Embryology week 17

Question 1

What are teratogens + examples

Answer 1

Agents that may cause cogenital anomalies when the embryo is exposed to them during the 4 - 8 weeks
Rubella virus, thalidomide , Warfarin

Question 2

When does the embryo fold

Answer 2

Fourth week

Question 3

Name the three phases of embryonic development

Answer 3

Growth
Morphogenesis
Differentation

Question 4

Explain what happens in the 3 phases of human development

Answer 4

Grwoth- cell divison
Morphogenesis- development of the shape of the organ and whole body
Differentiation(maturation) - the formation of tissues and organs that are capable of performing specialsied tissue functions -

Question 5

When the embryo folds what exaclty folds

Answer 5

cranial ends, caudal ends and sides

Question 6

Explain what happens when the head folds
-Neural folds
-Septum transversum

Answer 6

• The neural folds have thickened to form the primdorium of the brain
  -Septum transversum, primodrial heart and move onto the ventral surfaceof the embryo

Question 7

Where does the foregut lie

Answer 7

• Between the brain and heart

Question 8

What happens to the endoderm of the umbilical vesicles during head folding

Answer 8

• Endoderm of the umbilical vesicle is incorporated into the embryo as the foregut

Question 9

What seperates the foregut from the stomodeum of the mouth

Answer 9

Oropharyngeal membrane

Question 10

What changes occur to the septum transversion in relation to the heart before and after head folding occurs

Answer 10

Before the septum transversum lies cranially to the heart but after it lies caudally

Question 11

Explain what happens to the tail during the folding of the embryo

Answer 11

The tail folds and extends over the cloacal membrane, which will later become the anus

Question 12

What does the hindgut develop into

Answer 12

colon and rectum

Question 13

How is the cloaca formed starting from the hindgut

Answer 13

-Hindgut expands to form the cloaca

Question 14

Explain how the primitive streak changes before and after folding

Answer 14

Before folding the primtive streak is cranial but after folding it is moves caudal

Question 15

During folding where does the connecting stalk move

Answer 15

To the ventral surface of the embryo

Question 16

During folding what is the allantois incorporated into

Answer 16

• Emrbyo

Question 17

What does the folding of the sides of the embryo produce

Answer 17

• Right and left lateral folds

Question 18

When is the midgut formed

Answer 18

When the embryo folds in the horizontal plane

Question 19

During the embryo folding in the horizontal plane, What is the endoderm germ layer incorporated into
- `

Answer 19

incorporated into the embryo as the midgut

Question 20

What does the midgut have a wide connection to

Answer 20

umbilical vesicle

Question 21

What are the neural crest cells derived

Answer 21

neuroectoderm

Question 22

What are the ectoderm derivatives

Answer 22

• central and preipheral nervous systes
  -glands
  -

Question 23

Which structures are formed from the neural crest cells

Answer 23

• Autonomic ganglia
  -Muscle

Question 24

What are the characteristsics of mesoderm

Answer 24

-Connective tissue
-Bone
- Cartilage

Question 25

What are the characteristics of the ectoderm

Answer 25

Central and peripheral nervous system pituitary glands

Question 26

Explainn the structure of the embryo on the fourth week and how many somites does it contain

Answer 26

- Embryo is almost straight -Contains 4-12 somites

Question 27

What are the openings of the neural tube called

Answer 27

- rostral(head end) -caudal( tail end)

Question 28

What completes the development of the central nervous system

Answer 28

neurpores

Question 29

When do the first two pharyngeal arches appear

Answer 29

fourth week

Question 30

What does the first pharyngeal arch form

Answer 30

lower jaw

Question 31

In the 4 week (26 days) how many pairs of pahryngeal arches are present

Answer 31

-3

Question 32

When is the upper limb buds recognized

Answer 32

day 26 ( 4th week)

Question 33

What are the ortic pits

Answer 33

- primordia of the internal ears

Question 34

What does the mesonephric ridges form

Answer 34

Kidneys

Question 34

What happens during the 5th week of development

Answer 34

- Head grows more -2 pharyngeal arches form -Mesoneophric ridges form

Question 35

What happens in 6th week

Answer 35

- hand plates start to develop -Development of the lower limb -Spontaneous movements

Question 36

What happens in the 7 th week

Answer 36

- Ossification of the bone starts in the upper limb

Question 37

What happens in the 8th week

Answer 37

- Head is bigger, half the size of the embryo -Neck region is established -Eyelids developW

Question 38

When does embryonic age begin

Answer 38

Fertilisation

Question 39

what is used to estimate the embryonic age

Answer 39

- They day when fertilisation occurs