Download Chapter 14 PP PDF

5/5/15
The Cardiovascular System
Chapter 14
The Cardiovascular System
When you h ave completed this chapter should be able to:
• 1. Describe the external and internal anatomy of the heart.
• 2. Follow the flow of blood through the heart, pulmonary circulation, and systemic circulation.
• 3. Explain how the heart valves keep blood flowing in the proper direction through the heart.
1
5/5/15
The Cardiovascular System
• 4. Describe the components of the cardiac conduction system and explain how it works to keep the heart beating in an organized fashion.
• 5. Explain what happens during one cardiac cycle.
• 6. Understand cardiac output and what conditions can affect it.
• 7. Describe the anatomy of arteries, veins, and capillaries and understand the function of each type of blood vessel
The Cardiovascular System
• 8. Understand the difference between fetal and newborn circulation.
• 9. Understand the different m ethods used to evaluate the cardiovascular system.
• 10. Know the common pulse points and venipuncture sites for common species of animal.
2
5/5/15
The Cardiovascular System
• Vocabulary Fundaments:
– Be able to define, describe, or identify the terms on pages 338 and 339.
The Cardiovascular System
• Blood continuously flows through a animal’s body through the heart.
• Blood is propelled by a beating, pumping m uscular heart.
• Blood vessels are:
– Arteries, arterioles, capillaries, v enules, v eins
3
5/5/15
The Cardiovascular System
• Blood cycles through the body in a “figure 8”
• Circulation can be divided into two categories:
– Pulmonary circulation (lungs)
– Systemic c irculation (body)
4
5/5/15
The Heart
• The base of the heart is rounded at the cranial end.
• The apex of the heart is more pointed at the caudal end
• The heart is located in the middle of the thoracic cavity, between the two lungs, in an area called the mediastinum.
• The apex is shifted to the left and sits more ventrally. 5
5/5/15
6
5/5/15
The Heart
• The heart lies in a fibrous sac called the pericardium, or pericardial sac.
• The pericardium, or serous pericardium, has a visceral layer and a parietal layer.
• The pericardial space is filled with a small amount of pericardial fluid. 7
5/5/15
The Heart
• The heart wall is made up of three separate layers of tissue:
– Epicardium
– Myocardium
– Endocardium
• The endocardium covers the papillary muscles as well. 8
5/5/15
The Heart
• The heart is composed of m yocardium, or specialized heart muscle tissue.
• There are four chambers in the mammalian heart:
– Right and left atria
– Right and left v entricles
9
5/5/15
The Heart
• The atria sit on the top of the heart to form the base. (Atrium = singular)
• The atria receive blood returning to the heart. • The r ight and left atria are separated by the interatrial septum.
• When filled with blood the right and left atrial contract and push blood down into the right and left ventricles.
10
5/5/15
The Heart
• The auricles are blind pouches that are a part of the atria.
• The interventricular grove is formed by the interatrial septum and the interventricular septum.
• The interventricular grove contains coronary blood vessels and fat.
11
5/5/15
The Heart
• The ventricles sit below the atria.
• The ventricles pump blood to the body and the lungs.
– The right ventricle pumps blood to the lungs.
– The left v entricle pumps blood to the body.
• The ventricles are separated by the interventricular septum. The Heart
• There are four one-­way valves that control blood flow through the heart:
– Right Atrioventricular Valve (Tricuspid)
– Left Atrioventricular Valve (Bicuspid or Mitral)
– Pulmonary Semilunar Valve
– Aortic Semilunar Valve
12
5/5/15
The Heart
• There are three components to the Right and Left Atrioventricular Valves:
– Leaflets or Cusps
– Chordae tendineae
– Papillary muscles
13
5/5/15
The Heart
• The “ skeleton” of the heart is located between the atria and the ventricles, and is made up of four dense fibrous connective tissue rings. • The tissue: – Separates the atria and the ventricles
– Anchors the heart valves
– Serves as a point if attachment for the myocardium
– Serves as electrical insulation between the atria and the ventricles
14
5/5/15
The Heart
• The heart has its own blood supply.
• The coronary arteries branch off the aorta and carry oxygenated blood to the myocardium.
• The coronary veins carry deoxygenated blood from the myocardium back to the right atrium of the heart.
15
5/5/15
The Heart
•
The cardiac muscle creates its own electrical impulses and produces its own contractions and relaxation.
•
There are nerves that slow or speed the heart, but they are not necessary for cardiac contractions. •
Cardiac conduction system:
– SA Node
– AV Node
– Right and left AV bundles
– Right and left bundle branches
– Purkinje fibers
16
5/5/15
The Heart
•
The cardiac cycle is made up of one complete heartbeat.
•
There is one cycle of atrial contraction and one cycle of ventricular contraction. – Systole = active contraction and depolarization of the myocardium
– Diastole = relaxation and repolarization of the myocardium
•
Each heart chamber does through a cyclic period of systole and diastole to complete one cardiac cycle. •
The chamber contractions are sequential, not at the same time.
17
5/5/15
The Heart
• The normal heart sounds are produced by the heart valves snapping closed. • One cardiac cycle produces two distinct heart sounds:
– First heart sound “Lub” is produced by the right and left AV v alves c losing. Occurs after atrial systole.
– Second heart sound “Dub” is produced by the pulmonary and aortic v alves c losing. Occurs after ventricular systole.
18
5/5/15
The Heart
• Abnormal heart sounds can be heard when the valves are not closing properly.
• Abnormal heart sounds are r eferred to as heart murmurs. • Valvular insufficiency = one or more values do not close completely
• Valvular stenosis = one or more valves do not open properly. The Heart
• Reference Web Site:
– http://www.vetgo.com/cardio/
19
5/5/15
The Heart
• Cardiac Output ( CO) is the volume of blood that is ejected from the left ventricle over a period of time, usually defined as one minute.
• CO = Stroke volume ( SV) X Heart r ate (HR)
• SV = Represents the relative strength of the heart
The Heart
• Stroke Volume is determined by four factors:
– 1) Preload
– 2) Contractility
– 3) Relaxility
– 4) Afterload
20
5/5/15
The Cardiovascular System
• The normal heart rate for each species is set internally and is dependent on the resting rate of SA node depolarization. • Outside factors increase or decrease the HR. 21
5/5/15
22
5/5/15
The Circulatory System
• Arteries are blood vessels that carry blood away from the heart.
• Pulmonary circulation carries deoxygenated blood from the heart to the lungs.
• Systemic circulation carries oxygenated blood to body tissues. • Arteries are usually paired
The Circulatory System
• There are two types of arteries:
– Elastic, such as the aorta
– Muscular, such as the arterioles
23
5/5/15
The Circulatory System
• Capillaries are the microscopic blood vessels found in tissues from branching arterioles.
• Capillaries occur in groups call capillary beds or capillary networks.
• Capillary walls are one endothelial cell thick
• The exchange of gasses, nutrients, and waste products occurs at this level The Circulatory System
• Veins carry blood towards the heart.
• Pulmonary veins carry oxygenated blood from the lungs back to the left atrium. • Systemic veins carry deoxygenated blood from body tissues back to the right atrium. 24
5/5/15
The Circulatory System
• Capillaries join together to form venules and venules join together to form veins.
• Many veins have one-­way valves present. • Muscular m ovements and values insure that the venous blood is returned to the heart.
• All systemic veins drain into the cranial or caudal vena cava. 25
5/5/15
26
5/5/15
27
5/5/15
The Circulatory System
• A fetus r eceives oxygen from the blood of its mother.
• Fetal lungs are not used for gas exchange.
• Fetal lungs only need enough oxygen to keep the tissues alive. • Gas exchange occurs through the placenta and umbilical cord
The Circulatory System
• On the first breath after birth.
• The lungs inflate and the new born starts to oxygenate its own blood.
• The foramen ovale and ductus arteriosus close so that the lungs are no longer bypassed in circulation. 28
5/5/15
29
5/5/15
30
5/5/15
The Circulatory System
• A pulse is the rate of alternating stretching and recoiling of elastic fibers in an artery as blood passes through with each heartbeat.
• A clinical pulse evaluates the regularity of pulsations and their strength.
• Auscultation is not a true pulse.
• There should be one pulse for each heartbeat. The Circulatory System
• The pulse should be the same for each heartbeat.
• Most often the pulse is felt on superficial arteries lying against firm surfaces, such as bones. • Generally, large animals have slower pulses and small animals have faster pulses. 31
5/5/15
The Circulatory System
• Blood pressure ( BP) is the measurement of of the amount of pressure that flowing blood exerts against arterial walls. • BP is dependent on:
– Heart rate
– Stoke v olume
– Diameter and elasticity of the artery
– Total blood volume
The Circulatory System
• Blood pressure varies during the cardiac cycle.
• Systolic is the highest number
• Diastolic is the lowest number
• Mean Arterial Pressure (MAP) is the average pressure during one cardiac cycle.
• MAP = (CO X SVR) + CVP
32
5/5/15
The Circulatory System
•
Blood pressure can be measured by:
– Oscillometric method, where a cuff is placed over an artery and the cuff measures the magnitude and and frequency of the pulsations.
– Doppler ultrasound, where a transducer is attached to a sphygmomanometer and systolic BP is measured. – Direct method, where a catheter is placed in an artery and the BP is measured directly from circulation.
The Cardiovascular System
• Indirect m ethods of monitoring the CV System:
– Auscultation of the thorax
– Peripheral artery palpation
– Arterial BP evaluation
– Thoracic radiography
– Electrocardiography
– Echocardiography 33
5/5/15
The Cardiovascular System
• Electrocardiography ( EKG or ECG) is based on the electrical activity of the heart. • The EKG detects the myocardial impulses on the surface of the body and produces a graphic representation. • The components of a EKG are:
– P wave
– QRS complex
– T wave
34
5/5/15
The Cardiovascular System
• Echocardiography, or an ECHO, is a common cardiac ultrasound procedure.
• Sound waves are bounced off the heart to watch the heart beat and blood flow. • ECHO’s are used to evaluate the size, shape, and movement of the heart and its various parts. 35
5/5/15
The Cardiovascular System
• Two-­dimensional echocardiography produces a cross section of of the heart, and gives the ability to see the heart working in real time.
• Doppler echocardiography adds color to the two dimensional image and is useful for evaluation of valvular stenosis or valvular insufficiencies. 36
5/5/15
The Cardiovascular System
• Superficial blood vessels can be used to perform venipuncture to collect blood samples, administer IV medications, and place IV catheters. • The external jugular vein is the most common site for venipuncture. • The superficial caudal epigastric vein (milk vein) can use used in dairy cattle but is not desirable. • In ruminants and r odents the coccygeal vein can also be used. 37
5/5/15
38
5/5/15
39
5/5/15
40