Fertilisation Flashcards
What type of reflex is ejaculation a part of
Parasympathetic Reflex
What happens to arterioles and the smooth muscle and why does that happen
Arterioles Dilate
Smooth muscles relax
Due to release of nitric oxide
The penis is now engorged with blood and the expansion compresses veins making blood leave slower
How is the reflex stimulated
Via sensory stimuli
Spinal reflex is initiated due to sympathetic discharge to the genital organs
Reproductive ducts will contract prismatically
What muscle induces contractions to propel semen?
Bulbocavernous Muscle
What does Viagra do ?
- Viagra inhibits PDE5 which will decrease cGMP breakdown
- This causes a prolonged arteriolar dilation hence a prolonged erection
What degrades cGMP
Phosphodiesterase 5
What makes up the seminal fluid ( 2 )
Seminal plasma and cells
What makes up the seminal plasma ( 3 )
Prostatic Fluid ( 30 % ) Epididymal Fluid ( 5 % ) Seminal Vesicle Fluid ( 65 % )
What cells are part of the seminal fluid
Spermatozoa
Leucocytes
Volume of Sperm during ejaculation
2 - 6 ml
pH of the sperm
7.2 - 8.0
- Count
- Total Count
- Morphology
- Viability
- WBC
- > 20 mil
- > 40 mil
- > 30% normal form
- > 75 %
- < 1 mill / ml
What is used as a marker for seminal vesicle function
Fructose
What does prostaglandin help with in terms of sperm ?
Helps with sperm motility
What is used as a marker for epididymal function
Alpha - Glucosidase
- What is the biomarker for prostate cancer
- What produces it ?
- Prostatic Specific Antigen
- The epithelial cells of the prostate produces it
- What is the marker used for prostate function
- What is the marker used for prostatic function
- Zinc
- Acid Phosphatase
What glycoprotein is incorporated into the sperm membrane
CD52
What are the prostatic secretions ( 6 )
- Calcium
- Zinc
- Citric Acid ( which is usually v hi concentration but low when have prostate cancer )
- Acid Phosphatase
- Prostatic Specific Antigen
- Albumin
How does the sperm cell membrane change during capacitation
Alterations in Surface Glycoprotein
Removal of cholesterol to increase fluidity of membrane
Loss of glycoprotein which exposes Egg Binding Protein
Fluctuation of Calcium ( to activate cAMP then phosphorylate protein )
How is the Egg Binding Protein Exposed
- HCO3- influx into the sperm cell membrane
- AMP is activated which leads to cholesterol efflux
- Causes Ca2+ influx
- Activates cAMP
- Activation of protein tyrosine kinase
- Leads to phosphorylation of protein
- Exposure occurs
How does Capacitation affect the sperm
- Increase in metabolism
- Increased rate of beating in flagellum
- Acrosomal enzymes are activated ( Pro - Acrosome changes to acrosin )
What increases uterine contractility to help in sperm transport ( 3 )
- Ovarian Steroids ( hi oestrogen in follicular phase makes cervical mucus thin and alkaline )
- Prostaglandins from the Seminal Fluid
- Oxytocin
Journey of sperm
1) 2.5 x 10^8 will be deposited in the vagina
2) Only 100,000 will reach uterine cavity
3) < 50 reaches the distal end of the fallopian tube
4) Fertilisation occurs at the ampullary isthmic junction resulting in a delay ( Day 1 - 2 )
5) Another delay at the Utero - tubal junction ( D2 - D3 )
6) Egg enters uterine cavity as morula ( D3 - D4 )
7) Implantation of Blastocyst at Day 7
Where is the zona pellucida first detected
Primary Follicle
What makes up the Zona Pellucida
Sulphated glycoproteins
Why does cross fertilisation rarely occur?
Zona Pellucida has a Species Specific Barrier
How many ZP glycoproteins are there and what do they do
3
- ZP3 : Mediates Sperm Specific Egg Binding
Sperm and carbohydrate receptor
- ZP2: Mediates Subsequent Sperm Binding
turns the sperm sideways
- ZP1 : Forms a cross link between ZP3 and ZP2
Which ZP glycoprotein is not essential for fertilisation
ZP 1
What sperm receptors are crucial in sperm - egg binding
Galtase ( no galtase, no binding )
What egg receptors are crucial in sperm - egg binding
O - linked oligosaccharide residues of ZP3
What reactions are initiated when the egg - sperm binds together ?
In the sperm - Acrosomal Reaction
In the egg - Cortical Reaction
What is the Acrosomal Reaction
Sperm - Egg Binding leads to receptor clustering and exocytosis of acrosome to digest Zona Pellucida
1) Binding of Sperm and ZP activates IP3
2) Increases Ca in the acrosome membrane and flagellum
3) Digestive enzymes are activated
Explain the Cortical Reaction
- Carried out by cortical granules
- Membrane bound granules that are formed beneath egg cell membrane
- Released at fertilisation which helps digest zona pellucida
- Also helps prevent polyspermy
What causes a decreased effectiveness in blocking polyspermy
- Heating of Ova
- Age of Ova
- Excessive Sperm Numbers
What is a sperm pronucleus
When a haploid nucleus sperm enters eggs
Embryonic Development Stages
Zygote → 2 cell stage → 4 cell stage → 8 cell stage → Morula → Blastula → Early gastrula → Late Gastrula
How do you make uni parental embryos
-ARTIFICIAL STIMULATION
Using a Ca2+ ionophore and electrical activation
Microinjection of Ca2+ into cytoplasm
- INHIBITION OF MPF ( CYCLIN B )
-BLOCKADE OF SECOND POLAR BODY EXTRUSION
You get a parthenope, uni parental with 2 maternal genomes
