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Flashcards in Embryology Deck (31):

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

Inferior parathyroids


Where do the voluntary muscles of the tongue originate? 

Occipital somites


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

Medial nasal prominence


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



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

Maxillary prominence, medial nasal prominence


Lateral cervical cysts are commonly located____________.

Anterior to the SCM


How many Pharyngeal arches are there?

How many Pharyngeal pouches?

How many Pharyngeal grooves?

What is significant about the fifth arch?

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. 


What are the pharyngeal arches made of?

Somite mesoderm and neural crest cells

Somite mesoderm forms muscles and arteries

Neural crest cells form bone and connective tissue


What is the thyroid formed from?



On adults what indicates the thyroglossal duct?

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


Foramen secum 


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?


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

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


What cranial nerve comes from the 2nd arch?

What is the mesoderm derivitave?

What is the neural crest derivitive?


Muscles of facial expression, posterior digastric stylohyloid, stapedus

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


What CN comes from the third arch?

Mesoderm derivitive?

Neural Crest Derivitive?


Styopharyngeus, common carotid arteries, internal carotid arteries

Greater and Lower Horn of the Hyloid Bone


What CN comes from the 4th arch?

Mesoderm Derivitive?

Neural crest derivitive?

CN10 (Inferior Laryngeal)

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

No neural crest derivitive


What CN comes from the sixth arch?

CNX (Superior Laryngeal)

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


What is derived from the first pouch?

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

First pouch has half ectoderm and half endoderm 


What is derived form the second pouch?

Epithelial lining of the palantine tonsils

Pouches are made of endoderm 


What is derived from the third pouch?

Inferior parathyroid gland and thymus

Pouches are made of endoderm 


What is derived from the fourth pouch?

Superior parathyroid gland and ultimobrachial body

Pouches are made of endoderm 


What is derived from the first groove?

Epithelial lnings of the external auditory meatus

Grooves are made of ectoderm 


What happens to grooves 2,3,4 ?



What is the most common site of thyroglossal cyst?

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. 


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

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


What fuses to form the intermaxillary segment?

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


What is the most common site of pharyngeal fistula?

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. 


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

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. 


Which pharyngeal arch is associated with Treacher collins Syndrome?


Is Robbins syndrome similiar? If yes how so

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. 


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 


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


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 

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


How does a pharyngeal cyst form?

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 


What is degeorge syndrome  

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.