Embryology

Question 1

Embryonic period

Answer 1

First 8 weeks of prenatal period
Where major organs are formed from three primary germ layers

Question 2

Fetal period

Answer 2

Remaining 30 weeks
Organs continue to develop in size and complexity

Question 3

Tube within a tube

Answer 3

Inner tube- digestive and respiratory tracts
Outer tube- consist of muscles and bones

Question 4

Bilateral symmetry

Answer 4

Most body structures are paired with some exceptions

Question 5

What has Dorsal hollow nerve cord and what does it develop into?

Answer 5

All vertebrate embryos have a hollow nerve cord that develops into the brain and spinal cord

Question 6

What does the Notochord form into

Answer 6

Embryonic notochord forms just deep to the spinal cord and is quickly replaced by the vertebrae which makes up spinal column or backbone

Question 7

Segmentation

Answer 7

Outer tube of the body develops into segments which are repeating units of similar structures

Question 8

Oocyte

Answer 8

Female reproductive cell

Question 9

Cleavage

Answer 9

Multiple cell division of zygote

Question 10

Morula

Answer 10

Cluster of 12-16 cells formed by day 4

Question 11

What are Blastocyst and their characteristics

Answer 11

Cluster of 60 cells
Will implant in the uterus around day 6
Fluid filled cavity in the center and inner cell mass and trophoblast

Question 12

Inner cell mass

Answer 12

Cluster of cells on one side of the cavity
Will form the embryo

Question 13

In some pregnancies The inner cell mass of a single blastocyst will split into two causes

Answer 13

Identical twins

Question 14

Trophoblast

Answer 14

Layer of cells surrounding the cavity and inner cell mass
Help form the placenta

Question 15

By day 9, inner cell mass have divided into

Answer 15

Two sheets of cell known as the bilaminar embryonic disc

Question 16

The ____ form the bilaminar embryonic disc which give rise to the embryo

Answer 16

Epiblast and hypoblast

Question 17

What are Epiblast and what’s do they form

Answer 17

Cells form most of the embryo
Forms amniotic sac

Question 18

Amnion

Answer 18

Outer membrane of amniotic sac

Question 19

What is Amniotic fluid

Answer 19

Fluid that acts to cushion the developing embryo up until birth

Question 20

Hypoblast

Answer 20

Extension of the hypoblast form yolk sac

Question 21

What does Yolk sac develop into

Answer 21

Give rise to digestive tract

Question 22

Gastrulation

Answer 22

During week 3 the bilaminar embryo develops into 3 layers known as embryonic disc

Question 23

Endodrerm

Answer 23

Day 14-15 the primitive steak appears on the dorsal surface of the Epiblast
Epiblast cells migrate toward the primitive streak and displace the hypoblast to become the endoderm

Question 24

How does Mesoderm form

Answer 24

Day 16 some Epiblast cell burrow down from the primitive stream to form the mesoderm

Question 25

Ectoderm

Answer 25

Epiblast cells that remain on the dorsal surface become the ectoderm

Question 26

Neurulation

Answer 26

Development of brain and spinal cord

Question 27

Primitive node

Answer 27

Swelling at the end of the primitive streak

Question 28

What appears on day 16 and by day 18 it reaches the cranial or cephalic region of the embryo

Answer 28

Notochord

Question 29

Presence of the notochord includes the ectoderm in the dorsal midline to thicken and become

Answer 29

Neural plate

Question 30

Neuro plate starts to fold inward to become the

Answer 30

Neural groove

Question 31

Neural groove depends into a

Answer 31

Neural tube

Question 32

What does Neural tube do

Answer 32

Closest off at the neck and proceeds cranially in caudally

Question 33

Neural crest cells

Answer 33

Originate from ectoderm and form nerve cells

Question 34

Anencephaly

Answer 34

Developmental disorder when neural tube fails to close cranially The rain does not develop in the baby is either stillborn or dies Associated with low maternal folate levels

Question 35

What are the different regions of the mesoderm by the end of week 3

Answer 35

Somites, intermediate mesoderm, lateral plate

Question 36

where are Somites and what do they form

Answer 36

Area of mesoderm closest to the notochord forms segmental bulges Visible on the dorsal surface

Question 37

Intermediate mesoderm

Answer 37

Series of spherical segments attached to Somites 

Question 38

Lateral plate

Answer 38

Most lateral part of mesoderm remains unsegmented but splits into two sheets Somatic and splanchnic mesoderm

Question 39

Somatic mesoderm

Answer 39

Next to ectoderm

Question 40

Splanchnic mesoderm

Answer 40

Next to endoderm

Question 41

Coelom

Answer 41

Wedged like space the form between the two layers Will become serous cavities of the ventral body cavity

Question 42

Folding occurs during week 4 body goes from a flat disk to

Answer 42

3D cylinder shape by folding into a tube Growth of Somites causes sides of embryo to join Head and tail regions fold under expanding the brain and spinal cord

Question 43

Derivatives of ectoderm

Answer 43

Ectoderm becomes the outer tube: brain, spinal cord and skin epidermis

Question 44

Derivatives of endoderm

Answer 44

Endoderm becomes the inner epithelial lining of the inner tube: gut and respiratory tubes

Question 45

Derivatives of mesoderm

Answer 45

Somites divide into three parts

Question 46

Sclerotome

Answer 46

Produce vertebrae and ribs

Question 47

Dermatome

Answer 47

Produce skin dermis in dorsal body

Question 48

Myotome

Answer 48

Produces muscles and help form the limb buds

Question 49

Intermediate mesoderm

Answer 49

Forms kidneys and gonads

Question 50

Somatic mesoderm

Answer 50

Gives rise to skin dermis in ventral body and helps form the limb buds

Question 51

Splanchnic mesoderm

Answer 51

Gives rise to digestive and respiratory tubes, heart and blood vessels

Question 52

Around day 28/ week 5-8 what happens

Answer 52

Limb buds start to appear Head enlarges and face starts to appear Most major organs are formed during the second month of development so that any disruption during this time can result in birth defects

Question 53

When can heartbeat be detected

Answer 53

By 6-7 weeks by ultrasound

Question 54

Week 9-12 month 3 is when what happens

Answer 54

Brain continues to enlarge Trunk and limbs elongate Bone marrow starts to produce blood cells Lungs begin to develop and fetus inhaled and exhales the amniotic fluid instead of air

Question 55

When can sex be determined

Answer 55

Month 3

Question 56

Weeks 13-16 month 4

Answer 56

Bone formation begins in vertebrae Myelin start to form around nerve cells Kidneys form

Question 57

Weeks 17-20 month 5

Answer 57

Brain grows

Question 58

When does quickening start

Answer 58

Month 5

Question 59

Weeks 21-30 months 6-7

Answer 59

Lungs complete development and start to produce pulmonary surfactant at end of month 6 Premature infants born before month 6 may die from respiratory distress

Question 60

week 31-38 month 8-9

Answer 60

Skin thickens and fat accumulates Immune systems begins to develop Normal birth