Flashcards in Fertilization Deck (42)
What does seminal fluid consist of?
→ Prostatic and seminal vesicle secretions
What is the function of seminal fluid?
→ It coagulates to prevent loss and later liquefies
What is the function of the cervical mucus?
→ To remove seminal fluid
→ removing morphologically abnormal sperm and cellular debris
When is cervical mucus less viscous and why?
→ in the absence of progesterone
→ allows sperm to pass
What forms a reservoir of sperm in the female?
→ Cervical crypts
When does fertilisation occur within?
→ 24-48 hours
→ sperm have been found alive after 5 days
What attracts the sperm to the egg?
→ Chemoattractants released from the oocyte cumulus complex
→ Sperm become hyperactivated near the egg
How do sperm become hyperactivated near the egg?
→ Forceful tail beats with increased frequency and amplitude
→ mediated by Ca2+ influx via CatSper channels
How is capacitation achieved?
→ Removing the sperm from the seminal fluid
→ uterine or tubal fluid may contain factors which promote capacitation
What must occur to the sperm before the acrosome reaction?
→ Biochemical rearrangement of the surface glycoprotein
→ changes in membrane composition
What time does capacitation occur?
→ 4-16 hours
Where does the acrosome reaction occur?
→ within the zona-cumulus complex
How does the acrosome reaction occur?
→ Acrosomal membrane on the sperm fuses
→ releases enzymes that cut through the zona-cumulus complex
→ acrosin bound to the inner acrosomal membrane digests the zona pellucida so sperm can enter
What causes the oocyte to undergo meiosis?
→ LH spike
What does the LH spike make the oocyte change into?
→ Primary oocyte becomes seconday oocyte + 1st polar body
What does the corpus luteum produce?
What does progesterone do to the endometrium?
→ Makes it secretory and receptive to implantation
What does progesterone do to the cilia?
→ Suppresses cilia in uterine tubes once the oocyte has passed
What does progesterone do the the cervical mucus?
→ It makes it viscous to prevent further sperm penetration
What is the function of estrogen in the luteal phase?
→ Maintains the endometrium
What causes the LH spike?
→ sustained levels of estrogen produced by the dominant follicle
After ovulation what happens to the follicle?
→ it becomes the corpus luteum
What does progesterone do in the secretory phase?
→ Makes the stratum functionalis thicker
→ uterine glands become more secretory
What causes the proliferative phase?
→ Estrogen from the follicular phase
What is the life span of the CL?
→ 14 days
What causes the inter cycle rise of FSH?
→ the fall in CL derived steroids
What does the CL becomes when it dies?
→ Corpus albicans
What happens to the CL in pregnancy?
→ It is rescued by the HcG from the embryo binding to the LH receptors
→ it continues to produce progesterone and maintain the endometrium
What does the menstrual cycle achieve?
→ Selection of a single follicle and oocyte
→ Correct number of chromosomes in the oocyte
→ Changes in cervix and uterine tubes to enable egg transport and sperm access
→ Preparation of the endometrium
→ Support of the implanting embryo