Session 3 - Cardiovascular system - the heart Flashcards
Location of the heart
Located in the mediastinum
- Area from sternum to the verterbral column and between lungs
- Two thirds of its mass is left of the midline
Heart orientation
o Apex - directed anteriorly, inferiorly and to the left
o Base - directed posteriorly, superiorly and to the right
o Anterior surface - deep to the sternum and ribs
o Inferior surface - rests on the diaphragm
o Right border - faces right lung
o Left border (pulmonary border) - faces left lung
Draw the surface projection of the heart
Define the pericardium
What is the name of the condition for inflammation of the pericardium
- Fibrous pericardium
- dense irregular connective tissue
- protects and anchors the heart, prevents overstretching
- Serous pericardium
• thin delicate membrane • contains
- parietal layer - outer layer
- visceral layer - inner layer
- Pericardial cavity: Space filled with pericardial fluid between the parietal and visceral pericardium. Reduces friction between the two membranes.
An inflammation of the pericardium is known as pericarditis. Associated bleeding / fluid into the pericardial cavity and compresses the heart;
potentially lethal.
What are the three layers of the heart wall
Epicardium, myocardium and endocardium
Describe the layers of the heart wall
o Epicardium
- visceral layer of serous pericardium
o Myocardium
- cardiac muscle layer - is the bulk of the heart
o Endocardium
- chamber lining and valves
Name the muscle bundles of the myocardium
Superior vena cava
Aorta
Pulmonary trunk
Superficial muscle bundles in atria
Superficial muscle bundles in ventricles
Deep muscle bundle in ventricle
* Cardiac muscle fibers swirl diagonally around the heart in interlacing bundles *
- Promotes maximum amount of expolsion
Name the chambers of the heart
2 upper atria ( left and right )
2 lower ventricles ( left and right )
Right Atrium
Receives blood from 3 sources
Superior vena cava - drains blood from the head, the neck and upper limbs
Inferior - drains blood from lower part of body and trunk
Coronary sinus - drains blood from Heart muscle or heart tissue
Right Atrium and Tricuspid valve
Tricuspid valve = It is the valve between the right atrium and right ventricle
Blood flows through tricuspid valve from the right atrium into the right ventricle.
The tricuspid valve then (closes) prevents blood from being pushed back into the right atrium when the right ventricle contracts
Right Ventricle
o Forms most of anterior surface of heart
Pumps blood Up pulmonary trunk through the pulmonary semilunar valve and into the lungs to get rid of the carbon dioxide and pick up oxygen
oChordae tendineae: cords between valve cusps and papillary muscles - connects papillary muscles with tricuspid valve
Left Atrium
oForms most of the base of the heart
oReceives blood from lungs - 4 pulmonary veins (2 right + 2 left)
oBicuspid valve: blood passes through this valve into left ventricle
- has two cusps
- to remember names of this valve, try the mnemonic LAMB
–Left Atrioventricular, Mitral, or Bicuspid valve
Left Ventricle
oForms the apex of heart
oChordae tendineae anchor bicuspid valve to papillary muscles
oAortic semilunar valve:
- blood passes through valve into the ascending aorta
- just above valve are the openings to the coronary arteries
Once pumped through semilunar valve, blood is pumped all around the body via the Aorta, has a much thicker cardiac muscle
Sulci of the heart
Grooves on surface of heart containing coronary blood vessels and fat
Myocardial Thickness and Function
Thickness of the myocardium of the four chambers varies according to the function of each chamber
- atria walls - thin because they only deliver blood to the ventricles
- ventricle walls - thicker pumping blood further
- right ventricle walls - thinner than the left because they pump blood into the lungs, which are nearby and offer very little resistance to blood flow.
- left ventricle walls - thicker because they pump blood through the body where the resistance to blood flow is greater
Atrioventricular (A-V)Valves
Bicuspid valve, tricuspid valve
oAtrioventricular (A-V) Valves open and allow blood to flow from atria into ventricles when ventricular pressure is lower than atrial pressure
• occurs when ventricles are relaxed, chordae tendineae are slack and papillary muscles are relaxed
Bicuspid valve, tricuspid valve
Atrioventricular Valves Close
Bicuspid valve (Left) and tricuspid valve (Right)
oA-V valves close preventing backflow of blood into atria
•occurs when ventricles contract, pushing valve cusps closed, chordae tendinae are pulled taut and papillary muscles contract to pull cords and prevent cusps from everting
Semilunar valves open and close
oSemilunar (SL) valves open with ventricular contraction
•allow blood to flow into pulmonary trunk and aorta
oSL valves close with ventricular relaxation
•prevents blood from returning to ventricles, blood fills valve cusps, tightly closing the SL valves
Blood circulation
oCirculation of the blood: divided into two closed circuits
•Systemic circulation (includes coronary circulation)
- Delivering oxygenated blood to the body
•Pulmonary circulation
- Delivering deoxygenated blood to the lungs and then back to the heart
Types of Blood circulation
- Systemic circulation is left side heart to body and back to heart
- Hepatic Portal circulation is capillaries of GI tract to capillaries in liver
- Pulmonary circulation is right-side heart to lungs and back to heart
- Foetal circulation is from fetal heart through umbilical cord to placenta and back
Cardiac muscle histology
Cardiac muscle fibers:
Shorter in length
Larger in diameter compared to skeletal muscle fibers.
They also exhibit branching.
Fibers within the networks are connected by intercalated discs, which consist of desmosomes and gap junctions.
Gap junctions important for electrical connectivity
Cardiac Myofibril
Conduction System of Heart
oComponents of Conductionsystem:
- Sinoatrial (SA) node (pacemaker),
- Atrioventricular (AV) node,
- Atrioventricular bundle (bundle of His), - Right and left bundle branches,
- The conduction myofibers (Purkinje fibers)
oSignals from the autonomic nervous system and hormones, such as adrenaline can modify the heartbeat (in terms of rate and strength of contraction)
SA Node
oSA node
- cluster of cells in wall of right atria
- begins heart activity that spreads to both atria
- sets the rhythm for contraction of the heart—the natural pacemaker.
- excitation spreads to AV node
AV Node
oAV node
•in atrial septum, transmits signal to bundle of His
Bundle of His
oBundle of His
- the connection between atria and ventricles
- divides into the left and right bundle branches
oPurkinje fibers
large diameter fibers that conduct signals quickly
Bundle of His will send an impulse to right and left bundle branches which will send impulse to the fibers of the purkinje
