540 



ORGAN SYSTEMS OF MAN 



trouble with those individuals who tend to 

 break with established convention and to 

 follow basic instinctive urges. This applies 

 to sex urges as well as others. It is impor- 

 tant that we recognize these basic urges as 

 normal and regulate our social order ac- 

 cordingly. This attitude has not always 

 been maintained in the past, but as knowl- 

 edge grows concerning human behavior we 

 shall eventually reach a better understand- 

 ing of what curbs can be placed on basic 

 instincts that will benefit society and thus 

 make for a more successful civilization. 



Male 



The sperm-producing glands are the 

 testes, which are very similar in their an- 

 atomy to the same organ in other mammals. 

 Sperms are produced by rapidly dividing 

 cells located in the walls of the long, tiny, 

 coiled tubules which, taken together, make 

 up most of the gland itself (Fig. 21-6). The 

 paired testes lie in a pendant sac, the scro- 

 tum, which is located in the pubic region. 

 Sperm cells make their way out of the 

 testes into the epididymis, a long convo- 

 luted tubule, where they mature and are 

 stored for a time. They then pass into the 

 vas deferens, a thickened sperm duct that 

 passes anteriorly through the inguinal 

 canal, finally entering the urethra and 

 thence through the penis to the outside. 

 Near the region where the two vasa def eren- 

 tia enter the urethra each receives secre- 

 tions from the glandular seminal vesicles. 

 Also at this junction the prostate gland sur- 

 rounds the urethra and pours its secretions 

 into it. The secretions from both the prostate 

 » gland and the seminal vesicles provide a 

 transport medium for the sperms. 



The penis is composed of a special tissue 

 with large capillaries called erectile tissue 

 which, when gorged with blood, causes the 

 organ to become much enlarged and turgid. 

 In such condition it becomes a satisfactory 

 organ for transferring sperms to the vagina 

 of the female. Erection is accomplished 



when, under sexual excitement, the small 

 arteries leading to the penis relax, allow- 

 ing blood to fill the large capillaries; at the 

 same time the vein^ constrict where they 

 leave the organ, thus trapping blood within 

 it. The organ becomes flaccid by a reversing 

 of the process. The penis ends in a cap-like 

 structure, the glans, which is partially cov- 

 ered by loose skin, the prepuce. 



Because of the anatomical arrangement 

 of the male generative organs, certain dif- 

 ficulties may be experienced, especially by 

 older men. For example, if the prostate be- 

 comes enlarged, which it not infrequently 

 does, elimination of urine becomes dif- 

 ficult because the urethra is squeezed shut. 

 Another difficulty arises from the fact that 

 when the testes descend through the in- 

 guinal canal into the scrotum some weeks 

 before birth, a weakened area is left at the 

 point where the spermatic cord perforates 

 the abdominal wall. If, at some later time, 

 sufficient pressure is brought to bear on this 

 area, a small segment of the gut may be 

 forced into this canal resulting in an in- 

 guinal hernia. This sometimes occurs dur- 

 ing birth when the child is apt to be 

 squeezed unduly while passing through the 

 small birth canal. If further constriction 

 occurs, the circulation to tlie gut may be- 

 come so impaired as to kill the region, thus 

 resulting in gangrene which can be very 

 serious. 



Female 



The egg-producing ovaries lie deep in 

 the lower body cavity where they function 

 much as they do in lower vertebrates ( Fig. 

 21-7). Their function is to produce suffi- 

 cient eggs to maintain the race, and since 

 the chances for fertilization in mammals 

 are very good only a comparatively small 

 number are actually generated. The cells 

 destined to become eggs lie in the periph- 

 ery of the ovary and as they mature migrate 

 into the deeper portions (Fig. 21-8). Sev- 

 eral layers of cells form around each egg at 



