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Flashcards in Pregnancy and development Deck (23):

Name the site of human fertilization. Define fertilization

-fertilization is the joining of the egg and sperm
-Sex of baby is determined
-if sperm is carrying a Y chromosome it is a boy--- X it is a girl


Define capacitation

-change in head of sperm weakening the acrosomal cap so that it may release its enzyme upon the layers around the egg


Define zygote

-Fertilized egg


Contrast dizygotic and monozygotic twins

-Dizygotic- fraternal, 2 different eggs fertilized by 2 different sperm
-Monozygotic are identical with one egg plus sperm forming zygote that then splits into 2


describe the events immediately following fertilization

-Egg wall changes so that no other sperm can enter
-nucleus of egg and sperm unite
-cleavage begins (30hrs-4days)
-In oviduct, mitosis devisions begin


define cleavage, morula and blastocyst

-Mitosis as zygote travels down oviduct
-a ball of identical cells formed from cleavage is morula
-once in uterus, the cells rearrange to become a blastocyst


Devine implantation and where and when it occurs

-When the blastocyst burrows into the endometrium on day 7-8


Describe the 3 germ layers and the organs that arise from each layer.

-Gastrulation is the state where the germ layers form
-depending which layer a cell ends up in determines which organ it will become
-Ectoderm-outer layer nervous tissue and skin
-mesoderm- skeletal, heart, muscles, vessels
-Endoderm- lungs, GI tract, Viscera

-Neurulation is the formation of the neural tube (brain and spinal cord)
-organogenesis is the beginning of formation of all major organs in the body occurring at week 4


Define embryo and fetus

-When you cannot tell what it is- embryo
-when you can tell it is human- fetus (about 10 weeks)
- at the end of the second month of gestation


Describe the function of HCG and where and when it is produced

-HCG is made by embryo from about weeks 2-12
-It is the hormone that is tested in home pregnancy test (also associated with morning sickness)
-It keeps the corpus luteum alive so that endometrium won't shed like an normal menses cycle
-by keeping the corpus luteum alive, estrogen and progesterone continue to be produced


Describe the functions of the placenta

-By week 12 the placenta takes over role of making estrogen and progesterone (till end of gestation)
-the placenta is where mom and baby blood meets with out actually mixing
- allows for diffusion of nutrients and oxygen to travel from mom to baby
-allows for diffusion of baby waste and carbon dioxide to travel baby to mom


Name the tissues that comprise the placenta

-Moms endometrium (decidua basalis)
-baby Chorion


Describe the decidua basalis

-Decidua basalis- moms endometrium


What is the average length of human gestation

- 40 full weeks- 280 days


Define parturition and labor. the water breaking refers to what?

-the uterus has weak contractions due the the high levels of estrogen towards the end of pregnancy (braxton hix)
- when these contractions are about 30 minutes apart, labor has begun
-a contraction will finally be strought enough to break the amnion and thus releasing amniotic fluid (water breaking)


Describe the positive feedback mechanism for parturition

-as the weak contractions force the babys head into the cervix, it stretches
-the stretching causing the hypothalamus to make oxytocin which is released fromt he posterior pituitary gland
-oxytocin causes a uterine contraction which forces babies head more into cervix, releasing more oxytocin
== stronger contractions, more stretching== more oxytocin== bigger contractions (positive feedback loop_


describe the effects of relaxin and oxytocin. Where are they produced?

-Relaxin is made by the placenta and relaxes the mom's pelvic structures making it easier for baby to pass
-Oxytocin causes uterine contractions, forcing babys head into the cervix (positive feedback, as cervix pressure causes more oxytocin to be released)


Define afterbirth-

-After the birth of the baby, the oxytocin is still causing uterine contractions
-empties uterus causing a shearing and passing of the placenta


Describe trophoblast cells

-Are the outer cells of the blastocyst stage of the embryo that develops into the outer membrane called the chorion


Describe chorion

-The chorion is vascular and has finger like extensions digging into mom's endometrium called villi


Describe chorionic villi

-there is the location of deffusion between mom and baby


Describe umbilical artery and vein and umbilicus

- the umbilical artery and veins comprise the umbilical cord and connect the baby to the placenta


Describe amnion and amniotic fluid

-The fetal membrane immediately surrounding the fetus is the amnion and in it is filled with fetus plus fluid (amniotic fluid)
-this fluid allows for movement, protection, and temperature control