Embryology Flashcards
Which germ layer gives rise to the musculature of the face and neck?
Mesoderm
During which weeks do the pharyngeal arches develop?
Week 4-5
What does each pharyngeal arch consist of?
Core of mesenchyme assoc. with pharyngeal clefts + pouches
Neural crest cells
Cranial nerve
Artery
The pharyngeal clefts externally/internally separate the pharyngeal arches (form ectoderm/endoderm lining)
The pharyngeal clefts externally separate the pharyngeal pouches (form ectoderm lining)
The pharyngeal pouches externally/internally separate the pharyngeal arches (form ectoderm/endoderm lining)
The pharyngeal pouches internally separate the pharyngeal arches (form endoderm lining)
There are 5 pharyngeal arches. The 5th pharyngeal arch does not develop in humans. True/False?
True
Arch 1, 2, 3, 4 and 6 exist only
(that’s how fcked up embryology is)
Which cranial nerve is assoc. with pharyngeal arch 1?
CN V
Which cranial nerve is assoc. with pharyngeal arch 2?
CN VII
Which cranial nerve is assoc. with pharyngeal arch 3?
CN IX
Which cranial nerve is assoc. with pharyngeal arch 4?
CN X (superior laryngeal branch)
Which cranial nerve is assoc. with pharyngeal arch 6?
CN X (recurrent laryngeal branch)
What skeletal components are assoc. with pharyngeal arch 1?
Maxillary: maxilla, zygoma, temporal bone
Mandibulary: mandible, Meckel’s cartilage, incus, malleus
What skeletal components are assoc. with pharyngeal arch 2?
Stapes
Styloid process of temporal bone
Stylohyoid ligament
Lesser horn + upper hyoid
What skeletal components are assoc. with pharyngeal arch 3?
Greater horn + lower hyoid
What skeletal components are assoc. with pharyngeal arches 4 + 6?
Laryngeal cartilages
What muscles are assoc. with pharyngeal arch 1?
Muscles of mastication
Mylohyoid
Tensor tympani
Tensor palatini
What muscles are assoc. with pharyngeal arch 2?
Muscles of facial expression
Stapedius
Stylohyoid
What muscles are assoc. with pharyngeal arch 3?
Stylopharyngeus
What muscles are assoc. with pharyngeal arch 4?
Cricothyroid
Levator palatine
Pharyngeal constrictors
What muscles are assoc. with pharyngeal arch 6?
Intrinsic laryngeal muscles
Which pharyngeal cleft does the external auditory meatus develop from?
Cleft 1
What happens to the 2nd-4th pharyngeal clefts?
Usually disappear; lose contact and form cervical sinus
What does the 1st pharyngeal pouch develop into?
Middle ear cavity
Eustachian tube
(ultimately tympanic membrane)
What does the 2nd pharyngeal pouch develop into?
Palatine tonsil
What does the 3rd pharyngeal pouch develop into?
Inferior parathyroid gland
Thymus
What does the 4th pharyngeal pouch develop into?
Superior parathyroid gland
Ultimobranchial body
What are otic placodes?
Thickening/invagination of ectoderm at back of embryo
What are otic vesicles?
Endocytosed otic placode that gives rise to inner ear
i.e. otic placode - otic pit - otic vesicle
What 3 regions develop as part of the otic vesicle?
Endolymphatic duct sac Utricular portion (forms semicircular canals) Saccular portion (forms cochlea)
List the 5 facial swellings present from week 4
Frontonasal prominence
2x maxillary prominences
2x mandibular prominences
What is the stomodeum?
Site of the future mouth
List the nasal swellings that develop on the frontonasal prominence in week 5
2x medial nasal swellings
2x lateral nasal swellings
What grows in the groove between the eye and the lateral nasal swelling?
Nasolacrimal duct
What nasal features develop from the frontonasal prominence?
Bridge
Bony septum
What nasal features develop from the medial nasal prominences?
Crest + tip of nose
What nasal features develop from the lateral nasal prominences?
Alae (sides of nostrils)
What does the primary palate form from?
Intermaxillary segment (formed by fusion of 2 medial nasal prominences)
What does the labial portion of the intermaxillary segment give rise to?
Philtrum of upper lip
What does the upper jaw component of the intermaxillary segment give rise to?
Carries 4 incisors
What does the secondary palate form from?
Palatine shelves that grow downwards from maxillary prominences
Is cleft palate more common in females or males?
Females
Failure of fusion of secondary palate
Is cleft lip more common in females or males?
Males
Failure of fusion of primary palate