Module Two - The Heart Flashcards
Describe the hearts location
the heart sits in the mediastinum (the medial cavity of the thorax, between the plural cavities). The heart rests on the diaphram, posterior to the sternum and anterior to the vertebral column.
Desrcibe the base of the heart
- superior wide surface
- where blood vessels attach
- levels of 2nd and 3rd costal cartilage
- centred 1.2cm left of midline
Apex
- inferior tip
- 12-14cm from base
- sth intercostal space
- 7.5cm from midline
What are the coverings of the hear?
Heart us enclosed by a double walled sac = pericardium
- outer parietal pericardium
- inner visceral pericardium
- pericardial space containing pericardial fluid
What are the three layers of the heart wall?
- epicardium (=visceral pericardium)
- Myocardium (muscular wall)
- Endocardium (endothelium covers inner surface of the heart)
Describe the external structures of the heart
> Two superior atria (thin, receiving chambers)
> two inferior ventricles (thick, discharging chambers) externally separated by the interventricular sulcus
What vessels bring blood back to the right atria?
Recieves deoxygenated blood from:
- Superior vena cava
- inferior vena cava
- coronary sinus
What vessels bring blood into the left atrai?
Recieves oxygenated blood from:
- right and left pulmonary veins (from the lungs)
What are the internal structures of the heart?
Similar to external.
> atria (right atrium receives coronary blood
> ventricles (separated from atria by AV valves which are anchored via the chordae tendineae attached to papillary muscles in ventricle walls)
> trabeculae carneae (muscular ridges)
> blood exists via semilunar valves
What are heart vavles and their names?
Flaps of endocardium reinforced by a core of connective tissue.
> AV valves
> Semilunar vavles
valves open and close in response to pressure changes
and ensure one way blood flow.
What do the AV valves do?
- prevent backflow of blood into the atria when ventricles contract
- chordae tendineae tense, via contraction of papilary muscles, preventing AV valves from everting into atria
What do the SV valves do?
- forced open when ventricles contract
- close when ventricles relax and blood in the arteries tries to flow backwards
What is coronary circulation?
supplies blood to the myocardium (blood flowing through the heart does not supply the needs of the heart tissue)
Where do the left and right coronary arteries arise from? and what do they give rise to?
They arise from the base of the aorta and circle the heart in the coronary sulcus.
Left CA gives rise to the anterior interventricular artery (supplies anterior ventricles)
Right CA gives rise to posterior interventricular artery (posterior ventricles)
What do the great cardiac vein and middle cardiac vein do?
Great CV: drains the anterior regions supplied by the anterior interventricular artery
Middle CV: drains the posterior area supplied by the posterior interventricular artery
Where do all veins drain into?
Coronary sinus - an expanded vein that drains into the right atrium
What are the two coronary artery diseases?
Angina pectoris and Myocardial infarction
What is angina pectoris?
A temporary deficiency in myocardial blood supply, characterised by thoracic pain. Caused by increased physical demand on the heart. Myocardial cells weakened but dont die.
What is myocardial infarction?
Prolonged coronary artery blockage, characterised by various symptoms. Ischaemic myocardial cell death
What are the left and right heart pumps called?
right: pulmonary pump
left: systemic pump
How does blood flow?
down its pressure gradient, from an area of high pressure to low pressure
Blood flow
- blood moves into both atria at the same time
- blood exits both ventricles at the same time
Describe the pulmonary circuit
- supplied by the right ventricle
- short, low pressure circulation
Describe the systemic circuit
- supplied by the left ventricle
- long, high pressure circulation
- encounters 5x more resistence than PC
- must generate more force than right ventricles
Which two ways are the activites of the heart modified?
> autonomic nervous system (extrinsic innervation)
> its own electrical system (instrinsic conduction system)
How does the heart stimulate its own contractions?
via the intrinsic conduction system.
Cardiac muscle cells have specialised connections - action potentionals in one muscle cell can be conducted to the next muscle cell - allows coordinated activity.
What are the components of the intrinsic conduction system?
- sinoatrial node
- atrioventricular node
- atrioventricular bundle
- bundle branches
- purkinje fibres
Which node is know as the pacemaker of the heart?
SA node
What does extrinsic innervation refer to?
autonomic nervous system modifies the activity of the heart.
What are the two cardiac centres which are crutial to extrinsic innervation?
- cardioacceletory centre: increased heart rate and force of contraction (sympathetic input via thoracic spinal cord to SA, AV node, myocarium and coronary arteries) causes dialation.
- Cardioinhibitory centre: decreases heart rate (parasympathetic input via vagus nerve to the SA and AV nodes
both in the medulla oblongata
ECG
P wave: depolarisation of the atria, beginning of the SA node
QRS complex: depolarisation of the ventricles. atrial depolarisation is masked by this complex
T wave: repolarisation of the ventricle
What can an ESG help determine?
- if the conduction pathway is normal
- if the heart is enlarged
- if certain regions of the heart are damaged
- the cause of chest pain
what is systole?
periods of contraction
what is diastole?
periods of relaxation
What does ausculation mean?
listening to body sounds
What is the S1 sound of the heart called?
lubb
What is the S2 sound of the heart called?
Dupp
What is a heart murmur?
swishing sound as blood backflows through an incomplete valve
What is end diastolic volume?
the volume of blood in the ventricles just prior to contraction
What is end systolic volume?
the volume of blood in the ventricles at the end of contraction
What is the goal of cardiovascular function?
the maintenance of adequate blood flow (i.e. oxygen) to vital tissues/organs
What is cardiac output?
A measure of peripheral blood flow. the volume of blood pumped by the left (or right) ventricle in one minute.
CO = stroke volume X heart rate
What is heart rate?
number of beats per minute
What is stroke volume?
volume of blood ejected from the left (or right) ventricle per beat
What are the factors that affect CO?
> anything that affects HR or SV will affect CO
as SV= EDV-ESV it is affected by changes in EDV or ESV
heart rate us affected by autonomic NS, hormones etc.
What is the EDV determined by?
- venous return: amount of blood returing to the heart from the systemic or pulmonary circuit - depends on
> total blood volume
> patterns of blood flow - passive filling time: time bth atria and ventricles are in diastole
What is the preload?
the degree the myocarium is stretched before contraction - determines force of ventricular myocardial contraction - determines SV
MORE BLOOD IN = MORE BLOOD OUT
What factors affect SV?
- Contractability: amount of force produced during a contraction.
- Afterload: pressure that the ventricles must overcome to open the SV to eject blood into the arteries
Why is HR rapidly altered?
to meet the needs of tissues/ organs and to compensate for changes in SV
How is HR altered?
- ANS
- hormones
- body temp.
- plasma electrolytes
What is the average HR?
75bpm (80 bpm)
