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42 Cards in this Set

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Which direction in embryologic terms is Rostral?
Towards the top of the vertical axis.
Define Caudal direction.
Caudal refers to "inferior" embryologic direction (defined by the neural axis), with the coccyx being the most caudal structure.

Early Embryology, slide 14
Name 3 tissues that derive from the Ectoderm.
Choose from:
*CNS; *PNS; Melanocytes; Glands; Pituitary Gland; Teeth Enamel; Adrenal Glands; Eyes

*Most important to remember
Early Embryology, slide 23
What structures are formed from the Mesoderm?
All internal, non-hollow organs:
Bone, Muscle, Kidneys, Heart, Blood, Gonads, Serous Membranes.

Early Embryology, Slide 23.
Name 3 structures derived from the Endoderm.
Choose from:
GI endothelium; Respiratory tissue; Thyroid; Parathyroids; Bladder; Inner Ear.

Early Embryology, slide 23
What is Ectodermal Dysplasia?
Over 400 conditions with patterns of ectodermal tissue malformation.
e.g. X-linked hypohidrodic ectodermal dysplasia which presents with:
1) Hypohydrosis; 2) Hypodontia; 3) Hyptrichosis

Early Embryology, slide 24
When does Gastrulation occur?
Begins 3 weeks post-fertilization.

Early Embryology slide 5.
What is Gastrulation?
Process in which the cranial/caudal and left/right axes are defined.

Following gastrulation, we have the 3 axis necessary to give positional information.

Early Embryology slide 5.
What is Neurolation?
Overlying ectoderm thickens into the neural plate;
Edges of the neural plate form the neural fold.
At the dorsal edge of each fold, a group of cells pinches off to form the Neural Crest.

-EarlyEmbryology Slide 26
When does an embryo implant?
Begins on day 6 and is completed on day 9.
When does the neural tube close?
The Cranial neuropore closes on Day 25.
The Caudal neuropore closes on Day 27.
What cell type is indicated by the purple arrow in this 9-day human blastocyst?

What does it become? What tissue lineage does it come from?
Epiblast.

It becomes the mature fetus and amniotic ectoderm.
It is derived from the Embryoblast.
What cells are indicated by the purple arrow on this 9-day blastocyst?
Hypoblast
What cells are indicated by the purple arrow on this 9-day blastocyst?
Synctiotrophoblast
What cells are indicated by the purple arrow on this 9-day blastocyst?
Cytotrophoblast
On this diagram of a 13-day blastocyst, what cavity is indicated by the purple arrow?

What was it called only a few days earlier?
Secondary (Definitive) Yolk Sac.

Primitive Yolk Sac.
On this diagram of a 13-day blastocyst, what cavity is indicated by the purple arrow?
Chorionic Cavity (Extraembryonic Cavity)
On this diagram of a 13-day blastocyst, what cavity is indicated by the purple arrow?
Amniotic Cavity
Where are Germ Cells derived from?
They come from the secondary yolk sac.
The second week of development is called the "Week of 2's." Why? (4 reasons)
1) The Trophoblast differentiates into 2 layers: Cytotrophoblast and Syncytiotrophoblast.
2) The Embryoblast forms 2 layers: Epiblast and Hypoblast.
3) 2 cavities form: Amniotic and Yolk sac cavities.
4) The Extraembryonic Mesoderm splits into 2 layers, the Somatic and Splanchnic layers.
Is this cross-sectional diagram of a Meningocele or a Meningomyelocele?
Meningomyelocele.
See the different types of NTDs, from Langman's P.296
What is the Notochord derived from?
What does it become?
Mesoderm.
Vertebral column
Diagram of 17-day embryo from Langman p. 54
What are some embryonic synonyms of "Cranial?"
Cephalic, Rostral, "Superior"
Give an example of Ectodermal Dysplasia.
X-linked Hypohidrotic Ectodermal Dysplasia, with symptoms of:
1) Hypohydrosis (dec. sweating); 2) Hypodontia (dec. teeth); 3) Hypotrichosis (dec. hair)
Are these twins mono or dizigotic?

When would the embryos have separated?
Monozygotic (monochorionic, monoamniotic)

Separation of embryonic cells after amniogenesis (from 7 to 14 days) results in single placenta with one amnion.
After 14 days, twins would have been conjoined.
When does the Embryonic Period end?

What happens after?
Embryonic period: First 8 weeks post fertilization.

After: Fetal period until birth.
At what age is an embryo most sensitive to teratogenic exposure?
Weeks 3 to 8 post fertilization.
Describe Gastrulation.
During the third week of embryonic development cells from the Ectoderm migrate through the Primitive Streak and form the Mesoderm and the Endoderm, resulting in the three germ layers of the embryo.
What's so special about the Buccopharyngeal (Oropharyngeal) Membrane?
It's one of two areas (along with the Cloacal Membrane) where the Ectoderm and Endoderm are never separated by the Mesoderm.

It forms the Mouth and Nares
Cloacal means "sewer"
It forms the Cloaca-urinary and anal orifices.
What's the first anatomical evidence of segmentation?
The formation of Somites.
The first ones form near the centre of the embryo and new ones proceed in both the cranial and caudal directions.
Identify the structure indicated by the purple arrow and the yellow arrow in the 16-day embryo.
Purple: Primitive Node.
Yellow: Primitive Streak.
Name two possible locations for ectopic pregnancies.
Uterine Tube and Rectouterine Pouch.
What are three Vitelline abnormalities?
1. Meckel's diverticulum
2. Vitelline Cyst
3. Vitelline Fistula
What are three potential Urachal abnormalities.
1. Urachal cyst
2. Urachal sinus
3. Urachal fistula
Name four abnormalities of the terminal hindgut and cloacal membrane.

How can you screen for them?
A. Urorectal fistula
B. Rectovaginal fistula
C. Rectoperineal fistula
D. Imperforate anus.

Examine newborn for normal anus.
What is the embryologic source of the ureters?
An outpouching of the mesonephric duct.
On the 3-mm (~25 day) embryo, what embryonic structure is indicated by the red arrow?

What germ line does it derive from? What does it become in a mature fetus?
What problems can occur with improper development?
Respiratory diverticulum.

From Endoderm, begins as a portion of the foregut. It becomes the respiratory tract.
If it doesn't separate properly from the foregut, can have tracheal-esophageal fistula (food and fluid going into the lungs).
In this 3mm (~25 day) embryo, what structure is indicated by the purple arrow?
What does it become? How?
Liver bud.

The liver bud is endoderm, an outpouching from the foregut. It grows into the Septum Transversum (mesoderm, the brown bit around the bud).
The final liver is derived from both the endoderm and mesoderm.
Endoderm(liver bud) -> Hepatoblasts and bile system
Mesoderm -> Supporting Stroma
In this 3mm (~25 day) embryo, what structure is indicated by the green arrow?

What is a common abnormality of this structure's development?
What is the radiological sign of that abnormality?
Duodenum.

Duodenal atresia.
Double-Bubble sign.
In this 3mm (~25 day) embryo, what structure is indicated by the yellow arrow?

What are some possible embryonic remnants of this structure?
Midgut.

Meckel Diverticulum or Vitelline abnormalities (Ligament, cyst, Fistula)
In this 3mm (~25 day) embryo, what structure is indicated by the white arrow?

What is a conserved remnant of this structure?
Hindgut.

Median Umbilical Ligament
What is bilious vomiting an indication of. What does it look like?
Is it an emergency?
Indication of malrotation.
Green.
Yes, medical emergency; can result in ischemia of the midgut.