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Midwifery 1201 > Fetal development and Embryology > Flashcards

Fetal development and Embryology Flashcards

1
Q

Describe the process of sperm production.

A

The process starts with the mitotic division (duplication) of the stem cell located inside the basement membrane of the tubules inside the testes. Then, each of the duplicated stem cells (46 chromosomes) will undergo meiosis division to become the sperm cells that have 23 chromosomes.

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2
Q

How come men have unlimited sperm cells?

A

Because their stem cells duplicate themselves before developing so they never run out of copies. However the fact that they duplicate then divide mean that there is more of a chance of genetic errors.

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3
Q

How long does the maturation process of sperm take?

A

around 24 days. This means that if the father uses any toxic substances like smoking or drugs then it can effect the sperm for almost a month

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4
Q

What is the acrosome?

A

like a crown or helmet which contains enzymes that help the sperm to cross the ovum wall. The acrosome will open the ovum wall and only the head of the sperm, containing the make DNA will enter the ovum. The rest of the cellular structures will stay outside.

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5
Q

What is capacitation?

A

The maduration that the sperm have to go through in order for fertilisation to happen. This happens inside the female genital tract. The female body sends chemical substances that will unlock certain receptors in the sperm. Which make it capable of reacting to the environment of the female body.

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6
Q

Where does capacitation happen?

A

Inside the cervical crypts

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7
Q

What happens if the women is in a fertile period?

A

The cervical music will form channels where the sperm can ‘slide’ through. Sperm is then stored in cervical crypts, where the capacitation process finishes. These crypts act as a reservoir releasing sperm over several hours Maximising the chances of fertilisation.

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8
Q

What is triggered by an orgasm?

A

Strong uterine contractions then suction up the sperm into the uterine cavity.

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9
Q

Describe the two walls of the egg.

A

These walls allow or block the entrance of sperm. The outer one is called the Corona radiata: once sperm gets here the enzyme in the acrosome are released to trigger the zona pellucida to allow the sperm head to penetrate the ovum.

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10
Q

5 steps of fertilisation

A
  1. penetration of corona radiata
  2. Species recognition Acrosome reaction
  3. Penetration of zona pellucida. Cortical reaction.
  4. Gamete fusion
  5. Meiosis completion
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11
Q

What triggers the sperm to penetrate the corona radiata?

A

chemicals produced by the oocyte

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12
Q

What is the cortical reaction?

A

It happens once a sperm has entered the zona pellucida and it means that no other sperm will be able to enter

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13
Q

What are the 3 stages of fetal development?

A

Pre embryonic: until implantation
Embryonic: 2-8 weeks
Fetal: week 9 to birth

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14
Q

What happens to the zygote within 24 hours?

A

The zygote undergoes mitosis and splits into smaller cells. This is called cleavage. Day 2 embryo

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15
Q

By day 4 what is it called?

A

Morula and has 16-20 cells

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16
Q

What is it called at day 10?

A

The blastocyst

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17
Q

What happens of the 5th day?

A

Fluid accumulates in the space between the peripheral and central cells of the morula and becomes the hollow blastocyst

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18
Q

What happens when the fluid penetrates the morula?

A

It divides the cell into 2 main areas: the inner cells becomes the embryoblast and the flattened outer cells

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19
Q

What will the embryoblast become?

A

The embryo

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20
Q

What will the flattened outer cells become?

A

The placenta

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21
Q

What is the layer of flattened outer cells called?

A

Trophoblast

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22
Q

What happens to the zona pellucida after fertilisation?

A

It hardens after the cortical reaction and it aims to keep the ball of cells together until they develop into more complex structures. this will disappear with implantation. When the trophoblast will develop further.

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23
Q

What happens after the blastocyst has implanted into the endometrium?

A

The embryoblast will have divided into 2 layers of different cells: the epiblast (closer to the trophoblast and hypoblast

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24
Q

After it has divided into the epiblast and hypoblast what is it called?

A

The bilaminar disc

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25
Q

What is the process that puts an end to the pre embryonic stage and starts the embryonic one called?

A

Gastrulation

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26
Q

Describe Gastrulation?

A

It develops 3 layers of tissue while the embryo grows in size and fluid fills up 2 cavities in the embryo. This will create the amniotic cavity from the epiblast/ectoderm and the yolk sac from the hypoblast/endoderm.

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27
Q

What has the epiblast become?

A

ectoderm

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28
Q

What has the hypoblast become?

A

endoderm

29
Q

What was the ectoderm form?

A

skin, hair and nervous system

30
Q

How is the mesoderm form?

A

Cells from the epiblast migrate and form the mesoderm.

31
Q

What does the mesoderm form?

A

muscle, bones, connective tissue, blood vessels, blood and urogenital glands

32
Q

What does the endoderm form?

A

lining of the digestive, respiratory and urinary systems and glandular cells like the liver and pancreas

33
Q

What does the bilaminar disc become?

A

The trilaminar disc

34
Q

Describe step 1 of gastrulation?

A

cells from the epiblast will start migrating inward, creating a depression called primitive streak. This will be like a channel that will lead to more and more cells migrating between 2 layers of the bilaminar disc

35
Q

Describe step 2 of gastrulation?

A

Some cells with differentiate and become the mesoderm

36
Q

Describe step 3 of gastrulation?

A

The ectoderm cells create ad tube inside the mesoderm. The creation of the tube is known as notocordal process.

37
Q

Describe step 4 of gastrulation?

A

This tube will temporarily connect the amniotic cavity with the yolk one, to equal pressures at both sides on the embryonic disc.

38
Q

Describe step 5 of gastrulation?

A

the notochodal plat will fuse and close this connection between both cavities. This now closed tube of ectoderm cells is known as notochord.

39
Q

What does the notochord do?

A

It serves as a source of midline signals that pattern surrounding tissues as a major skeletal element of the developing embryo. it is almost like the spine of the embryo that will ensure symmetry in the development of the fetal structures. Failure in this process can lead to situations like dextocardia, where some people have their heart on the right side of the body instead of the left one.

40
Q

Describe step 6 of gastrulation?

A

At the ned of the gastrulation process we have the embryonic disc with the notochord in the middle position. At both ends of the disc the mesoderm thins forming two membranes the OROPHARYNGEAL one which develops into the mouth and the CLOACAL which develops into the genitals and anus

41
Q

In which ways does embryonic folding happen?

A

transverse and longitudinal

42
Q

What is the neural rube?

A

the embryonic structure that will develop into the brain and spinal chord.

43
Q

What is the process called where the neural tube is formed?

A

neuralation

44
Q

Why are women advised to take a folic acid supplement?

A

Because the process of the neural tube closure is mediated by folic acid.

45
Q

Why are defects more likely to happen at the brain or the sacrum?

A

Because the folding starts in the middle and goes outward

46
Q

How is the heart formed?

A

Like the neural tube the cells in the mesoderm will organise themselves into 2 tubes like 2 primitive blood vessels. These two tubes will fuse into a single one that will start beating around 22 days. The heart is the first system to start working in the heart.

47
Q

How do ventricles and atriums come about?

A

The cardiac tube needs to twist itself in the right direction. It will end up creating the ventricles and atriums. But only one of each.

48
Q

How are two ventricles and 2 atriums made?

A

The wall of the heart will grow from a structure called endocardial cushion, just in the middle of the hart that will grow and originate the hearts internal walls (septums) and the hearts valves.

49
Q

How is the digestive system formed?

A

The digestive system develops from the endoderm. With the folding of the embryo, the endoderm will end up inside the fetus.

50
Q

What happens with the digestive system by week 5?

A

The liver, gallbladder and pancreas are already developing from the primitive tube.

51
Q

what happens with the digestive system by week 10?

A

The liver grows rapidly and occupies most of the abdominal cavity so there is not enough space for the intestines to grow. This is why the intestines start to grow outside the abdominal cavity in the yolk sac and then by week 10 it will rotate and fit inside the abdominal cavity

52
Q

What happens if there is a failure in the intestines rotating inside?

A

This can cause congenital malformations. If the yolk sac doesn’t retract inside then congenital abnormalities in the abdominal wall can lead to babies being born with part of the bowel outside their body.

53
Q

How is the face formed?

A

The ectoderm, mesoderm and endoderm will come together at the oropharyngeal membrane, developing the eyes, nose the palate and the mouth. These layers will join in the middle of the face.

54
Q

When will the baby start making breathing movements?

A

week 11

55
Q

When can the baby open its eyes?

A

25 weeks

56
Q

When do the lungs reach full maduration?

A

34 weeks

57
Q

How has the endometrium prepared for implantation?

A

Around day 10 the endometrium has proliferated and it is now in the secretive phase which means it is highly vascular and has developed small pools of blood, full of nutrients ready to feed the embryo

58
Q

How does the endometrium know the prepare for implantation?

A

The embryo sends chemical signals that will prepare the endometrium to be receptive for implantation for a short period of time.. This is called the window of implantation.

59
Q

What happens after the zona pellucida dissolves?

A

The blastocyst will find its home in one of the valleys in the endometrium called a crypt.

60
Q

What happens after the embryo is completely embedded within the endometrium?

A

The endometrium is now known as the decidua, which is the maternal side of the placenta?

61
Q

What are the two layers that the trophoblast will expand to?

A 
the cytotrophoblast (inner layer)
the syncytiotrophoblast (outer)
62
Q

What will trigger the changes in the maternal body to maintain pregnancy?

A

The primitive placenta will start producing hCG. This hormone is detected in pregnancy tests

63
Q

How does the syncytiotrophoblast expand?

A

it will continue to expand into the decidua in fingerlike projections (roots of a tree). these roots are called chorionic villi and they grow around the pools of blood in the decidua that grow bugger and bigger.

64
Q

What is implantation bleeding?

A

this is bleeding that some women may experience at the beginning of pregnancy because the trophoblast breaks through the decidua

65
Q

what happens when the villi closer to the decidua grow?

A

The ones closer t o the embryo will gradually degenerate and be replaced by cells from cytotrophoblast forming chorionic membrane.

66
Q

Where does the exchange of nutrients between maternal and fetal blood?

A

the chorionic villi

67
Q

What is the amnion?

A

The part of the epiblast in contact with the cytotrophoblast will now be called the amnioblast, separated by the amniotic cavity from the bilaminar disc that will become the embryo. the amnioblast when the embryo folds this will end up surrounding the fetus, forming the most inner placenta membrane

68
Q

What happens when the bilamniar disc becomes trilaminar?

A

Part of the mesoderm will develop blood vessels through the cytotrophoblast connecting the embryo with the chorionic villi and the maternal circulation, this is the primitive umbilical chord.

69
Q

What is the placenta like at 10 weeks?

A

The placenta is functional and pretty much fully developed. During pregnancy the number of chorionic villi will continue to grow but no more complex structures will appear

Midwifery 1201 (23 decks)

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