Embryology

Question 0

Products of the second pharyngeal arch are…

Answer 0

Stapes and stapedius
Styloid process and stylohyoid
Stylohyoid ligament
Lesser horn
Superior part of hyoid bone
Muscles of facial expression
Posterior belly digastric
(Facial nerve)

Question 1

Products of the first pharyngeal arch are…

Answer 1

Meckel's cartilage
Mandible
Malleus and Incus
SphenoMandibular ligament
Anterior ligament of malleus
Lingula
Muscles of mastication
Two tensor muscles (tymp and palati)
MM of ant. 2/3 tongue
Maxillary artery
Mylohyoid and ant. belly digastric
(Maxillary br. of Trigeminal nerve)

Question 2

Products of the third pharyngeal arch are….

Answer 2

Greater horn and inferior of hyoid bone
Stylopharyngeus
(Glossopharyngeal nerve)

Question 3

Products of the fourth and sixth pharyngeal arches are…

Answer 3

Thyroid
Cricoid
Epiglottic and arytenoid cartilages
Intrinsic muscles of the larynx
Muscles of the pharynx
Levator palati
(Vagus nerve)

Question 4

Lateral derivatives of the first pharyngeal arch are…

Answer 4

Auditory tube
Tympanic membrane
Mastoid antrum

Question 5

Lateral derivatives of the second pharyngeal arch are…

Answer 5

Tympanic cavity
Tonsillar crypts
Supratonsillar fossa

Question 6

Lateral derivatives of the third pharyngeal pouch are…

Answer 6

Inferior parathyroid gland
Thymic rudiments
Each gives a lobe to the thymus

Question 7

Lateral derivatives of the fourth pharyngeal pouch are…

Answer 7

Superior parathyroid glands

Question 8

Lateral derivatives of the fifth pharyngeal pouch are…

Answer 8

Ultimobranchial body which donate para follicular (C) cells to the thyroid which produce calcitonin.

Question 9

What pouches give rise to the tongue?

Answer 9

Buds from the first, third, and fourth arches form the storms of the tongue.
(Hypoglossal nerve)

Question 10

What are the remnants of the Müllerian ducts in a male?

Answer 10

Disappears in the male except at either end:
Upper end persists as appendix testis
Lower end persists as prostatic utricle.

Question 11

What does the mesonephric (Wolffian) duct form in the male?

Answer 11

The Wolffian duct forms the epididymis and vas.

Question 12

What does the metanephros contribute to male genitalia?

Answer 12

The metanephros tubules persist and attach to the testis creating vasa efferentia. These drain products of the tested into the mesonephric duct. Some are blind ending and form vasa abberentia, the appendix of the epididymis is an example of this.

Question 13

What does the mesonephric (Wolffian) contribute to in female genitalia?

Answer 13

The mesonephric duct and tubules usually disappear in the female. Remnant can be found in the mesosalpinx as the epoophoron and in the base of the broad ligament as the paroophoron.

Question 14

What do the Mullerian ducts contribute to in the female?

Answer 14

The fuse at their caudal ends to form the uterus and continue to reach the dorsal wall of the urogenital sinus thereby forming the upper part of the vagina. Their cranial ends persist as uterine tubes.

Question 15

Which major fetal veins persist in the term fetus?

Answer 15

Left umbilical
Right vitelline
Right cardinal

Question 16

What are the 4 sources from which the diaphragm develops?

Answer 16

1. Septum transversum (central tendon)
2. 3rd, 4th, 5th cervical myotomes
3. Pleuroperitoneal membranes
4. Oesophageal mesentery.

Question 17

Describe the development of the foramen ovale:

Answer 17

The primary septum grows downwards towards the endocardial cushions, but does not fuse. The gap remaining is the primary foramen. Before the ostium primum can be obliterated, the ostium secondum is formed. Now, the septum secundum grows down, though does not enclose the ostium secundum entirely. This gap is the foramen ovale.

Question 18

What is the fate of the sinus venosus?

Answer 18

The right horn becomes incorporated into the right atrium, forming its smooth part and accounting for the SVC and IVC draining into it. The rest of the sinus venosus persists as the coronary sinus, with the left horn being represented by the oblique vein of the left atrium.

Question 19

What is the fate of the truncus arteriosus?

Answer 19

This becomes divided by two internal swellings, the right and left bulbar ridges, which meet to form the aorticopulmonary septum. The septum spirals down, turning 180* to join the posterior endocardial cushion to form the membranous part of the IV septum.

Question 20

From where does the SA node develop?

Answer 20

Sinus venosus tissue

Question 21

From where do the AV node and bundle arise?

Answer 21

The original atrial tissue.

Question 22

What is the Tetralogy of Fallot?

What is the cause?

Answer 22

1. Pulmonary stenosis
2. Over-riding aorta
3. Defect in membranous IV septum
4. RV hypertrophy.

Due to unequal division of the Truncus Arteriosus.

Question 23

What is the fate of the 3rd branchial arch artery?

Answer 23

The 3rd remains as the common and internal carotid arteries.

Question 24

What is the fate of the 4th branchial arch artery?

Answer 24

The 4th on the right contributes to the subclavian, on the left to the arch of the aorta.

Question 25

Which branchial arch artery persists as the ligamentum arteriosum?

Answer 25

The 6th branchial arch artery on the left. On the right, the dorsal part of the 6th disappears.

Question 26

Describe the course and cause of a non-recurrent right laryngeal nerve:

Answer 26

Commonly caused by failure of the brachiocephalic trunk to arise from the normal location (arises instead from left of the the common carotid). Occurs in 1% of people. Hazard during thyroidectomy.

Question 27

What is the incidence and cause of a cleft lip?

Answer 27

Cleft lips occur in 1 in 1000 births. They are caused by failure of fusion of the maxillary and medial nasal prominences.

Question 28

What is the incidence and cause of a cleft palate?

Answer 28

Cleft palate occurs in 1 in 2500 births. It may be partial or complete and is caused by failure of the two palatal processes to unite. It may cause a bifid uvula or complete cleft palate.