BIOL 142 Chapter Notes - Chapter 13-14: Collagen, Chyle, Gastrointestinal Tract
9 Jul 2018
School
Department
Course
Professor
Document Summary
Capillaries are miscroscopic and are the smallest blood vessels. In some cases. one endothelial cell forms the entire circumference of the capillary wall. Their exceedingly thin walls consist of just a thin tunica intima. Their diameters are so small that only since. At strategic location along the outer surface of some capillaries are spider-shaped pericytes, contractile stem cells that can generate new vessels or scar tissue, stabilize capillary wall and help control capillary permeability. Average capillary length is 1 mm and average lumen diameter is 8 - 10 um, just large enough for red blood cells to slip through in single file. Most tissues have a rich capillary supply, but there are exceptions. Tendons and ligaments are poorly vascularized (and so heal poorly). Cartilage and epithelia lack capillaries, but receive nutrients from blood vessels in nearby connective tissues, and the avascular cornea and lens of the eye receive nutrients from the aqueous humor.
