23/24. Heart

Question 1

Sides of the heart and their functions

Answer 1

2 sides, 4 chambers
Right side: receives deoxygenated blood from body and pumps blood to lungs (pulmonary circuit)
Left side: receives oxygenated blood from the lungs and pumps to the body (systemic circuit)

Question 2

Location and physical characteristics of heart

Answer 2

About fist sized
Lies behind sternum but assymetrical
Apex: down to the left
Base: posterior side
Mediastinum: area between lungs

Question 3

Components of the pericardium

Answer 3

Triple layered sac around the heart
Consists of fibrous pericardium and serous pericardium
Forms pericardial sac (fibrous + parietal layers) and pericardial space (between parietal and visceral layers)

Question 4

Fibrous pericardium

Answer 4

Outer layer of dense CT

Question 5

Serous pericardium

Answer 5

Consists of parietal and visceral (aka epicardium) layers
Parietal: outer layer (adhered to fibrous pericardium)
Visceral: inner layer (adhered to heart)

Question 6

Components of the heart wall

Answer 6

Epicardium = visceral pericardium
Myocardium = cardiac muscle
Endocardium = endothelium + connective tissue

Question 7

Characteristics of the heart wall in regards to ventricles and atria

Answer 7

Ventricles are thicker than atria
Includes pectinate muscle and trabeculae carnae
Ventricles separated by interventricular septum
Atria separates by interartrial septum

Question 8

Pectinate muscle

Answer 8

Bands of muscle in atria

Question 9

Trabeculae carneae

Answer 9

“Beams of meat”
Bands of muscle in ventricles

Question 10

Passage of oxygen-poor blood through the heart

Answer 10

1. Superior vena cava, inferior vena cava, and coronary sinus
2. Right atrium
3. Through the tricuspid valve
4. Right ventricle
5. Through the pulmonary semilunar valve
6. Pulmonary trunk

Question 11

Passsage of oxygen-rich blood through the heart

Answer 11

1. Four pulmonary veins
2. Left atrium
3. Through the mitral valve
4. Left ventricle
5. Through the aortic semilunar valve
6. Aorta

Question 12

Heart valves

Answer 12

2 atrioventriclular (AV) valves and 2 semilunar valves

Question 13

Atrioventricular (AV) valves of the heart

Answer 13

Between atria and ventricles
Right AV valve (tricuspid valve)
Left AV valve (bicupsid valve)

Question 14

Semilunar valves of the heart

Answer 14

Between ventricles and arteries
Pulmonary semilunar valve
Aortic semilunar valve

Question 15

Tricuspid valve

Answer 15

3 cusps
Between right atrium and right ventricle
Includes chordae tendineae - “strings” attach cusps to papillary muscles

Question 16

Function of tricuspid valve

Answer 16

During ventricle contraction (systole):
Blood pushes valve closed
Papillary muscles contract to pull chordae tendineae taught
Prevents prolapse of cusps into right atrium

Question 17

Characteristics of bicupsid valve

Answer 17

Also called mitral valve
Has 2 cusps and 2 papillary muscles
Between left atrium and left ventricle

Question 18

Characteristics of semilunar valves

Answer 18

Pulmonary semilunar valve opens to pulmonary trunk
Aortic semilunar valve opens to aorta

Question 19

Ventricular systole

Answer 19

Contraction of ventricles
Atrioventricular valves shut
Semilunar valves open
Blood pumped through semilunar valves into pulmonary trunk and aorta

Question 20

Ventricular diastole

Answer 20

Relaxation of ventricles
Atrioventricular valves open
Semilunar valves shut
Blood pumped from atria into ventricles

Question 21

Sounds of the heart

Answer 21

We hear “lub-dub”
“Lub” is from atrioventricular valves closing during ventricular systole
“Dub” is from semilunar valves closing during ventricular diastole

Question 22

Heart murmur

Answer 22

Unusual sound due o faulty heart valve
Can be caused by a valve that doesn’t close properly or a calcification of the valve (stenosis)
In severe cases, surgery or valve replacement is required

Question 23

Coronary arteries

Answer 23

Aorta, pulmonary trunk, right coronary artery, left coronary artery, circumflex artery, anterior interventricular artery, and posterior interventricular artery

Question 24

Cardiac veins

Answer 24

Anterior cardiac veins, great cardiac vein, coronary sinus, and middle cardiac vein

Question 25

Overview of blood supply to cardiac muscle

Answer 25

Anterior interventricular artery runs with great cardiac vein
Anterior cardiac veins cross over right coronary artery
Posterior interventricular artery runs with middle cardiac vein

Question 26

Atherosclerosis

Answer 26

Fatty deposits in arteries that become plaque and restrict blood flow

Question 27

Myocardial infarction

Answer 27

Heart attack
Coronary arteries blocked with plaque can’t deliver blood to the cardiac muscle
Muscle cells die and heart can’t function

Question 28

Bypass graft

Answer 28

Donor blood vessel is sewn to the aorta… “bypassing” the occluded vessel
Operation for MI

Question 29

Conduction system of the heart

Answer 29

Heart contracts ~72 beats per min
Specialized cardiac muscle cells in the sinoatrial (SA) node generate and propagate an impulse through heart (autorhythmicity)
Impulses travel through walls of atria, then converge on atrioventricular (AV) node
AV bundle carries the impulse down interventricular septum, divides into left and right bundle branches
Purkinje fibers (subendocardial network) extend from apex of heart to walls of ventricles

Question 30

SA and AV nodes

Answer 30

SA node is the pacemaker of the heart located in right atrium
AV node receives impulses in the right atrium near the tricuspid valve and divides them into bundles

Question 31

Characteristics of cardiac skeleton

Answer 31

Fibrous connective tissue around heart valves
Prevents spread of conduction directly from atrial walls to ventricle walls
Cardiac skeleton bypassed by AV bundles

Question 32

Abnormal heart beats

Answer 32

Arrhythmia: abnormal heart rhythm
Ventricular fibrillation: rapid, random electrical firing into the ventricles that leads to cardiac arrest
Atrial fibrillation: random bursts of electrical activity in the atria that creates poorly coordinated contractions and leads to blood clots & stroke
Tachycardia: abnormally high heart rate
Bradycardia: abnormally low heart rate

Question 33

Innervation of the heart

Answer 33

SA node spontaneously depolarizes ~72 bpm
However, autonomic influence heart rate
Cardiac control center located in medulla oblongata
Sympathetics from the sympathetic trunk increase HR
Parasympathetics from the vagus nerve (CN X) decrease HR

Question 34

Characteristics of fetal circulation

Answer 34

Lungs are not truly functional until after birth
Developing fetus receives oxygenated blood from the placenta
Umbilical vein carries mother’s blood from placenta to right atrium
Oxygenated blood needs to bypass pulmonary circulation to reach aorta and body tissues

Question 35

Structures of fetal circulation

Answer 35

Foramen ovale: opening between right and left atria that moves oxygenated blood from right side to left side of heart, bypassing lungs
Ductus arteriosus: connection between pulmonary trunk and aorta
Both structures close off at birth

Question 36

Congenital heart defects: patent foramen ovale

Answer 36

Also known as atrial septal defect
Foramen ovale between atria fails to close after birth
Leads to symptoms of heart murmur, shortness of breath with exercise, fatigue, cyanosis, and stork due to blood clots passing through opening and traveling to brain