Repro 8 Flashcards
By roughly what day has the blastocyst fully embedded into the endometrium? Which two structures interact for implantation to occur?
By roughly day 10, the blastocyst has implanted into the endometrium.
The synctiotrophoblast interacts with the simple columnar epithelium of the endometrium.
Explain what is meant by the term ‘haemomonochorial’ when applied to the placenta
Only a single layer of trophoblast separates the foetal blood and maternal blood.
Describe the differences between primary, secondary and tertiary villi, when discussing implantation.
Primary
- day 13
- finger like projections of trophoblast
Secondary
- day 15-16
- invasion of mesenchyme into the core
Tertiary
- day 23
- invasion of foetal blood vessels into mesenchyme
Name two implantation defects and briefly describe them and their associated risks.
- Ectopic pregnancy
- implantation at a site that is not the uterine body- commonly the Fallopian tubes
- can be ovarian or peritoneal
- can become life threatening very quickly
- Placenta praevia
- implantation in the lower uterine segment
- can cause haemorrhage in pregnancy
- requires C-section delivery
What is decidualisation?
This provides a balancing force for the invasive force of the trophoblast. It ensures the trophoblast doesn’t invade further than it needs to.
Why do you think there is a risk of haemorrhage in ectopic pregnancy?
The decidual cells are present in the uterus so they can control implantation invasive force.
In sites that are not the uterus, there are no decidual cells so there is no balancing force in terms of invasive force. Therefore there is nothing to stop the trophoblast from invading further and further. There are many arteries nearby so they can easily become invaded
What does remodelling of the spiral arteries achieve ?
Creates a low resistance vascular bed which can maintain the high flow required to meet foetal demand.
Very important in late gestation.
What is pre eclampsia and how is it characterised?
It is a pre cursor to maternal seizures (eclampsia)
Characterised by proteinuria and hypertension.
Describe the features of first trimester placenta
- Relatively thick, so it acts as a barrier to diffusion
- cytotrophoblast layer beneath the synctiotrophoblast
Describe the features of a term placenta
- Very thin - allows diffusion to take place easily
- no cytotrophoblast beneath the synctiotrophoblast
- surface area available for diffusion increased massively.
What are cotyledons and how are they formed ?
Decidual septum forms and projects into the intervillous space of the placenta. It doesn’t reach the chorionic plate but it divides the placenta. These divisions are called cotyledons.
The placental barrier gets thicker as pregnancy proceeds, to ensure the foetus gets blood supply constantly as its metabolic demands increase, particularly due to the brain getting larger. True or false?
False.
The placental barrier gets smaller as pregnancy proceeds.
At week 38, it’s roughly 5 micrometers compared to 40 micrometers at week 14.
Describe the arrangement of foetal blood vessels within the placenta.
Umbilical arteries and veins project into the tertiary villi, which are bathed in maternal blood.
2 Umbilical arteries carry DEOXYGENATED blood from the foetus back to the placenta.
1 umbilical vein carries OXYGENATED blood from the placental blood to the foetus.
Cotyledons receive blood from the spiral arteries, which are high pressured. This forces blood out of the arteries into the intervillous spaces.
Name some functions of the placenta
Metabolism
Transport
Endocrine
Describe the metabolic function of the placenta.
Synthesises:
- glycogen
- fatty acids
- cholesterol
Outline the endocrine function of the placenta.
Secretes steroid and protein hormones.
What steroid hormones does the placenta secrete and what is the function?
These are released to maintain the pregnant state. They take over from the corpus luteum around week 11.
Progesterone and oestrogen are secreted
- progesterone increases appetite, which lays down fat stores for when the metabolic demands of the foetus increase in later pregnancy.
What protein hormones are secrete from the placenta and what is their function?
hCG
- secreted from the synctiotrophoblast in the first two months
- supports the secretory function of the corpus luteum
- absence of this hormone within the luteal phase leads to break down of the corpus luteum. It’s the signal it waits for.
- pregnancy specific
Human chorionic somatomammotrophin (hCS)
- influences metabolism. It increases the amount of glucose available to the foetus. Achieved by causing insulin resistance.
hPL - insulin resistance
hCT and hCC
What is the basis for pregnancy tests based on urine sample?
hCG is released from synctiotrophoblast and is therefore pregnancy specific.
It’s released in the urine so therefore testing the urine for the presence of this hormone is diagnostic.
What is a ‘hydatidiform mole’
Name one other disease that falls under the same category of diseases
This is a trophoblast disease.
This is a molar pregnancy, where there is a ‘pregnancy’ without a conceptus. It’s essentially uncontrolled synctiotrophoblast.
Another disease is choriocarcinoma.
Identify and outline the way major substances are transported across the placenta by simple diffusion
- down concentration gradient
- water
- electrolytes
- urea and uric acid
- gases
GLUCOSE - facilitated diffusion not active transport or simple diffusion!
Identify the major substances which are actively transported across the placenta
- amino acids
- iron
- vitamins
Specific transporters are expressed by the synctiotrophoblast.
Describe the placenta as a provider of passive immunity from the mother to the neonate
Foetus can make all of the components of complement by the end of the first trimester.
- week 14 - maternal IgG passes to foetus via receptor mediated pinocytosis.
What are the signs in a foetus that rubella has crossed the placenta?
PDA
Cataracts
Microcephaly.
