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Billy Week 108 > Embryology > Flashcards

Embryology Flashcards

(115 cards)

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1
Q

How long does it take for the fertilised ovum to make it to the uterus?

A

4 days

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2
Q

How long does fertilisation take?

A

20-24h

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3
Q

When does the ZP disappear?

A

Around day 5; after the blastocyst is formed, and the cells have become embryoblasts and trophoblasts

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4
Q

What is the name of the 16ish cell mass with gap junctions?

A

Morula - around day 4

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5
Q

Why does the blastocyst form?

A

Blastomere enters uterine cavity and absorbs water forming blastocoele

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6
Q

What is blastulation?

A

Blastocyst formation from morula; morula enters uterus and sucks in water to form blastocoele; cells become trophoblasts (outside) and embryoblasts (inner, one pole)

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7
Q

What is apposition?

A

When the trophoblast cells come into contact with the endometrium, the blastocyst rotates so that the embryoblast is touching the endometrium. This triggers changes to the trophoblast ready for implantation (DECIDUAL reaction)

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8
Q

What are the main events in the 2nd week?

A

Trophoblast into 2 layers:

  • Cytotrophoblast
  • Syncitiotrophoblast

Embryoblast into 2 layers:

  • Epiblast
  • Hypoblast

Two cavities form:

  • Amniotic sac
  • Yolk sac
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9
Q

What / how does the trophoblast develop into?

A

Trophoblast cells in the area over the embryoblast differentiate; becoming the cytotrophoblast and the syncitiotrophoblast.

Syncitiotrophoblast cells fuse and lose membranes.

At this point the bilaminar disc also forms:

  • Embryoblast into epiblast and hypoblast
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10
Q

Where does the amniotic cavity form and when?

A

Day 8

Small cavity within epiblast layer forms and enlarges to become amniotic cavity.

Epiblast cells adjacent to the cytotrophoblast become amnioblasts and secrete amniotic fluid

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11
Q

What cells secrete amniotic fluid?

A

Amnioblasts, which are differentiated epiblast cells

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12
Q

When does the primary yolk sac form?

A

Second week, around day 9

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13
Q

How does the primary yolk sac form?

A

Flattened cells from the hypoblast alone with the exocoelomic membrane which lines the cytotrophoblast line a new cavity; primary yolk sac.

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14
Q

Where will the primary yolk sac be in relation to the trilaminar disc?

A

Beneath the endoderm

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15
Q

What provides nutrition for the embryo before the placenta is fully formed?

A

Primary yolk sac

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16
Q

What would cause a woman to possibly bleed a little and when?

A

Fibrinous plug over blastocyst

Around day 12

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17
Q

When is uteroplacental circulation established?

A

Aroudn day 12

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18
Q

What is the name of the space that forms at the end of the week two surrounding the primitive yolk sac and amniotic cavity? What does that mean for the other structures?

A

Chorionic cavity

Primitive yolk sac is now called secondary yolk sac

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19
Q

What will form the umbilical cord?

A

Connecting stalk, which connects the bilaminar germ disc to the trophoblast

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20
Q

What secretes hCG and from when, and why?

A

The syncitiotrophoblast from the end of the second week, secretes hCG to maintain the corpus luteum in the ovary, which secretes progesterone to maintain the endometrium

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21
Q

How is the endometrium maintained during pregnancy?

A

Syncitiotrophoblast secretes hCG

hCG maintains the corpus luteum in the ovary

Corpus luteum secretes progesterone which maintains the endometrium

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22
Q

When does the formation of the three germ layers occur?

A

At the start of the third week

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23
Q

What is the name of the formation of the three germ layers?

A

Gastrulation

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24
Q

What depression occurs on the bilaminar disc at the beginning of the third week?

A

The primitive streak

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25
What is the name for the structure at the cranial end of the primitive streak? And what is important about it?
The primitive pit Around it is the primitive node which is an important signalling area
26
What happens following formation of the primitive streak during gastrulation?
The outer cells of the epiblast start to migrate toward the primitive streak and upon arrival detach from the epiblast and slip beneath it (invagination)
27
What controls the cells' migration and specification?
Growth factor; gastrulation is a good example of patterning and morphogenesis
28
What does the epiblast form?
Ectoderm on top Mesoderm in middle Endoderm underneath
29
What does the ectoderm form?
External surfaces: - Epidermis - Nervous system - Retina
30
What does the mesoderm form?
- Muscle - Connective tissue - CVS - Blood cells - Bone - Skeleton - Reproductive organs
31
What does the endoderm form?
Internal-external surfaces: - Epithelia of resp and GI tracts - Glandular cells of GI organs
32
Which layer forms the respiratory epithelia?
Endoderm
33
Which layer forms the skin?
Ectoderm
34
Which layer forms the retina?
Ectoderm
35
Which layer forms the glands of the GIT?
Endoderm
36
Which layer forms the nervous system?
Ectoderm
37
What processes happen in the third week?
Gastrulation and neurulation
38
What is neurulation?
Formation of the brain and spinal cord
39
What forms underneath where the primitive streak was?
The notochordal plate; cells differentiate and migrate cranially to form the notochordal plate within the mesoderm
40
How does the notochord form and when?
Around day 17 (third week) After gastrulation; cells under where the primitive streak was differentiate and migrate cranially to form the notochordal plate. The cells detach from the endoderm layer and anastomose to form a solid rod; the notochord
41
What is the function of the notochord?
Forms parts of the IV discs in adults Sends out chemical signals to determine the longitudinal axis of the embryo in embryogenesis ("induction")
42
What structure is important in setting out the embryological axis?
Notochord is important in INDUCTION
43
Why / how does the neural plate form?
The mesoderm and notochord induce a change in the ectoderm (thickens) The neural plate enlarges at the cranial and caudal end staying in the middle quite narrow; still a plate Then the edges thicken and the plate deepens to form the neural groove, then the folds fold in on each other and form the neural tube
44
When does neurulation occur (beginning with neural plate formation)
Day 19 - 28
45
What are the names of the open cranial and caudal ends of the neural tube and when do they close?
Neuropores Day 27
46
Where do neural crest cells from from?
Edges of neural tube
47
What do the neural crest cells do?
Detach themselves from the neural groove to form discrete aggregations which migrate to form different parts of the CNS and PNS
48
What forms from neural crest cells?
Glial cells Schwann cells Meninges
49
What cells will become the neurons of the grey matter?
Neuroblasts
50
Which zone of the neural tube becomes the spinal cord white matter?
Marginal zone
51
What is the name of the structure the nerves form where the spine is longer?
Cauda equina
52
What does the forebrain develop from?
Prosencephalon
53
What does the midbrain develop from?
Mesencephalon
54
What does the hindbrain develop from?
Rhombencephalon
55
When do the three primary brain vesicles form and what are they?
Fourth week Pros, Mes, Rhomb
56
When do the five secondary brain vesicles form?
Week 5 Prosencephalon becomes: - Telencephalon (c. hem) - Diencephalon (thal/hypothal) Mesencephalon Rhombencephalon becomes: - Metencephalon (pons and cerebrellum) - Myencephalon (medulla)
57
What does the cerebral hemisphere from from?
Telencephalon
58
What does the thalamus form from?
Diencephalon
59
What does the hypothalamus form from?
Diencephalon
60
What does the pons develop from?
Metencephalon
61
What does the midbrain develop from
Mesencephalone
62
What does the cerebellum develop from?
Metencephalon
63
What does the medulla develop from?
Myencephalon
64
What does the prosencephalon turn into
Telencephalon | Diencephalon
65
What does the mesencephalon develop into
It stays as mesencephalon
66
What does the rhombencephalon develop into?
Metencephalon | Myencephalon
67
What does the lumen of the neural tube turn into?
The ventricular system and the central canal in the spinal cord
68
When does the gut tube form?
At roughly the same time as neurulation (end of third week to end of fourth week)
69
Which layer forms the gut tube?
The endoderm
70
Which layer forms the neural plate?
Ectoderm
71
Which part of the gut tube is still in contact with the yolk sac?
The midgut
72
What is the name for the connection between the gut tube and the yolk sac?
Vitelline duct
73
The glandular cells (parenchyma) of the liver and pancreas are formed from which layer?
The endoderm
74
The connective tissue and smooth muscle of the pancreas and liver and derived from which layer?
The mesoderm
75
Gut tube epithelia is from which layer?
Endoderm
76
What happens to the yolk sac as embryogenesis continues?
It shrinks as nutrients are used up by the embryo
77
Why does the gut tube end up sustpended in the primitive peritoneal cavity?
The parietal and visceral mesoderm layers fold and become continuous to form the dorsal mesentery
78
Where is the allantois and what will it become?
The connecting stalk The umbilical cord
79
What is the name of the primordial mouth
Stomodeum
80
What is the name of the primordial anal pit
Proctodeum
81
What is the name of the membrane which separates the proctodeum from the outside work
Cloacal membrane
82
what does the greater omentum form from?
The dorsal mesentery (dorsal mesogastrium)
83
What does the lesser omentum form from
The liver is within the mesogastrium and as it grows, separates it into two The part ventral to the liver becomes the falciform ligament The part dorsal to the liver becomes the lesser omentum
84
When is the gut tube formed as a closed tube by
The end of week 4
85
When is the growth period of the oesophagus?
Weeks 4 through 7
86
What happens in the 8th week regarding oesophageal development?
Rapid proliferation of the epithelium followed by recanalisation
87
What are potential complications of the oesophagus developing?
``` Blockage = atresia Stenosis = narrowing of the lumen ```
88
What happens with the development of the stomach?
Start of 6th week Enlarges ventrodorsally Rotates clockwise Left and right vagus become anterior and posterior vagi Ventral mesogastrium becomes lesser sac Dorsal mesogastrium becomes greater omenstum
89
Stomach development
Week 5-6 Grows rapidly Pulled round by stomach rotation Epithelia proliferate Recanalisation
90
Which bud does the liver and gallbladder form from
Hepatic diverticulum
91
When is the liver producing bile?
From week 12 - meconium becomes dark green
92
Why is part of the pancreas retroperitoneal and some intraperitoneal?
Part is formed within the dorsal and part within the ventral mesentery; so form dorsal and ventral pancreatic buds When the stomach raotates it brins the buds togther and allows them to join; they form the major duodenal papilla
93
What does the falciform ligament form from
Ventral mesentery (septum transversum)
94
When does the pancreas start to produce insulin
Around 10 week
95
When does the pancreas start to produce glucagon
Around 15weeks
96
What way does the small intestine rotate, and when?
It grows and rotates counter-clockwise, a total of 270 degrees, in weeks 10-12
97
What is the name of the terminal part of the hindgut?
Cloaca
98
What does the urorectal septum do?
Small piece of connective tissue in the cloaca grows toward the cloacal membrane to split the cavity into two
99
What are the two openings formed when the cloacal membrane ruptures, and when?
Week 7 Anal oepning dorsally Urogenital opening ventrally
100
Why might you see bile in the vomit of a baby?
Duodenal atreia; common in downs and prems
101
When does duodenal formation occur
Weeks 5-7
102
What are differences between the alveoli before and after birth?
Foetal: - thick walled - smaller lumen Adult - thin walled - larger lumen
103
What is the first stage of lung development?
Embryonic 3-5w Bronchial buds from Branching
104
What is the second stage of lung development?
Pseudoglandular 6-16w Branching
105
What is the third stage of lung development?
Canalicular 17-24w Terminal bronchioles develop
106
What is the fourth stage of lung development?
Saccular 25w to term Primitive alveoli develop
107
What is the fifth stage of lung development?
Alveolar 8m into childhood Morre alveoli form; maturation of alveoli
108
What separates the early foregut tube from the ventral lungbud?
Tracheooesophageal septum
109
When do type II pneumocytes appear?
Pseudoglandular stage
110
When do type I pneumocytes appear?
Canalicular stage
111
When is surfactant produced?
Saccular stage
112
What would a lack of surfactant cause?
Atelectasis (total lung collapse) Respiratory distress syndrome Steorids +/- surfactant therapy via ET tube
113
Oesophageal atresia
Incomplete spearation of trachea from foregut Often leads to polyhydramnios as foetus doesnt swallow amniotic fluid Surgical
114
Tracheosophageal fistulas
Incomplete separation of trachea from foregut
115
Hiatal hernia
Can lead to maldevelopment of left lung which can cause death of foetus!! (not right due to liveR)

Billy Week 108 (2 decks)

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