13 – Placenta Flashcards
1
Q
Placenta comprised of fetal and maternal tissue
A
- Chorioallantoic
- Choriovitelline (short lived in domestic species, ex. horses)
- Endometrium
2
Q
What are the major functional units of the placenta?
A
- Chorionic villi
o Projections on the surface of the chorion that closely interact with maternal tissue
3
Q
Individual cells of chorionic villi=
A
- Trophoblast
4
Q
Due to differences in placental shape, structure and invasiveness large differences in
A
- Endocrinological and
- Immunological and
- Metabolic communication between mother and fetus
5
Q
Placental transport types
A
- Diffusion
- Facilitated diffusion
- Active transport
- Receptor-mediated endocytosis
6
Q
Diffusion in placenta
A
- Gases (ex. O2)
- Simple molecules (drugs)
- Water
7
Q
Facilitated diffusion in placenta
A
- Glucose
- *carrier system operates with a chemical gradient
8
Q
Active transport
A
- AA
- Water soluble vitamins
- Na, K, Ca
- *maintain higher concentrations in fetus than in mother
9
Q
Receptor-mediate endocytosis
A
- Immunoglobulins (IgG)
- Protein
- Fat
- Viruses
10
Q
Pig and horse placenta
A
- Diffuse
- Epitheliochorial
11
Q
Diffuse placenta (pig and horse)
A
- chorionic villi located over ENTIRE uterine luminal epithelium
12
Q
Epitheliochorial placenta (pig and horse)
A
- epithelium of chorionic villi and uterine luminal epithelium are intact
13
Q
Porcine placenta
A
- Allantois: mesenchyme and blood vessels
- Chorionic epithelium: trophoblasts
- Endometrium: epithelium and stroma (with uterine glands)
- vessels are very close
- uterine gland empty into AREOLA and taken up by chorion (fetal component)
14
Q
Hemotrophic nutrition
A
- Movement of substances from maternal to fetal circulations via crossing of intervening layers of cells
- Ex. active transport, facilitated diffusion
- *all placentae can achieve this
15
Q
Histotrophic nutrition
A
- Uptake of uterine gland secretions, tissue debris and maternal blood cells via PINOCYTOSIS or ENDOCYTOSIS
- Occurs in varied placentae but especially in EPITHELIOCHORIAL
16
Q
Areolae as sites of histotrophic nutrition
A
- Top is columnar trophoblast capable of:
o ENDOCYTOSIS and PINOCYTOSIS
o Breakdown of absorbed material for transfer to fetal capillaries
17
Q
Examples of nutrients that are taken up in histotrophic nutrition
A
- Proteins
- Uteroferrin: bi-iron protein (acid phosphatase
- Vitamins(ex. placental folate)
- Minerals
18
Q
In between microcotyledons of the mare there are
A
- Areolae
19
Q
Chorionic girdle
A
- First attachment of chorionic epithelium to the uterine epithelium PRIOR to the development of the microcotyledons
20
Q
Endometrial cups in mare
A
- Derived from a narrow band of thick trophoblast that develop around fetus (chorionic girdle)
- Chorionic girdle peels off fetal membranes and trophoblast at d40 and INVADE to form the cups and produce eCG
- Begin to be destroyed at d70 due to maternal immune attack
21
Q
Equine chorionic gonadotropin (eCG) provides stimulus for
A
- Maintenance of primary CL in the ovary formed from primary follicle
22
Q
Gonadotrophins are typically produced in
A
- Pituitary
- *Horses are one species that produces gonadotrophins OUTSIDE of the pituitary (also humans)
23
Q
eCG stimulates formation and maintenance of
A
- Accessory CL that produce more progesterone during pregnancy
24
Q
eCG levels
A
- Detected in mare blood at 38-42 days post ovulation
- Max levels at 60-70 days
- No detection by 150 days
25
eCG has FSH (except in mare) and LH-like activity
- Provides signal for formation of accessory CLs (~40-60days gestation)
- Regulates luteal steroidogenesis
26
eCGs and accessory CLs
- 40% via ovulation
- 60% via luteinization of anovulatory follicles
27
eCG stimulation of primary and accessory CLs
- Increased circulating progesterone and plateaus (50-140days) then decrease
- Low concentrations (180-200days)
- Rapidly increase (300days) for parturition
28
Cow, sheep and goat placenta
- Cotyledonary
- Syn-epitheliochorial
29
Cotyledonary placenta (cow, sheep, goat)
- Chorionic vascularized villous trophoblasts and uterine endometrial structures (CARUNCLES) come together
- **placentomes
30
Syn-epitheliochorial
- Some trophoblast cells fuse together into binucleate giant trophoblast cells (BNGC)
o BNGC migrate into uterine epithelium=fuse with maternal cells into trinucleate giant trophoblast
31
Importance of multinuclear trophoblast secretions (BNGCs)
- Important producers of progesterone, estradiol and placental lactogen
32
Pregnancy-associated glycoprotines (PAGs) also referred to as
- Pregnancy specific protein B (PSP-Bs)
33
PAGs are a group of
- Aspartic proteinases=enzymes that cleave proteins at aspartic residues
34
Functions of PAGs (unclear)
- Process or cleave growth factors and other maternally released factors at trophoblast-uterine interface
35
Dog and cat placenta
- Zonary
- Endotheliochorial
36
Zonary (dog and cat placenta)
- Invasive band of chorion surrounds middle of fetus
37
Endotheliochorial (dog and cat placenta)
- Trophoblasts move through uterine epithelium and stroma
- *in contact with maternal endothelia
- *one layer is absent (endometrial layer has been ‘eroded’)
38
Rat, mice and higher primates placenta
- Discoid
- Hemochorial
39
Discoid placenta (rats, mice, higher primates)
- Disc-like structure of chorion interacting with maternal tissue
40
Hemochorial placenta (rats, mice, higher primates)
- Highly invasive trophoblast pass through the maternal uterine epithelium, stroma, and endothelium of maternal vasculature becomes DIRECTLY in contact with maternal blood
- *only 3 layers (maternal layers have been eroded)
41
Which species can pass on passive immunity through the placenta?
- Primates
- Rodents
- Dogs
- Cats
- **only IgG is transferred via receptor-mediated endocytosis as Fc receptors on trophoblast bind Fc portion of IgG
42
Which species can NOT take up IgG
- Horses
- Pigs
- Ruminants
- *due to their extra layers in the maternal-fetal interface
43
Placentate of all domestic species can produce steroids such as:
- Estrogens
- Progesterone (indispensable for pregnancy)
- *except in dog
44
Species with predominantly luteal P4 synthesis
- Goat
- Pig
- *ONLY way in the dog (can’t produce from placenta)
45
Placental steroidogenesis
1. Cholesterol to pregnenotlone by P450scc
2. Pregnenolone to progesterone by 3beta-HSD (Delta4 pathway: progestogens)
3. Pregnenolone to dehydropiandrosterone to androstenedione
4. Androstenedione to oestrone by P450arom then to oestradiol (Delta 5 pathway: androgens, estrogens)
46
What organelle is able to do steroidogenesis?
- Mitochondria
47
Placental Steroidogenesis: cow and ewe
- take cholesterol and mitochondria breaks it down into progesterone or estrogens
- **IMPORTANCE of the multinucleated cells in the placentae of the ruminants
48
Different estrogens produced by placenta (especially during last part of pregnancy in ungulates)
- Estradiol
- Estrone: major estrogen in ungulates
- Equine specific forms: equilin and equilenin
49
Mares and steroid production
- can NOT make steroids from scratch
- **NEED precursors from fetal gonads (ex. dehydroepiandrosterone)
50
Relaxin
- Small polypeptide hormone of the insulin superfamily
- Produced by a number of tissues with a range of chemical effects between species
- Acts via GPCRs
- Not discovered in ruminants yet
51
Relaxin in mares
- Main secretion by placenta
52
Relaxin in humans, cats, dogs
- Placental AND trophoblast production
53
Relaxin in pigs
- Potent production by CL
- *NOT produced by placenta
