Conception & Fetal Development

Question 1

After ovulation, the ruptured follicle collapses and forms what?

Answer 1

The corpus luteum

Question 2

What does the corpus luteum do?

Answer 2

Secretes progesterone and oestrogen

Question 3

What happens to the corpus luteum if pregnancy does not occur?

Answer 3

Degenerates in 10 days, leaving a scar called corpus albicans

Question 4

What happens to the corpus luteum if pregnancy does occur?

Answer 4

It produces hormones until the placenta takes over the role at about week 10 of pregnancy

Question 5

Explain the process pre-conception

Answer 5

• ovulation, an oocyte is in the fallopian tube
• spern ejaculated into vagina and some cross the cervical os and entered fallopian tubes
• before fertilisation sperm undergoes two maturational changes

Question 6

What are the two maturational changes sperm undergoes before fertilisation?

Answer 6

Capacitation and acrosome reaction

Question 7

Explain sperm maturation - Capacitation

Answer 7

• degeneration of the membrane over the acrosome (sperm head)
• stimulated by chemical within female genital tract
• increases mobility of sperms tail

Question 8

Explain sperm maturation - acrosome reaction

Answer 8

• binding a sperm to the zona pellicuda triggers the acrosome reaction
• release of enzymes prior to the binding disperse to corona radiate
• following binding enzymes, sperm digests and penetrates a path to egg cell

Question 9

What is the zona pellicuda?

Answer 9

outer layer of the ovum, jelly-like layer

Question 10

What is the corona radiate?

Answer 10

The outermost layer of the ovum

Question 11

What occurs upon entry of sperm during fertilisation?

Answer 11

the ovum nucleus swells, creating the female pronucleus. The sperm nucleus is released in the cytoplasm of the oocyte and the two nuclei approach each other

Question 12

What makes the female and male nuclei both ‘haploid’?

Answer 12

They contain 23 chromosomes

Question 13

What are the fused nuclei named as the conceptus (product of fertilisation)?

Answer 13

Zygote

Question 14

The zygote is ‘diploid’ because..

Answer 14

It holds 46 chromosomes

Question 15

Within 24 hours what happens to the zygote?

Answer 15

undergoes mitosis and splits into 2 smaller cells

Question 16

What is the process of the zygote splitting called?

Answer 16

cleavage

Question 17

What is the name of the smaller cells of zygote called when split?

Answer 17

blastomeres

Question 18

The zygote continues cleaving, dividing into:

Answer 18

• 2 cells within 24 hours
• 4 cells within 48 hours
• 8 cells within 60 hours
• 16 cells within 72 hours

Question 19

What is the zygote known as at the point of 16 cell division?

Answer 19

Morula

Question 20

The zygote structure has not increased in size despite cleavage. How?

Answer 20

The cells become more compact

Question 21

During the development of the blastocyst (morula) what is the process of cavitation?

Answer 21

occurs where the outer cells secrete fluid into the moral creating a fluid filled cavity

Question 22

What is the name of the fluid filled cavity made through cavitation?

Answer 22

blastocyst

Question 23

When does the formation of the blastocyst occur?

Answer 23

When there is at least 32 cells - cleavage

Question 24

What is the blastocyst composed of?

Answer 24

• a single layer of trophoblasts (flattened outer cells)

- an inner cell mass, embryoblast

Question 25

What do the trophoblasts form?

Answer 25

the placenta and chorion

Question 26

What do the embryo blasts form?

Answer 26

the embryonic disc including umbilical cord and amnion

Question 27

Define chorion?

Answer 27

Outermost layer of membranes surrounding the embryo

Question 28

Define amnion?

Answer 28

The amnion is membrane that covers the embryo when first formed. Fills with amniotic fluid which causes the amnion to expand and become the amniotic sac

Question 29

When does implantation occur?

Answer 29

Between day 6 and 14 after ovulation

Question 30

What allows implantation to occur?

Answer 30

when the trophoblasts adhere to/stick to the prepared endometrium

Question 31

Implantation can result in...

Answer 31

a small amount of vaginal bleeding that can be mistaken as menstruation - known as implantation bleed

Question 32

Day 14 when implantation is complete, what begins to develop?

Answer 32

The placenta (trophoblast cells)

Question 33

Define 'embryo'

Answer 33

this term refers to the conceptus form implantation until 8 weeks after conception

Question 34

By week 2 the embryo blast cells differentiate into 2 types of cells:

Answer 34

epiblasts and hypoblasts

Question 35

What do the epiblast and hypoblast cells form?

Answer 35

Bilaminar embryonic disc

Question 36

What does the hypoblast cells form?

Answer 36

The umbilical vesicle (sac) and umbilical cord

Question 37

What does the epiblast cells form?

Answer 37

the amnion

Question 38

What does the umbilical vesicle do that is formed by hypoblast cells?

Answer 38

- provides nourishment - forms part of digestive system - produces earliest blood cells and vessels

Question 39

What does the amnion do formed by the epiblast cells?

Answer 39

grows more rapidly than the embryo and surrounds it

Question 40

Define 'organogenesis'

Answer 40

Development of the embryo

Question 41

What happens to the bilaminar embryonic disc around day 15

Answer 41

further differentiation enables the inner cell mass to become the trilaminar embryonic disc

Question 42

What are the 3 primary germ layers of the trilaminar embryonic disc?

Answer 42

- ectoderm - mesoderm - endoderm

Question 43

What does the ectoderm layer do within the trilaminar embryonic disc?

Answer 43

forms structures of nervous system, skin epidermis, hair and nails

Question 44

What does the mesoderm layer do within the trilaminar embryonic disc?

Answer 44

forms the skeleton, muscles, connective tissues, kidneys, heart, lymph, dermis of skin, blood and blood vessels

Question 45

What does the endoderm layer do within the trilaminar embryonic disc?

Answer 45

forms the epithelial layer of digestive, respiratory and urogenital systems and glandular cells of liver and pancreas

Question 46

Define 'embryonic folding'

Answer 46

the disc results in a tube from a change of shape and relationship of the organs - after 4 weeks

Question 47

Fetal Development: Weeks 8-12

Answer 47

``` Eyelids develop Kidneys begin to function Passing urine from week 10 Fetal circulation functioning Sucking and swallowing begins Lanugo appears (thin hair) Moves freely Gaining weight Fetal heart rate heard ```

Question 48

Fetal Development: Weeks 12-16

Answer 48

Skeletal development Meconium present in gut (first stool) Nasal septum and palate fuse Sex distinguishable

Question 49

Fetal Development: Weeks 16-20

Answer 49

``` ‘Quickening’ - mother feels movement Fetal heart easily heard on auscultation Vernix appears Fingernails can be seen Skin cells begin to be renewed ```

Question 50

Fetal Development: Weeks 20-24

Answer 50

Periods of sleep and activity Respond to sound Skin red and wrinkled

Question 51

Fetal Development: Weeks 24-28

Answer 51

Survival can be expected if born Eyelids open Respiratory movements

Question 52

Fetal Development: Weeks 28-32

Answer 52

Begins to store fat and iron Testes descend into the scrotum Lanugo disappears from face

Question 53

Fetal Development: Weeks 32-36

Answer 53

Increased fat make the baby more rounded Lanugo disappears from the body Nails reach tips of fingers Head hard lengthens Producing surfactant to help lung inflate at birth Weight gain 25g per day Plantar creases visible - i.e. creases in hands and feat

Question 54

Fetal Development: 36-40 weeks

Answer 54

Contours rounded Skull fully formed by soft and pliable - so the plates can override making the head as small as possible for birth At ‘term’ - birth is due