Human Anatomy and Physiology Unit IV Circulation and

Human Anatomy and Physiology Unit IV Circulation and Body Defense Part II The Heart

Resources Your textbook – Chapter 20 Your lab manual – Exercise 27 and 28 Wiley PLUS

Heart Topics 1. 2. 3. 4. 5. 6. 7. 8. Location of the Heart Chambers of the Heart Valves Coronary Circulation Cardiac Muscle Cardiac Conduction System Cardiac Cycle Cardiac Output

Location of the Heart The heart is located in the mediastinum, where it is surrounded by a doublelayered pericardium

Location of the Heart The heart is located in the mediastinum, where it rests on the diaphragm

Location of the Heart Two-thirds of the heart lies to the left of the midline

Location of the Heart

Location of the Heart The heart is enclosed and held in place by the pericardium

Location of the Heart 1. Outer fibrous pericardium 2. Inner serous pericardium A) Parietal layer B) Visceral layer

Pericardium

Pericardium Parietal pericardium Visceral Pericardium

Pericardial Diseases Pericarditis Inflammation of the pericardium Pericardial effusion Passage of fluid into the pericardial cavity Often due to congestive heart failure

Pericardial Diseases Cardiac tamponade Bleeding into the pericardial cavity

Pericardial Diseases

Heart Topics 1. 2. 3. 4. 5. 6. 7. 8. Location of the Heart Chambers of the Heart Valves Coronary Circulation Cardiac Muscle Cardiac Conduction System Cardiac Cycle Cardiac Output

Location of the Heart The wall of the four-chambered heart has three layers: (1) epicardium, (2) myocardium, and (3) endocardium

Layers of the Heart Wall Epicardium Myocardium Endocardium

Chambers of the Heart Right atrium Right ventricle Left atrium Left ventricle

Chambers of the Heart Anterior View Posterior view

Chambers of the Heart Right atrium and right ventricle pump blood to the lungs

Chambers of the Heart Left atrium and left ventricle pump blood to the rest of the body

Coronary Sulci Coronary sulcus Anterior interventricular sulcus Posterior interventricular sulcus

Coronary Sulci Coronary sulcus Anterior interventricular sulcus Posterior interventricular sulcus

Right Atrium Forms the right border of the heart Receives blood from: Superior vena cava Inferior vena cava Coronary sinus

Right Atrium Forms the right border of the heart Receives blood from: Superior vena cava Inferior vena cava Coronary sinus

Right Atrium In between the atria is the interatrial septum Fossa ovale

Right Atrium Posterior atrial wall is smooth Anterior wall is rough. Pectinate muscle Right auricle

Right Atrium

Right Atrium Blood leaves the right atrium through the tricuspid valve

Right Ventricle Forms most of the anterior surface of the heart

Right Ventricle Right and left ventricles are separated from each other by the interventricular septum

Right Ventricle The inside of the right ventricle contains muscular ridges called trabeculae carnae

Right Ventricle Blood leaves the right ventricle through the pulmonary semilunar valve Pulmonary trunk Right and left pulmonary arteries

Left Atrium Forms most of the base of the heart Receives blood from the pulmonary veins

Left Atrium The left atrium is separated from the right atrium by the interatrial septum

Left Atrium The walls of the left atrium are smooth except for the auricle

Left Atrium Blood leaves the left atrium through the bicuspid valve

Left Ventricle Forms the apex of the heart

Left Ventricle Receives blood from the left atrium Bicuspid valve Chordae tendinae Papillary muscles

Left Ventricle Blood leaves the left ventricle through the aortic semilunar valve Ligamentum arteriosum

Atrial Septal Defects Incomplete closure of the foramen ovale.

Ventricular Septal Defects Incomplete formation of the interventricular septum.

Myocardial Thickness and Function Atrial walls are thinner than ventricular walls Walls of the right ventricle thinner than walls of the left ventricle

Fibrous Skeleton Four dense connective tissue rings wrapped around the four AV valves of the heart

Heart Topics 1. 2. 3. 4. 5. 6. 7. 8. Location of the Heart Chambers of the Heart Valves Coronary Circulation Cardiac Muscle Cardiac Conduction System Cardiac Cycle Cardiac Output

Location of the Heart valves ensure that blood flow is one way

Heart Valves Left AV valve (bicuspid) Right AV valve (tricuspid) Pulmonary semilunar valve Aortic semilunar valve

AV Valves An AV valve opens towards the ventricle One-way due to pressure gradient Backflow prevented by papillary m. and chordae tendinae

SL valves An SL valve opens towards the artery One-way due to pressure gradient Backflow prevented by shape of valve

Heart Murmers Valve incompetence Valve stenosis

Valve Implants

Heart Topics 1. 2. 3. 4. 5. 6. 7. 8. Location of the Heart Chambers of the Heart Valves Coronary Circulation Cardiac Muscle Cardiac Conduction System Cardiac Cycle Cardiac Output

Blood Flow Systemic circulation Pulmonary circulation

Coronary Circulation Lt. coronary a. Left anterior descending a. Circumflex a. Rt. coronary a. Posterior descending coronary a.

Cardiac Veins Great Middle Small Anterior

Athersclerosis

Coronary Bypass

Heart Topics 1. 2. 3. 4. 5. 6. 7. 8. Location of the Heart Chambers of the Heart Valves Coronary Circulation Cardiac Muscle Cardiac Conduction System Cardiac Cycle Cardiac Output

Cardiac Muscle © Jason Taylor

Cardiac Muscle © Jason Taylor

Heart Topics 1. 2. 3. 4. 5. 6. 7. 8. Location of the Heart Chambers of the Heart Valves Coronary Circulation Cardiac Muscle Cardiac Conduction System Cardiac Cycle Cardiac Output

Cardiac Conduction System

Action Potentials in Cardiac Cells Rapid Depolarization Plateau Repolarization Refractory Period

The ECG P Wave QRS Complex T Wave

ECG

Heart Topics 1. 2. 3. 4. 5. 6. 7. 8. Location of the Heart Chambers of the Heart Valves Coronary Circulation Cardiac Muscle Cardiac Conduction System Cardiac Cycle Cardiac Output

The Cardiac Cycle Atrial Systole Ventricular Systole Relaxation Period

Atrial Systole ECG Connection: from P wave to Q wave AV valves: open SL valves: closed

Atrial Systole Both atria contract Atrial pressure increases AV valves open Blood flows into both ventricles Ventricles are relaxed Ventricular pressure too low to open SL valves

Ventricular Systole Divided into two periods isovolumetric ventricular contraction ventricular ejection Atria are relaxed and filling with blood

Isoventricular Ventricular Contraction ECG Connection: begins with R wave AV valves: closed SL valves: closed

Isoventricular Ventricular Contraction Both ventricles begin contracting Ventricular pressure increases AV valves close Ventricular pressure too low to open SL valves remain closed

Ventricular Ejection ECG Connection: from S wave to T wave AV valves: closed SL valves: open

Ventricular Ejection Both ventricles continue contracting Ventricular pressure continues to increase AV valves remain closed High ventricular pressure opens SL valves Blood is ejected into pulmonary trunk and aorta

Stroke Volume Stroke volume - the volume of blood ejected from each ventricle during systole. SV= EDV-ESV SV =130 ml – 60 ml SV = 70 ml

Relaxation Period Divided into two periods: Isovolumetric ventricular relaxation Passive ventricular filling Both atria and ventricles are relaxed and filling with blood

Isovolumetric Ventricular Relaxation ECG Connection: begins at end of T wave AV valves: closed SL valves: closed

Isovolumetric Ventricular Relaxation Both ventricles begin to relax Ventricular pressure begins to decrease Low ventricular pressure closes SL valves Ventricular pressure too highto open AV valves

Passive Ventricular Filling ECG Connection: after T wave to next P wave AV valves: open SL valves: closed

Passive Ventricular Filling Both ventricles continue to relax ventricular pressure continues to decrease SL valves remain closed Atrial pressure exceeds ventricular pressure AV valves open Blood fills the ventricles

Cardiac Cycle and Heart Rate Durations of atrial and ventricular systole are relatively constant Increased heart rate decreased relaxation period

Heart Topics 1. 2. 3. 4. 5. 6. 7. 8. Location of the Heart Chambers of the Heart Valves Coronary Circulation Cardiac Muscle Cardiac Conduction System Cardiac Cycle Cardiac Output

Cardiac Output (CO) = SV X HR At rest CO = 70 X 75 At rest CO = 5. 25 L/minute Cardiac Reserve = 5 X CO CO adjusted by changing SV or HR

Regulation of Stroke Volume Preload Contractility Afterload

Preload Increased stretch increased force of contraction Increased filling during diastole increased force of contraction during systole Determined by: Duration of ventricular diastole Venous return

Why Preload? The relationship between ventricular filling (EDV) and preload equalizes the output of the right and left ventricles and keeps the same volume of blood flowing to both systemic and pulmonary circulations.

Contractility Positive inotropics increase contraction Norepinephrine and epinephrine Negative inotropics decrease contraction Acetylcholine

Afterload – the pressure that the ventricles must overcome to open the SL valves. Increased afterload decreased SV

Regulation of Heart Rate Regulating HR is the body’s principal mechanism of short-term control of CO Three main mechanisms: 1. ANS 2. Endocrine system 3. Other factors

Regulation of Heart Rate - ANS

Regulation of Heart Rate - Endocrine Epinephrine and Norepinephrine Increase HR and contractility Thyroid hormone Increases HR and contractility Cations also affect heart rate: Na+ and K+ decrease HR and contractility Ca 2+ increases HR and contractility

Regulation of Heart Rate – other factors Cations also affect heart rate: Na+ and K+ decrease HR and contractility Ca 2+ increases HR and contractility

EXERCISE AND THE HEART

Exercise and the Heart