NEET MDS Lessons
Anatomy
The Arteries of the Face
- The superficial arteries are derived from the external carotid arteries.
The Facial Artery
- This is the chief artery of the face.
- It arises from the external carotid artery and winds its way to the inferior border of the mandible, just anterior to the masseter muscle.
- It hooks around the inferior border of the mandible and grooves the bone. Here the artery is superficial, just beneath the platysma and its pulsation can be felt.
- In its course over the face to the medial angle of the eye, the facial artery crosses the mandible, buccinator muscle, and maxilla.
- It lies deep to the zygomaticus major.
- The facial artery ends by sending branches to the lip and side of the nose.
- The part of the artery that runs along the side of the nose to supply the eyelids is called the angular artery.
The Superficial Temporal Artery
- This artery is the smaller of the two terminal branches of the external carotid artery (the other is the maxillary artery).
- It begins deep to the parotid gland, posterior to the neck of the mandible, and ascends superficial to the posterior end of the zygomatic process of the temporal bone. It then enters the temporal fossa.
- The superficial temporal artery ends in the scalp by dividing into the frontal and parietal branches.
- Pulsation of this artery can be felt by compressing the root of the zygomatic process of the temporal bone.
The Transverse Facial Artery
- This small artery arises from the superficial temporal artery before it emerges from the parotid gland.
- It crosses the face superficial to the masseter muscle, about a fingerbreadth inferior to the zygomatic arch.
- It divides into numerous branches that supply the parotid gland and duct, the masseter muscle, and the skin of the face.
- It anastomoses with branches of the facial artery.
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First pouch |
Auditory tube, which comes in contact with epithelial line of first pharyngeal cleft, where future external acoustic meatus will form. Distal portion will form tympanic cavity (lining will become eardrum) Proximal portion will become auditory tube |
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Second pouch |
Forms buds that penetrate surrounding mesenchyme, which together form the palatine tonsils |
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Third pouch |
Forms thymus and inferior parathyroid glands |
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Fourth pouch |
Forms superior parathyroid glands |
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Fifth pouch |
Forms utlimobranchial body |
Initially, four clefts exist; however, only one gives rise to a definite structure in adults.
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1st pharyngeal cleft |
Penetrates underlying mesenchyme and forms EAM. The bottom of EAM forms lateral aspect of tympanic cavity. |
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2nd pharyngeal cleft |
Undergoes active proliferation and overlaps remaining clefts. It merges with ectoderm of lower neck such that the remaining clefts lose contact with outside. Temporarily, the clefts form an ectodermally lined cavity, the cervical sinus, but this disappears during development. |
Internal Ear
- Osseous labyrinth: a complex system of cavities in the substance of the petrous bone.
- Membranous labyrinth: filled with endolymph, bathed in perilymph.
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Mesodermal Origin |
Muscles |
Innervation |
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Somitomeres 1, 2 |
Superior, medial and ventral recti |
Oculomotor (III) |
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Somitomere 3 |
Superior oblique |
Trochlear (IV) |
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Somitomere 4 |
Jaw-closing muscles |
Trigeminal (V) |
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Somitomere 5 |
Lateral rectus |
Abducens (VI) |
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Somitomere 6 |
Jaw-opening and other 2nd arch muscles |
Facial (VII) |
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Somitomere 7 |
Stylopharyngeus |
Glossopharyngeal (IX) |
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Somites 1, 2 |
Intrinsic laryngeals |
Vagus (X) |
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Somites 2-5 |
Tongue muscles |
Hypoglossal (XII) |
Nerve Supply of the Muscles of the Orbit (pp. 715-6)
- Three cranial nerves supply the muscles of the eyeball; the oculomotor (CN III), trochlear (CN IV) and abducent (CN IV) nerves.
- All three enter the orbit via the superior orbital fissure.
- The trochlear nerve supplies the superior oblique muscle.
- The abducent nerve supplies the lateral rectus muscle.
- The oculomotor nerve supplies everything else.
- A mnemonic that is used is this formula for this strange sulfate: SO4(LR6)3
Genioglossus Muscle
- Origin: Mental spine of the mandible.
- Insertion: Dorsum of the tongue and hyoid bone.
- Nerve Supply: Hypoglossal nerve (CN XII).
- Arterial Supply: Sublingual and submental arteries.
- Action: Depresses and protrudes the tongue.