VIVA – Anatomy – Congenital Flashcards
What are the derivatives of the arches?
For each: ARCH, SKELETAL DERIVATIVES, ARTERY
MUSCULAR DERIVATIVES, INNERVATION
For each: ARCH, SKELETAL DERIVATIVES, ARTERY
MUSCULAR DERIVATIVES, INNERVATION
1st Branchial Arch (Meckel’s Cartilage)
Proximal Part
Ramus of mandible
Sphenomandibular lig
Anterior Malleolar lig
Malleus (Except Manubrium - 2nd Arch)
Incus (Except long process - 2nd Arch)
Distal Part withers
Maxillary
Muscles of Mastication
- Masseter
- Pterygoids
- Temporalis
Tensor Tympani
Tensor Veli Palatini
Anterior Belly of Digastric
Mylohyoid muscle
Trigeminal Nerve (V3)
Remaining trigeminal provides sensory
2nd Branchial Arch (Reichert’s Cartilage)
Proximal Part
Styloid process
Manubrium of Malleus
Long process of incus
Stapes Superstructure (Footplate derived from otic capsule)
Central Portion (withers leaving)
Stylohyoid ligament
Distal Portion
Superior body of hyoid
Lesser cornu of hyoid
Stapedial
Muscles of facial expression
Platysma
Posterior Belly of Digastric
Stylohyoid muscle
Stapedius Muscle
Facial Nerve
Sensory distribution absent except for small branch to EAC
3rd Branchial Arch
Inferior Body of Hyoid
Greater Cornu of Hyoid
Proximal part of ICA (dorsal aorta forms remaining part)
Stylopharyngeus
Glossopharyngeal Nerve
Also innervates parts of pharynx
4th Branchial Arch
Thyroid
Arch Aorta (L) and Subclavian (R)
Constrictors of pharynx
Striated upper ½ oesophagus
Palatoglossus
Palatopharyngeus
Salpingopharyngeus
Levator palatine
?Cricothyroid
Vagus Nerve and Cranial Accessory nerve *
6th Branchial Arch
Cricoid
Arytenoid
Corniculate
Cuneiform cartilages
Ventral = Pulmonary Artery
Dorsal = Ductus Arteriosus
Cricopharyngeus
All Laryngeal intrinsic muscles
RLN
What are the theories of brachial cysts?
Branchial apparatus theory = cyst represents remnants of pharyngeal pouch or branchial cleft
Cervical sinus theory = represent the remains of the cervical sinus of His, formed by 2nd arch growing down – trapped ectoderm fails to involute (extension of 1st theory) – 2ND arch becomes platysma
Thymopharyngeal duct theory = cyst represents remnants of original connection between thymus and 3rd branchial pouch
Inclusion theory = cysts are epithelial inclusions of LNs – most likely
Epithelial rest theory = cysts develop from epithelial rests of tissue from Waldeyers ring
Describe the pathway of the following branchial fistulas 1st arch
Always superior to the hyoid bone
Ant neck
Tract usually starts on floor of EAC in cartilaginous portion or at bony-cartilage junction
Usually found in a triangle formed from the EAC curving to meet the mid-hyoid and tip of the chin
The tract courses over the angle of the mandible, through the parotid gland and terminates near the bony-cartilaginous junction of the EAC
Ends between first (mandibular) and Second (hyoid) arches
External opening is usually in submandibular region
- Type I
- Duplication of the membranous EAC
- Ectoderm only
- Pass lateral to the facial nerve
- Present as swelings near the ear (preauricular)
- Lesions track parallel to the EAC and middle ear and often begin as fistulous tracts at the post auricular or pretragal area
- Ends in a blind end at a bony plate at level of mesotympanum
- Cyst lined by Squamous epithelium but no cartilage or adnexa
- Duplication of the membranous EAC
- Type II (more common)
- Duplication of EAC and pinna
- Involve ectoderm and mesoderm
- Contain cartilage
- Pass medial to the facial nerve
- Course of the tract in relation to the facial nerve is variable – 29% may pass medial to the nerve, some may split around the nerve
Present as pre-auricular, infra-auricular or postauricular swellings inferior/posterior to angle of mandible or anterior to SCM
Describe the pathway of the following branchial fistulas - 2nd arch
The tract courses deep to the second arch derivatives (external carotid and stylohyoid) and superficial to the third arch derivatives
If external opening is present – is most consistently found at the anterior border of the SCM at the middle and inferior two-thirds junction (b/c SCM arises from epicardial ridge)
It then courses anterior to the SCM, superficial to the IX, XII nerve to turn medial and pass between the internal and external carotid artery
The tracts typically terminate into the tonsillar fossa or close to middle constrictor
Describe the pathway of the following branchial fistulas - 3rd arch
- Cystic structure at lower anterior border SCM, at level of superior pole of thyroid
- ?Lateral to CCA
- Deep to ICA and CNIX (?post to ICA and inferior to CN IX)
- lateral to the hypoglossal nerve à can cause a palsy if infected
- Pierce thyrohyoid membrane above superior laryngeal nerve (4th arch – lies superficial to SLN)
- Communicate with the pharynx via pyriform sinus – not ascend above CNIX or styloharyngeus which are 3rd arch
Describe the pathway of the following branchial fistulas - 4th arch
- Depends upon side
- Similar to course of RLN
- Between 4th and 6th arch structures
- Internal sinus opening near apex of piriform sinus, exit the pharynx caudal to SLN (inferior – third passes above), travel translaryngeal under thyroid ala to emerge near cricothyroid joint, descend superficially to RLN in paratracheal region
- RIGHT
- Loops around subclavian artery
- Deep to ICA
- Ascends to level hypoglossal nerve
- Descends along anterior border SCM
- Enters pharynx at pyriform sinus apex or cervical oesophagus
- LEFT (93%)
- Tract passes into mediastinum
- Loops around arch of aorta medial to Lig arteriosum
- Ascends in similar course to (R)
- Below the superior laryngeal nerve
What is the difference in the pathways between a 3rd and 4th cyst?
3rd passes above SLN, 4th below
4th follows path of RLN
What will the report be on histopathology from a branchial cyst?
Cyst wall is composed of either squamous or columnar cells with lymphoid infiltrate, often with prominent germinal centers. The cyst may contain granular and keratinaceous cellular debris. Cholesterol crystals may be found in the fluid extracted from a branchial cyst.
