General Embryology 2 Flashcards
(50 cards)
1
Q
Subdivision of mesoderm
A
- Intraembryonic mesoderm proliferates between the ectoderm and endoderm
- 3 regions develop
2
Q
3 regions of mesoderm subdivision
A
- Paraaxial mesoderm
- Intermediate mesoderm
- Lateral mesoderm
3
Q
Paraaxial mesoderm
A
- Head mesenchyme
- Somites
4
Q
Intermediate mesoderm
A
- Urogenital organs
5
Q
Lateral Mesoderm
A
- Split by the formation of the intraembryonic coelom
- Somatic mesoderm (somatopleure)
- Splanchnic mesoderm (splanchnopleure)
6
Q
Somites
A
- Block-like condensations of paraxial mesoderm
- Form on the sides of the neural tube
7
Q
Somatogenesis
A
- Somite pairs begin formation on day 20
- Progresses in a cranial to caudal pattern
- 42-44 pairs form, most caudal disappear leaving 37 pairs
8
Q
First 4 pairs of somites
A
- Contribute to head
9
Q
8 pairs of somites
A
- Contribute to the cervical region
10
Q
12 pairs of somites
A
- Contribute to the thoracic region
11
Q
5 pairs of somites (two sets of 5)
A
- Contribute to the lumbar region
- Contribute to the sacral region
12
Q
3 pairs of somites
A
- Contribute to coccyx
13
Q
Somites subdivide into
A
- Sclerotome
- Dermamyotome
14
Q
Sclerotome forms
A
- Meninges
- Vertebrae
- Ribs
15
Q
Dermamyotome forms
A
- Dermis of the neck and back
- Muscle
16
Q
Dermamyotome differentiates into
A
- Dermatome
- Myotome
17
Q
Myotome splits into
A
- Epimere, located dorsally
- Hypomere, located ventrally
18
Q
Epimere gives rise to
A
- Epaxial muslces of the back
- Deep back muscles
19
Q
Hypomere gives rise to
A
- Hypaxial muscles
- Muscles of the abdominal and thoracic wall
- Limb muscles
20
Q
Lateral plate divides into
A
- Somatic mesoderm
- Splanchnic mesoderm
21
Q
Somatic mesoderm
A
- Lines body wall
22
Q
Somatopleure
A
- Somatic mesoderm + ectoderm
- Forms body wall with ectoderm
23
Q
Splanchnic mesoderm
A
- Covers endoderm
24
Q
Splanchnopleure
A
- Splanchnic mesoderm + endoderm
- Forms gut wall with endoderm
25
Coelom
- Body cavity formed by lateral folding of the embryo
26
Folding of the embryo
- Lateral folds fuse at the ventral midline
| - Forms intraembryonic coelom
27
Intraembryonic coelom eventually divides into 3 principal body cavities:
- Pericardial
- Pleural
- Peritoneal cavities
28
Craniocaudal and lateral folding
- Draw in the yolk sac (purse string)
- Close off body wall (except at umbilicus)
- Flat trilaminar embryonic disc -> cylindrical embryo
29
Ectopia cordis
- Failure of the thoracic body wall to close
30
Gastroschisis
- Failure of the abdominal body wall to close
31
Early development of the cardiovascular system
- Vasculogenesis begins during 3rd week
| - Hemangioblast cells develop in the extraembryonic splanchnic mesoderm of the yolk sac
32
Hemabgioblast development gives rise to
- Hematopoietic cell progenitors
- Endothelial precursor cells
- Endothelial cells surround blood cell aggregates (blood islands)
33
Yolk sac involved in erythropoiesis until
- About day 60
34
Vasculogenesis
- Differentiating endothelial cells organize into small capillary vessels
- Fuse to form channels
35
Vasculogenesis events
- Vascularizes the yolk sac, connecting stalk, and chorionic villi
- Vessels from extraembryonic mesoderm -> placenta -> join embryo blood vessels (from intraembryonic splanchnic mesoderm) -> establish circulation
36
Intraembryonic vessels begin to develop on
- Day 18
37
Hematogenesis does not begin within the embryo until about
- 4th week
38
2 major phases of hematopoiesis
- Embryonic (weeks 1-4)
| - Definitive (weeks 4-term)
39
Embryonic phase of hematopoiesis
- Blood cells arise from yolk sac extraembryonic mesoderm
40
Definitive phase of hematopoiesis
- Hematopoietic stem cells (from extraembryonic/intraembryonic mesoderm) -> seed the spleen, liver, and then bone marrow
41
Liver is major site of
- Fetal hematopoiesis until bone marrow takes over
42
Vasculogenesis definition
- Blood vessels arise de novo from “hemangioblasts” that develop into blood cells and vascular tubes
43
Angiogenesis
- Growth of new blood vessels from existing ones
44
Segmentation of endoderm
- Foregut
- Midgut
- Hindgut
45
Foregut
- Trachea
- Esophagus
- Stomach
- Duodenum
- Liver
- Pancreas
46
Midgut
- Small intestine
- Ascending colon
- Proximal 2/3 of transverse colon
47
Hindgut
- Distal 1/3 of transverse colon
- Descending colon
- Rectum
- Upper anal canal
48
Weeks 4-8
- Organogenetic period: all main organ systems have begun to develop
- Critical period of many organ systems
49
Teratogen exposure
- Can cause major congenital birth defects during organogenetic period (weeks 4-3)
50
Teratogens
- Agents that can disturb the development of an embryo (or fetus)
- Radiation, drugs, infections, chemicals
