Mini 1 Review: Early Embryology

Front 1

How do the rapid mitotic divisions of the zygote differ from ordinary cell division?

Back 1

Cells DO NOT grow in size between divisions

Front 2

~3 days after fertilization, the zygote becomes what?

Back 2

Ball of cells called MORULA

Front 3

The morula enters the uterus and becomes what?

Back 3

Blastocyst

Front 4

The blastocyst contains what two cellular masses?

Back 4

Trophoblast (outer cell mass)
Embryoblast (inner cell mass)

Front 5

What substance allows the trophoblast to become sticky and attach to the uterine epithelium

Back 5

L-selectin

Front 6

Following uterine invasion, the trophoblast differentiates into what two layers?

Back 6

syncytiotrophoblast and cytotrophoblast

Front 7

How does the syncytiotrophoblast cells proliferate?

Back 7

Mitosis of cytotrophoblast, and addition of these cells to the syncytiotrophoblast (syncytiotrophoblast cells do not divide on their own)

Front 8

Give a 5-step summary of the first week.

Back 8

1. Ovulation
2. Fertilization
3. Cleavage, morula, blastocyst
4. Zona pellucida disappears
5. Trophoblast invades superficial epithelium

Front 9

The embryoblast becomes differentiated into two distinct layers. Which day does this occur and what are the two layers?

Back 9

8th day

Epiblast (columnar)
Hypoblast (cuboidal)

Front 10

What does the bilaminar germ disc consist of? Which week of development is the embryo bilaminar.

Back 10

Epiblast (columnar)
Hypoblast (cuboidal)

2nd week.

Front 11

What is the protective membrane that begins forming on the 8th day (and will eventually surround the entire embryo)?

Back 11

Amnion

Front 12

Right after the embryo becomes completely embedded in the uterine endometrium, what is the defect (in the endometrium) closed by?

Back 12

Fibrin plug (epithelium will eventually close over the plug)

Front 13

What are lacunae?

Back 13

Spaces that appear in the syncytiotrophoblast

Front 14

How is the uteroplacental circulation established?

Back 14

syncytiotrophoblast erodes away lining of maternal sinusoids and glands, and maternal blood flows into and out of lacunae.

Front 15

What do the extraembryonic somatic mesoderm and extraembryonic splanchnic mesoderm respectively surround

Back 15

Amniotic sac and Yolk sac.

Front 16

Around the 13th day, hypoblast cell proliferation surrounds what new cavity?

Back 16

Secondary yolk sac.

Front 17

Explain the initial formation of the prechordal plate.

Back 17

Thickened hypoblast cells (become columnar)that are firmly attached to overlying epiblast.

Front 18

What connects the embryo to the trophoblast

Back 18

Connecting stalk

Front 19

What will the connecting stalk become?

Back 19

umbilIcal cord (let's say it together, umbilIIIIcal)

Front 20

Give a 7-step summary of the 2nd week of development with regards to the extraembryonic regions?

Back 20

1. Trophoblast differentiates (cytotrophoblast and syncytiotrophoblast)
2. Lacunae develop
3. syncytiotrophoblast erodes maternal sinusoids and endometrial gland
4. Primary chorionic villi form on external surface of chorionic sac
5. Implantation completed and defect closed
6. Amnion forms
7. Secondary yolk sac forms

Front 21

What are the two main developments of the embryoblast during the 2nd week?

Back 21

1. Differentiation to epiblast and hypoblast (bilaminar)
2. Prechordal plate develops

Front 22

What is placenta previa?

Back 22

Blastocyst implantation in lower segment of uterus. Will lead to severe bleeding during birth.

Front 23

What is ectopic pregnancy and where do most occur?

Back 23

Pregnancy outside the uterus occurring mostly in the uterine tube (which will eventually rupture and hemorrhage).

Front 24

What is the main feature of the 3rd week?

Back 24

GASTRULATION

Front 25

What does gastrulation consist of?

Back 25

1. Primitive streak formation
2. Notochord formation
3. Germ layers

Front 26

Explain the movement of the epiblast cells through the primitive streak (what germ layers are created)

Back 26

Ectoderm = epiblast that does not enter primitive groove

Mesoderm = between epiblast and hypoblast layers]

Endoderm = hypoblast layer

Front 27

What are the 2 locations between the epiblast and hypoblast layers that mesodermal cells do NOT migrate?

Back 27

1. Prechordal plate
2. Cloacal Membrane

Front 28

What happens at the margins of the embryonic disc

Back 28

intraembryonic and extraembryonic mesoderm become continuous.

Front 29

The mesoderm that migrates cranially of the prechordal plate becomes what

Back 29

Cardiogenic area

Front 30

How is the notochord formed?

Back 30

Cranial migration of the mesoderm from the primitive node

Front 31

By day 16, what is the outpouching of the yolk sac?

Back 31

allantois

Front 32

What do the blood vessels of the allantois become?

Back 32

umbilical arteries and veins

Front 33

What is ectodermal neurulation?

Back 33

Notochord induces overlying ectoderm to become neural plate, which will eventually fold and pinch off, yielding the neural tube (by the end of the 3rd week)

Front 34

Towards the end of the 3rd week, what causes the primitive streak to shrink and eventually disintegrate?

Back 34

Cranial pole development

Front 35

What is sacrococcygeal teratoma?

Back 35

A tumor that arises from remnants of the primitive streak.

Front 36

What is caudal dysplasia?

Back 36

Various syndromes that result from abnormal gastrulation in which migration of mesoderm is disturbed.

Front 37

About when do the anterior and posterior neuropores of the neural tube close?

Back 37

25-27th day

Front 38

What two structures influence one another, eventually forming the lens and optic cup, respectively.

Back 38

Lens placode and Optic vesicle (outpouch of diencephalon)

Front 39

What does high levels of BMP-4 cause?

Back 39

1. Ectoderm to form epidermis
2. mesoderm to form LPM and IM

Front 40

What 3 secretions from notochord inhibit BMP-4? What fn do they have other than inhibiting BMP-4?

Back 40

noggin, chordin, and follistatin

These also cause forebrain and midbrain development

Front 41

What does BMP-4 inhibition result in?

Back 41

ectodermal neuralization, thus causing ectoderm directly above notochord to become neural plate and eventually pinch off forming the neural tube.

Front 42

What are WNT-3a and FGF?

Back 42

Caudal neural plate influencers that form hindbrain and spinal cord.

Front 43

What do low levels of BMP-4 influence?

Back 43

Neural crest formation.

Front 44

Ectodermal derivatives.

Back 44

1. CNS
2. PNS
3. Sensory epithelium
4. Epidermis (hair, nails, glands)
5. Ant. pituitary gland
6. Enamel of teeth
7. Derivatives of neural crest cells

Front 45

What gives rise to somites?

Back 45

Paraxial mesoderm

Front 46

What do somites give rise to?

Back 46

1. Dermatome (dermis of skin)
2. Myotome (muscles)
3. Sclerotome (bone, cartilage)

Front 47

The space between intraembryonic somatic and splanchnic mesoderm form what?

Back 47

intraembryonic coelom

LPM --> intraembryonic somatic and splanchnic --> intraembryonic coelom

Front 48

By 8 weeks, what does the intraembryonic coelom develop into?

Back 48

1. pericardial cavity (heart)
2. pleural cavity (lungs)
3. peritoneal cavity (guts)

Front 49

Mesodermal derivatives

Back 49

1. CT, cartilage and bone (except head and neck)
2. striated, smooth, cardiac muscle
3. blood cells, heard, blood and lymph vessels
4. kidneys
5. gonads and ducts
6. cortex of adrenal glands
7. spleen

Front 50

What germ layer contributes to embryo folding?

Back 50

Endoderm

Front 51

Endodermal derivatives

Back 51

1. Epithelium of gut
2. lining of Resp. tract
3. tonsils, thyroid gland, parathyroids, thymus, liver, and pancreas
4. lining of bladder and urethra
5. lining of tympanic cavity and auditory tube
6. Epithelium and glands of guts

Front 52

What is the period of maximal sensitivity to abnormal development (which weeks)?

Back 52

Weeks 3-8

Front 53

What is vasculogenesis

Back 53

Vessels arising from blood islands

Front 54

What is angiogenesis?

Back 54

Vessels arising from existing vessels

Front 55

Lateral Plate Mesoderm Derivatives

Back 55

Intraembryonic somatic: body wall

Intraembryonic splanchnic: wall of gut

Front 56

Paraxial mesoderm derivatives

Back 56

somites [which will form dermatome (dermis), myotome (muscles), and sclerotome (CT, bone, and cartilage)]

Front 57

Neural crest derivatives

Back 57

1. CT and bones of face and skull
2. Odontoblasts (dentine)
3. Dermis in face and neck
4. Spinal ganglis
5. Adrenal medulla
6. Schwann and glial cells
7. meninges (pia and arachnoid)
8. melanocytes

Front 58

Intermediate mesoderm derivatives

Back 58

Gonads and kidneys