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Physiological changes during pregnancy

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The physiological processes that regulate parturition and the onset of labor continue to be defined. It is clear, however, that labor onset represents the culmination of a series of biochemical changes in the uterus and cervix. These result from endocrine and paracrine signals emanating from both mother and fetus.

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Physiological changes during pregnancy

  1. 1. PHYSIOLOGY OF PREGNANCY
  2. 2. GAMETOGENESIS • The process involved in maturation of two highly specialized cells, Spermatozoon in male & Ovum in female before they unite to form zygote is called Gametogenesis.
  3. 3. OOGENESIS • The process of development of a mature ovum is called oogenesis. • The total no of primary oocyte at 20th week of gestation is about 7 million at birth 2 million at puberty 4 lakhs the rest get atrophied only 400 are likely to ovulate during the entire reproductive period.
  4. 4. • Maturation Of Oocytes: The primary oocyte undergoes first meiotic division Secondary oocyte & one polar body (unequal in size) Secondary oocyte contain two haploid no of chromosomes i.e 23X and cytoplasm & small polar body contains 23X chromosomes and scanty cytoplasm. Ovulation occurs soon after formation of secondary oocyte
  5. 5. SPERMATOGENESIS – The process involved in the development of sperms from premordial male germ cell, their differentiation into spermatozoa is called spermatogenesis. Premordial germ cell Mitosis Spermatogonia (stay in seminiferous tubules) Primary spermatocyte(46XY) First meiotic division
  6. 6. 2 secondary spermatocytes (1st with 23X chromosone) (2nd with 23Y chromosome) Second mitotic division Formation of 4 spermatids 1. 23X 2. 23X 3. 23Y 4. 23Y Undergo extensive morphological changes Spermatozoa is formed This whole process is called spermatogenesis & it requires 61 days.
  7. 7. CAPACITATION • Occurs in the fluid media of female genital tract. • Requires 2 to 3 hours. • Sperm undergoes physiological & chemical changes to make it capable of fertilizing the ovum. • Only capacited sperm can penetrate the outer covering of ova known as zona pellucida.
  8. 8. OVULATION • Process by which secondary oocyte is released from ovary following rupture of graffian follicle & it becomes available for conception. • One sec oocyte ruptures in each ovarian cycle. • Occurs on the 14th day. • Ovulation remains suspended during pregnancy & lactation.
  9. 9. FERTILIZATION • Fusion of mature sperm with mature ovum. • Occurs in ampullary part of fallopian tube. • Following ovulation ovum is picked up by the fimbria & is rapidly tranfered to ampulla. • Out of millions of sperms deposited into vagina only thousands can enter the uterine tube & only 300-350 reach the ovum. • It takes about 1 hour for sperm to reach the site.
  10. 10. • Penetration of sperm is done by disolution of external membranes of ovum i.e corona radiata & zona pellucida. • The penetration occurs by hyluronidase which is liberated from acrosomal cap of hundreds of sperms. • Soon after penetration entry of other sperms is prevented & immobilization is done by viteline block & zona reaction(hardening).
  11. 11. • Just before the union 2nd meiotic division occurs in the oocyte forming female pro nucleus of 23X chromosomes & 2nd polar body is formed. • Head & Neck of sperms which are successfully entered in oocyte form male pro nucleus with chromosome no 23X or 23Y. • Male & Female unite with each other & zygote is formed with chromosome no 46 XX/XY.
  12. 12. MORULA • After zygote formation mytotic division of nucleus occurs producing two blastomeres. • Two cell stage is reached approximtely 30 hours after fertilization. • Blastomeres continue to divide & redivide to form 4, 8 & 16 cell stage until cluster of cells is formed which is known as morula. • Morula spends 3 days in the uterine tube enters the uterine cavity through narrow uterine ostium (1mm) on the 4th day at 16-64 cell stage. • Central cell(inner cell mass) forms embryo & peripheral cell(outer cell mass) form protective & nutritive membranes for embryo.
  13. 13. BLASTOCYST • On 4th-5th day morula remains free in uterine cavity. • It is covered by a thin film of mucus. • Fluid passes through canaliculi of zona pellucida which seperates the cells of the morula & is now termed as blastocyst.
  14. 14. IMPLANTATION (nidation) • Implantation occurs in the endometrium of anterior or posterior wall of the body near fundus on the 6th day( 20th day of menstrual cycle). • Endometrium is in the secretory phase. • Occurs in 4 stages: 1. Apposition 2. Adhesion 3. Penetration 4. Invasion
  15. 15. • APPOSITION:Occurs through pinopod formation.( long finger like projections i.e microvilli that absorb endometrial fluid secreted by endometrial glands) • ADHESION:Endometrial fluid is rich in glycogen & mucin & provides nutrition to blastocyst. Unless this fluid is absorbed adhesion cannot occur. Adhesion of blastocyst to endometrium occurs through glycoproteins.
  16. 16. • PENETRATION & INVASION:Blastocyst is burried more & more deep inside the endometrium. Nutrition by maternal food. • This type of deeper penetration of human blastocyst is called as Interstitial Implantation. • Blastocyst is covered on all sides by endometrium. • This corresponds to 11-13th day after fertilization.
  17. 17. TROPHOBLAST • Just before implantation trophoblast is differentiated into outer layer of Synctio trophoblast & Inner layer of Cyto trophoblast or Langhans layer. • Placenta & fetal membranes are developed from trophoblast. • Main function- INVASION, NUTRITION & PRODUCTION OF HORMONES for maintenance of pregnancy.
  18. 18. DECIDUA • Endometrium of pregnant uterus. Named so because much of it will shed following delivery. • Decidual Reaction: Increased structural & secretory activity of the endometrium due to progesterone following implantation is known as decidual reaction. • Consists of 3 layers: 1. Superficial compact layer. (decidual cells, gland ducts & dilated capillaries). 2. Intermeiate spongy layer. (dilated uterine glands, cells, blood vessels) 3. Thin basal layer. (regeneration of mucus coat following parturation).
  19. 19. After implantation of blastocyst into compact layer of decidua the different layers are renamed as: 1. Decidua Basalis ( base of blastocyst) 2. Decidua Capsularis (covering of blastocyst) 3. Decidua Vera (rest of decidua lining the uterine cavity outside site of implantation) Functions: - Good site for implantation. - Supplies nutrition to early stage growing fetus. - Decidua basalis takes part in formation of organs.
  20. 20. • Inner cell mass forms two cavities: –The yolk sac –Amniotic cavity • In humans the yolk sac produces blood cells and future sex cells • The amniotic cavity becomes the cavity in which the embryo floats. Fluid is produced from fetal urine, and secretions from the skin, respiratory tract, and amniotic membranes.
  21. 21. GESTATION: • Divided into three trimesters. • First trimester (Months 1-3) (Initial development and rapid growth): – At the end of the first month, the embryo has a heartbeat, a two-lobed brain, and a spinal cord. – By the end of the second month, the embryo is recognizable as a human and is called a fetus. – After two months, the fetus has started to form arms and legs as well as fingers, ears, and toes. – The fetus can be visibly identifies as a male or female. – By the end of the first trimester, the heart has four chambers.
  22. 22. • Second trimester (Months 4-6) (Fetus Continues to form): – By the end of the fourth month, fingernails, toenails, eyebrows, and eyelashes have developed. – Teeth begin to form, lips appear, and head hair may begin to grow. Movement of the fetus can be felt by the mother. The fetus can bend its arms and make a fist. – During the fifth month, the heartbeat can be detected by a stethoscope. – By the end of the sixth month vernix (keeps body from dehydrating and skin from getting wrinkled) appear on baby.
  23. 23. • Third trimester (Months 7-9) (Growth): –By the seventh month lanugo (fine hair grown to insulate the fetus) appears on the baby. –By the eighth months fetus growth slows down and moves into a head-down position. –By the ninth month the fetus is full term. Skin is smooth and waxy looking. The eyes are usually gray. Languo drops off.
  24. 24. Five-Week-Old Embryo
  25. 25. Wajed Hatamleh RN, MSN, PhD. Fetus at 14 and 20 weeks gestation
  26. 26. Three-to-Four Month-Old Fetus
  27. 27. Six-Month-Old-Fetus
  28. 28. PLACENTA • The chorion develops into the fetal part of the placenta. • The chorionic villi connect the fetal circulation to the placenta • Composed of both fetal and maternal tissues
  29. 29. Functions of the placenta: 1 Transfer gasses 2 Transport nutrients 3 Excretion of wastes 4 Hormone production – temporary endocrine organ – estrogen and progesterone 5 Formation of a barrier – incomplete, nonselective – alcohol, steroids, narcotics, anesthetics, some antibiotics and some organisms can cross
  30. 30. Wajed Hatamleh RN, MSN, PhD. Placental functions • Simple diffusion - water, oxygen, carbon dioxide, sodium and chloride • Facilitated transport – glucose and galactose • Active transport – amino acids, calcium, iron, iodine, vitamins, and glucose • Pinocytosis – albumin and gamma globulin • Hydrostatic and osmotic pressure • Endocrine – hCG, hPL, estrogen and progesterone
  31. 31. HORMONES Oestrogen • Produced in corpus luteum • Produced by placenta after 12 weeks • Responsible for growth particularly of uterus and breasts
  32. 32. Progesterone • Produced in corpus luteum and then the placenta • Relaxes smooth muscle • Inhibits uterine contractions until uterus is prepared for labour • Regulates storage of body fat
  33. 33. Human chorionic gonadotrophic • Secreted from trophoblast of the developing embryo • Maintains corpus luteum until placenta takes over • Used in tests to confirm pregnancy
  34. 34. Human placental lactogen • Alters maternal metabolism • Diverts glucose to fetus • Mobilises free fatty acids from maternal stores
  35. 35. RELAXIN • Released by corpus luteum then the Placenta • Softens pelvic ligaments • Reduces myometrial tone
  • ArpitaShanbhag2

    May. 11, 2020
  • PriyaValluvan

    Jun. 5, 2019
  • AishwaryaLakshmi25

    Feb. 6, 2019

The physiological processes that regulate parturition and the onset of labor continue to be defined. It is clear, however, that labor onset represents the culmination of a series of biochemical changes in the uterus and cervix. These result from endocrine and paracrine signals emanating from both mother and fetus.

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