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Lecture 3 pregnancy and lactation

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The pregnancy followed by.
Parturition followed by.
Lactation

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Lecture 3 pregnancy and lactation

  1. 1. Pregnancy and Lactation
  2. 2. • If the ovum becomes fertilized, a new sequence of events called gestation or pregnancy takes place. • The fertilized ovum eventually develops into a full-term fetus. • Fertilization of the ovum normally takes place in the ampulla of one of the fallopian tubes. • The 23 unpaired chromosomes of the male pronucleus and the 23 unpaired chromosomes of the female pronucleus align themselves to re- form a complete complement of 46 chromosomes (23 pairs) in the fertilized ovum or zygote.
  3. 3. WHAT DETERMINES THE SEX OF THE FETUS THAT IS CREATED? X chromosome (the female chromosome). Y chromosome (the male chromosome). XX combination, a female child will be born. XY combination, a male child will be born.
  4. 4. EARLY NUTRITION OF THE EMBRYO ANATOMY AND FUNCTION OF THE PLACENTA: • The total surface area of all the villi of the mature placenta is only a few square meters—many times less than the area of the pulmonary membrane in the lungs. • Nutrients and other substances pass through this placental membrane mainly by diffusion in much the same manner that diffusion occurs through the alveolar membranes of the lungs and the capillary membranes elsewhere in the body.
  5. 5. PLACENTAL PERMEABILITY AND MEMBRANE DIFFUSION CONDUCTANCE • The major function of the placenta is to provide for diffusion of foodstuffs and oxygen from the mother’s blood into the fetus’s blood and diffusion of excretory products from the fetus back into the mother. • Diffusion of Oxygen Through the Placental Membrane is: The same principles for diffusion of oxygen through the pulmonary membrane, which means by simple diffusion.
  6. 6. • The mean partial pressure of oxygen (PO2) of the mother’s blood in the placental sinuses is about 50 mm Hg. • The mean po2 in the fetal blood after it becomes oxygenated in the placenta 30 mm Hg. • The mean pressure gradient for diffusion of oxygen through the placental membrane is about 20 mm Hg. Three reasons why even this low PO2 is capable of allowing the fetal blood to transport almost as much oxygen to the fetal tissues. 1. The hemoglobin of the fetus is mainly fetal hemoglobin (more carry oxyg). 2. The hemoglobin concentration of fetal blood is about 50 percent greater than that of the mother. 3. Double bohr effect: low partial pressure of carbon dioxide in fetal blood due to exerted co2 by the fetus will increase the affinity of o2
  7. 7. HORMONAL FACTORS IN PREGNANCY: • In pregnancy, the placenta forms especially large quantities: 1. Human chorionic gonadotropin, 2. Estrogens, 3. Progesterone 4. Human chorionic somatomammotropin,
  8. 8. 1- Function of Human Chorionic Gonadotropin • Human chorionic gonadotropin is a glycoprotein having a molecular weight of about 39,000. • Function of HCG • Persistence of the corpus luteum and prevents menstruation. • Human chorionic gonadotropin stimulates the male fetal testes to produce testosterone. 2- ESTROGENS • A syncytial trophoblast cells of the placenta. • Enlargement of the mother’s uterus. • Enlargement of the mother’s breasts and growth of the breast ductal structure, enlargement of the mother’s female external genitalia. • Relax the pelvic ligaments of the mother. • Rate of cell reproduction in the early embryo.
  9. 9. 3- PROGESTERONE • Causes decidual cells to develop in the uterine endometrium. These cells play an important role in the nutrition of the early embryo. • Decreases the contractility of the pregnant uterus. • Contributes to the development of the conceptus even before implantation. • Helps estrogen prepare the mother’s breasts for lactation, 4- HUMAN CHORIONIC SOMATOMAMMOTROPIN • Often called placental lactogen. It acts like prolactin and growth hormone. • Enlargement of mammary glands and induces lactation. • like GH on protein metabolism. • It reduces the peripheral utilization of glucose in the mother. • It mobilizes fat from the adipose tissue of the mother
  10. 10. • FETOPLACENTAL UNIT: • Refers to the interaction between fetus and placenta in the formation of steroid hormones. • The interaction between fetus and placenta occurs because some of the enzymes involved in steroid synthesis present in fetus are absent in placenta and those enzymes, which are absent in fetus are present in placenta.
  11. 11. Other Hormonal Factors in Pregnancy a) Pituitary Secretion: • The anterior pituitary gland increases its production of corticotropin, thyrotropin, and prolactin. • Pituitary secretion of FSH and LH is almost totally suppressed as a result of the inhibitory effects of estrogens and progesterone from the placenta. b) Increased Corticosteroid Secretion: • Glucocorticoids is moderately increased. • Twofold increase in aldosterone secretion (pegnancy induced hypertension).
  12. 12. c) Increased Thyroid Gland Secretion: • Increases its production of thyroxine, and small quantities of a specific thyroid-stimulating hormone, called human chorionic thyrotropin. d) Increased Parathyroid Gland Secretion: • Enlarge during pregnancy due to insufficiency of Ca in diet. e) Secretion of “Relaxin” by the Ovaries and Placenta: • Secreted by the corpus luteum of the ovary and by placental tissues. • Its secretion is increased by a stimulating effect of human chorionic gonadotropin. • Relaxin is a 48–amino acid polypeptide with a molecular weight of about 9000. • Cause relaxation of the pelvic ligaments.
  13. 13. Changes in the pregnant woman: 1- Response of the Mother’s Body to Pregnancy: • The uterus increases from about 50 grams to 1100 grams, and the breasts approximately double in size. • The vagina enlarges and the introitus opens more widely. • The development of edema, acne, and masculine or acromegalic features. 2- Weight Gain in the Pregnant Woman: • The average weight gain during pregnancy is about 25 to 35 pounds. • During pregnancy, a woman often has a greatly increased desire for food. 3- Metabolism During Pregnancy: • Secretion of many hormones during pregnancy, including thyroxine, adrenocortical hormones, and the sex hormones, the basal metabolic rate of the pregnant woman increases about 15%. • The extra load she is carrying (fetus), greater amounts of energy than normal must be expended for muscle activity.
  14. 14. 4- Nutrition During Pregnancy: • Ordinarily, the mother does not absorb sufficient protein, calcium, phosphates, and iron, Vit D, Vit K from her diet during the last months of pregnancy to supply these extra needs of the fetus. To over ride these the mother should take a supplementary food. 5- Changes in the Maternal Circulatory System During Pregnancy: • Blood flow through the placenta and maternal cardiac output increase during pregnancy. • Maternal blood volume increases during pregnancy. 6- Maternal Respiration Increases During Pregnancy: • the high levels of progesterone and the increased basal metabolism during pregnancy increase the minute ventilation even more. 7- Maternal Kidney Function During Pregnancy: • The rate of urine formation by a pregnant woman is usually slightly increased because of increased fluid intake and increased load of excretory products.
  15. 15. Amniotic Fluid and Its Formation • Normally, the volume of amniotic fluid (the fluid inside the uterus in which the fetus floats) is between 500 milliliters and 1 liter. • A large portion of the fluid is derived from renal excretion by the fetus. Preeclampsia and Eclampsia Preeclamsia toxemia of pregnancy: 1- Increased BP. 2- Edema. 3- Protenurea. Eclamsia: Preeclamsia + Convulsion
  16. 16. • Parturition: means birth of the baby. • Two major categories of effects lead up to the intense contractions responsible for parturition: (1) Progressive hormonal changes that cause increased excitability of the uterine musculature. (2) Progressive mechanical changes. • Hormonal Factors That Increase Uterine Contractility: A. Increased Ratio of Estrogens to Progesterone (estrogens have a definite tendency to increase the degree of uterine contractility). B. Oxytocin Causes Contraction of the Uterus. C. Effect of Fetal Hormones on the Uterus (secretion of oxytosin, fetus’s adrenal glands secrete large quantities of cortisol ).
  17. 17. • Mechanical Factors That Increase Uterine Contractility: A. Stretch of the Uterine Musculature (fetal movements, twins born earlier than single). B. Stretch or Irritation of the Cervix (obstetricians frequently induce labor by rupturing the membranes). • ONSET OF LABOR—A POSITIVE FEEDBACK MECHANISM FOR ITS INITIATION: • Braxton Hicks contractions: is the periodic episodes of weak and slow rhythmical contractions of the uterus. It’s painless. • Braxton Hicks contractions are triggered by several factors such as: 1. Touching the abdomen 2. Movement of fetus in uterus 3. Physical activity 4. Sexual intercourse 5. Dehydration.
  18. 18. The false labor contractions are believed to help cervical dilatation. Remember that for a positive feedback to continue, each new cycle of the positive feedback must be stronger than the previous one. ABDOMINAL MUSCLE CONTRACTIONS DURING LABOR: Once uterine contractions become strong during labor, pain signals originate both from the uterus and from the birth canal. These signals, in addition to causing suffering, elicit neurogenic reflexes in the spinal cord to the abdominal muscles, causing intense contractions of these muscles.
  19. 19. STAGES OF PARTURITION: • First Stage: • Labor contractions arise from fundus of uterus and move downwards so that the head of fetus is pushed against cervix. • Second Stage: • The fetus is delivered out from uterus through cervix and vaginal canal. This stage lasts for about 1 hour. • Third Stage: • The placenta is detached from the decidua and is expelled out from uterus. It occurs within 10 to 15 minutes after the delivery of the child. • Involution of the Uterus After Parturition: • Endometrial surface autolyzes, causing a vaginal discharge known as lochia, which is first bloody and then serous in nature and continues for a total of about 10 days Hormones involved in the process of parturition • Maternal Hormones: 1. Oxytocin 2. Prostaglandins 3. Cortisol 4. Catecholamines 5. Relaxin. • Fetal Hormones 1. Oxytocin 2. Cortisol 3. Prostaglandins. • Placental Hormones 1. Estrogen 2. Progesterone 3. Prostaglandins.
  20. 20. DEVELOPMENT OF THE BREASTS: • The breasts begin to develop at puberty. • Estrogens Stimulate Growth of the Ductal System of the Breasts. • Growth of the ductal system are at least four other hormones: 1. Growth hormone. 2. Prolactin. 3. Adrenal glucocorticoids. 4. Insulin. • Progesterone Is Required for Full Development of the Lobule- Alveolar System.
  21. 21. PROLACTIN PROMOTES LACTATION • Prolactin: is secreted by the mother’s anterior pituitary gland, and its concentration in her blood rises steadily from the fifth week of pregnancy until birth of the baby. • The placenta secretes large quantities of human chorionic somatomammotropin, which probably has lactogenic properties. • The fluid secreted during the last few days before and the first few days after parturition is called colostrum; it contains essentially the same concentrations of proteins and lactose as milk, but it has almost no fat. • Growth hormone, cortisol, parathyroid hormone, and insulin: are necessary to provide the amino acids, fatty acids, glucose, and calcium required for the formation of milk.
  22. 22. • The Hypothalamus Secretes Prolactin Inhibitory Hormone: • The hypothalamus mainly stimulates production of all the other hormones, but it mainly inhibits prolactin production. • The catecholamine dopamine, which is known to be secreted by the arcuate nuclei of the hypothalamus and can decrease prolactin secretion as much as 10-fold. • Suppression of the Female Ovarian Cycles in Nursing Mothers for Many Months After Delivery: • Increased prolactin—inhibit secretion of gonadotropin- releasing hormone by the hypothalamus. • This inhibition, in turn, suppresses formation of the pituitary gonadotropic hormones—luteinizing hormone and follicle-stimulating hormone.
  23. 23. EJECTION (OR “LET-DOWN”) PROCESS IN MILK SECRETION—FUNCTION OF OXYTOCIN • Milk is secreted continuously into the alveoli of the breasts, but it does not flow easily from the alveoli into the ductal system and, therefore, does not continually leak from the nipples. • When the baby suckles, it receives virtually no milk for the first half minute or so. • Suckling on one breast causes milk flow not only in that breast but also in the opposite breast. • Inhibition of Milk Ejection: • Many psychogenic factors or even generalized sympathetic nervous system stimulation throughout the mother’s body can inhibit oxytocin secretion and consequently depress milk ejection.
  24. 24. • Antibodies and Other Anti-infectious Agents in Milk: • Multiple types of antibodies and other anti- infectious agents are secreted in milk along with the nutrients. • Several different types of white blood cells are secreted, including both neutrophils and macrophages.

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