B. Capillaries * microscopic blood vessels
{"Image DocumentName": "B. Capillaries   microscopic blood vessels", "Image ImageDescription": "join arterioles to venules.   site of gas/nutrient/waste exchanges. Capillaries form networks in the body. Not all capillary beds are open all the time - you don\u2019t have enough blood to fill them all. Precapillary sphincters close capillary beds when they do not need to be open. For example, after you have eaten, capillary beds servicing the skin & skeletal muscles are closed down, while those servicing the stomach & intestines are opened.", "Image XResolution": "37", "Image YResolution": "37", "Image ResolutionUnit": "Pixels/Centimeter", "Image Software": "SlidePlayer", "Image YCbCrPositioning": "Centered"}