1
Q
What happens in week 2 of pregnancy
A
- The week of 2s
- Two distinct cellular layers emerge
- Outer cell mass
- Syncytiotrophoblast - transport membrane
- Cytotrophoblast - develop into fetal membrane
- Inner cell mass becomes the bilaminar disk
- Epiblast and hypoblast
2
Q
Identify when implantation takes place
A
- Implantation begins day 6
- Interaction between trophoblast and endometrial lining
- By day 9, blastocyst becomes embedded in endometrium
3
Q
Describe the structure of the conceptus at the end of week 2
A
- The conceptus has implanted
- The embryo and its two cavities will be suspended within a supporting sac
- Two cavities are - amniotic cavity and yolk sac
- Suspended by connecting stalk - lateral converted to umbilical cord
- Supporting sac - chorionic cavity
- Yolk sac disappears and the amniotic sac enlarges
- The chorionic sac is occupied by the expanding amniotic sac
4
Q
What is the reason for implantation
A
- Establishes the basic unit of exchange
- Anchors the placenta
- Establishes maternal blood flow within the placenta
- Villi surrounded with maternal blood
5
Q
Differentiate between primary, secondary and tertiary villi
A
- Primary villi - early finger-like projections of trophoblast
- Secondary villi - invasion of mesenchyme into core
- Tertiary villi - invasion of mesenchyme core by fetal vessels
6
Q
Explain what a chorionic villus is
A
- Placental is a specialisation of the chorionic membrane (outer membrane)
- Chorion frontosum - where villi are
- Villi are finger like projections made of trophoblast
- Have inner connective tissue core - fetal vessels
- Very good for exchange
- Have inner connective tissue core - fetal vessels
7
Q
Where in the uterine epithelium does implantation take place
A
- Implantation is interstitial
- The uterine epithelium is breached and the conceptus implants within the stroma
8
Q
Describe the change in placental membrane as the fetus grows
A
- The placental membrane becomes progressively thinner as the needs of the fetus increase
- In the human, one layer of trophoblast ultimately separates maternal blood from fetal capillary wall
- The two circulations never mix
9
Q
Describe the change in chorionic villus structure from first to third trimester
A
- First trimester villus - thicker barrier
- Cytotrophoblast act as stem cell layer of syncytium
- Allow growth for transport
- Cytotrophoblast act as stem cell layer of syncytium
- Third trimester villus - barrier at optimal thickness
- Vessels pushed against syncytiotrophoblast to maximise exchange
- Only syncytiotrophoblast and fatal capillary membrane as barrier
10
Q
Describe the blood vessels connecting placenta to fetus
A
- Two umbilical arteries - deoxygenated blood from fetus to placenta
- One umbilical vein - oxygenated blood from placenta to fetus
11
Q
What molecules travel by diffusion across placenta
A
- Simple diffusion
- Water
- Electrolytes
- Urea and uric acid
- Gases
- Facilitated diffusion
- Applies to glucose transport
12
Q
What limits gas exchange in placenta
A
- Simple diffusion
- Flow limited - not diffusion limited
- Fetal oxygen stores are small, therefore maintenance of adequate flow essential
13
Q
What substances are actively transported across placenta
A
- Specific transporters expressed by the syncytiotrophoblast
- Amino acids
- Iron
- Vitamins
14
Q
Explain the roles of steroid hormones produced by placenta
A
- Progesterone and oestrogen
- Responsible for maintaining the pregnant state
- Placental production takes over from corpus luteum by the 11th week
- Progesterone increases appetite
- Important in increasing fat stores in the mother as glucose stores mainly diverted to the fetus
- Also supports breast tissue development for lactation
- Important in increasing fat stores in the mother as glucose stores mainly diverted to the fetus
15
Q
State what protein hormones are produced in the placenta
A
- Human chorionic gonadotrophin (hCG)
- Human chorionic somatomammotrophin (hCS)
- Human chorionic thyrotrophin
- Human chorionic corticotrophin
16
Q
Explain the action of hCG
A
- Produced during first 2 months of pregnancy
- Supports the secretory function of corpus luteum
- Produced by syncytiotrophoblast therefore is pregnancy specific
- Excreted in maternal urine therefore used as the basis for pregnancy testing
- Can identify trophoblast disease such as molar pregnancy and choriocarcinoma (malignancy of chorion)
17
Q
Explain the action of hCS
A
- Increases glucose availability to fetus
- Causes insulin resistance in the mother so glucose is not stored in the mother
- Preferentially transferred to the fetus for growth
18
Q
Explain the hormonal basis for testing for pregnancy
A
- hCG measured in maternal urine
- Pregnancy specific as produced by the embryo itself
- Can be reliably detected 14 days after fertilisation
19
Q
Explain how fetal progress can be measured hormonally
A
- Oestriol used to measure fetal progress
- Only type of oestrogen directly synthesised from fetus
20
Q
Explain the function of the placenta as a provider of passive maternal immunity to the neonate
A
- Fetal immune system is immature
- Immunoglobulin transported to fetus through receptor mediated endocytosis
- Maturing as pregnancy progresses
- Immunoglobulin class-specific
- Only IgG transported across placenta
- IgG concentrations in fetal plasma exceed those in maternal circulation
21
Q
Explain how the maternal CVS system adapts to pregnancy
A
- Increases in plasma volume, cardiac output, heart rate
- Decrease in peripheral resistance - progesterone causes relaxation of smooth muscle
- Overall decrease in blood pressure early on, but gradually increases
- Increases in coagulation factors and fibrinogen
22
Q
How can the CVS system be affected in pregnancy
A
- Venous distension and engorgement may occur in late pregnancy
- Increase in stroke volume
- Uterus compresses against IVC and causes blood stasis - venous distension
- May lead to varicose veins and haemorrhoids
23
Q
How are kidneys affected in pregnancy
A
Increases in renal blood flow and glomerular filtration rate
24
Q
How are lungs affected in pregnancy
A
Increase tidal volume and oxygen consumption
25
How are breasts affected in pregnancy
- Increase breast size
| - Thin watery secretion
26
How is the GI system affected in pregnancy
- Progesterone relaxes smooth muscle to cause acid reflux and constipation
- Prolonged transit time
27
Explain complications of implantation in wrong place
- Ectopic pregnancy
- Most commonly in the ampulla
- Can be peritoneal or ovarian
- Can very quickly become life-threatening
- Development into pelvic cavity can affect blood vessels and cause bleeding into peritoneum
- Placenta praevia
- Implantation in the lower uterine segment
- Can cause haemorrhage in pregnancy
- Can require C-section delivery
28
State complications of incomplete invasion
- Placental insufficiency
| - Pre-eclampsia
29
Explain how control of invasion in implantation occurs in the uretrus
- Transformation of the endometrium in the presence of a conceptus
- Becomes the decidua
- The decidual reaction provides the balancing force for the invasive force of trophoblast
- Ectopic pregnancy - no decidua therefore no control
- If the decidual reaction is sub-optimal
- Can lead to a range of adverse pregnancy outcomes
30
What are teratogens
- Agent that can disrupt development of embryo/fetus
- Can access fetus via the placenta
- Eg, unintentional outcomes from physiological process
- Haemolytic disease of the newborn secondary to Rhesus incompatibility of mother and fetus
31
List potential teratogens
- Thalidomide - used in treatment of cancers
- Limb defects
- Alcohol
- Fetal alcohol syndrome
- Alcohol related neurodevelopmental disorder
- Therapeutic drugs
- Anti-epileptic drugs
- Warfarin
- ACE inhibitors
- Drugs of abuse
- Dependency in the fetus and newborn
- Maternal smoking
- Fetus smaller - calcification
32
Explain at what stage of pregnancy is teratogenesis is most dangerous
- Pre-embryonic - lethal effects
- Embryonic - high sensitivity
- Each organ has a period of peak sensitivity
- Fetal - decreasing sensitivity
- After embryonic period, risk of structural defects very low - except CNS
33
Explain clinical features of gestational diabetes
- Hyperglycaemia in mother will increase glucose transfer to fetus
- Increase insulin produced in fetus
- Leads to increased growth of fetus - larger baby more difficult to give birth
- May cause congenital abnormalities - heart and nervous system development interrupted
- Baby has too much insulin after birth - hypoglycaemia
- Brain damage from hypoglycaemia as it does not have glycogen storage
34
Explain clinical features of anaemia in pregnancy
- Mother needs more iron as oxygen given to fetus so more haemoglobin production needed
- Iron supplements given to mother
- Consequences of poor fetal-placental perfusion associated with anaemia
- Neurological problems
- Fetal retardation
35
Differentiate between oestrone, oestrodiol and oestriol
- Oestrone - maintains healthy thin uterine lining during menopause
- Oestrodiol - maintains healthy uterine lining for possible pregnancy during reproductive years
- Oestriol - maintains healthy thick uterine lining providing blood to the placenta during pregnancy
36
Describe the pathophysiology of preeclampsia
- Hypertension and proteinuria important diagnostic features
- Narrowing of utero-placental arteries due to fibrosis reduces blood flow to placenta
- Lead to intra-uterine growth restriction or death
- Pre-inflammatory proteins released into mother's vessels, causing vasoconstriction and retention of salt
- Both cause hypertension
- Low blood to kidney can damage glomerulus, leading to proteinuria
37
Describe the symptoms of preeclampsia
- Oedema may be present
- Seizures/fits in the mother - eclampsia
- Headaches, blurred vision, vomiting, oedema
- Stroke, impaired liver and kidney function, blood clotting problems, pulmonary oedema
- Baby - impaired development, premature birth, born small
3 - Reproduction
flashcards
Decks in class (17)
# Cards
-
Male Reproductive System17
-
Female Reproductive System18
-
Development of Reproductive Tracts16
-
Puberty and the HPG Axis22
-
Gametogenesis17
-
Menstrual Cycle20
-
Disorders of Menstruation12
-
Sex and Fertilisation18
-
Contraception and Infertility27
-
Placental Function and Dysfunction37
-
Fetal Physiology14
-
Fetal Growth and Development19
-
Labour and Delivery24
-
Infections of the Reproductive Tract31
-
Pelvic Floor17
-
Menopause12
-
Neoplasms of the Reproductive System26
