The fallopian tubes or the oviducts/uterine tubes are structures found in the female reproductive system. They are pivotal in transporting the ova or the egg released as a result of the ovulation process from the ovary into the lumen (central channel) of the uterus every month. In case of fertilization as a result of the presence of sperms, the fallopian tubes conduct the transportation of the fertilized egg to the uterus for its firm implantation. The other structures of the female reproductive system include ovaries, uterus, cervix and vagina.
The fallopian tubes are uterine appendages bilaterally situated at the superior part of the uterine cavity. They are the long, slender tubes connecting ovaries to the uterus. It leaves the uterus via the cornua leading to the formation of a link between the peritoneal and endometrial cavities.
The fallopian tubes show fine hair-like projections known as cilia on cells of the lining. These cilia of the tube are necessary for egg-movement from the tube to the uterus. If these cilia are caused any harm as a result of any infection, it may hinder the movement of the egg forward and may continue to stay in this tube itself. Additionally, it may also lead to complete or partial blocking of the tube with scar tissue thereby preventing the egg from physically entering the uterus.
Structure of Fallopian Tubes
Each of the fallopian tubes is 4-5 inches long with a diameter of approximately 0.2–0.6 inches. The channel of the fallopian tubes is lined with a mucous membrane which has several papillae and folds. Papillae are small cone-shaped projections of the tissue.
The mucous membrane has three layers of muscle tissue – the outermost layer has longitudinal fibres ending in several fimbriae (finger-like branches) near the ovaries, leading to the formation of infundibulum – funnel-shaped depository. The middle layer has circular fibres while the innermost layer has fibres arranged spirally.
The infundibulum is the outermost, wide distal section of each of the fallopian tubes. It grasps the eggs released and channels it. The extremities of the fimbriae spread over the ovary contracting close to the surface of the ovary during the ovulation to guide the freely moving egg suitably.
Following the infundibulum is the central, long part of these uterine tubes known as the ampulla. The ampulla and the infundibulum are linked to the uterus through the isthmus – a small area close to 0.8 inches long. The intramural, the last part of the tube is situated in the fundus of the uterus. The intramural duct offers a channel which is the narrowest part of the tube. This structure is the narrow tube in line with the isthmus leading to the uterine wall and the uterine cavity. This is the region where the fertilized eggs typically secure themselves and go on to develop.
This mucous membrane which lines the fallopian tube produces secretions helping the smooth transportation of the sperm and the egg for it to thrive. This fluid mainly comprises sodium, calcium, proteins, chloride, glucose, lactic acid and bicarbonates. The last two constituents are key to the usage of oxygen by sperms in addition to helping the egg in developing after fertilization. While the other constituents mentioned render a suitable environment for fertilization, glucose serves as a nutrient for the sperms and eggs.
The mucous membrane possesses cells containing cilia – fine hair-like projections. They help in the movement of the sex cells. The sperms once deposited in the female reproductive tract typically arrive at the infundibulum in a matter of some hours. In any case, the eggs arrive in the uterine cavity in about 3-4 days. The peristaltic movement in the form of rhythmic muscular contractions in sync with the sweeping motions of the cilia together assist and rightly guide, channelizing the movement of the sperm or the egg. Any damage or abnormalities to the fallopian tube affects the fertility of a woman.
The monthly cycle of changes in the ovaries and the lining of uterus or endometrium is termed as the menstrual cycle. This menstrual cycle ceases when the egg is fertilized, and pregnancy begins. The menstrual cycle occurs in two phases: the follicular phase of the menstrual cycle and the Ovulatory phase of menstrual cycle. The follicular phase is the first day of the period. The following events occur during this follicular phase:
Hormones like Follicle stimulating Hormone (FSH) and Luteinizing Hormone (LH), are released from the brain and travel in the blood to the ovaries.
The hormones stimulate the growth of about 15 to 20 eggs in the ovaries which have a separate shell known as a follicle.
The FSH and LH also trigger a rise in the production of the female hormone called estrogen.