![]() Interlobar arteries, which enter the renal tissue at the border between the cortex and medulla.Segmental arteries (large end arteries).Anterior and posterior main branches of the renal artery.In summary, the arterial and venous circulation of the kidney can be presented as a sequential list of vessels: Inside the kidney, there is no anastomosis between these arteries, i.e each branch is an end-branch and the ischaemia of one segmental artery will create regional ischaemia in the territory of its distribution ( Bertram, 2000). Just before entering the parenchyma, the human renal arteries tend to divide into anterior and posterior main branches, which in turn divide into segmental arteries. Each is about 4-5 cm in length and 5-10 mm in diameter, with one usually a little bigger than the other. Renal vascular supplyĮach kidney is supplied by a renal artery, which is basically a big muscular artery and a main branch of the aorta. Just (2007) is also new and free, but realistically, no CICM primary exam candidate would ever need as much detail as that. Braam et al (2014) is new, good, free, but long. Stein (1990) is old, but short, good, and free. There is a lot of high-quality material in the peer-reviewed literature, and the CICM exam candidate is spoiled for choice, even if they decide not to pay for anything. Glomerula filtration rate is less affected (out of porportion to blood flow) because the efferent arterioles vasoconstrict more than the afferent in response to a sympathetic stimulus.shock) overrides autoregulation and markedly decreases renal blood flow Autoregulation typically maintains stable renal blood flow over a wide range of systemic sympathetic conditions.Sympathetic tone regulates the range of renal blood flow autoregulation.Sympathetic regulation of renal blood flow. ![]() The mechanism is mediated by ATP and adenosine secreted by macula densa cells, which cause afferent arterolar vasoconstriction.This is a negative feedback loop which decreases renal blood in response to increased sodium delivery to the tubule.This is a stereotyped vascular smooth muscle response, not unique to the kidney.Vasoconstriction in response to wall stretch.Other mechanisms involving angiotensin-II and NO (Myogenic response (50% of the total autoregulatory response).Renal blood flow remains constant over a MAP range of 75-160 mmHg.Renal oxygen extraction remains stable as renal blood flow changes, because renal metabolic rate depends on glomerular filtration rate and tubular sodium delivery.Total renal oxygen extraction is low (10-15%).Total renal blood is high for reasons of filtration rather than metabolism.Medullary blood flow must remain low to maintain the urea concentration gradient, to facilitate the concentration of urine.95% goes to the cortex, 5% goes to the medulla.Total blood flow: 20-25% of cardiac output, or 1000ml/min, or 400ml/100g/min.The resistance of the afferent and efferent arterioles, on either side of the high-pressure glomerular capillaries, is an important mechanism of control for glomerular filtration.A low pressure capillary network, the peritubular capillaries. ![]() A high pressure capillary network, being the glomerular capillaries.Renal arteries are end-arteries (there is no arterial anastomosis inside the kidney). ![]() Is it renal? Is it circulatory? Ultimately, the author had felt that, unless the discussion veers dangerously close to the topic of glomerular filtration or solute clearance, it would be relatively safe to fit this under the cardiovascular heading. Like with cerebral and hepatic metabolism, it was difficult to find a suitable position for this chapter within the revision structure.
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