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Cardio – Vascular System
Endothelium of a capillary
This EMG demonstrates the endothelium lining the lumen of a capillary (in muscle).
Note the relatively large nucleus (N) in the cytoplasm of the endothelial cell (A) and part of the cytoplasm of another (B).
Note too, the pinocytotic vesicles (arrows) which in this case serve to transport fluid across the cytoplasm between the blood in the capillary and the muscle cell.
Fawcett, “The Cell”, p403
This diagram illustrates the structure of a fenestrated capillary. Note the pores (P) with diaphragms which occur at regular intervals in the attenuated cytoplasm of the endothelium.
RBC = red blood cell in lumen (L)N = nucleus of endothelial cellPV = pinocytotic vessiclesJ = junctional complexBL = basal lamina of endothelium
Example of a small arteriole
Note the three distinct coats in the wall of this arteriole (RBC – red blood corpuscles in lumen):• the tunica intima, made up of one layer of endothelial cells only; note too, the nuclei (N) and the basal lamina (BL) of the endothelium• the tunica media, made up of one layer of smooth muscle cells (SM)• the tunica adventitia, the outermost coat, made up of collagen (Co) and associated fibroblasts (F and arrow on the left).
Matthews and Martin, Atlas, 1971