Embryology- Neurulation And Placentation

Front 1

Neural induction.

What structure produces the induction signals?

Back 1

The definitive notochord.

Front 2

Where does the neural tube form from?

Back 2

It forms from the neural folds (from neuroectoderm).

Front 3

What are the three expanded regions of the cephalic region of the closed neural tube?

Back 3

Prosencephalon aka forebrain (divided into telencephalon and diencephalon).
Mesencephalon aka midbrain.
Rhombencephalon aka hindbrain (divided into rhombomeres)

Front 4

What gives rise to all the CNS and neuroglia?

Back 4

Neuroepithelium of the neural tube.

Front 5

Where do PS ganglia originate from?

Back 5

They all originate from neural crest cells at the trunk region.

Front 6

What are the three origins of the dermis?

Back 6

The dermatome (dorsal portion of body).
Somatic mesoderm (ventral portion of body).
Neural crest cells (face and neck)

Front 7

Where do ectodermal placodes originate from?

Back 7

Neuroepithelial cells of the telencephalon. (they DO NOT give rise to neural crest cells! Instead, they give rise to ectodermal placodes).

Condensations of ectodermal cells within the surface ectoderm adjacent to the neural tube.

Front 8

Optic placode

Back 8

Lense of the eyes.

Front 9

Olfactory (nasal) placodes.

Back 9

Sensory epithelium of the nose.

Front 10

When does embryo folding occur?

Back 10

At the fourth week. The embryonic disc will acquire a cylindrical shape.

Front 11

List the structures of the head region of the bilaminar embryo- before and after sagittal folding.

Back 11

Head bilaminar embryo before sagittal folding:
Septum transversum, developing heart/intraembryonic cavity, buccopharyngeal membrane.

After folding:
Forebrain, stomodeum/buccopharyngeal membrane, heart/intraembryonic cavity, septum transversum.
The endoderm folds to form the foregut.

It is easier to draw out the structures before fording and extrapolate from there.

Front 12

List the structures of the tail region- before and after sagittal folding.

Back 12

Before folding:
Connecting stock, allantois, cloacal membrane, developing spinal cord.

After folding: Spinal cord, cloacal membrane, allantois, and connecting stock.
The endoderm folds to creade the hindgut.

Front 13

What forms the umbilical cord?

Back 13

Vitelline duct (whcih becomes associated with the allantois and connecting stalk)

Front 14

Intraembryonic coelom

Back 14

The space created as the lateral mesoderm is split. Surrounded ventrally by splanchnopleure, and dorsally by somatopleure.

Becomes the pericardial cavity anteriorally, and the peritoneal cavity posteriorally/

Front 15

What are the fetal components of the placenta? What are the maternal component?

Back 15

Fetal components:
Amniotic cavity: env. control, and protection.
Placenta (derived from the chorion): nutrition, respiration, ENDOCRINE function, excretion.

Maternal compopnents:
Decidua basalis: forms basal plate and remains with placenta at parturition.
Other maternal parts: D. capsularis, D. Parietalis, and D. capsularis (degenerates)

Front 16

What are the two parts of the chorion (at the placena)?

Back 16

Chorion frondosum: villous chorion- fetal portion of placenta.

Chorion laeve: smooth (villus and vasculature are lost), and stretches over expanded amnion.

Front 17

What happens with the placental barrier with time?

Back 17

It lessens with time. Cytotrophoblast layer is lost.

Front 18

Chorionic villi

Back 18

Cytotrophoblast on basal lamina, fuses to syncytiotrophoblast

Front 19

Decidua basalis is mainly what type of trophoblast?

Back 19

Cytotrophoblast.
Anchoring villi, and extravillous trophoblast.

Front 20

What is the primary source of amniotic fluid?

Back 20

Diffusion of fluid across placenta from maternal blood.

Front 21

What are the mechanisms to cross the placental barrier?

Back 21

Simple diffusion, facilitated diffsion, active transport, pinocytosis, breaks.

Front 22

How is CO2 and O2 transported across the placenta?

Back 22

They diffuse freely due to the differences in partial pressure.

Front 23

How do drugs cross the placenta?

Back 23

Most cross by simple diffusion.

Front 24

What are the hormones produced by the placenta?

Back 24

hCG
Human placental lactogen
Progesterone
Estrogen

Front 25

What does the placenta look like for dizygotic twins? For monozygotic twins?

Back 25

Dizygotic twins: separate placentas- two amnions, and either two or fused CHORIONS.

Monozygotic twins: one placenta- two amniotic sacs, and ONE CHORIONIC SAC. In 1% of cases, we may have one amnion and one chorion, which may lead to conjoined or parasitic twins.

Front 26

What layers are present at the end of week 3?

Back 26

Ectoderm, endoderm, and mesoderm.

Front 27

What is the first indication of gastrulation in an embryo?

Back 27

Formation of primitive streak.

Front 28

When a woman misses a period and discovers she is pregnant, what week pf development is the the embryo found in?

Back 28

Week 3.

Front 29

What trilaminar embryonic structure gives rise to the kidneys and gonads?

Back 29

Intermediate mesoderm.

Front 30

Decidua parietalis

Back 30

All portions of the endometrium other than the site of implantation.

Front 31

During the later stages of pregnancy, the maternal blood is separated from the fetal blood by what?

Back 31

Syncytiotrophoblast and fetal endothelium.

Front 32

What are the maternal and fetal components of the placenta?

Back 32

Decidua basalis and villous chorion.

Front 33

What is in the intervillous space of the placenta?

Back 33

Maternal blood.

Front 34

What is the normal amount of amniotic fluid at term?

Back 34

1L

Front 35

What is the placental component of a dizygotic twin?

Back 35

Two placentas, two amniotic sacs, two chorions.

Front 36

The anterior fontanelle is usually closed by what age?

Back 36

2 years.