Normal Pregnancy Development & Physiology of Fetus PDF

Normal Pregnancy Development & physiology of fetus ‫جامعة وارث األنبياء \\ كلية التمريض‬ ‫\\ المرحلة الثالثة‬ Cell Division and Gametogenesis Mitosis is a continuous process by which the...

Normal Pregnancy Development & physiology of fetus ‫جامعة وارث األنبياء \\ كلية التمريض‬ ‫\\ المرحلة الثالثة‬ Cell Division and Gametogenesis Mitosis is a continuous process by which the body grows and develops and dead body Cells are replaced. In this type of cell division, each daughter cell contains the same number of chromosomes as the parent cell. The 46 chromosomes in a body cell are called the diploid number of chromosomes Meiosis is a different type of cell division in which the reproductive cells undergo two sequential divisions. During meiosis, the number of chromosomes in each cell is reduced by half, to 23 chromosomes per cell, each including only one sex chromosome. This is called the haploid number of chromosomes. Figure )2( Ovulation ,fertilization ,and implantation FATIMAH FADHIL JAWAD PHD IN NURSING - At fertilization, the sex of the fetus is already determined, depending on whether the egg receives an X or Y chromosome from a sperm cell. If the egg receives an X chromosome, the baby will be a girl; a Y chromosome means the baby will be a boy. - A normal pregnancy usually lasts about from 38- 40 weeks. **************************************************************************** EMBRYONIC AND FETAL Development Cell differentiation During the week between fertilization and implantation, the cells within a zygote are identical to one another. After implantation the cells begin to differentiate and develop special functions. The chorion, amnion, yolk sac, and primary germ layers appear. Stages of Development the stages of development are:  Fertilized ovum (zygote)  Morula  Early blastocyst  Late blastocyst  The cells in the outer ring are known as trophoblast cells. They are the part of the structure that forms the placenta and membrane the inner cell called erythroblast cells is the portion that forms the embryo Fetal Membranes The chorionic villi on the inner surface gradually thin and smooth out and becomes the outermost fetal membrane—the“ chorionic membrane” The second membrane the amnion ,encloses the amniotic cavity ,containing the amniotic fluid FATIMAH FADHIL JAWAD PHD IN NURSING  An amniotic membrane that contains the amniotic fluid(AF) Functions of amniotic fluid: The following are functions of amniotic fluid:  Maintains an even temperature.  Prevents the amniotic sac from adhering to the fetal skin.  Allows symmetrical growth.  Allows buoyancy and fetal movement.  Acts as a cushion to protect the fetus and the umbilical cord from injury Alterations in amniotic fluid Normal averages 800 ml.About 600 ml of amniotic fluid surrounds the baby at full term 40(weeks gestation * Oligohydramnios :deficiency in the amount of amniotic fluid500ml at term. It’s associated with maternal disease as Diabetes Miletus , neural tube defects ,chromosomal deviations ,malformation of the central nervous system ,The gastrointestinal tract malformation. ********************************************************************** The umbilical cord is the vital connection between the fetus and the placenta. Development begins in the embryologic period around week. 3 the umbilical cord composed of two umbilical arteries and one umbilical vein surrounding by a gelatin-like extracellular matrix known as Wharton’s jelly The average umbilical cord is 50 to 60 centimeters in length 2 ,centimeters in diameter.The Function of umbilical cord carry the fetal blood back and forth to the placenta, with the umbilical vein carrying oxygenated blood with nutrients from the placenta to the fetus and the umbilical arteries transporting deoxygenated blood with waste product ***************************************************************** Placentation =Formation of the placenta from:  Embryonic trophoblastic tissues  Maternal endometrial tissues Placentation The chorion develops fingerlike villi, which: FATIMAH FADHIL JAWAD PHD IN NURSING  Become vascularized Extend to the embryo as umbilical arteries and veins Lie immersed in maternal blood The placenta is fully formed and functional by the end of the third month Functions of the Placenta 1-Organ of respiration:- Functions of Fetal Placental Circulation Respiration – Oxygen is obtained and carbon dioxide is excreted through Placenta. Nutrition - Placenta provides proteins as amino acids, carbohydrates and fats as fatty acids. Storage – It stores glucose as glycogen. Excretion – It gives out carbon dioxide bilirubin urea uric acid Protection – Prevents entry of microorganism and noxious agent but not drugs And virus. Endocrine – Produces human Chorionic Gonadotropin, Estrogen &Progesterone.-human chorionic gonadotropin , estrogen ,progesterone - ********************************************************************** Germ Layer FATIMAH FADHIL JAWAD PHD IN NURSING Milestones of Fetal Growth and Development At the End of 4th Gestational Week  By the end of the first month, the embryo is about 0.75cm in long and weight about 400 mg  The heart, no larger than a poppy seed, has begun beating.  Head, mouth, liver, and intestines begin to take shape. End of 8th Gestational Week  The embryo grows to about 2.5 cm and 20 g long and has distinct slightly webbed fingers.  Veins are clearly visible.  The placenta is already nourishing the baby through the umbilical cord.  The heart has divided into right and left chambers.  Most vital organs are developed. End of 12th Gestational Week (First Trimester)  Starting at eight weeks ,called a fetus.  By the end of the first trimester ,the fetus 8-7 cm long and weight is45 g is fully formed .He has begun swallowing and kicking.  All organs and muscles have formed and are beginning to function.  The arms ,legs ,hand ,and fingers are fully developed.  The nails on his fingers and toes are starting to develop. End of 16th Gestational Week The fetus is about 17-10 cm long and Weight: 55–120 g  th fetus covered with a layer of thick ,downy hair called lanugo.The first outlines of the face are showing.  His heartbeat can be heard clearly  This is when many mothers feel their baby's first thrilling kick.  The genital organs can be recognized as male or female End of 20th Gestational Week FATIMAH FADHIL JAWAD PHD IN NURSING   The fetus will be nearly 25 cm long and weigh almost223 g.  The skull bones are the most  important bones being developed at this time  In ultrasound ,can see fetus sucking his thumb. End of 24th Gestational Week (Second Trimester)  Length: 25 cm  Weight: 223 g  Tiny eyebrows and eyelids are visible.  There is a lot of evidence to show that the baby can hear the outside world.  The fetus lungs are filled with amniotic fluid, and he has started to practice breathing movements.  Fingerprints are formed. End of 28th Gestational Week  Fetus weighs about1200 g and is about 38-35 cm long.  His body is well formed.Fingernails cover his fingertips. End of 32nd Gestational Week -The fetus is , weight 2700 – 1800 g 48 – 42 cm. -layers of fat are piling on under his skin. -He has probably turned head-down in preparation for his coming birth. End of 36th Gestational Week  The fetus is 52 -48 cm and weight about 3000 g.  The lungs develop in preparation for breathing and the head is now head-down.  As he becomes more crowded, the last few weeks , the baby“ drops ”in preparation for delivery End of 40th Gestational Week (Third Trimester) Length: 48–52 cm (crown to rump, 35–37 cm) Weight: 3000 g (7–7.5 lb) Fetus kicks actively, hard enough to cause the mother considerable discomfort. Fetal hemoglobin begins its conversion to adult hemoglobin. The conversion is so rapid that, at birth, about 20% of hemoglobin will be adult in character. Vernix caseosa is fully formed. Fingernails extend over the fingertips. FATIMAH FADHIL JAWAD PHD IN NURSING