Pregnancy Flashcards
Human pregnancy
Gestation (pregnancy):
~ 266 days from conception to birth
Usually measured from the first day of the last menstrual period (280 days / 40 weeks)
A pregnancies term = its duration Divided into 3X 3-month trimesters
Fertilisation
-occurs in distal half of fallopian tube
-egg does not live long enough to reach uterus(12-24h)
-only 0.00001% of spermatozoa reach the egg
-takes 24-72h
Capacitation in sperm
Sperm must first undergo capacitation (in the uterus)
↑ Membrane calcium permeability
↑ Motility
Destabilizes the membrane of the acrosomal region
Allows for an acrosomal reaction (When sperm encounters an egg)
Enzymes released via Ca2+ influx (Acrosin and other proteases)
These enable the sperm to penetrate the egg
What happens when the sperm penetrates the egg
-Oocyte completes meiotic divisions • Must prevent polyspermy (via the cortical reaction)
-Must prevent degradation of the corpus luteum
(the zygote secretes human chorionic
gonadotrophin)
-The first sperm is not necessarily the one which fertilizes the egg
Stages of pregnancy
-blastocyst(during conception, 2weeks post fertilisation)
-embryo 2-8 weeks
-fetus from 9 weeks until birth
-birth(neonate for 6 weeks following birth)
Blastocyst stage
The pre-embryonic stage (0-2 weeks)
3 stages:
1. Cleavage
2. Implantation
3. Embryogenesis
Cleavage
Begins almost immediately after fertilisation
Mitotic divisions result in blastomeres
After 72 hours, it consists of a ball of cells called the morula Hollows out to form a blastocyst\
Parts of the blastocyst
-Trophoblast
+outer cells
+develops to form the placenta
-Blastocyst cavity
-Embryo-blast
+inner cell mass
+develops to form the embryo
Implantation
~6 days after fertilization
The blastocyst attaches and embeds into endometrium
The trophoblast begins to form the placenta This with ultimately nourish the foetus
(11 days – 12 weeks)
The trophoblast secretes Human Chorionic Gonadotropin (HCG) Stimulates corpus luteum to secrete Oestrogen and Progesterone
(Corpus luteum)The chorion eventually takes this role (the outer foetal membrane)
(Progesterone)Suppresses menstruation
Pregnancy tests
-detecting human chORionic gonadotropin
-Method:
+ Urine applied ↓HCG binds to mobile antibodies
+ HCG bind to immobilised antibodies ,Enzyme changes colour of band
+ Excess mobile antibodies bind to immobilised antibodies
Colour change = test worked
Embryogenesis
Occurs during implantation Blastomeres form into 3 primary germ layers
-blastula turns into a gastrula through the process of gastrulation
-3 layers include mesoderm ectoderm and endoderm
-Develops into everything else :Becomes the epithelia of the gut and airways
Becomes the nervous system and epidermis
All body systems present after 8 or 9 weeks
Beginning with CNS development (Neurulation) in 1st month
Foetal development
From 9 weeks until birth
The growth and differentiation of organs formed during embryogenesis
Maternal physiological adaptations in pregnancy
-The Cardiovascular System
↓Total Peripheral Resistance (in the first half of pregnancy)
-Affects other circulations:
↑ Glomerular Filtration Rate (Renal) For elimination of foetal waste products
↑ Cardiac Output (both stroke volume and heart rate) ↑ Blood volume → ↑ Preload
↑ Contractility (some ventricular hypertrophy)
-Blood pressure needs to be maintained
However, low resistance in the placenta
↓
↓ Diastolic pressure and wider pulse pressure
RBC count does not increase enough to match the ↑ in plasma volume (Physiological anaemia)
↑ Pressure by the uterus on pelvic blood vessels Impairs venous return → varicose veins and oedema
Uterine spinal arteries
Supplying nutrients to the placenta and foetus
During pregnancy, trophoblast invade and differentiate(from epithelial to endothelial phenotype)
Vascular remodelling occurs, narrow highly resistant vessels become highly dilated vessels with a Hugh capacity
Pre-eclampsia
High blood pressure disorder during pregnancy
Often with proteinuria More common in 3rd trimester
Common cause is abnormal placentation
Failure of trophoblast differentiation
↓
Inadequate invasion
↓
Narrow & highly resistant spiral arteries
Risk factors of pre-eclasmia
-multiple babies
-Kidney disease
-autoimmune diseases
-prior hypertension
-type 1/type 2 diabetes
Eclampsia
The onset of seizures or a coma with symptoms of preeclampsia
Before, during or after delivery Difficult to predict progression to eclampsia Often no prior warning signs or symptoms
Blood pressure with preeclampsia and eclampsia
-preeclampsia
>90-109 + proteinuria
-severe preeclampsia
>110 pr PE+1 danger sign
-eclampsia
>90+convulsions or unconscious
Danger signs:
-headache
-blurred vision
-upper abdominal pain
Gestational diabetes
-Diagnosed for the first time during pregnancy Effects ~16.5% of pregnancies globally
-Less effective use of insulin=high blood sugar
Risk factors of gastational diabetes
-high maternal age
-obesity
-lack of physical activity
-pre diabetic/family history
-PCOS
What does gastational diabetes increase the risks of
CVD and T2DM in mother and child Macrosomia
Future obesity of infant
Initiation of labour
Complex – Involves a number of hormones Stable myometrium → Contractile myometrium
The Trigger:
↑ Adrenocorticotropic Hormone (ACTH) secretion
Subsequent cortisol release (from the foetal adrenal gland)
Cortisol promotes conversion:
Progesterone → Oestrogen (in the placenta)
Initiation of labour part 2
-oestrogens : Promote production of PGF2α ↑ Oxytocin receptors Promotes contraction(stimulates oxytocin )
-oxytocin: Activation of the Hypothalamus = further Oxytocin release
Accumulation of oxytocin
↑ Rate and intensity of uterine contractions
Following birth – Feedback ends No further oxytocin production
Uterine contraction
Uterine Smooth Muscle : ↑ Calcium = Contraction
↓ Calcium = Relaxation
G-Protein Coupled Receptor
signalling increases intracellular Calcium
E.g. Oxytocin Receptor ↓
Oxytocin can modulate contraction!
