Placenta Flashcards
What type of placenta does humans have?
Discoid
What are the caruncles?
Implantation site of the placenta
Sheep placenta - What happens once the placenta implants on the caruncle bump?
It invades into the caruncle bumps to create a placentome (both caruncle and cotyledon (fetal)). This also has a vascular system
How does the vascular system work?
There is a flow - nutrients from mother to baby, and waste from baby to mother
Do veins bring oxygen to baby from mother?
Yes which is unusual as its a vein not an artery
Does the baby or mothers side of the placenta have veins/arteries etc?
Baby
What are the stretchy membrane around the edge of the placenta?
Fetal membrane sac where baby sits (fetal membranes which are trophoblasts).
What are the villi in the human placenta?
Site of placental exchange
Outer most layer of placenta is what?
Trophoblasts
What is the placenta in humans and rodents?
Haemochorial (interphase is blood trophoblast) - discoid
What is the placenta in pig and horse?
Epitheliochorial - definite maternal and fetal tissue (diffuse)
What is the placenta in the sheep and cow?
Synepitheliochorial - epithelial, trophoblast intermediatory (cotyledonary)
After implantation what happens at 8 weeks in a human pregnancy?
Amnion and chorion form a sac around fetus (chorion has a trophoblast).
What is the role of the placenta - protection of fetus from maternal immune system?
Immunosuppression
Self/non-self (HLA-G) inhibiting NK cells
Semi-allograft (trophoblast layer at interfaceand uterus specific)
Cross talk against the endometrium resident cells and the immune system as it is invading
What is the second role of the placenta - transfer?
Diffusion - O2, CO2, fatty acids, steroids, lipophilic (transcellular and high permeability), hydrophilic (diffusion limites)
Facilitated diffusion - membrane-bound carrier proteins
Active transport - sodium dependant and independant
Endocytosis - lipoproteins and immunoglobins for passive immunity
Role of placenta - endocrine organ - what hormones does this secrete and what does it do?
hCG 0 has to have homology with gonadotrophins, rescue CL
Progesterone - immune supression, suppression of uterine activity, anithestic
Oestrogens - blood volume and vascular tone, parturition
Other peptide hormones e.g. CRH, placental lactogen
Sheep - what do the trophoblast cells in the sheep do?
Secrete progesterone,
How is fetal growth assessed?
Ultrasound
- in early pregnancy monitors viability, gestational age, fetal number or any serious pathology
- detailed anomaly scan
- placenta and amniotic fluid check
- fetal growth and assessment
- Invasive procedures
What is crown rump length?
This helps us understand how big the baby is
What factors affect prenantal growth? (5)
1) Fetal and maternal geneme and genetic factors e.g. if parents are small = small baby
2) Hormones and growth factors including insulin (gestational diabetes = big baby), placental lactogen, thyroxine, GH, and growth factors
3) Maternal nutrition and health
4) Environmental factors
5) Litter size and duration of pregnancy - e.g. small animals grow fast with big litter sizes.
How can the placenta restrict fetus growth?
- abnormal differentation or maternal nutrition limitations
- pathophysiological reduction in blood flow (pregnancy induced hypertension, pre-eclampsia).
