Anatomy and Physiology Review with Maryann Ivons The Cardiovascular System

Course Description This course describes the anatomy and physiology of the Cardiovascular System. It is designed for clinicians who desire to use the information in a clinical setting to better inform their understanding of the underlying processes of a clinical presentation.

Course Objectives At the end of this course students will: ❖ Be familiar with the structure of the cardiovascular

system. ❖ Describe the normal functions of cardiovascular system. ❖ Relate the structure and function to the clinical

presentations that they encounter in practice.

The cardiovascular system is like any pumping system. It consists of the pump, the tubing, fluids and the power source. In the this biological system the pump is the heart, the tubing consists of arteries and veins, the fluid is blood, and the power source is the nervous system.

The pericardial sac is a conical sac of fibrous tissue which surrounds the heart and the roots of the great blood vessels.

The pericardium has two layers. The outer layer is tough and thickened, loosely cloaking the heart, and is attached to the central part of the diaphragm and the back of the sternum (breastbone). The inner layer is double, with one layer closely adherent to the heart while the other lines the inner surface of the outer layer with an intervening space filled with fluid.

Cardiac Blood Flow

Right heart is the low pressure side of the heart. It receives returning deoxygenated blood from the body and returns it to the lungs. The walls of the right side of the heart are thinner then the left.

Left heart is the high pressure side of the heart and receives oxygenated blood from the lungs and pushes that out to the body. The walls of the left ventricle are thick and able to deal with the increased blood pressure that maintains a normal cardiac output

The valves of the Left heart are:

• Mitral valve; Between the left atrium and ventricle.

• Aortic valve; Between the left ventricle and the entrance to the aorta.

The valves of the right heart are

• Tricuspid valve; Between the right atrium and ventricle.

• Pulmonary valve; Between the right ventricle and the entrance to the pulmonary artery.

Cardiac muscle is composed of the contractile cells. Like skeletal muscle it has a striated appearance due to alternating thick and thin filaments composed of myosin and actin. Actin and myosin are contractile protein filaments, with actin making up thin filaments, and myosin contributing to thick filaments. All the cardiac muscle cell are capable of initiating a heart beat but there is an organized system to assure an orderly route of depolarization and repolarization in the heart muscle to facilitate adequate cardiac output.

The heart has built in fail safes in an attempt insure a continuous sufficient cardiac output. The sinoatrial node is the chief regulator of the beat but if that fails the atrioventricular node take over. If that fails then the ventricles try to maintain the beat. Each of these areas have an individual normal rate.

❖ Sinoatrial node: 60-100 beats per minute ❖ Atrioventricular node: 40-59 beats per minute ❖ Ventricular node: 20-39 beats per minute

Vessels of the Heart

❖ Arteries: muscular-walled tubes which carry mainly oxygenated blood from the heart to all parts of the body.

❖ Veins: Tubular branching blood vessel; especially that carry blood toward the heart. The blood is deoxygenated, except for the blood in the pulmonary vein.

❖ Capillaries: The smallest blood vessels connecting arteries to veins. These blood vessels carry oxygen and nutrients to individual cells throughout the body.

Capillaries play a vital role in the exchange of gases, nutrients, and metabolic waste products between the blood and the cellular tissues. Substances pass through the capillary wall by diffusion, filtration, and osmosis. Oxygen and carbon dioxide move across the capillary wall by diffusion. Fluid movement across a capillary wall is determined by a combination of hydrostatic and osmotic pressure. The net result of the capillary microcirculation created by hydrostatic and osmotic pressure is that substances leave the blood at one end of the capillary and return at the other end.

Blood is the fluid of the cardiovascular system.

To understand cardiac physiology it is important to have a basic understanding of blood pressure and the other parameters affecting cardiac hydrodynamics.

The job of the cardiovascular system is to deliver oxygen and nutrients to all the cells and return carbon dioxide and waste for disposal to their appropriate destinations. All of this is dependent on an efficient pump. The following must be considered.

❖ Adequate blood pressure ❖ Adequate circulating blood volume ❖ Normal stroke volume

Blood pressure is measured by two readings call the systolic and diastolic pressures. The systolic pressure is the pressure of the blood in the arteries when the heart pumps. The diastolic pressure is specifically the minimum arterial pressure during relaxation and dilatation of the ventricles of the heart when the ventricles fill with blood.

More than 120 over 80 and less than 140 over 90 (120/80-140/90)

The right ventricle the systolic pressure is normally in the 25- to 30-mm Hg range, with end-diastolic pressure of 5 to 7 mm Hg. The systolic pressure in the left ventricular should equal the systolic arterial pressure; the end-diastolic pressure is typically less than 10 mm Hg.

The stroke volume is the amount of blood pumped by the left ventricle of the heart in one contraction. A normal stroke volume is 60-100 ml/beat. A blood circulating blood volume is 4-5 L. Both ventricles of the heart have about the same stroke volume per beat although the right side pressure is considerably less then the left side.

Cardiovascular Anatomy and Physiology Review

Questions?

This anatomy and physiology review has been prepared for you by Maryann for the Trinity Health Hub. Copyright 2019 Maryann Ivons. Any use beyond

personal review requires specific written permission by the author.