Embryology

Question 1

Name the organ that arises from the same pharyngeal pouch as the thymus.

Answer 1

Inferior parathyroids

Question 2

Where do the voluntary muscles of the tongue originate?

Answer 2

Occipital somites

Question 3

Describe the primary palate and name the structure from which it arises.

Answer 3

Medial nasal prominence

Question 4

The anterior two thirds of the tongue are derived from which pharyngeal arch.

Answer 4

1st

Question 5

Cleft lip occurs when the ______ fails to fuse with the ______.

Answer 5

Maxillary prominence, medial nasal prominence

Question 6

Lateral cervical cysts are commonly located____________.

Answer 6

Anterior to the SCM

Question 7

How many Pharyngeal arches are there?

How many Pharyngeal pouches?

How many Pharyngeal grooves?

What is significant about the fifth arch?

Answer 7

1. There are fice arches (1,2,3,4,6)
2. There are 4 pharyngeal pouches (1,2,3,4)
3. There are 4 pharyngeal grooves (1,2,3,4)

Pharyngeal arch 5 has completely regressed along with the fifth branch of the aortic arch that it would have formed.

Question 8

What are the pharyngeal arches made of?

Answer 8

Somite mesoderm and neural crest cells

Somite mesoderm forms muscles and arteries

Neural crest cells form bone and connective tissue

Question 9

What is the thyroid formed from?

On adults what indicates the thyroglossal duct?

Answer 9

Thyroid diverticulum which migrates caudally passing the ventral hyoid bone and remains connected to the tongue by the thyroglossal duct.

Foramen secum

Question 10

What cranial nerve comes from the first arch?

What is the adult derivitave of the mesoderm?

What is the adult derivitive of the Neural crest?

Answer 10

5

Muscles of mastication, mylohyloid, anterior digastric, tensor palentini, tensor tympini

Menkels cartlidge, maxilla, mandible, incus, malleus, zygomatic bone, squamous temporal bone, sphenomandibular ligament,

Question 11

What cranial nerve comes from the 2nd arch?

What is the mesoderm derivitave?

What is the neural crest derivitive?

Answer 11

CN7

Muscles of facial expression, posterior digastric stylohyloid, stapedus

Hyloid Arch, Stapes, styloid process, stylohyloid ligament, lesser horn and upper body of the hyloid ligament

Question 12

What CN comes from the third arch?

Mesoderm derivitive?

Neural Crest Derivitive?

Answer 12

9

Styopharyngeus, common carotid arteries, internal carotid arteries

Greater and Lower Horn of the Hyloid Bone

Question 13

What CN comes from the 4th arch?

Mesoderm Derivitive?

Neural crest derivitive?

Answer 13

CN10 (Inferior Laryngeal)

Muscles fo the soft pallate , pharynx, cricopharyngeus, laryngeal cartlidge, subclavian artery, aortic arch

No neural crest derivitive

Question 14

What CN comes from the sixth arch?

Answer 14

CNX (Superior Laryngeal)

Intrinsic muscles of the larynx, upper muscles of the esophagus, laryngeal cartlidge, pulmonary arteries, ductus arteriosus

Question 15

What is derived from the first pouch?

Answer 15

Epithelial lining of the auditory tube, middle ear cavity and mastoid air cells

First pouch has half ectoderm and half endoderm

Question 16

What is derived form the second pouch?

Answer 16

Epithelial lining of the palantine tonsils

Pouches are made of endoderm

Question 17

What is derived from the third pouch?

Answer 17

Inferior parathyroid gland and thymus

Pouches are made of endoderm

Question 18

What is derived from the fourth pouch?

Answer 18

Superior parathyroid gland and ultimobrachial body

Pouches are made of endoderm

Question 19

What is derived from the first groove?

Answer 19

Epithelial lnings of the external auditory meatus

Grooves are made of ectoderm

Question 20

What happens to grooves 2,3,4 ?

Answer 20

Obliterated

Question 21

What is the most common site of thyroglossal cyst?

Answer 21

Midline close to the hyphoid bone. Thyroid forms from the diverticulum and descends caudally passing the hyphoid bone. If the thyroglossal duct remains after the descent it will from the thyroglossal cyst.

Question 22

What is the taste sensation from the oral 2/3 of the tongue

Answer 22

Chorda typani branch of the facial nerve CN7. this part of the tongue froms from the first pharyngeal arch so the sensation will be from the CN5

Question 23

What fuses to form the intermaxillary segment?

Answer 23

Medial nasal prominances fuse at the midline to form the adult palate.

Question 24

What is the most common site of pharyngeal fistula?

Answer 24

Anterior border of the sternocleomastoid muscle. The pharyngeal fistula forms when pharyngeal pouch 2 and pharyngeal groove 2 persist therefore the fistula is on the lateral portion of the neck.

Question 25

What is the most common congenital malformation of the head and neck area?

Answer 25

Unilateral cleft lip. This forms when the maxillary prominance fails to fuse with the medial nasal prominance and when the underlying somitomeric mesoderm and neural crest cells fail to proliferate.

Question 26

Which pharyngeal arch is associated with Treacher collins Syndrome? Is Robbins syndrome similiar? If yes how so

Answer 26

First arch syndrome is treacher collins syndrome and is a result of the lack of migration of the neural crest cells. You will observe an underdevelopment of the zygomatic bone, deformed lower eyelids and external ears. Robbins sequence has normal ears and a cleft pallate.

Question 27

You are operating to remove a thyroid tumor and you send a small section to frozen section to see if the tissue is malignant. The report comes back as parathyroid tissue with reminants of thymus HOW CAN THIS BE?

Answer 27

Eptopic glandular tissue is commonly found in this region. The parathyroid and thymus migrate in a caudal and medial direction during development and eptopic glandular tissue can be found anywhere in their path

Question 28

A newborn infant presents with treacher collins syndrome. Which structure would most likely be affected A. Hyphoid Bone B. Stapes C. Malleus D. Thyroid Gland E. Inferior Parathyroid

Answer 28

The only structure listed that is derived from the first arch is the Malleus.

Question 29

How does a pharyngeal cyst form?

Answer 29

When the part 2,3,4 of the pharyngeal groove fail to fuse they will form a cyst normally on the margin of the mandible

Question 30

What is degeorge syndrome

Answer 30

A defect in the third and fourth pouch which results in the lack of a thymus. Sevire immune defects will persist as well as a lack of parathyroid glands which render the patient unable to regulate calcium. Kiddos are normally killed by the cardiovascular abnormalities.