Lecture 5: Transport of Gametes and Fertilization

Question 1

What happens during ovulation?

Answer 1

• Astral fluid and ovum from ovary ex pulse into peritoneal cavity
• ovulation occurs under hormonal control through estrogen

Question 2

Label the stages of Egg Transport.

Answer 2

Question 3

What is the process of Egg Transport?

Answer 3

• when sperm gets to egg in ovary, follicular rupture near fimbriae (infundibulum) of oviduct
• ciliated epithelial cells and smooth muscle of oviduct help the movement of the ovum into oviduct to ampulla
• in the ampulla, fluid moves in the direction where the egg needs to go
• fertilization occurs as end of ampulla or ampulla/isthmus junction
• fertilization ovum enters isthmus and uterus

Question 4

What forces regulates the Egg Transport through the Oviduct?

Answer 4

• contraction of smooth muscle of tubule wall
• direction and rate of tubular fluid currents —> can go both ways where one will be pushing more that the other
• secretory activity of non-ciliated cells in oviduct
• (not-essential) —> cilia movement of tubal mucosa

Question 5

How long does the egg travel from the ovary to the uterus?

Answer 5

Tubal transport in humans take 3-4 days; progesterone necessary for egg to pass uterotubal junction

2 kinds of transport:
- slow transport in ampulla (72 hours)
- rapid phase through the isthmus and into the uterus

Question 6

What are the structures of the Uterine Tube?

Answer 6

Question 7

What is the pathway of Sperm Transport in the Female Reproductive Tract?

Answer 7

Question 8

What are different ways for sperm deposition in the female reproductive tract in different species?

Answer 8

Uterus - rodents, dog, pig, horse
Cervix - cat, pig
Vagina - cat. Rabbit, sheep, cattle, human

Question 9

What is the Sperm Transport pathway in the Upper Vagina?

Answer 9

1. Semilunar fluid deposits into upper vagina where the environment changes from a pH of 4.3 - 7.2 to protect spermatozoa for a few minutes until it reaches the cervix (pH of 6 - 6.5) which has an optimal environment for sperm motility

Question 10

What is the Sperm Transport Pathway in the Female Reproductive Tract: Cervix?

Answer 10

• Cervix acts as a reservoir for spermatozoa
• during the menstrual cycle, estrogen regulates the transport by releasing copious mucus in order for sperm to move
• viscosity of mucus changes as by days 9-16, the water content increases making sperm passage through the cervix at time of ovulation easier

Question 11

What are the functions of the Cervix?

Answer 11

1. Storage for sperm and inhibits migration during other phases of estrus cycle
2. Protects sperm from vagina’s acidic environment
3. Filters defective and immotile spermatozoa

Question 12

What is the Sperm Transport pathway in the Cervix: Rapid Transport?

Answer 12

• After insemination, spermatozoa penetrates cervical muscular
• some are quickly transported to reach uterine tubes within one hour of ejaculation via muscular movements performed bythe female reproductive

Question 13

What is the Sperm Transport pathway in the Cervix: Colonization of Sperm Reservoirs?

Answer 13

• cervical mucus drives # of spermatozoa to be trapped in mucosal folds of cervical crypt
• more spermatozoa in cervical reservoir = more will reach oviduct = increase chances of fertilization

Question 14

What is the Sperm Transport pathway in the Cervix: Slow Release and Transport?

Answer 14

Slow sequential release of spermatozoa in the cervical crypts (passes along cervical canal for 3-4 days) ensures continued supply for potential fertilization in oviduct
- prevents polyspermy via physiological barriers —> decreasing amount of sperm in oviduct where 2 sperm in one egg can cause early loss of pregnancy

Question 15

What is the Sperm Transport in the Uterus?

Answer 15

From uterus to oviduct, smooth muscle contracts to help spermatozoa transport but sperm motility does not play a role in entering the uterus
- Spermatozoa can enter only enter one oviductal tube through random chance, travels via a chemoattractant that is released by the egg to dictate where the sperm should go

Question 16

What is the Sperm Transport pathway in the Oviduct?

Answer 16

• controlled by peristalsis and anti-peristalsis of oviductal musculature, where 200 spermatozoa can be found in the an avid cal tube at any time
• ovarian hormones, seminal plasma, and prostaglandins control the intensity of these contractions

Question 17

What is the process of Capacitation?

Answer 17

Physiological changes occurs to spermatozoa during the passage through female tract to enable penetrating egg
- tissues secreted by female tract antlers glycoprotein surface of spermatozoa

Question 18

How do Spermatozoa survive?

Answer 18

• 80hrs life span after ejaculation where it is maintained in metabolic environment provided by cervical mucus
• undergoes capacitation (separated from seminal plasma) when travelling through female genital tract

Question 19

How are most Spermatozoa loss?

Answer 19

• Most are eliminated at barriers; cervical, uterotubal junction
• phagocytosis
• ciliated cells carry damaged/immotile sperm back to cervix

Question 20

What is the series process of Fertilization?

Answer 20

Starts with motile spermatozoa penetrating corona radiata with its head fusing into ovum cytoplasm at ZP3; and ending with mixing maternal and paternal chromosomes after spermatozoon enters egg

Question 21

What is the process in which the Corona Radiata is penetrated?

Answer 21

12 motile spermatozoa surround corona radiata while the enzyme Hyalurondiase in sperm head, helps to “eat” through Zona pellucida

Question 22

What is the role of Zona Pellucida?

Answer 22

• allows only one same species spermatozoon to enter the egg —> prevents premature implantation of embryo
• acts as a filter, for substances from uterine tube enter egg

Question 23

Describe the process of an Acrosomal RXN when Spermatozoon fuses with Zona Pellucida.

Answer 23

Question 24

Explain Sperm-Oocyte Fusion.

Answer 24

Question 25

What are ways to Prevent Polyspermy?

Answer 25

Once sperm-egg fusion occurs, must prevent others from entering through 2 ways:

Fast block;
- rapid depolarization of the egg plasma membrane occurring 2-3 seconds after fusion

Slow block;
- cortical RXN

Question 26

What is the process of the Cortical RXN after the Sperm fuses into Oocyte?

Answer 26

Wave of Ca2+ from sperm-egg fusion site —> cortical granules release hydrologic enzymes and polysaccharides into perivitelline space —> cortical granules hydrolyze sperm receptor molecules in Zona, creating ZONA BLOCK