Placenta

Question 1

What type of placenta does humans have?

Answer 1

Discoid

Question 2

What are the caruncles?

Answer 2

Implantation site of the placenta

Question 3

Sheep placenta - What happens once the placenta implants on the caruncle bump?

Answer 3

It invades into the caruncle bumps to create a placentome (both caruncle and cotyledon (fetal)). This also has a vascular system

Question 4

How does the vascular system work?

Answer 4

There is a flow - nutrients from mother to baby, and waste from baby to mother

Question 5

Do veins bring oxygen to baby from mother?

Answer 5

Yes which is unusual as its a vein not an artery

Question 6

Does the baby or mothers side of the placenta have veins/arteries etc?

Answer 6

Baby

Question 7

What are the stretchy membrane around the edge of the placenta?

Answer 7

Fetal membrane sac where baby sits (fetal membranes which are trophoblasts).

Question 8

What are the villi in the human placenta?

Answer 8

Site of placental exchange

Question 9

Outer most layer of placenta is what?

Answer 9

Trophoblasts

Question 10

What is the placenta in humans and rodents?

Answer 10

Haemochorial (interphase is blood trophoblast) - discoid

Question 11

What is the placenta in pig and horse?

Answer 11

Epitheliochorial - definite maternal and fetal tissue (diffuse)

Question 12

What is the placenta in the sheep and cow?

Answer 12

Synepitheliochorial - epithelial, trophoblast intermediatory (cotyledonary)

Question 13

After implantation what happens at 8 weeks in a human pregnancy?

Answer 13

Amnion and chorion form a sac around fetus (chorion has a trophoblast).

Question 14

What is the role of the placenta - protection of fetus from maternal immune system?

Answer 14

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

Question 15

What is the second role of the placenta - transfer?

Answer 15

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

Question 16

Role of placenta - endocrine organ - what hormones does this secrete and what does it do?

Answer 16

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

Question 17

Sheep - what do the trophoblast cells in the sheep do?

Answer 17

Secrete progesterone,

Question 18

How is fetal growth assessed?

Answer 18

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

Question 19

What is crown rump length?

Answer 19

This helps us understand how big the baby is

Question 20

What factors affect prenantal growth? (5)

Answer 20

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.

Question 21

How can the placenta restrict fetus growth?

Answer 21

• abnormal differentation or maternal nutrition limitations
• pathophysiological reduction in blood flow (pregnancy induced hypertension, pre-eclampsia).