Fertilisation And Implantation Flashcards
What is the first hurdle in fertilisation?
Survival of spermatozoa in the vagina
Sperm must survive the vaginal environment to reach the cervix.
What are the factors involved in spermatozoa maturation?
- 100 fold concentration of sperm (oestrogen-dependent)
- Completion of sperm modelling
- Changes in metabolism
- Acquisition of forward motion
- Changes in membrane surface proteins, charge, and fluidity
- Coating of sperm plasma membrane with glycoproteins
Adequate stimulation of the epididymis by androgens is essential.
What mediates coitus in both males and females?
- Sympathetic activity (hypogastric nerve)
- Parasympathetic activity (pelvic nerve)
- Somatic outflow (pudendal nerve)
These activities coordinate the physiological responses involved in sexual intercourse.
What is the role of lactobacillus spp. in the vagina?
They produce lactic acid, maintain an acidic pH (<5), and prevent pathogenic bacterial colonisation
This helps create a protective environment for sperm.
What is capacitation in spermatozoa?
It is a process required for sperm to reach full fertilisation capacity
Capacitation involves loss of glycoproteins coat, revealing binding sites and receptors.
What happens during the acrosome reaction?
Exocytosis of acrosome enzymes occurs, allowing sperm to penetrate the zona pellucida
Enzymes like acrosin and hyaluronidases are involved.
What is the significance of the cumulus oophorus in fertilisation?
It surrounds the ovulated oocyte and aids in its collection by fimbria
This structure is crucial for guiding sperm to the oocyte.
Fill in the blank: Sperm fusion with the oocyte membrane triggers the release of _______ from internal stores in the oocyte.
Ca2+
What are the stages of preimplantation development?
- Zygote (24 hours post-fertilisation)
- Morula (80-96 hours post-fertilisation)
- Blastocyst (120-150 hours post-fertilisation)
Each stage represents significant developmental milestones leading to implantation.
What occurs during the maternal recognition phase?
It involves the embryo signaling its presence to the mother to prevent menstruation
This is crucial for successful implantation.
True or False: The journey of spermatozoa through the uterus is solely dependent on self-propulsion.
False
Other factors like ciliated cells and myometrial contractions also play a role.
What is the role of progesterone during the luteal phase regarding cervical mucus?
It decreases cervical mucus secretion and hydration, making it impermeable to sperm and pathogens
This protects the potential fertilized embryo.
What triggers spermatozoa hyperactivation?
An increase in intracellular Ca2+
This results in ‘whiplashing’ tail beats, enhancing motility.
What is the role of the tetraspanin network in fertilisation?
It facilitates sperm fusion with the egg membrane
Components like CD9 and CD81 are involved.
What are the two main types of receptors involved in sperm attraction to the oocyte?
- Odorant receptors
- Specific receptors responding to chemo-attractive substances
These receptors help direct sperm towards the oocyte in the uterine tube.
What does the term ‘chemotaxis’ refer to in the context of sperm movement?
The movement of sperm towards chemo-attractive substances
This is essential for sperm locating the oocyte.
Fill in the blank: The outer rim of the blastocyst is called _______.
trophoblast
What factors can neutralise the acidic vaginal environment?
- Alkaline seminal fluid
- Immunosuppressive compounds in seminal fluid
These factors help sperm survive the vaginal environment.
What is the significance of the fimbria during ovulation?
They collect the ovulated oocyte from the peritoneal cavity
This is crucial for the oocyte’s journey to the fallopian tube.
What is the rim of trophoblast cells that form a precursor to extra-embryonic support tissue?
Trophectoderm
The trophectoderm is crucial for the formation of the placenta.
What is the fluid-filled cavity within the blastocyst called?
Blastocoel
The blastocoel is essential for the development of the embryo.
What is the first hurdle that spermatozoa must overcome?
Survival of spermatozoa in the vagina
What is the second hurdle that spermatozoa must penetrate?
Penetration through the cervix
What is the third hurdle in the journey of spermatozoa?
Journey through the uterus
What is the fifth hurdle spermatozoa encounter?
Fertilisation of the ovum
What is the fourth hurdle related to spermatozoa?
Entering the uterine tube leading to the ovulated oocyte
What is the sixth hurdle regarding maternal recognition?
Maternal recognition of conceptus
What is the seventh hurdle that involves implantation?
Implantation in the uterus
What hormone do trophoblasts of the blastocyst secrete?
Human chorionic gonadotrophin (hCG)
What is the role of hCG during early pregnancy?
Prevents luteal regression
To what receptors does hCG bind?
LH receptors on the luteal cells
What hormones does hCG stimulate the secretion of?
- Progesterone
- Oestrogen
What are cytokines and growth factors involved in maternal recognition?
- Interleukins
- Transforming growth factor-beta (TGF-β)
- Vascular endothelial growth factor (VEGF)
What do extracellular vesicles modulate in maternal immune responses?
MicroRNAs and proteins
What prevents the cells of the pre-compaction conceptus from separating?
Zona Pellucida
What does the Zona Pellucida prevent in terms of conceptus formation?
Prevents genetically distinct conceptuses from forming a chimera
What do mucins (MUC-1) in the endometrial glycocalyx do?
Prevent binding of the conceptus and guide it to a receptive area
What is the first phase of implantation?
Hatching
What occurs during the hatching phase of implantation?
Zona Pellucida breaks down
What is the second phase of implantation?
Apposition
What characterizes the apposition phase?
Unstable interaction between the blastocyst and the uterine epithelium
What is the third phase of implantation?
Adhesion
What are pinopodes?
Protrusions in the luminal epithelium of the endometrium
What receptors are expressed by trophoblasts during the adhesion phase?
Epidermal Growth Factor (EGF) receptors
What do trophoblasts use to mediate firm adhesion to the endometrial lining?
Cell adhesion molecules such as integrins
What is the fourth phase of implantation?
Invasion
What do trophoblasts differentiate into during the invasion phase?
- Cytotrophoblast
- Syncytiotrophoblast
What do syncytiotrophoblasts secrete to facilitate invasion?
TNFa
What does decidualisation refer to?
Transformation of endometrial stroma into decidual cells
What is the primary decidualisation reaction characterized by?
Oedema and ECM remodelling
What does angiogenesis refer to in the context of implantation?
Increased sprouting and growth of capillaries
What do regulatory T cells do during immune tolerance in pregnancy?
Suppress the activation of effector T cells
What provides nutrients for the developing conceptus during invasion?
Breakdown products from degenerating decidual cells
What is histotrophic nutrition?
Direct uptake of nutrients from maternal blood
What do cytotrophoblastic cells form during invasion?
Finger-like projections in the syncytiotrophoblast (chorionic villi)
What defines the implantation window in terms of timing?
Days 1-7 luteal phase is pre-receptive; Days 7-10 is receptive phase
What happens if there is no implantation during the implantation window?
Refactory phase
What is a common issue that occurs in 75% of cases leading to failure to implant?
Failure of fertilized oocytes to lead to pregnancy
What is the role of contraception methods?
Prevent pregnancy
What is the only contraception method that also protects from STIs/STDs?
Condoms
What is the price range for a male sterilization procedure?
£350-1k
What does mifepristone do?
Prevents progesterone binding to its receptor
