Lecture 14 Flashcards
Name the 2 circulations of the lungs
Bronchial - systemic circulation
- supplies metabolic needs
Pulmonary - alveoli
- oxygenates blood
Exercise CO
20-25 L/min
Adaptations to lower resistance
Short, wide vessels - lower TPR
Lots of parallel capillaries - 1/R + 1/R
Less smooth muscle in arterioles - little contraction
Adaptations to promote gas exchange
High density of capillaries - increased surface area
Thin tissue layer - short diffusion pathway
Optimal ventilation perfusion ration
0.8
Pulmonary response to hypoxia in the lungs
Vasoconstriction of pulmonary vessels to decrease perfusion ventilation equals perfusion
Blood diverted to well ventilated alveoli to optimise gas exchange
Effect of chronic hypoxia pulmonary vasoconstriction
Chronic increase in vascular resistance Pulmonary hypertension Increased afterload in RV RV hypertrophy Right sided heart failure
At altitude
Lung disease
Which pressures influence the pulmonary circulation
Hydrostatic
Oncotic
Pulmonary oedema
Mitral valve stenosis
LV failure - increased preload
Hydrostatic pressure in the pulmonary vein increases Greater than oncotic pressure Fluid moves out Oedema in base of lungs - orthostasis Oedema in all lung - lying down
Treatment: diuretics
Adaptations of cerebral circulation
High oxygen extraction rate
High basal flow
High capillary density - reduced diffusion distance
Anastomoses
Myotonic autoregulation - maintains perfusion during hypotension
- low BP = vasodilation
Metabolic regulation - hypercapnia (CO2) - vasodilation (exercise)
Hyperventilation
Hypocapnea (dispel too much CO2) - Cerebral vasoconstriction
Causes syncope and dizziness
Metabolites that cause vasodilation
Increased CO2
Adenosine
Increased Potassium
Decreased oxygen (except lungs)
Adaptations of coronary circulation
Short fibre diameter Lots of capillaries - short diffusion pathway All capillaries are opened Continuously perfumed Produce nitric oxide - vasodilator High basal flow
Functional end arteries
Coronary arteries have few arterio-arterial anastomoses
Prone to atheromas
Skeletal muscle circulation adaptations
High vascular motor tone - allows fro vasodilation to increase flow
Capillary density dependent on type
Half of capillaries opened - other half for recruitment
Adaptations of cutaneous circulation
Arteriovenous anastomoses
Arterial to venous shunts
Bradykinin - non apical skin vasodilation
Causes of chest pain
Musculoskeletal and skin Lungs and pleural sac Heart and pericardial sac Oesophageal Aorta
Musculoskeletal and skin
Well localised
Painful on palpating
Sharp
Examples:
rib fracture
shingles
Costochondritis
Pleural sac and lungs
Localised
Painful on inhalation, coughing, positional movements
Sharp pain
Examples:
Pneumonia
Pulmonary embolism
Cardiac and pericardial sac
Dull crushing pain
Radiating to jawline, arms and shoulders
Central
Examples:
MI
Pericarditis - sharp central pain non radiating
Ischaemia
Aorta
Sharp tearing pain
Radiates to back
Example
Aortic dissection
Oesophageal
burning sensation
Examples:
Oesophageal reflux
Peptic ulcer disease
Differences between visceral and somatic pain
Visceral is: Dull and central pain Worsened with exertion Involves the heart Poorly localised
Somatic: Localise Sharp pain Involves pleural and pericardial sac Worse on inspiration, positional change and coughing
Pericarditis
Sharp pain Localised Predisposition: Male and infection Worse on coughing, inspiration and positional movement Better when sitting up Widespread ST elevation saddle
Pericardial rub may be heard
Atherosclerosis
Lipid Laden core with fibrous external cap
Partially occluded coronary arteries causing ischaemia
Stable angina
Pain on exertion
Relieved at rest
Dull tight pain
Central
No autonomic symptoms
Relieved with GTN spray (nitrates)
Unstable angina
Pain at rest and made worse on exertion
Lasts longer
ST depression
T wave inverted and flattened
Acute coronary artery syndrome
Atheromatous plaque rupture
Thrombus formed
Acute increased occlusion (not stable angina) of coronary arteries
E.g coronary dissection or spasm
How to distinguish between unstable angina and MI
Blood test for Troponin I
Present - MI
MI
Pain at rest
Worse on exertion
Autonomic symptoms:
- sweating
- nausea and vomiting
- tachycardia
Pathological Q wave
T wave inversion
ST elevation or depression
Regional wall motion abnormal
Loss of viable myocardium
Infarct
ST segment elevation
Hyperacute T wave
New left bundle branch block
