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MSc foetus exam > fetal and placental physiology - finished cards > Flashcards

fetal and placental physiology - finished cards Flashcards

1
Q

what is fetal growth and development dependant on?

A

Dependent on adequate transfer of nutrients and O2 across the placenta

Placental development is dependent on adequate maternal nutrition and uterine perfusion.

Fetal hormones have an important role in fetal development they affect the metabolic rate, growth of tissues and maturation of individual organs.

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2
Q

what does IGF, insulin and thyroxine do in growth and development of fetus?

A

IGFs co-ordinate a precise and orderly increase in growth through late gestation.
Insulin and thyroxine are required through late gestation to ensure appropriate growth in normal and adverse nutritional circumstances
Fetal hyperinsulinemia as in DM results in macrosomia due excessive fat deposition, while in growth restricted fetuses fetal insulin levels are low

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3
Q

when is fetal growth slow and fast?

A

Fetal growth is slow up to week ~20, accelerates to reach a peak at weeks 30–36 and then slows again. (There is also a postnatal growth peak at week 8).

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4
Q

what is fetal growth determined by?

A

Growth is primarily determined by the fetal genome; IGFs are an important mediator.

Fetal thyroid hormones stimulate growth in late pregnancy. The fetus makes GH but it is not effective in stimulating fetal growth.

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5
Q

what maternal factors can affect growth of fetus?

A 
maternal factors are clearly significant 
nutrition 
health 
parity (first babies are smaller)
smoking
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6
Q

what happens to volume of amniotic fluid levels during pregnancy?

A

Amniotic fluid volume increases until week 34, then declines

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7
Q

what happens to placental size during pregnancy?

A

Placental size increases steadily (although the fetus grows faster, so the placental:fetal weight ratio falls).

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8
Q

what happens to fetus if there is a lack of thyroid hormone during pregnancy?

A

Lack in thyroid hormone produces deficiency in skeletal and cerebral maturation (cretinism), also there is delayed surfactant production.

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9
Q

what is cortisol needed for in the fetus?

A

1-lung compliance and surfactant release, which ensure that spontaneous breathing can occur at birth.
2-in the fetal liver , it induces beta receptor and glycogen deposition to maintain a glucose supply to the neonate after delivery.
3- in the gut it is responsible for villus proliferation and induction of digestive enzymes, which enable the neonate to switch to enteral feeding after birth.

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10
Q

what is the average birth weight at the end of normal pregnancy?

A

3.5kg

1/3 of the eventual birth weight is reached by 28 wk
1⁄2 by 31 wk
2/3 by 34 wk.

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11
Q

Each baby has its own optimal growth potential, which is predictable from physiological characteristics known at the beginning of pregnancy; those factors are:

A

Pre-pregnancy weight and maternal booking weight (increasing with maternal weight).
Maternal height (increasing with maternal height) .
Maternal age and parity increased with mother >para2.
Ethnic group (low in South Asian and Afro-Caribbean).
Fetal sex (male > female) .
Paternal height.

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12
Q

how is the fetal circulation different from adult circulation?

A

1-oxygenation occurs in the placenta not in the lung.
2-the right and left ventricles work in parallel rather than in series.
3-the heart ,brain and the upper body receive blood from the left ventricle , while the placenta and lower body receive blood from both right and left ventricles.

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13
Q

There are modifications in fetal vascularity that ensure that the best , oxygenated blood from the placenta is delivered to the fetal brain, these are:

A

1- the ductus venosus (DV) that shunts blood away from the liver.
2-the foramen ovale, shunts blood from right to left atrium. (trie to bypass the right pumping chamber - so less blood is going to the lungs.
3-the ductus arteriosus (DA) that shunts blood from the pulmonary artery to the aorta - so less blood goes to lungs and more to the body

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14
Q

what does oxygenated blood from the placenta return to the fetus through?

A

the umbilical vein

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15
Q

what two main branches does the umbilical vein divide into?

A

1- One supplies the portal vein in the liver.
2- The DV which joins the inferior vena cava (IVC) as it enters the right atrium.

50% of oxygenated blood will pass to the portal system and 50% will pass to the DV

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16
Q

how do the ductus venous and the foramen ovale work to bypass the lungs?

A

The ductus is a narrow vessel and a high blood velocities are generated within it.
The streaming of DV blood , together with a membranous valve in the right atrium ( the crista dividens), prevents mixing of the well- oxygenated blood from the DV with the desaturated blood of the IVC
The DV stream passes across the right atrium through a physiological defect in the atrial septum (foramen ovale) to the left atrium, then the blood will pass to the left ventricle through the mitral valve and hence to the aorta.

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17
Q

how does the ductus arteriosus remain patent and how do the DV and DA close at birth?

A

Prior to birth, the DA remains patent due to production of the prostaglandin E2 and prostacyclin which act as local vasodilators,
• Administration of cyclo-oxygenase inhibitor will lead to premature closure of the ductus.
• At birth ,the cessation of umbilical blood flow causes cessation of flow in the ductus venosus , a fall in the right atrium pressure and closure of the foramen ovale.
• Ventilation of the lungs opens the pulmonary circulation, with rapid fall in pulmonary vascular resistance.
• The DA closes functionally within a few days of birth

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18
Q

what is persistent fetal circulation?

A

Occurs when there is delayed closure of the DA after birth because the
pulmonary vascular resistance fails to fall despite adequate breathing.
• Results in left to right shunting of blood from the aorta through the DA to the lung.
• The baby remains cyanosed and can suffer from life threatening hypoxia.
• This is mostly occur in premature infants.
• Result in congestion in the pulmonary circulation and reduction in the blood flow to the gastrointestinal tract and brain, that lead to necrotizing enterocolitis and intraventricular haemorrahge.

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19
Q

what is the development of respiratory system at 20 week and 24 weeks?

A

By 20 wk gestation full differentiation of capillary and canalicular elements of the fetal lung is apparent, but alveoli develop after 24wk.

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20
Q

what is needed for necessary lung maturation?

A

Adequate amniotic fluid volume is necessary for lung maturation.

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21
Q

what is the fetal lung filled with?

A

The fetal lung is filled with fluid, the production of this fluid starts from early gestation and ends in the early stages of labour.
At birth the production of this fluid must cease and the fluid present is absorbed, adrenaline play a major role in this process

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22
Q

what are lung alveoli lined by?

A

Lung alveoli are lined by a group of phospholipids known collectively as surfactant that prevents the collapse of small alveoli during expiration by lowering surface tension.

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23
Q

where is surfactant continually produced from?

A

The surfactant is continually produced from type 2 alveolar cell (10% of the lung parenchyma), maximum production will be after 28 wk.

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24
Q

what is the predominant phospholipid that lines the lung?

A

The predominant phospholipid( about 80% of total) is phosphotidylcholine (lecithin); and it’s production is enhanced by cortisol, growth retardation and prolonged rupture of membrane; and is delayed in diabetes.

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25
Q

what is phosphoatidylglycerol?

A

Phosphoatidylglycerol is another type of potent phospholipid that is present in the amniotic fluid ,and it is more predictive of respiratory distress syndrome especially in diabetic preganat women.

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26
Q

what to things can result in pulmonary hypoplasia?

A

Oligohydramnios and reduced intrathoracic space (daiphragmatic hernia) or chest wall deformities can result in pulmonary hypoplasia, which lead to progressive respiratory failure from birth.

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27
Q

what is associated with respiratory distress syndrome in premature babies?

A

Respiratory distress syndrome (RDS)is specific to babies born prematurely and is associated with surfactant deficiency.

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28
Q

What is respiratory distress syndrome complicated by?

A

RDS may be complicated by hypoxia , intraventricular haemorraghe and necrotizing enterocolitis .

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29
Q

what can reduce the incidence and severity of RDS?

A

The incidence and severity of RDS can be reduced by administrating steroids antenatally to mothers at risk of preterm delivery

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30
Q

where and when are the first fetal blood cells formed?

A

The first fetal blood cells are formed on the surface of the yolk sac from 14 to 19 days after conception

Haemopoiesis from the yolk sac continues until the 3rd post- conceptional month.

During the 5th wk of embryonic life extramedullary haemopoiesis begins in the liver and to a lesser extent in the spleen.

The bone marrow starts to produce red blood cells at 7-8 wk and is the predominant source of red cell from 26 wk of gestation.

Most haemoglobin in the fetus is the fetal haemoglobin (HbF) that has 2 gamma chains (2 alpha , 2 gamma).

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31
Q

where and when are the first fetal blood cells formed?

A

The first fetal blood cells are formed on the surface of the yolk sac from 14 to 19 days after conception

Haemopoiesis from the yolk sac continues until the 3rd post- conceptional month.

During the 5th wk of embryonic life extramedullary haemopoiesis begins in the liver and to a lesser extent in the spleen.

The bone marrow starts to produce red blood cells at 7-8 wk and is the predominant source of red cell from 26 wk of gestation.

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32
Q

what kind of haemoglobin is in the fetus

A

Most haemoglobin in the fetus is the fetal haemoglobin (HbF) that has 2 gamma chains (2 alpha , 2 gamma).

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33
Q

what is adult Hb?

A

While the adult Hb is composed from HbA (2 alpha, 2 beta) chains and HbA2 (2 alpha, 2 delta) chains.

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34
Q

when does a switch from fetal to adult Hb occur?

A

90% of fetal Hb is HbF from 10 to 28 wk.
From 28-34 wk a switch to HbA occurs.
At term the ratio of HbF to HbA is 80:20, by 6th month of age only 1% of the Hb is HbF.

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35
Q

what is the difference between adult and fetal Hb?

A

The HbF had high affinity for oxygen than HbA.

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36
Q

what enhances transfer of oxygen across the placenta?

A

higher Hb concentration

fetal Hb has a higher affinity for oxygen.

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37
Q

what will beta major thalassaemia without treatment result in?

A
  • Severe anemia,
  • Fetal growth restriction,
  • Poor musculoskeletal development and
  • Skin pigmentation due to increased iron absorption.
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38
Q

what will alpha thalassaemia major result in?

A
  • Severe fetal anemia with cardiac failure,
  • Hepatoseplenomegaly & generalized oedema,
  • Infants are stillborn or shortly die after birth.
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39
Q

why does the fetus require an immune system?

A

The fetus requires an effective immune system to resist intrauterine and perinatal infections.

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40
Q

when do lymphocytes appear in the fetus?

A

8 weeks

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41
Q

what cells will be available by middle of the second trimester to mount a response?

A

By the middle of the second trimester all phagocytic cell, T and B cells and the complements are available to mount a response.

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42
Q

what can affect the immune system?

A

Early infections with any of the TORCH organisms will affect the immune system

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43
Q

Where are IgG, IgM and IgA produced and can they cross the placenta?

A 
Immunoglobulin g (IgG) originates mostly from maternal circulation and crosses the placenta to provide passive immunity.
The fetus normally produces a small amount of IgM and IgA, which don’t cross the placenta.
44
Q

what is indicative of fetal infection in the new born?

A

Detection of IgM& IgA in the newborn without IgG is indicative of fetal infection.

45
Q

what are general immunological defences in fetus?

A
  • The amniotic fluid (lysosymes,IgG ).
  • The placenta (lymphoid cells, phagocytes, barrier ). -Granulocytes from liver and bone marrow . -Interferon from lymphocytes
46
Q

what affect does fetal skin have on homeostasis?

A

Fetal skin protects and facilitates homeostasis.

47
Q

what happens to the thickness of the skin during pregnancy?

A

The thickness of the skin increase progressively from the 1st month of gestation until birth.

48
Q

when doe the stratum corner form?

A

A stratum corneum forms in the 5th month and after 23 wks the appearance of the skin approaches that the adult epidermis.

49
Q

what is the vernix?

A

Vernix ( consisting of desequemated skin cells, cholesterol and glycogen) is covering the skin of fetus in the last wks.
Preterm infants have no vernix and thin skin, this allows a proportionately large amount of insensible water loss.

50
Q

when are the primitive forget and hindgut present by?

A

The primitive forgut and hindgut are present by the end of 4th wk as a straight tube suspended by the mesentery from the dorsal body wall.

51
Q

when doe the midgut herniate into the base of the umbilical cord?

A

The midgut is herniated into the base of the umbilical cord during the 6th wk because the abdominal cavity is too small to accommodate the enlarging liver & intestine.

52
Q

what happens to the gut during the 12th week?

A

By 12th wk the gut will re-enter the abdominal cavity but prior to that the gut undergoes rotation.
Failure of the re-entry results in the development of abdominal wall defects like omphalocele or gastroschisis.

53
Q

swallowing reface in the fetus?

A
  • The swallowing reflex develops and matures gradually.
  • The fetus continually and increasingly swallow amniotic fluid up to 20 ml/hr at term .
  • A failure in the swallowing mechanism as in neurological abnormalities e.g. anencephaly or an obstruction of the gut e.g. atresia of the oesophagus will result in polyhydramnios.
54
Q

when does peristalsis in the intestine occur?

A

Peristalsis in the intestine occurs from the 2nd trimester.

55
Q

what is the large bowel filled with?

A

The large bowel is filled with the meconium

56
Q

what is a sign of post maturity and fetal hypoxia?

A

meconium stained liquor is a sing of post maturity and fetal hypoxia.

57
Q

when doe the glycogen and fat stores increase in the fetus?

A

Body water content gradually diminishes and the glycogen and fat stores increase about 5 fold in the last trimester.

Preterm infants and growth restricted fetuses have reduced glycogen and fat stores.

58
Q

when does the primitive liver appear in the developing fetus?
what happens to it on the 25th day?

A

The primitive liver appears at about 18th day of embryonic life as a diverticulum arising from the duodenum.
By the 25th day it has developed into a T shaped outgrowth which is invaded by blood vessels.

59
Q

what gives rise to the hepatic ducts and gallbladder

A

The large portion of this diverticulum gives rise to the parenchymal cells and the hepatic ducts, while the small portion gives rise to the gallbladder.

60
Q

when does the liver play a role in haemopoiesis?

A

The liver plays an important in haemopoiesis starts from 6th wk and peaks at 12-16th wks and continues until 36th wk.

61
Q

how is the fetal liver and adult liver different?

A

Fetal liver differs from adult in that it has reduced ability to conjugate bilirubin because of relative deficiencies in necessary enzymes like glucuronyl transferase .

62
Q

what take over the role of the normal metabolic function of the liver in the fetus?

A

The placenta is performing the normal metabolic function of liver.

63
Q

what are premature and growth restricted infants more prone to?
(to do with liver)

A

The premature and growth restricted infants are more prone to jaundice and hypoglycemia

64
Q

what forms the renal collecting system?

A

The metanephros forms the renal collecting system (uerters,pelvis, calyces, and the collecting ducts).

65
Q

what forms the renal secretory system?

A

The mesenchyme of the nephrogenic cord forms the renal secretory system ( glomeruli, convoluted tubes, loops of Henle).

66
Q

when is nephrogenesis completed by?

A

36 weeks

67
Q

what does fetal urine form?

A
  • Fetal urine forms much of the amniotic fluid.

* Renal agenesis result in severe oligohydramnios

68
Q

when is fetal movement first perceived by the mother?

A

Fetal movement (quickening) can be 1st precieved by the mother by 18-20 wk in primigravida, and several wks earlier in multigravida.

69
Q

why is self monitoring of fetal movement important?

A

Self monitoring of fetal movement is an important method fetal well-being.

Diminished fetal movement may indicate chronic hypoxia and growth restriction, this will need further investgation.

70
Q

what does the fetus develop with maturation of central nervous system?

A

With maturation of the central nervous system, the fetus develops more complex and well defined behavioral states named 1F-4F

71
Q

what is state 1F behavioural state?

A

state 1F is similar to quit(non REM)sleep,absence of eye and body movements.

72
Q

what is state 2F behavioural state?

A

state 2F periodic body and eye movement are present(REM sleep).

73
Q

what is state 3F behavioural state?

A

state 3F is like quiet wakefulness when there are eye but no body movements.

74
Q

what is state 4F behavioural state?

A

state 4F body in active ongoing body and eye movement.

75
Q

what two behavioural states will the fetus alternate between?

A

> 80% of time the fetus will alternate between 1F and 2Fstate

76
Q

how is the amniotic fluid produced?

A

By 12 wk the amnion comes into contact to the inner surface of the chorion and obliterates the extra-embryonic space .

The two membranes didn’t contain blood vessels or nerves but do contain significant quantity of phospholipids and enzymes.

Choriodicedual function play a pivotal role in initiation of labour through production of prostoglandin E2 and F2a.

The amniotic fluid is initially secreted by the amnion.

By 10th wk it is mainly a transudate of the fetal serum via the skin and umbilical cord.

From 16 wks the skin become impermeable to water, so the increase in the amniotic fluid is through a contribution of kidney and lung fluids, and removed by fetal swallowing

77
Q

how much amniotic fluid is there at different stages of pregnancy?

A

10 wk - 30ml
20 wk - 300ml
30 wk - 600ml
38wk - 1000ml

From term there is rapid fall in the volume ( 40 wk :800ml, 42wk :350 ml).

78
Q

what is the function of amniotic fluid?

A
  • protect the fetus from mechanical injury.
  • permit fetal movement and preventing limbs contracture.
  • prevent adhesions between the fetus and amnion.
  • permit fetal lung development, if there is absence of the fluid especially in the 2nd trimester this will lead to pulmonary hypoplasia.
79
Q

what is the function of the placenta?

A
  1. Protection
  2. Nutrition
  3. Respiration
  4. Excretion
  5. Hormone production
80
Q

what is the placenta?

A

The placenta is a transient organ of metabolic interchange between the conceptus and mother.
It is also a transient endocrine organ.

81
Q

what two parts is the placenta composed of?

A

– Fetal component derived from the chorion

– Maternal component derived from modifications of the uterine endometrium

82
Q

what does the placenta transport?

A 
– Gases
– Water
– Minerals and vitamins
– Glucose and Amino Acids 
– Proteins
– Lipids
– Large peptide hormones (TSH, ACTH, GH, insulin, glucagon)
– Smaller molecular weight hormones (steroids, T3 and T4) and catecholamines
– Toxic substances
– Bacteria and viruses
83
Q

where does water exchange occur?

A

Water exchange occurs at the placenta and at the non-placental chorion (where it touches the amnion).

The placenta is probably the main route, but the amnion/chorion are permeable to water. Exchange is by simple diffusion.

  • Since the placenta is very permeable to water, small osmotic pressure gradients could move large quantities of water.
  • However, a hydrostatic pressure difference is more likely to be responsible for large water movement (maternal blood is at a higher pressure).
84
Q

what electrolytes are exchanged between mother and fetus?

A

• Sodium: Fetus pumps Na+ out into the
mother, making the fetus electronegative.
• May use this to regulate fluid volume, but also generates a gradient to drive other exchanges.
• Potassium: simple diffusion down electrochemical gradient.
• Chloride: active transport?
• Iodide: actively trapped

85
Q

what happens to waste products from the fetus?

A

• Bilirubin. Unconjugated and crosses by
diffusion for the mother to excrete.
• The gut and urinary tract open into amniotic fluid, which the fetus drinks – indeed, fetal urination helps to maintain amniotic fluid volume.
• After birth it must start conjugating it to excrete it

86
Q

what does the fetus use as it predominant energy source?

A

Uses carbohydrate as its predominant energy source. 1⁄2 energy comes from glucose; the remainder from amino acids and from lactate (formed from glucose in the placenta).
Also needs material for anabolism – amino acids, fatty acids, vitamins, minerals.

87
Q

what is the metabolic rate of the fetus?

A

Metabolic rate: fetus 9 ml O2/kg/min; placenta 32 ml/kg/min

88
Q

what does progesterone do to the mothers metabolism?

A

The fetus takes glucose from maternal blood. Early in pregnancy, progesterone stimulates appetite.
• Switches maternal metabolism via its GH-like actions: it mobilizes fatty acids stores for the mother to use, and renders maternal tissues less sensitive to insulin.
• Causes a rise in maternal glucose, which the fetus can capture.
• It is also a diabetogenic influence on the mother.

89
Q

what percentage of fetal fuel does lactate make up and what is it made from?

A

Lactate makes up >25% of fetal fuel – the placenta makes it from glucose. This conversion maintains the glucose gradient.

90
Q

what happens to the maternal metabolism of amino acids?

A

Maternal metabolism of amino acids becomes more efficient.

The mother does not need to eat more protein, and non- pregnant females absorb >95% of dietary protein, but urea excretion falls so the AA are being used more efficiently.

The effect is due to progesterone (reduced maternal hepatic AA deamination) and this provides the source for the fetus.

There is active transport of amino acids into the fetus. Fetal urea diffuses passively back into the mother.

91
Q

Iron in pregnancy???

A

Iron is actively transported across the placenta (a membrane iron transport protein).
• There is a net need of 550 mg in pregnancy (300 mg fetus, 50 mg placenta, 200 mg postpartum blood loss).
• Maternal intestinal absorption is enhanced.

92
Q

folic acids, calcium and water soluble vitamins transport?

A 
Folic acids (folate) and vitamin B12 are provided for the fetus at the expense of the mother.
• Calcium is also transported actively; (bone formation!); maternal increase in PTH (also as GFR increased, there’s more urinary loss to be replaced) and maternal absorption becomes more efficient.
• Water-soluble vitamins are transported; fat-soluble vitamins (A,D,E,K) cross. But babies tend to be vit. K- deficient
93
Q

oxygen stores and transport in fetus?

A
  • Fetal oxygen stores are small (2 minutes’ worth).
  • Fetal consumption is high.
  • O2 diffuses readily across the placenta.
94
Q

what is the differences between CO2 and O2 diffusion across the placenta?

A

Carbon dioxide diffuses even more readily (diffusion constant 20× that of O2).

95
Q

what is the gradient for oxygen and carbon dioxide and what are large gradients caused by?

A 
• There is obviously a diffusion gradient for O2 and CO2 (90   15 and 53   30 mmHg respectively
• Gradients vary with species.
• Large gradients caused by
(1) placental O2 consumption;
(2) long diffusion path;
(3) pattern of blood flow
96
Q

what causes oxygen to be released into placenta and was causes fetal blood to uptake oxygen?

A
  • The fall in pH of maternal blood as it passes through the placenta causes release of O2 .
  • The rise in pH of fetal blood increases uptake of O2 .
97
Q

what kind of organ is the placenta?

A

metabolic exchange organ and well a transitory endocrine organ?

98
Q

what are the 2 main types of hormone produced by placenta?

A

protein and steroid hormone

99
Q

what do the hormones produced from the placenta affect?

A 
– Stimulate ovarian function
– Maintain pregnancy
– Influence fetal growth
– Stimulate mammary function
 – Assist in parturition
100
Q

what hormones are secreted from the placenta?

A

progesterone
oestrogen
relaxin
lactogen or somatomammotropin

101
Q

what is the role of progesterone secreted from the placenta?

A

– Progesterone provides the stimulus for elevated secretion by the endometrial glands
– Progesterone inhibits myometrial contraction (progesterone block)

102
Q

what is the role of oestrogen secreted from the placenta?

A

The placental estrogens are particularly important during the last part of gestation and in most species signals the early preparturient period

103
Q

what is the role of lactogen / somatomammotropin secreted from the placenta

A

– Promoting the growth of fetus

– Stimulating the mammary gland

104
Q

what is the role of relaxin secreted from the placenta?

A

– Softening of the connective tissue in the cervix
– Promotes elasticity of pelvic ligaments
Can cause too much elasticity leading to pelvic girdle pain (PGP) or symphysis pubis dysfunction (SPD)

105
Q

in what species is relaxin secreted from the placenta?

A 
– Humans
– Mares
– Rabbits
– Pigs and monkeys 
– Cats and dogs
106
Q

what is the physiology of parturition?

A

limited space for fetus–> fetus hypothalamus –> fetus ACTH –> fetus cortisol –> placental oestrogen –> uterus PGF2 alpha –>progesterone –> induction of parturition.

MSc foetus exam (19 decks)

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