Pregnancy and development

Question 1

Name the site of human fertilization. Define fertilization

Answer 1

• Oviducto
• 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

Question 2

Define capacitation

Answer 2

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

Question 3

Define zygote

Answer 3

• Fertilized egg

- Diploid

Question 4

Contrast dizygotic and monozygotic twins

Answer 4

• 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

Question 5

describe the events immediately following fertilization

Answer 5

• 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

Question 6

define cleavage, morula and blastocyst

Answer 6

• 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

Question 7

Devine implantation and where and when it occurs

Answer 7

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

Question 8

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

Answer 8

• 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

Question 9

Define embryo and fetus

Answer 9

• 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

Question 10

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

Answer 10

• 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

Question 11

Describe the functions of the placenta

Answer 11

• 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

Question 12

Name the tissues that comprise the placenta

Answer 12

• Moms endometrium (decidua basalis)

- baby Chorion

Question 13

Describe the decidua basalis

Answer 13

-Decidua basalis- moms endometrium

Question 14

What is the average length of human gestation

Answer 14

• 40 full weeks- 280 days

Question 15

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

Answer 15

• 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)

Question 16

Describe the positive feedback mechanism for parturition

Answer 16

-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_

Question 17

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

Answer 17

• 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)

Question 18

Define afterbirth-

Answer 18

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

Question 19

Describe trophoblast cells

Answer 19

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

Question 20

Describe chorion

Answer 20

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

Question 21

Describe chorionic villi

Answer 21

-there is the location of deffusion between mom and baby

Question 22

Describe umbilical artery and vein and umbilicus

Answer 22

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

Question 23

Describe amnion and amniotic fluid

Answer 23

• 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