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Body Logistics (Milly's) > Embryology > Flashcards

Embryology Flashcards

1
Q

Where does fertilisation normally occur?

A

Ampullary region of the fallopian tube

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2
Q

What surrounds the ovum?

A

A layer of cells called the corona radiata

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3
Q

What is the zone pellucida?

A

the thick transparent membrane surrounding a mammalian ovum before implantation

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4
Q

What lies between the corona radiata and the ovum?

A

The zone pellucida

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5
Q

What are the male and female nuclei called called just before they fuse within the ovum?

A

Pronuclei

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6
Q

What is embryonic age?

A

The time since fertilisation

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7
Q

What is gestational age?

A

The time since the last menstruation

So embryonic age plus 2 weeks

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8
Q

What is the Germinal stage of a pregnancy called?

A

The time from fertilisation to the end of the second week

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9
Q

What is the embryonic period of pregnancy?

A

The time from the the third to the end of the 8th week

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10
Q

What is the foetal period of pregnancy?

A

The time from the beginning of the ninth week to to birth at 38 weeks (38-embryonic age/40-gestational age)

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11
Q

What happens at the point of fertilisation and what type of zygote is formed as a result?

A

Immediate mitosis produces a 2 cell zygote

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12
Q

When does implantation of the blastocysts occur?

A

Day 6

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13
Q

After fertilisation the zygote begins to divide, what restricts the size of the ball of cells?

A

The zone pellucida

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14
Q

What is a morula?

A

a solid ball of cells resulting from division of a fertilized ovum

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15
Q

Within the zona pellucida the morula develops into two cell masses, what are these called?

A

Inner and outer cell mass

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16
Q

What does the outer cell mass become?

A

The trophoblast

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17
Q

What does the trophoblast become during the later stages of pregnancy?

A

The placenta and yolk sac

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18
Q

Where does normal implantation occur?

A

Superior posterior wall of uterus

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19
Q

What happens if the zygote implants in an abnormal site within the woman’s reproductive organ?

A

An ectopic pregnancy

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20
Q

During which period of pregnancy is there the most change?

A

The embryonic period (weeks 3-8)

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21
Q

What stgage of pregnancy is at the greatest risk o major congenital malformation and why?

A

The embryonic period because it is very sensitive to teratogenic agents and it is the stage where all major structures and systems are formed

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22
Q

What are the 4 main events/processes occurring in early development of a foetus following fertilisation and implantation?

A

Gastrulation
Neurulation
Segmentation
Folding

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23
Q

What appears on the epiblast in the third week of development and where exactly is this?

A

The primitive streak, pit and node appear on the dorsal surface of the epiblast

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24
Q

What forms the bilaminar disk in gastrulation?

A

Epiblast and hypoblast

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25
Q

How does the the bilaminar disc become the trilaminar disc?

A

The cells in the epiblast migrate and invaginate to form a mesoderm

26
Q

What are the layers of the trilaminar disc in gastrulation?

A

Ectoderm, mesoderm, endoderm

27
Q

Why are there two points at which there is no mesoderm?

A

So the endoderm and ectoderm are touching,

These points will become the future mouth and future anus

28
Q

List some structures that will arise form the ectoderm (2)

A

Organs and structures that maintain contact with outside world:
Nervous system
Epidermis

29
Q

List some structures that will arise from the mesoderm (4)

A 
Supporting tissues:
Muscle
Bone
Cartilage
Vascular system (including heart and vessels)
30
Q

List some structures that will arise from the endoderm (3)

A

Internal structures:
Epithelial lining of GI tract
Respiratory tract
Parenchyma of glands

31
Q

What is situs inversus?

A

When someone has complete mirror image viscera

32
Q

What can situs inversus commonly result from?

A

Immotile cilia

33
Q

When might situs inversus be an issue?

A

If there is a mixture of both normal and mirror image dispositions

34
Q

Prior to gastrulation what state is the embryonic disk in?

A

Bilaterally symmetrical

35
Q

What type of cells can you find at the node on the trilaminar disk?

A

Ciliated cells

36
Q

What do the ciliates cells present on the node of the trilaminar disk cause?

A

Leftward movement of signalling molecules which causes a sight specific signalling cascade

37
Q

How would cells migrate toward the left and right side of the trilaminar disk through the action of the ciliated cells on the node?

A

Move to left=The cilia would be leftward

Move to right= absence of any cilia movement, meaning signalling molecules aren’t moved

38
Q

Gastrulation marks the start of which period of pregnancy?

A

Embryonic period (3-8 weeks)

39
Q

Name a key structure that appears as a result of gastrulation

A

The notochord (runs straight down the mid line of the embryonic disk)

40
Q

What is neurolation?

A

The process by which we begin the develop the nervous system

41
Q

What is the notochord? (In terms of structure?)

A

A solid chord of cells that lies in the mesoderm

42
Q

What do the cells in the notochord do?

A

Release signalling molecules which directs conversion of overlying ectoderm to neurectoderm

43
Q

How does ectoderm become neurectoderm? (3)

A

Ectoderm thickens
Slipper shaped neural plate is formed
Edges of the plate elevate up and curl towards each other creating the neural tube

44
Q

During neurolation in pregnancy, what 4 types does the mesoderm differentiate into and where are the types found?

A

Paraxial mesoderm - next to the neural tube (next to the axial)
Intermediate mesoderm- lateral to the paraxial mesoderm
Somatic mesoderm- a fork of mesoderm just below the ectoderm (lateral to the intermediate mesoderm)
Splanchnic mesoderm- a fork of mesoderm just above the endoderm (lateral to the intermediate mesoderm)

45
Q

What is the space created between the somatic and splanchnic mesoderm called?

A

Intraembryonic coelom

46
Q

What does the paraxial mesoderm become?

A

Somites- body segments

47
Q

Where do the 1st somites appear?

A

1st pair appear at day 20 in the occipital region

48
Q

By the end of week 5 how many somites are there?

A

42-44 pairs

Which will eventually become 31 pairs

49
Q

What doe somites give us?

A

The building blocks of the musculoskeletal system

50
Q

How do somites initially appear? Structure.

A

As regular blocks of mesoderm cells arranged around a small cavity

51
Q

What do the cells in somites undergo in order to become precursor cells?

A

‘Organised degeneration’

52
Q

What the mesoderm undergoes ‘organised degeneration’ what are the two categories of cells formed?

A

Dermomyotome and sclerotome

53
Q

What is sclerotome?

A

Precursor of bone

54
Q

The dermomyotome (mesoderm cells in the somites of a developing embryo) separate into two groups. Name the groups and what they are precursors of

A

Dermatome- precursor for dermis

Myotome- precursor of skeletal muscle

55
Q

What are two reasons for segmentation of the body during development?

A

Guides innervation

Gives rise to repeating structures (ie ribs/vertebrae)

56
Q

What is the area of the mesoderm in the trilaminar disc that gives rise to the future heart and where would you find it?

A

Cardiogenic area- found right at the cranial end of the embryonic disc (even above the mouth!)

57
Q

During development the embryonic disc needs to be folded in order to put structures in their correct place (the heart for example). In simple terms how is this achieved?

A

The formation of the neural tube causes folding at the head and tail end of the embryonic disc
And the formation of somites caused folding of the lateral edges

58
Q

What is the head and tail folding of the embryonic disc called and why does it occur?

A

Cephalocaudal folding

Caused by the formation of the neural tube

59
Q

What is the folding of the lateral edges of the embryonic disc called?

A

Lateral folding

60
Q

What does folding of the embryonic disc achieve? (3)

A

Creates a ventral body wall
Pulls amniotic sac around embryo
Ensures structures are in the correct place

61
Q

What is the lining of the uterus called?

A

Endometrium

62
Q

What layer of the embryonic disc gives rise to the cardiac tissue?

A

Splanchnic mesoderm

Body Logistics (Milly's) (9 decks)

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