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The Reproductive System > Lecture 7.2: Foetal Physiology > Flashcards

Lecture 7.2: Foetal Physiology Flashcards

1
Q

How does placenta connect to and from the foetus?

A

Umbilical Chord

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2
Q

What embryonic layer is placenta derived from?

A

Trophoblast

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3
Q

Roles of the Placenta (4)

A
  • Nutrition
  • Gas Exchange
  • Waste Removal
  • Source of hematopoietic stem cells, endocrine and
    immune support
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4
Q

What Hormones does the Placenta produce? (7)

A
  • HCG
  • HPL
  • Oestrogen
  • Progesterone
  • Thyrotropin
  • Corticotropin
  • Relaxin
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5
Q

What is the diameter, thickness and weight of the Placenta?

A
  • 20cm in diameter
  • 2.5cm thick
  • Average weight of 600g
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6
Q

What are the 2 surfaces of the Placenta?

A
  • Maternal surface, attached to the uterine wall
  • Foetal surface, facing towards the amniotic cavity
    within which is the foetus
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7
Q

What is the Decidua?

A

It is the uterine lining during pregnancy. In the non-pregnant uterus the decidua is known as the endometrium

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8
Q

The portion of the decidua associated with the placenta is called the….?

A

Decidua basalis/placentalis

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9
Q

What is the length and width of the umbilical chord?

A
  • 50 to 60 cm long
  • Width of 2 to 3 cm
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10
Q

What does the umbilical cord contain? (4)

A
  • 2 arteries carrying deoxygenated blood
  • 1 umbilical vein carrying oxygenated blood back to the
    baby
  • Which are surrounded by Wharton’s jelly
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11
Q

Shape of Umbilical Chord

A
  • These vessels are longer then the cord
  • Tend to twist and spiral to add strength and protect
    against entanglement, compression and tension
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12
Q

Foetal umbilical pO2 must be …. than maternal pO2

A

lower

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13
Q

Uterine blood flow can be influenced by? (4)

A
  • Maternal Blood Pressure
  • Medication
  • Uterine Contractions
  • Hormones
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14
Q

Foetal Hb dissociation curve is to the left of adult Hb, what does this mean?

A

Higher affinity for oxygen

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15
Q

Foetal Hb has lower affinity for …… which results in higher O2 affinity

A

2,3 DPG

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16
Q

CO2 passively diffuses from foetal to maternal side, this results in ….?

A

Local acidosis

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17
Q

What is the effect of local acidosis?

A
  • Reduces the oxygen affinity of maternal Hb and
    oxygen is released to the diffuse to the foetal side and
    to the foetal Hb
  • This is the Bohr effect
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18
Q

Foetal Umbilical Vein carries oxygenated blood from the
placenta to the foetus at what saturation?

A

70%

19
Q

Foetal Blood Flow: Umbilical Vein to Heart (6 Steps)

A
  • The foetal Umbilical Vein carries oxygenated blood.
    placenta to the fetus
  • The Ductus Venosus receives oxygenated blood from
    the umbilical vein
  • Directs it to the inferior vena cava and then to the
    RA, open ductus venosus acts to bypass the liver
  • The oxygenated blood goes from IVC into the R-atrium
  • Oxygenated Blood flows from right atrium through the
    foramen ovale to the left atrium, thus oxygenated
    blood bypasses the lungs
  • The oxygenated blood goes from LA to LV and then
    aorta to the brain and upper limbs at about 60%
    saturated
20
Q

Foetal Blood Flow: Brain back to Heart (6 Steps)

A
  • Blood Returns from head/brain/upper limbs in the SVC
    at 30% saturated
  • From SVC the blood goes to RA and mixes with a little
    oxygenated blood (from IVC) in RA and so passes from
    RA to RV at 50% saturated
  • The blood goes from RV to Pulmonary Artery, but 4/5
    of this blood goes to the ductus arteriosus (bypasses
    lungs)
  • Then goes to the arch of Aorta distal to the origin of
    the left subclavian artery
  • Then down the descending aorta, supplying bowel,
    kidneys and lower limbs and also to the internal iliac
    arteries to the two umbilical arteries back to the
    placenta
  • Some mixing occurs at ductus arteriosus and in the
    descending Aorta blood is 60% saturated
21
Q

What structures are visible on the maternal surface of the placenta?

A
  • 15 to 20 polygonal cotyledons, each with 10 to 20
    lobules
  • They are divided by deep septae of the decidua which
    also divides up the intervillous space
22
Q

What form pools of maternal blood in intervillous spaces?

A

c.200 Branches of the maternal uterine arteries enter each lobule of the space between the chorionic and decidual plates

23
Q

What is the foetal surface of the placenta covered in?

A

Covered by the shiny amniotic membrane

24
Q

The chorionic plate is made up of…?

A

The amnion and chorion and forms the boundary of the foetal portion of the placenta

25
Q

What plate forms the boundary of the maternal side of the placenta?

A

The decidual plate

26
Q

What lies between the chorionic and decidual plate?

A

Intervillous spaces

27
Q

What is in the intervillous space?

A

Lakes/lacunae of maternal blood

28
Q

What from the foetus grow into the intervillous lakes of maternal blood?

A

The arborescent fetal villous trees

29
Q

Should there be direct contact/connection between the foetal and maternal circulations?

A

No

30
Q

What stimulates the the baby to breath in once it’s born?

A

Physical, thermal and chemical stimuli that occur just prior and during birth

31
Q

Why does the foramen ovale close after the baby takes its first breath? (5)

A
  • The lungs inflate, fill with air and are quickly emptied of
    fluid
  • This causes a decrease in pulmonary vascular
    resistance allowing greater pulmonary blood flow and
    oxygenation
  • Therefore an increase in oxygen tension
  • The increased pulmonary blood flow and pulmonary
    venous return leads to increase in left atrial pressure
  • Causing the foramen ovale to close
32
Q

What causes the ductus arteriosus to close soon after birth?

A

Response to increased oxygen tension and reduced prostaglandins (metabolised in pulmonary circulation)

33
Q

What causes the ductus venosus to close soon after birth?

A

The umbilical cord is cut, the arteries go into spasm and the blood flow in the umbilical vein stops and the ductus venosus closes

34
Q

What does the Foramen Ovale become?

A

Fossa ovalis

35
Q

What does the ductus arteriosus become?

A

Ligamentum arteriosum

36
Q

What does the ductus venosus become?

A

Ligamentum venosum

37
Q

What does the umbilical vein become?

A

Ligamentum teres

38
Q

What do the umbilical arteries become? (2)

A
  • Medial umbilical ligaments
  • Superior vesicle arteries to bladder
39
Q

What cells produce Surfactant?

A

Alveolar type II cells/Pneumocytes

40
Q

Surfactant production begins from week….?

A

24

41
Q

What does surfactant do in the newborns lungs?

A

Reduces surface tension at the air-fluid interface on the surface of the alveoli allowing the alveoli to open easily and also stops the alveoli from collapsing. Therefore, the work of breathing is reduced.

42
Q

Earlier production of surfactant can occur as a result of..?

A

“Stress” such as an event(s) that may be leading to premature delivery

43
Q

Administration of …… to a mother with threatened premature delivery is very useful in increasing foetal surfactant production

A

Steroids

The Reproductive System (19 decks)

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