Lecture 6.1: Placental Development and Pregnancy Flashcards
What does the Trophoblast differentiate into? (2)
- Syncytiotrophoblast
- Cytotrophoblast
What does the Embryoblast differentiate into? (2)
- Epiblast
- Hypoblast
Which trophoblast differentiate invades the uterine wall? On what day?
- Syncytiotrophoblast
- Day 6
Degraded contents of uterine cells engulfed by the trophoblast are used to feed the embryo until….?
links with maternal capillaries are made
What day does the bilaminar disk form?
Day 7-9
By the end of week 2: what are the 2 cavites surrounding the embryo?
- Amniotic Cavity
- Yolk Sac
What is the supporting sac at the end of week 2 called?
Chorionic Cavity
What is the role of the yolk sac?
Provides nutrients until placenta ready to take over
What does the Chorion go on to form? What is its role?
- Placenta
- Provide Nutrition for Embryo
What does the Allantois go on to form? What is its role?
- Umbilical Chord
- Waste Disposal
What is the Amnion?
Membrane surrounding amniotic fluid
Twins: When are there 2 chorions and 2 amnions?
- 2 morulas and 2 blastocytes
- Could be 2 separate eggs or 1 egg splits into 2 at
zygotic stage - Separate implantation sites
Twins: When are there 2 amnions but a shared chorion?
- 1 morula but 2 ICMs and bilaminar disks
Twins: When are there is shared amnions and a shared chorion?
- 1 blastocyte and bilaminar disk but 2 primitive streaks
The human placenta is haemomonochorial, what does this mean?
Only one layer of trophoblast ultimately separates maternal blood from foetal capillary wall
Why does the placental membrane get thinner?
To fulfil the needs of the foetus as they increase
What are the aims of the implantation of a foetus? (3)
- Establish the basic unit of exchange (villi)
- Anchor the placenta
- Establish maternal blood flow within the placenta
What are Primary Villi?
Early finger-like projections of trophoblast
What are Secondary Villi?
Invasion of mesenchyme into core
Tertiary Villi
Invasion of mesenchyme core by foetal vessels
What is Decidualisation?
Functional and morphological changes that occur within the endometrium to form the decidual lining into which the blastocyst implants
What hormone signals to the endometrium to prepared
for implantation each month?
Progesterone
What do endometrial stromal cells do?
Secrete growth factors and signalling molecules
What do uterine natural killer cells do?
Regulate the immune response against the non-self embryo
What happens in remodelling of the spiral arteries?
Modifies the arteries from low-flow, high-resistance to high-flow, low-resistance vessels
Why does remodelling of the spiral arteries occur?
Maintains the high flow required to meet foetal demand
What happens to the cytotrophoblast layer of the placenta as pregnancy progresses?
It is lost, as placenta becomes thinner so that nutritional needs of foetus can be better met
What structure links placental blood vessels with developing foetus?
Umbilical Chord
What vessels does the umbilical chord contain?
- Two umbilical arteries (deoxygenated blood from
foetus to placenta) - One umbilical vein (oxygenated blood from placenta to
foetus)
What are the 3 ways the placenta allows transport of materials from mother to foetus?
- Simple Diffusion
- Active Transport
- Facilitated Diffusion
What materials are transported via Simple Diffusion between mother and foetus? (4)
- Water
- Electrolytes
- Urea & uric acid
- Gases (foetal O2 stores are small so maintenance of
adequate flow is essential)
What materials are transported via Facilitated Diffusion between mother and foetus?
Glucose
What materials are transported via Active Transport between mother and foetus? (3)
- Specific “transporters” expressed by the
syncytiotrophoblast - Amino Acids
- Iron
- Vitamins
How is Passive Immunity passed from mother to foetus? What Ig specifically?
- Receptor-mediated transport process
- IgG
The Placenta is also involved in metabolism, what substances does it synthesis? (3)
- Glycogen
- Cholesterol
- Fatty acids
Why does the placenta synthesise glycogen?
Storage of maternal glucose for transfer to foetus later as necessary
Why does the placenta synthesise cholesterol?
It is a precursor for oestrogen and progesterone
What steroid hormones does the placenta produce? (2)
- Oestrogen
- Progesterone
What protein hormones does the placenta produce? (4)
- Human Chorionic Gonadotrophin (hCG)
- Human Chorionic Stomatomammotrophin
- Human Chorionic Thyrotrophin
- Human Chorionic Corticotrophin
What is a molar pregnancy (hydatidiform mole)?
- A gestational trophoblastic disease (GTD), which
originates from the placenta and can metastasise - It is unique in that the tumour originates from
gestational tissue rather than from maternal tissue
What is a choriocarcinoma?
A malignant, fast-growing tumour that develops from trophoblastic cells
What effect does placental progesterone have on maternal metabolism?
Causes increased appetite
What effect does hCS/hPL have on maternal metabolism?
Increases glucose availability to foetus by switching mother from glucose to fatty acid metabolism
What effects does Relaxin have on the mother? (4)
- Increases flexibility of pubic symphysis
- Increases size of pelvis
- Suppresses oxytocin release thereby preventing
premature labour - Causes dilation of cervix before delivery
Dysfunctions in Implantation: Ectopic Pregnancy
Implantation at site other than uterus (most commonly fallopian tubes)
Dysfunctions in Implantation: Complication of Lower Uterine Implantation (3)
- Placenta Praevia (placenta attaches in the lower part
of your uterus, sometimes completely covering the
cervix) - Haemorrhage in Pregnancy or during Birth
- Require C-section
Dysfunctions in Placental Invasion
Inadequate invasion of trophoblasts to reach the maternal vessels
What teratogens can access the foetus via the placenta? (5)
- Thalidomide
- Alcohol
- Therapeutic drugs
- Drugs of abuse
- Maternal smoking
What is haemolytic disease of the newborn?
Occurs when the immune system of the mother sees a baby’s RBCs as foreign, Rhesus blood group incompatibility of mother and foetus
What maternal systems/physiological change during pregnancy? (6)
- Cardiovascular System
- Urinary System
- Respiratory System
- Metabolic Changes
- Gastrointestinal System
- Immune System
What happens to blood volume during pregnancy?
It Increases
Is BP affected by pregnancy?
Systolic BP is never normally increased in pregnancy
What is Pre-eclampsia?
Having high blood pressure (hypertension) and protein in your urine (proteinuria) during pregnancy
How is Pre-eclampsia treated?
Deliver the baby
What is Eclampsia?
Eclampsia is unexplained generalised seizures in patients with preeclampsia
What changes occur in the urinary system during pregnancy? (7)
- Glomerular filtration rate (GFR) increases
- Renal plasma flow increases
- Filtration capacity intact
- Functional renal reserve decreases as GFR increases
- Increased kidney volume
- Ureter dilation
- Increased bladder capacity
What happens to cardiac output, stroke volume,
heart rate in pregnancy?
Increases
What happens to systematic vascular resistance and
blood pressure in pregnancy?
Decreases
What happens to the subcostal angle during pregnancy?
Increases
What increases in the respiratory system during pregnancy? (3)
- Subcostal Angle
- Anterior-Posterior and Transverse Diameters of the
Chest Wall - Chest Wall Circumference
What provides substrate for maternal metabolism, leaving glucose for the foetus?
Free fatty acids
What is Gestational Diabetes?
Occurs when your body can’t make enough insulin during your pregnancy, thus increased blood sugar levels
Effects of Gestational Diabetes on Baby
- Baby being very large
- Being born early
- Having low blood sugar after birth
Effects of poorly controlled Gestational Diabetes on Baby (3)
- Congenital Defects
- Developing type 2 diabetes later in life
- Having low blood sugar after birth (baby will have
hyperinsulin due to mother’s diabetes)
Pregnancy is a pro-thrombotic state, what does this increase risk of? (4)
- VTE/DVT
- PE
- Heart Attack
- Stroke
Why can Anaemia occur in Pregnancy?
If you don’t have enough iron stores or folate, you could develop iron deficiency anaemia
Effects of pregnancy related anaemia on foetus (2)
- Increases the risk of premature birth
- Baby may not grow as much as it should
What are the diagnostic criteria for pre-eclampsia (3)
- Thrombocytopenia
- Proteinuria
- Hypertension