Chapter 10 Fetal Development And Genetics Flashcards Preview

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Fetal development stages

Pre-embryonic stage: fertilization through the second week
Embryonic stage: end of the second week through the eighth week
Fetal stage: end of the eighth week until birth



The union of ovum and sperm which is the starting point of pregnancy. Usually around two weeks after menstrual period. Takes place in outer third of ampulla of the fallopian tube


Zona pellucid a

Clear protein layer to block extra sperm. Disappears in five days



The new life that is formed from the 23 chromosomes each joining making 46. XX is female XY is male. Implants in the endometrium about 7 to 10 days after conception



4 sets of mitosis/cleavages, 16 Cells appear as a ball of cells. Reaches the uterine cavity in 72 hours



Within the morula, a hollow ball of fluid filled space or cells (inner cell mass). The inner surface will form the embryo and amnion.



The outer layer of cells surrounding the blastocyst. Will develop the embryonic membranes, the chorion, and helps form placenta.



Usually occurs in the upper uterus or fundus. Usually with in 7 to 10 days after conception


Amniotic fluid

Surrounds the embryo and increases in volume up to 1 L at term. It comes from fluid transported from the maternal blood and fetal urine. It helps maintain constant body temperature, symmetric growth and development, and cushions the fetus, Allows the umbilical cord to be free of compression, promotes fetal movement and muscular development.



Too little amniotic fluid, less than 500 mL at term. Associated with utero placental Insufficiency and fetal renal abnormalities



Too much amniotic fluid, greater than 2000 mL at term. Associated with maternal diabetes, neural tube defects, chromosomal deviations, and malformations of the central nervous system and/or GI tract That prevents normal swallowing of amniotic fluid by the fetus.


Umbilical cord

From amnion, Contains one large vein and two small arteries. Whartons jelly is a connective tissue that surrounds them to prevent compression. Average is 22 inches long and 1 inch wide. The vein supplies the oxygen, the arteries bring waste back to the mom



It is a gland that produces hormones. Made from trophoblasts which make hCG that ensures the endometrium will be receptive to the implanting embryo. It makes hormones to control physiology of the mother so the fetus is supplied with nutrients and oxygen. It protects from an immune attack, removes waste products from the fetus, induces the mother to bring more food, produces hormones that ready fetal organs. It's function depends on maternal blood pressure. Completely formed within 12 weeks



Preserves the corpus luteum and it's progesterone production so tha endometrial lining of the uterus is maintained


hPL Human placental lactogen

Controls fetal and maternal metabolism, develops maternal breast for lactation, decreases maternal insulin sensitivity to increase availability for fetus


Estrogen estriol

Enlarges women's breasts, uterus, and external genitalia, stimulates myometrial contractility


Progesterone progestin

Maintains endometrium, decreases contractility of the uterus, stimulates maternal metabolism and breast development, provides nourishment for the early conceptus



Synergistic with progesterone to maintain pregnancy, causes relaxation of pelvic ligaments, softens cervix in preparation for birth


Fetal stage

Pregnancy is 280 days. fetal stage is the end of the eighth week until birth. Longest period of prenatal development. Conceptus is now a fetus. All major systems are present.
Dramatic growth and maturation of organ systems


Fetal circulation

Carries oxygenated blood to vital areas the heart and brain while first shunting it away from the lungs and liver. The placenta takes over the functions of the lungs and liver during fetal life. As a result large volumes of oxygenated blood are not needed.


Three shunts of fetus

Ductus venosus-Umbilical vein to interior vena cava
Ductus arteriosus-Main pulmonary artery to the aorta
Foramen ovale-Anatomic opening between right and left atrium



Two or more alternative versions of the gene at a given position or Locus on the chromosome that imparts the same characteristic of that gene. Example an allele might be able to produce blue eyes or one for brown eyes.



Outward characteristics of an individual



Pictorial analysis of the number, form, and size of individuals chromosomes.


Mendels law

Inheritance of single gene disorders also referred to as monogenic or sometimes Mendelian disorders


Autosomal dominant inheritance disorder

When a single gene in the heterozygous state is capable of producing the phenotype. Examples include neurofibromatosis, Huntington's disease, achondroplasia, polycystic kidney disease. Offspring have a 50% chance of being abnormal. Male can pass the disorder onto his son. Dn nn


Autosomal recessive inherited disorders

Two abnormal genes in the homozygous state are needed for the individual to demonstrate signs and symptoms of a disorder. Examples are cystic fibrosis, phenylketonuria, TaySachs disease, sickle cell disease. 25% chance of inheriting normal 50% chance of being a carrier, and a 25% of being abnormal. Male Can pass disorder onto son. Nd Nd


X-linked inheritance disorders

The altered gene is present on the X chromosome. If the male inherits the X-linked gene he will express the condition because he only has one X-chromosome. Females inherit 2 x chromosomes so they can be heterozygous or homozygous.


Three embryonic layers

Ectoderm, mesoderm, endoderm



Forms the central nervous system, special senses, skin, and glands