444 ANATOMY FOR NURSES [Chap. XXI 



fully matured the wall of the ovary and the wall of the follicle burst 

 at the same point, and the contents of the follicle — the fluid, 

 the ovum, and the surrounding cells — escape. This process of 

 development, maturation, and rupture of a follicle is kncnvn as 

 ovulation, and continues at regular intervals from puberty to the 

 menopause. 



The corpus luteum. — After the rupture of a follicle, and the 

 escape of the ovum, the walls collapse and the cavity becomes 

 filled with blood which forms a clot. Later this clot becomes 

 surrounded by cells containing a yellow pigment, which gives the 

 follicle a yellow color, and hence it is known as the corpus luteum. 

 The size and duration of the corpus luteum is dependent on whether 

 fertilization occurs or not. If fertilization does not occur the cor- 

 pus luteum increases in size for two or three weeks and then is ab- 

 sorbed. If fertilization does occur and the woman becomes preg- 

 nant, the corpus luteum increases in size during the first few 

 months, and does not show retrogressive changes until about the 

 sixth month. The function of the corpus luteum is unknown. 

 Some physiologists regard it as a protective mechanism by means of 

 which the cavity resulting from the rupture of the follicle is filled 

 with a tissue which can be easily absorbed. Others attribute to 

 the corpus luteum the formation of the internal secretion of the 

 ovaries. This will be discussed later. 



Fallopian tubes. — The Fallopian tubes or oviducts are two in 

 number, one on each side, and pass from the upper angles of the 

 uterus in a somewhat tortuous course between the folds and along 

 the upper margin of the l)road ligament, towards the sides of the pel- 

 vis. They are about four inches (100 mm.) long, and at the point 

 of attachment to the uterus are very narrow, but gradually increase 

 in size so that the distal end is larger. The margin of the distal 

 end is surrounded by a number of fringe-like processes called fim- 

 briae. . One of these fimbrise is attached to the ovary. The uterine 

 opening of the tube is minute, and will only admit a fine bristle ; 

 the abdominal opening is comparatively much larger. 



The uterine tube consists of three coats : — 



(1) Serous. — The external, or serous, coat is derived from the 

 peritoneum. 



(2) Muscular. — The middle, or muscular, coat has two layers : 

 one a layer of longitudinal fibres and the other of circular fibres. 



