Sperm Capacitation Flashcards
What is sperm capacitation?
It is the process by which sperm gain the ability to fertilize an oocyte, involving ionic changes, cAMP activation, and removal of cholesterol from the sperm membrane.
How do reactive oxygen species affect sperm?
ROS can damage sperm DNA and membranes, but antioxidants like Vitamin E protect against this damage.
What is the significance of CatSper channels in sperm?
They transport calcium into sperm, essential for motility and hyperactivation during capacitation.
How do prostaglandins in semen aid sperm transport?
Prostaglandins stimulate myometrial contractions, helping sperm move through the uterus.
What are prostasomes, and what role do they play in fertilization?
Prostasomes, secreted by the prostate gland, deliver calcium ions to sperm, aiding motility and capacitation.
How do bicarbonate ions influence sperm capacitation?
Bicarbonate ions activate adenylate cyclase, increasing cAMP levels, which enhance sperm motility and prepare them for the acrosome reaction.
What are the three major complications sperm face after ejaculation in the vagina?
Gravity, sudden acidic environment and presence of immune cells
What is ejaculated first during sperm entry into the vagina?
Sperm-rich prostatic fluid is ejaculated first.
What happens to human semen shortly after ejaculation?
Human semen coagulates within about a minute after ejaculation due to proteins secreted by the seminal vesicle (Semenogelin-1 and 2) and zinc
What is the function of semen coagulation, and how is it degraded?
The coagulation helps hold the sperm at the cervical os. The coagulum is degraded by prostate-specific antigen (PSA).
What effect does the vaginal pH < 5 have?
Vaginal pH < 5 helps protect against infections such as harmful bacteria, yeast (Candida), and pathogens like Gardnerella, which causes bacterial vaginosis
How does lactobacilli bacteria contribute to vaginal health?
Lactobacilli bacteria convert glycogen into lactic acid, which supports the acidic environment and helps prevent infections
How does semen affect the vaginal pH, and how is the pH restored?
Semen has a neutralising effect on the vaginal pH, but this effect is temporary. Lactobacilli bacteria gradually restore the vaginal pH
How does vaginal pH change throughout the menstrual cycle?
Vaginal pH is strongly acidic during the mid-cycle, supporting the acidic environment for protection against infections.
What are the main components of cervical mucus?
Water
Glycoproteins (including mucins, which give mucus its viscosity)
Ions and bicarbonate (which influence its pH)
Immunoglobulins (IgG and IgA for mucosal immunity)
How does cervical mucus vary throughout the menstrual cycle?
During ovulation, the cervical mucus becomes more watery and fertile due to the influence of estrogen. During non-ovulatory phases, mucus is thicker and more acidic due to the influence of progesterone
How does cervical mucus affect sperm transport?
Cervical mucus scrubs and selectively allows only sperm with a certain motility and morphology to pass through the cervix.
What factors influence sperm’s ability to penetrate cervical mucus?
Sperm motility, morphology, and hormonal changes (such as oestrogen and progesterone levels) influence sperm’s ability to penetrate cervical mucus
What conditions can cause blockages in the cervix that affect sperm transport?
Infections and inflammation, such as cervicitis, chlamydia, or gonorrhoea, can cause blockages in the cervix
What is the role of the stroma in the cervix?
The stroma, which consists of a collagen matrix and fibroblasts, regulates the rigidity of the cervical wall
What is the function of the epithelium in the cervix?
The epithelium, made up of columnar epithelial cells, is the site of mucus production and contains sodium and water pumps that are influenced by hormones
Where is the mucus thickness in the cervix the thickest and thinnest?
The mucus is thickest in the central canal and thinner in the secondary grooves
Why is the central canal of the cervix significant in terms of immune cells?
The central canal contains a high concentration of immune cells, which can potentially affect sperm viability.
What is the optimal path for sperm through the cervix to avoid thick mucus and immune cells?
The optimal route for sperm is to pass through the primary grooves and secondary grooves, avoiding the thick mucus and immune cells in the central canal.
What role do myometrial contractions play in sperm transport?
Myometrial contractions, particularly pro-ovarian contractions, help draw cervical mucus into the uterine cavity, providing sperm with more volume and direction
How do smooth muscle contractions in the uterus vary during the menstrual cycle?
During the follicular phase, ultrasonography reveals cranially directed waves of smooth muscle contraction that increase in intensity. These contractions are thought to be stimulated by prostaglandins in semen, as opposed to the more general contractions during menstruation that involve all layers of the myometrium.
What happens to sperm in the isthmus of the uterus?
In the isthmus of the uterus, sperm bind to epithelial cells, forming a temporary reservoir. The sperm are stored there and are slowly released toward the ampulla
What role do prostasomes play in sperm capacitation?
Prostasomes, secreted by the prostate gland, deliver calcium ions to the sperm, which are essential for maintaining motility and enabling capacitation. These prostasomes fuse with the sperm membrane
What ions are involved in capacitation, and what do they contribute to?
Capacitation involves the influx of bicarbonate ions and the efflux of potassium ions. These ions are crucial for activating adenylate cyclase, which increases cyclic AMP (cAMP) levels, a key second messenger for capacitation
How does bicarbonate contribute to sperm capacitation?
Bicarbonate ions increase the intracellular pH, which in turn activates the CatSper channels. These channels help transport calcium into the sperm cell, facilitating capacitation.
What is the function of the Hv1 proton pump in capacitation?
The Hv1 proton pump expels hydrogen ions (H+) from the sperm cell, further increasing the intracellular pH, which supports capacitation.
What is the role of cAMP in sperm capacitation?
Elevated levels of cAMP activate protein kinase A (PKA), which then phosphorylates various proteins on tyrosine residues. These phosphorylation events are essential for changes in the sperm tail, enhancing motility and preparing the sperm for the acrosome reaction.
Why is protein phosphorylation important for sperm motility?
Protein phosphorylation is crucial for molecular changes in the sperm tail, which increase motility and prepare the sperm for the acrosome reaction, necessary for fertilization.
How does Vitamin E protect sperm from ROS damage?
Vitamin E, a fat-soluble antioxidant, neutralizes ROS and is incorporated into the plasma membrane of sperm to protect it from oxidative damage.
Why are sperm membranes particularly vulnerable to damage from ROS?
Sperm membranes are rich in polyunsaturated fats, which are highly susceptible to lipid peroxidation by ROS. This makes them more prone to damage
What happens to sperm after they lose Vitamin E during passage through mucus?
After losing Vitamin E, sperm become more susceptible to ROS-induced damage. However, normal sperm are typically able to cope with this loss, while abnormal sperm cannot handle the damage effectively.
How does Vitamin E affect sperm motility and function?
By neutralizing ROS, Vitamin E helps maintain the integrity of the sperm’s plasma membrane, preventing DNA damage and ensuring proper motility and function.
How does the removal of cholesterol from the sperm plasma membrane affect sperm capacitation?
The removal of cholesterol from the sperm plasma membrane begins in the uterus and makes the membrane more fluid and less rigid. This change is important for enabling capacitation and the subsequent acrosome reaction
What substance is used in clinical settings to remove cholesterol from sperm membranes?
Human serum albumin is used in clinical settings to remove cholesterol from the sperm plasma membrane.
What role does sialic binding protein (SABP) play in sperm capacitation?
Sialic binding protein (SABP) is secreted by endometrial cells and binds to the sperm plasma membrane. Along with cholesterol removal, SABP facilitates calcium entry into the sperm, which is crucial for capacitation
What changes occur to the sperm plasma membrane during capacitation?
During capacitation, the sperm plasma membrane undergoes changes in its architecture and its charge. These changes are critical for enabling sperm to undergo the acrosome reaction and fertilize the egg
How does the female reproductive tract influence sperm capacitation through bicarbonate channels?
In the female reproductive tract, bicarbonate channels allow more bicarbonate ions into the sperm cell. This stimulation activates SACY (sodium adenylate cyclase) and CatSper, which contributes to sperm hyperactivation
What is sperm hyperactivation, and why is it important for fertilization?
Sperm hyperactivation is characterized by jagged or erratic swimming patterns. This hyperactivation is important for helping sperm navigate through the cumulus cells and zona pellucida to reach and fertilize the egg
