5- Emberiology

Question 1

1- A 34 year old lady suffers from hyperparathyroidism. The right inferior parathyroid is identified as having an adenoma and is scheduled for resection. From which of the following embryological structures is it derived?

Answer 1

Third pharyngeal pouch

The inferior parathyroid is a derivative of the third pharyngeal pouch. The superior parathyroid originates from the fourth pharyngeal pouch.

Question 2

2- What is embryological origin of the pulmonary artery?

Answer 2

Sixth pharyngeal arch

The proximal part of the sixth right pharyngeal arch gives origin to the right pulmonary artery. The distal part gives origin to the left pulmonary artery and the ductus arteriosus.

Question 3

3- During embryological development, which of the following represent the correct origin of the
pancreas?

Answer 3

Ventral and dorsal endodermal outgrowths of the duodenum

The pancreas develops from a ventral and dorsal endodermal outgrowth of the duodenum. The ventral arises close to, or in common with the hepatic diverticulum, and the larger, dorsal outgrowth arises slightly cranial to the ventral extending into the mesoduodenum and
mesogastrium. When the buds eventually fuse the duct of the ventral rudiment becomes the main pancreatic duct.

Question 4

4- From which embryological structure is the ureter derived?

Answer 4

Mesonephric duct

The ureter develops from an outpouching that arises from the mesonephric duct. The mesonephric duct is associated with the metanephric duct that develops within the
metenephrogenic blastema. This forms the site of the ureteric bud which branches off the mesonephric duct.

Question 5

5- In a patient with an ectopic kidney where is the adrenal gland most likely to be located?

Answer 5

In its usual position

Because the kidney is present, rather than absent, the adrenal will usually develop and in the normal location.

Question 5

6- From which structure is the central tendon of the diaphragm derived?

Answer 5

Septum transversum

The septum transversum is a thick ridge of mesodermal tissue in the developing embryo that separates the thoracic and abdominal cavities and forms the central tendon of the diaphragm.

Question 6

7- The right and left pulmonary arteries are derived from which of the following embryological aortic
arches?

Answer 6

Sixth

Pulmonary vessels develop from the sixth arch

Question 7

8- A 6 month old child is brought to the surgical clinic because of non descended testes. What is the mainstructure that determines the descent path of the testicle?

Answer 7

Gubernaculum

The gubernaculum is a ridge of mesenchymal tissue that connects the testis to the inferior aspect of the scrotum. Early in embryonic development the gubernaculum is long and the testis are located on the posterior abdominal wall. During foetal growth the body grows relative to the gubernaculum, with resultant descent of the testis.

Question 8

9- What is the correct embryological origin of the stapes?

Answer 8

Second pharyngeal arch

Embryological origin stapes = 2nd pharyngeal arch
The ectoderm covering the outer aspect of the second arch originates from a strip of ectoderm lateral to the metencephalic neural fold. The cartilaginous element to this, eponymously known as Reicherts cartilage extends from the otic capsule to the midline on each side. Its dorsal end separates and becomes enclosed in the tympanic cavity as the stapes.

The dorsal ends of the cartilages of the first and second pharyngeal arches articulate superior to the tubotympanic recess. These cartilages form the malleus, incus and stapes. At least part of the malleus is formed from the first arch and the stapes from the second arch. The incus is most likely to arise from the first arch.