Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Year 2 Development > Early Fetal Development > Flashcards

Early Fetal Development Flashcards

1
Q

What is fertilisation age?

A

measured from the time of fertilization (assumed to be +1 day from last ovulation)
difficult to know time of fertilization exactly (unless IVF)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is another name for fertilisation age?

A

Conceptual

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why is fertilisation age not very practical?

A

Difficult to measure in practice

Variaiblity in time between intercourse and fertilisation in natural conception
Can be inferred if we know time of ovulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is gestational age?

A

calculated from the time of the beginning of the last menstrual period (LMP)

Determined by fertilization date (+14 days) if known, or early obstetric ultrasound and comparison to embryo size charts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is carnegie stage?

A

23 stages of embryo development based on embryo features not time
Allows comparison of developmental rates between species
Covers the window of 0-60 days fertilization age in humans

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the division of pregnancy?

A

Embryogenic stage
Embryonic stage
Fetal stage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

When is the embryogenic stage?

A

14-16 days post-fertilization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the purpose of the embryogenic phase?

A

establishing the early embryo from the fertilized oocyt
e
Determining two populations of cells:

pluripotent embryonic cells (contribute to fetus)

Extraembryonic cells (contribute to the support structures eg placenta)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

When is the embryonic stage?

A

16-50 days post fertilisation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What happens during the embryonic stage?

A

Establishment of the germ layers and differentiation of tissue types
Establishment of the body plan

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

When is the fetal stage?

A

50-270 days post-fertilisation

8-38 weeks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens during the fetal stage?

A

Major organ systems now present
Migration of some organ systems to final location
Extensive growth and acquisition of fetal viability (survival outside the womb)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the first trimester comprised of?

A

Embryogenic stage

Embryonic stage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

When does the change from embryo to fetus occur?

A

Roughly at the end of the first trimester

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the developmental trajectory for the first few days of life?

A 
Ovulated oocyte
Zygote
Cleavage state embryos (2-8 cells)
Morula (16+cells)
Blastocyst (200-300 cells)

All occurs whilst travelling along the fallopian tube towards uterus

Zone pellucida present for all stage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the first developmental event?

A

Maternal-toZygotic transition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the Maternal-toZygotic transition?

A

Occurs at the 4-8 cell stage

Embryotic genes take over - begin transcription

Embryo increases protein production

Maturation of organelles (mitochondria and golgi)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How does the cell divide prior to Maternal-toZygotic transition?

A

No genes are transcribes

Divisions dependent on maternal mRNA and proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the second major event?

A

Compaction

Occurs at 8 cell stage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What happens in compation?

A

Cells start pressing up against the zona pellucida

Go from spherical to wedge-shaped

Outer cells connect to each other through tight gap junctions and desmosomes

Forms barrier to diffusion between inner and outer embryo

Outer cells become polarised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What does compaction result in?

A

2 distinct cell types in the early embryo

  1. Inner
  2. Outer
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is the zona pellucida?

A

Hard protein shell inhibiting polyspermy and protects early embryo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the inner cell mass?

A

Pluripotent embryonic cells that will contribute to the final organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the trophectoderm?

A

Extra-embryonic cells that contribute to the extraembryonic structures that support development

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the balstocoel?

A

Fluid-filled cavity formed
osmotically by
trophoblast pumping
Na+ ions into cavity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is hatching?

A

Escape of the blastocyst from the zona pelluida shell

Essential for implantation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How does hatching occur?

A

Enzymatic digestion

Cellular contractions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What are the peri-implantation events?

A

Further differentiation of the embryo

  1. Trophectoderm lineage separates
  2. Inner cell mass separates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What does the trophoblast separate to?

A

trophoblast cells fuse to form syncitiotrophoblast

Syncitiotrophoblast invasion destroys local maternal cells in the endometrium
Creates interface between embryo and maternal blood supply

cytotrophoblast cells remain individual to provide source of syncitiotrophoblast cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What does the inner cell mass separate to?

A

epiblast: from which the fetal tissues will be derived.
hypoblast: which will form the yolk sac (extraembryonic structure)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is the yolk sac important for?

A

Gut development

Early haematopoesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What occurs at day 12+?

A

Bi-laminar embryonic disc formation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is Bi-laminar embryonic disc formation?

A

Some cells become separated from the epiblast by the formation of a new cavity – the amniotic cavity.

These amnion cells will contribute to the extra-embryonic membranes.

This leaves a two-layer disc of epiblast and hypoblast, sandwiched between cavities.

Embryo is now ready for gastrulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Why is it called bi-laminar?

A

Looks like two discs stitting on top of eachother

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What does syncitiotrophoblast secrete?

A

hCG

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What forms the basis of pregnancy testing?

A

Detection of beta hCG subunit in blood/urine is basis of pregnancy testing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What is gastrulation?

A

The process whereby the bilaminar embryonic disc undergoes reorganisation to form a trilaminar disc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What happens during the third week of developement?

A

Differentiatied to establish three primary germ layers

39
Q

What is the primitive streak?

A

Thickened structure forms along the mid-line at the caudal end
Defines major body axis of the embryo

40
Q

What occurs to the primitive streak at the cranial end of the embryonic disc?

A

Expands to form a primitive node

Containing a circular depression - primitive pit

41
Q

What happens to the primitive pit?

A

Depression continues along the midline of the epiblast, towards the caudal end

Forms the primitive groove

42
Q

What is invagination?

A

Cells of the epiblast migrate inwards towards to streak

Detach from the epiblast

Slip beneath it into the interior of the embryo

43
Q

What do the first invaginated cells do?

A

Invade the hypoblast and displace its cell

Forms new proximal layer - the definitive endoderm

44
Q

What happens by day 16?

A

Majority of hypoblast have been replaced

Remaining cells of the epiblast are referred to as the ectoderm

45
Q

What does the ectoderm form?

A

Most exterior, distal layer

46
Q

What do the other invaginated cells do?

A

Remain in the space between the ectoderm and definitive endoderm - form a germ layer

the mesoderm

47
Q

What are the three germ layers?

A

Ectoderm (upper)
Mesoderm
Definitive endoderm

48
Q

What organs are formed by the ectoderm?

A

CNS and neural tract
Skin epithelia
Tooth enamel

49
Q

What organs are formed by the endoderm?

A

GI tract
Liver, pancreas
Lung
Thyroid

50
Q

What organs are formed by the mesoderm?

A

Blood (endothelial cells, red and white blood cells)
Muscle (smooth, skeletal and cardiac)
Gonads, kidneys and adrenal cortex
Bone, cartilage

51
Q

What is the first major event after gastrulation?

A

Notochord formation at day 13

52
Q

What is the notochord?

A

rod-like tube structure formed of cartilage-like cells

Forms along the embryo midline, under the ectoderm

53
Q

What is the function of the notochord?

A

Acts as a key organizing centre for neurulation and mesoderm development
Releases growth factor signals

54
Q

What is neurulation?

A

Process of CNS formatuon

55
Q

How does the notochord organise neurulation?

A

Through controlling the neural plate

56
Q

What is the neural plate?

A

Area of ectoderm on top pf embryo
Thickened
Notochord directs neural plate to form neural tube

57
Q

What does the neural plate do?

A
  1. Part of neural plate to invaginate to form neural groove

2. Creates two ridges (neural folds) running along the cranio-caudal axis

58
Q

What happens after neural fold formation?

A

Neural folds move together over neural groove

Ultimately neural folds fuse, forming a hollow tube

59
Q

What happens to the neural tube?

A

Neural tube overlaid with epidermis (ectoderm derived)
Initially open at each end
Must close for formation of brain structures

60
Q

When does the neural tube close at the head end?

A

day 23

61
Q

When does the neural tube close at the tail end?

A

27

62
Q

What conditions are caused by failure of neural tube closure?

A

Anencephaly

Spina bifida

63
Q

What is anencephaly?

A

absence of most of the skull and brain

arises from failure to close at the head end (1/10,000 births)

64
Q

What is spina bifida?

A

open neural tube at birth, usually lower spine due to failure to close tail end– varying severity
(0.4-5/1000 births)

65
Q

What are the main features of the neural crest cells?

A

endoderm derived, plastic and migrate extensively during development
give rise to a variety of cell types

66
Q

How are the neural crest cells classified?

A

By where they end up in the embryo

67
Q

What are the different neural crest cells?

A

Cranial
Cardiac
Trunk
Vagral and Sacral

68
Q

What do the cranial crest cells form?

A

cranial neurones, glia, lower jaw, middle ear bones (ossicles), facial cartilage

69
Q

What do the cardiac crest cells form?

A

aortic arch/pulmonary artery septum, large arteries wall musculoconnective tissue

70
Q

What do the trunk crest cells form?

A

dorsal root ganglia, sympathetic ganglia, adrenal medulla, aortic nerve clusters, melanocytes

71
Q

What do the vagral and sacral crest cells form?

A

dorsal root ganglia, sympathetic ganglia, adrenal medulla, aortic nerve clusters, melanocytes

72
Q

What do defects of neural crest migration/specification lead to?

A

diverse birth defects including:
pigmentation disorders
deafness
cardiac and facial defects failure to innervate the gut

73
Q

What is the stage after neuralation?

A

Somitogenesis

74
Q

What is somitogenesis?

A

formation of somites

75
Q

What are somites?

A

arise from paired blocks of paraxial mesoderm flanking the neural tube and notochord

76
Q

What happens to paraxial mesoderm?

A

Blocks of paraxial mesoderm condense and bud off in somite pairs

One of each pair either side of the neural tube.

Pairs of condensed mesdoderm = somites

77
Q

Where does somitogenesis occur?

A

at the head end and progresses down the long axis of the embryo

78
Q

What is the rate of budding?

A

species-specific, as is the number of pairs

Humans 1 pair/90 min, 44 pairs

Week 4: 3-4 pairs
Week 5: around 30 pairs

79
Q

What do somite pairs look like on embryo imaging?

A

Chevron structures

Blocks lining up along the back of the embryo

80
Q

What types of embryonic tissue to the somites give rise to?

A

Sclerotome

Dermomyotome

81
Q

What will the sclerotome give rise to?

A

vertebrae and rib cartilage

82
Q

What does the dermomyotome divide into?

A

Dermatome: gives rise to dermis of the skin, some fat and connective tissues of neck and trunk
Myotome: forms the muscles of the embryo

83
Q

From what does the primitive gut arise?

A

around Day 16 from

Ventral folding: where the head and tail ends curl together

Lateral folding: where the two sides of the embryo roll

This pinches off part of the yolk sac (At top) to form the primitive gut

84
Q

What subsequently happens to the primitive gut?

A

patterned into foregut, midgut and hindgut

85
Q

What does the foregut give rise to?

A

esophagus, stomach, upper duodenum, liver, gallbladder, pancreas

86
Q

What does the midgut give rise to?

A

lower duodenum and remainder of small intestine, ascending colon and first two-thirds of transverse colon

87
Q

What does the hindgut give rise to?

A

last third of the transverse colon, descending colon, rectum and upper anal canal

88
Q

What are the features of heart development?

A

Begins as tube of mesoderm around day 19, beating and pumping blood commences around day 22
Fetal heartbeat detectable from ~6 weeks gestational age

89
Q

What are the features of lung development?

A

Arise from the lung bud, and endodermal structure adjacent to the foregut, in the 4th week of development

Lung bud splits into two at the end of the 4th week, and progressively branches through development.

90
Q

What do the gonads form from?

A

Forms from mesoderm as bipotential (i.e. not committed to testis or ovary) structures known as gonadal/genital ridges

91
Q

What are the features of XY embryo development?

A

presence of SRY gene on Y chromosome directs gonadal cells to become Sertoli cells, triggering testis development, Leydig cell formation and testosterone production

92
Q

What are the features of XX embryo development?

A

absence of SRY leads to gonadal cells adopting a granulosa cell fate and ovary development, requires reinforcement by FOXL2

93
Q

What is RIF?

A

Recurrent implantation failure

Year 2 Development (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions