Week 7 - Heart Flashcards
How many lobes are there in the left lung
2
Which vena cava does NOT go through the diaphragm?
Superior vena cava
Location of the heart
Rests on diaphragm near midline of thoracic cavity + lies in mediastinum.
Define pericardium
Membrane surrounding + protecting heart.
What 2 parts does the pericardium consist of?
Outer fibrous pericardium
Inner serous pericardium
What is the superficial outer fibrous pericardium composed of?
Tough, inelastic, dense irregular connective tissue.
What is the function of the superficial outer fibrous pericardium?
Prevents over-stretching of heart
Provides protection
Anchors heart in mediastinum
Location of fibrous pericardium
Near apex of heart
Partially fused to central tendon of diaphragm
Describe the deeper/inner serous pericardium
Thinner
More delicate membrane
Double layer around heart.
What is the outer parietal layer of serous pericardium fused to?
Fibrous pericardium
Inner visceral layer of serous pericardium a.k.a epicardium
Adheres tightly to surface of heart.
Define pericardial fluid
⬇️ friction between layers of serous pericardium as heart moves.
What are the 3 layers of the heart wall
Epicardium (external)
Myocardium (middle)
Endocardium (inner)
Pericarditis
Inflammation of pericardium
Build up of pericardial fluid
Squeezes myocardium
Heart can’t contract fully
What does the epicardium contain
Bv
Lymphatics
Vessels that supply the myocardium
What is the myocardium responsible for?
Pumping action of heat
What is the myocardium composed of
Cardiac muscle tissue.
It’s muscle fibres are wrapped + bundled w. connective tissue sheaths composed of endomysium + perimysium.
Function of endocardium
Provides smooth lining for chambers of heart
Minimises surface friction as blood passes through
Auricles of the heart
Anterior surface of each atrium
Wrinkled pouch like structure
Slightly ⬆️ capacity of each atrium
Sulci of the heart
Grooves containing bv + fat
Separate chambers
Simple blood flow order
Vena cava
Tricuspid valve
Pulmonary semilunar valve
Pulmonary artery
Pulmonary veins
Bicuspid (mitral) valve
Aortic valve
Aorta
Location of right atrium
Anterior upper medial surface of heart.
How thick is right atrium
2-3mm
Where does the right atrium receive blood from?
Superior + inferior vena cava
Coronary sinus
Define interatrial septum
Thin partition between right + left atrium.
How thick is the right ventricle
4-5mm
From how many pulmonary veins does the left atrium receive blood?
4
What is the wall like anteriorly + posteriorly of the left atrium
Smooth
What does blood pass through to get from left atrium to left ventricle
Bicuspid valve
How thick is the left ventricle
10-15mm
Thickest chamber
Where does blood pass through from left ventricle
Aortic valve –> ascending aorta.
Some in aorta flows into coronary arteries which branch from ascending aorta + carry blood to heart wall.
Remainder passes into arch of aorta + descending aorta.
What happens to the AV when open?
Rounded ends of cusps project into ventricle
What happens to the papillary muscles + chordae tendineae when ventricles are relaxed?
Papillary muscles are relaxed
Chordae tendineae are slack
What happens to the papillary muscles + chordae tendineae when ventricles contract?
Papillary muscles contract = pulling on + tightening chordae tendineae.
– Preventing valve cusps from everting in response to high ventricular pressure.
What happens if AV valves or chordae tendineae are damaged
Blood may regurgitate into atria when ventricles contract.
What are the SL valves made up of?
3 crescent moon-shaped cusps
Define pacemaker potential
Spontaneous depolarisation of the SA node cells
What happens when pacemaker pot reaches threshold
Triggers AP
1st step to the conduction system
AP from SAN propagates throughout both atria via gap junctions in intercalated discs of atrial muscle fibres = Atria contract simultaneously.
2nd step to the conduction system
AP reaches AVN
Slows due to differences in cell structure
= Time for atria to empty blood into ventricles.
3rd step to conduction system
AP enters AV bundle/Bundle of His, then both right + left bundle branches.
4th step to the conduction system
Purkinje fibres rapidly conduct AP from apex of heart up to remainder of ventricular myocardium = ventricles contract = pushing blood up toward SL valves.
Define ECGs
Record of AP produced by all heart muscle fibres during each HB.
Instrument used = electrocardiogram
What does an ECG enable one to determine?
If conducting pathway is normal
If heart is enlarged
If certain regions of heart are damaged
Cause of chest pain
Why is the T wave smaller + wider than the QRS complex
Due to reploraization occurring slower than depolarisation.
Where do the coronary arteries branch from
Ascending aorta + encircle the heart.
Why does blood flow into the coronary arteries when heart is contracting
Due to being squeezed shut
Where does the left coronary artery pass?
Inferior to left auricle
Anterior interventricular branch / Left anterior descending (LAD) artery
Supplies O2-blood to walls of both ventricles.
Where does the circumflex branch lie?
In the coronary sulcus
What does the right coronary artery do?
Supplies small atrial branches to right atrium.
Location of Posterior interventricular branch
Follows posterior interventricualr sulcus
Where does the Marginal branch run?
Along right margin of heart
Coronary Veins
Most of the deO2-blood from myocardium drains into a large vascular sinus in the sulcus on posterior surface of heart called coronary sinus
What is blood flow to coronary circulation controlled by?
Primarily by metabolites.
Minor role of sympathetic — vasodilate.
Minor control parasympathetic — Vasoconstrict.
Detailed blood flow order
Blood —> inferior + superior vena cava.
Deposited into right atrium — also comes here from coronary blood supply via coronary sinus.
From this chamber blood will go through tricuspid valve —> right ventricle.
Blood —> pulmonary artery though pulmonary SL valve.
After going round pulmonary circulation, blood is returned to heart in pulmonary veins.
Blood in left atrium —> bicuspid valve —> left ventricle.
Blood —> aortic SL valve —> aorta.
Sounds for the heart beat
S1 - Cupsid valves close - lubb
S1 - SL valves close - dubb
S3 - Ventricular filling
S4 - Atrial systole
Where do you listen to the heart
2nd intercostal left + right
Left 4th intercostal sternal border
Left 5th intercostal mid clavicular line
Where does the circumflex branch distribute O2-blood to?
Walls of left ventricle + left atrium.
Where can the right coronary artery be found?
Inferiorly to right auricle
Divides into posterior inter ventricular + marginal branches.
What does the Posterior interventricular branch do?
Supplies walls of ventricles w/ O2 blood.
What does the marginal branch do?
Transports O2-blood to wall of right ventricle.
