Chapter 13 – Cardiovascular System

13.1 Introduction

Systemic Circulation – delivers blood to all body cells and carries away waste
Pulmonary Circulation – eliminates carbon dioxide and oxygenates blood (lung pathway)

Arteries - carry blood away from the heart
Veins - return blood to the heart

13.2 Structure of the Heart

Heart Size – about 14 cm x 9 cm (the size of a fist)

Coverings of the heart

Pericardium encloses the heart (like a bag) (visceral, parietal)
Pericardial cavity – contains fluid for the heart to float in, reducing friction

Wall of the Heart

Epicardium – outer layer, reduces friction
Myocardium – middle layer, mostly cardiac muscle
Endocardium – inner layer, blood vessels and Purkinje fibers

13.3 Heart Chambers and Valves

Atria - top chambers

Ventricles - bottom chambers

Septum - divides left and right side

Atrioventricular Valve (AV) - these valves are located between the atrium and the ventricle

Tricuspid - right side AV

Bicuspid - left side AV, also called mitral valve

Superior Vena Cava - vessel the returns blood to the heart from the upper body

Inferior Vena Cava - vessel the returns blood to the heart from the lower body

Coronary Sinus - indentation on the front of the heart

Chordae tendinae / Papillary Muscles - muscles and tendons that hold the heart valves in place

Pulmonary Trunk/Arteries - large vessel that splits into the left and right pulmonary arteries, these are the only arteries that carry deoxygenated blood

Pulmonary valve - controls the flow of blood into the pulmonary trunk

Pulmonary Veins - returns oxygenated blood from the lungs

Aorta - large vessel that delivers blood to the body

Aortic Valve - controls the flow of blood into the aorta

 Path of Blood Through the Heart

Quick Overview

1. Deoxygenated blood enters right atrium through the vena cava
2. Blood moves into the right ventricle
3. Blood goes out the pulmonary arteries and heads to the lungs
4. Blood returns from the lungs and enters the left atrium
5. Blood moves into the left ventricle
6. Oxygenated blood moves out of the left ventricle through the aorta and to the body

13.3 Heart Actions

Cardiac Cycle - once complete heartbeat

Systolic pressure / diastolic pressure

Systolic occurs when blood is forced out of the left ventricle, and the aortic valve OPENS...this is the high number on a blood pressure reading

Diastolic occurs when the aortic valve closes and the ventricle relaxes, this is the lower number of the blood pressure reading.

Average (Normal) Blood Pressure = 120/80
Average heart rate = 72 bpm

The cusps (flaps) of the bicuspid and tricuspid valves are anchored to the ventricle walls by fibrous “cords” called chordate tendineae, which attach to the wall by papillary muscles. This prevents the valves from being pushed up into the atria during ventricular systole.

*The device used to measure blood pressure is a SPHYGMOMANOMETER

Factors affecting blood pressure:

1. Cardiac Output
2.  Blood volume (5 liters for avg adult)
3.  Blood Viscosity
4.  Peripheral Resistance

ECG = electrocardiogram

- recording or electrical events that occur during the cardiac cycle

• P Wave – depolarization of the atria (atrial contraction – systole)
• QRS Complex – depolarization of the ventricles (ventricular contraction, systole)
• T Wave – Repolarization of the ventricles

Heart Sounds

- the opening and closing of the valves makes a characteristic "lub dub" sound.
- doctors use a STETHESCOPE to listen to the heart sounds, cardiologists are trained to hear abnormalities.

Cardiac Conduction System: Specialized cardiac muscle tissue which conducts impulses.

1. Sinoatrial (S-A) Node – “Pacemaker.” Posterior wall of the right atrium. Special muscle tissue that spontaneously generates (initiates) rhythmic impulses which spread through the myocardium. Cells of the S-A Node are “self-excitatory”
2. Junctional Fibers – carries impulses into the A-V Node. Also these slow down the impulse (smaller fibers)
3. Atrioventricular Node (A-V) – conducts impulses from the atria through the septum, to the ventricles. Slows the impulse further, giving atria time to empty and the ventricles time to fill. Found in the floor of right atrium, near septum
4. A-V Bundle – within the interventricular septum. A right and left branch transmits impulse to walls of the ventricles.
5. Perkinje Fibers – Begin about halfway down the septum. Branch throughout the walls of the ventricles and carry impulse rapidly throughout ventricles, stimulating contraction

Cardiac Output = Stroke Volume x Heart Rate

Regulation of the Cardiac Cycle – controlled by the cardiac center within the medulla oblongata. The cardiac center signals heart to increase or decrease its rate according to many factors that the brain constantly monitors.

Increased muscle activity = Higher oxygen demands = increase in heart rate
Higher Body temperature = increased heart rate; Lower body temp = lower heart rate
Blood level of certain ions - Potassium High = Lower heart rate; Potassium Low = Higher heart rate
- Calcium high = Higher heart rate; Calcium Low = Lower heart rate

Abnormal Heart Rhythms – Arrhythmias

Tachycardia = rapid heartbeat ( > 100 BPM)
Bradycardia = slow heartbeat ( < 60 BPM)
Fibrillation = rapid, uncoordinated unsynchronized heart rate. Atria (not serious. Ventricles (deadly)

SADS  = (Sudden Arrhythmia Death Syndromes  or  Sudden Adult Death Syndrome)

Interpreting ECGs

An ECG is printed on paper covered with a grid of squares.

Notice that five small squares on the paper form a larger square. The width of a single small square on ECG paper represents 0.04 seconds. A common length of an ECG printout is 6 seconds; this is known as a "six second strip."

Defibrillator- common treatment for life-threatening cardiac arrhythmia The device shocks the heart and allows it to re-establish its normal rhythm The device can also be used to start a heart that has stopped

Measuring Blood Pressure (LAB)

This lab outlines the procedure involved in taking a patient's blood pressure using a sphygmomanometer and a stethescope.

13.4 Blood Vessels : arteries, veins, capillaries

Arteries : strong elastic vessels which carry blood moving away from the heart. Smallest ones are arterioles which connect to capillaries .

Veins : Thinner, less muscular vessels carrying blood toward the heart. Smallest ones are called venules which connect to capillaries . Contain valves .

Capillaries : Penetrate nearly all tissues. Walls are composed of a single layer of squamous cells – very thin. Critical function: allows exchange of materials (oxygen, nutrients) between blood and tissues.

Control of Blood Flow:

Precapillary sphincters – circular, valve-like muscle at arteriole-capillary junction.

Vasoconstriction – narrowing blood vessel’s lumen (“passageway”)
Vasodilation – explanding blood vessel’s lumen

Blood flow through veins – not very efficient. Slow, weak “pushing” by arterial blood pressure is not much of a factor at all.

Important factors include:

1. Contraction of the diaphragm.
2. Pumping action of the skeletal muscles.
3. Valves in the veins.

* Blood Clots can occur if blood does not flow properly through the veins - can occur if a person does not move enough

Major Blood Vessels

Aorta - Ascending Aorta, Aortic Arch, Descending Aorta, Abdominal Aorta. The aorta is the largest artery. (leaves right ventricle)
Pulmonary Trunk – splits into left and right, both lead to the lungs (leaves left ventricle)
Pulmonary Veins – return blood from the lungs to the heart (connects to left atrium)
Superior and Inferior Vena Cava – return blood from the head and body to the heart (connects to right atrium)

Branches of the Aorta

Right and Left Coronary Arteries - supply blood to the heart itself
Brachiocephalic Artery branches into the Right Subclavian ( supplies blood to the arms) and the Left Common Carotid (bicarotid)
The common carotid then branches into the left and right carotid arteries which supply blood to the head
Left Subclavian Artery – supplies blood to the left arms

Note that the vessels are not symmetrical.

Disorders of the Circulatory System

1. MVP - mitral valve prolapse, the mitral valve does not close all the way; this creates a clicking sound at the end of a contraction. 

2. Heart Murmurs – valves do not close completely, causing an (often) harmless murmur sound. Sometimes holes can occur in the septum f the heart which can also cause a murmur 

3. Myocardial Infarction (MI) - a blood clot obstructs a coronary artery, commonly called a “heart attack”

4. Atherosclerosis – deposits of fatty materials such as cholesterol form a “plaque” in the arteries which reduces blood flow. Advanced forms are called arteriosclerosis. Treatment: Angioplasty, where a catheter is inserted into the artery and a balloon is used to stretch the walls open. A bypass can also treat clogged arteries, a vein is used to replace a clogged artery. Coronary bypass refers to a procedure where the coronary artery is bypassed to supply blood to the heart. (The phrase “quadruple bypass” means that 4 arteries were bypassed.)

Video Showing a Stent and Angioplasty (Mayo Clinic)

5. Hypertension – high blood pressure, the force within the arteries is too high. A sphygmomanometer can be used to diagnose hypertension

6. Stenosis - narrowing of one or more arteries that prevents or slows blood flow

7. Ventricular (Atrial) Septal Defect - often described as a hole in the heart, blood can leak between the two sides

Name: _____________________________________

Circulatory System Review Guide

1. How do you calculate cardiac output (formula)? _____

How much blood is contained in the average human? ________

2. Arteries carry blood ____________ from the heart.
Veins carry blood _____ the heart.
Which (arteries or veins) carries oxygenated blood? ___________
Name the one vessel that is the exception: ___________________

3. What do you call the loose, outer layer of the sac around the heart? What side points toward the heart (inside layer)? _________________
What layer is on the outside? _____________

4. When vessels expand, it is called _____________________
When they contract? ____________________

5. Briefly describe the epicardium, myocardium, and endocardium

6. Describe the size and location of the heart.

Where is the apex of the heart located? _______________________
What divides the left and right side of the heart? __________________
Which side is more muscular? __________________
What bone lies directly in front of the heart? _______________

7. During systole, the aortic valve is __________________.
During diastole, the aortic valve is __________________.

8. Veins and arteries meet at ________________________, where nutrients are exchanged with body tissues.

Arteries branch into smaller vessels called _________________
Veins also have smaller branches called __________________

9. What three things push blood back to the heart (through the veins)? _________________________

What are pre-capillary sphincters? _____________________________________

10. Describe the function of the sinoatrial node and trace the path of a nerve (cardiac) impulse through the cardiac conduction system.

What is the pacemaker? ____________________________
What fibers cause a contraction in the ventricle? ________________________
Where is the AV node located? ________________________

11. What do the terms tachycardia and bradycardia mean? What is arrhythmia? Be able to identify these on an ECG.

12. Generally speaking, when the ventricle contracts, the atrium ________________

Any contraction (atrial or ventricular) is called ___________________
Relaxing is called _______________. At what point is blood pressure at its highest? _______________

14. Identify the P-Wave, the QRS complex and a T wave on an ECG.

What is an ECG? (Be able to analyze one)

15. What is a defibrillator used for? How does it work?

16. What are systolic pressure and diastolic pressure? What is the “normal” blood pressure for a human?

17. What two piece of equipment are needed to take a person’s blood pressure?

Describe the procedure:

18. Name and give the function of all four valves of the heart. Some have multiple names; make sure you know all of them.

19. Blood that moves from the heart to the lungs and back to the heart again is in the _____________________ circuit.
Blood moving throughout the body is in the ___________________ circuit.

20. List the three major vessels that branch off of the aortic arch. You may want to draw a diagram.

21. Label all of the major vessels that attach to the heart.

22. Label a diagram of the heart and trace the flow of blood through the heart.

23. Know each of the following diseases related to the circulatory system, included how they are treated

Hypertension ___________________________________________________________________
Atherosclerosis _________________________________________________________________
Mitral Valve Prolapse _____________________________________________________________
Cardiac Infarction ________________________________________________________________
Heart Murmer ___________________________________________________________________
Deep Vein Thrombosis (Blood Clots) _________________________________________________