A textbook of obstetrics . ds! ;/, bulging of wall into neck of fetus; ;, ()> externum; //.pouch of Douglas;it posterior vaginal wall (elongated and thinned) ; /, rectum ; k, Stretched anal canal ;/, placenta; m, uterovesical peritoneum; ;/, region of os internum (above whichfragments of membranes are found, and below it portions of cervical glands) ; 0, lowerlimit of bladder; />, anterior vaginal wall (not elongated); </, urethra; r, vagina;s, vulva; /, perineum with blood extravasation Barbour and Webster). ,6o THE MECHANISM OF LABOR. of the fetal skull to the shape of the pelvic
A textbook of obstetrics . ds! ;/, bulging of wall into neck of fetus; ;, ()> externum; //.pouch of Douglas;it posterior vaginal wall (elongated and thinned) ; /, rectum ; k, Stretched anal canal ;/, placenta; m, uterovesical peritoneum; ;/, region of os internum (above whichfragments of membranes are found, and below it portions of cervical glands) ; 0, lowerlimit of bladder; />, anterior vaginal wall (not elongated); </, urethra; r, vagina;s, vulva; /, perineum with blood extravasation Barbour and Webster). ,6o THE MECHANISM OF LABOR. of the fetal skull to the shape of the pelvic inlet by molding ; accommodation f the direction of the head to the direction ofthe pelvic canal by Literal inclination. These movements occurprior to labor, when the head enters the pelvic inlet with thesubsidence of the uterus. Second Step.— Further flexion, molding, and accommodationof the head to the pelvis by lateral inclination, when labor-painsappear, and the head is subjected to a propulsive force and to. Fig. 213.—Flic descent of the head in a vertex presentation, left occipitoanterior position. the resistance of the lower uterine segment, the cervix, and thepelvic walls. Third Step.— Dilatation of the lower uterine cavity and of thecervical canal. Fourth step.—Descent of the head to the pelvic floor, mainlyby an extension of the fetal spine. The fetal body, as a whole,is not yet propelled along the birth-canal, because, during a painand while the head is obviously descending to the pelvic floor,the fundus uteri and the breech do not sink to a lower level. MECHANISM OF PRESENTATIONS IND POSITIONS. \6\ On the contrary, there is a slight elevation of the fundus, anelongation of the uterus, and the distance between the head andthe breech increases during a uterine contraction. Fifth Step.—Anterior rotation of the occiput. The Cause of This Movement—The head, driven through thefunnel-shaped parturient canal, its most dependent portion, thetip of the occiput, f
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Keywords: ., bookcentury1800, bookdecade1890, bookidtex, booksubjectobstetrics
