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Repro > 8. Pregnancy > Flashcards

8. Pregnancy Flashcards

1
Q

Describe the different roles of the different cell types in the blastocyst

A

Cytotrophoblast: implantation role & stem cells

Syncytiotrophoblast: multinucleated cellular sheet, good for transport
Produces enzymes to aid invasion of endometrium

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2
Q

Was is meant by implantation being interstitial

A

Uterine epithelium breached & conceptus implants within stroma

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3
Q

What is meant by the placenta being haemomonochroial

A

1 layer of trophoblast separates maternal blood from feral capillary wall

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4
Q

What are the aims of implantation

A 
Establish basic unit of exchange
Anchor placenta (establish outermost cytotrophoblast shell)
Establish maternal blood flow within placenta

(Establishment of placenta takes priority in early embryonic dev: support for pregnancy)

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5
Q

Describe the development of the basic unit of exchange

A

Primary villi: early, finger-like projections of trophoblast

Secondary villi: invasion of mesenchyme into core of villi

Tertiary villi: invasion of mesenchyme core by fetal vessels
= functional chorionic villus

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6
Q

How is the endometrium prepared for implantation

A

Decidualisation

Remodelling of spiral arteries

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7
Q

Describe decidualisaton in preparation for implantation

A

Pre-decidual cells:
Cells that fall away (endometrium)

Decidual reaction:
Provides balancing force for invading trophoblast
Interaction between pre-Decidual cells & trophoblast
Stimulated by progesterone

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8
Q

Describe re modelling of spiral arteries in preparation for implantation

A

Creates low resistance vascular bed

Maintains high flow required to meet fetal demand, especially in late gestation

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9
Q

Describe the main implantation defects

A 
Simple inappropriate site:
Ectopic pregnancy (implantation @ site other than uterine body)
Placenta Praevia (implantation in lower uterine segment)

Incomplete invasion:
Placental insufficiency (affects fetus e.g. Poor dev)
Pre-eclampsia (fetal affects & maternal signs/symptoms)

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10
Q

Describe the 2 components of the placenta after 4th month

A

Fetal portion:
Formed by chorion frondsum
Bordered by chorionic plate

Maternal portion:
Formed by Decidua basalis
Decidual plate most intimately in incorporated into placenta

Btw chorionic & decidual plates = intervillous spaces, filled with maternal blood

During 4th & 5th months, decidua form no of decidual septa:
Divide placenta into no of compartments: cotyledons
Project into intervillous spaces but don’t reach chorionic plate

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11
Q

Describe the 1st trimester placenta

A

Placenta established
Barrier to diffusion still relatively thick
Complete cytotrophoblast later beneath syncytiotrophoblast

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12
Q

Describe the term placenta

A

Surface area for exchange dramatically increased

Placental barrier now thin

Cytotrophoblast layer beneath syncytiotrophoblast lost

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13
Q

Describe the arrangement of umbilical arteries & veins

A

Project into tertiary villi, bathed in oxygenated maternal blood

2 umbilical arteries:
Deoxygenated blood from fetus to placenta

1 umbilical vein:
Oxygenated blood from placenta to fetus

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14
Q

What are cotyledons

A

Group of chorionic villi bathed in maternal blood

A buffer for fetal support, especially at end of pregnancy

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15
Q

How do cotyledons receive blood

A

Receive blood thru spiral arteries that pierce decidual plate

Pressure in arteries forces oxygenated blood into intervillous spaces & bathes small villi in oxygenated blood

As pressure decreases, blood flows back from chorionic plate towards decidua & enters endometrial veins

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16
Q

What factors influence passive diffusion of substances across the placenta

A

Concentration gradient

Barrier to diffusion (placental membrane)

Diffusion distance (haemomonochroial)

17
Q

What methods of trans epithelial transport occur across the placenta
What substances are transported

A

Simple diffusion:
Water, electrolytes, urea & Uric acid, gases (O2, CO2)

Facilitated diffusion:
Glucose

Active transport:
Specific transporters expressed by syncytiotrophoblast - amino acids, iron, vitamins

18
Q

What harmful substances can be transported across the placenta

A

Teratogens:
Thalidomide, alcohol, therapeutic drugs e.g. Anticonvulsants, drugs of abuse, maternal smoking

Some pathogens:
Varicella zoster, cytomegalovirus, treponema Pallidum, toxoplasma gondii, rubella

19
Q

The placenta plays a role as an endocrine organ in supporting pregnancy
What hormones does it secrete

A 
Protein hormones:
Human Chorionic Gonagotrophin (hCG)
Human Chorionic Somatotrophin
Human Chorionic Thyrotrohin
Human Chorionic Corticotrophin

Steroid hormones:
Progesterone
Oestrogen

20
Q

What role do protein hormones (secreted from placenta) play in supporting pregnancy

A

hCG:
Supports secretory function of corpus luteum
Increases glucose availability to fetus
Produced by syncytiotrophoblast during 1st 2m of pregnancy
Excreted in maternal urine: clinically useful

hCS:
Influences maternal metabolism; increases availability of glucose to fetus

21
Q

What role do steroid hormones play in supporting pregnancy

A

Maintain pregnant state
By end of T1, plants produces adequate steroid to support

Progesterone: influences maternal metabolism - increases appetite

22
Q

What else does the placenta synthesise

A

Glycogen
Cholesterol
Fatty acids

Largely to support own function

23
Q

How does the function of the placenta provide passive maternal immunity to the neonate

A

Receptor mediated endocytosis

Immunological competence begins in T3; fetus then making all components of complement

Fetal immunoglobulin consist almost entirely of maternal immunoglobulin (IgG) (transported from approx 14 weeks)

Fetus gains passive immunity against many infectious diseases

24
Q

Describe the mechanism of Rhesus blood group incompatibility between mother & fetus

A

Mother previously sensitised to Rhesus antigen (e.g. In a previous pregnancy)

IgG against Rhesus crosses placenta & attack so fetal rbc’s

Now uncommon because prophylactic treatment

25
Q

Describe the maternal physiological adaptations to pregnancy

A

CVS:
increased HR, SV, CO, blood vol

Urinary:
Increased renal plasma flow, glomerular filtration rate
Filtration capacity intact

Respiratory:
Diaphragm displaced
AP & transverse diameters of thorax increase
Physiological hyperventilation driven by progesterone
Increased O2 consumption, tidal vol, resp minute vol, alveolar ventilation
Decreased functional residual capacity
Unchanged vital capacity, resp rate

GI:
alterations on position of viscera (e.g. Appendix moves to RUQ)
Smooth musc relaxation by progesterone (delayed GI emptying, biliary tract stasis, increased risk pancreatitis)

Immune system:
Transfer of antobodies
Non-specific suppression of local immune response @ maternal-fetal interface

Haematology:
Mother pro-thrombotic: high fibrin deposition @ site of implantation, stasis, venodilation
Anaemia (plasma vol increases & rbc’s mass can’t keep up, iron/folate deficiency)

26
Q

Describe the metabolic changes that occur in pregnancy

A

Carbohydrate:
Glucose & aa metab altered to favour nutrition to fetus
Fat laid down in 1st 1/2 pregnancy helps meet demands of fetus later
Oestrogen stimulates prolactin release (contributes to maternal insulin resistance)
Progesterone stimulates appetite
Later on, maternal energy met by metabolising peripheral FAs

Lipid:
Increased lipolysis from T2
Increased plasma conf of free FAs on fasting
Increased utilisation FAs increases risk ketoacidosis

Thyroid hormones:
Increased TBG, T3, T4 (stimulated by hCG)
Free T4 in normal range because More TBG

27
Q

Describe How insulin levels are normally controlled in pregnancy

A

Rate of insulin secretion (basal & stimulated) normally increases as pregnancy proceeds

Ability of pancreatic beta cells to meet increased demand for insulin achieved by:
Increased rate of insulin synthesis in beta cells
Beta cell hyperplasia & hypertrophy

28
Q

Describe what goes wrong with insulin levels in gestational diabetes

A

Endocrine pancreas unable to respond to metabolic demand of pregnancy

Pancreas fails to release increased insulin

Loss of control of metabolism: blood glucose increases

29
Q

Describe the physiological changes that occur in Pre-Eclampsia

A 
Vasoconstricted
Plasma-contracted
BP raised
proteinuria
Pitting oedema

Poor uteroplacental circulation
Widespread endothelial dysfunction
Reduced tendon reflexes

30
Q

Describe what is normally included in antenatal screening

A

History & examination (risk factors)

Blood test:
Blood group
Haemoglobin
Infection

Urinalysis:
Protein

31
Q

Describe the process of implantation

A

4-5 days post fertilisation: blastocyst enters uterine cavity
after a day or so in uterine cavity, implants in endometrium

Implantation involves interaction between trophoblast cells & epithelium of uterus:
Further embedding of blastocyst into endometrium dependent on invasive property of trophoblasts

10 days post fertilisation: blastocyst fully embedded in endometrium

Repro (13 decks)

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