Pulse rate is easily felt when gently pressing the arteries in the wrist or neck region (Fig. 1).

assessing pulse rate
Fig. 1. Feeling the pulse at the radial artery. Source: Wikipedia

Arteries supply the thin vasculature in the capillary bed where the blood flow encounters a large increase in resistance due to the narrow vasculature and blood flow is reduced, albeit the pressure may still be relatively high. The capillary bed, in turn, feeds the venous system (Fig. 2), characterized by a low blood pressure and relatively slow and continuous blood flow. This steady, slow blood flow is apparent during blood sampling procedures from the veins in the arm, where I have never noticed any pulsatile flow by visual observation (anecdotal evidence, but quite representative I'm sure).

Fig. 2. Blood vessels. Source: Aruba trial.

Is there an observable/measurable pulse in the capillaries and veins, or is blood flow continuous in these vessels?

PS. This question was re-formulated based on a deleted question posted by @laggingreflex and credits go to OP.

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    $\begingroup$ I asked the original question but mine was probably a lot dumber :) as I was basically just asking whether blood flow was continuous in the arteries of the wrist itself (something I mistakenly imagined were the case), to which the answer would've been "duh no" because if it were you wouldn't be able to measure the pulse. Yours is a great question though, clearly much more than just an interpretation. +1 $\endgroup$ – laggingreflex Jul 6 '15 at 13:11
  • $\begingroup$ @laggingreflex - your question was not dumb and in fact pretty interesting! My knowledge on behavior of pressurized fluids is next to nil, so I'm curious to the answers. $\endgroup$ – AliceD Jul 6 '15 at 13:32
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    $\begingroup$ If it adds to the context, I was trying to learn how exactly does a sphygnomanometer help in measuring the blood pressure and I encountered this line on Korotkoff sounds page: "As the heart beats, these pulses are transmitted smoothly via laminar (non-turbulent) blood flow throughout the arteries, and no sound is produced." which kinda sounds like the pulsating flow of the blood from the heart becomes smooth and continuous in the arteries (unless I'm misunderstanding). Anyways I'm curious and looking forward to the answers as well. $\endgroup$ – laggingreflex Jul 6 '15 at 13:39
  • $\begingroup$ @AliceD can you include the original question in yours? And why wasn't the original question edited include this aspect? $\endgroup$ – bonCodigo Jul 7 '15 at 5:10
  • $\begingroup$ @bonCodigo - question was removed - edited my Q to explain $\endgroup$ – AliceD Jul 7 '15 at 5:31

In the capillary bed? Absolutely! In the venous return? Depends!

I had to build one of these for class. In short: you can tell how oxygenated the blood is by its color, but you have to correct for how much blood there is: The dilation of the arterioles and capillaries with the heartbeat increases the size of the area being measured, and changes all sorts of properties including conductance. There's a neat heartbeat monitoring method method that involves putting two electrodes on your arm, one at the wrist and one at the elbow, and measuring the increase in conductivity every time your heart beats and your arm swells.

Depending on heart rate and all sorts of other things, there's not usually a detectable heartbeat in the veins right outside the heart (see the CVP, which is pretty much flat). However, the jugular venous pressure is the pressure of the internal jugular vein that drains the head, and that has heartbeat oscillations (not one-to-one, there are "echoes" and other weirdnesses because it's almost connected to the heart. See here for more).

In sum: The capillary bed absolutely swells and contracts with each heartbeat, but in the veins blood usually just oozes along. There are a couple exceptions but mostly they're silent.

(The Korotkoff sounds you're talking about are a fluid dynamics thing. When the veins are regular-sized they're wide enough to permit laminar flow(where all the blood moves in a straight line), which is smooth but still pulsatile. Like these guys the blood flow starts and stops but is in sync with itself. When you compress them you increase the Reynolds number and you get turbulent flow, which you can hear because it's making noise.)

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  • $\begingroup$ "I had to build one of these for class" : Can you share how you build it or/and an accessible manual for it? $\endgroup$ – bonCodigo Jul 7 '15 at 6:45
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    $\begingroup$ A complete description would be too long for comments. As far as a manual you could try this but I don't advise you try this at home. It's not life-threatening per se but you'll probably need to solder things onto other things. $\endgroup$ – Resonating Jul 7 '15 at 14:55

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