Capacitation and Sperm transport

CAPACITATION

Capacitation is a complex process that sperm undergo in the female reproductive tract, rendering them capable of fertilizing an egg. It involves biochemical and physiological changes that occur after ejaculation and as the sperm travel through the female reproductive system. Here are the key aspects of capacitation:

1. Removal of Surface Proteins:
• Sperm leaving the male reproductive tract are covered with glycoproteins that need to be removed for fertilization to occur.
• The female reproductive tract provides conditions that lead to the removal of these surface proteins.
2. Changes in Membrane Fluidity:
• The sperm membrane undergoes changes in fluidity during capacitation, allowing it to fuse with the egg membrane.
3. Hyperactivated Motility:
• Capacitated sperm exhibit hyperactivated motility, characterized by increased amplitude and asymmetrical flagellar beating.
• This enhanced motility helps sperm navigate the female reproductive tract and approach the egg.
4. Acrosome Reaction Readiness:
• Capacitation prepares the sperm for the acrosome reaction, an essential step in fertilization where enzymes are released to aid in penetrating the egg's protective layers.
5. Increased Intracellular Calcium:
• Capacitation is associated with an influx of calcium ions into the sperm, which is crucial for various signaling pathways and cellular changes.
6. Duration and Location:
• Capacitation can take several hours and occurs as sperm traverse the female reproductive tract, specifically in the uterus and fallopian tubes.

In summary, capacitation primes sperm for fertilization by modifying their membrane properties, enhancing motility, and preparing them for the acrosome reaction.

Sperm Transport:

After ejaculation, sperm must traverse the female reproductive tract to reach the site of fertilization. The journey involves several stages:

1. Cervical Mucus Interaction:
• Sperm must navigate through the cervical mucus, which can serve as a barrier or facilitator, depending on the woman's menstrual cycle.
• Cervical mucus changes in consistency during the menstrual cycle, becoming more receptive to sperm around the time of ovulation.
2. Uterine Transport:
• Sperm travel through the cervix and into the uterus.
• Contractions of the uterine muscles aid in sperm transport.
3. Fallopian Tube Migration:
• The final destination for fertilization is typically the fallopian tubes.
• Sperm movement through the fallopian tubes is facilitated by both muscular contractions and the ciliary action of the tube's epithelial cells.
4. Chemotaxis and Thermotaxis:
• Sperm exhibit chemotaxis, following chemical signals released by the egg, guiding them toward the site of fertilization.
• Sperm also respond to temperature gradients (thermotaxis) within the female reproductive tract.
5. Survival in the Female Reproductive Tract:
• Sperm can survive for several days within the female reproductive tract, allowing them to be present and functional when the egg is released during ovulation.

Both capacitation and sperm transport are crucial for successful fertilization. Capacitation ensures that sperm are functionally competent for fertilization, while sperm transport involves their passage through the female reproductive tract to reach the egg. These processes are finely regulated and contribute to the overall success of natural conception.