Theme C lecture 6 Flashcards
What is the function of the placenta?
It is the interface between the mother and the fetus responsible for exchange of gas and nutrients.
Placenta acts as a barrier
Immune function
Hormone production
How are nutrients and important gasses transmitted to the fetus?
Passive transport (diffusion)
Facilitated Diffusion
Active transport
Vesicular transport
What stuff passes through the placenta via passive transport?
O2
Steroid hormones
Fetal waste - Uric acid, Urea, creatinine
What stuff passes through the placenta via active transport?
Amino acids
Folate
Micronutrients
What stuff pass through the placenta via facilitated diffusion?
GLUT transporters transport glucose
What kind of molecules are transported by vesicular transport?
Large molecules (eg immunoglobulins)
How does the placenta act as a barrier?
Placenta metabolizes compounds as they pass through
How does the placenta prevent the higher concentration of glucocorticoids in the mother from reaching the fetus?
Placenta expresses 11beta-HSD2 to convert active glucocorticoids into inactive metabolites
What immune function does the placenta perform?
Placenta modulates maternal immune system to prevent rejection.
How does the placenta carry out its immune function?
Placenta secretes neurokinin B which binds to phosphocholines which parasites use to evade the immune system.
Placenta inhibits maternal T-cells via lymphocytic suppressors
Which antibodies cross the placenta and provide immunity for the fetus in early life?
IgG
Can diseases pass through the placenta?
Several conditions can pass from the mother to the fetus via the placenta but not all.
What is the placenta’s endocrine function?
Produces Growth factors such as , Lactogen, IGF2, Prolactin, Growth Hormone
Produces progesterone which maintains endometrial lining, and prevents preterm labour.
Produces hunger regulating hormones to regulate mother’s eating. (leptin/ghrelin)
Many other factors are produced by the placenta which include VEGF (family of growth factors) and Corticotropin releasing hormone
What is the function of placental lactogen?
Regulates maternal insulin levels (increases fatty acids and glucose in the blood)
What is the function of placental progesterone?
Maintains endometrial lining, prevents preterm labor.
What is the function of leptin/ghrelin?
Peptide hormones that regulate maternal hunger/appetite
Where does the placenta originally develop and how does this happen?
Placenta starts developing early in pregnancy and is important for implantation.
Where is the embryological origin of the placenta?
Trophoblast forms the placenta as it thickens at the point it connects to the uterus
How does the placenta anchor the fetus to the wall of the uterus?
Trophoblasts invade through the endometrial wall and arteries are produced which provide blood supply to the placenta.
What is placentation?
The development of specialised regions of fetal and maternal origin. When maternal cells and zygote-derived fetal cells come together within close proximity.
When does placentation complete itself during pregnancy in humans?
by the end of the 1st trimester of pregnancy.
*Placenta is the first organ to develop during pregnancy and the largest organ to be produced during gestation.
What is required for a normal pregnancy?
The placenta needs to develop at the correct position
What is placenta previa?
As the placenta grows it covers the cervix such that the fetus has no passage to pass out through which would cause the death of the mother.
How is placenta previa treated?
C-section is the best and safest method.
What is placenta accrecia?
The fetus invades far beyond that depth that is considered normal and grows through the uterus and hurts structures such as the bladder.
When the placenta comes out it often causes severe blood loss because it tears much of the uterus and the bladder.
What are some other conditions that influence placental development?
Pre-eclampsia
Gestational hypertension
Diabetes/Gestational diabetes
Over- undernutrition
Chronic stress
Asthma
What effect do maternal conditions have on fetal development?
Maternal conditions can affect blood flow, nutrient availability, and endocrine function of the placenta causing altered fetal development.
How are placentas classified?
classified based on the number of placental layers.
Which maternal layer do humans have?
Hemochorial
What happens at the hemochorial layer of the placenta?
Blood comes in from mother and forms a bath of blood in which the placental capillaries sit.
What is the difference between epitheliochorial and hemochorial placentas?
Tree of capillaries interact and form complex networks of blood vessels to transfer material
Whereas in humans the fetal blood vessels sit in a bath of maternal blood.
What animals have hemochorial placentas?
The hemochorial placentas are only really found in higher order primates and rodents
What placental shape do humans have?
Diacoid placenta is what humans have
What type of shapes can the placenta have?
Multicotyledonary (multiple implantation points sheep have it)
Diffuse (encapsulates entire fetus)
Discoid (humans and mice have it)
Zonary (ring around the fetus found in dogs and cats)
What is a hemomonochorial placenta?
Hemomonochorial placenta is a placenta with a single type of layer between maternal and fetal blood.
What are the layers between maternal and fetal blood in a hemodichorial placenta?
Hemodichorial placenta contains a layer of Syncytiotrophoblast and cytotrophoblast.
What is the kind of layer found between the maternal and fetal blood in a hememonochorial placenta?
Syncytiotrophoblast
What layers exist between maternal and fetal blood in a hemotrichorial placenta?
hemotrichorial placenta contains 2 layers of syncytiotrophoblast and a layer of sinusoidal giant cells
What are cytotrophoblast?
they are the precursor to syncytiotrophoblast
What kind of blood
Rodents have more branching called a labrynth. Maternal interactions are through a blood space nevertheless.
What is different about rodent placental function compared to humans?
Rodents have more cell types and each cell type does a different function.
Humans have more functions being performed by the same cells
What is the function of the junctional zone?
rodents have a junctional zone which produce hormones
What is the extravillous region?
The point of the maternal uterus that interacts with the placenta.
What 2 regions can be found in the placenta?
Villous region
Extravillous region
How do perturbations affect males and females?
Males and females are often impacted in different ways by maternal factors
What were the effects of famine on the placenta?
Lighter placenta
Reduced surface area
This affected boys more than girls
What is the result of reduced placental size and surface area?
Glucose intolerance
Coronary heart disease
Increased stress responsiveness
Obesity
What is the placental ratio important for?
If the placenta is too large it is often inefficient.
If the placenta is too small it is poorly developed and also not effective.
The ideal ratio provides optimal growth.
What is the placental ratio?
Ratio between
fetus weight:placenta weight
What is the effect of surface area on cardiovascular disease risk?
If the placenta has too much or too little surface area there is an increase of cardiovascular risk with age.
What are some conditions that are correlated with a high placental ratio?
Hypertension
Coronary Heart Disease in both men and women
Glucose intolerance
What are some conditions that are correlated with a low placental ratio?
coronary heart disease in males.
What are some causes of problems during fetal development caused by the placenta?
impaired placental structure.
Dysregulated nutrient transport
Impaired endocrine functions
dysregulated placental barrier.
Why are male babies more prone to developmental programming of disease?
placenta of male fetus prioritise making baby large. Female placenta doesn’t mind.
What does HSD11B2 break down cortisol into?
cortisone
What does HSD11B2 break down corticosterone into?
11 deoxycorticosterone
What does HSD11B2 break down dexamethasone (DEX) into?
11-ketodexamethasone
How is HSD11B2 related to programming of disease?
HSD11B2 can be dysregulated by multiple perturbations in maternal physiology.
What is the effect of ethanol on the placenta in females compared to males?
Placenta is better protected from ethanol in females than in males.
What does hypoxia do to HSD11B2 expression?
hypoxia reduces HSD11B2
What are the adaptations that cause males to be more likely to develop disease than females?
Males take more risky growth than females.
