The embryo is referred to as a fetus after 8 weeks of gestation.
The growing fetus' specialized circulatory system does:
a. receives oxygen directly from its mother
b. supplies nutrients to the fetus
c. removes carbon dioxide and metabolic wastes
d. all the above.
All the above!
The two components of the fetus' specialized circulatory system :
2. umbilical cord
The placenta and umbilical cord are outgrowths of the four extra embryonic membranes formed during development:
4. yolk sac
__________ acts as a shock absorber of external and localized pressure from the uterine contractions during labor
During fetal development, the ___________ lies next to the shell and carries out gas exchange.
Durin fetal development, the _______________ collects nitrogenous wastes.
During fetal development, the _______________ provides nourishment to the fetus.
The chorion, amnion, allantois, and yolk sac are also known as _________________.
Extra-embryonic membranes - develop from extensions of the germ layers.
Found in humans and chicks.
During fetal development, the ________________ become closely associated with endometrial cells, developing into the spongy tissue of the placenta.
The blood vessels of the allantoic wall enlarge and become the _________________.
Umbilical vessels : connect the fetus to the developing placenta.
At some point during fetal development, the ___________ and the ____________ are enveloped by the amnion, forming the primitive umbilical cord.
Allantois and yolk sac
The _______________ is the site of nutrition, respiration, and waste disposal for the fetus.
___________________ are able to diffuse across maternal capillaries into fetal blood.
C. Amino Acids
E. Inorganic salts
F. all the above
all the above
Fetal hemoglobin (Hb-F) has __________ affinity for oxygen than does adult hemoglobin (Hb-A).
_________________________ diffuse in the opposite direction --- from fetal blood into maternal blood.
Metabolic wastes and carbon dioxide
Circulatory system of mother and fetus are not directly connected.
*Maternal blood and fetal blood do not mix!
Material between maternal and fetal blood vessels occurs in the placenta via ______________.
In addition to nutritive and respiratory functions, the placenta offers the fetus some immunological protection by preventing the diffusion of foreign material/bacteria.
Placenta is permeable to _____________.
C. alcohol, drugs
d. both B and C.
Both B and C
The placenta also functions as an _______________, by producing hormones.
The placenta produces hormones such as
3. human chorionic gonadotropin (HCG)
The presence of ___________________ in urine is the simplest test for pregnancy.
HCG - human chorionic gonadtropin
The major difference in fetal circulation is that, blood is oxygenated in the ____________, while in adults the blood is oxygenated in the lungs.
*This is because fetal lungs do not become functional until after birth.
The fetal circulatory route contains 3 shunts that divert blood flow away from the developing fetal liver and lungs.
1. ductus venosus
2. foramen ovale
3. ductus arteriosus
The ______________ carries oygenated blood from the placenta to the fetus.
In fetal circulation, the blood bypasses the fetal liver by way of a shunt called the __________________, before converging with the inferior vena cava
*Since the oxygenated blood from the umbilical vein mixes with the deoxygenated blood of the venae cavae, the blood entering the right atrium is only partially oxygenated.
In fetal circulation, blood bypasses the pulmonary circulation and enters the left atrium directly from the right atrium by way of the ___________________, a shunt that diverts blood away from the pulmonary arteries.
In fetal circulation, the remaining blood in the right atrium empties into the right ventricle and is pumped into the pulmonary artery. Most of this blood is shunted directly from the pulmonary artery to the aorta via the ____________________.
Ductus Arteriosus- monary arteries carry
In the fetus, the pulmonary arteries are partially oxygenated to the lungs.
Deoxygenated blood is returned to the placenta via _________________.
Which arteries are the only arteries that carry deoxygenated blood?
Fetal umbilical artery and adult pulmonary arteries.
Which veins are the only veins that transport oxygenated blood?
Fetal umbilical vein
Adult pulmonary vein
Human pregnancy, or _______________, is approximately 9 months.
Gestation: First Trimester: 8 weeks
major organs begin to develop:
eyes, gonads, limb, and liver start to form
still an embryo in the beginning of the trimester
cartilaginous skeleton begins to turn into bone by the 7th week
by the 8th week, most organs have formed
brain is fairly developed
embryo is referred to as a fetus
Gestation: Second Trimester
fetus does a tremendous amount of growing
moves around amniotic fluid
face appears human
toes and fingers elongate
Gestation: Third Trimester
continued rapid growth and further brain development
*antibodies are transported by highly selective transport from the mother to fetus
growth rate slows as the fetus becomes less active, as it has less room to move about
After birth, a number of changes occur in the circulatory system of the fetus:
lungs expand with air and rhythmic breathing begins
resistance in the pulmonary blood vessels decreases- causes an increase in blood flow through the lungs
umbilical blood flow stops
blood pressure in the inferior vena cava decreases - causing a decrease in pressure in the right atrium
left atrial pressure increases due to the increased blood flow from the lungs
increased left atrial pressure coupled with decreased right atrial pressure causes the foramen ovale to close
ductus arteriosus constricts and later closes permanently.
ductus venosus - degenerates over time, completely closing in most infants 3 months after birth.