Embryology

Question 1

16 cell morula what day

Answer 1

3

Question 2

hatches what day

Answer 2

5

Question 3

1. what establishes the Dorsal/Ventral Axis?
2. what establishes the Cranial/Caudal Axis?

Answer 3

1. BILAMINAR DISC formation
2. PRIMITIVE STREAK formation

Question 4

Notochord serves as the basis for the development of what?

Answer 4

the AXIAL SKELETON

(paraxial mesoderm)

Question 5

when is Primitive Utero-Placental Circulatory system formed?

1. what forms Primary Chorionic Villi?
2. what forms Secondary Chorionic Villi?
3. what forms Tertiary Chorionic Villi?

Answer 5

DAY 13

1. PRIMARY Chorionic Villi: CYTOTROPHOBLAST grows into the SYNCYTIOTROPHOBLAST
2. SECONDARY Chorionic Villi: EXTRAEMBRYONIC MESODERM grows into primary villus
3. TERTIARY Chorionic Villi: EMBRYONIC BLOOD VESSELS FORM in villus

Question 6

when is the Placenta formed with materno-embryonic exchanges taking place?

Answer 6

end of 4TH WEEK

Question 7

when is Gastrulation

Answer 7

WEEK 3

Question 8

when is Neurulation

Answer 8

WEEK 3 & 4

Question 9

when does the Cranial Neuropore close?

when does the Caudal Neuropore close?

Answer 9

CRANIAL: DAY 25

CAUDAL: DAY 28

Question 10

Epidermis is derived from which layer?

Dermis is derived from which layer?

Answer 10

• EPIDERMIS: SURFACE ECTODERM
• DERMIS: PARAXIAL MESODERM
  (dermis of back)

Question 11

Somites (paraxial mesoderm) determine the Migration pattern of what

Answer 11

NEURAL CREST CELLS & SPINAL NERVE AXONS

Question 12

when is Folding of the Embryo

Answer 12

WEEK 4

Question 13

Hepatocytes origin:

Kupffer and Haematopoietic cells origin:

Answer 13

Hepatocytes: ENDODERM (FOREGUT)
- induced by Cardiogenic mesoderm

Kupffer and Haematopoietic cells: MESODERM

MOST OF LIVER FROM ENDODERM
but some parts from MESODERM

Question 14

when does INSULIN secretion begin

Answer 14

5TH MONTH

(but Islets of Langerhans formed at 3 Months)

Question 15

Lung Bud / Respiratory Diverticulum is an outgrowth of what

Answer 15

FOREGUT ventral wall
(4 weeks)

Question 16

Cartilaginous, Muscular and Connective Tissue components of the Lungs, Trachea and Ovaries are derived from what?

Answer 16

SPLANCHNIC MESODERM

Question 17

when do Pharyngeal Arches appear

Answer 17

DAY 24

Question 18

Pharyngeal Arch 1

cranial nerve:
artery:
derivative:

Answer 18

• MANDIBULAR ARCH

TRIGEMINAL NERVE

MAXILLARY ARTERY

Muscles of mastication, skull bones etc

Question 19

Pharyngeal Arch 2

cranial nerve:
artery:
derivative:

Answer 19

• HYOID ARCH

FACIAL NERVE

HYOID & STAPEIDAL ARTERY

Muscles of Facial expression, Reichert’s cartilage, lesser horn of hyoid
(most of hyoid)

Question 20

Pharyngeal Arch 3

cranial nerve:
artery:
derivative:

Answer 20

GLOSSOPHARYNGEAL NERVE

COMMON & INTERNAL CAROTID ARTERIES

NECK STRUCTURES
GREATER HORN, INFERIOR BODY of HYOID BONE

Question 21

Pharyngeal Arch 4

cranial nerve:
artery:
derivative:

Answer 21

VAGUS NERVE

AORTIC ARCH & RIGHT SUBCLAVIAN ARTERY

THYROID CARTILAGE
(NECK STRUCTURES)

Question 22

Pharyngeal Arch 6

cranial nerve:
artery:
derivative:

Answer 22

VAGUS NERVE

PULMONARY ARTERIES

CRICOID CARTILAGE
(NECK STRUCTURES)

Question 23

when do you have 42-44 pairs of Somites by

Answer 23

END 5TH WEEK

Question 24

1. when is Primordial Heart present and pumping Blood?
2. when does it separate into Atria and Ventricles?

Answer 24

1. DAY 26
2. DAY 28