Specialization in Individual Circulation Flashcards
(39 cards)
the five individual circulations.
1) coronary circulation
2) skeletal muscle circulation
3) cutaneous circulation
4) cerebral circulation
5) pulmonary circulation
coronary circulation
right & left coronary arteries, supply blood to the heart. Coronary sinus and thebesian veins return blood to the RA. Coronary is the shortest circulation in the body
skeletal muscle circulation
important role of metabolic hyperemia (coronary circulation too). During exercise, muscle circulation increases O2 & glucose delivery. Muscle mass ~ 40% of the body mass
cutaneous circulation
Skin circulation for temp regulation blood flow can change over 100 x. Skin surface area ~1.8 m2 & 2-3 kg. Epidermis is avascular, dermis is well vascularized. Skin has low metabolic rate.
cerebral circulation
Human brain ~1.5 kg & receives 14% of resting cardiac output, 20% of resting O2 consumption.
pulmonary circulation
Metabolic needs of alveoli are over supplied by pulmonary blood flow. Pulmonary circulation is different from systemic
Ways pulmonary circulation differs from systemic (5)
1) Pressures are low and flows high due to low pulmonary vascular resistance.
2) Autoregulation is absent and basal tone is low
3) Sympathetic vasomotor nerves have no major role
4) metabolic vasodilation has no role
5) pulmonary hypertension causes failure of the RV wall
Special tasks of coronary circulation
deliver O2 at a high rate to match basal myocardial demand. During exercise, it must increase to match cardiac work.
Special tasks of skeletal circulation
During exercise, circulation must increase O2 and glucose delivery. Vascular resistance has a major effect on total vascular resistance; helps regulate arterial blood pressure.
Special tasks of cutaneous circulation
1) regulate core temperature
2) water & heat are delivered to skin by bloodstream
3) defense against environment
4) emotional-related changes skin color
Special tasks of cerebral circulation
1) grey matter has high O2 demand, loss of consciousness after a few seconds of ischemia; irreversible neural damage within 4 min
2) increase O2 demand in response to regional demand
3) tightly regulated neuronal environment
Special tasks of pulmonary circulation
1) gas exchange. Equilibrate w/ gas phase, perfuse alveolus
2) enzymatic modification of circulating peptides such as angiotensin I and bradykinin
coronary circulation adaptation
Structural: 1) myocardial density is very high. 2) exercise training increases coronary artery width
Functional: 1) blood flow per gram is 10 x the whole body average. 2) extra O2 required supplied by increased coronary blood flow rate. 3) autoregulation 4) sympathetic vasoconstriction fibers innervate myocardial arteries. 5) adrenaline levels can increase. 6) ischemia elicits vasodilation & ATP use
skeletal circulation adaptation
Structural: 1) postural muscle - slow oxidative. 2) phasic muscle - fast glycolytic 3) endurance training stimulates capillary angiogenesis 4) arterial vessels adapts to max blood flow of 400 ml/mim/100 g of muscle
Functional: 1) vascular tone high @ rest. 2) vascular resistance regulate BP 3) sympathetic activity regulated by baroreceptors. 4) muscle pump boost local pressure gradient
cutaneous circulation adaptation
1) sympathetic nerves, not metabolic are dominant.
2) stress causes vasoconstriction, embarrassment vasodilation.
3) cold causes veno & vasoconstriction. Heat causes dilation.
4) core temp receptrors in hypothalamus control vasoconstrictor fibers to acral skin.
cerebral circulation adaptation
1) grey matter has high basal flow dur to low arteriolar resistance.
2) blood brain barrier creates regulated neuronal environment.
3) perfusion pressure is safeguarded by brainstem regulation
4) autoregulation maintains perfusion during hypotension
pulmonary circulation adaptation
Structural: 1) pulmonary bed has high capillary density & short diffusion distance. 2) pulmonary arteries are shorter and thinner walled than systemic counterparts, less hydraulic resistance.
Functional: 1) transit time in pulmonary capillaries is short, 0.3-1.0 sec 2) local hypoxia causes vasoconstriction to preserve uniform alveolar ventilation/perfusion rate. 3) flow increases in proportion to pressure; no autoregulation. 4) low capillary pressure reduces alveolar membrane stress & fluid filtration. 5) endothelium enzymes modify/degrade circulating vasoactive peptides.
Problems with coronary circulation
1) systole obstructs coronary blood flow. 80% happens during diastole
2) coronary arteries are common site for atheroma
3) thrombosis causes MI
4) chronic coronary stenosis causes angina
Problems with skeletal circulation
1) blood flow is mechanically impaired, especially during isometric contraction
2) increases capillary filtration causes swollen “pumped” muscle in severe exercise
3) ischemia due to leg artery causes intermittent claudication, ulcers, and gangrene.
Problems with cutaneous circulation
1) prolonged compression leads to pressure ulcers
2) cutaneous vasodilation contributes to fainting & heat exhaustion
3) ambient cold triggers Raynauds disease
4) strenuous exercise can lead to heat exhaustion
Problems with cerebral circulation
1) disorganization of the endothelial junction protein causes the blood-brain barrier to break down.
2) standing up can cause transient cerebral hypoperfusion & dizziness
3) vasodilation contribute to migraine headaches
4) carotid/cerebral artery atheroma causes strokes
problems with pulmonary circulation
1) apices not well perfused in orthostatis
2) chronic hypoxia causes chronic vasoconstriction and hypotension -> Right heart failure
3) embolism can cause sudden fall in cardiac output, collapse, or death
4) alveolar/endothelial membrane is ultra thin 0.3 nanometer, hypertension can cause membrane leakage
Technique for assessing coronary circulation
ECG, blood enzymes, ECHO, nuclear imaging, coronary angiography, CS thermal dilution method, isotope imaging
Technique for assessing skeletal circulation
1) venous occlusion plethysmography - limb blood flow
2) doppler velocity meter & ABPI - arterial vessel patency
3) kety’s isotope clearance method - capillary perfusion
