Embryological Derivatives

Question 1

Surface ectoderm

(ECTODERM)

Answer 1

1. Anterior pituitary (Rathke pouch)
2. Lens & cornea
3. Inner ear sensory organs, olfactory epithelium
4. Nasal & oral epithelial linings, salivary glands
5. Epidermis, sweat & mammary glands

Question 2

Neural tube

(ECTODERM)

Answer 2

1. Brain & spinal cord
2. Posterior pituitary, pineal gland
3. Retina

Question 3

Neural crest

(ECTODERM)

Answer 3

1. Neural ganglia, adrenal medulla
2. Schwann cells; pia & arachnoid mater
3. Aorticopulmonary septum & endocardial cushions
4. Branchial arches (bones & cartilage)
5. Skull bones
6. Melanocytes

Question 4

Mesoderm

Answer 4

1. Muscles (skeletal, cardiac & smooth)
2. Connective tissue, bone & cartilage
3. Serosal linings (e.g., peritoneum)
4. Cardiovascular & lymphatic system
5. Spleen & hemopoietic cells
6. Kidney & ureters, internal genitalia
7. Adrenal cortex

Question 5

Endoderm

Answer 5

1. Gastrointestinal tract, liver, pancreas
2. Lungs
3. Thymus, parathyroids, thyroid follicular cells
4. Middle ear epithelium
5. Bladder & urethra
6. Parafollicular (C) cells*

Question 6

Brain development and derivatives

Prosencephalon

• Telencephalon:

Answer 6

1. Cerebral hemisphere
2. Lateral Ventricles

Question 7

Prosencephalon

• Diencephalon:

Answer 7

1. Thalamus
2. 3rd Ventricle

Question 8

Mesencephalon

Answer 8

Mid Brain & Aqueduct

Question 9

Rhombencephalon

Metencephalon

Answer 9

Pons, Cerebellum & Upper 4th Ventricle

Question 10

Rhombencephalon

Myelencephalon

Answer 10

Medulla & Lower 4th Ventricle

Question 11

1st Aortic arch

Answer 11

Forms Maxillary artery

Question 12

2nd Aortic Arch

Answer 12

Stapedial and Hyoid arteries

Question 13

3rd Aortic Arch

Answer 13

• Common carotid arteries
• Proximal internal Carotid arteries

Question 14

4th Aortic Arch

Answer 14

• Left: Aortic arch
• Right: Proximal Right Subclavian artery

5th aortic arch regresses

Question 15

6th Aortic Arch

Answer 15

• Proximal Pulmonary arteria
• Ductus arteriosis

Question 16

Brachial Apparatus

Answer 16

Aka Pharyngeal apparatus

• Clefts: Derived from Ectoderm
• Arches: Derived from Mesoderm
• Pouches: Derived from Endoderm

Question 17

1st Brachial arch

Answer 17

• Trigeminal Nerve (CN-V)
• Meckels cartilage — Malleus, Incus & template for mandible
• Muscles of Mastication

Question 18

2nd Brachial Arch

Answer 18

• Facial Nerve (CN-VII)
• Reihert’s cartilage — Stapes & Upper part of Hyoid
• Muscles of facial expression

Question 19

3rd Brachial arch

Answer 19

• Glossopharyngeal Nerve (CN-IX)
• Remainder of hyoid
• Stylopharyngeus
• Common internal & external Carotid arteries

Question 20

4th Brachial arch

Answer 20

• Vagus Nerve (CN-X)
• Cartilages of larynx
• Circothyroid, Levator palatini, constrictors of pharynx muscles
• Aorta (left) , Brachiocephalic (right)

Question 21

6th Brachial arch

Answer 21

• Vagus Nerve (CN-X)
• Cartilages of larynx
• Intrinsic Muscles of Pharynx
• Pulmonary arteries

Question 22

1st Brachial Pouch

Answer 22

• Middle ear cavity
• Eustachian tube
• Mastoid air cells

Question 23

2nd Brachial Pouch

Answer 23

Develops into epithelial lining of palatine tonsils

Question 24

3rd Brachial Pouch

Answer 24

• Dorsal wings develop into inf. Parathyroid
• Ventral wings develop into Thymus

Question 25

4th Brachial Pouch

Answer 25

Dorsal wing develops into superior Parathyroid