Organogenesis

Question 1

What is embryonic folding ?

Answer 1

Folding of the flat trilaminar germ layer into a cylindrical embryo

Question 2

In which planes does Embryonic folding occurs?

Answer 2

Median and horizontal planes

Question 3

During median folding, at the beginning of the 4th-week cranial neural folding occurs to form what?

Answer 3

Primordium of the brain

Question 4

Describe development of the brain

Answer 4

Initially the brain projects dorsally into the amniotic cavity, later the developing forehead grows cranially beyond the oropharyngeal membrane overhanging the developing heart.

Question 5

During cranial neural folding, the movement of structures to the ventral surface happens at the same time and in different directions, namely:

Answer 5

Septum transversum
Primordial heart
pericardial coelom
oropharyngeal

Question 6

The foregut is developed from which part of the embryo?

Answer 6

An umbilical vesicle endoderm incorparated into the embryo

Question 7

The foregut lies intermediate of:

Answer 7

The Forebrain and the primordial heart

Question 8

Which membrane separate the foregut from the stomodeum?

Answer 8

The Oropharyngeal membrane

Question 9

lies caudal to the heart and develops into central tendon of the diaphragm after folding…….

Answer 9

Septum transversum

Question 10

Describe the position of the pericardial coelom after folding

Answer 10

lies ventral to the heart
lies cranial to the septum transversum

Question 11

Describe the caudal folding of the embryo

Answer 11

caudal eminences projects over cloacal membrane, the endodermal layer incorporates into the embryo as Hindgut- the future transverse, descending and he rectum

Question 12

After folding the primitive streak will lie caudal to ?

Answer 12

The Cloacal membrane

Question 13

Allantois projects into the umbilical cord from which structure?

Answer 13

the umbilical vesicle/ yolk sac

Question 14

Describe the folding of the primordia of ventrolateral abdominal wall

Answer 14

folds towards the median plane median plane, rolls embryonic disc edges ventrally

Question 15

The midgut is formed ……

Answer 15

when the abdominal cavity formation incorporates the endodermal layer

Question 16

Reduction of the connection of the midgut to the umbilical vesicle result in the formation of?

Answer 16

Omphaloenteric/ vitelline duct

Question 17

Ectoderm gives rise to which structures?

Answer 17

the central and peripheral nervous system
sensory epithelia of the eyes, ears and nose
neural crest cells forms spinal cord and cranial nerve cells

Question 18

Mesoderm give rise which structures of the embryo?

Answer 18

Connective tissue
cartilage
heart
pleura

Question 19

Endoderm give rise to?

Answer 19

Epithelial lining of digestive and respiratory
thyroid and parathyroid glands
Epithelial linning of urinary bladder

Question 20

how many somites does an embryo have in the 4th week

Answer 20

4-12 somites dorsally

Question 20

Neural tube is formed opposite——–widely open at ———-and ———-.

Answer 20

The somites
caudal
rostral neuropores

Question 21

The first pharyngeal arches are visible by 24 days. which parts contributes to the mandible and the maxilla

Answer 21

the major parts contributes to the mandible
Rostral extension contributes to the maxilla

Question 22

in which days are the upper limbs recognizable

Answer 22

26/27 days as small swellings on the ventrolateral body walls

Question 23

Lens Placodes develops into?

Answer 23

future lenses of the eyes

Question 24

the third pharyngeal arch pairs are visible at….

Answer 24

at 26 days

Question 25

the 4th pharyngeal arches are visible at?

Answer 25

The end of the 4th week

Question 26

At the end of the 4th week 3 structures are visible namely…?

Answer 26

the fourth of Pharyngeal arches
lower limbs buds
caudal eminences
rudiments of the cardiovascular system

Question 27

what minor changes occurs at the fifth week

Answer 27

head grows, exceeding other regions. rapid development of brain and facial prominences.

the face soon contacts the heart.

the 2 pharyngeal arch outgrows the 3 and 4th- forming the lateral depression called cervical sinus.

Question 28

ON the 6th week the shows which movements

Answer 28

he spontaneous movement of the trunk and developing limbs
also exhibit responses to touch

Question 29

Describe the regional differentiation of the upper limbs

Answer 29

development of elbows and hand plates
digital rays begin to develop in hand plates

Question 30

development of lower limb occurs?

Answer 30

4-5 days after upper limbs

Question 31

what develops around pharyngeal groove

Answer 31

the Auricular hillocks as samll swellings

Question 32

which structure does auricular hillocks form

Answer 32

pinna (auricle)

Question 33

external acoustic meatus is formed by

Answer 33

pharyngeal groove

Question 34

where does the intestine enter

Answer 34

extraembryonic coelom the proximal part of the umbilical cord called umbilical herniation

Question 35

in which week does the the notches appear between digital rays and what are they indicating

Answer 35

seventh week
they are indicating hand and foot digital

Question 36

when does upper ossification start

Answer 36

by the end of this week 7

Question 37

around week 8

Answer 37

hand digit are clearly visible .
notsches on feets are clealy

Question 38

what forms a band

Answer 38

scalp vascular plexus

Question 39

why limbs are differentiated

Answer 39

purposeful li movements

Question 40

during 8th week

Answer 40

Primary ossification of the femur begins
Caudal eminence disappears completely
Hands and feet move towards each other ventrally
Distinct human characteristics present by end of week
- Head still disproportionately large
Eyelids established and fused by end of the week
- United by epithelial fusion
Intestines remain in the umbilical cord proximally
External genitalia is visible, but not distinctive enough

Question 41

coadal eminences appear as ?

Answer 41

as Stub