Embryology Flashcards
Describe the general organisation of each Pharyngeal Arch.
- Ectoderm covering
- Mesenchyme core
- Endoderm lining
- Each has associating cartilage, artery, nerve
- Pharyngeal Clefts separate each arch externally
- Pharyngeal Pouches separate each arch internally
- Pharyngeal membrane between clefts and pouches
Describe the structure of the Neural Tube and their derivates in terms of brain.
- Prosencephalon -> Forebrain
- Mesencephalon -> Midbrain
- Rhombencephalon -> Hindbrain
List the derivates of 1st Pharyngeal Arch in terms of the associating:
- Nerve
- Artery
- Cartilage
- N: CN V Trigeminal
- A: disappears
- C: Meckel’s Cartilage -> template of Mandible & Malleus & Incus
List the derivates of 2nd Pharyngeal Arch in terms of the associating:
- Nerve
- Artery
- Cartilage
- N: CN VII Facial
- A: disappears
- C: Reichert’s Cartilage -> Stapes & Styloid Process of Temporal Bone & Upper Hyoid Bone
List the derivates of 3rd Pharyngeal Arch in terms of the associating:
- Nerve
- Artery
- Cartilage
- N: CN IX Glossopharyngeal
- A: Internal Carotid Arteries
- C: Lower Hyoid Bone
List the derivates of 4th Pharyngeal Arch in terms of the associating:
- Nerve
- Artery
- Cartilage
- N: Superior Laryngeal Br of CN X Vagus
- A: Brachiocephalic Trunk (right) & Aortic Arch (left)
- C: Epiglottis & Laryngeal cartilages (together with 6th Pharyngeal Arch)
List the derivates of 6th Pharyngeal Arch in terms of the associating:
- Nerve
- Artery
- Cartilage
- N: Recurrent Laryngeal Br of CN X Vagus
- A: Pulmonary Trunk
- C: Epiglottis & Laryngeal cartilages (together with 4th Pharyngeal Arch)
Describe the development of the associated arteries of Pharyngeal Arch, hence their relationships with Vagus Nerve.
- Aortic Sinus associated to 4th Pharyngeal Arch develop asymmetrically
- Right: Brachiocephalic Trunk
- Left: Aortic Arch
- R. Recurrent Laryngeal Br. hooks under Brachiocephalic Trunk
- L. Recurrent Laryngeal Br. hooks under Aortic Arch
Which side of Recurrent Laryngeal Nerve is more likely to be damaged? Why and how? What symptoms may it cause?
- Left, due to asymmetric development of 4th Pharyngeal Arch
- Left arch -> Aortic Arch (whereas right arch -> Brachiocephalic Trunk)
- Aortic Arch Aneurysm
- Enlarged Mediasternal Lymph Nodes
- Brachial/Oesophageal Carcinoma
- Mitral Stenosis -> Enlarged left ventricle -> lifted Pulmonary Trunk
- Compression on Recurrent Laryngeal N -> Vocal Cord paralysis -> hoarseness in voice
Describe the artery derivates of each Pharyngeal Arch.
- 1st & 2nd: disappear
- 3rd: Internal Arteries
- 4th: (right) Brachiocephalic Trunk & (left) Aortic Arch
- 6th: Pulmonary Trunk
Describe the nerve derivates of each Pharyngeal Arch.
- 1st: CN V Trigeminal
- 2nd: CN VII Facial
- 3rd: CN IX Glossopharyngeal
- 4th: Superior Laryngeal Br. of CN X Vagus
- 6th: Recurrent Laryngeal Br. of CN X Vagus
Describe the cartilage derivates of each Pharyngeal Arch.
- 1st: Meckel’s Cartilage -> template of Mandible & Malleus & Incus
- 2nd: Stapes & Styloid process of Temporal Bone & Upper Hyoid Bone
- 3rd: Lower Hyoid Bone
- 4th & 6th: Laryngeal cartilages & Epliglottis
Describe the derivates of each Pharyngeal Cleft.
- 1st: External Acoustic Canal
- 2nd: covers all other clefts -> Cervical Sinuses -> obliterate
Describe the derivates of each Pharyngeal Pouch.
- 1st: Eustachian Tube & Tympanic Cavity
- 2nd: Palatine Tonsils
- 3rd: Thymus & dorsal: Superior Parathyroid gland
- 4th: Thyroid C cells & dorsal: Superior Parathyroid gland
What are Cervical Sinuses? What happens to them during embryology development? What may the failure of this development cause?
- 2nd Pharyngeal cleft covers clefts of 3rd to 6th -> Cervical Sinuses
- Obliterate in normal situation
- Failure -> Branchial Cyst/Fistula
Describe the cartilage derivates of each Pharyngeal Arch.
- 1st: Meckel’s Cartilage -> template of Mandible & Malleus & Incus
- 2nd: Stapes & Styloid process of Temporal Bone & Upper Hyoid Bone
- 3rd: Lower Hyoid Bone
- 4th & 6th: Laryngeal cartilages & Epiglottis
Describe the main structures that responsible for the development of the face. What structures do them give rise to?
- 1 Stomatodeum -> Buccopharyngeal membrane disappear -> Mouth opening
- 1 Frontonasal Prominence -> Forehead + Nose + Middle Upper Palate + Philtrum + Upper 4 Incisors
- 2 Maxillary Prominences -> Cheeks + Lateral Upper Palate and Lip + Upper Jaw
- 2 Mandibular Prominences -> Lower Lip and Jaw
Describe briefly the development of nose.
- Nasal Placodes appear on FNP
- FNP sinks -> Nasal Pits + Medial and Lateral Nasal Prominences + Nasal Septum
Describe briefly the development of eyes.
- Forebrain grows outward -> in contact with Optic Placode -> Lens
- Facial prominences push eyes upwards and medially
What is Neurulation? What important structure does it form, that responsible for development of special sense organs.
- Notochord directs overlying Ectoderm to become Neuroectoderm -> thickens & folds -> Neural Tube
- Cells at lateral Neural Tube (Neural crest) migrate into Mesoderm -> Neural Placodes
Why is drinking alcohol dangerous to foetal development?
- Freely transports across Placenta
- Toxic to Neural Crests
- Influence development of Special sense organs
Describe briefly, the separation between nasal and oral cavities.
- Fusion between each Medial Nasal Prominence & each Maxillary Prominence -> Intermaxillary Segment -> Primary Palate
- 2 Maxillary Prominences -> 2 Palatal Shelves
- Fusion of 2 Palatal Shelves & Nasal Septum -> Definite Palate
How does Lateral Cleft Lip happen?
Failure of fusion between Maxillary Prominence & Medial Nasal Prominence on one side
How does Cleft Lip and Palate happen?
Failure of fusion between Palatal Shelves & Maxillary Prominence & Medial Nasal Prominence on one side
What is Intermaxillary Segment? List some derivates of it.
- Fusion between each Medial Nasal Prominence & each Maxillary Prominence
- Intermaxillary Segment -> Primary Palate & Upper 4 Incisors & Philtrum
How does a baby with Foetal Alcohol Syndrome commonly present?
- Smooth philtrum
- Thin upper lip
- Growth & mental retardation
Describe the embryonic origin of the Posterior Pituitary Gland.
A down-growth of the Diencephalon in the midline = the Infundibulum -> extends towards Oral cavity & connected with the brain via Pituitary Stalk
Describe the embryonic origin of the Anterior Pituitary Gland.
Up-growing of the oral cavity forms Raiketh Pouch -> wraps Pituitary Stalk -> Anterior Pituitary
Describe the embryonic origin of the Hypothalamus.
The part of Diencephalon giving Infundibulum = a down-growth in midline gives rise to Posterior Pituitary Gland
Where do the Anterior and Posterior Pituitary glands locate?
Pituitary Fossa/Sella Turcica of Sphenoid bone
Describe how the Pharyngeal arches responsible for the development of the tongue.
- 1st -> Lateral swellings & Tuberculum Impar -> Lateral overtakes
- 2nd & 3rd -> Cupola -> 3rd arch overtakes
- 4th -> Epiglottal swelling
- Extensive degeneration of the arches -> drops the Tongue (except the Ligual Frenulum)
Describe how the Pharyngeal arches responsible for the innervation of the tongue.
- 1st -> Lingual br. of Mandibular (CN Viii) -> general sensory of anterior 2/3
- 3rd -> Glossopharyngeal (CN IX) -> general sensory of posterior 1/3
- 2nd -> Chorda Tympani (CN VII) -> hjks Lingual N (CN Viii) -> taste of anterior 2/3
- 3rd -> Glossopharyngeal (CN IX) -> taste of posterior 1/3
- Migration of myogenic cells from Hypoglossal N -> motor
Describe the embryonic origin of the Thyroid Gland.
- Expansion of mesenchyme between Tuberculum Impar & Cupola at floor of pharynx
- Bifurcates & bi-lobes connected by Isthmus
- Bi-lobes descend & connected to the tongue by Thyroglossal Duct
What could be a non-canceous and painless swelling inferior to the Hyoid bone?
Thyroglossal cyst as the Thyroid gland descends down from the pharynx during embryonic development
Why may a parathyroid gland be found within the Thymus?
- The Thymus derived from 3rd pouch ventrally
- The Superior & Inferior Parathyroid glands derived from 4th & 3rd pouch respectively
- The 3rd pouch descends and passes over the 4th, forming the Inferior Parathyroid
