I9I4 . HUMAN ANATOMY. 



escape of urine. A similar, but usually permanent closure of the wound — by mus- 

 cular contraction, or by a valvular action from the change in the relation of the coats 

 of the vesical wall after tension has been relieved — takes place when the bladder has 

 been tapped above the pubes (^suprapubic puyidure^. 



Cystitis, in so far as it has an anatomical bearing, should be studied with regard 

 to the possible sources of the essential infection and of the almost equally essential 

 predisposing condition of congestion. No explanation is required of the influence 

 of (a) frequent micturition, however caused ; {b) trauma ; {c) vesical distention ; 

 {d) acid urine ; (<?) calculi or tumors ; {/) cold and wet ; (g) prolonged sexual 

 excitement ; (h) cardiac weakness, in bringing about a congestion of the vesical 

 and vesico-prostatic plexuses. The sudden removal of pressure when an habitually 

 distended bladder is emptied may be followed by congestion so excessive as to cause 

 haematuria. 



Infection may occur by spreading from the urethra or prostate, by instrumenta- 

 tion, by descent from the kidneys, by extension from any pericystic focus of suppu- 

 ration, or by direct passage of the microbic cause from the rectum. The great 

 venous plexus at the base of the bladder, emptying into the valveless internal iliac 

 veins, is engorged whenever pressure is made upon the latter, as by fecal masses in the 

 sigmoid flexure or rectum. Constipation is thus both a predisposing and — through 

 the migration of microbes to the contiguous bladder — an exciting cause of cystitis. 



The mucosa of the bladder, supplied by the hypogastric plexus, is not very 

 sensitive normally, except in the region of the trigonum. There it is tightly con- 

 nected with the muscular layer, and the loose, elastic, submucous connective tissue 

 found in the remainder of the bladder is absent. The difterence is shown by the 

 smooth surface of the trigonum as contrasted with the rugae of the lax mucosa seen 

 o\'er the rest of the interior of the empty bladder. The laxity in the superior por- 

 tions of the bladder is determined by the necessity for great changes in its size. At 

 the trigonum a similar looseness of the mucosa would encourage its prolapse, and 

 might result in frequent obstruction of the ureteral and vesical outlets. This close 

 adhesion of mucous and muscular layers prevents free swelling when inflammation 

 occurs, and, in conjunction with the particularly generous vascular and nerve-supply 

 to the trigonum and neck of the bladder, explains the pain and sensitiveness of that 

 region in cystitis. In a marked case the whole bladder may become sensitive, so 

 that hypogastric pressure is painful. 



Frequent micturition, as a result of cystitis or of other conditions in which vesical 

 irritation is present, is due to stimulus of the sensory nerves supplied by the third 

 and fourth sacral nerves from the second, third, and fourth sacral segments of the 

 cord. The motor impulse reaches the bladder from the eleventh and twelfth dorsal 

 and first lumbar segments through the hypogastric and pelvie plexuses. 



The skin of the scrotum and of the penis and the urethral mucous membrane 

 are supplied with sensation from the same spinal segments as is the bladder, and 

 therefore the referred pains in vesical irritation or inflammation are often felt in those 

 regions in the distribution of the perineal branches of the pudic and inferior gluteal 

 nerves. As the inferior hemorrhoidal nerve — supplying the skin over the external 

 sphincter ani and about the anus — is often derived from the sacral plexus, itching or 

 tickling in that region or painful spasm of the anal sphincter may be caused by 

 vesical irritation. 



Other referred pains in vesical disease are to the lumbo-sacral region, through 

 the communication between the second, third, and fourth sacral nerves and the hypo- 

 gastric plexus ; to the kidney, by the junction in the spermatic plexus .of filaments 

 from the vesical and renal plexuses ; and to the lower limb, occasionally to the foot 

 (pododynia), through the sacral nerves which enter into the sacral. plexus and the 

 lumbo-sacral cord, giving off the great sciatic nerve, and also into the pelvic 

 plexuses. 



The important muscular element in the vesical, as in the ureteral, walls gives 

 the "colicky" character to the symptoms of irritation and, in the case of the in- 

 flamed bladder, causes the violent tenesmus accompanying the discharge of the last 

 drops of urine, when the muscles in the vicinity of the sensitive trigonum contract 

 spasmodically. 



