Gametogenesis & Fertilization

Question 1

When are precursors of gametes recognizable by?

Answer 1

The 4th week of gestation

Question 2

Where do primordial germ cells develop?

Answer 2

In the endoderm of the yolk sac

Question 3

What do primordial germ cells associate with to form primordial gonads?

Answer 3

With somatic cells

Question 4

What do primordial germ cells divide by?

Answer 4

Standard mitosis

Question 5

What hypothalmic/pitutary influences affect male and female gametes?

Answer 5

Hypothalmus - GnRH
Pituitary - LH, FSH
Sex Steroids

Question 6

What sex steroids are used in males and females?

Answer 6

Males use testosterone

Females use estrogen and progesterone

Question 7

What is initiated by week 12?

Answer 7

Meiosis I, primary oocytes are beginning to develop, aquirered layer of epithelial cells called primordial follicles

Question 8

What do follicular cells secrete?

Answer 8

OMI or oocyte maturation inhibitor which arrests the follicle at prophase I

Question 9

How many oocytes at birth, puberty and maturity?

Answer 9

~2.5 million at birth
~70,000 at puberty
~400 at maturity

Question 10

What does GnRH do to oocytes at puberty?

Answer 10

Increases FSH & LH secretion

Question 11

What does FSH do to oocytes at puberty?

Answer 11

Stimulates follicle maturation; maturing oocyte termed “Graafian follicle”

Question 12

What does LH do to oocytes at puberty?

Answer 12

Stimulates ovulation

Question 13

What does Estrogen do to oocytes at puberty and what is it secreted by?

Answer 13

Secreted by follicular cells, stimulates maturation

Question 14

What is Progesterone secreted by?

Answer 14

By the corpus luteum

Question 15

At what stage are oocytes arrested at until the menstrual cycle?

Answer 15

They are arrested as primary follicles which is an oocyte plus a single columnar layer of epithelial cells.

Question 16

What does an oocyte progress to during a menstrual cycle?

Answer 16

A secondary follicle which is a primary oocyte + zone pellucida and multi-layer epithelial cells

Question 17

What does the innermost layer of the secondary follicle attach too?

Answer 17

The corona radiata attaches to the zona

Question 18

What is the Zona pellucida made of?

Answer 18

3 glycoproteins (ZP 1,2,3)

Question 19

What does the epithelial layer of the oocytes differentiate into?

Answer 19

Into the interna and external of the theca follicle.

Question 20

What is the antrum?

Answer 20

Fluid filled cavity in center of follicle

Question 21

What does the LH surge trigger?

Answer 21

Proteolytic breakdown of ovarian wall granulose-secreted enzymes

Question 22

What prohibits the enzyme breakdown triggered by LH?

Answer 22

Theca cells

Question 23

When does meiosis resume for oocytes?

Answer 23

Just prior to ovulation

Question 24

What is OMI maintained by?

Answer 24

PK-A

Question 25

What does the LH surge cause?

Answer 25

An increase in IP3 and Ca2++ in granlosa cells which is transmitted via gap junctions to oocyte

Question 26

How does signaling for oocytes change when cAMP phosphodiesterase is increased?

Answer 26

[cAMP] goes down resulting in PK-A losing activation and OMI loses function. When PK-A mediation is shut off PK-C mediation begins.

Question 27

What is MPF?

Answer 27

Maturation Promoting Factor

Question 28

What does MPF target?

Answer 28

Nuclear laming and triggers germinal vesicle breakdown and completion of meiosis I.

Question 29

What increases MPF activity?

Answer 29

PK-C

Question 30

At what stage does the secondary oocyte arrest until fertilization?

Answer 30

Meiosis II, metaphase II

Question 31

Where are spermatogonia located?

Answer 31

As dormant cells in testicular seminiferous tubules

Question 32

What does GnRH do to spermatogenesis at puberty?

Answer 32

Increases FSH and LH

Question 33

What does FSH do to spermatogenesis at puberty?

Answer 33

Stimulates Serotoli cell secretion of androgen binding protein (ABP) and inhibin

Question 34

What does LH do to spermatogenesis at puberty?

Answer 34

Stimulates Leydig cell secretion of testosterone

Question 35

What do testosterone and DHT do to spermatogenesis at puberty?

Answer 35

Stimulate final steps of spermatogenesis

Question 36

How many lobules and seminiferous tubules are in the testes?

Answer 36

2-300 lobules each with 2-3 seminiferous tubules

Question 37

How does Sperm Differentiate?

Answer 37

Histones replaced by protamines; intensive condensation Golgi builds acrosomal Axoneme organizes flagella

Question 38

What type of genome does spermiogenesis require?

Answer 38

A diploid hormone

Question 39

How long does it take for the differentiation process of converting spermatids to mature sperms take?

Answer 39

~64 days total

Question 40

How many mature sperm are produced each day?

Answer 40

~300 million

Question 41

Are sperm and egg cells large or small?

Answer 41

``` Sperm = small Egg = huge ```

Question 42

Are sperm and egg cells motile or immotile?

Answer 42

``` Sperm = motile Egg = nonmotile ```

Question 43

Do sperm and egg cells have accessory cells?

Answer 43

``` Sperm = no Egg = Yes ```

Question 44

Do sperm and eggs have lots of cytoplasm or sparse cytoplasm?

Answer 44

``` Sperm = sparse Egg = Lots ```

Question 45

How many types of sperm and egg cells are there?

Answer 45

``` Sperm = 2 types: 23X, 23Y Egg = 1 Type: 23X ```

Question 46

How do oocytes go from the the ovaries to the fallopian tube?

Answer 46

Oocyte and follicular fluid are swept in the fallopian tube via fimbriae and mucosal cell cilia

Question 47

How does the oocyte get move toward the ampulla of the fallopian tube?

Answer 47

Via peristaltic waves

Question 48

Define emission in terms of sperm transport?

Answer 48

Semen is delivered to posterior urethra via peristalsis of ductus deferens

Question 49

Define ejaculation.

Answer 49

Semen is expelled through urethra via bulbospongiosus muscle contractions

Question 50

How much volume is expelled during ejaculation and what is the approximate sperm concentration?

Answer 50

About 2.5 - 5 ml with a sperm concentration of 50-150 x 10^6 / ml

Question 51

Where do the components of seminal fluid come from?

Answer 51

60% - seminal vesicles 25% - prostate 10% - bulbourethral (Cowper's) gland

Question 52

What do the seminal vesicles contribute to seminal fluid?

Answer 52

Fructose Prostaglandins Unique clotting proteins

Question 53

What does the prostate contribute to seminal fluid?

Answer 53

Citrate | Prostate specific antigen (PSA)

Question 54

What does the Cowper's gland contribute to seminal fluid?

Answer 54

Buffer | Mucous

Question 55

What happens in post ejaculation sperm maturation?

Answer 55

Capacitation

Question 56

What happens in capacitation?

Answer 56

Acrosome is cleared of glycoprotein coat and seminal proteins Sperm become more actively motile

Question 57

What is capacitation dependent on and who long does it take?

Answer 57

Calcium dependent | Takes 7-10 hours

Question 58

What happens post-fertilization?

Answer 58

Oocyte completes 2nd meiotic division and female and male pronuclei form Sperm parts breakdown Pronuclei breakdown Mitotic spindle organizes using centriole components from sperm tail; chromosomes arrange on spindle Mitosis begins

Question 59

What are some ways to assist fertilization?

Answer 59

IVF: in vitro fertilization GIFT: gamete intrafallopian transfer (sperm + egg transfer) ICSI: intracytoplasmic sperm injection (sperm only transfer)

Question 60

What are some reasons for male infertility?

Answer 60

Sperm count Sperm motility Sperm morphology

Question 61

What sperm count threshold is considered to be infertile?

Answer 61

< 20 X 20 ^6 / ml

Question 62

What is preimplantation genetic diagnosis (PGD) via blastomere dissection used for?

Answer 62

For diagnosis of heritable disease in 8-cell embryo

Question 63

What is the "manster" test?

Answer 63

Tests the ability of human sperm to penetrate zone-free hamster egg