1. PREGNANCY
September 18, 2018
puberty

2. Introduction Fertilization of ovum
Leads to a sequence of events called gestation/pregnancy
Ovum undergoes 1st & 2nd meiotic division to produce haploid number of chromosome
then released into oviduct by the propelling of cilia
Fertilization takes place at the ovarian end of the fallopian tube called ampulla
After fertilization a single celled structure called blastocyst is formed
Implants into the endometrium of the uterus
September 18, 2018
puberty

3. Introduction After implantation
Trophoblast cells develop over thebsurface of blastocyst
Trophoblast & other adjacent cells from the blastocyst and the uterine endometrium proliferate rapidly forming placenta
Permeable structure thus allowing conductance/diffusion of certain materials between maternal and fetal blood
September 18, 2018
puberty

4. FUNCTIONS OF PLACENTA Diffusion of foodstuffs and oxygen
From maternal blood to fetus blood
Diffusion of excretory products
From fetus blood to maternal blood
O2 diffusion
simple diffusion
Mean Po2 mothers blood 50mmHg
Mean Po2 fetal blood is 30mmHg
Means pressure gradient 20mmHg
September 18, 2018
puberty

5. Function of placenta
Mechanisms of transport O2 despite low O2 partial pressure
Fetal Hb
At low Po2 levels in fetal blood the fetal Hb can carry 20-50% more oxygen than maternal Hb can
Has a higher oxygen affinity
September 18, 2018
puberty

6. FUNCTION OF PLACENTA
Mechanisms of transport O2 despite low O2 partial pressure
2. Hb concentration of fetal blood
Is about 50% greater than that of the maternal
3. BOHR EFFECT
Explained in relation to exchange of CO2 and O2 in the lungs
Hb can carry more O2 at a low Pco2 than it can at a high Pco2
September 18, 2018
puberty

7. FUNCTION OF PLACENTA Bohr effect cont’d
Fetal blood entering placenta has increased Co2 much diffuses to maternal blood
Loss of Co2 makes fetal blood more alkaline and maternal blood more acidic
Increased capacity of fetal blood to combine with O2 where as maternal blood decrease
September 18, 2018
puberty

8. FUNCTION OF PLACENTA 3. BOHR EFFECT
Explained in relation to exchange of CO2 and O2 in the lungs
Hb can carry more O2 at a low Pco2 than it can at a high Pco2
Fetal blood entering placenta has increased Co2 much diffuses to maternal blood
Loss of Co2 makes fetal blood more alkaline and maternal blood more acidic
Increased capacity of fetal blood to combine with O2 where as maternal blood decrease
September 18, 2018
puberty

9. FUNCTION OF PLACENTA Carbondioxide diffusion Diffusion of food stuffs
Pco2 Fetal blood > maternal blood by 2-3mmHg
Pressure gradient
Co2 Diffuses from fetal blood to maternal blood
Diffusion of food stuffs
Glucose
Facilitated diffusion through placental membranes
Transported by carrier molecules in the trophoblastic cell of the membrane
Fetal blood glucose % < maternal blood
September 18, 2018
puberty

10. FUNCTION OF PLACENTA Fatty acids Other substances
Slow diffusion compared to glucose
Glucose used more easily by fetus for nutrition
Other substances
Ketone bodies,Potassium,Sodium,Chloride
Excretion of waste products
By diffusion
Fetal blood to maternal blood
Non-protein nitrogen
Urea, uric acid,creatinine
September 18, 2018
puberty

11. FUNCTION OF PLACENTA Hormonal Factors in placenta
Produces large quantities of
human chorionic gonadotropin
Estrogen
progesterone &
human chorionic somatomammotropin
Glycoprotein mwt 39000
Same function as Lutenizing Hormone
After blastocyst implants in the endometrium
September 18, 2018
puberty

12. human chorionic gonadotropin
1. Corpus luteum
Prevents involution at the end of monthly female cycle
Cause it to secrete large quantities of sex hormones (estrogen & progesterone)
Prevents menstruation
Cause endometrium
continuous growth
store large amounts of nutrients
Maintain the decidual nature of the uterine endometrium
Necessary for fetal development
Maintains pregnancy up to 7th/12th week
September 18, 2018
puberty

13. Human chorionic gonadotropin
Corpus luteum involutes slowly after 13th to 17th week of gestation
2. Fetal testes
Exerts an interstitial cell stimulating effect on testes of male fetus
Resulting in production of testosterone till birth
Cause fetus to grow male sex organs
Cause the testes to descend into the scrotum near term
September 18, 2018
puberty

14. Placental estrogen/progesterone
Secreted by syncytiotrophoblast cells of placenta
Estrogen
Formed from androgenic steroid compounds
Dehydroepiandrosterone
16hydroxydehydroepiandrosterone
Formed from adrenal glands mother and fetus
Converted by trophoblast cells to estradiol, estrone and estriol
September 18, 2018
puberty

15. Functions of Placental estrogen
Exerts proliferative function on reproductive and associated organs of the males
Enlargement
Breasts and growth of the breasts ductal structure
Female external genitalia
Relaxes pelvic ligaments of the mother
Limber sacroiliac joints becomes relatively limber
Symphysis pubis becomes elastic
Hence easier passage through birth canal
September 18, 2018
puberty

16. Function of Placental progesterone
Secretion of progesterone
Both mother & placenta
10 fold increase during pregnancy
Function
Essential for successful pregnancy
Development of nutritive cells in the endometrium (decidual cells)
Decrease uterine contractility
Prevents abortion
Contributes to development of the conceptus (morula& blastocyst)
Helps estrogen prepare the mother breast for lactation
September 18, 2018
puberty

17. human chorionic somatomammotropin
Protein mwt 38000
Produced 5th week onwards
Function-uncertain
Possible effect
Partial development of breast tissue
weak protein synthesis effect
Decrease insulin sensitivity and glucose utilization in the mothers side
Large quantities available for the fetus
Promotes release of fatty acids from fat stores
September 18, 2018
puberty

18. Other hormonal factors in pregnancy
Pituitary secretion
Anterior pituitary enlarges at least 50 %
Increased
Cortison
Thyrotoxin
Prolactin
LH/FSH suppressed
By placental estrogen & progesterone
September 18, 2018
puberty

19. Other hormonal factors in pregnancy
Corticosteroid secretion
Increased adrenocortical secertion of the glucorcoticoids
Help mobilize a.a from mothers tissue for synthesis of fetal tissue
Aldosterone & estrogen increase sodium reabsorption
pregnancy induced hypetension
Secretion by the thyroid gland
50% increase
Increased thyroxin production caused by placental hormone
Human chorionic gonadotropin
Thyroid stimulating hormone
Human chorionic thyrotropin
September 18, 2018
puberty

20. Other hormonal factors in pregnancy
Secretion by the parathyroid gland
Increase size
Increased calcium absorption from the mother bones
Maintains normal mother extracellular calcium
Secretion of relaxin by ovaries and placenta
by Corpus luteum of ovaries & placenta tissues
Polypeptide with mwt 9000
Soften the cervix at term
Mild relaxation of pelvic ligaments in humans
September 18, 2018
puberty

21. RESPONSE OF THE MOTHERS BODY TO PREGNANCY
Increased size of various sexual organs
Excessive hormones of pregnancy
Uterus
from 50gm to 110gm
Breast
Almost doubles in size
Vagina enlarges
Introitus opens more widely
Others
Oedema
Acne
Musculine and acromegaly features
September 18, 2018
puberty

22. RESPONSE OF THE MOTHERS BODY TO PREGNANCY
5. Weight gain
From 2nd semister
6. Increased metabolism/Increased metabolic rate
Thyroxine,adrenocortical homornes, sex hormones
Sensation of becoming overheated
Energy expended by muscle activity owing to carrying extra weight
7. nutrition
If no adequate dietary supply
Calcium, phosphates, iron, vitamin deficiency
September 18, 2018
puberty

23. Changes in maternal circulatory system
1. Increase blood flow through the placenta & cardiac output
625ml of blood flow through maternal circulation of the placenta each minute
Together with general increased mothers metabolism
Increase cardiac output %
2. blood volume
Increase by 30 % above normal before term
Aldosterone & estrogen
Increased fluid retention by the kidneys
Increased bone marrow activity
Extra red blood cell produced to go with excess blood volume
1-2litres of blood at term
¼ lost through bleeding
Allowing a considerable safety factor for the mother
September 18, 2018
puberty

24. Changes in maternal respiratory system
Maternal respiration
1. Because of Increased
basal metabolic rate & Body size
Total O2 utilization is 20% above normal
Commensurate amount of CO2 formed
Increased ventilation rate
2. High levels of progesterone increase respiratory centre sensitivity to CO2
increase minute ventilation
September 18, 2018
puberty

25. Changes in maternal respiratory system
3. Growing uterus
presses upwards against the abdominal contents
Decreased total excursion of the diaphragm
Consequently R.R increased to maintain extra ventilation
September 18, 2018
puberty

26. Function of the maternal urinary system during pregnancy
Rate of urination increases
Increased fluid intake
Increased load or excretory product
50% increase renal tubules reabsorption capacity
Sodium, chloride and water
Due to increased production of steroid hormones by the placenta and adrenocortex
50% increase GFR
Increased rate of water and electrolyte secretion in the urine
September 18, 2018
puberty