PREGNANCY September 18, 2018 puberty

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

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

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

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

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

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

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

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 20-30 % < maternal blood September 18, 2018 puberty

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

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

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

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

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

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

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

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

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

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

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

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

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

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 30-40 % 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

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

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

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