Lecture Ten

-7 days post fertilization: “Burrowing of the blastocyst into the uterine wall”

• Zygote – once male and female nucleus combine • Blastocyst – first 2 weeks • Embryo = 2 – 8 weeks • Foetus = week 9 to birth • Length of Pregnancy = 40 weeks

-Human chorionic gonadotropin (HCG) o Secreted by blastocyst and placenta o Found in urine gives indication of pregnancy o Stimulates growth of the corpus luteum x2 in size = increased amounts of oestrogen and progesterone

-Relaxin o Secreted by the corpus luteum and placenta -Relaxes the ligaments of the body

-Placenta o Also secretes -Estrogen: increase water retention and protein synthesis -Progesterone: smooth muscle relaxation, raises body temp

-After 3 months the corpus luteum is no longer needed the placenta is both o A point of exchange between the foetus and mother o An endocrine gland that secretes hormones to maintain pregnancy = increased levels of oestrogen and progesterone during pregnancy

• Why these changes occur 1. To provide a suitable environment for the growth, nutrition and development of the foetus. 2. To protect and prepare the mother for the process of pregnancy and support for the newborn.

-Cardiac position and size o Diaphragm pushed upwards o Apex of the heart pushed upwards and laterally o Heart enlarges by 70-80 mL -Wall thickness -Increased venous filling

-Plasma Volume o Increases by 50% to ~3800 mL o To accommodate the increased blood flow to the uterus and other organs

-Heart Rate o Increases by 15 bpm

-Stroke Volume o Increases by 10%

-Cardiac Output o Increase by 1.5 L (30-50%) o Falls when lying supine as the uterus compresses the inferior vena cava therefore decreasing venous return

-Blood Pressure o Mean arterial pressure decreases by 10 mmHg by 8 weeks’ gestation o 24 weeks it will be at its lowest o Supine hypotension syndrome -Mother lying in supine position particularly on the left side

-Peripheral Resistance o Mean arterial pressure / CO o ~ 50% reduction o Increase progesterone causes vasodilation = decreased resistance

-No change o Respiratory rate o Vital capacity -Increases in: o Tidal volume (40%) o Inspiratory capacity o Minute volume o Oxygen consumption o Ventilation – ‘over-breathing’ -Decreases in: o Expiratory reserve volume o Residual volume o Airway resistance -These increases and corresponding decreases all assist with more efficient gas mixing

-As a result of increased vascular volume: o Kidneys enlarge (volume enlarges) o Increases in: -Renal blood flow (30-50%) -Glomerular filtration rate (50%) -Evidence of glucosuria during pregnancy o Not an indication of diabetes o Possibly due to less efficient tubular reabsorption

-During pregnancy the metabolic rate increases o = increase in heat production -How does the body dissipate additional heat load? o Increase in ventilation o Increase skin blood flow -Considerations o Keep hydrated o Avoid high environmental

-Anterior Pituitary: o Increased plasma concentrations of Prolactin o Placenta produces CRH and ACTH o GH, LH, FSH are supressed -Posterior Pituitary: o Increased number of oxytocin receptors -Thyroid function increases

-Increased: o Weight gain to the anterior o Ligament Laxity - Relaxin o Joint mobility (hypermobility) -Centre of gravity alterations o Some contention: -Shift backwards to prevent falling -More pressure in the heels -Shift forwards with enlarged tummy and breasts o Upwards -Can cause: o Lordosis of the lumbar o Lordosis of the cervical o Protraction of the shoulders o Hyperextension of the knees o Back pain

-Layer of muscles which support the pelvic organs: o Uterus o Bladder o Bowel -These muscles can weaken

-Cessation of the menstrual cycle -When: o 40-50 yrs of age -Why: o Remaining number of follicles is small o Follicles left are less sensitive to FSH and LH o Reduced amount of estrogen and progesterone -Symptoms: o Uncomfortable sweating (hot flushes) o Anxiety o Fatigue o Emotional disturbances

-Post-menopausal Osteoporosis o 1 in 3 women o Reduction in bone mineral density due to hormonal factors -Reduced estrogen = increased bone loss o Consequences increased risk of fractures