LETTER XXII.. The Pelvis and Its Organs.

THE PELVIS AND ITS ORGANS.

General Description—Differences between the Male and Female Pelvis—The Bladder and Urethra—The Vagina—The Uterus and its Appendages.

Before entering upon the subject of labor and its phenomena, it is proper that I should give you some idea of the parts more immediately concerned in parturition. In doing this, I propose for the most part to adopt the plain and concise description of these structures given by Mr. Erasmus Wilson, of London, whose work on anatomy stands as high as any other that has ever been written.

THE PELVIS.

The pelvis, considered as a whole, is divisible into a false and true pelvis; the former is the expanded portion, bounded on each side by the ossa ilii, and separated from the true pelvis by the linea iliopectinea. The true pelvis is all that portion which is situated beneath the iliopectinea. This line forms the margin or brim of the true pelvis, while the included area is called the inlet. The form of the inlet is heart-shaped, obtusely pointed in front at the symphysis pubis, expanded on each side, and encroached upon behind by a projection of the upper part of the sacrum, which is named the promontory. The cavity is somewhat encroached upon at each side by a smooth quadrangular plane of bone, corresponding with the internal surface of the acetabulum, and leading to the spine of the ischium. In front are two fossæ around the obturator foramina, for lodging the obturator internus muscle, at each side. The inferior termination of the pelvis is very irregular, and is termed the outlet. It is bounded in front by the convergence of the rami of the ischium and pubes, which constitute the arch of the pubes; on each side by the tuberosity of the ischium, and by two irregular fissures formed by the greater and lesser sacro-ischiatic notches; and behind by the lateral borders of the sacrum, and by the coccyx.

A FEMALE PELVIS.

1. The last lumbar vertebra. 2, 2. The intervertebral substance connecting the last lumbar vertebra with the fourth and sacrum. 3. The promontory of the sacrum. 4. The anterior surface of the sacrum, on which its transverse lines and foramina are seen. 5. The tip of the coccyx. 6, 6. The iliac fossæ, forming the lateral boundaries of the false pelvis. 7. The anterior superior spinous process of the ilium; left side. 8. The anterior inferior spinous process. 9. The acetabulum. a. The notch of the acetabulum. b. The body of the ischium. c. Its tuberosity. d. The spine of the ischium seen through the obturator foramen. e. The os pubis. f. The symphysis pubis. g. The arch of the pubes. h. The angle of the os pubis. i. The spine of the pubes; the prominent ridge between h and i is the crest of the pubes. k, k. The pectineal line of the pubes. l, l. The ilio-pectineal line; m, m. The prolongation of this line to the promontory of the sacrum. The line represented by h, i, k, k, l, l, and m, m, is the brim of the true pelvis. n. The ilio-pectineal eminence. o. The smooth surface which supports the femoral vessels. p, p. The great sacro-ischiatic notch. ]

The pelvis is placed obliquely with regard to the trunk of the body, so that the inner surface of the ossa pubis is directed upward, and would support the superincumbent weight of the viscera. The base of the sacrum rises nearly four inches above the level of the upper border of the symphysis pubis and the apex of the coccyx, somewhat more than half an inch above its lower border. If a line were carried through the central axis of the inlet, it would impinge by one extremity against the umbilicus, and by the other against the middle of the coccyx. The axis of the inlet is therefore directed downward and backward, while that of the outlet points downward and forward, and corresponds with a line drawn from the upper part of the sacrum, through the center of the outlet. The axis of the cavity represents a curve, which corresponds very nearly with the curve of the sacrum, the extremities being indicated by the central points of the inlet and outlet. A knowledge of the direction of these axes is most important to the surgeon, as indicating the line in which instruments should be used in operations upon the viscera of the pelvis, and the direction of force in the removal of calculi from the bladder; and to the accoucher, as explaining the course taken by the fetus during parturition.

There are certain striking differences between the male and female pelvis. In the male the bones are thicker, stronger, and more solid, and the cavity deeper and narrower. In the female the bones are lighter and more delicate, the iliac fossæ are large, and the ilia expanded; the inlet, the outlet, and the cavity, are large, and the acetabula farther removed from each other; the cavity is shallow, the tuberosities widely separated, the obturator foramina triangular, and the span of the pubic arch greater. The precise diameter of the inlet and outlet, and the depth of the cavity, are important considerations to the accoucher.

The contents of the pelvis are, the bladder, vagina, uterus with its appendages, and the rectum. Some portion of the small intestines also occupies the upper part of its cavity.

THE BLADDER.

This is in relation with the os pubis in front, with the uterus behind, from which it is usually separated by a convolution of small intestine, and with the neck of the uterus and vagina beneath. The form of the female bladder corresponds with that of the pelvis, being broad from side to side, and often bulging more on one side than on the other. This is particularly evident after frequent parturition. The coats of the bladder are the same as those of the male.

THE URETHRA.

This is about an inch and a half in length, and is lodged in the upper wall of the vagina in its course downward and forward, beneath the arch of the os pubis, to the meatus urinarius. It is lined by mucous membrane, which is disposed in longitudinal folds, and is continuous internally with that of the bladder, and externally with the vulva; the mucous membrane is surrounded by a proper coat of elastic tissue, to which the muscular fibres of the detrusor urinæ are attached. It is to the elastic tissue that is due the remarkable dilatability of the female urethra, and its speedy return to its original diameter. The meatus is encircled by a ring of fibrous tissue, which prevents it from distending with the same facility as the rest of the canal; hence it is sometimes advantageous in performing this operation, to divide the margin of the meatus slightly with the knife.

THE VAGINA.

This is a membranous canal, leading from the vulva to the uterus, and corresponding in direction with the axis of the outlet of the pelvis. It is constricted at its commencement, but near the uterus becomes dilated, and is closed by the contact of the anterior with the posterior wall. Its length is variable; but it is always longer upon the posterior than upon the anterior wall, the former being usually about five or six inches in length, and the latter four or five. It is attached to the cervix of the uterus, which latter projects into the upper extremity of the canal.

In structure, the vagina is composed of a mucous lining, a layer of erectile tissue, and an external tunic of contractile fibrous tissue, resembling the dartos of the scrotum. The upper fourth of the posterior wall is covered, on its pelvic surface, by the peritoneum, while in front the peritoneum is reflected from the upper part of the cervix of the uterus to the posterior surface of the bladder. On each side it gives attachment, superiorly to the broad ligaments of the uterus, and inferiorly to the pelvic fascia and levatores ani.

The mucous membrane presents a number of transverse papillæ or rugæ, upon its upper and lower surfaces, which extend outward on each side from a middle raphé. The transverse papillæ and raphé are more apparent upon the upper than upon the lower surface, and the two raphé are called the columns of the vagina. The mucous membrane is covered by a thin cuticular epithelium, which is continued from the labia, and terminates by a fringed border at about the middle of the cervix uteri.

The middle, or erectile layer, consists of erectile tissue enclosed between two layers of fibrous membrane; this layer is thickest near the commencement of the vagina, and becomes gradually thinner as it approaches the uterus.

The external, or dartoid layer of the vagina, serves to connect it to the surrounding viscera. Thus it is very closely adherent to the under surface of the bladder, and drags that organ down with it in prolapsus uteri. To the rectum it is less closely connected, and that intestine is therefore less frequently affected in prolapsus.

The uterus is a flattened organ, of a pyriform shape, having the base directed upward and forward, and the apex downward and backward in the line of the axis of the inlet of the pelvis, and forming a considerable angle with the course of the vagina. It is convex on its posterior surface, and somewhat flattened upon its anterior aspect. In the unimpregnated state it is about three inches in length, two in breadth across its broadest part, and one in thickness, and is divided into fundus, body, cervix, and os uteri. At the period of puberty, the uterus weighs about one ounce and a half: after parturition, from two to three ounces; and at the ninth month of utero-gestation, from two to four pounds.

The fundus and body are inclosed in a duplicature of peritoneum, which is connected with the two sides of the pelvis, and forms a transverse septum between the bladder and rectum. The folds formed by this duplicature of peritoneum on either side of the organ are the broad ligaments of the uterus. The cervix is the lower portion of the organ; it is distinguished from the body by a well-marked constriction; to its upper part is attached the upper extremity of the vagina, and at its extremity is an opening, which is nearly round in the virgin, and transverse after parturition; the os uteri, bounded before and behind by two labia, the anterior labium being the most thick, and the posterior somewhat the longest. The opening of the os uteri is of considerable size, and is named the orificium uteri externum; the canal then becomes narrowed, and at the upper end of the cervix is constricted into a smaller opening, the orificium internum. At this point the canal of the cervix expands into the shallow triangular cavity of the uterus, the inferior angle corresponding with the orificium internum, and the two superior angles, which are funnel-shaped, and represent the original bicornute condition of the organ, with the commencement of the Fallopian tubes. In the canal of the cervix uteri are two or three longitudinal folds, to which numerous oblique folds converge, so as to give the idea of branches from the stem of a tree; hence this appearance has been denominated the arbor vitæ uterina. Between these folds, and around the os uteri, are numerous mucous follicles. It is the closure of the mouth of one of these follicles, and the subsequent distention of the follicle, with its proper secretion, that occasion those vesicular appearances so often noticed within the mouth and cervix of the uterus, called the ovula of Naboth.

Structure.—The uterus is composed of three tunices: of an external, or serous coat, derived from the peritoneum, which constitutes the duplicatures on each side of the organ, called the broad ligaments; of a middle, or muscular coat, which gives thickness and bulk to the uterus; and of an internal, or mucous membrane, which lines its interior, and is continuous, on the other hand, with the mucous lining of the Fallopian tubes, and on the other with that of the vagina. In the unimpregnated state, the muscular coat is exceedingly condensed in texture, offers considerable resistance to section with the scalpel, and appears to be composed of whitish fibers, inextricably interlaced and intermingled with blood-vessels. In the impregnated uterus the fibers are of large size, and distinct, and are disposed in two layers, superficial and deep. The superficial layer consists of fibers, which pursue a vertical direction, some being longitudinal and others oblique. The longitudinal fibers are found principally upon the middle line, forming a thin plane upon the anterior and posterior face of the organ, and upon its fundus. The oblique fibers occupy chiefly the sides and fundus. At the angles of the uterus, the fibers of the superficial layer are continued outward upon the Fallopian tubes, and into the round ligaments and ligaments of the ovaries. The deep layer consists of two hollow cones of circular fibers, having their apex at the openings of the Fallopian tubes, and by their bases intermingling with each other on the body of the organ. These fibers are continuous with the deep muscular layer of the Fallopian tubes, and indicate the primitive formation of the uterus by the blending of these two canals. Around the cervix uteri the muscular fibers assume a circular form, interlacing with and crossing each other at acute angles. The mucous membrane is provided with a columnar ciliated epithelium, which extends from the middle of the cervix uteri to the extremities of the Fallopian tubes.

Vessels and Nerves.—The arteries of the uterus are the uterine, from the internal iliac, and the spermatic, from the aorta. The veins are very large and remarkable; in the impregnated uterus they are called sinuses, and consist of canals, channeled through the substance of the organ, being merely lined by the internal membrane of the veins. They terminate on each side of the uterus in the uterine plexuses. The lymphatics terminate in the lumbar glands.

The nerves of the uterus are derived from the hypogastric and spermatic plexuses, and from the sacral plexus. They have been made the subject of special investigation by Dr. Robert Lee, who has successfully repaired the omission made by Dr. William Hunter, in this part of the anatomy of the organ. In his numerous dissections of the uterus, both in the unimpregnated and gravid state, Dr. Lee has made the discovery of several large nervous ganglia and plexuses. The principal of these, situated on each side of the cervix uteri, immediately behind the ureter, he terms the hypogastric ganglion; it receives the greater number of the nerves of the hypogastric and sacral plexus, and distributes branches to the uterus, vagina, bladder, and rectum. Of the branches to the uterus, a large fasciculus proceeds upward by the side of the organ, toward its angle, where they communicate with branches of the spermatic plexus, and form another large ganglion, which he designates the spermatic ganglion, and which supplies the fundus uteri. Besides these, Dr. Lee describes vesical and vagina ganglia, and interior and posterior subperitoneal ganglia, and plexuses, which communicate with the preceding, and constitute an extensive nervous rete over the entire uterus. Dr. Lee concludes his observations by remarking: “These dissections prove that the human uterus possesses a great system of nerves, which enlarges the coats, blood-vessels, and absorbents during pregnancy, which returns, after parturition, to its original condition before conception takes place. It is chiefly by the influence of these nerves that the uterus performs the varied functions of menstruation, conception, and parturition, and it is solely by their means that the whole fabric of the nervous system sympathizes with the different morbid affections of the uterus. If these nerves of the uterus could not be demonstrated, its physiology and pathology would be completely inexplicable.”

APPENDAGES OF THE UTERUS.

The appendages of the uterus are inclosed by the lateral duplicatures of peritoneum, called the broad ligaments. They are the Fallopian tubes and ovaries.

VISCERA OF THE FEMALE PELVIS.

1. The symphysis pubis; to the upper part of which the tendon of the rectus muscle is attached. 2. The abdominal parietes. 3. The collection of fat, forming the projection of the mons Veneris. 4. The urinary bladder. 5. The entrance of the left ureter. 6. The canal of the urethra, converted into a mere fissure by the contraction of its walls. 7. The meatus urinarius. 8. The clitoris, with its præputiam, divided through the middle. 9. The left nympha. 10. The left labium majus. 11. The meatus of the vagina, narrowed by the contraction of its sphincter. 12. The canal of the vagina, upon which the transverse rugæ are apparent. 13. The thick wall of separation between the base of the bladder and the vagina. 14. The wall of separation between the vagina and rectum. 15. The perineum. 16. The os uteri. 17. Its cervix. 18. The fundus uteri. The cavitas uteri is seen along the center of the organ. 19. The rectum, showing the disposition of its mucous membrane. 20. The anus. 21. The upper part of the rectum, invested by the peritoneum. 22. The recto-uterine fold of the peritoneum. 23. The utero-vesical fold. 24. The reflexion of the peritoneum, from the apex of the bladder upon the urachus to the internal surface of the abdominal parietes. 25. The last lumbar vertebra. 26. The sacrum. 27. The coccyx. ]

The Fallopian tubes or oviducts—the uterine trumpets of the French writers—are situated in the upper border of the broad ligaments, and are connected with the superior angles of the uterus. They are somewhat trumpet-shaped, being much smaller at the uterine than at the free extremity, and narrower in the middle than at either end. Each tube is about four or five inches in length, and more or less flexuous in its course. The canal of the Fallopian tube is exceedingly minute; its inner extremity opens by means of the ostium uterinum into the upper angle of the cavity of the uterus, and the opposite end into the cavity of the peritoneum. The free or expanded extremity of the Fallopian tube presents a double, and sometimes a triple series of small processes or fringes, which surround the margin of the trumpet or funnel-shaped opening, the ostium abdominale. This fringe-like appendage to the end of the tube has gained for it the appellation of the fimbriated extremity; and the remarkable manner in which this circular fringe applies itself to the surface of the ovary during sexual excitement, the additional title of morsus diaboli. One of the processes, longer than the rest, or, according to Cruveilhier, a distinct ligamentous cord, is attached to the distal end of the ovary, and serves to guide the tube in its seizure of that organ.

The Fallopian tube is composed of three tunices: an external and loose investment derived from the peritoneum; a middle or muscular coat, consisting of circular (internal) and longitudinal (external) fibers, continuous with those of the uterus; and an external or lining mucous membrane, which is continuous, on the one hand, with the mucous membrane of the uterus, and at the opposite extremity with the peritoneum. In the minute canal of the tube, the mucous membrane is thrown into longitudinal folds or rugæ, which indicate the adaptation of the tube to dilatation.

The ovaries are two oblong, flattened, and oval bodies of a whitish color, situated in the posterior layer of peritoneum of the broad ligaments. They are connected to the upper angles of the uterus at each side by means of a rounded cord, consisting chiefly of muscular fibers derived from the uterus, the ligament of the ovary.

In structure, the ovary is composed of a cellulo-fibrous parenchyma or stroma, traversed by blood-vessels, and inclosed in a capsule consisting of three layers: a vascular layer, which is situated most internally, and sends processes inward to the interior of the organ; a middle or fibrous layer of considerable density; and an external investment of peritoneum. In the cells of the stroma of the ovary, the small vesicles or ovisacs of the future ova, the Graafian vesicles, as they have been termed, are developed. There are usually about fifteen fully-formed Graafian vesicles in each ovary; and Dr. Martin Barry has shown that countless numbers of microscopic ovisacs exist in the parenchyma of the organ, and that very few out of these are perfected so as to produce ova.

After conception, a yellow spot, the corpus luteum, is found in one or both ovaries. The corpus luteum is a globular mass of yellow, spongy tissue, traversed by white areolar bands, and containing in its center a small cavity, more or less obliterated, which was originally occupied by the ovum. The interior of the cavity is lined by a puckered membrane, the remains of the ovisac. In recent corpora lutea, the opening by which the ovum escaped from the ovisac through the capsule of the ovary, is distinctly visible; when closed, a small cicatrix may be seen upon the surface of the ovary in the situation of the opening. A similar appearance to the preceding, but of smaller size, and without a central cavity, is sometimes met with in the ovaries of the virgin; this is false corpus luteum.

Vessels and Nerves.—The arteries of the ovaries are the spermatic; their nerves are derived from the spermatic plexus.

The round ligaments are two muscular and fibrous cords situated between the layers of the broad ligaments, and extending from the upper angles of the uterus, and along the spermatic canals to the labia majora, in which they are lost. They are accompanied by a small artery, by several filaments of the spermatic plexus of nerves, and by a plexus of veins. The latter occasionally become varicose, and form a small tumor at the external abdominal ring, which has been mistaken for inguinal hernia. The round ligaments serve to retain the uterus in its proper position in the pelvis, and during utero-gestation to draw the anterior surface of the organ against the abdominal parietes.