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Embryo's Journey

Embryo's Journey. DEFINITIONS.

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Embryo's Journey

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  1. Embryo's Journey

  2. DEFINITIONS • Embryo: an animal in the early stages of growth, characterized by the laying down of fundamental tissues, and the formation of primitive organs and organ systems. The developing human individual from the time of implantation to the end of the eighth week after conception. • Fetus: the unborn young of an animal, having a basic structural resemblance to the adult animal. In humans, the unborn young from the end of the eighth week after conception to the moment of birth. • One can conclude that: • The born young of a human is called a baby…

  3. TIME PERIOD: 1 day post-ovulation(~15 days LMP) • Fertilization begins when a sperm penetrates an egg, and it ends with the creation of the zygote. The fertilization process takes about 24 hours. • A sperm can survive for 48 hours, up to 5 days. It takes about 10 hours to navigate the female productive tract, from the vaginal canal into the fallopian tube, where fertilization begins. Penetration of the outer part of the egg takes about 20 minutes. • Within 11 hours following fertilization, the zygote is created and fertilization ends.

  4. TIME PERIOD: 1.5 - 3 days post-ovulation(~15.5-17 days LMP) • The zygote begins a series of divisions, each division creating blastomeres and occurring approximately every 20 hours. • Each blastomere becomes smaller and smaller with each subsequent division. • At about 16 cells, the zygote becomes a morula (mulberry shaped). By now it passed the fallopian tube and entered the uterine cavity (3-4 days after fertilization).

  5. TIME PERIOD: 4 days post – ovulation(~18 days LMP) • Cell division continues, and a cavity known as a blastocele forms in the center of the morula. • With the appearance of the cavity in the center, the entire structure is now called a blastocyst.

  6. TIME PERIOD: 5 - 6 days post-ovulation(~19-20 days LMP) • Implantation begins- hCG levels rise • The blastocyst enters the uterine cavity and erodes the epithelial lining of the uterus, starting to implant.

  7. TIME PERIOD: 7-12 days post-ovulation(~21-26 days LMP) • Implantation is complete • Ectopic pregnancies - implantation sites not in the uterus - can occur at this time and may continue up to 16 weeks unnoticed.

  8. TIME PERIOD: 16 days post-ovulation(~30 days LMP) • Size: 0.4 mm  • Neural cells originate at the top of the neural tube and differentiate into many cell types such as neurons, glial cells, pigmented cells of the skin, epinephrine producing cells of the adrenal gland, and various skeletal and connective tissues of the head.

  9. TIME PERIOD: 17-19 days post-ovulation(~31-33 days LMP) • Size: 1.0-1.5 mm • The embryonic area is shaped like a pear, and the head region is broader than the tail end. • The neural groove forms now and it is the precursor of the embryo's nervous system, one of the first organs to develop.

  10. TIME PERIOD: 21- 23 days post-ovulation(~35-37 days LMP) • Size: 1.5 - 3.0 mm • The heart tubes formed as early as 19-23 days post-ovulation fuse in an S-shape, establishing the asymmetry of the heart. As the S-shape forms, cardiac muscle contraction begins.

  11. TIME PERIOD: 26- 30 days post-ovulation (~40-44 days LMP) • Size: 4.0 - 6.0 mm • Neural tube is closed. The brain and spinal cord are the largest and most compact tissue of the embryo. • The blood system continues to develop. • Muscles, skin and cartilage develop. • The digestive epithelium layer begins to differentiate into the future locations of the liver, lung, stomach and pancreas. • The first thin surface layer of skin appears covering the embryo.

  12. TIME PERIOD: 37 - 42 days post-ovulation(~51-56 days LMP) • Size: 9.0 - 11.0 mm  • Brain is well marked by its cerebral hemispheres. The hindbrain, which is responsible for heart regulation, breathing and muscle movements, begins to develop.

  13. TIME PERIOD: 42 - 44 days post-ovulation(~56-58 days LMP) • Size: 10.0 - 13.0 mm • Primitive germ cells arrive at the genital area and will respond to genetic instructions to develop into either female or male genitals.

  14. TIME PERIOD: 48-51days post-ovulation(~62-65 days LMP) • Size: 13.0-18.0 mm • The head is more erect and semicircular canals start to form in the inner ear which will enable a sense of balance and body position. • The gonads form. In about a week, the sex of the embryo will be recognizable in the form of testes on a male. • Legs are now at their proper location, and toenails begin to appear. Muscles develop and get stronger. • 49 days post ovulation (or 63 days LMP) is the limit for MAB for now.

  15. TIME PERIOD: 51 - 53 days post-ovulation(~65-67 days LMP) • Size: 15.0 - 20.0 mm • Spontaneous movement begins • Urogenital membranes differentiate in male and female embryos.

  16. TIME PERIOD: 56 - 60 days post-ovulation(~70-74 days LMP)End of embryonic period • Size: 23.0 - 26.0 mm • Head and Neck • Head is erect and rounded. • External ear is completely developed. • Taste buds begin to form on the surface of the tongue. The primary teeth are at cap stage. Bones of the palate begin to fuse. • External genitals still difficult to recognize. • Upper and lower limbs are well formed.

  17. TIME PERIOD: 24 weeks post-ovulation(~26 weeks LMP) • Size: weight about about 1.2 pounds (540g) • Fetal brain waves begin to activate auditory and visual systems, both mouth and lips show more sensitivity. • Eyes respond to light, while ears respond to sounds originating outside uterus. Permanent teeth buds appear in gums. Nostrils begin to open. Reflex movements improve. • Blood vessels start to develop in lungs to prepare fetus for life outside the uterus. Around 26 weeks post-ovulation lungs are capable of breathing air.

  18. When is a fetus viable? • There is no sharp limit of development, age or weight at which a fetus automatically becomes viable. According to data years 2003-2005, babies born at: • 23 weeks (LMP) gestation have a survival rate of 20-35% • 24-25 weeks (LMP) gestation more than double it to 50-70% survival rate. • At 26-27 weeks (LMP), survival rate is over 90%. • Data pooled so far showed that it is rare for a baby weighing less than 500gm to survive Moore, Keith and Persaud, T. The Developing Human: Clinically Oriented Embryology, p. 103 (Saunders 2003).

  19. Can a fetus feel pain? • Pain perception requires conscious recognition or awareness of a noxious stimulus. • Neither withdrawal reflexes nor hormonal stress responses to invasive procedures prove the existence of fetal pain, because they can be elicited by nonpainful stimuli and occur without conscious cortical processing. • Fetal awareness of noxious stimuli requires functional thalamocortical connections. Thalamocortical fibers begin appearing between 23 to 30 weeks (LMP) gestational age, while electroencephalography suggests the capacity for functional pain perception in preterm neonates probably does not exist before 29 or 30 weeks. Lee SJ, Ralston HJ, Drey EA, Partridge JC, Rosen MA (2005). "Fetal pain: a systematic multidisciplinary review of the evidence". JAMA294 (8): 947–54.Retrieved 02/28/2010

  20. Beginning of Mom's journey... • The hormone estrogen increases (a hundredfold during pregnancy). • The hormone progesterone also increases as it is needed to relax the muscles in the uterus to prevent early labor. It also relaxes the stomach and intestines, leading to slower transit (bloating, constipation, hypersalivation, heartburn). • The hormones estrogen and progesterone cause breast tissue changes, one of the earliest signs of pregnancy. Usually starting around 4 to 6 weeks after implantation (as early as 49 days LMP) and lasting through the first trimester. • Frequent urination begins about 6 weeks into pregnancy and is one of pregnancy's most common early signs. • The amount of blood in a pregnant woman's body increases by 50% during pregnancy

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