1320 THE UKO-GENITAL SYSTEM. 



Structure of the Uterus. The thick uterine wall is composed of three chief layers, 

 which are termed respectively the serous, the muscular, and the mucous coats. 



Tunica Serosa. The serous coat, or perimetrium, is derived from the peritoneum, and 

 covers the whole organ except the part of the cervix which projects into the vagina 

 and the anterior surface of its supra-vaginal portion. At the borders it is continued 

 into the broad ligaments. Over the fundus and body of the uterus the serous coat 

 is very firmly adherent to the deeper layers, and cannot be easily peeled off without 

 tearing either it or the underlying muscular tissue. Near the borders the peritoneum 

 is less firmly attached, and over the posterior aspect of the cervix it may readily be 

 stripped off without injury to the underlying structures. 



Tunica Muscularis. The muscular coat is composed of unstriped fibres, and forms the 

 chief part of the uterine wall. Inferiorly the muscular coat of the uterus becomes 

 continuous with that of the vagina. The more superficial layer of the muscular coat sends 

 prolongations into the recto-uterine folds, into the round and broad ligaments of the 

 uterus, and into the ovarian ligaments. Other fibres join the walls of the uterine tubes. 

 The main branches of the blood-vessels and nerves of the uterus lie among the muscle 

 fibres. In the deeper layers of the muscular coat a considerable amount of connective 

 tissue and some elastic fibres are to be found. The muscular coat of the cervix, or 

 tunica muscularis cervicis, contains more connective and elastic tissue than that of the 

 body, and hence the greater firmness and rigidity of the cervical part of the uterus. 



The deeper and thicker part of the muscular tissue of the uterus is considered by some 

 anatomists to represent a muscularis mucosee, and is therefore described as part of the 

 mucous coat. The deep and superficial portions of the muscular coat are, however, quite 

 continuous, and there is no representative of a submucous vascular layer of tissue such 

 as in the alimentary canal separates the muscular coat from the muscularis mucosse. In 

 the uterus the blood-vessels lie in the muscular coat. 



Tunica Mucosa. The mucous coat in the body of the uterus is smooth and soft, and 

 covered with columnar ciliated epithelium. Simple tubular glands, glandulse uterinse, also 

 lined with a ciliated epithelium, are present in the mucous membrane, and penetrate in their 

 deeper parts into the muscular coat. In the cervix of the uterus the mucous coat is 

 firmer and more fibrous than in the body, and its surface is not smooth, but presents 

 a number of peculiarly disposed ridges which have been already described. Like 

 the mucous membrane of the body of the uterus, that of the cervix is covered with a 

 ciliated epithelium which passes into squamous epithelium just inside the external orifice of 

 the uterus. The cervix uteri possesses, in addition to unbranched tubular glands, re- 

 sembling those present in the body, numerous somewhat branched glands, the glandulae 

 cervicales uteri. Both kinds of glands are lined by ciliated epithelium. In many 

 cases little clear retention cysts, "ovules of Naboth," are to be seen in the cervical 

 mucous membrane. These arise as a result of obstruction at the mouths of the glands. 



Differences in the Uterus at Different Ages. At birth the cervix uteri is 

 relatively larger than in the adult organ, and its cavity is not distinctly marked 

 off from the interior of the body by an internal orifice. At this time also the 

 plicae palmatse extend throughout the whole length of the uterus. The organ grows 

 slowly until just before puberty, when its growth is rapid for a time. As the 

 body of the uterus increases in size the mucous membrane becomes smooth and the 

 plicae palmatae become restricted to the cervix. In women who have borne 

 children the cavity remains permanently somewhat wider and larger than in cases 

 where the uterus has never been pregnant. 



In old age the uterine wall becomes harder and has a paler colour than it 

 possesses in the young subject. 



Variations. In rare cases the uterus may be divided by a septum into two distinct cavities, 

 or its lateral angles may be produced into straight or curved processes, called " horns " or cornua. 

 The latter abnormality recalls the appearance of the bicornuate uteri of some animals. Both the 

 above conditions arise from an arrest in the fusion of the two separate tubes the Miillerian 

 ducts which normally unite in the embryo to form the uterus. 



Periodic Changes in the Uterine Wall. At each menstrual period a remark- 

 able series of changes occurs which results in a periodic shedding of the super- 

 ficial parts of the uterine mucous membrane. For a few days before menstruation 

 begins, the mucous membrane gradually thickens and becomes more vascular, while 

 at the same time its surface becomes uneven. Soon the superficial parts of the 



