Cardiovascular system Flashcards
(154 cards)
1
Q
A
2
Q
2 loops of circulation
A
pulmonary circulation and systemic circulation
3
Q
Describe the pulmonary circulation
A
Oxygen depleted blood
Passes from heart to lungs
Returns oxygenated vlood to heart
4
Q
Describe systemic circulation
A
Oxygen rich blood
Passes from heart to rest of body
Returns deoxygenated blood to heart
5
Q
Describe the superior mediastinum
A
Upper portion - T1 posteriorly - superior aspect of mediastinum
Lower portion - sternal angle - landmark for 2nd rib
6
Q
Describe the inferior mediastinum
A
Anterior (fat and thymus)
Middle (heart)
Posterior (aorta, oesophagus)
7
Q
Describe the two types of pericardium
A
Fibrous - tough outer layer which anchors the heart to the diaphragm. prevents rapid overfilling of the heart but can also restrict if there is an accumulation of fluid compressing the heart, especially the right and reducing CO
Serous - this in itself has two layers; an inner visceral layer and an outer parietal
8
Q
What travels through the SVC
A
deoxygenated blood from head and nack and upper limbs
9
Q
what travels through the IVC
A
deoxygenated blood from below level of heart, eg. abdomen, pelvis, lower limbs
10
Q
Order of aortic structures from the patients right to left (doctors left to right)
A
Coronary arteries
Brachiocephalic trunk
Left common carotid artery
Left subclavian artery
11
Q
Function of Ductus Venosus
A
Allows blood to bypass liver to the inferior vena cava. At birth this closes and becomes the ligamentum venosum
12
Q
Function of foramen Ovale
A
Allows blood to flow from the right atrium to the left atrium
13
Q
Function of ductus arteriosus
A
Links the pulmonary artery with the aorta to redirect blood from non-functioing lungs in utero
14
Q
Function of umbilical arteries
A
Carry deoxygenated blood back to the placenta
15
Q
fossa ovalis
A
embyological remnant of the patent foramen ovale in foetal life. Used to allow blood to flow between the right atrium and the left atrium.
16
Q
Aortic sinuses
A
dilatations just above the aortic valve. There are 3 of these and from 2 arise the left and right coronary arteries
17
Q
Right atrial appendage
A
additional part of the right atrium. Used as the site for an external pacemaeker to be postitioned.
18
Q
Crista terminalis
A
at the opening of the right atrial appendage and is the site of origin of the pectinate muscles
It acts as a landmark, separating the sinus venarum (smooth, posterior part) from the original atrial chamber (rough, anterior part)
19
Q
Musculi pectinati
A
allow for stretch and improve the volume of the right atrium
20
Q
orifice of coronary sinus
A
where the venous blood from the heart enters
21
Q
pulmonary veins
A
2 on left and 2 on right carrying oxygenated vlood to the left atrium.
22
Q
interventricular septum
A
big muscle that divides right and left ventricles
23
Q
describe ASDs/VSDs
A
present at birth. Small holes sometimes close themselves, and larger ones will compromise the heart and lungs due to increased blood pressure
24
Q
AVSD
A
Atrioventricular septal defect
Requires surgery as it will compromise the patient leading to problems breathing, racing heart, weak pulse and cyanosed (blue), tiring easily
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tricuspid valve
3 leaflets
Right atrioventricular valve
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Mitral valve
2 leaflets
left atrioventricular
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what prevents valves from opening
papillary muscle contraction which tightens chordae tendineae
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semilunar valves
half-moon shaped structures
aortic and pulmonary valves
no chordae tendineae
hold blood to prevent backflow into ventricles
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hearts blood supply
coronary arteries
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ischaemia
reduction in oxygen due to narrowing of the arteries
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Infarction statistics
Anterior intraventricular branch of left coronary artery: 40-50%
Right coronary artery: 30-40%
Circumflex branch of LCA: 15-20%
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Longest vein in the body
Saphenous vein - from lower limb
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Describe CABG
Coronary artery bypass graft
Done to bypass cholesterol buildup
Saphenous vein used as its so long, but as a vein with valves it must be flipped
OR
Internal mammary artery used which is sometimes preferred as its an artery doing an artery's job
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Sinoatrial node
Generates electrical signals and is the pacemaker of the heart
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Moderator band
Allows for more rapid conduction across the anterior papillary muscle and helps with conduction sinuses
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Purkinje fibres
Specialised conducting fibres, bigger than cardiac myocytes and create a synchornised contraction across the ventricles
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Functions of respiratory system
Conduction of air (warms and humidifies)
Respiration (gas exchange)
Protection against pathogens (mucous)
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Upper respiratory tract
Nasal cavity, pharynx, larynx
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Lower respiratory tract
Trachea, Primary bronchi, lungs
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Nasopharynx
base of skull to bottom of soft palate (uvula in mouth)
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Oropharynx
soft palate (uvula) to epiglottis (elastic cartilage)
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laryngopharynx
epiglottis to where the bifurication occurs to the oesophagus and the trachea
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differences between right and left bronchus
Right - more vertical, greater diamter, shorter than left main bronchus. Foreign bodies more likely to go to right
2 lobes of bronchi in right, 3 in left
right lobe has horizontal and ovlique fissure, left only has oblique
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respiratory epithelium
pseudostratified ciliated columnar epithelium with goblet cells (secrete mucous)
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surfactant
secreted by the type II pneumocytes and increases lung compliance and prevents collapse, or atelectasis ot the lungs at the end of expiration. Produced from weeks 24-28 and enough production occurs by week 34 out of 40 gestation
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Hilum function
holds together in place the bronchus, pulmonary arteries and pulmonary veins
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advantages of ultrasounds
no ionising radiation
portable
real-time images
dynamic assessment of structures
easy intervention (guiding line placment)
cheaper equipment
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4 types of ultrasound probe
Convex, Linear, Phased array, Endocavity
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Convex probe
Wide field of view
good penetration
abdominal organs, pregnancy
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linear probes
good resolution for superficial structures
musculoskeletal, breast, thyroid, vascular
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phased array probe
small footprint, fast frame rate
cardia (echocardiogram)
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endocavity probe
shape - assess structures via cavity
transvaginal, transrectal, transoesophageal, endobrachial
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How is ultrasound image produced
electrical pulses converted to ultrasound waves by array of crystals in transudecer
waves transmitted into soft tissues
waves reflected at acoustic interfaces of differing echodensity between/within tissues
returning ultrasound waves converted into electric signal again
machine builds the image on the screen dot by dor
- larger amplitude: brighter
- longer return time: deeper
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Term for ultrasound shades
Black - Anechoic
Dark gray - Hypoechoic
Light grey - Isoechoic
White - Hyperechoic
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Anechoic structures
Fluid filled structres reflect almost no sound waves back = black
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Hyperechoic structures
Strongly reflective, ie, bone
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High and low frequency on resolution and penetration
High Frequency: high resolution, lower penetration
Low frequency: low resolution, higher penetration
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functions of Cardiovascular system
Transport of nutrients, oxygen and waste
Thermoregulation
pH buffer
Transport of hormones
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LVEDP
Left ventricle end diastolic pressure
Pressure in left ventricle right before it contracts
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7 phases of cardiac cycle
Atrial Systole
Isovolumetric contraction
Rapid ejection
Reduced ejection
Isovolumetric relaxation
Rapid filling
Reduced filling
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Describe Atrial systole
- AV valves opne, Aortic and pulmonary valves closed
- SA node initiates P wave on ECG
- Active filling to top-up ventricle: 'a wave'
- Contributes 10-40% of LV filling
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Describe isovolumetric contraction
- All valves closed
- QRS complex; LV depolarisation
- LV ; papillary muscles contract
- AV valves close (S1 sound)
- rapid increase in pressure
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Describe structure of arteries
Tunica externa, external elastic lamina, tunica media, elastic membrane, tunica intima (from superficial to deep)
Thick muscle layers
highly elastic
contains 17% of blood
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Describe the structure of veins
Tunica externa, external elastic lamina, tunica media, elastic membrane, tunica intima (from superficial to deep)
Thin muscle layer
Distensible: high volume
Contains 70% of blood
valves
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Pericytes
Cells that wrap around arterioles and venules and can contract to control how much blood volume gets through
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Function of endothelium
Releases nitric oxide
Releases constrictors: endothelin, throboxane
Releases dilators: prostacyclin
Influences proliferative state of sooth muscle cells
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Dysfunctional endothelial cells
can release free radicals which oxidise LDL (pro-atherosclerosis)
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mean arterial pressure
MAP is the average pressure pushing blood around the system
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partial pressure oxygen and carbon dioxide in a healthy person
oxygen: 100+- 2mm Hg
co2: 40+- 2mm Hg
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Assumptions of the poiseuille equation
flow is laminar
flow is non-pulsatile
flow is through a uniform and straight pipe
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total peripheral resistance to flow
the sum ofresistances for the entire vascular tree
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Mechanisms encouraging venous return
Respiratory pump
skeletal muscle pump
sympathetic nerves
ventricular filling
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describe the respiratory pump
movement of diaphragm causes fluctations in intra-thoracic and intra-abdominal pressures
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describe the skeletal muscle pump
muscle contraction squeezes veins
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describe sympathetic nerves in venous return
norepinephrine constricts veins, therefore increased venous return to the heart
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describe ventricular filling in venous return
expansion of ventricles during filling creates diastolic suction
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effects of nitrates on angina
venodilation
- lowers central venous pressure
- lowers pre-load/LVEDP
- lowers CO
- Less caridac work/ O2 consumption
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Describe baroreceptors
Sensory nerve endings in the carotid sinus and aortic arch
pressure changes in response to stretching/standing up
reduces rapid fluctations in BP
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Things that effect baroreceptors
Ageing, hypotension and atherosclerosis all reduces baroreceptor receptor sensitivity
dysfunction can result in orthostatic hypotension
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Cardiovascular control centre
- Afferent nerves from barorecpetors terminate in the NTS of the medulla
- Efferent nerves innervate the sympathetic nervous system via the bulbar circulatory centres
Parasympathetic nervous system via the vagal nucleus
- NTS also recieves input from hypothalamus
-- This can amplify or diminish the baroreceptor response via adregenic receptors
81
Clonidine
Selective alpha-2 adrenoreceptor agonist
Activates presynaptic receptors in brain vasomotor centre to lower sympathetic output.
in NTS, fools brain into thinking catelcholamine levels are higher
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alpha-Methyldopa
sometimes used in pre-eclampsia due to lack of teratogenic effects
converted to alpha-methyl norepinephrine in the brain where it acts as a central alpha2 agonist
83
Describe rapid ejection
SL valves open, AV valves closed
Max outflow velocity occurs
Atria continue to fill but the pressure dips due to atrial diastole
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Describe reduced ejection
SL valves open, AV valves closed
T wave repolarisation
LV muscle starts to relax as the ejection rate decreases
Atria pressure rises due to continuous venous return
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describe isovolumetric relaxation
All valves closed
LVP decreases rapidly
S2 short sharp sound
86
Describe rapid filling
AV open, SL closed
LVP decreases despite filling due to continued relaxation: creates diastolic suction
Rapid passive filling
Atrial pressure decreases rapidly
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Describe reduced filling
Av open, SL closed
Passive filling almost complete
decreases pressur egradient = decreased filling
Prolonged phase at rest
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Stroke volume equation
SV = End Diastolic Volume - End Systolic Volume
(amount of blood ejected with each beat, note there is always some residula volume)
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Cardiac output equation
CO = Stroke Volume x Heart Rate
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cardiac index equation
Cardiac index = Cardiac Output / Body Surface Area
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Ejection Fraction equation
Stroke Volume / End Diastolic Volume x100
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Describe contraction by electrical conduction
Impulses generated by SAN
Spread over atria and ventricles by AVN
AVN slows conduction velocity to create delay
Signal propagated by bundle of His and Purkinje fibres
Spreads between myoctes via GAP junctions at ICDs
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SAN Action potential in sympathetic stimulation
Increase in HR by an increased Ca2+ ion influx to each threshold quicker
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SAN action potential in parasympathetic stimulation
increase in K+ ion permeability taking longer to reach threshold = lower HR
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Purkinje action potential
relatively prolonged
- Fast depolarisation due to Na+ current
- Plateau phase due to slow inactivation of L-type ca2+ channels
repolarisation by K+ influences duration too
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Describe an electrocardiogram
detects phasic change in potential difference between electrodes on surface of heart and limbs
The body acts as volume conductor
Recorded on paper or computer
useful for diagnosis of arrythmias, myocardial infarction, cardiomyopathy
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P wave
Atrial depolarisation
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QRS complex
Ventricular depolarisation
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t wave
ventricular repolarisation
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P-R interval
Delay through AV node
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S-T interval
Plateau phase of Action potential
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What is suggested by Sinus Rhythm
Normal healthy heart
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What is suggested by Sinus Brachycardia
Slow HR (< 60 bpm)
Normal in trained athletes
Many causes; sick sinus syndrome, electrolytes, myocarditis, beta-blockers
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What is suggested by Atrial fibrillation
Chaotic atrial rhythm (eg, >350bpm)
irregular ventricular rate
caused by re-entrant conduction pathways and common in elderly
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What is suggested by ventricular fibrillation
Chaotic ventricular rhythm incompatible with life
requires immediate resucitation
frequently occurs during MI
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Describe bundle branch block
Block in one branch of the bundle of his
Part of the ventricle is not innervated and i stimulated by unaffected myocardium
conduction is slowe = wide QRS
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Describe second degree heart block
Problem with AVN conduction
Only some impulses are conducted leading to irregular ventricular rhythm
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Describe ventricular tachycardia
A run of etopic beats (100bpm) originating in the ventricle
'Sustained' if lasting >30s and can lead to fibrillation and death
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describe STEMI
ST elevation is indicative MI
Reflects injured cells shifting baseline of ECG upwards
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Describe excitation-contraction coupling in cardiomyocytes
- action potential causes membrane depolarisation
- ca2+ enters via L-type calcium channels
- Ca2+ induced calcium release from sarcoplasmic reticulum amplifies signa
- Cross bridge formation at myofilaments = contraction
- removal of Ca2+ via sodium-calcium exchanger (NCX) and re-uptake into SR = relaxation
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What is inotropy
instrinsic contractility is determined by Ca2+ levels and myofilament sensitivity
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Describe regulation by adrenoceptors
exist in alpha and beta forms with subtypes of each
- Mainly Beta1 in heart
They bind norepinephrine released by sympathetic nerves and circulating adrenaline
Increases intracellular Ca2+
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Define chronotropy
heart rate
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define dromotropy
conduction speed
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define lusitropy
relaxation
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examples of adrenoceptors
agonists such as dobutamine can support the heart in acute decompensated heart failure
beta-blockers such as bisoprolo are used in chronic heart failure to reduce workload
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What is the afterload
The load against which the heart has to work to eject blood
Determined by aortic pressure, aortic compliance, and total peripheral resistance (TPR)
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What is preload
Myocyte stretch prior to contraction
Markers = end-diastolic volume or pressure (EDV/EDP)
Increase in sarcomere length means more overlap between filaments allowing for more cross-bridge formation, increases force
Determined by venous return, LV compliance and function
INOTROPY NOT ALTERED
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Describe the Frank-starling law
The heart contracts more forcefully during systole when it is filled to a greater extent during diastole
Failing hearts have impaired F-S response due to ventricular dilation resulting in too much stretch and less filament overlap.
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Describe quiet breathing
Inspiration: ACTIVE
- Diaphragm contracts downwards pushing abdominal contents outwards
- External intercostals pull ribs outwards and upwards
Expiration: PASSIVE
- Elastic recoil
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Describe strenuous breathing
Inspiration: ACTIVE
- greater contraction of diaphragm and external intercostals
- Inspiratory accessory muscle active ( sternocleidomastoid, ale nasi, genioglossus)
Expiration: ACTIVE
- Abdominal muscles (rectus abdominus, internal oblique, external oblique and transverse abdominus)
- Internal intercostal muscles oppose external intercostals by pushing ribs down and inwards
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Epithelium of upper airways to bronchioles
pseudo-stratified ciliated columnar
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Function of upper airways
Humidify (saturate with water)
Warm (to body temp)
Filter
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Describe the cough reflex (aspects, not the process)
* Rids airway of offending material
* rapidly adapting pulmonary stretch receptors (RARs) are found in epithelium of resp track
* RARs activated by dust, smoke, ammonia, oedema etc
* RARS afferents of vagus nerve
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describe the rpcoess of the cough reflex in steps
1. Stimulation of RARs by irritant
2. Affterent information sent via vagus nerve to brain
3. Brain sends information to diaphragm; external intercostals to induce strong contraction
4. air rushes into lungs
5. Abdominal muscles contrcat to induce expiration
6. glottis opens to forcefully release air and irritants
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what are the Conducting airways
Bronchi containing cartilage and non-respiratory bronchioles
Do not participate in gas exchange
form anatomic dead space
150ml in volume
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what are the respiratory airways
bronchioles with alveoli where gas exchange occurs (from terminal bronchioled to alveoli)
region is ~5mm long
~2500ml volume
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what is a respiratory unit
Gas exchanging unit
basic physiological unit of the lung consisting of respiratory bronchioles, alveolar ducts and alveoli
129
Describe the alveoli
Polygonal in shape, ~250um in diamteter
composed of type 1 and 2 epithelium.
1: occupy 97% pf surface are. Primary site of gas exhange
2: Septal cells. occupy 3% of surface area. produce pulmonary surfactant (reduced surface tension)
Large surface area, very thin walls and good diffusion characteristics
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2 blood supply to the lungs
Pulmonary circulation: brings deoxygenated blood from heart to the lung and oxygenated blood from lung to the heart then body
bronchial circulation: brings oxygenated blood to lung parenchyma
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distance between alveoli and red blood cell
1-2um
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differences between O2 and CO2 concentration gradients
Similar volumes of CO2 and O2 move each minute but the pressure gradient for O2 is much larger as CO2 is more diffusable
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describe arteries
high pressure
thick muscle layer
highly elastic
contains 17% of blood
dampens pulsatile flow
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describe veins
low pressure
thin muscle layer
distensible: high volume
contains 70% of blood
valves prevent backflow
135
Descibe endothelial cells
Continuous layer lining ALL vessles and the inside of heart chambers
Regulate contraction and relaxation of underlying smooth muscle cells
Prevent platelt aggregation and blood clot formation
Premeability barrier for nutrients / fluid between plasma and interstitial fluid.
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Nitric oxide function
Signal that keeps smooth muscle relaxed and so prevents platelt aggregation
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What do endothelial cells release
Constrictors: Endothelin, thromboxane & dilators: prostacyclin
When dysfunctional they can release free radicals which oxidise LDL (pro-atherosclerosis)
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Describe vascular smooth muscle cells
Present in all vessels except really small capillaries
Exhibit intrinsic contractile tone
Determine vessel radius by contracting and relaxing when stimulated by nerves, hormones, local signalling molecules
Secrete and extracellular matrix which gives the vessels their elastic properties
can proliferate in some diseases
139
What is MAP
mean arterial pressure is the avergae pressure pushing blood around the system
MAP = Diastolic BP + 1/3 pulse pressure (PP)
MAP = Co x TPR
140
Describe blood pressure control in regards to sympathetic innerveation
1. release of norepinephrine from post-ganglionic nerve varicosities
2. Activate alpha1 adrenoceptors on smooth muscle cells to cause constriction and increase in TPR
3. Norepinephrine taken up from synapse by alpha 2 adrenoceptors in pre-synaptic neuron (FEEDBACK LOOP)
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What is hyperaemia
increased blood flow
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What is active hyperaemia
Changes in gases and metabolites can dilate arterioles
- hypoxia (low O2) relaxes vascular SMCs
- High CO2 causes vasodilation via NO release
- Increases metabolic demand: ATP -> adenosine, whihc acts on alpha2 receptors to relax SMCs
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What is reactive Hyperaemia
Blocking blood flow temporarily induces vasorelaxtion (can be used to test vascular function in humas)
144
Describe capillaries
contain ~5% of total blood volume
network consists of ~25000 miles
echnage of nutrients/waste
one cell thick
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Factors influencing transport of water across capillaries
1. the blood in the capillaries exerts a pressure on the capillary wall (hydrostatic pressure)
2. This tends to favour movement of water out of the capillary (filtration)
3. The plasma has an intrinsic osmotic pressure due to plasma proteins (colloid pressure)
4. This tends to favour movement of water into the capillary
5. The sum of these 2 pressure determines the net water flow across the capillary wall
146
Describe how pulmonary capillaries are different to other types
Pulmonary hydrostatic pressures are lower than in systemic capillaries (~8 mmHg)
^ Due to larger diameter capillaries within a low resistance parallel capillary network
Osmotic pressure is also lower, since more permeable to proteins
Net effectslightly favours filtration
147
describe congestive heart failure
Impaired LV output results in elevated EDP. Pressure 'backs-up' into pulmonary circulation to increase hydrostatic pressure and cause fluid accumulation in the lungs (pulmonary oedema) resulting in breathlessness
148
describe right-sided heart failure
greatly increases venous pressure observed as jugular distension and increased capillary hydrostatic pressure in peripheral tissues, particularly the extremities.
149
Where are the main arterial baroreceptors found in the body
Carotid sinus and aortic arch
150
Describe the carina (location and function)
Found where the trachea splits into two bronchi
Sensitive to irritants that initiate a cough
151
How do you calculate mean arterial pressure
MAP = DP + (SP - DP)/3
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Epithelial lining within the trachea
Ciliated pseudostratified columnar epithelium
153
How do alveoli remain open and not collapse in on themselves
Presence of surfactant
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