A complex and coordinated interplay of numerous variables is required for the transportation of embryos and gametes (sperm and ovum) via the fallopian tube. Fallopian tubes are tubular organs with one end linked to the uterus and the other end located close to the ovary. It aids in removing the ovum from the fimbrial end, moving, maturing, and storing sperm, fertilising the ovum with sperm, creating an embryo, and ultimately moving the embryo to the uterus. Knowing the tubal anatomy and functioning is necessary to comprehend the tubal transport of the embryo and gamete.
Four segments make up a fallopian tube, and each plays a unique part in fertilisation and healthy pregnancy. Segments spanning the medial to lateral sides include:
- The fimbriae, or first section, are about 25 projections that resemble fingers. This end’s fimbriae assist in picking up the ovum,
- The second segment of the tube is the main section where sperm and egg fertilization takes place.
- The common site for ectopic pregnancy in the third part, and
- The fourth segment is where the tube enters the uterus and carries the embryo there.
Fallopian tubes mostly consist of two types of cells, including Cilia are hair-like structures that aid in the movement of the gamete and embryo in cells with ciliary activity. Another type of cell is one that secretes tubal fluid, which aids in the nourishment and transportation of gametes and embryos.
The hormones secreted by the ovaries have an impact on the tubal epithelium, which alters. Therefore, more ciliated cells are present in the early phases of the monthly cycle than secretory cells are in the late phases.
Numerous elements, including as hormonal signals, neurological input with ciliary motility, muscle contractility, tubal fluid, ovarian hormones, and follicular fluid, affect tubal transport.
The amount of activity and frequency of ciliary movement are influenced by a variety of hormonal and neurological variables. Ovarian hormones and other bioactive substances are also crucial. The most crucial ciliary projections for sperm and egg motility. These cilia are impacted by a variety of disorders, and even if the tubes are open if they are broken, pregnancy cannot be conceived.
In the fallopian tubes, there are two different forms of contraction, including:
The first continuous contraction acts as a functional gate between the uterus and the fallopian tube, permitting the passage of gametes and embryos only when conditions are ideal on either side. By regulating the rate at which sperm are released into the ampulla, it also prevents polyspermy, which is the admission of numerous sperm.
Frequent intermittent contraction, which propels tubal fluid and aids in ovum pickup, is the second type of contraction.
Tubal fluid, which contains a few bioactive chemicals that influence ciliary activity and muscle contractility, is released by secretory cells of the tubal lining. Potassium, bicarbonate, and a few significant bioactive substances are abundant in it. Phase of the menstrual cycle affects glucose levels. Midcycle is when the most tubal fluid forms. Additionally, it aids in gamete and embryo feeding.
Diseases and conditions which affect tubal transport-
Inflammatory substances secreted as a result of the disease process in endometriosis lead to aberrant tubal movement and a decrease in the frequency of ciliary movement. The normal fertilisation and transportation of gametes and embryos may be hampered by tube scarring.
Smoking affects ciliary movement frequency, tubal blood flow, and tubal motility. Tubal transport is also impacted by PID, infections like gonorrhoea, chlamydia, and TB, as well as congenital conditions such immotile cilia syndrome.
For spontaneous conception, gamete and embryo transportation through tubes must be coordinated and managed, as well as sperm maturation, oocyte fertilisation, and early embryo development.
Therefore, a patent tube with a normal lining, cilia function, contractility, and tubal fluid secretion is necessary for a successful pregnancy. In vitro fertilisation can be used to help with spontaneous conception when one or more of the aforementioned elements is malfunctioning.