Fertilization and Pregnancy

Question 1

Describe the process of oocyte fertilization.

Answer 1

Oocyte fertilization involves the binding of sperm to the zona pellucida, triggering the acrosome reaction, which allows the sperm to penetrate the egg. Following penetration, the egg resumes meiosis, extrudes the second polar body, and forms the female pronucleus.

Question 2

Summarize the main features of early embryonic development up to implantation.

Answer 2

Early embryonic development includes fertilization, cleavage, and the formation of a blastocyst, which eventually implants into the uterine wall.

Question 3

How long after ovulation is an egg capable of being fertilized?

Answer 3

An egg is typically capable of being fertilized for about 12 to 24 hours after ovulation.

Question 4

How long do sperm remain viable in the female reproductive tract?

Answer 4

Sperm can remain viable in the female reproductive tract for up to 5 days.

Question 5

Define sperm capacitation and indicate its relevance to fertility.

Answer 5

Sperm capacitation is a maturation process that sperm undergo after ejaculation, allowing them to fertilize an egg. It is crucial for fertility as it enhances sperm motility and prepares the plasma membrane for the acrosome reaction.

Question 6

Explain the significance of capacitation in sperm function.

Answer 6

Capacitation increases the rate of flagellar beating and motility of sperm, making them more capable of reaching and fertilizing the egg.

Question 7

Describe the acrosome reaction.

Answer 7

The acrosome reaction occurs when a sperm binds to the zona pellucida, leading to the release of enzymes that help the sperm penetrate the egg. This reaction is crucial for successful fertilization.

Question 8

Why is it important that the acrosome reaction occurs only after sperm have bound to the zona pellucida?

Answer 8

It is important for the acrosome reaction to occur only after binding to the zona pellucida to ensure that only the sperm that are in close proximity to the egg can penetrate it, preventing polyspermy.

Question 9

Define polyspermy.

Answer 9

Polyspermy is the condition in which an egg is fertilized by more than one sperm, which can lead to abnormal development.

Question 10

Briefly describe the fast block to polyspermy.

Answer 10

The fast block to polyspermy is an immediate electrical change in the egg’s membrane potential that prevents additional sperm from binding.

Question 11

Briefly describe the slow block to polyspermy.

Answer 11

The slow block to polyspermy involves the release of cortical granules that modify the zona pellucida, making it impenetrable to other sperm after the first sperm has fertilized the egg.

Question 12

What happens during the resumption of meiosis in the egg after fertilization?

Answer 12

During the resumption of meiosis, the egg extrudes the second polar body and forms the female pronucleus.

Question 13

What forms the male pronucleus after fertilization?

Answer 13

The sperm nuclear material forms the male pronucleus after it penetrates the egg.

Question 14

Define zygote and describe its formation process.

Answer 14

A zygote is a fertilized egg formed when the male (♂) and female (♀) pronuclei fuse to create a 2N nucleus.

Question 15

Summarize the developmental steps that occur while the embryo is traversing the oviduct.

Answer 15

During the journey through the oviduct, the embryo undergoes several developmental stages, including cleavage and formation of the morula and blastocyst before implantation.

Question 16

Define morula, blastocyst, and hatching.

Answer 16

A morula is a solid ball of cells resulting from the division of the zygote, a blastocyst is a hollow structure formed from the morula that implants into the uterine wall, and hatching is the process by which the blastocyst breaks free from its protective zona pellucida.

Question 17

Explain the process of implantation and its timing.

Answer 17

Implantation begins around the 6th day following fertilization when the blastocyst burrows into the endometrium of the uterus.

Question 18

Describe the Germinal period of development

Answer 18

Germinal Period lasts from conception to 2 weeks,

Question 19

Describe the Embryonic period of development

Answer 19

Embryonic Period spans from 3 to 8 week

Question 20

Describe the Fetal period of development

Answer 20

Fetal Period extends from 9 weeks to term.

Question 21

Summarize the hormonal regulation of pregnancy.

Answer 21

Hormonal regulation of pregnancy involves various hormones, including human Chorionic Gonadotropin (hCG) and human Chorionic Somatomammotropin (hCS), which support the maintenance of pregnancy and fetal development.

Question 22

Describe the dual functions of the placenta.

Answer 22

The placenta has two primary functions: it acts as an endocrine organ, producing hormones, and it facilitates the exchange of nutrients, gases, and wastes between maternal and fetal blood.

Question 23

Explain the significance of human Chorionic Gonadotropin (hCG) in pregnancy.

Answer 23

hCG is crucial for maintaining pregnancy; it is detectable in maternal serum by the 8th day after fertilization and peaks around 60-80 days, indicating the presence of the developing embryo.

Question 24

What is the primary function of hCG and its timing of production?

Answer 24

The primary function of hCG is to support the corpus luteum and maintain progesterone production, which is essential in the early stages of pregnancy.

Question 25

Describe the structure and components of the normal term placenta.

Answer 25

A normal term placenta weighs about 500g, measures 15-20 cm in diameter, and is 2-3 cm thick, facilitating nutrient and gas exchange.

Question 26

What is the typical length and structure of the umbilical cord?

Answer 26

The umbilical cord is usually 50-70 cm long and contains two umbilical arteries and one umbilical vein.

Question 27

Explain the role of the trophoblast in placentation.

Answer 27

The trophoblast layer of the placenta grows toward maternal blood vessels, facilitating nutrient and gas exchange between the mother and fetus.

Question 28

Describe the ductus venosus and its function.

Answer 28

The ductus venosus is a fetal blood vessel that allows oxygenated blood from the placenta to bypass the liver and flow directly into the inferior vena cava.

Question 29

What is the foramen ovale and its significance in fetal circulation?

Answer 29

The foramen ovale is an opening between the right and left atria of the fetal heart that allows blood to bypass the non-functioning lungs.

Question 30

Describe the role of hormones in breast development during pregnancy.

Answer 30

Hormones such as estrogen and progesterone stimulate breast development in preparation for postnatal lactation.

Question 31

Explain how pregnancy affects fetal bone growth.

Answer 31

Pregnancy hormones support fetal bone growth by providing necessary nutrients and stimulating growth processes.

Question 32

How does insulin sensitivity change during pregnancy and what is the potential risk associated with it?

Answer 32

Insulin sensitivity decreases during pregnancy, making glucose more available to the fetus, which can increase the risk of developing gestational diabetes.

Question 33

Define the role of placental growth hormone in fetal development.

Answer 33

Placental growth hormone stimulates lipolysis and gluconeogenesis to support fetal growth.

Question 34

Outline the source of estrogens during early pregnancy.

Answer 34

Initially, estrogens come from the corpus luteum, but their function is gradually assumed by the placenta.

Question 35

Explain how the placenta contributes to estrogen production during pregnancy.

Answer 35

The placenta converts circulating androgens from fetal and maternal adrenal glands into estrogen.

Question 36

Describe the types of estrogens produced during pregnancy and their functions.

Answer 36

Initially, estrone and estradiol-17-β are produced, followed by estriol, which maintains the uterine endometrium and contributes to breast development.

Question 37

What is the source of progesterone during early pregnancy?

Answer 37

Progesterone is initially produced by the corpus luteum, with its function gradually taken over by the placenta.

Question 38

How does progesterone affect smooth muscle during pregnancy?

Answer 38

Progesterone has a relaxing effect on smooth muscle, affecting the uterus, blood vessel walls, ureters, gastroesophageal sphincter, and intestines.

Question 39

Outline the cardiovascular changes that occur during pregnancy.

Answer 39

Blood pressure decreases to a nadir at 24 weeks, then slowly returns to normal levels; pulse increases by 15-20 beats/min in the third trimester; myocardial hypertrophy and increased cardiac output occur.

Question 40

Describe the changes in blood volume during pregnancy.

Answer 40

There is an overall increase in blood volume of about 40%, with plasma volume increasing more than red blood cell volume, leading to physiological anemia of pregnancy.

Question 41

Explain the gastrointestinal effects of pregnancy.

Answer 41

Pregnancy can cause nausea due to increased levels of hormones such as progesterone and hCG.

Question 42

Describe the condition that can occur during pregnancy if severe nausea is untreated.

Answer 42

Hyperemesis gravidarum can occur, leading to dehydration, ketosis, electrolyte imbalances, and potential liver and kidney damage.

Question 43

Explain the changes in kidney size during pregnancy.

Answer 43

The kidneys increase in length by 1-1.5 cm due to increased renal blood flow.

Question 44

How does bladder capacity change during pregnancy?

Answer 44

Bladder capacity nearly doubles during pregnancy.

Question 45

Define the change in glomerular filtration rate (GFR) during the first trimester of pregnancy.

Answer 45

The GFR increases by 30-50% in the first trimester.

Question 46

What hormonal changes affect renal sodium and water retention during pregnancy?

Answer 46

High progesterone promotes renal sodium and water loss, while increased aldosterone and estrogen promote salt and water retention.

Question 47

Explain the increased risk of urinary tract infections during pregnancy.

Answer 47

The risk increases due to changes in bladder tone and capacity, as well as hormonal influences.

Question 48

Describe the cervical changes that occur during the first trimester of pregnancy.

Answer 48

The cervix softens and shows increased vascularity early in the first trimester, along with increased mucus production from endocervical glands.

Question 49

How do cervical secretions change during pregnancy?

Answer 49

Cervical secretions increase in quantity and decrease in pH due to high estrogen levels.

Question 50

What is the impact of high estrogen on vaginal health during pregnancy?

Answer 50

High estrogen levels increase susceptibility to vaginal candidiasis, a fungal infection, due to higher glycogen levels. (Yeast infection)

Question 52

Describe the acrosomal reaction on sperm

Answer 52

The acrosomal reaction occurs when sperm binds to the zona pellucida's sperm-binding receptors, leading to an increase in Ca2+ levels within the sperm. This triggers the release of acrosomal enzymes that digest holes through the zona pellucida, allowing the sperm to reach the oocyte.

Question 53

Explain the role of Ca2+ in the acrosomal reaction.

Answer 53

In the acrosomal reaction, the binding of sperm to the zona pellucida causes an increase in Ca2+ levels within the sperm, which is crucial for triggering the release of acrosomal enzymes necessary for penetrating the zona pellucida.

Question 54

How does the cortical reaction contribute to blocking polyspermy

Answer 54

The cortical reaction involves an increase in Ca2+ levels that trigger exocytosis of cortical granules, which harden the zona pellucida and destroy its sperm-binding receptors, effectively blocking polyspermy.

Question 55

What happens to the zona pellucida during the cortical reaction?

Answer 55

During the cortical reaction, the zona pellucida hardens and its sperm-binding receptors are destroyed, preventing additional sperm from binding

Question 56

Describe the role of acrosomal enzymes in fertilization

Answer 56

Acrosomal enzymes play a critical role in fertilization by digesting the zona pellucida, creating a pathway for the sperm to reach and fuse with the oocyte.

Question 57

Explain the significance of the zona reaction in fertilization.

Answer 57

The zona reaction is significant because it prevents polyspermy by hardening the zona pellucida and eliminating sperm-binding receptors after the first sperm successfully fertilizes the oocyte.

Question 58

Describe the Zona Pellucida and its significance in fertilization.

Answer 58

The Zona Pellucida is a glycoprotein layer surrounding the oocyte, playing a crucial role in fertilization by facilitating sperm binding and preventing polyspermy.

Question 59

How long does it take for the first cleavage to occur after fertilization?

Answer 59

The first cleavage occurs approximately 24 hours after fertilization.

Question 60

Explain the significance of the male and female pronuclei being visible after fertilization.

Answer 60

The visibility of male and female pronuclei indicates that the sperm and egg nuclei have fused, marking the beginning of the zygote's development.

Question 61

What happens during the completion of the second meiotic division in oocytes?

Answer 61

The completion of the second meiotic division results in the formation of a polar body, which is a byproduct of oocyte maturation.

Question 62

Do cortical granules release occur during fertilization, and what is its purpose?

Answer 62

Yes, the release of cortical granules occurs shortly after fertilization, serving to modify the Zona Pellucida to prevent additional sperm from entering the egg.

Question 63

Describe the endometrium.

Answer 63

The endometrium is the inner lining of the uterus, which plays a crucial role in the menstrual cycle and in supporting a fertilized egg during pregnancy.

Question 64

Explain the significance of the lumen of the uterus.

Answer 64

The lumen of the uterus is the hollow space within the uterus where a fertilized egg can implant and develop into a fetus.

Question 65

Define the term 'blastocyst'.

Answer 65

A blastocyst is an early stage of embryonic development that occurs approximately five days after fertilization, characterized by a fluid-filled cavity and the differentiation of cells into an inner cell mass and an outer layer.

Question 66

How does a blastocyst interact with the uterine cavity on Day 4 of development?

Answer 66

On Day 4, the early blastocyst floats in the uterine cavity and undergoes a process called 'hatching', where it breaks free from the zona pellucida, the protective outer layer.

Question 67

What happens to the zona pellucida during the blastocyst's development?

Answer 67

The zona pellucida degenerates as the blastocyst hatches, allowing it to implant into the endometrium of the uterus

Question 68

Describe the role of the endometrial epithelium.

Answer 68

The endometrial epithelium is the layer of cells that lines the endometrium, providing a suitable environment for implantation and supporting the early stages of pregnancy.

Question 69

Explain the significance of blocks to polyspermy during fertilization.

Answer 69

Blocks to polyspermy are crucial as they prevent multiple sperm from entering the oocyte, ensuring that the fertilized ovum contains only two copies of each chromosome.

Question 69

How do sperm navigate through the female reproductive tract to reach the oocyte?

Answer 69

Sperm are delivered to the vagina and undergo capacitation, which enhances their motility and ability to navigate toward the secondary oocyte.

Question 70

Describe the state of the oocyte at the time of fertilization.

Answer 70

The oocyte is arrested in meiotic metaphase II at the time of fertilization, which means it has not yet completed its second meiotic division.

Question 71

How does the sperm's surface contribute to its ability to fertilize an oocyte?

Answer 71

The sperm's surface contains enzymes and receptors that facilitate its binding to and penetration of the oocyte, allowing for successful fertilization.

Question 72

Explain the process of capacitation in sperm.

Answer 72

Capacitation is a physiological process that sperm undergo in the female reproductive tract, enhancing their motility and preparing them for the acrosome reaction necessary for fertilization.