5 The heart Flashcards
What is the shape of the pericardium?
Conical shaped
What is the pericardium continuous with?
With pretracheal layer of cervical fascia superiorly
Nb function of pericardium
Shock absorber (cardiac seatbelt), prevents over expansion when blood increases and limits heart movements
Layers of pericardium
- Fibrous
- Serous
Outermost layer of pericardium
Fibrous
Describe fibrous layer
Irregular dense connective tissue with much collagen
Function of fibrous layer
To anchor heart to diaphragm and the great vessels
Serous pericardium layers
- Parietal
- Visceral
What is the parietal layer attached to?
Fibrous pericardium
What is the visceral attached to?
To surface of the heart and aorta, pulmonary trunk, vena cavae (epicardium)
What do the lines of reflection between visceral and parietal pericardium form?
Two pericardial sinuses – oblique and transverse
What is the pericardial cavity filled with?
With serous pericardial fluid, really a potential space containing 10-20 mls of pericardial fluid
Function of pericardial cavity being lubricated?
Prevents friction as the heart beats
Inflammation of the pericardium
Pericarditis
Where is the transverse pericardial sinus located?
Anterior to the SVC and post to the Ascending aorta and Pulmonary Trunk
What does the transverse pericardial sinus seperate?
The arterial vessels (A, PT) and the venous vessels (SVC, PV)
What can the transverse sinus be used to locate?
The arteries of the heart during coronary artery bypass grafting.
What is the oblique sinus bound by?
The lines of reflection of the serous pericardium onto the
inferior vena cava and the left and right pulmonary veins
Cardiac tamponade long
The relatively inextensible fibrous pericardium can cause pericardial effusion (increased fluid) in the pericardial cavity. Increased pressure. The chambers can become compressed, thus compromising cardiac output.
Haemopericardium (bloodin the pericardium) and pericarditis
Arterial blood of pericardium
- Internal thoracic - Musculophrenic and pericardiophrenic branches
- Descending thoracic aorta from bronchial, oesophageal and superior phrenic arteries
Venous blood of pericardium
Venous drainage to azygous system
Nerves of pericardium
Phrenic nerve to fibrous and serous pericardium / visceral is vagus and sympathetic trunks (insensitive to pain)
3 layers of the heart from out - in
- Epicardium
- Myocardium
- Endocardium
Describe epicardium
- Visceral layer of pericardium
- Adipose and fibroelastic tissue
What is endocardium ?
- Endothelial cells
- Smooth lining also covering the valves.
Where are cardiac muscle fibres anchored to?
To the fibrous skeleton of the heart.
Functions of the skeleton of heart x 3
- Prevent over distension of valves
- Serve as attachments of leaflets and cusps
- Provide electrical insulation from atria and ventricles
Framework of skeleton of heart
Framework of dense collagen forming four fibrous rings (L. annuli fibrosi) that surround the orifices of the valves 2 rings and 2 cononets
What are sulci?
Grooves on surface of heart containing coronary blood vessels and fat
x 3 sulci
- Coronary sulcus
- Anterior interventricular sulcus
- Posterior interventricular sulcus
Coronary sulcus marks
Encircles heart and marks the boundary between the atria and the ventricles
What does the anterior interventricular sulcus mark?
Marks the boundary between the ventricles anteriorly
What does the posterior interventricular sulcus mark?
The boundary between the ventricles posteriorly
Myocarditis
inflammation due to infections, chemicals, medication
- Often caused by viral infection
- Need for biopsy
- Mild disease, chest pain to heart failure, or sudden death
Endocarditis
Inflammation usually involving the valves (bacterial endocarditis)
Infective endocarditis
- Bacterial infection
- Valves, septum, chordae tendinae
- Most common cardiovascular infection worldwide
Left coronary artery pathway
Arises from left posterior aortic sinus and passes forward between the left auricle and infundibulum
Artery in the interventricular groove
Anterior descending interventricular groove
SA nodal percent
40%
SA nodal artery percent
60%
Circumflex branch location and supplies
In coronary sulcus, supplies left atrium and left ventricle – sometimes AV node (left dominant)
Branches of anterior descending interventricular artery
Conus branch and diagonal branch
Right coronary artery course
Ant aortic sinus travels between infundibulum of the right ventricle and the right auricle to AV groove
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What does the right coronary artery supply?
- The right atrium.
- Most of right ventricle.
- Diaphragmatic surface of the left ventricle
- Part of the IV septum, usually the posterior third.
- The SA node (in approximately 60%).
- The AV node (in approx 70 80%).
What does the left coronary artery supply?
- The left atrium.
- Most of left ventricle.
- Part of right ventricle.
- Most of IVS (usually its anterior two thirds), including the AV bundle through its perforating IV septal branches.
- The SA node (in approx 40%).
What drains to the great cardiac vein?
Posterior, the oblique vein, middle and small cardiac veins
Where does the great cardiac vein drain into?
Coronary sinus
Where does the coronary sinus empty into?
Right atrium
Right pump circulation
Pulmonary circulation
Left pump circulation
Systemic and coronary circulation
Right pump describe blood flow
- Atrium receives de-oxygenated blood from systemic and coronary circulation
- Blood passes to ventricle before being sent to the lungs
Left pump describe blood flow
- Atrium receives oxygenated blood from pulmonary circulation
- Blood passes to ventricle before being sent to the body and heart
Where does the right atrium receive blood from?
From the superior and inferior vena cava and coronary sinus
What is fossa ovalis?
A remnant of the embryonic inter-atrial circulation
What is the posterior wall of the right atrium like?
Smooth
What is the wall of the right atrium other than the posterior wall like?
Ridged by pectinate muscles
Where is the sulcus terminalis and what is it produced by?
Between SVC and auricle produced by crista terminalis on lateral wall bxn vena cava
What is the right ventricle separated from the atrium by?
By a tricuspid atrioventricular valve.
What is the tricuspid valve opened by?
Opened by contraction of papillary muscles pulling on chrodae tendinae
What is the inflow tract of right ventricle like?
Rugged - Trabeculae carnae
What is the outflow tract of right ventricle like?
Smooth
What is the outflow tract of right ventricle like?
Smooth
What is the outflow to pulmonary trunk controlled by?
Pulmonary valve (semilunar valve)
What does the pulmonary trunk split into?
The right and left pulmonary arteries (de-oxygenated blood)
Cusps of tricuspid valve/
Anterior cusp
Posterior cusp
Septal cusps
- attached to the fibrous AV ring
What are the walls of the left atrium like?
Both smooth
Auricle of left atrium?
A small out pouching extension which has pectinate muscles
What deos the left atrium open into and regulated by>
Opens into left ventricle and regulated by the bicuspid valve.
What is the left ventricle separated from the atrium by?
By bicuspid atrioventricular valve
Where are the anterior and posterior cusps attached to?
To fibrous AV ring
What is the bicuspid valve opened by?
By contraction of papillary muscles pulling on chordae tendinae - ant and post
What is the inflow tract of left ventricle like?
Rugged - Trabeculae carnae
What is the outflow tract of left ventricle like?
Smooth
What is the thickest part of the heart?
Wall of left ventricle
What is the outflow to aorta controlled by?
Aortic valve (semilunar valve)
Where do coronary arteries branch off?
The ascending aorta
Nervous system innervation of the heart
Autonomic nervous system
What does the parasympathetic system do to activity and act via?
Inhibits activity - vagus nerve
Acts via acetlycholine
What is the cardiac plexus?
A collection of parasympathetic and sympathetic nerve fibres (inferior aortic arch)
What does the sympathetic system do to the heart and act via?
Enhances activity - sympathetic trunk
Acts via release of norepinephrine and epinephrine
What accompanies sympathetic nerves?
Afferent (sensory nerve fibres)
What occurs in the relaxation period?
Ventricles are relaxed and blood flows from the atria to the ventricles
What occurs in atrial systole?
Atria contract to completely fill the ventricles
What occurs in ventricular systole?
Ventricles contract to push blood of out the heart
Nerve signals through heart (from cardiac muscle fibres)
- SA node generates action potential that spreads through both atria, synchronising their contraction.
- SA node signal to AV node is delayed ensuring time for atria to empty into ventricles
- AV node signal spreads throughout the ventricles which contract to expel the blood
(Via bundles of His and Purkinje fibres)
Describe atrial fibrillation (AF)
- The most common sustained cardiac arrhythmia
- Maintained by reentry and/or rapid focal ectopic firing
- Potential for blood clot
- Heart palpitations, shortness of breath and weakness
Describe ventricular fibrillation (VF)
- Most serious cardiac rhythm disturbance
- Most commonly identified arrhythmia
- Uncoordinated contraction of ventricular endocardium
Valve disorders x 3
- Genetic, bacterial infection
- Incompetent valve (failure to completely close)
- Stenotic (narrowed opening)
What is bradycardia?
When the heart rate is too slow - less than 60 beats per minute
What is tachycardia?
When the heart rate is too fast - more than 100 beats per minute
Heart disorders x 5
- Coronary artery disease
- Heart failure
- Fibrillations
- Transposition of the great vessels
- Septal defects
What is coronary artery disease
Blockage of coronary arteries
- Angina pectoris
- Myocardial infarction
What is heart failure?
Weakening of heart muscle
Types of fibrillations
Atrial and ventricular fibrillations
