Cardiac Anatomy & Coronary arteries Flashcards
Describe the pericardium
3 layered sac
Fibrous pericardium: dense connective tissue
- protective layer
- attached to great vessels (aorta, pulmonary arter&vein)
- Attached to diaphragm
- Anchors heart in plcae
Serous pericardium
- Parietal attached to fibrous layer
- Visceral attached to surface of the hart (epicardium): allows the smooth movement of the myocardium- beats or movement of heart
What is the function of pericardium
- Fixes heart in mediastinum and limits movement
- Protection from infections coming from other organs (such as lungs)
- Prevents excessive dilation of heart in cases of acute volume overload
- Lubrication: allow free movement of heart with the pericardial sac
What is pericardial effusion/tamponade
Fibrous pericaridum:
- Normally restricts overexpansion
- But if fluid gathers between parietal and visceral pericardium the heart has no where to go
Accumulation of fluid under high pressure
Management: Pericardiocentesis
Indication for pericardiocentesis:
- A pericardial effusion causing tamponade (RV free wall collapse during diastole)
Decrease SV -> decrease CO-> hypotension/shock (reflex tachycardia)
incr
Describe the heart wall layers
- Epicardium
- Visceral layer of serous pericardium - Myocardium
- Cardiac muscle fibres: arranged in bundles, squeezes blood out of herat - Endocardium
- Continous with endothelium
- Lines chamgers and valves
Trace the flow of blood through the heart and identify the great vessels
Is the volume of blood propelled by the right ventricle the same as that
Superior vena cava, Inferior vena cava
Coronary sinus
Right atrium
Tricuspid valve
Right ventricle
Pulmonary semilunar valve
Pulmonary trunk
To lungs
Pulmonary capillaries
To heart
Four pulmonary veins
Left atrium
Mitral vavle
Left ventricle
Aortic semilunar vavle
Aorta
To body
Systemic capillaries
To heart
Describe the arrangement and the main features of the chambers of the heart
External landmarks
- Coronary groove (atrioventricular sulcus)
- Between atria and ventricles - Anterior interventricular sulcus
- Between right and left ventricle - Posterior interventricular sulcus
- Between right and left ventricle
What does the right atrium and the left atrium consist?
Right:
1. SVC,IVC
2. Right auricle
Left:
1. 4 pulmonary veins
2. Left auricle
Coronary groove: oblique plane which separates atria and ventricle
What does the right and left ventricle consist of?
Right:
1. 2/3 anterior
2. Pulmonary truncle
Left:
1. Apex (left border)
2. Inferior surface (2/3 post)
3. Aorta
Interventricular groove: overlies interventricular septum which separates left adn right ventricle
What does the right atrium and ventricle consist?
- Right border and anterior surface
- SVC,IVC and cornary sinus
- Smooth walled posteriorly, rough anteriorly
- Fossa ovalis:closed holes from the fetus stage (passes blood from right to left as it doesn’t need to go through the lungs)
- Tricuspid valve
- Valve cusps
- Cordae tendineae
- Papillary muscles - Trabeculae carnae
- Trabeculae: pole like, rod like cluster of blood vessels - Pulmonary trunk
What is the internal landmarks of the right atrium
- SVC
- Fossa ovalis
- IVC
- Cristae terminalis
- Pectinate muslce
- Tricuspid valve
What is the internal landmarks of the right ventricle
- Tricuspid valve
- Septal
- Chordae tendinae
- Trabeculae carnae
- Ant/Post. papillary muscle
- Moderator band
- Septal papillary muscle
- Pulmonary valve
- Pulmonary trunk
What does the left atrium and ventricle consist of?
- Posterior or base of heart
- 4 pulmonary veins
- Smooth walls excluding pectinate muslce in elft auricle
- Fossa ovalis
- Mitral valve: chordae tendineae, papillary muscle
- Trabeculae carnae
- Thicker myocardium
- Ascending aorta: aortic semilunar valve
What is the coronary blood supply?
Arterial supply
- Coronary arteries: right and left
Supply both the atria and ventricles
Coronary arteries
- Right anastomoses with circumflex branc of LCA
- After RCA has given rise to post interventricular artery - LAD loops around apex and anastomoses with post interventricular artery
- Dominance
- Determined by the artries that supply the posterior and inferior wall of the left ventricle
- Approximately 60% of the general population are right dominant, 25% are co-dominant and 15% are left-dominant
What is the anatomy of coronary arteries
Clinical anatomy of the heart
- Myocardial infarction
- LAD off LCA 40-50%
- RCA 30-40%
- Circumflex of LCA 15-20% - May damage conudcting system
- LAD to septal branches supplying AV node
- RCA supplies both SA and AV nodes: heart block
Function and anatomy of coronary veins
- Venous drainage from cardiac muscle
- Drains into coronary sinus on posteriro surface of heart
- Coronary sinus empties into right atrium
Fibrous skeleton of the heart
- Dense connective tissue surrounds AV and outflow vessels valves
- Fuse together and merge with interventricular septum
- Support the valves
- Prevents overstretching of the valves
- Insertion point of cardiac muscle bundles
- Electrical insulator between atria and ventricles
What happens in diastole?
Diastole-ventricular filling
1. AV valves open and allow blood to flow from atria into ventricles when ventricular pressure is lower than atrial pressure
2. Occurs when ventricles are relaxed
3. Chordae tendinae are slack
4. Papillary muscles are relaxed
What happens in systole?
- AV valves close preventing backflow of blood into atria
- Occurs when ventricles contract
- Pushing valve cusps closed
- Chordae tendinae are pulled taut
- Papillary muscles contract to pull cords and prevent cusps from everting
What is the function of semilunar valves?
- Three cusps
- Prevent backflow from aorta and pulmonary trunk into ventricles
- Passive action
- Systole of ventricles open valves
- Diastole of ventricles: decrease in BP, backflow fills cusps and closes vavle
Describe the heart conducting system
- The sinoatrial (SA) node (pacemaker) generates 70-80 impulses per minute, atria contract
- The impulses pause (0.1 sec) at the AV node so ventricles have time to fill
- The atrioventricular (AV) bundle connects the atria to the ventricles
- The AV bundle branches conduct the impulses through the interventricular septum
- THe Purkinje fibres stimulate the contractile cells of both ventricles, starting at apex and moving superiorly
What consists in the heart conducting system?
- Cardiac muscle fibers form 2 networks via gap junctions at intercalated discs: atrial network, ventricular network
- Separated by fibrous skeleton
Describe the innervation of the heart
- Heart is supplied by the cardiac plexus
- Lies anterior to the bifurcation of the trachea and posterior to the arch of aorta
- Cardiac plexus contains:
- Parasympathetic (from vagus)
- Sympathetic (from sympathetic trunk) - Fibres extend from the plexus to the coronary vasculate and to components of the conducting system of the heart (especially SA node)
Describe the sympathetic innervation of the heart
- Increase heart rate
- Increase force of contraction
- Cardioaccelaratory centre: medullary reticular formation
- Preganglionic symptathetic neruons in thoracic spinal cord
- Postganglionic sympathetic neurons to SA&AV node and to coronary VSM
Describe the parasympathetic innervation
- Slows heart rate
- Pathway
- Reticular formation in medullar (cardioacceleartory centre)
- Vagus nerve (CN X)
- To SA&AV node
Cardiac Pain
- Pain not felt in heart-referred
- Pain caused by ischaemia and damage to cardiac muscle
- Stimulates visceral sensory nerve endings in myocardium
- Visceral afferent nerve fibres ascent to the CNS through cardiac brances of the sympathetic trunk and into CNS
[organ and skin pain fibres travel to spinal cord together]
[generally referred {interpreted} as if it came from somatic areas]
[skin supplies by T1-5 L side of chest, neck, face, left arm]
- For infarct on inferior wall (referred) [to epigastrium: T7,8, and 9]
