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Life sciences for paramedics > The anatomy and physiology of the circulatory system > Flashcards

The anatomy and physiology of the circulatory system Flashcards

1
Q

Heart location

A

-mediastinum- extends from sternum anteriorly to the vertebral column
-lies medially between lungs
-2/3 mass is to the left of midline
-base (top) of heart tipped up medially and posteriorly
-apex projects inferiorly and laterally

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2
Q

The pericardium
what is it, what it does, what its composed of

A

-membrane surrounds the heart
-helps retain hearts position within mediastinum
-composed tough outer fibrous layer and lined by delicate serous membrane
-serous membrane divided into parietal layer (outer) and visceral layer (inner)
-between these layers there’s serous fluid

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3
Q

Layers of heart wall

A

-epicardium- thin, transparent outer layer, also called visceral layer of pericardium
-myocardium- thick middle layer, composed of cardiac muscle
-endocardium- squamous epithelium, known throughout circulatory system as endothelium

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4
Q

Atrial kick

A

-when atria contract
-responsible for only a 20% increase in amount of blood ejected by the ventricles

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5
Q

Heart valves

A

-atrioventricular valves- between atria and ventricles
-outflow/ semi lunar valves- from ventricles to outflow vessels

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6
Q

Atrioventricular valves

A

Right AV valve= tricuspid valve as has 3 leaflets/ cusps
Left AV valve= bicuspid/ mitral valve

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7
Q

Outflow valves

A

-right= pulmonary valve
-left= aortic valve

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8
Q

How heart valves (av) work by preventing backflow

A

-AV valves tethered to walls of ventricles by heart strings/ chordae tendinae attached to papillary muscles
-papillary muscles pull on AV valves via chordae tendinae, slowing their closure and preventing damage to valve

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9
Q

Outflow valves

A

-firm cusps that each look like a semi full moon
-each cusp makes up a third of the valve

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10
Q

Why there are no valves between vena cava and right atria and pulmonary vein and left atria

A

-small amount of blood does flow backwards
-but minimised by the way the atria contracts
-this compresses and nearly collapses the vessels

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11
Q

Arteries

A

-blood away form heart
-contain oxygenated blood
-thick walls, exposed to high pressures and friction forces
-outer layer= tunica externa
-middle layer= tunica media
-inner layer= tunica interna/ endothelium

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12
Q

Veins

A

-blood back to heart
-contain deoxygenated blood
-thin walls as exposed to low pressures and minimal friction forces
-same 3 layers as artery- tunica externa, media, interna
-layers just not as thick as an artery
-valves

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13
Q

Arteries and vein that attach to heart

A

-arch of the aorta
-pulmonary trunk
-coronary arteries
-superior and inferior vena cava
-4 pulmonary veins
-coronary sinus

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14
Q

Arterioles- 3 layers and structures

A

-thin tunica interna with thin fenestrated elastic lamina
-tunica media consists of one or two layers of smooth muscle cells
-tunica externa consists of connective tissue and sympathetic nerve supply that can vary the rate of flow

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15
Q

Capillaries

A

-smallest vessels
-one RBC through at a time
-allow exchange of substances between blood and interstitial fluid
-lack tunica media and externa
-single layer endothelial cells

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16
Q

Systemic circuit

A

-ejects blood into aorta, systemic arteries, and arterioles, powered by left side of heart

17
Q

Pulmonary circuit

A

-ejects blood into pulmonary trunk, powered by right side of heart

18
Q

Coronary circulation

A

-passive process
-blood flows through coronary arteries only during relaxation phase of ventricular diastole
-LCA- goes to anterior interventricular and circumflex branches
-RCA- to marginal and posterior atrioventricular branches
-coronary veins collect in coronary sinus at the back of heart
-coronary sinus empties into right atrium to be oxygenated by lungs

19
Q

Cardiac muscle tissue

A

-shorter fibres than skeletal muscle
-branch
-only have on centrally located nucleus
-communicate with neighbouring cells through gap junctions in intercalated discs

20
Q

Autorhythmicity

A

-doesn’t rely on CNS
-just happens automatically
-autorhythmic cells spontaneously depolarise
-when they reach the threshold, an AP is reached causing all cells in that area to depolarise

21
Q

Myocytes- 2 roles

A

-form the conduction system
-act as pacemakers

22
Q

Normal pacemaker of the heart
name, why, location

A

-sino atrial node (SAN)
-due to fastest rate of depolarisation
-located right atrial wall

23
Q

How often the SA node fires

A

-once every 0.8 seconds or 75 AP per min

24
Q

Cardiac conduction

A

-AP generated at SAN
-then propagates throughout wall of atria via the bachmann’s bundle to the AVN in the interatrial septum
-at AVN, signal is slowed allow atria chance to mechanically move blood into ventricles
-spreads down bundle of his which separates to the right and left bundle branches to the purkinje fibres

25
Q

How contractions are coordinated

A

-band of muscle wind around the heart, working as a unit
-this forms a functional syncytium
-this allows the top and bottom parts to contract in their own way

26
Q

Role ANS

A

-regulate changes in BP, blood flow and blood volume
-maintain enough cardiac output to provide for all organs

27
Q

Refractory period

A

-longer than the contraction itself, unlike skeletal muscle
-therefore tetanus (maintained contraction) cannot occur in cardiac muscle

28
Q

ECG

A

Electrocardiogram
-records electrical changes on surface of the body caused by depolarisation and repolarisation of myocardium
-measures presence or absence of certain waveforms

29
Q

PQRST waves

A

P= atrial systole
QRS= ventricular systole
T= diastole/ repolarisation of ventricle
PQ interval- excitation goes from SAN to AVN for the pause to occur

30
Q

Cardiac cycle

A

-includes all events associated with one heartbeat
-systole and diastole
-during atrial systole, ventricles are relaxed and vice versa
-lub (S1)= closure of mitral and tricuspid valves
-dub (S2)= closure of aortic and pulmonary valves

31
Q

Average stroke vol

A

70 ml

32
Q

Cardiac output calculation

A

stroke volume x heart rate
resting adult= 70ml x 75bpm= 5.25 l/min
-on average whole blood volume flows through pulmonary and systemic circuits every minute

33
Q

3 factors affect stroke volume

A

-amount of ventricular filling before contraction (preload)
-contractility of ventricle
-resistance in blood vessels the heart is pumping into (afterload)

34
Q

Cardiac reserve

A

-difference between cardiac output at rest and the maximum cardiac output the heart can generate

35
Q

Starlings law of the heart

A

-the more the heart muscle is preloaded/ stretched, the more forcefully the heart will contract

36
Q

Functions of blood

A

-transportation- O2, CO2
-regulation- pH, temp
-protection- clotting, immune system

Life sciences for paramedics (18 decks)

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