Embryology

Question 1

What is a blastocyst

Answer 1

• Blastocyst comprised of outer trophoblast and inner embryoblast.
• Trophoblast becomes foetal component of placenta.
• Embryoblast splits to become bilaminar embryonic disc.
• The cells of this disc develop into the embryo proper.

Question 2

What is a blastocyst compromised of

Answer 2

Outer trophoblast and inner embryoblast

Question 3

What does a trophoblast become

Answer 3

Foetal component of placenta

Question 4

What does a embryoblast become

Answer 4

Splits to become bilaminar embryonic disc

Question 5

What happens to the cells of the bilaminar embryonic disc

Answer 5

Develop into embryo proper

Question 6

What happens during the 3rd week in terms of primitive streak

Answer 6

Cranio caudal primitive streak forms on dorsal surface
Cells migrate into streak
Forms trilaminar disc

Question 7

Ectoderm

Answer 7

Covers the embryo

Question 8

Mesoderm

Answer 8

Lies between the ectoderm and the endoderm

Question 9

Endoderm

Answer 9

Lines the gut tube

Question 10

Gastrulation

Answer 10

3 layers arise:
-ectoderm
-mesoderm
-endoderm

Question 11

What is the endoderm

Answer 11

Is open to the yolk sac
Fate: Linings of the gut, associated glands and lining of the lungs

Question 12

What is the mesoderm

Answer 12

Lies between the ectoderm and the endoderm
Fate: notochord, muscles, bone and connective tissue

Question 13

Somites

Answer 13

Paired mesodermal blocks that lie lateral to the neural tube

Question 14

What is the mesoderm

Answer 14

Intermédiaire mesoderm- lies lateral to notochord ventral to the somites and dorsal to the lateral plane
Fate: kidneys, ureters and gonads
Lateral place mesoderm- surrounds coelom (body cavity)
Splanchnic mesoderm- visceral (inner) fate= gut wall
Somatic mesoderm- parietal (outer) fate=body wall
Fate: heart, blood vessels, gut musculature and lining of body cavities

Question 15

What is the surface ectoderm

Answer 15

Covers the embryo. Continous with the amnion
Fate: epidermis of skin (hair, nails, and skin glands)

Question 16

Neural crest

Answer 16

Dorso lateral to neural tube
Fate: PNS, ganglia, structures in head and neck

Question 17

Neural tube

Answer 17

Fate:CNS

Question 18

Neuroectoderm

Answer 18

Neural tube and neural crest tissue derived from neuroctoderm
Neural crest tissue is unique to vertebrates

Question 19

Notochord

Answer 19

Cranio caudal stiffening rod that is characteristic of chordates
Fate: nucleus pulposus of IV discs during infancy

Question 20

When is the neural plate formed

Answer 20

At 18 days ectoderm starts to thicken to from the neural plate

Question 21

When should the neural tube fuse

Answer 21

By the end of the 4th week

Question 22

Forebrain

Answer 22

Optic cups, cerebral hemispheres, olfactory bulb and tract, hypothalamus and thalamus

Question 23

Midbrain

Answer 23

Remains undivided

Question 24

Hindbrain

Answer 24

Cerebellum, medulla and pons

Question 25

Formation of neural crest

Answer 25

-fusion starts in the middle of the tube
-neural crest cells might into mesoderm
-somites form from mesoderm
-ventral part= vertebrae
-dorsal part=skin/skeletal muscle

Question 26

Gut folding around transverse axis description

Answer 26

-foregut and hind gut are formed by cephalocaudal folding
-this is due to differential growth
-foregut and hind gut commence as blind tubes that terminate at the buccopharyngeal and cloacal membranes
-midgut open to yolk sac

Question 27

Development of the diaphragm

Answer 27

-lungs and bronchi develop as out pocketing of forgut
-therefore their lining is derived from ectoderm
-spectrum transversal folded inwards

Question 28

Development of the lungs

Answer 28

-diverticulum formed in the endoderm at the future site of the glottis
-splits in two: primary bronchi
-divides again: secondary bronchi etc
-endoderm gives rise to: mucosa, alveolar epithelium

Question 29

What does the mesoderm give rise to during the development of lungs

Answer 29

-bronchai and tracheal cartilages
-bronchai and tracheal muscles
-pulmonary vasculature
-visceral pleurae

Question 30

Division of the coelom

Answer 30

-the future pericardial and peritoneal cavities are separated by the septum transversum
-the future pleural and peritoneal cavities communicate via (the pericardio- peritoneal) canals
-pleuro-pericardial folds separate the pericardial and pleural cavities and contain phrenic nerves
-lung buds invade the mesoderm of the wall

Question 31

What is the Diaphragm formed from

Answer 31

-septum transversum centrally
-pleuroperioneal folds dorso laterally
-the oesophageal mesentery dorso medically
-body wall