Anatomy + Embryology Flashcards
What are the layers of the deep cervical fascia?
What are the muscles inclosed by the deepest layer?
THREE LAYERS
1. Superficial (investing)
- Underlies platysma and completely invests or encircles all of the superficial neck structures
2. Middle (pretracheal or visceral)
- Encloses visceral structures of the neck (trachea, esophagus, thyroid gland)
3. Deep (prevertebral)
- Surrounds the deep muscles of the neck and cervical vertebrae
MUSCLES ENCLOSED BY DEEP PREVERTEBRAL LAYER - muscles that lie on the anterior spect of the cervical vertebrae
1. Levator Scapulae
2. Scalenus anterior/middle/posterior
3. Longus colli and capitis
Cummings Chapter 202 Figure 202.1
Describe the embryology of the face and neck.
Starts at 4-5 weeks GA
Branchial/pharyngeal interchangeable
- Pharyngeal arches form: 4-5 pairs of finger-like masses of tissue that form the future face and neck
- 5th arch never forms; 6th arch no consensus but cannot be readily seen externally
- Contains mesoderm and neural crest cells –> gives rise to structures composed of muscle, bone, or the like derivatives
- Each arch receives motor/sensory innervation from associated cranial nerve, blood supply from an associated artery - Pharyngeal clefts
- External indentations of the arches, lined by ectoderm - Pharyngeal pouches
- Lateral outpouchings from the foregut region composed of endoderm (ie. opposite siide of clefts)
- Endodermal lining contacts ectodermal epithelium of the corresponding cleft at the extreme lateral wall of each pharyngeal pouch
- Forms specific elements of the pharynx
Cummings Chapter 202, Fig 202.3-4
List all the pharyngeal arch (branchial arch) derivatives, including the relative artery, skeletal elements, muscles, and cranial nerves
FIRST BRANCHIAL/PHARYNGEAL ARCH:
A. Arch Artery
- Terminal branch of internal maxillary artery (SPA)
B. Skeletal Elements
- Meckel’s cartilage: mandibular ramus, mandibular body, malleus (Except manubrium), incus (except long process)
- Maxillary process: forms alisphenoid, premaxilla, maxilla, zygoma, squamous portion of temporal bone
- Sphenomandibular ligament
- Anterior malleolar ligament
C. Muscles
- Muscles of mastication (temporalis, masseter, medial pterygoid, lateral pterygoid)
- Mylohyoid
- Anterior belly of digastric
- Tensor tympani
- Tensor veli palatini
D. Cranial nerve
- Maxillary and mandibular divisions of trigeminal nerve (V2 and V3)
SECOND BRANCHIAL/PHARYNGEAL ARCH:
A. Arch Artery
- Stapedial artery (embryonic)
- Caroticotympanic artery (contributes to osseous part of the pharyngotympanic tube- eustachian tube)
B. Skeletal Elements
- Reichert’s cartilage: Styloid process, manubrium of malleus, long process of incus, stapes superstructure, stylohyoid ligament, superior hyoid body, lesser cornu of hyoid
C. Muscles
- Muscles of facial expression (orbicularis oculi and oris, risorius, platysma, auricularis, frontalis, buccinator)
- Posterior belly of digastric
- Stylohyoid
- Stapedius
- Auricular muscles
D. Cranial nerve
- Facial nerve CNVII
E. Other
- Lymphoid tissue of tonsil proper
- Hillocks of His are formed by 1st and 2nd pharyngeal arches
THIRD BRANCHIAL/PHARYNGEAL ARCH:
A. Arch Artery
- Common carotid artery
- Internal carotid artery
B. Skeletal Elements
- Inferior body and greater cornu of hyoid
C. Muscles
- Stylopharyngeus muscle
D. Cranial nerve
- Glossopharyngeal nerve CNIX
FOURTH BRANCHIAL/PHARYNGEAL ARCH:
A. Arch Artery
- Aortic arch (between right and left carotids)
- Right subclavian artery
B. Skeletal Elements
- Thyroid cartilage
- Cuneiform laryngeal cartilages
- Epiglottis
C. Muscles
- Pharyngeal constrictors
- Cricothyroid
- Levator veli palatini
D. Cranial nerve
- Superior laryngeal branch of vagus nerve (CNX)
SIXTH BRANCHIAL/PHARYNGEAL ARCH:
A. Arch Artery
- Ductus arteriosus
- Pulmonary artery roots
B. Skeletal Elements
- Cricoid cartilage
- Arytenoid cartilages
- Corniculate cartilages
C. Muscles
- Intrinsic laryngeal muscles (except cricothyroid)
- Striated muscle in upper esophagus
D. Cranial nerve
- Recurrent laryngeal branch of vagus nerve (CNX)
Cummings Chapter 202, figure 202.5
List all the pharyngeal pouch derivatives
FIRST BRANCHIAL/PHARYNGEAL POUCH
- Elongates and incorporates into the temporal bone and forms the tubotympanic recess
- Eventually tubotympanic recess becomes middle ear and eustachian tube
- Most lateral portion of the pouch, with the closing plate of the first pharyngeal cleft, forms the inner layer of the Tympanic membrane
SECOND BRANCHIAL/PHARYNGEAL POUCH
- Epithelial lining of tonsillar fossa and palatine tonsil
- Underlying mesenchymal elements contribute to lymphoid tissue of tonsil proper
THIRD BRANCHIAL/PHARYNGEAL POUCH
- Lateral wall of piriform sinus
- Separated into superior and inferior portions
- Superior portion = paired inferior parathyroid glands
- Inferior portion = Thymic tissue which eventually migrates into neck/retrosternal mediastinum to form thymus
- Aberrant migration of the third pharyngeal pouch may result in ectoptic inferior parathyroid or thymus tissue
FOURTH BRANCHIAL/PHARYNGEAL POUCH
- Superior parathyroid glands
- Apex of piriform sinus
FIFTH/SIXTH BRANCHIAL/PHARYNGEAL POUCH:
- aka. Ultimobranchial body –> eventually become parafollicular cells (C-cells) responsible for calcitonin
- Sometimes considered as fourth branchial pouch?
Cummings 202.4 Ch 202
List all the pharyngeal cleft derivates
FIRST PHARYNGEAL CLEFT:
- External auditory meatus/canal
SECOND, THIRD, FOURTH, SIXTH PHARYNGEAL CLEFT
- Cervical sinus of His (eventually degenerates)
Cummings Figure 202.4 (Chapter 202)
Describe the embryological development of the tongue
Pharyngeal arches 1-4 all contribute to tongue development
- 4 weeks GA: lateral lingual swelling + medial lingual swelling (tuberculum impair) from the first branchial arch form the anterior two thirds of the tongue
- Sensory innervation = lingual nerve branch of V3
- Taste = chorda tympani (branch of CNVII) - 2nd-4th arch = posterior third of the tongue (first forms the copula or hypobranchial eminence)
- Sensory and taste = glossopharyngeal nerve (from the third arch)
- Posterior tongue (vallecula) and epiglottis are innervated by the superior laryngeal branch of the vagus (fourth arch) - Junction between anterior and posterior tongue is V-shaped = terminal sulcus
- Occipital/high cervical somites form extrinsic tongue muscles
- Intrinsic tongue musculature differentiates from migration of myoblasts from occipital (high cervical) somites
- Innervated by hypoglossal nerve except for palatoglossus (pharyngeal plexus of the vagus)
Fig 202.7 Cummings Ch 202
Define Epipericardial ridge, and the 4 muscles and 2 nerves which are derived from it
An elevation of mesoderm separating the developing pharyngeal region from the embryonic pericardium
TITS 11, 12:
1. Trapezius
2. Infrahyoid muscle
3. Tongue
4. SCM
5. CNXI
6. CNXII
What are the rules of branchial arch anomaly relationships?
- Runs deep to own arch structures
- Runs superficial to next arch structures
Describe the embryological development of the thyroid gland. What are two main congenital errors that can occur?
- Begins as a solid swelling of endoderm in the midline of the posterior one-third of the tongue
- Point of origin = foramen cecum (invaginates at week 5 GA)
- Thyroglossal duct descendings inferiorly in the developing neck between 2nd and third arches (therefore persistence may be included within body of hyoid)
- 7 week GA: Thyroid gland reaches final destination in neck + parathyroid glands take their positions adjacent to the thyroid gland + ultimobranchial body infiltrates posterior aspects of the lateral thyroid lobes
- Thyroid gland is functional by 10-12 week GA
- Thyroglossal duct normally collapses and atrophies
Errors:
1. Abnormal migration = ectopic thyroid tissue
2. Persistent duct = thyroglossal duct cyst
Discuss the embryology of the larynx
- 4 weeks GA: Laryngotracheal groove forms in the ventral wall of the primitive pharynx
- 5-7 weeks GA: Laryngotracheal diverticulum buds and elongates, separated from dorsal foregut by tracheoesophageal septum; Arytenoid swellings from neural crest cell-derived mesenchyme of the 4th and 6th arches
- 8-9 weeks GA: Epithelial proliferation obliterates laryngeal lumen
- 10 weeks GA: Recanalization of the larynx
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