The Heart Flashcards
What the heart does
- Arteries
- Veins
- Great Veins
-Heart propels blood to and from most body tissues via arteries and veins
Arteries: Blood vessels that carry blood away from the heart
Veins: Blood vessels that carry blood back to the heart
Great Vessels: arteries and veins entering and leaving the heart (have a relatively large diameter)
General characteristics & Functions of the Heart (3)
-defn. of blood pressure
- Blood flow is unidirectional
- Acts like 2 side-by-side pumps (work at same rate and pump same volume of blood)
- Develops blood pressure through alternate cycles of wall contraction & relaxation
Blood pressure=force of the blood pushing against the inside walls of blood vessels
-minimum blood pressure essential to circulate blood throughout body
Pulmonary vs Systemic circulation
Pulmonary: Conveys deoxygenated blood from right side of heart to lungs to be oxygenated (and to release CO2)
Systemic: Moves oxygenated blood from left side of heart to systemic cells of rest of body
-deoxygenated blood return to right side
Basic flow of blood (heart, lungs, body)
Right side of heart -> lungs -> left side of heart -> systemic tissues of body -> back to right side of heart
Position of the heart
- base
- apex
- Slightly left of midline, deep to the sternum in the mediastinum (compartment of the thorax)
- Base of heart= posterosuperior surface of heart - is mainly left atrium
- superior border is formed by the great arterial vessels & superior vena cava
- Apex: inferior conical end
- inferior border formed by right ventricle
Pericardium
- Composition
- Function
- 2 Parts
-is a tough sac that the heart is enclosed in
-Restricts heart’s movement and prevents it from overfilling w/ blood
2 parts:
1. Firbrous pericardium: outer covering of tough, dense CT
-attached to diaphragm and base of great vessels
2. Serous pericardium: inner portion = thin, double-layered serous membrane subdivided into;
i) Parietal layer (lines surace of fibrous pericardium)
ii) Visceral layer (aka Epicardium - covers outer surface of heart)
-b/w 2 layers = pericardial cavity where serous fluid secreted to lubricate movement of heart
Anatomy of Heart Wall
- 3 layers;
1. Epicardium: outermost layer - also known as visceral layer- serious membrane & areolar CT
- as we age more fat is deposited - becomes thicker and more fatty
- Myocardium: Middle layer
- composed of cardiac muscle tissue (is thickest layer)- is where heart attacks occur
- Endocardium: internal surface of heart & external surfaces of heart valves
- Myocardium: Middle layer
- simple squamous epithelium & layer of aerolar CT
External Heart Anatomy
- Chambers
- Auricle
- 4 hollow chambers; 2 small atria & 2 larger ventricles
- anteroinferior borders of atria = muscular extension called AURICLE
- Coronary Sulcus: deep groove that separates the atria and ventricles
Atria (general facts)
- Thin walled chambers located supriorly
- receives blood returning from both circulations & passes to ventricle on each side
Ventricle (general facts)
- inferior chambers
- 2 large arteries (pulmonary artery & aorta) leave at superior pole
4 Valves in the heart
- Right atrioventricular (tricupsid)
- Pulmonary semilunar
- Left atrioventricular (bicupsid or mitral)
- Aortic semilunar
Right atrium
- what it receives
- 3 veins that drain into it
- associated valve
- Receives venous (deoxygenated) blood from heart, muscles & systemic circulation
- 3 veins drain into it;
- Superior vena cava
- Inferior vena cava
- Coronary sinus
- Right atrioventricular valve separates right atrium from right ventricle
- forced closed when right ventricle begins to contract - prevents blood backflow
Right Ventricle
- What it receives
- Features
- Receives deoxygenated blood from right ventricle (through right atrioventricular valve)
- Intraventricular septum forms thick wall between right and left ventricles
- Has large, irregular muscular ridges on inner wall = trabeculae carneae
- typically 3 cone-shaped muscle projections = papillary muscles
- anchor thin strands of CT w/ collagen fibres called chordae tendineae (attach to tricuspid valve)
- superior end (or roof) = conus arteriosus (smooth area)
- beyond this = pulmonary semilunar valve (marks end of ventricle & beginning of pulmonary trunk)
Left Atrium
- what it receives
- how separated from left ventricle
- Oxygenated blood from lungs travels through pulmonary veins to left atrium
- separated from left ventricle by left atrioventricular valve (tricuspid)
- forced shut when left ventricle contracts in similar fashion to closing of right antrioventricular valve
Left Ventricle
- Wall typically 3 x thicker than right
- superior end (roof) = aortic semilunar valve
- marks end of ventricle and beginning of aorta
- pressure of blood backflowing onto valve is what closes them
Semilunar valves
- 2 types
- location
- Features
- Mechanism of action w/ contraction and relaxation
- either pulmonary or aortic
- located in roof of right & left ventricles
- each one composed of three thin, half-moon shaped, pocketlike semilunar cusps
- When ventricles contract, blood pushes cusps against arterial trunks
- when ventricles relax, some blood flows back - enters pockets of cusps & forces them toward midline & closes them
Coronary Circulation
- Right & left coronary arteries travel w/in coronary sulcus & supply heart wall muscle w/ oxygen & nutrients
- coronary arteries are only branches given off by ascending aorta just superior to aortic semilunar valve
Right coronary artery - 2 branches and what they supply
- branches into 2 arteries
1) Marginal artery: supplies to right border of the heart
2) Posterior interventricular artery - supplies the posterior surface of the left and right ventricles
Left coronary artery - 2 branches and what they suply
- branches into 2 arteries;
1) Anterior interventricular artery (aka left anterior descending artery) - supplies anterior surface of both ventricles and most of interventricular septum
2) Circumflex artery - supplies left atrium and ventricle
Coronary Veins
- 3 major veins
- what they all drain into
- Venous return of blood from heart muscle walls
- occurs through 3 major veins;
1. Great cardiac vein
2. Middle cardiac vein
3. Small cardiac vein - all three drain into large vein (called coronary sinus) that drains into right atrium
Composition of myocaridum
- composed of cardiac muscle fibres
- contract as a single unit - all connected w/ low resistance cell-to-cell junctions called gap junctions
- gap junctions comprise the intercalated discs (shared by adjacent cardiac muscle fibres)
- electrical impulse distributed immediately & spontaneously throughout myocardium
Conducting system of the heart
- how it contracts
- Sinoatrial node - what it does
- Atrioventricular node
- how impulse travels w/in heart
- Contracts autorhythmically (initiates own heartbeat external of nerves)
- Electrical impulse comes from specialised cardiac muscle = Sinoatrial (SA) node (or pacemaker)
- located on posterior wall of right atrium (adjacent to opening of superior vena cava)
- SA node generates 70-80 impulses per minute under parasympathetic control
- Impulses travel to left atrium & atrioventricular (AV) node located in floor of right atrium
- electrical activity leaves AV node into AV bundle which extends into interventricular septum -then divides into left and right bundles
Purkinje fibres
- Left and right bundles w/in septum pass impulse to conduction cells called Purknje fibres - begin at apex of the heat
- spread impulse superiorly from apex to all of the ventricular myocardium
Systole & Diastole
Systole = contraction of the heart Distole = relaxation of the heart - when each chamber relaxes and chamber fills with blood
Coordinated sequence of heart chamber contractions (4)
- SA node generates an impulse
- Both atria contract almost simultaneously while ventricles are relaxing
- Impulse goes to AV node and then to the ventricles
- Ventricles contract while atria relax
