Placenta
- Temporary organ
- Forms when trophoblast forms the chorion(3 layers)
- will develop extensions(villi)
- Transfer of substances between maternal and fetal systems
- forms from two parts , trophoblast and endometrial lining from mom
- villi-to exchange nutrients and waste products
Components of the placenta
- Embryonic(chorion frondosum)
- Maternal(decidua basalis)
- decidua -endometrial lining of uterine cavity
Decidua(maternal component)
- Decidua basalis-portion of endometrium underlying the implantation site
- Decidua capsularis-portion overlying the implanted embryo and separating ti from the uterine cavity
- Covering and capsule over implantation site
- eventually lost as the amnioitic cavity enalrges and occupies all the sapce in the uterine cavity
- Decidua parietalis-the remainder of the endometrium
- these two wil fuse together and they will lose their individuality
- These are areas of the endometrium lining the uterine cavity, but not part of the placenta
- As the baby gets larger the uterine cavity gets lost
- Myometrium-muscle that helps contract and push the baby
Fetal component of the placenta
- Chorion fondosum(chorionic plate)
- area where villi develop(villious chorion)
- VIlli are the agetns of exchange between maternal & fetal systems
- Fetal surface of placenta should have chorionic(fetal) blood vessels
- Going to have to grow into them a set of capillaries because diffusion is not enough
- Chorion villi help make capillaries
Primary chorionic villi
- Solid outgrowths of cytotrophoblast that protrude into the syncytiotrophoblast
- Start out in primary chorioinic villi
- A little bump of cytotrophoblast
Function of chorionic villi
- oxygen and nutrients in the maternal blood in the intervillous spaces diffuse through the walls ov the villi and enter hte fetal capillaries
- Carbon dioxide and waste products diffuse from blood in the fetal capillaries through the walls of the villi the maternal blood in the intervillous spaces
- Need lots of sruface area but thin walls
- cytotrophblast helps keep the capillaries open because you need the nutrients and oxygen
- Get them into the fetal system
- Needs lots of surface area and thin walls when wanting to move tons of different waste products
Secondary chorionic villi
- Have a core of lose connective tissue,which grows into the primary villi about the third week of development
Teritary chorionic villi
- Contain embryonic blood vessels
- These blood vessels connect up with vessels that develop in the chorion and connecting stalk and begin to circulate embryonic blood about the third week of development
- Thin coating of cytotrophoblast and other trophoblast
- now you have blood vessels
- by the end of week three we have built this sytem and can move blood around in the developing embryo
- also have heart now that can beat
- we will become more elaborate as the weeks go on
Placental barrier
- 1.syncytiotrophoblast
- cytotrophoblast
- Extraembryonic mesenchyme
- Fetal endothelium(single layered wall of fetal capillaries)
Placental membrane
- Not a strict barrier
- Variety of substances cross freely
- Beneficial or harmful
- Some substances do not cross
Substances that cross the Placenta
- Beneficial:O2, CO2 glucose free fatty acids, vitamins
- Harmful: rubella,measels , herpes, cytomegalovirus, variclla,poliomyelitis
- Cat D: some antibiotics, Valium, Librium , Xanax, Lithium
- Have been shown to cause congential deffects
- Cat X drugs:thalidomide , warfarin, isotretinoin , nicotine,alcohol, phenytoin
- Thalidomide-disrupts the signaling ,and stops the growth of hte limbs from growing properly
- FAS-worse tetraogens we deal with
- Warfarin
- Coumadin
- Anticoagulant
- Phenytoin
- Antiepileptic
Isotretinoin
- Used to treat severe acne that is resistant to more conservative treatments
- Because of its serious side effects, isotretinoin should be used only for severe resistant acne
- Sotret, Claravis , Amnesteem
Erythroblastosis fetalis(Rh factor)
- Rh-negative mother with Rh-positive fetus will produce antibodies
- First pregnancy unaffected
- Antibodies in 2nd pregnancy with Rh-positive fetus
- Destruction of fetal RBCs
- Brain damage to fetus& severe edema(hydrops fetalis)
- Some of the fetal cells will be left and will develop antibodies for it
- subsequent pregnancis will be problematic and mom’s antibodies will attack the embryo becasue it think it’s a foreign figure
Symptoms in newborn baby for Erythroblastosis fetalis
- Anemia
- Edema(swelling under the surface of the skin)
- Enlarged liver or spleen
- Hydrops(fluid throughout the body’s tissues,inclduing in the spaces containing the lungs, heart, and abdominal organs)
- Newborn jaundice
treatment for erythroblastosis fetalis
- RhoGAM
- Human immunoglogin wiht antibodies against the Rh factor
- prevents maternal antibody response to Rh-positive cells for the fetus
- third trimester or after devlivery ,give her a dose of RhoGAM and it will stop mom’s antibodies from attacking the baby
Chorionic Villus Sampling
- test for familial genetic disorders,advanced maternal age(chromosomal abnormalities)
- Chorionic villlus sampling can be done earlier in pregnancy(at 10 to 12 weeks) than amniocentesis(usually done at 15 to 20 weeks
- You can find out the karotype to determin the genetic health of that child
- Very dangerous proceudre and transabdominal procedure can poke the developing fetus on accident
Umbilical(Placental) vessels
- Wharton’s jelly is a placental cord(umbilical cord) gelatinous connective tissue
- It is seen at parurition when it increases in volume to assist closure of placental blood vessels
- Matrix cells from wharton’s jelly have recently been identified as a potential source of stem cells
- This placental cord substance is named after thomas wharton(1614-1673) an english physician and anatomist who first described it
- vein kinda of functions like an artery
- Wharton’s jelly-gelantinous viscousconnective tissue
- increases in volume irhgt before birth
- helps squeeze down the lumen and helps the vessel collapse
- a place where you can get stem cell, and don’t have to interact with embryo blast
Why is htere one umbilical vein?
- During development ,there are two umbilical veins that drain blood from the placenta to the heart
- Right umbilical vein regresses and under normal circumstances is completely obliterated during the second month development
- Left umbilical vein persists and delivers blood from the placenta to the developing fetus
Persisten right umbilical vein
- PRUV is an uncommon anomaly
- Present in 2~1000 briths
- Normally the right umbilical vein begins to obliterate in the 4th week of gestation and disappears by the 7th week
Velamentous cord
- Virtually unprotected for long periods of teim, and easier to get a knot into this
- Easier for damage to occur at child birth
- Doesn’t mean you can’t do a vagina lbrith just need to watch babie’s heart rate and oxygen
If the placent is unstable then go for C section
- Fetal blood vessels travel abnormally
- Pass through amniochorionic membrane before reaching the placenta
- These vessels are more exposed to trauma during the birth process
Placenta Previa
- Implantation of the placenta over the cervical os(opening)
- covers internal opening of cervix(os)
- a low-lying placenta is near the cervical opening but not covering it
- partial placenta previa covers part of hte cervical oepning
- total placenta previa covers and blocks the cervical opening
Placenta Accreta
- Abnormal trophoblastic invasion into the muscular layer of the uterus(placenta increta) or through the uterine wall and into surrounding tissues(placenta percerta)
- Placenta accreta-the placental roots grow too deeply into the muscular wall of the uterus
- Placenta increta-the placenta invades through the muscle of the uterus
- Placenta percreta-the placenta pushes through the uterine wall and invades into other organs, like the bladder
- Run into the same problems with ectopic pregnancy and no mechanism to shut off blood supply
- hope to reabsorb and do a C section
- Run into the same problems with ectopic pregnancy and no mechanism to shut off blood supply
Placenta as an Endocrine Organ
- Synthesizes glycogen, cholesterol and fatty acids
- Nutrients,oxygen some immunoglboulins
- remove waste products
- synthesis and release of hormones
- Most synthesized in the syncytiotrophoblast
- human chorionic gonadotropin(hCG)-stimulates production of progesterone by the ovary(corpus luteum)
- Chorionic somatomammotropin
- aka human placental lactogen(hPL)
- induces lipolysis, elevating free fatty acids in mother
- “growth hormone” of the fetus
Progesterone
- Steroid hormone that maintains the endometrial lining during pregnancy also suppresses contractility in uterine smooth muscle
Estrogens
- Steroid hormones, stimulate mammary gland development
Placental calcification
- Calcification is a sign of placental aging
- The pattern of calcification(precipitation of calcium hydroxyapatite) is similar to that seen in other aging tissues
- Probably a response to cell death and diminshed blood circulation in localized regions of the placenta
- one significant risk ractor-smoking
Lithopedion
- Fetal death with an ectopic pregnancy(usually)
- The fetus is too large to be reabsorbed by the body and calcifies
Functions of Amniotic Fluid
- Permits symmetrical external growth
- Enables fetus to move freely
- Acts as a barrier to infection
- Permits normal fetal lung development
- Prevents adherence of amnion to embryo/fetus
- Helps maintain homeostais
- lets baby grow symetrically
- make sure it gets right temperature , electrolytes
- helps the lung expans and pracitice breathing
Ligohydramnios
- Low volume of amniotic fluid
- associated with renal agenesis & obstructive uropathy
- complications-pulmonary hypoplasia & limb defects
- too little amniotic fluid, if you dont’ have enough the major tissues are renal agenesis is bad(where kidney’s dont form)
- If potter syndrome-the failures of the kidney to develop, if you dont have kidney’s can’t supplement the amnioitic fluid
- Fetal compression and not enough fluids can’t move around
- Pulmonary hypoplasia-not enough fluid in there for the fetus to pracitice breathing and the lungs to devlop normally (usually kills the kid)
Potter syndrome
- PUlmonary hypoplasia-for normla development amniotic fluid must be brought into lung by fetal breathing movements ,leading to distension of the developing lung
Polyhydramnios
- High volume of amniotic fluid
- Associated with CNS anomalies & esophageal atresia
- What babies do to decrease amniotic fluid and practice swallowing
- Goes to the GI tract to get processess and helps keep it in normal range
- baby is trying to swallow and odens’t get through
- Baby can’t swallow
- Get a huge overgrowth of epithilium and doesn’t reopen and baby has problems swallowing and can’t get through the esophagus
- if it’s in the dueodenum can process some of it
- Can fix this problem relatively easy, if somethign wrong with the brain a lot more serious
Amniotic band syndrome
- Tears in the amnion detach and surround fetus
- or adhesions between the amnion and affected strcutrues
- May cause ring constrictions or amputations of limbs or digits
- Shouldn’t have tears in the membrane
- Get pieces of the amniotic membrane that warp around the limb
- when it deos that you get constrictions in developing limbs, can get amputations depending on constriction
Vasculogenesis
- Blood vessels arise from coalescence of hemangioblasts which arise from blood isalnds
- major vessels form via this way
- Early in development it starts off in the yolk sac
- gets little clumps of mengioblast which develops into vessels
- Once we have enough fetal development we transfer it to the embryo
Angiogenesis
- Vessel formation via branches arising from exisiting vessels
- smaller ones from via angiogenesis
Definitive hematopoietic stem
- Formation of blood cells in the yolk sac is transitory
- Definitive hematopoietic cells arise from mesoderm around the aorta
- Aorta-gonad-mesonephros region(AGM)
- These cells will colonize the liver
- The are in the fetus that will take over the development of red white blood cells
- Eventually it will move out of hte AGM and go into the liver
- 7 months into development, bone marrow takes over and the major site of the development of blood cells
Hematopoietic tissue in the fetus
- Stem cels colonize the liver- major hemaopoietic organ of the fetus
- Later stem cells from the liver colonize the spleen, thymus and ultimately the bone marrow