Chapter 19 - The Circulatory System: the heart (before you go on Q) Flashcards
- Distinguish between the pulmonary and systemic circuits and state which part of the heart supplies each one.
- Predict the effect of a pericardial sac that fits too tightly around the heart. Predict the effect of a failure of the pericardial sac to secrete pericardial fluid.
- Name the three layers of the heart and name their structural differences.
The three layers of the heart are the epicardium, myocardium and the endocardium. The epicardium (visceral pericardium) is a serous membrane of the external heart surface. It conisists mainly of a simple squamous epithelium overlying a thin layer of areolar tissue. In some places, it also includes a thick layer of adipose tissue whereas in other areas it is fat-free and translucent, so that the muscle of the underlying myocardium shows through. The largest branches of the coronary blood vessels travel through the epicardium. The endocardium is similar to the epicardium. it lines the interior of the heart chambers. it consists of simple squamous epithelium overlying a thin areolar tissue layer and has no adipose tissue. It covers the valve surfaces and is continous with the endothelium of the blood vessels. The myocardium is between the epicardium and endocardium. and is composed of cardiac muscle. It is teh thickest layer and performs the work of the heart. its thickness is proportional to the workload on the individual chambers. Its muscle spirals around the heart forming a myocardial vortex. When the ventricles contract they exhibit a twisting and wringing motion that enhances the ejection of blood.
- What are the functions of the fibrous skeleton?
The fibrous skeleton is a framework in the heart made of collagenous and elastic fibers. This tissue is especailly concentrated in the walls between the heart chambers, in fibrous rings around the valves and in sheets of tissue that interconnect these rings. Functions of the fibrous skeleton are**: 1. 1111 ** alves and openings of the great vessels. It holds these orifices open and prevents them from excessively stretching
- Trace the flow of blood through the heart, naming each chamber and valve in order.
- Blood enters the right atrium from the superior and inferior vena cava . 2. The flows through the right atrialventricular valve (tricuspid valve) to the right ventricle. 3. contraction from the right ventricle forces pulmonary valve to open and the blood goes to the pulmonary valve and into the pulmoary trunk..4. blood is distributed by right and left arteries to the lungs where it unloads CO2 and loads O2. 5.blood returns from the lungs it flows out of the pulmonary veins into the left atrium. 6. from the left atrium it flows theough the left atrialventricular valve (bicuspid valve) in to the left ventricle. 7. contraction of left ventricle simulatenous with step 3 forces aortic valve to open. 8. From the left ventricle it goes to the aortic valve to the ascending aorta. 9. blood in aorta is distributed to every organ in the body where it unloads O2 and picks up CO2. 10. blood return to the heart via venae cavae. nlood enbbb
- What are the three principal branches of the left coronary artery? where are they located on the heart surface? What are the branches of the right coronary artery, and where are they located?
The three principal branches of the left coronary artery (LCA) are: the anterior interventricular branch which travels down the anterior interventricular sulcus to the apex, rounds the bend, and travels a short distance up the posterior side of the heart. There it joins the posterior interventricular branch. This artery supplies blood to both ventricles and the anterior two-thirds of the interventricular septum. 2. The circumflex branch which passes down the left margin of the heart in the coronary sulcus. It gives off a left marginal branch. 3. left marginal branch passes down the left margin of the heart and furnishes blood to the left ventricle. The circumflex branch then ends on the posterior side of the heart and supplies blood to the left atrium and posterior wall of the left ventricle. The three principal branches of the right coronary artery (RCA) are: 1. right marginal branch which runs towards the apex of the heart and supplies the right lateral aspect of the right atrium and ventricle. 2.posterior interventricular branch which travels down the corresponding sulcus and supplies the posterior walls of both ventricles as well as the posterior portion of the interventricular septum. It ends by joining the interventricular branch of the LCA.
- What si the medical 1111111111cfdfsdgddssss7. What is the medical significance of anastomoses in the coronary arterial system?
anastomoses can give protection from myocardial infarction (MI) or heart attack by the points where the two arteries come together and combine their blood flow to points farther downstream. these points of converegence (anastemoses) provide alternative routes called collateral circulation that can supply the heart tissue with blood if the primary route becomes obstructed.
- Why do the coronary arteries carry a greater blood flow during ventricular relaxation than they do during ventricular contraction?
- contraction of the myocardium compresses the arteries and obstructs blood flow. 2. When the ventricles contract, the aortic valve is forced open and its cusps cover the openings to the coronary arteries, blocking blood from flowing into them. 3. When they relax, blood in the aorta briefly surges backward towards the heart. It fills the aortic valve cusps and some of it flows into the coronary arteries. In the coronary blood vessels, therefore, blood flow increases during ventricular relaxation.
- What are the three major veins that empty into the coronary sinus?
- the great cardiac vein - collects blood from the anterior aspect of the heart and travels alongside the anterior inteventricular artery. It carries blood fromt he apex to the coronary sulcus, then arcs around the left side of the hear and empties into the coronary sinus. 2. The posterior interventricular (middle cardiac) vein found int eh posterior interventricular sulcus, collects blood from the posterior aspect of the heart. It carries blood from the apex upward and drains in the same sinus. 3. left marginal vein travels from apoint near the apex of the left margin and also empties into the coronary sinus.
- What organelle(s) are less developed in cardiac muscle than in skeletal muscle? What one(s) are more developed? What is the functional significance of these differences between the muscle types?
The sarcoplasmic reticulum is less developed than in a skeletal muscle. It lacks terminal cisternae. The T-tubules are much larger than in skeletal muscle. During excitation of the cell they admit supplemental calcium ions from the extracellular fluid to activate muscle contraction. Cardiocytes also have large mitochondria They fill about 25% of the cell. Skeletal muscle mitochondria only occupy 2%. The heart makes little use of anaerobic fermemntation so it is not prone to fatigue.
- What exactly is an intercalated disc, and what function is served by each of its components?
An intercalated disc is connection that joins cardiocytes end to end by using thich connections. It has three distinctive features not found in skeletal muscles. 1. Interdigitating folds: plasma membrane at then end of the cell is folded somewhat like the bottom of an egg carton. The folds of adjoining cells interlock with each other and increase the surface area of intercellular contact. 2. Mechanical Junctions: cells are tightly joined by two types of mechanical junctions: the fascia adherens and desmosomes. The fascia adherens is the most extensive. It’s a broad band in which the actin and the thin myofilaments is anchored to the plasma membrane and each cell is linked to the next via transmembrane proteins. The fascia dherens is interrupted here and there by desmosomes. The desmosomes prevent the contracting cardiocytes from pulling apart. 3. Electrical Junctions: The intercalated discs also contain gap junctions, which form channels that allow ions to flow from the cytoplasm of one cardiocyte directly into the next. They enable each cardiocyte to electrically stimulate the neighbors. The entire myocardium of a the two atria and ventricles behaves almost like a single cell which is essential for effective pumping of heart.
- Cardiac muscle rarely uses anaerobic fermentation to generate ATP. What benefit do we gain from this fact?
Cardiac muscle is more vulnerable to an oxgen dificency than it is to the lack of any specific fuel. Since it makes little usse of anaerobic fermentation (the oxygen debt mechanism) it is not prone to fatigue. WHich is good because it can maintain it’s rythmn for a lifetime without fatigue.
- Where is the pacemaker of the heart located? What is it called? Trace the path of electrical excitation from there to a cardiocyte of the left ventricle, naming each component of the conduction system along the way.
The pacemaker of the heart is located in the right atrium under the epicardium near the superior vena cava. It is called the sinoatrial (SA) node. It’s a patch of modified cardiocytes. It initiates the heart beat and determines the heart rate. The path it takes is as follows: 1. the SA node fires, 2. Excitation spreads through the atrial myocardium. 3. AV node fires. 4. Excitation spreads down AV bundle.5. Purkinje fibers distribute excitation through ventricular myocardium.
- Why does the heart have a nerve supply since it continues to beat even without one?
Even thought the heart has its own pacemake, it does receive both sympathetic and parasympathetic nerves that modify the heart rate and contraction strength. without this nerve supply, the heart would be only at the rate of the pacemaker.
- Define Systole and diastole.
Systole is contraction of the heart and diastole is relaxation of the heart. These terms can refer to a specific part of the heart (ex: artial systole) but if no particular chamber is specified, they usually refer to the more conspicous and important ventricular action, which ejects blood from the heart.
