1 66a 



HANDBOOK OF PHYSIOLOGY 



CIRCULATION II 



shaft of the bone forms one nutritional unit, and the 

 joint cavity and adjoining epiphysis form another. 

 For this reason, Harris (55) uses the term circulus 

 vasculosis arliculi et epiphyseos to emphasize the nutri- 

 tional interdependence of the joint and the epiphysis. 



The venous drainage has received little attention. 

 According to Testut (104), Sappey described the 

 veins as characterized by frequent anastomoses, 

 tortuosities, and varicosities. Testut remarks on their 

 voluminous nature. Occasional valves are seen in the 

 large veins, even in the more superficial parts of the 

 synovial membranes. 



The delicate nature of the synovial membrane and 

 its blood supply is indicated by the fact that small 

 extravasations of blood into the joint cavity are often 

 found in animals, and some extravasation follows 

 such a simple procedure as puncture of the joint (35). 



The Nerve Supply 



Chief among the features of the synovial membrane 

 is its sensitivity to pain. Localization is often not 

 highly accurate. To what degree the synovial mem- 

 brane responds to other sensations, such as tension or 

 pressure, is uncertain. Medullated and nonmedullated 

 nerves entering the joint with the blood vessels form a 

 plexus in the synovial membrane. The nonmedullated 

 fibers in large part innervate the blood vessels and are 

 probably of sympathetic origin. The effects of sympa- 

 thectomy on the vascular supply of joints remains 

 obscure, and in view of the paradoxical effects re- 

 corded by Engel (44) they need investigation. The 

 synovial membrane shows an abundance of free nerve 

 endings presumably subserving pain; end organs 

 possibly concerned with proprioceptive impulses are 

 variously described as Ruflini, Golgi, Mazzoni, 

 looped or knotted types. Pacinian corpuscles are not a 

 characteristic feature of the synovial membrane. 

 Gardner (49) failed to find them, and Davies (34) 

 confirms this. 



Blond Flow Through Joints 



Attempts have been made to determine the blood 

 flow through joints by measuring the intra-articular 

 temperature (61), by the application of the plethysmo- 

 graph to a knee segment (9), by using a bubble flow- 

 meter (25), and by means of an electromagnetic 

 flowmeter (26, 27). 



In adult anesthetized dogs weighing 9.5 to 31 k", 

 the blood flow through the knee joint amounts to 1.5 

 to 7.0 ml per min (26). The temperature of the joint 

 must be markedly raised to obtain a measurable in- 



crease in flow, changes of 10 C having little effect. 

 Even a high external temperature of 60 to 65 C in- 

 creases the blood flow only 1 5 to 57 per cent. Rapid 

 cooling of the joint with ice packs causes the flow to 

 decrease and remain fairly constant at half that of the 

 control. However, sometimes the flow falls, rises, and 

 then falls again; this is a type of behavior also de- 

 scribed for skin vessels exposed to low temperatures 

 (84). Removal of the ice packs is followed by a slow 

 return of blood flow to the control level, partly owing 

 to the delay in returning to the normal temperature. 

 Nevertheless, a delay in the return of blood flow also 

 occurs when the joint is quickly restored to the control 

 temperature. 



According to Horvath & Hollander (61), joint 

 blood vessels dilate in response to cold and constrict 

 when exposed to heat. This finding is not supported 

 by the work of Hunter & Whillams (67) who used the 

 same technique. The latter found that joint tempera- 

 ture fell when their subject was exposed to cold, and 

 this they attributed to a reflex superficial vasodilata- 

 tion resulting in a short period of excessive heat loss. 

 On the other hand, Cobbold & Lewis (26) believe 

 the decrease in intra-articular temperature on expo- 

 sure to cold is the result of the constriction of joint 

 vessels. In their plethysmographic study of blood flow 

 through the knee segment, Bonney*/ a/. (9) found that 

 cooling the area resulted in a decrease in blood flow, 

 and heating produced the reverse effect. Since they 

 found a similar decrease in flow when the circulation 

 to the skin of the segment was suppressed by Adrenalin 

 iontophoresis, and further observed that after this 

 procedure cooling no longer decreased the blood flow, 

 Bonney et al. suggest that a different reaction to cool- 

 ing may occur in articular than does in superficial 

 vessels. The direct measurement of flow by Cobbold 

 & Lewis (26) does not support this view. These in- 

 vestigators believe that the results reported by Bonney 

 et al. are complicated by the presence of other tissue 

 such as muscle. 



Nervous Control of Joint Blood J'essels 



The innervation of joints has been fully reviewed 

 by Gardner (50). The blood vessels of the knee joint 

 receive vasoconstrictor fibers by way of the articular 

 nerves. Section of these increases blood flow some 

 50 per cent above the resting level (27). Stimulation 

 of the peripheral cut end of this nerve produces vaso- 

 constriction and a decreased blood flow. When the 

 carotid arteries were occluded below the carotid sinus, 

 the usual increase in systemic pressure was seen, but 



