VAN 121: Veterinary Gross Anatomy-II (2+2)

INTERNAL MAXILLARY ARTERY

• This is the larger of the two terminal branches of the external carotid artery.
• It passes obliquely forwards and upwards on the lateral aspect of the pharynx and reaches the lower part of the temporal fossa.
• It runs in company with the maxillary nerve to the maxillary hiatus.
• Here, it divides into two sets of branches, the malar and infraorbital and greater palatine and sphenopalatine arteries.

Collateral branches

• Branches to the pterygoid muscles (pterygoid arteries). Parotidotemporal branch arises from the posterior face of the artery and it divides into parotidoauricular and temporomeningeal branches. The former divides into parotid and auricular branches of which the former is distributed to the parotid salivary gland and the latter gains the concave face of the concha and supplies the skin. The temporomeningeal branch enters the temporal canal passes through it detaches a meningeal branch to the duramater and then passes out of the canal into the temporal fossa through one of the foramina and is distributed to the temporalis muscle. This branch is the posterior deep temporal artery.
• Mandibuloalveolar artery arises from the anterior face of the artery passes downwards and forwards over the medial pterygoid on the medial face of the vertical ramus enters the mandibular canal through the inferior maxillary foramen in company with the vein and nerve passes through the canal gains exit at the mental foramen and divides into labial artery to supply the lower lip. At the mental foramen an incisor branch is given off by the inferior dental artery which passes through the incisor canal in the body of the mandible below the roots of the incisors and its branches are distributed to them. Along its course the mandibuloalveolar artery gives off pterygoid branches to the medial pterygoid muscle and dental branches to the lower cheek teeth, the alveolar periosteum and bone.
• The middle meningeal artery arises from the posterior face about the level of the preceding branch passes upwards and backwards gains the company of the mandibular nerve enters the cranium through the foramen ovale and assists in the formation of the rete mirabile cerebri.
• The anterior deep temporal artery arises from the posterior face a little above the preceding gains the anterior part of the temporal fossa enters the deep face of the temporalis muscle and is distributed to it.
• Buccinator artery arises from the anterior face of the artery passes forwards in company with the buccinator nerve. It supplies the pterygoid, masseter and buccinator muscles.
• Anterior meningeal arteries are two or three branches arising from the internal face of the artery pass towards the foramen orbito-rotundum in company with the maxillary nerve enter the cranium and concur in the formation of rete mira bile cerebri. These arteries take the place of the internal carotid of other animals.
• External ophthalmic artery arises from the internal maxillary artery at the level of the temporal fossa. It passes upward crosses the maxillary nerve reaches the orbit penetrates the periorbita passes under the superior rectus and forms a rete mirabile orbitale. It gives off the frontal and nasal arteries. It also gives off in its course lacrimal branch to lacrimal gland, muscular branches to the muscles of the eyeball, ciliary arteries and the central artery of the retina.
• The ciliary arteries arise from the ophthalmic or its muscular branches. They pass between the medial rectus and retractor oculi reach the sclera and divide into anterior and posterior branches. The anterior branches are distributed to the ciliary processes and ciliary muscle. The posterior branches mostly end in the chorioid coat as the short ciliary arteries but branches pass between sclera and chorioid gain the iris, divide and form an arterial circle the circulus iridis major. From this, secondary branches are detached which form a second circle around the pupillary margin, the circulus iridis minor.
• The central artery of the retina is a slender vessel and it supplies the retina.
• The frontal or supraorbital artery passes upwards enters the supraorbital canal gains the frontal sinus and supplies the mucous membrane. The nasal or ethmoidal artery passes backwards gains the cranium through the ethmoidal foramen near the cribriform plate of ethmoid enters the nasal cavity through one of the large foramina near the crista galli and is distributed to the posterior part of nasal mucous membrane.