from the left side to the right side. The left atriums pressure after birth is higher than the pressure in the right atrium, therefore blood flows to the area of least resistance, which is into the right atrium. If the opening is small, and there is minimal mixture between oxygenated blood and deoxygenated blood, surgeons usually do not do anything. But, if the opening is large, and there is a large amount of oxygenated blood traveling into the right atrium and mixing with deoxygenated blood, it can start to overload the right side of the heart. Therefore, it results in an enlargement of the right atrium, right ventricle, and pulmonary truck. As a result, the heart ends up sending too much blood to the lungs, overloading the lungs. The child then starts out with one problem which is a hole that does not close between the two atrium, and they end up with many problems such as the enlargement of the right side of the heart and pulmonary truck, as well as, fluid build up in their lungs. If the hole is large enough and there is a large amount of shunting from the left atrium to the right atrium, surgery is required to close the foramen ovale.

What are the pressure differences between the right atrium and left atrium before birth? what about after birth? what does this pressure difference after birth cause? what is formed after birth between the two atria?

Before birth you have the right atrium under high pressure as the lungs are not inflated. Since the lungs are not inflated there is a lot of resistance as we do not want blood traveling that way. Therefore, this resistance increases the pressure in the right atrium so that blood can be forced through the foramen ovale into the left atrium where there is lower pressure. Even through the left atrium is pumping systemically, in utero, the left atrium has a lower pressure than the right atrium, therefore blood wants to travel to the area of lower pressure, and into the left atrium. Blood is traveling down the pressure gradient into the left atrium. After birth, the lungs inflate. Now the resistance on in the right atrium, and hence pressure, is MUCH lower than the left atrium. Therefore, the right atrium is pushing against a much higher pressure in the left atrium, therefore this resistance of blood to flow from the right atrium to the left atrium is prevented as the increase in pressure of the left atrium forces the foramen ovale closed. As long is there is enough overlap between the septum secundum and septum primum, the two will fuse. When this is done, the little impression the foramen ovale leaves becomes the fossa ovalis.

In a fetus there are two built in lung bypasses - what are they? what do they become once the baby is born?

In a fetus there are two of these built in lung bypasses. 1. foramen olvale - an opening between the right atrium and left atrium. When the baby is born this opening is shut and it becomes the fossa ovalis. 2. ductus arteriosus - an opening between the trunk of the pulmonary artery and the descending aorta. When the baby is born it shuts and becomes the ligamentum arteriosum

What is pericarditis? what sensory information does is cause our body to perceive? what are the possible causes of pericarditis?

Inflammation of the pericardium. Inflammation usually causes chest pain. The sharp chest pain associated with pericarditis occurs when the irritated layers of the pericardium rub against each other. Possible causes: -Viral, bacterial, fungal, and other infections -Trauma such as a fracture of the sternum that tear or irritate the pericardium. -Heart attack and heart surgery (if there is a surgery that resulted in the opening of the pericardium, like a CABG operation, it can result in irritation of the pericardium, resulting in pericarditis.) -Kidney failure, HIV/AIDS, cancer, tuberculosis -Autoimmune disorders such as lupus, scleroderma and rheumatoid arthritis (chronic pericarditis) You can have inflammation of the pericardium which is called pericarditis. This usually results in sharp chest pain. So this is a visceral structure, but the pericardium around it is not treated as a visceral structure, but rather like body wall. The phrenic nerve is a somatic nerve so the information that it carries back is perceived as if it is somatic pain. Therefore, it is very sharp and very located pain. The occurs when there is rubbing of the heart and its visceral pericardium up against the parietal layers. Again, the visceral pericardium is NOT sensitive the pain, but the parietal layer is. SO when the heart rubs up on the inside of it, it produces pain sensations. There is lots of things that can cause pericarditis.

External Heart Anatomy—Posterior View; what can be seen?

Looking at a posterior view of the heart. We can see the superior and inferior vena cava. Between the two is the right atrium. We can also see the third structure that opens into to the right atrium which is the coronary sinus. It is carrying deoxygenated blood from the heart muscles itself and dumping it into the right atrium. We can also see the left atrium and pulmonary veins. There are usually four pulmonary veins, but sometimes people only have one on one side and two on the other. We can also see the Posterior interventricular groove. Again this is a place where cardiac veins and coronary arteries are sitting as the run against the heart.

External Heart Anatomy—Anterior View: What are the three things that bring blood back to the heart? where is this blood coming from? where is it dumped into? is it deoxygenated or oxygenated? what are the two main grooves found on the heart? where are they located?

Looking at the external anatomy. Veins are colored in blue and arteries color in red. But remember the pulmonary truck is carrying deoxygenated blood so it should also be blue. The superior vena cava is bringing all of the blood from above the diaphragm into the right atrium. So the thoracic cavity - both front and back, both upper limbs, and the head and neck. The inferior vena cava is bringing all the deoxygenated blood back for the right atrium that is below the diaphragm. And the coronary sinus, which we cannot see in this image, is bring deoxygenated blood from the heart muscle itself back to the right atrium. The right atrium kinda looks like a pigs ear and it has a part of it called the right auricle (auricle means ear). The atrium is a compartment of the heart whereas auricle is a small out-pouching of the atrium. Right next to the superior vena cava is the aorta. It has a ascending part, an arch, and then in the back of the heart there is a descending part of the aorta. Next to the aorta is the pulmonary truck which divides into the left and right pulmonary arteries which carry deoxygenated blood from the right side of the heart to the lungs. The pulmonary truck sits more towards the front and the aorta sites a little bit towards the back. But as the aorta comes up to form its arch they sort of change positions. The pulmonary truck comes out of the right ventricle. The right and left ventricle meet at the apex of the heart. The left ventricle sits above the apex. Between the two ventricles is an interventricular groove. There is one on the front between the two ventricles called the Anterior interventricular groove, and one of the back between the two ventricles called the posterior interventricular groove. Arteries and veins sit inside these interventricular grooves. There is another set of grooves between the atrium and ventricles called the Atrioventricular groove (sometimes called the coronary groove). Vessels also sit and travel through these grooves as well. We can also see the left auricle. You cannot see the left atrium from the front. It is on the back of the heart. We can also see the ligamentum arteriosum. In a fetus it is open and called ductus arteriosus. It is one of the bypasses that the heart has for the lungs. The lungs are not inflated in a fetus, therefore you do not want to send blood to the lungs. The mother is sending oxygenated blood to the fetus. It's the job of the fetus's heart to get that blood out to the fetus's body. It does not have to oxygenate that blood.

We can also think of our heart as a house - when we do this what do we end up with?

Or think of the heart as a house with: •4 Rooms (Chambers) •4 Doors (Valves) •4 Big Hallways (Vessels) •4 Small Hallways (Vessels) We can also think of our heart as a house with four rooms. In terms congenital problems that occur, can then be though of as architectural problems. Coming into the right atrium we have our superior and inferior vena cava. The only thing you can't see in this image is the coronary sinus. We then see the tricuspid valve which is the right atrial ventricular valve. It allows blood from from the right atrium into the right ventricle. We then see outflow of the right ventricle through the pulmonary valve into tho pulmonary arteries. This is all in blue as it is all deoxygenated blood. On the left side we have blood coming back from the pulmonary veins into the left atrium. Blood travels from the left atrium into the left ventricle through the mitral valve, which is the left atrial ventricular valve (it is also known as the bicuspid valve bc it has two cusp). Blood then flows from the left ventricle into the aorta through the aortic valve. This is all in red as it is oxygenated blood. If you look closely you can see that the first thing that comes off the aorta is the coronary arteries which send blood to the heart itself. Later we will look closely at the aortic valve and we will see little openings in the aortic valve that are for the left and right coronary arteries. That is the first thing the heart supplies is itself. These valves are designed so that even when the heart is relaxed and not pushing blood out to the aorta, there is still blood that is kinda pooled and siting around so that you can keep blood flowing in the coronary arteries even if the heart is not pumping.

Parasympathetic Cardiac Innervation

Parasympathetic innervation is via preganglionic fibers located in the vagus nerve. Presynaptic parasympathetic fibers contribute to the cardiac plexuses. Postganglionic cells are located in the cardiac tissue (atrial wall and interatrial septum near the SA and AV nodes and along coronary arteries). Postsynaptic fibers end in the SA and AV nodes and directly on the coronary arteries. Parasympathetic stimulation is responsible for decreasing heart rate, force of contraction, and constricting coronary arteries. Parasympathetic Cardiac Innervation is the opposite of sympathetic Cardiac Innervation. All of the Parasympathetics are in the vagus nerve. The vagus nerve leaves the brain, travels down the neck, and as it passes down into the thorax, it is going to send off presynaptic branches (bc remember we really do not see postsynaptic parasympathetic branches), that contribute to that same cardiac plexus. The parasympathetics travel most of the same places as the sympathetics - around the SA node, AV node, and coronary arteries, but they just have the opposite effects. They slow down heart rate, decrease the force of contraction, and even constrict the coronary arteries a little. The preganglionic parasympathetic nerves from the vagus will synapse with little ganglia that are in the wall of the heart itself. So we never see the postganglionic parasympathetic nerves.

Sympathetic Cardiac Innervation

Preganglionic sympathetic neuron cell bodies are located in the lateral horns of spinal cord segments T1-T5. Postganglionic cells are located in the cervical and superior thoracic paravertebral ganglia. The postsynaptic fibers are carried in (thoracic) cardiopulmonary splanchnic nerves, contributing to the cardiac plexus and ending in the SA and AV nodes and in relation to the termination of parasympathetic fibers on the coronary arteries. Sympathetic innervation is responsible for increasing heart rate, impulse conduction, force of heart beat, and blood flow in coronary arteries. sympathetic preganglionic neurons start out in the lateral horn of the spinal cord and exit through T1-T5 segments. They leave out through the ventral root considering they are motor neurons and go out to the paravertebral ganglia. They can run up into the cord too synapse with the ganglia, or they can synapse at the level at while they leave the spinal cord. The postsynaptic fibers leave the paravertebral ganglia, and since these are fibers that are going to a visceral structure, they are called splanchnic nerves, also called cardiopulmonary splanchnic nerves. They travel to the heart and the lungs. They travel through a plexus over the top of the aortic arch and synapse along cells of the SA node and AV node, and even into some of the cells in the coronary arteries. Their job is to increase HR by speeding up the conduction in the conduction system. Making the heart beat harder and to dilate the coronary vessels, increasing blood flow to the muscles of the heart.

External Anatomy of the Heart

So we have finished talked about the pericardium, and now we are going to start talking about the external anatomy of the heart and move internally. This imagine shows you the where the heart is in someone who is in anatomical position. We see the manubrium of the sternum. At the base of the menubrium is where the sternal angle is found. Therefore, everything above the sternal angle is the superior mediastinum. We see the superior vena vaca. The ascending aorta and the arch of the aorta. We cannot see the descending aorta, as it is tucked behind the heart in the posterior mediastinum. We can also see the pulmonary truck which splits into the left and right pulmonary arteries. We can also see the pulmonary veins on the right side below the left pulmonary artery. Remember that the pulmonary arteries travel away from the heart and they carry deoxygenated blood. This is an exception to all other arteries in the body. In this picture the pulmonary arteries are colored in blue just as the superior vena cava is as they are carrying deoxygenated blood. The pulmonary veins which are found on the back of the heart are kinda peaking out below the left pulmonary artery are color pinkish as they are carrying oxygenated blood towards the heart. This is also an exception to all other veins in the body. We can also see the heart which has to kinds of chambers. 2 atria which are the filling chambers and 2 ventricles. In the image we can see the right atrium, and the ventricles. We can also see the apex of the heart which is where the left ventricle meets the right ventricle. Most of the heart, especially the right atrium and right ventricle, sit behind the body of the sternum which helps protect it. If you move away from the sternum out into the intercostal spaces of the right side of the heart, there is not a lot of stuff to hit if one were to be stabbed with a knife. If you where to stab someone through the 4th intercostal space on the right side, you would have to be right up against the body of the sternum to hit the heart. Now the left side is a little different. If your were stabbed on the left side of the body through the 4th intercostal space next to the body of the sternum you would hit the RIGHT ventricle. The heart is rotated so that the right side of the heart sort of faces forward, and the left side is tucked around towards the back. Therefore, most of what you see for the front of the heart is mostly the right ventricle. You would have to get way out of the edge to hit left ventricle. This will most likely be a test question.

What valves are open during diastole? systole?

The function of the atrioventricular valves is to prevent back flow into the atria during ventricular contraction. Papillary muscles and chordae tendineae prevent the cusps from prolapsing into the atria. One can look at the valves of the heart and determine if the heart is in diastole or systole. Diastole is a relaxed heart, as the heart is filling. During diastole the AV valves are open. Blood is opening in above them into the atrium, through the open AV valves, and into the ventricle. The semilunar valve, pulmonary valve, and aortic valve are closed. When you go into systole, the heart is contracting, causing the AV valves to slam shut, as you do not want back flow of the blood into the atrium. And then the pulmonary and aortic valve open so that blood can lead the heart. On the exam, be prepared to look at one of these images and determine if the heart is in systole or diastole.

What is the role of the interventricular septum? what are the two parts of the interventricular septum? where does blood go after it leaves the right ventricle? how does the blood exit the right ventricle?

The interventricular septum has two parts: - Muscular part - Membranous part that is superior and posterior - IV septum stiffens during contraction (systole) The pulmonary valve is a semilunar valve guarding the pulmonary trunk. Blood flowing through the right ventricle from right AV valve to pulmonary valve follows a U-shaped path, changing direction about 140° In the image we can see the interventricular septum which divides the right ventricle from the left ventricle. It has two parts to it. A muscle part which is about 90% of it. This part of the interventricular septum extends from the apex of the heart, almost all the way up to the endocardial cushion. And then the upper part of the interventricular septum is the membranous part. This part of the interventricular septum is a little more superior and posterior located. The reason we care about the location is because we can get differences in the in kinds of holes one can get in the heart, depending upon whether the hole is in the membranous part of the interventricular septum or the muscle part. The interventricular septum stiffens up as the heart contracts, giving the blood in the heart something to push against, so that when blood travels down from the right atrium into the right ventricle through the atrioventricular orifice, it makes a U shaped turn hitting the rigid septum, forcing it out of the right ventricle through the pulmonary valve, which is called a semilunar valve and it is difference in its shape a function when compared to AV valves. Semilunar valves do not have papillary muscles or chordae tendineae.

How many cusps does the left AV valve have? what is the other name of the left AV valve? what is interesting about the left AV valve? what can occur if there is prolapse of the AV valve?

The mitral valve has two cusps (bicuspid valve): -Anterior cusp -Posterior cusp Papillary muscles -Anterior -Posterior Chordae tendineae The mitral valve is the most commonly diseased of the valves of the heart. Nodules can form on the cusps resulting in turbulent flow. Prolapse of it may occur in as many as 7% of females. Hemodynamics associated with valvular prolapse can erode the endothelial surfaces of the valve and predispose a patient to endocardial infections. These infections occur when transient bacteremias seed abnormal endothelial surfaces. Looking at the Mitral Valve which is the left AV valve. It has two cusp - an anterior and posterior cusp. Therefore, it has an anterior and posterior papillary muscle that attaches to the cusp through chordae tendineae. But what is interesting about the Mitral Valve is that it is the most commonly diseased valve of the heart. You can have little nodules or bumps that form on the left AV valve. Also if someone has an infection, sometimes it can damage the endothelium that lines the left AV valve resulting in scaring. Both of these issues prevents the valve from closing completely which results in a little bit of prolapse and back flow, therefore there is regurgitation of blood into the left atrium. This is much more common in females. If you have prolapse of left AV valve, the hemodynamics of it can damage and scare the valve, predisposing that pt to an endocarditis which is an infection or inflammation of the endocardial lining of the inside of the heart. Therefore, pt that have issues with left AV valve prolapse frequently see their PCP to make sure that any type of systemic infection they might have does not travel and infect the heart valves.

What is Pericardial Effusion? what does it result in?

The presence of an abnormal amount of fluid and/or an abnormal character to fluid in the pericardial space. Because of the limited amount of space in the pericardial cavity, fluid accumulation leads to an increased intrapericardial pressure which can negatively affect heart function (cardiac tamponade). It can be caused by a variety of local and systemic disorders, or it may be idiopathic. When there is fluid build up in the pericardial cavity resulting in pericardial effusion. This build up of fluid causes an increase in pressure inside of the pericardial cavity. If the pressure becomes high enough, it makes it very hard for the heart to expand, as it now has to expand against the pressure of the fluid that is surrounding it, resulting in decreased heart function which is called cardiac tamponade.

What are the two Semilunar Valves and what is their structure? what is interesting about the aortic valves? do the Semilunar Valves have chordae tendineae and papillary muscles?

The pulmonary and aortic valves are tricuspid semilunar valves: They have three cup- like cusps that prevent back flow into the ventricles during ventricular relaxation. They are not associated with chordae tendineae and papillary muscles. We are now going to talk about the Semilunar Valves, and their name comes from their shape as they are kind of half moon shaped. They are different is structure form the AV valves. The Semilunar Valves have a sort of bucket shape to them. The edges of the valves are called lunules. And then in the middle of the valve there is a thickening called a nodule. When the Semilunar Valves are closed the three nodules come together in the center. Another things that is interesting in the aorta specifically, above the right and left cusp, there are little openings. These holes are the openings to the left and right coronary arteries. When the heart is in systole, and the heart is contracting, the Semilunar Valves are open. When the heart relaxes and goes into diastole, the Semilunar Valves shut. But in the aortic valves, there is a tendency for the last amount of blood that is ejected into the aorta, which has not made it all the way up to the arch yet, to fall backwards, as there is no pressure from underneath it to push it forward. This last amount of blood then gets caught in the aortic valves, and pulls in the cusp. Therefore, even when the heart is relaxed, the aortic valve cusp can fill with blood, which can then flow out through the openings into either the right or left coronary artery. SO even when the heart is relaxed, you still have oxygenated blood traveling to the heart muscle itself.

Where is each part of the conduction system in the heart located? what is the pathway of the conducting system? where does it start and end? what is the final result of the conduction system?

The rhythm of the heart is normally controlled by a group of automatically depolarizing specialized cardiac muscle cells called the sinoatrial node. The SA node is located in the wall of the right atrium near the opening of the superior vena cava and the superior end of the crista terminalis. - It initiates cardiac muscle contraction and determines heart rate. The AV node is located in the interatrial septum just superior to the opening of the coronary sinus. The AV bundle passes from the AV node in the membranous part of the interventricular septum and divides into right and left bundle branches The heart has its own internal conduction system, meaning you can take it out of one person and put it into someone else and it should work just fine. The conducting system consists of specialized cardiac muscle cells called myocytes that have been modified so that they can conduct an electrical signal. This signal starts up in the right atrium at the SA node. The SA node sits up at the end of the ridge that runs between the pectinate muscle and the smooth muscle part of the right atrium called the crista terminalis, right where the superior vena cava opens. The SA node initiates contraction of the heart muscle. From the SA node the signal is sent to the AV node which is still in the right atrium, sort of in the interatrial septum, just above where the coronary sinus opens. From the AV node the signal is sent to the bundle of his (also known as the AV bundle) which has two parts that split and run down either side of the interventricular septum. From the bundle of his the signal is sent out into the ventricles itself and into the papillary muscle, so that the signal that is coming from the AV node, goes to all of the muscle of the ventricles all at once so that there is a coordinated contraction. The ventricle walls contract at the same time the papillary muscle contract, putting tension on the Chordae tendineae so that the AV valves are pulled shut.

How many cusp does the right AV valve have? how are the papillary muscles attached to the AV valve? when is the AV valve open? closed? how does it open and close?

The right atrioventricular valve has three cusps (tricuspid valve): -Anterior cusp -Posterior cusp -Septal cusp Papillary muscles -Anterior (septomarginal trabeculum carries the right branch of the AV bundle to it) -Posterior -Septal Chordae tendineae If we look at the right AV valve which is also know as the tricuspid valve we can see that it has three cusps. An anterior, posterior, and septal cusp. The septal cusp is near the interventricular septum. Each cusp as one or two papillary muscle attached to it through chordae tendineae. There is a posterior, anterior, and septal papillary muscles. There is a connection that comes over from the interventricular septum over to the base of the right anterior papillary muscle called the septomarginal trabeculum. Part of the conduction system of the heart runs through it. It allows the conduction system to come over and innervate the papillary muscles so that they contract, when the muscle and ventricular wall contract. When the heart is filling during diastole, the AV valves are open. As blood comes into the atrium, is can travel through the AV valve into the ventricle as the heart fills with blood. The atrium tend to sit more on top, so gravity does a lot of the work. You only really get contraction of the atrial muscles towards the end of diastole, pushing the last bit of blood down into the ventricles. When the ventricles contract during systole, the AV valves close. During contraction, the pressure down in the ventricles increases, pushing blood against the close AV valves. You do not want the valve to open, allowing blood to go backwards into the atrium (this is called a prolapse or regurgitation). To prevent this, the job of the chordae tendineae, is to pull down on the cusp. So the walls of the ventricles are going to contract, increasing the interventricular pressure, while this is occurring the papillary muscles contract, pulling down on the chordae tendineae, causing them to pull down on the cusp of the valves, shutting them and preventing them from opening upward.

what are the two different parts of the right atrium that are divided based on their embryological origin? what is the area called that seperates these two areas? what is the role of the interatrial septum? what is the fossa ovalis? what does it a remnant of? what was its role in the fetus?

The right atrium can be divided into two parts based on morphology and embryological origin: •The sinus venarum is the smooth thin-walled posterior part that receives the venae cavae and coronary sinus. •The part with pectinate muscles (including the auricle). It is divided from the sinus venarum by the crista terminalis. The interatrial septum divides the right atrium from the left atrium. •The fossa ovalis is a remnant of the fetal foramen ovale and its valve. We are now going to start opening up the heart to see what the inside of these chambers look like. We are going to start with the right atrium. We are looking at the inside of the right atrium. The blue tube at the top is the superior vena cava. At the bottom we can see a blue tube which is the inferior vena cava. We can also see the opening for the coronary sinus. Those are the three major structures that open into the right atrium. When you open the right atrium up - half of it looks really smooth and half does not. This is because these two areas start out during embryological development as two different little dilations. The really smooth part is called the sinus venarum. This is where the vena cava open into as well as the coronary sinus. the other part of the right atrium as all of these little muscles in its walls called pectinate muscles. You find them over into the auricle as well. Where the pectinate part comes into contact with the smooth part of the right atrium there is a little ridge called the crista terminalis. It marks the division between the two embryologically different areas of the right atrium. Another thing we can see is an oval shaped structure called the fossa ovalis which is on the wall between the two atria. It is called the interatrial septum. When we were talking about the heart as a box and we were added the endocardial cushion and we attached the two vertical walls. Well this area would be the top vertical line that was separating the two atrium. The interatrial septum is the wall between the two atrium. In this wall there is a fossa ovalis. In the fetus this is an opening and it is called the foramen ovale. It is there so that oxygenated blood coming into the right atrium from the mother can be sent over to the left atrium. remember in the fetus we are not really sending blood to the lungs, therefore there is no reason to send blood to the right ventricle and then to the pulmonary arteries. So instead we send the blood that is received by the mother into the right atrium over to the left atrium so that it can then be sent to the left ventricle and to the rest of the fetus's body. The foramen ovale is a build in bypass for the lungs.

Right Ventricle receives blood from where? how does blood get into the right ventricle? what are trabeculae carneae and where are they found?

The right ventricle receives blood from the right atrium through the right atrioventricular orifice. - Guarded by the tricuspid valve. The irregular muscular elevations on the internal surface of the right ventricle are the trabeculae carneae. Now looking at the right ventricle. Blood come travels from the right atrium, through the right atrioventricular orifice which is the opening in the tricuspid valve. It is called the tricuspid valve because it had three cusps. It is also known as the right AV valve. As blood travels through the atrioventricular orifice, it enters the right ventricle. We will soon talk about the structure of the AV valves because they have what are called chordae tendineae (which means heart strings), which are the little white strings, that are attached to papillary muscles. When looking at the walls of the right ventricle, you can see ridges of muscle, which are called trabeculae carneae. They are pretty extensive in the right ventricle.

Looking down at the Semilunar Valves

This is what the two Semilunar Valves look like from above. Red is the aortic valve. the right coronary artery would be traveling out of the right aortic cusp and the left coronary artery out of the left aortic cusp.

In utero how does blood travel from the right atrium to the left atrium?

This is what we are trying to set up in utero. Blood comes in from the mother into the right atrium, travels through the foramen ovale, which is the hole in the septum secundum. As the blood travels through the foramen ovale it pushes the septum primum inwards into the left atrium, so that the blood can travel through the ostium secundum into the left atrium.

Visceral Afferent Cardiac Innervation

Visceral pain pathways for the heart follow the path of the sympathetics backward. Visceral sensory pathways that participate in reflex actions that lower blood pressure and slow the heart rate are carried in the vagus nerve (CN X). The vagus nerve does not transmit any visceral pain fibers originating in the heart. Visceral pain from the heart travels back with the sympathetics. It follows the sympathetic pathway back. There are visceral afferents that are not pain and they are mostly things that are participating in reflexes that usually adjust your blood pressure or change your heart rate. this information does travel back with the vagus nerve. But this information does not carry pain information, it is essentially homeostasis and monitoring information.

Diastole versus Systole - what is occurring with regards to the heart? what valves are open? shut?

When talking about Diastole versus Systole we usually talk about them in reference to the ventricles, but you can also specify them by the valves as well. During ventricular diastole, the heart is relaxed and filling with blood. The AV valves are open and the Semilunar Valves are closed. During systole, the heart contracts, the AV valves slam shut, and the Semilunar Valves open, as you are pushing blood out of the ventricles, either to the lungs or out to systemic circulation. Again be prepared to see one of the two images and state if the heart is in systole or diastole, and what valves are open vs. shut.

How are the pulmonary trunk and aortic outflow tracts developed? what does the pulmonary trunk valve end up with? what about the aortic valve?

When we build the heart the heart and we put in the interventricular septum, so that we can divide the two ventricles from each other, but we also have to divide their two outflow tracks. Initially the outflow track starts out as one tube as does the heart. But we need to divide that outflow track into an aorta and a pulmonary truck outflow track that are separate. Early in development there is one tube with a right and left cusp, and then a posterior and anterior cusp. As we divide the two ventricles by adding the interventricular septum we sort of push it up into the outflow tract to divide the two outflow tracks into aorta and pulmonary outflow. Early on when the two are leaving the left ventricle, The pulmonary trunk sits a little towards the front, and the aorta sit a little towards the back. But as they continue they sort of switch positions and the aorta moves more towards the front, and the pulmonary trunk towards the back. Because of this, the septum that separates the two outflow tract is in the shape of a spiral. This structure is very complicated to build, therefore it is very common for a congenital abnormally to occur within this septum. When this septum is being built you end up with a little rotation, so that the aorta ends up sitting slightly towards the back, and the pulmonary trunk towards the front. The right and left cusps are divided by the septum, therefore, both have a left and right cusp. But the pulmonary trunk will have an anterior cusp and the aorta will have a posterior cusp. In the bottom picture we can see the two coronary arteries coming out of the left and right cusp of the aortic valve that are designed to hold blood during diastole.

When you draw the heart as a large box what are the things that are added in order during embryological development?

You can draw the heart as a large box. You have venous input and arterial output. The venous input into the heart comes from the superior vena cava, inferior vena cava, and coronary sinus are the things that open into the right atrium. The pulmonary veins open into the left atrium. You then have output which is either the pulmonary truck on the right side or the aorta on the left side. - embryologically when you start to build the heart, this is what you start with. A tube essentially. It actually starts out as two tubes that come together a fuse. It then divides into four units - two atrium and two ventricles. the first thing that happens to accomplish this is that we add a block of tissue into the middle of the heart so that when you start building walls, they have something to attach too. This tissue is called endocardial cushion (ECC). This allows us to separate the heart into the right and left side. We then add two vertical walls that attach to the ECC. If the ECC does not form, you will not be able to separate the atrium and ventricles. We then build valves which are the green circles. We now have two chambers on top which are the atria and two chambers below which are the ventricles. we have inflow of blood into the atria and outflow of blood from the ventricles, and two valves that control the movement of blood from the atria to the ventricles.

Through which valve does blood enter the right ventricle from the right atrium? aortic pulmonary tricuspid mitral

tricuspid

What provides the pericardium with blood? what about drainage from the pericardium?

•Blood supply to the pericardium is via the pericardiacophrenic arteries, musculophrenic arteries, branches of the thoracic aorta (bronchial, esophageal, and superior phrenic) and coronary arteries (to visceral layer only). •Venous drainage is via pericardiacophrenic vv, internal thoracic vv., & azygos system. Most of the blood supply to the pericardium is going to come from the pericardiacophrenic arteries. Looking at the picture, remember we have the subclavian artery which is a branch of the aorta. It gives off an internal thoracic artery which gave off the anterior intercostals for the 1st through 6th intercostal spaces. The internal thoracic artery then split into the a superior epigastric artery which goes to the abdomen and a musculophrenic artery which supplied blood to the lower intercostal spaces. - well down in that area where you are running along the edge of the rib cage, the musculophrenic artery will send branches over to the pericardium. Most of them are going to come from another branch of the internal thoracic artery called the pericardiacophrenic artery. It is the artery in the middle of the heart that we can see in the left image. It sends lots of little branches to the pericardium. Additonally, any other large artery in the area, may also send a few branches to the pericardium. So anything coming off of the aorta, such as the bronchial arteries that are going to the lungs, esophageal arteries, and even little branches off of the internal thoracic artery as it passes and spits into the musculophrenic artery will supply blood to the pericardium.

How does the pericardium fix the heart into position?

•Fixes the heart in the mediastinum and limits its motion - this is due to its attachment to the diaphragm, the sternum and the tunica adventitia (outer layer) of the great vessels. So functions of the pericardium. We have already mentioned one of them. It fixes the heart into position. We can see in the picture that the fibrous pericardium is attached at the bottom to the central tendon of the diaphragm. This is sitting right behind the sternum. The pericardium holds the heart into position behind the rib cage which is going to be the most protective for it. This attachment to the diaphragm holds it into position. the other things we can see in the picture is the lungs, so we have our pleura. At the bottom along the diaphragm we see diaphragmatic pleura. When the pleura turns and comes up on either side of the heart it, which is the middle mediastinum, it becomes meditational pleura. We can also see the Phrenic nerve & the two vessels that run with are the pericardiacophrenic artery and vein. The phrenic nerve we know goes to the diaphragm for motor innervation, but we also learned last unit that it sensory innervation for the mediastinal pleura. That phrenic nerve and those two vessels sit kind of sandwiched between the fibrous pericardium on one side and the mediastinal pleura on the other. So if the phrenic nerve is going to give sensory innervation of the mediastinal pleura it is going to give sensory innervation for the fibrous pericardium as well. In addition, if those pericardiacophrenic vessels will provide blood to the fibrous pericardium as they provide blood to the mediastinal pleura. SO the fibrous pericardium holds the heart in the most protective position it can get it in inside of the thoracic cavity.

How does the pericardium prevent overfilling in the heart? how does it provide lubrication? protection?

•Prevents overfilling of the heart - The relatively inextensible fibrous layer of the pericardium prevents the heart from increasing in size too rapidly, thus placing a physical limit on the potential size of the organ •Lubrication - A thin film of fluid between the two layers of the serous pericardium reduces the friction generated by the heart as it moves within the thoracic cavity. •Protection from infection-The fibrous pericardium serves as a physical barrier between the muscular body of the heart and adjacent organs prone to infection, such as the lungs We have also talked about how the pericardium prevents the heart form overfilling. As we talked about, you do not want to put too much blood into the ventricles that when it contracts all of the blood is unable to get out. Therefore, we keep it rapped in a fairly non-distensible bag. But that also means that if anything gets into that pericardial cavity, like additional fluid, it can start to compress the heart. This is something called cardiac tamponade which we will talk about here soon. - Last unit we talked about things like pleural fusions where you have fluid of some kind inside the pleura cavity, well the same thing can happen to the pericardial cavity. This would result in a pericardial infusion. - So the fact that the pericardium holds the heart in place and prevents overfilling is good, but also means that if you get too much of fluid of anything else in the pericardium cavity, it cannot stretch, so the heart will be compressed as a result, resulting in lose of heart function. Other functions include lubrication. The serous fluid in the pericardium cavity provides this lubrication. It allows the heart to move inside of the pericardial cavity without friction. The last function is protection from infection. The pericardium acts as a physical barrier. If you have some sort of infection going on in one of the pleural cavities for example, it can get into the pericardial cavity, but the pericardium is going to slow it down. It makes it more difficult for pathogenic infection to move from some kind of pleural cavity or somewhere else in the thorax into the pericardium.

What nerve provides the pericardium with innervation? does every layer of the pericardium receive sensory innervation?

•Somatic sensory innervation to the fibrous and parietal layers is via the phrenic nerves (C3-C5). •Visceral sensory to the epicardium is via the cardiac plexuses (the epicardium is insensitive to pain). We have already kind of talked about blood supply and innervation. We are going to start will talking about the innervation which is the bottom picture. We can see the phrenic nerve which comes out of cervical segments 3, 4, and 5. It's going to come down and innervate the motor component for the bulk of the diaphragm, in addition to sensory expect of the outside edges. As the phrenic nerve is running down between the mediastinal pleura and the fibrous pericardium, it is going to provide sensory innervation to the fibrous pericardium and to the parietal layer underneath. The visceral pericardium is just like visceral pleura, as it is insensitive to pain, therefore it has no sensory innervation. It can send some information back to the brain with the autonomics that innervate the chest through the cardiac plexus. This will tell the brain things about the stretch and distention of the heart, but the visceral pericardium DOES NOT FEEL PAIN.