Placenta, Cord and Membranes Flashcards
What are the 5 functions of the placenta?
- Respiration: provides the fetus with oxygen (diffusion from the maternal body to the fetal circulatory system. This is because the fetal lungs are not functioning before birth.
- Nutrition: active transport of glucose, irons and some vitamins. The placenta can metabolise carbohydrates, protein and fats into simple molecules. The placenta stores glycogen which can be broken into glucose if energy is needed.
- Hormone Production: the placenta acts as an endocrine gland and adjusts maternal physiology to provide an optimal environment for fetal development.
- Excretion: amnion secretes amniotic fluid to replace the old one as the fetus excreted urine and waste products from metabolic reactions.
- Protection: acts as a barrier for most small bacteria. some small viruses and microorganisms can cross the villi.
the placenta transfers IgB antibodies. However, smoking, alcohol and drugs diffuse into the fetus and can cause the brain to not develop as well and conditions such as fetal alcohol syndrome
What happens during implantation for the zygote?
During implantation, the zygote implants itself near the fundus of the uterus and starts to multiply into a morula which then multiplies into a blastocyst.
What are the three main parts of a blastocyst?
- Trophoblast: which eventually forms the placenta and the chorion. Develops finger-like projections –> CHORIONIC VILLI.
- Inner cell mass: will form the embryo
- Blastocyst cavity: becomes a fluid-filled cavity
What occurs after implantation is finished?
The villi with the most abundant blood vessels multiply and the rest creates the chorionic membrane.
HcG helps to form the placenta by week 10 and by 12-20 weeks gestation the placenta can carry out all metabolic reactions.
How does a placenta at term look like (stage the diameter, thickness and weight)
The placenta is flat and round and is 20cm in diameter, 2.5cm thick and weighs around 600g (normally 1/6th the baby’s birth weight)
What are the two sides of the placenta and what is their function?
Chorion (developed from the trophoblast) and Amnion.
Chorion is the maternal, outer surface and is attached to the decidua. It is arranged into lobes called cotyledons. Each cotyledon contains numerous lobules and every lobule has one chorionic villus and provides maximum contact with maternal blood due to the large surface area.
Amnion is the inner, fetal surface and is covered by the amniotic membrane. it secrets amniotic fluid and at term, this surface is white and shiny.
What is the umbilical cord and the function?
It connects the fetus to the placenta at the fetal umbilicus. It is 50cm long and 2cm wide. it consists of ONE VEINS AND TWO ARTERY. The cord is composed of Wharton’s gel and is a spiral twist to add strength.
What is amniotic fluid and its function?
The amniotic fluid is the fluid that surrounds the fetus. it cushions the fetus and protects it from the pressure of the uterine walls and noise from the body systems. Around 1000ml of amniotic fluid is considered normal.
What is amniocentesis?
Examination of the amniotic fluid can reveal information about the condition of the baby.
Cells shed from the fetal skin which carries the fetal DNA
Genetic abnormalities can be determined
What are the abnormal quantities of the amniotic fluid?
Polygohydramnious- 1500ml of amniotic fluid. It is usually associated with a congenital defect in the fetus (neural tube defect). It can cause discomfort to the mother. A lot of care should be taken during labour as the sudden compression of the uterus can cause placental abruption or umbilical cord prolapse. Usually, need to have an ARM and after delivery, the baby is examined for abnormalities.
Oligohydramnios- less than 500ml. It is usually associated with fetal abnormalities such as the absence of kidneys and dries out the fetus.
What are the anomalies of the placenta?
Succenturiate lobe
Placenta accreta and percreta
Placenta praevia
Vasa praevia
What is a succenturiate lobe?
When there is an extra lobe growing onto the placenta. Blood vessels will run through this lobe and can cause intrapartum bleeding. During delivery of the placenta, the lobe might be retained which can cause a secondary haemorrhage or an infection. The midwife will notice this as there is a hole missing on the main placenta.
What is placenta accreta and percreta?
A normal placenta will embed itself into the lining of the uterus.
Placenta accreta will mean that the placenta is embedded further than the lining of the uterus.
Placenta percreta will mean that the placenta is embedded further than the lining of the placenta and into the endometrium muscle.
What is placental praevia and what can it cause?
When the placenta is situated in the lower segment of the uterus. A major will cover the cervix and can cause a haemorrhage whereas a minor placental praevia will just be close to the cervix.
What is vasa praevia and what can it cause?
When the blood vessels of the placenta cover the cervical os which can cause a haemorrhage.
