Pregnancy Flashcards
What happens during capacitation
Capacitation happens in female reproductive tract
- decapacitation factor is washed away by uterine fluid
- loss of high cholesterol environment (testes) weakens acrosomal cap (cholesterol hardens cap)
- sperm becomes permeable to Ca- activates whip like activity of flagella in tail
What does decapacitation factor due? Where is it produced
Epididymis
Suppress motility
Prevent capacitation reaction
Acrosome functions
Break granulosa cells- hyaluronidase = break down hyaluronic acid which is part of the connective tissue
Break zona pellucida- proteolytic enzymes
Function of Ca with sperm
Whip like motion of flagella in tail
What day of menstral cycle does fertilization occur
Day 16-17
Note ovulation 14
Steps of fertilization
- Hyaluronidase (in acrosome) breaks down granulosa cells and sperm bind to ZP3 glycoprotein (sperm has ZP3 receptor)
- Sperm-ZP3 interaction initiates the acrosomal reaction. Acrosomal reaction disrupts the acrosomal membrane, releasing proteolytic contents. Proteolytic enzymes bore into zona pellucida and digest it
3-4. Sperm penetrate ZP and fuse with oocyte membrane. Cytoplasmic portions of sperm enter oocyte. Accomplished by chemical- acrosomal enzymes and mechanical- sperm tail thrashing (Ca dependent)
5-6. Cortical reaction initiated by intracellular Ca release from intracellular stores of oocyte. Cortical reaction- exocytosis of granules that contain enzymes that harden ZP. Purpose to ensure only one sperm can penetrate the ovum. ovum complete second meiotic division to become haploid in preparation for fertilization
- Sperm nucleus decondenses and tail degenerates
- Male and female haploid pro nuclei fuse- form diploid zygote. Fertilization complete
- Fertilized ovum transported to uterus (3 days) during which cell divisions occur. End result blastocyst in uterus (100 cells). Uterine tube secretions provide nourishment
Importance acrosomal reaction
Disrupt acrosomal mebrane- breaking down
Proteolytic enzymes released- bore into ZP and digest it
Importantance cortical reaction
Harden ZP so no other sperm can penetrate ovum
Zygote development stages while travelling to uterus
Zygote- 1 cell- ampulla of uterine tube
Morulla- 16 cells- uterine tube
Blastocyst- 100 cells- uterus
How long between fertilization and implantation
3-4 days
Implantation day 20 menstrual cycle
Blastocyst properties
Has LH receptors
Secrete HCG- save corpus luteum
Secrete immunosuppressant
Blastocyst will become embryo
Why is implantation delayed after fertilization
Important for cell division and endometrium
What is decidualization ? what hormone maintains it?
Occurs before implantation
Changes to endometrium inner layers- decidua basalis (implant zone), decidua capsularis (surround embryo), decidua parietalis (surround rest of uterine surface)
- progesterone from CL maintains decidualised endometrium
- uterine milk- secretions from uterus that nourish blastocyst and embryo stages
What is uterine milk
glandular secretions- proteins, iron, fat soluble vitamins, cholesterol, nutrients
Nourish blastocyst and embryo stages
4 events of implantation
- Hatching and alignment of trophoblast- lytic factors break down zona pellucida (hardened state to degeneration). Trophoblast replaces outer layer (trophoblast will become placenta)
- Apposition- ruptured ZP causes blastocyst wall to lose contact with endometrial wall. Inner cell mass of blastocyst aligned with epithelium (of endometrium- same cells talked about throughout)
- Adhesion- ligand receptor interactions (integrin family- transmembrane proteins). Trophoblast (outer layer) attaches to uterus endometrial epithelium
- Invasion- syncytiotrophoblast invades endometrium. Trophoblast divides in two- syncytiotrophoblast + cytotrophoblast (outer layers still)
- blastocyst eventually fully embeds in decidua and reaches maternal blood supply
What is in contact with maternal blood supply
Lacuna- fluid filled pools- exchange site
Exchanges excretions for maternal blood
Syncytiotrophoblast and cytotrophoblast role in placenta development
Syn- Lacuna pools and mother blood vessels. Maternal part of placenta
Cyto- fetus blood vessels that reach into lacuna. Fetal part of placenta
What reaches into lacuna to pick up maternal blood
Cytotrophoblast- finger like projections reach in. Will become fetal blood vessels
Mature placenta key parts
Intervillous space- used to be lacuna. Filled with maternal blood
Mature chorionic villus- whole area. Covered with syncytiotrophoblast
Fetal Arterioles/venules- from cytotrophoblast
Umbilical vein- to fetus, oxygenated blood, nutrients
Umbilical artery- from fetus
When does fetus heart start to beat
4 weeks
Roles of placenta
- site of exchange between mom and fetus
Lungs
GI tract
Kidneys- waste removal and electrolyte balance
Liver- waste removal
What are the four circulatory shunts
Placenta- exchange site for maternal and fetal blood, nutrients
Ductus arteriosus- connect right pulmonary arteries to the aorta. Blood stays in systemic circulation. Flow to pulmonary vessels is low due to hypoxic vasoconstriction
Ductus venosus- connect umbilical vein to inferior vena cava
Foreman ovale- connect RA to LA. Allows ventricles to pump in parallel. Mixing of oxygenated and deoxygenated blood
Discuss fetal oxygenation and the Bohr effect
Left shift of oxygen dissociation curve.
Fetal hemoglobin is more efficient at up taking O2 at lower pressures of oxygen compared to mom (less oxygen available but still can uptake)
Carry 25-50% more oxygen at low PO2
Hemoglobin concentration of fetal blood is 50% higher than mother
——
Placenta has low PCO2- fetal blood uptakes O2
In fetus high PCO2- fetal blood release O2 to its tissues
- all oxygen to fetus dependent on Hb- no lungs
What are the roles of the 3 hormones of pregnancy
- Human Chorionic Gonadotropin- maintains the corpus luteum until the placenta takes over (12 weeks drop starts)
- HCG produced by blastocyst
- cause of morning sickness (severe= hyperemesis gravidarum)
- tested for in pregnancy tests - Estriol (E17B)- most important estrogen when pregnant- enlarge uterus, enlargement and ductal growth of breast tissue, relax pelvic ligaments
- Progesterone- decidualisation, lobular breast development, quiescent uterus- no contractions
When is the switch from corpus luteum to placenta
8-12 weeks of pregnancy
Explain maternal placental fetal unit- what does DHEA-S stand for
Hint- two important pathways
One for estrogen and one for progesterone- both of which fetus cannot be exposed to
Pg 14 pregnancy
Other hormonal support of pregnancy- other than P + E
Pituitary -ACTH, TSH and prolactin -near complete suppression of LH and FSH (via inhibition from estrogen and P)
Corticosteroids -glucocorticoids (mobilise a.a. from mother for fetal tissue synthesis) -
aldosterone – 50% more salt retention and expansion of blood volume (1.5-2L)
Erythropoetin -increased red blood cell production in bone marrow
Thyroid hormone -enlarges 50% and increases thyroxine secretion 50% (hCG) Parathyroid hormone -enlarge and reabsorb Ca2+ from maternal bones / teeth to support fetal needs
Relaxin -from corpus luteum and placenta -relaxes ligaments of pubic symphysis, softens cervix and inhibits uterine contractions
factors relating to pregnancy lose
- Increased maternal age
- Weight: underweight and overweight
- Smoking/alcohol/drugs
- ≥2 prior pregnancy losses
- Chronic conditions e.g. uncontrolled diabetes/thyroid disease
When are most pregnancy’s lost- what % of los preg are from this time
First 12 weeks
80% of pregnancies
What can cause pregnancy lose
Causes Chromosomal abnormalities (~50%) – inherited or random
Maternal factors: cervical competence; uterine fibroids; endocrine imbalance; infections
Lots are Unknown
What could be a sign of pregnancy loss
Heavy or delayed period
% pregnancy’s lost out of all pregnancy’s vs the known pregnancy (persona aware of pregnancy)
Pr egnancy loss occurs 30-50% of all pregnancies and ~10-20% of known pregnancies
