pregnancy and placentation

Question 1

Histotrophic vs hemotrophic nutrition

Answer 1

Pre-implantation, nutrients from uterine secretions (histotrophic nutrition)

Post-implantation, nutrients from maternal blood via hemochorial placenta (hemotrophic nutrition).

Question 2

Development of placenta (time)

Answer 2

Starts: 2wks after feralization (4 LNMP)

Fully functional: end of 12th week after ferilisation (14 LNMP)

Question 3

Functions of placenta

Answer 3

Nutrition
- hemotrophic nutrition
-gas exchange
-waste excretion

immune
-immunomodulatory
-passive immunity

hormonal
-produces hormones that regulate fetal and maternal organs

Question 4

How does the placenta develop?

Answer 4

Extraembryonic mesoderm of cytotrophoblasts and syncytitrophblast form chorion and chorionic villi

Endometrium differentiates into decidua

Fetal chorion and villi combine with decidua basalias = true placenta

Question 5

Stages of Chorion development.

Answer 5

Primary stem vili – 11-13 days after F, CB expands into SB

Secondary stem vili – 16 days after F, extraembryonic mesoderm proliferates into projection (after gastrulation)

Tertiary stem vili – 21 days after F, mesoderm differentiates into CT and blood vessels

Question 6

Compare histological structure of placenta in the three trimesters

Answer 6

Vili:
1- large
2- smaller and more vascular
3- even smaller and highly vascular

cells
1- 2 cell layers (CB and SB)
2- thinning of CB
3- minimal CB

Question 7

Why are the vili of the placenta in the 3rd trimester, small and highly vascularised?

Answer 7

to support blood gas and nutrient exchange required by growing fetus approaching gastrulation

Question 8

What hormones are secreted by the placenta?

Answer 8

HCG

Estrogen

Progesterone

Relaxin

Human chorionic Somatomammmotropin (hCS)

Human chorionic thyrotropin (hCT)

Corticotropin-releasing hormone (CRH)

Question 9

Function of hCG

Answer 9

maintains corpus lutem

Supresses maternal immune system

Question 10

Function of estrogen from placenta

Answer 10

Uterine enlragment

Breast development and blocks prolactin

Relaxes pelvic ligamnets

Question 11

Functions of progesterone from placenta

Answer 11

Maintains functional endometrium

Prevents myometrial contractions

Breast development and blocks PRL

Increased respiratory tidal volume

Question 12

Functions of relaxin

Answer 12

Relaxes pelvic muscles

Cervical softening

Question 13

Function of Hman Chorionic Somatommotropin (hCS)

Answer 13

Decrease glucose metabolism and increased FA metabolsim

Breast development

Question 14

function of
Human chorionic thyrotropin (hCT)

Answer 14

Increase rate of maternal metabolism

Question 15

function of
Corticotropin-releasing hormone (CRH)

Answer 15

Stimulates cortisol production via fetal HPA axis

Question 16

cells that separate maternal and fetal blood

Answer 16

Syncytiotrophoblasts

Cytotrophoblasts

Vilus CT

Fetal capillary endothelium

Question 17

What are the maternal anatomical changes that occur in pregnancy?

Answer 17

Increased vascularity of reproductive organs

Weight gain (13kg) mostly fluids

Breast enlargement

Uterine enlargement

Pelvis and ligaments relax

Question 18

What hormones cause breast enlargement?

Answer 18

E, PE, PRL, hCS and hCG

Question 19

features of uterine enlargement

Answer 19

• fist size –>fills abdominal cavity

increased pressure on internal organs,

alters centre of gravity (lumbar lordoisis and backaches)

Question 20

What are the maternal metabolic change in pregnancy?

Answer 20

Increased appetite

Increase FA metabolism, decreased glucose

Increase rate of maternal metabolism

Question 21

What causes increased appetite in pregnancy and why?

Answer 21

cortisol

elevated fat strohgae and BGL)

Question 22

Cause and purpose of Increase FA metabolism, decreased glucose

Answer 22

hCS

frees up glucose in blood for fetus

Question 23

cause and purpose of Increase rate of maternal metabolism

Answer 23

hCT

elevated calcium for fetal bone development

Question 24

What organ systems change in pregnancy?

Answer 24

GI

Renal

Respirartory

CV

Question 25

Cause and change in the GI system during pregnancy

Answer 25

Via PE and E

changes
Initial nausea

Reflux

Constipation

Question 26

physiological changes that occur to the renal system during pregnancy.

Answer 26

Increase freq and volume of urine

Na and water retention

Question 27

Cause and change in the CV system during pregnancy

Answer 27

Via T3 and T4

Increased blood voulme and periodic increase in CO

Question 28

How is sex determined?

Answer 28

Y Sex chromsome

Sex-determining region on Y (SRY gene) = maleness

Determined by sperm as oocytes only have X

Question 29

the development of the testes or ovaries are dependant on:

Answer 29

presence of XY or aabsence of XX on SRY gene

Question 30

Germ cell formation

Answer 30

Gonadal ridge develops in 5th week

Priodrial germ cells migrate to gonadal ridge to become oogonia or spermatogonia

Question 31

Steps of male embrogenic development

Answer 31

SRY –> TDF in 5th-6th wk

Testes and sertoli cells form in 7th wk

Sertoli cells produce MIF = degenerates paramesonephric duct

HCG tells leydif cells to produce testosterone (supports mesonephric duct)

Mesonephric duct –> epididymis and ductus deferens

Testosterone stimulates testicular descent and development of external genitalia and accessory glands

Question 33

Steps in female reproductive tract development.

Answer 33

ovaries form

paramesonephric ducts survive to form the uterine tubes (as no MIF production)

unsupported by testosterone, the mesonephric ducts degenerate

the ovaries descend and the external genitalia develop

uterine tubes fuse to form the uterus

uterus and cloaca form the vagina

Question 34

Genetic vs Gonadal vs phenotypic sex

Answer 34

Gen= XY or XX
Gon= testis or ovary
Phen= internal and external genitalia

Question 35

What does tropgectoderm form into?

Answer 35

CB and SB = form the placenta

Question 36

what does the inner cell mass/ epiblasts develop into?

Answer 36

form the germ layers: ectoderm, mesoderm and endoderm that is used in gasulraltion and organogeneis.

Question 37

What will happen in pregnancy if the embryo still has not formed a blastocsyst with a functioning trophectoderm 10 days after fertilisation?

Answer 37

Will not secrte hCG so will not be able to maintain corpus luteum. This causes CL to degenerate. Progesterone is NOT produced to support the pregnancy causing a loss of pregnancy