248 ANATOMY AND PHYSIOLOGY 



The length of the male urethra is from seven to eight inches. 



The female urethra is about one and one-half inches long and 

 1/4 in wide, but is very distensible. It curves slightly downward 

 toward the external meatus. 



Clinical note. The catheter should pass a little upward after entering the 

 urethra (Fig. 165). 



A urethral caruncle is an exceedingly painful little tumor 

 projecting from the urethral mucous membrane. It is a collection 

 of sensitive blood-vessels and nerves. 



When empty the bladder lies entirely in the pelvis, but if it 

 contains more than eight ounces it begins to rise into the abdo- 

 men. It has been known to extend as high as the umbilicus. 



Surgical notes. Since the peritoneum covers the vertex and a portion of 

 the posterior surface only, the bladder may be entered in front through an 

 incision just above the symphysis pubis without wounding the peritoneum. 



Cystitis is inflammation of the bladder. 



PHYSIOLOGY OF THE KIDNEYS AND ACCESSORY 



ORGANS 



This consists in the removal of waste substances from the blood in the 

 form of urine and expelling it from the body. 



The process of excretion in the kidney is one of filtration and secretion. 

 The kidney has a large blood supply through the renal artery, which enters 

 at the hilum and divides at once into several branches. The capillaries from 

 these arteries are very numerous. They enter first the capsule of the Mal- 

 pighian body as afferent vessels and form a cluster or tuft there (the glomerulus] 

 from which the water and salts are filtered out and pass into the tubule. 

 They then leave the capsule as efferent vessels and twist themselves about the 

 convoluted tubules, whose epithelial cells select (secrete) the organic substances 

 urea, uric acid and others. These are washed down, by the watery solution 

 coming from the capsule, to the collecting tubes of the pyramids and there 

 discharged into the pelvis of the kidney, as urine; the amount of urine excreted 

 varies greatly, but in the adult, in health, averages 48 ounces or 3 pints daily; 

 it is directly affected by the quantity of fluid which the person drinks, the 

 amount of perspiration formed and in other ways. 



Children excrete more than adults in proportion to the body 

 size, averaging nearly one-half of the adult quantity at the age of 

 five years. This is probably due to the fact that their dietary 

 contains more fluid, also their metabolism or tissue change is 

 more rapidly carried on, creating more waste material proportion- 

 ately, to be eliminated. 



