Review of Ob/ GYN
The Bony Pelvis is central to any consideration of Ob/GYN because it is the location of the sexual organs as well as the site of gestation and particularly because birth involves the transit through the pelvis.
Like every other aspect of biology, the pelvis comes in variety of shapes and sizes. In general the female pelvis comes in four basic shapes, the Gynaecoid, Android, Platypelloid, and Anthopoid.
The Gynaecoid pelvis, with its round brim, flat walls, and non-prominent ischial spines that allows passage of the baby with the least amount of trauma is the the ‘genuine female’ pelvis.
The Android pelvis has a less symmetrical, heart-shaped opening is more common amongst tall, narrow-hipped or African women. This shape may lead to longer, more traumatic labor.
The Anthopoid pelvis is oval with the obstetrical diameter being longer. Once the baby enters the pelvis birth often proceeds without complication.
The Plattypelloid pelvis is also oval, with the transverse diameter being longer. Although the baby may have difficulty in entering the pelvis, birth should proceed without difficulty.
Internally, the female reproductive tract is straightforward and laterally symmetrical. Many of the terms, meaning prefixes and roots are similarly named to other body parts.
The womb / uterus (Gr. metra) is comprised of three layers. Internally it is lined with an endothelial layer called the endometrium (inside the womb). Under the endothelium is a muscular layer called the myometrium (muscle of the womb). The external part of the womb is covered with a perimetrium, or serous layer derived from the visceral peritoneium.
The vagina leads to the cervix (or more properly cervix uteri, neck of the uterus) which is comprised of a cervical canal connecting the vagina to the uterine cavity. The cervical opening on the uterine side is known as the internal os, while the opening to the vagina is the external os. (L. os – mouth). Within, the cervix is comprised of numerous folds of the endocervix corming crypts in which sperm can be released into the uterus over several hours.
Two ovaries are ‘connected’ to the uterus via fallopian tubes (named for a 16th century Italian anatomist, Gabriele Falloppio).
The Infundibulum (L. Funnel) of the fallopian tube (or oviduct) with extended fimbriae is the opening of the fallopian tube proximal to the ovary through which ova move during ovulation. The tube continues as an ampulla (the diminutive of amphora, the double handled jugs used for storage and trade, see illustration), isthmus (stretch of land), and finally the interstitium (space between objects) that crosses through the muscular wall of the uterus into its lumen.
Fertilization and early pregnancy
Fertilization occurs very soon after ovulation as sperm (typically) meet the ovum while it is en route through the fallopian tube toward the uterus. The (haploid) egg and (haploid) sperm fuse to form a (diploid) zygote that begins dividing immediately. About seven days later, the early embryo (now a blastocyst) will implant into the endometrium, where it will continue to grow into an fetus.