The Placenta

Question 1

What is the function of the placenta?

Answer 1

Brings fetal and maternal circulations into close proximity, allowing the exchangef of gases, nutrients and waste. It also important for the maintenance of pregnancy, such as Human Chorionic Gonadotropin and Estrogen.

Question 2

The placenta has two sides; one at the fetal and one at the maternal side. What is the name given to both of these?

Answer 2

Fetal side: Chorionic Plate

Maternal side: Basal Plate

Question 3

What are the components of the umbilical cord

Answer 3

2 umbilical arteries (taking stuff away from fetus to mum

1 Umbilical vein (taking stuff from mum to fetus)

Question 4

What fluid is found inside the umbilical cord?

Answer 4

Wharton’s jelly

Question 5

What membrane is found on the surface of the chorionic plate of the placenta?

Answer 5

Avascular glossy amnion (which is a protective membrane)

Question 6

What side of the placenta attaches to the uterus?

Answer 6

The basal plate

Question 7

What is the top layer of the basal plate of the placenta?

Answer 7

Decidua Basalis

Question 8

Describe the appearance of basal plate, and what the tissues contribute

Answer 8

• Surface is separated into lobes called cotelydons, which roughly mark the underlying trees.
• endomterial, trophoblasts and fibroid

Question 9

From what part of the blastocyst does the placenta arise?

Answer 9

The trophoblast

Question 10

At day 9, the trophoblast differentiates into what two layers?

Answer 10

The Cytotrophoblast and the syncitiotrophoblast

Question 11

One of the differentiated layers of trophoblast is very proliferative, whilst the other is non-dividing and has a multi-nucleated appearance. Which is which, and which is on the inside and which is on the outside?

Answer 11

Proliferating: Cytotrophoblast

Non-dividing, multinucleated?: Syncitiotrophoblast

Inner layer is Cytotrophoblast

Outer later is Syncitiotrophoblast

Question 12

What are the names of the spaces that develop within the syncitiotrophoblast? What are they precursor to - and what function does this have?

Answer 12

Lacunae

Intervillous space - the site of exhange between maternal and fetal circulations

Question 13

At around week 12, some of the syncitiotrophoblasts cells migrate deeper into the endometrium in around uterine glands and spinal arteries. Some blood will flow into the lucane at this stage, before what happens?

Answer 13

Trophoblasts block the spiral arteries, thereby preventing any more maternal blood from entering the lucane for the first 10 weeks of pregnancy.

Question 14

So, the lucanea are blocked, but development of the Villous tree is ongoing.

??????? cells migrate, and form ??????? projections that extend towards the ????? plate. These villous projections are surrounded by an outer layer of ??????????. Fetal capillaries also begin to form.

Answer 14

Cytotrophoblast cells migrate, and form villous projections that extend towards the maternal basal plate. These villous projections are surrounded by an outer layer of syncitiotrophoblast. Fetal capillaries also begin to form.

Question 15

Trophoblast invasion is an important factor in the remodelling of the spiral arteries to increase blood flow. Some of the cytotrophoblasts of the vili will differentiate to become ??????????????, which will invade the endometrium, myometrium and then spinal arteries.

Explain the changes that occur to with regards to the hemodynamics of the spinal arteries (stating before and after)

Answer 15

Before: Arteries, are narrow, low flow, high resistance

After: Areies are wider, high flow, low resistance

Question 16

Maternal blood which is rich in oxygen and nutrients flows from the ????? arteries into the ????????????????? surrounding the vili, then back into the uterine veins.

Fetal blood which is low in oxygen and nutrients flows through umbilical arterues to the capillaries of the villi and returns through the ????????

Answer 16

Maternal blood which is rich in oxygen and nutrients flows from the spiral arteries into the intervillious spaces surrounding the vili, then back into the uterine veins.

Fetal blood which is low in oxygen and nutrients flows through umbilical arterues to the capillaries of the villi and returns through the umbilical vein

Question 17

A very SHORT distance separates the maternal and fetal circulations.

Question 18

There are various ways by which nutrients can be transported between the fetal circulation. how are glucose, amino acids and fatty acids transported?

Answer 18

• Glucose - faciliated diffusion
• Amino acids - active transport
• Fatty acids - fatty acid transporter proteins

Question 19

Give examples of drugs that can cross placenta

Answer 19

• Cocaine
• Alcohol

Both of these cross by the same mechanisms as Nutrients in other card.

Question 20

Pregnant women are often not included in what?

Answer 20

Drug trials

Question 21

Describe the Barker Hypothesis

Answer 21

• life in the womb can predispose us to future diseases
  
  • caused by inadequete nutrition

There is lots of information to suggest this is the case.

Question 22

Placental dysfunction could what problems for the fetus? What problems is this also linked to in later life?

Answer 22

• Malnutrition
• Obesity, CV Disease, Diabetes

Question 23

What is the most common complication of pregnancy?

Answer 23

Miscarriage

Question 24

Define Miscarriage

Answer 24

Loss of pregancy during the first 23 weeks. (Anything after week 12 is described as a late miscarriage).

An estimated 1 in 4 pregnancies end in miscarriage.

1 in 100 experience recurrent miscarriages.

Question 25

Define stillbirth

Answer 25

Death of baby after 24 weeks of gestation.

Approximately 1 in 225.

Question 26

Pre-eclampsia is a disorder of late pregnancy. Describe what the clinical findings of the disease are

Answer 26

• sudden onset of hypertension (140/90) occuring after 20 weeks of gestation
• also proteinuria

There are however, atypical presentations of pre-eclampsia that do not fit this model. For example, women with pre-existing hypertension or renal disease.

Question 27

Left untreated, pre-eclampsia can progress to what?

Answer 27

Eclampsia, characterised by convulsions (fits)

Question 28

Exact cause of pre-eclampsia is unclear, but factors include:

Answer 28

• genes
• vascular disease
• immune system
• the placenta itself
• African ethnicity is higher risk

Question 29

What is the pathogenesis of pre-eclampsia?

Answer 29

• Invasion of extravillous trophoblasts is abnormal in some way, and spiral arteries are not remodelled properly and thus blood flow is reduced to placenta
• Since there is higher resistance due to narrow vessels that haven’t been remodelled, BP increases.

Question 30

State the 3 major diagnositic tests used during pregnancy

Answer 30

• Chorionic villus sampling
• Amniocentesis
• Non-invasive Prenatal Testing