Conception and Fetal Development
Conception and Fetal Development NURB 331
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This 11 page Class Notes was uploaded by Kelsey Forbeck on Monday September 5, 2016. The Class Notes belongs to NURB 331 at University of Indianapolis taught by Professor Rairdon in Fall 2016. Since its upload, it has received 8 views. For similar materials see Lifespan 1 in NURSING at University of Indianapolis.
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Date Created: 09/05/16
NURB 330: Lifespan 1 Unit 2: Pregnancy Conception And Fetal Development ∆ Cell Division o Mitosis: The parent body cell will replicate into two cells that contain the same genetic makeup as the parent cell. Mitosis begins by copying the cell’s DNA, which is followed by division. The division will create two identical daughter cells each containing 46 chromosomes Where: Cell replicates each chromosome in nucleus Why: For growth and development/ cell replacement o Meiosis: The germ cells divide while dividing their chromosome number in HALF producing gametes (sperm and eggs) Each of the pairs of chromosomes contain one from dad and one from mom Called haploid cell because half (23) of genetic material compared to normal cells. How: Replicating DNA and then dividing twice. The male and female will then unit to form a zygote (46 chromosomes) When: Occurs only in sexual reproduction during gametogenesis ∆ Oogenesis o Defined: Process of egg formation during fetal life of a female o The primary oocyte meiotic division right away o Second meiotic division is during ovulation ∆ Spermatogenesis o Defined: Process of sperm formation during puberty of a male ∆ Fertilization o Defined: process when sperm fuses with ovum to form diploid cell, or zygote o Location: Occurs in outer third of fallopian tube o Process: 1. The sperm all fight to reach the egg. 2. Once they arrive they penetrate the membrane 3. The membrane then is not able to be penetrated by other sperm 4. The head of the sperm enlarges and transitions into the make pronucleus and tail degeneration 5. Nucleus of female ovum becomes pronucleus as well ∆ Determining the sex o Ovum contributes X chromosome ALWAYS o Sperm can carry either X or Y chromosome o When there is a sperm carrying a bigger X chromosome, then the child will be female because the sperm gives and X and the ovum gives and X. (XX = female) o When the sperm is carrying a Y and fertilizes the egg, a male child is produced because males always have a Y. o So all in all, males determine the gender of the baby. ∆ Stages of prenatal development: 1. Zygote: starts when the oocyte is fertilized by the sperm and will continue until day 14 a. Function: covers cellular replication, blastocyst formation, the start of the development of embryotic membrane, and makeup of primary germ layers 2. Embryo: At day 15 the embryo begins and lasts until 8 week of gestation or until embryo measures 3 cm frth crown to bottom. th 3. Fetus: Begins 8 week and continues until 40 week gestation or birth. ∆ Teratogens o Defined: substances or exposures that cause abnormal development o The most critical time in development of organ systems and main external features in during embryotic stage o The areas that is in the process of developing are the ones most at risk for malformation due to environmental teratogens. ∆ Functions of amniotic fluid include: 1. A source of oral fluid and respiratory waste 2. Surrounds and protects fetus 3. The fluid makes movement for musculoskeletal development possible for the fetus 4. Prevents embryo from tangling with the membranes so the fetus can grow symmetrically 5. Maintains body temperature of fetus 6. Prevents the amniotic sac from sticking to embryotic skin ∆ Abnormalities of amniotic fluid: o Oligohydraminos: a result of Potter’s syndrome (an obstruction of urine) Less than 300 mL of fluid Oligohydraminos is associated with renal abnormalities o Hydraminos (polyhydraminos): as a result of Bartter’s syndrome (fetal diuresis) Less than 2,000 ml of fluid o Hydraminos results from when a fetus does not swallow normal amounts of fluid as in esophageal atresia Associated with GI abnormalities ∆ Placenta: o Function: Provides for exchange of nutrients and waste products between fetus and mother. An early function is it is an endocrine gland that produces 4 hormones necessary to maintain pregnancy and support embryo/fetus. o The placenta develops by 3 month o The placenta is dependent on maternal circulation o Decidua basalis is where the maternal part of the placenta arises from o Hormones of the placenta: 1. Human chorionic gonadotropin (hCG) 2. Human chorionic somatomammotropin (hCS), previously known as human placental lactogen (hPL) 3. Progesterone 4. Estrogen ∆ hCG- Human Chorionic Gonadatropin o Function: Preserves function of ovarian corpus luteum During fertilization, hCG gets secreted immediately and prevents shrinkage of corpus luteum o If corpus luteum stops working then a miscarriage results o Corpus luteum increases the formation of estrogen and progesterone until week 11. At that point the placenta takes over o hCG is what you are looking for on pregnancy tests because it is detectable in maternal blood as soon as implantation occurs (8-10 days after fertilization) o The amount of hCG reaches its max at 50-70 days. After that it begins to decrease ∆ (hPL/hCS) Human Placental Lactogen/Human chorionic somatomammotropin o Causes the adjustments in the mother’s metabolism in order to make the adequate protein, glucose, and minerals available for the fetus. o Increases resistance to insulin, facilitates glucose transport across the placental membrane, and stimulates breast development. ∆ Progesterone o Function: Balancing the action of estrogen. Sort of like one is pulling and the other is pushing. Facilitates the RELAXATION or decrease of body tissue Increases the tubal and uterine nourishing secretions in order to provide nutrition for morula and blastocyst stages Reduces the contractions of the uterus to prevent spontaneous abortions Converts endometrial lining into decidual cells in order to permit implantation of blastocytes Also prepares the mammary glands for secretion of milk o Vascular system- relaxes blood vessel walls and decreases vascular resistance. (Causes hemorrhoids or edema) o GI- Contributes to constipation and heartburn. Increase GB disease because of the decrease in GB mobility o Respiratory- Decreases airway resistance o Renal- contributes to urinary stasis and ureter dilation. A contributing factor to bladder infections ∆ Estrogen o Function: Builds tissue by either increasing the number or size of tissue, blood vessels, and blood cells. Increase size of uterus Increase size of gonads Increase breast size Increase blood, lymph, and nerve supply to uterus * Estrogen increases VASCULARITY. Progesterone RELAXES muscle tone (smooth muscle)* o Appearance: Maternal side- beefy red appearance due to large amounts of arterioles and venules Fetal side- has greyish, shiny appearance at term because it develops from chorionic villi and chorionic blood vessels and the amniotic fetal membrane covers the side. o What can and cannot pass: Can: o Nutrients o Drugs o Antibodies o Viruses Cannot: o Large particles like bacteria ∆ Umbilical cord: o Forms at the same time as placenta o Body stalk (which contains blood vessels) elongates to form cord during embryotic stage o Multiple vessels in body stalk become 1 large vein and 2 small arteries o Arteries carry deoxygenated blood and waste products from fetus o Veins carry oxygenated blood and provides oxygen and nutrients to fetus o Wharton’s jelly Defined: White connective tissue that surround and separates the blood vessels Provides space needed for growth of blood vessels and fetus Keeps vessels separate so it doesn’t interfere with circulation Vessels are surrounded within Wharton’s jelly to allow movement and stretching without interfering with circulation ∆ Termination of fetal circulation o Circulation is terminated when the cord is clamped Foramen ovale- closes 2 hours after birth. Closed permanently after 3 months Ductus arteriosis- closes functionally within 15 and closes permanently in about 3 weeks Ducts venous- closes functionally when the cord is clamped and close in a week permanent
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