exam 4 fertilization

Question 1

What happens if sperm cells are present when the secondary oocyte enters the fallopian tube?

Answer 1

the vaginal pH is neutralized by alkaline secretions of male’s bulbourethral glands to allow the sperm to travel to the cervix where they use mucous to gain access into fallopian tubes which undergo reverse peristalsis to pull sperm deeper inside

Question 2

What is the zona pellucida?

Answer 2

a species-specific barrier which is eroded by enzymes in the sperm’s acrosome after the sperm cluster around the oocyte

Question 3

What happens as soon as 1 sperm penetrates the zona pellucida?

Answer 3

the barrier changes its chemical structure which prevents any additional sperm from entering; the egg finally undergoes meiosis II

Question 4

What happens after the egg undergoes meiosis II?

Answer 4

a 2nd polar body is formed; it is haploid containing 1 chromatid from each of the 23 chromosomes; it dies & disintegrates

Question 5

What is a fertilized oocyte?

Answer 5

stage in which the sperm has combined with the egg cell but their nuclei have not fused yet

Question 6

What is the result from the sperm & egg nuclei fusing?

Answer 6

a single-cell diploid embryo with 46 chromosomes (23 from each parent)

Question 7

What happens to the single-cell embryo?

Answer 7

it undergoes mitosis to make a 2-cell embryo & the process continues as more & more cells form due to multiple rounds of mitosis; eventually, the embryo is a solid ball of cells called a morula

Question 8

How long does it take the embryo to float through the fallopian tube to the uterus?

Answer 8

4-5 days

Question 9

What is occurring to ensure embryo implantation?

Answer 9

the effects of estrogen & progesterone keep the endometrium healthy; FSH release is suppressed; uterine lining blood vessels are formed rapidly

Question 10

What does the placenta release after it develops?

Answer 10

human chorionic gonadotropin (hCG)

Question 11

What does hCG do?

Answer 11

ensures that estrogen is produced by the mother & that the corpus luteum continues to release progesterone for approximately 10 weeks

Question 12

Why are the functions of hCG important?

Answer 12

ensures that the endometrium is intact & continually inhibits FSH release

Question 13

What keeps the pregnancy intact past 10 weeks?

Answer 13

estrogen levels

Question 14

What is prolactin?

Answer 14

hormone that causes breast enlargement & milk production

Question 15

What is relaxin?

Answer 15

hormone that targets ligaments at pubic symphysis causing them to stretch so that the hips can separate during childbirth

Question 16

What is oxytocin?

Answer 16

hormone that causes contraction of myometrium resulting in thinning & stretching of cervical canal & the contractions that occur in labor

Question 17

What other hormones are released during pregnancy?

Answer 17

prolactin, relaxin, & oxytocin

Question 18

What happens to the oocyte without fertilization?

Answer 18

it dies & disintegrates within 24-48 hours after ovulation but sperm can live in fallopian tube for 5 days

Question 19

What happens to the corpus luteum without fertilization?

Answer 19

it is reabsorbed into the ovary becoming a corpus albicans; this takes approximately 5 days

Question 20

What happens to progesterone levels without fertilization?

Answer 20

they decline & the endometrium cannot be maintained so it breaks down & sheds away as menstrual flow

Question 21

What happens to FSH without fertilization?

Answer 21

it is no longer suppressed; it is released & the next cycle begins