Placenta Lecture Powerpoint Flashcards
Cotyledons
Invaginations and folds that attach the placenta to the maternal wall, houses villi and membrane where exchange from spiral arteries of the uterus to the umbilical vein occurs, can be left behind in the uterus upon delivery
Fetal maternal communication of circulatoin
There is no commingling of maternal and fetal blood in a healthy pregnancy, always separated in theory
Pre-implantation genetic screening
Culturing of a blastocyst in a petri dish incubated followed by PCR to determine the genetic karyotyping (if its aneupleudy then won’t successfully thrive but if euploidy then implantable) where implanting has led to increased success of in vitro fertilization
Zona pellucida
Wall that is penetrated by sperm enzymatically, remains intact and disappears just before implantation
Fertilization takes place in the….
Implantation occurs in the…
….fallopian tube
….upper posterior wall of the uterus
A pregnancy is undetectable until
8-10 days post conception (when it implants in the uterus and begins secreting hCG, undetectable before)
Chorionic villi
Tufts of capillaries coming from the trophoblast developing on day 12 from fertilization, fetal blood vessels are functional with circulation established on day 19-21
Spiral arteries of the uterus conversion (Vascular invasion of decidual cells) mech of action
- Trophoblasts invade maternal capillaries and destroy arterioles and spinal arteries vessels walls
- uterine tissue replaced with placental tissue, maternal smooth muscle replaced by SMOOTH MUSCLE LACKING cytotrophoblastic cells
- maternal veins not evolved
- Not autoregulated flow and spiral arteries converted to lacunae (lakes of blood) by becoming very dilated and causing maternal blood to enter in fountain like spurts engorging the area right outside the umbilical artery and vein capillaries, this flow is continuous until uterine contraction pressure limits it (no autoregulation)
No matter what the mother’s blood sugar is, the baby’s is…
…higher
Placental sequestration
The placenta sequesters zinc, copper, lead, and cadmium and other heavy metals, if in a poor developmental environment the baby can be born with toxic levels
Do drugs and metabolites cross the placenta?
Yes, by diffusion (almost 10% of neonates are born addicted to substances)
hCG is found in excessively high levels in these 3 conditions, and lower in these 2
- multiple pregnancies
- fetuses with anti-D rH disease
- down syndrome
- ectopic pregnancy
- impending abortion
Amniotic fluid
Bound by the amnion, fluid that bathes the fetus detectable by 1st trimester as it diffuses into the amnion, 85% fetal urine, swallowed and absorbed into the fetal blood stream, diffuses across placental membrane back into the maternal space, excreted by kidneys and lungs of mother
Umbilical vein
Carries o2 RICH blood from placenta to fetus that then bipasses the liver and into the right atria via the ductus venosus
There are __ umbilical arteries (oxygen poor blood) and __ umbilical veins
2, 1
Ligamentum teres
Remnant of the umbilical vein, free edge of the falciform ligament of the liver
Placenta previa
Accreta
Increta
Percreta
- Occurs when the placenta implants over the cervical opening
- placenta implants in the decidua basalis
- placenta implants into the myometrium
- placenta implants into the serosal surface of the uterus or into bladder wall
Mechanism of shifting from utero to newborn breath
- aeration of lungs causes them to inflate
- sees a dramatic fall in pulmonary vascular resistance and marked increase pulmonary blood flow causing pressure on right side of heart to decrease
- systolic systemic BP is about 75-80 mmHg, and pulmonary drops from 1/2 that to about 1/3rd, the foramen ovale and ligamentum arteriosum close by 1 year and 24 hours of this, respectively
Risk factors for abnormal placental implantation (6)
- previa
- older mothers
- higher parity
- prior cesareans
- uterine scarring from ablation
- leiomyomas
Complications of abnormal placental implantation (4)
- post partum hemorrahge***
- damage to bladder and bowels
- transfusion reactions
- ARDS
The amnion
Innermost fetal membrane contiguous with amniotic fluid, avascular but metabolically active, provides tensile strength of fetal membranes
Less than __mL at term is oligohydramnios, greater than __L is polyhydramnios, avg is ___mL
100ml, 2L, 1000mL
Umbillical cord
Originated from the yolk sac, average length of 55cm, normal range 30-100cm, houses 2 arteries and 1 vein
Amniotic bands syndrome
Rare malformation of the amnion and chorion that causes constricting of the tissue instead of a clear sac and can potentially strangulate extremities
“I think I might be pregnant, my last period was 3 weeks ago, would the pregnancy test be positive?”
No it would be negative
Thyroid hormone values in pregnancy, what is the active form of thyroid hormone?
- Free T3 and T4 decreased
- T3
Bacteruria levels in nonpregnant vs pregnant indicating infection
Nonpreg >100,000 colonies/mL
Preg >10,000 colonies/mL
Placental transfer methods (3)
- diffusion primarily (O2)
- facilitated transport (fetus spends energy to take up sugar and such)
- Maternal blood has higher affinity for CO2 than fetal blood drawing it out
hCG alpha and beta subunits
alpha is identical to TSH FSH and LH
Beta is unique
Ductus venosus
Fetal shunt from the umbilical vein bipassing the liver directly to the inferior vena cava
Foramen ovale
Right atrial opening into the left atrium to bypass pulmonary circulation
Ductus arteriosus
Opning to descending aorta from pulmonary arteries to bypass pulmonary circulation and return blood to the placenta from the umbilical arteries (division of anterior iliac in systemic circulation)
Ductus venosus
Branch off the umbilical vein that bipasses the liver bringing blood direclty to the inferior vena cava, becoming the ligamentum venosum after birth
Chorioamnion
Outer layer up against uterine uterine wall as placenta grows, not as strong as amnion, can be site of infection of meconium stanining
