Fertilisation and Implantation

Question 1

Question 1
https://canvas.qut.edu.au/courses/15043/files/2609389?module_item_id=1438092

Answer 1

Hypoblast

Question 2

A fertilised oocyte is referred to as a:

Answer 2

Zygote

Question 3

Human chorionic gonadotropin hormone is produced by cells derived from where?

Answer 3

Trophoblast

Question 4

Match the developmental stage with its correct term:

Zygote:
Morula:
Blastocyst:
Bilaminar embryonic disc:

Differentiation into trophoblast and embryoblast
Fusion of male and female prouclei
Differentiation into epiblast and hypoblast
Rapid mitotic cell division

Answer 4

1) Zygote: Fusion of male and female prouclei
2) Morula: Rapid mitotic cell division
3) Blastocyst: Differentiation into trophoblast and embryoblast
4) Bilaminar embryonic disc: Differentiation into epiblast and hypoblast

Question 5

Question 6
https://canvas.qut.edu.au/courses/15043/files/2609389?module_item_id=1438092

Answer 5

Trophoblast

Question 6

Question 7
https://canvas.qut.edu.au/courses/15043/files/2609389?module_item_id=1438092

Answer 6

Epiblast

Question 7

What process maintains secretion of progesterone following successful implantation?

Answer 7

Corpus luteum

Question 8

The formation of the zygote is characterised by what?

Answer 8

Fusion of the male and female pronuclei

Question 9

What does the placenta form?

Answer 9

Trophoblast

Question 10

What must the spermatozoan penetrate to fertilise the oocyte?

Answer 10

Zona pellucida

Question 11

Question 13
https://canvas.qut.edu.au/courses/15043/files/2609389?module_item_id=1438092

Answer 11

Zona pellucida

Question 12

What is the most common site for fertilisation of the oocyte to occur?

Answer 12

Ampulla of the uterine tube

Question 13

Where does the blastocyst typically hatch from the zona pellucida

Answer 13

Uterine cavity of the body of the uterus

Question 14

What is the importance of meiosis in human development?

Answer 14

Meiosis halves the number of chromosomes in the resulting gametes to ensure embryo forms from maternal and paternal chromosomes

Question 15

What is the significance of menopause in the (biological) woman?

Answer 15

Women are born with finite number of gamete that begin to mature at the onset of puberty. Conversely, men produce an infinite number of sperm and remain fertile throughout life. Menopause (45-55yrs) marks the end of ova maturation (no more eggs released)

Question 16

Why are chromosomal abnormalities more frequent in the off spring of older women?

Answer 16

Degeneration of oocytes with age, resulting in non-disjunction (chromosomes fail to separate correctly, resulting in gametes with one extra, or one missing)

Question 17

Describe how it may be possible for a (biological) man to provide suitable environment for the growing fetus.

Answer 17

-Adequate space for the fetus to grow and mature
-Nourishment

Question 18

Why would delivery of the baby be life-threatening to the father (in this case, the biological man)?

Answer 18

Abdomen has not evolved to separate from the placenta during birth. High risk of haemorrhage. Risk of infection with surgery and/or if the amniotic fluid bursts while in the abdominal cavity. Potential risk of organ damage if baby reaches full term

Question 19

What is the timing of embryonic period compared to foetal period?

Answer 19

Embryonic period weeks 1-8. Foetal period after

Question 20

What occurs during embryonic period?

Answer 20

Gametogenesis, fertilisation, cleavage, morphogenesis, gastrulation, organogenesis, maturation

Question 21

What is the purpose of the zona pellucida?

Answer 21

Barrier to Sperm Entry, Sperm Recognition, Induction of the Acrosome Reaction, Protecting the Developing Embryo, Signalling Role

As the embryo continues to develop and divide, the zona pellucida eventually degrades and disappears, allowing the embryo to implant into the uterine lining.

Question 22

What is main morphological difference between morula and blastocyst?

Answer 22

the main morphological difference is that the morula is an early, solid ball of cells without a central cavity, while the blastocyst is a more advanced stage with a central cavity and the presence of distinct inner (embryo space) and outer cell layers (trophectoderm) , each with specific roles in embryonic development.

Question 23

What is meant by hatching of the blastocyst?

Answer 23

Eventually, the pressure exerted by the expanding blastocyst, combined with the enzymatic degradation of the zona pellucida, leads to the blastocyst “hatching” or emerging from the zona pellucida. Hatching is a crucial step because it allows the blastocyst to make direct contact with the endometrial lining and initiate the process of implantation.

Question 24

The trophoblast and embryoblast of the blastocyst give rise to which tissue components?

Answer 24

Trophoblast- gives rise to embryonic part of placenta
Embryoblast- cells give rise to embryo

Question 25

How does the birth control pill physiologically prevent pregnancy?

Answer 25

Suppression of Ovulation: One of the primary mechanisms of action of birth control pills is the suppression of ovulation, the release of an egg from the ovaries. Oestrogen and progestin in the pill work together to inhibit the secretion of hormones such as luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland. These hormones are necessary for the maturation and release of an egg from the ovarian follicles. Without a mature egg, ovulation does not occur, and there is no egg available for fertilization.

Thickening of Cervical Mucus: Birth control pills, particularly those containing progestin, also thicken the cervical mucus. This thicker mucus acts as a barrier that makes it more difficult for sperm to pass through the cervix and reach the uterus and fallopian tubes, where fertilization typically occurs.

Changes in the Uterine Lining: Birth control pills can alter the lining of the uterus (endometrium), making it less receptive to a fertilized egg. This change can make it less likely for a fertilized egg to implant and establish a pregnancy.

Question 26

What is historical significance of 17th century drawing of a sperm by Hartoeker?

Answer 26

Hartsoeker’s drawing also stirred controversy and debate. In his drawing, he included what he believed to be a “homunculus” inside the head of the sperm—a tiny, fully formed human. This concept, known as preformationism, was a prevailing theory at the time, suggesting that all the information for a future individual was preformed in miniature within the sperm or egg. Hartsoeker’s illustration fuelled discussions about preformationism, which would later be challenged by the theory of epigenesis.

Question 27

What tissue characteristic of the uterine tube allows oocyte and zygote to travel through uterine tube?

Answer 27

Smooth muscle- 2 circular, 1 longitudinal
Peristalsis cilia

Question 28

What tissue changes in uterine wall for readiness for implantation?

Answer 28

Endometrium- thickens by female hormones oestrogen and progesterone, creates nutrient rich zone optimal for zygote growth

Question 29

Where does fertilisation of oocyte most commonly occur?

Answer 29

Ampulla- adequate space for zygote to travel to body of uterus, other areas too narrow or not timed well enough for zygote growth which can lead to miscarriage

Question 30

What is situs solitus of thorax?

Answer 30

Normal position of thoracic and abdominal organs (heart in right position)

Question 31

What is process of development that results in conjoined twins and which organs/regions are most commonly shared?

Answer 31

Zygotes slightly separated but not split, most common in chest wall or upper abdomen (eg sternum and liver)