534 



THE REPRODUCTIVE SYSTEM 



lowed by a process of regression and later of regeneration, by which the 

 uterine mucosa rapidly returns to its former condition. 



The first or hypertrophic stage involves the epithelium, whose cells are 

 elongated, and the tunica propria, in which many of the connective tissue 

 cells undergo multiplication and enlargement. Thus the mucous mem- 

 brane becomes greatly thickened; its glands, also, are increased in both 

 length and breadth, becoming at the same time even more tortuous than 

 before. The glandular hypertrophy involves both the uterine and the 

 cervical glands; the secretion of the latter is much increased. 







FIG. 468. FROM A. SECTION OF THE HUMAN UTERINE MUCOSA AT THE FIRST DAY 



OF MENSTRUATION. 



e, epithelium; d, disintegrating layer; g, gland; v, blood-vessel; m, muscular coat. 

 X 44. (After Minot.) 



At the same time, the blood-vessels become widely dilated, especially 

 those near the surface, and broad thin-walled sinuses are formed beneath 

 the epithelium. Finally these vessels rupture and hemorrhages occur into 

 the substance of the mucosa as well as into the cavity of the organ; des- 

 quamation and disintegration of the superficial portions of the mucosa 

 result. The menses which are thus formed contain blood, epithelium, con- 

 nective tissue cells, and many leukocytes, which wander out from the blood- 

 vessels of the mucosa in large numbers. The greatly thickened' and hemor- 

 rhagic mucosa is known as the decidua menstrualis. 



Regression and regeneration follow rapidly upon one another, the 

 mucosa gradually regaining its former condition. During this process fat 

 droplets appear in many of the connective tissue cells. The epithelium is 

 rapidly regenerated, the new cells arising from the epithelial remnants at 



