Lecture 2: Arterial supply + venous drainage of face/head

Question 1

Common Carotid Artery

Answer 1

Ascends with neck to superior border of thyroid cartilage/C3-C4 vertebral level

• Birfucates –> internal/external carotid a
• As it ascends, positioned MEDIAL to IJV.
• Vagus n is POSTERIOR, between artery and vein
• All 3 in carotid sheath

Question 2

Internal carotid artery

Answer 2

• Passes deep to posterior belly of digastric and stylohyoid muscles
• Crossed by hypoglossal n (passes superficial to both internal and external carotid arteries)

Question 3

ICA p 2

Answer 3

• Ascends anterior to transverse process of C1-C3 to reach base of skull; passes into carotid canal (petrous temporal bone) to reach cranial cavity (middle cranial fossa)
• No branches in neck
• Major source of blood to brain and orbit

Question 4

Four parts of ICA

Answer 4

1. Cervical part: bifurcation of CCA to lower end of carotid canal
2. Petrous part: pass through carotid canal (in petrous temporal bone)
3. Cavernous: course through cavernous sinus (along body of sphenoid)
4. Cerebral: after piercing dura (near anterior clinic process), ICA gives off ophthalmic a before terminating as anterior and middle cerebral arteries

Question 5

Ophthalmic a

Answer 5

Emerges from internal carotid immediately upon leaving cavernous sinus

• Enters orbit via optic canal
• Several branches (lacrimal, ciliary, ethmoidal, muscular) + 2 to forehead: supraorbital and supratrochlear

Question 6

External carotid a

Answer 6

Deep to posterior belly of digastric and stylohyoid muscles
- Posterior to ramus of mandible, embedded in parotid gland
Mainly supply structures external to skull

Question 7

ECA branches

Answer 7

1. Superior thyroid a
2. Ascending pharyngeal a
3. Lingual a
4. Facial a
5. Occipital a
6. Posterior auricular a
7. Superficial temporal a
8. Maxillary a

Question 8

Superior thyroid a

Answer 8

Passes anteroinferior, DEEP to infra hyoid muscles to reach thyroid gland
- Also gives off branches to local muscles – gives rise to superior laryngeal a (larynx)

Question 9

Ascending pharyngeal a

Answer 9

Near origin of ECA and smallest branch

• Ascends between ICA and pharynx to base of skull
• Sends branches to pharynx

Question 10

Lingual a

Answer 10

Arises from anteromedial aspect of ECA, between superior thyroid and facial arteries

• Crossed by hypoglossal n
• Passes deep to stylohyoid and posterior digastric muscles before disappearing deep to hyoglossus
• Passes to inferior aspect of tongue -> deep lingual and sublingual branches
• Primary blood supply to tongue and floor of oral cavity

Question 11

Facial a

Answer 11

Deep to digastric and stylohyoid muscles and medial to ramus/angle of mandible

• Passes along lower border of mandible, where it has a close relationship to submandibular gland
• Prior to entering face, gives off submental a
• Hooks around inferior border of mandible and enters face

Question 12

Facial branches of facial a

Answer 12

Inferior labial a
Superior labial a
Lateral nasal branch
Angular a
– terminal part of facial a as it travels to medial angle of eye
–Forms anastomosis with ophthalmic a (branch of ICA)

Question 13

Occipital a

Answer 13

Arises from posterior aspect of ECA, opposite origin of facial a

• • Passes posteriorly, parallel and deep to posterior belly of digastric as it courses to posterior scalp
• -Several branches that supply structures in area, scalp+muscles in the area

Question 14

Posterior auricular a

Answer 14

Small posterior branch, ascends posteriorly between EAM and mastoid process
- several branches to structures in area, including posterior auricle and muscles in the area

Question 15

Superficial temporal a

Answer 15

Originates within parotid gland

• Between neck of mandible and EAM, enters temporal fossa and terminates by dividing into frontal/parietal branches
• • TRANSVERSE FACIAL A- superficial to masseter, inferior to zygomatic arch

Question 16

Maxillary a

Answer 16

• Arises within parotid gland, posterior to neck of mandible
• Medial to mandible to enter infra temporal fossa
• Within infra temporal fossa, may pass superficial OR deep to lateral pterygoid muscle
• Divided into 3 parts by lateral pterygoid muscle
• Passes through pterygomaxillary fissure to enter pterygopalatine fossa

Question 17

Maxillary a (1st or mandibular part)

Answer 17

1. Deep auricular a - pierces wall of EAM, supplies lateral surface of tympanic membrane
2. Anterior tympanic a - traverses petrotympanic fissure and supplies medial surface of tympanic membrane
3. Middle meningeal a - traverses foramen spinosum to enter middle cranial cavity, blood supply: dura mater
4. Accessory meningeal a - foramen ovale -> middle cranial cavity -> dura mater
5. Inferior alveolar a: mandibular foramen -> mandibular canal; mandibular teeth and gingiva

Before passing into bone, gives off mylohyoid branch (travels with n)
2nd premolar: divides into incisor/incisive and mental branches
Incisive branch to midline–> anterior teeth/gingiva
Mental branch -> mental foramen -> muscles/skin of chin

Question 18

Max artery 2nd or pterygoid part

Answer 18

1. Masseteric a: superior to mandibular notch –> deep surface of masseter muscle
2. Deep temporal a (anterior and posterior): ascends to supply temporal muscle
3. Pterygoid arteries: supply pterygoid muscles
4. Buccal a: buccinator

Question 19

Max Artery 3rd or Pterygopalatine Part

Answer 19

1. Posterior superior alveolar a: traverses alveolar foramen; supplies max molars, premolars, adjacent ging tissue as well as lining of maxillary sinus
2. Infraorbital a: passes through inferior orbital fissure –> infraorbital groove –> infraorbital canal –> infraorbital foramen; supplies inferior eyelid, lateral nose and superior lip; along course gives rise to anterior alveolar a (max canine, incisors and adj gingival tissue)
   BOTH supply max sinus
3. Descending palatine a: descends through greater palatine canal –> greater and lesser palatine arteries and pass through same named foramina; supply mucous membrane/glands of soft and hard palate and maxillary gingival tissue
4. Artery of pterygoid canal: passes through pterygoid canal; supplies the nasopharynx, pharyngotymapnic tube and tympanic cavity
5. Pharyngeal a: passes through palatovaginal canal; supplies nasopharynx
6. Sphenopalatine a: terminal branch of maxillary a, passes through sphenopalatine foramen to reach nasal cavity; supplies portion of nasal cavity, including nasal septum and anterior hard palate

Question 20

Venous Drainage: Cranial Cavity

Answer 20

Blood from brain empties into dural venous sinuses

• Blood from scalp may also communicate with dural venous sinuses via emissary veins, pass through openings in cranial wall
• — Emissary veins allow communication between veins outside skull and dural venous sinuses (inside skull) –> potential spread of infection
• Diploic veins occupy channels in diploe of cranial bones

Question 21

Dural venous sinuses

Answer 21

Endothelial-lined spaces between periosteal and meningeal layers of dura

Question 22

Superior sagittal sinus

Answer 22

Occupies convex superior attaches border of falx cerebri

-Begins near crest Galli and ends near internal occipital protuberance, at confluence of sinuses

Question 23

Inferior sagittal sinus

Answer 23

Occupies concave inferior free border of falx cerebri

-Ends in straight sinus

Question 24

Straight sinus

Answer 24

Formed by union of inferior sagittal sinus and great cerebral vein

• Joins confluence of sinuses
• Located at junction of falx cerebri and tentorium cerebelli

Question 25

Occipital sinus

Answer 25

Occupies attached border of falx cerebelli and ends superiorly in confluence of sinuses

Question 26

Confluence of sinuses

Answer 26

Union of superior sagittal, straight, occipital and transverse sinuses

Question 27

Transverse sinus

Answer 27

- Passes from confluence of sinuses, laterally along attached margin of tentorium cerebelli - Laterally, where sinus passes from tentorium cerebelli, it becomes sigmoid sinus

Question 28

Sigmoid sinus

Answer 28

- Originates where transverse sinus leaves tentorium cerebelli - S-shaped as it descends and passes through in posterior cranial fossa - Continues inferiorly as IJV after traversing jugular foramen

Question 29

Cavernous Sinus

Answer 29

Located on either side of sella turcic (sphenoid) | -Drains posteroinferiorly through superior and inferior petrosal sinuses

Question 30

Superior petrosal sinus

Answer 30

- Located along anterior margin of tentorium cerebelli | - Passes from posterior end of cavernous sinus and terminates where it joins transverse sinus

Question 31

Inferior petrosal sinus

Answer 31

Originates at posterior end of cavernous sinus, passes inferiorly and empties into proximal aspect of IJV

Question 32

Cavernous sinus

Answer 32

Structures passing cavernous sinus include: 1. ICA 2. Internal carotid plexus (sympathetic nerves) 3. CN3 4. CN4 5. CN6 6. CNV1 7. CNV2 these structures separated from blood in sinus by endothelial cells

Question 33

Superficial Temporal Vein

Answer 33

Begins from widespread network of veins in scalp - Drains blood from scalp, anterior to auricle - Near auricle, superficial temporal vein enters parotid gland

Question 34

Maxillary Vein

Answer 34

Short trunk accompanying 1st part of maxillary artery - Derived from union of veins of pterygoid venous plexus (deep network of vein in infra temporal fossa) - Union of maxillary and superficial temporal veins occurs within parotid gland and forms retromandibular vein

Question 35

Retromandibular vein

Answer 35

Courses posterior to ramus of mandible and descends through parotid gland, superficial to ECA and deep to facial n Divides into anterior and posterior branches

Question 36

Posterior branch of retromandibular vein

Answer 36

Joins posterior auricular vein --> external jugular vein (union occurs just after exiting parotid gland)

Question 37

Anterior branch of retromandibular vein

Answer 37

Joins facial vein which drains into IJV (sometimes called common facial vein)

Question 38

Facial Vein

Answer 38

Formed by union of supraorbital and supratrochlear veins at medial angle of eye - Angular vein from its origin (medial eye) -> along lateral aspect of nose - Receives several veins (superior, labial, inferior labial, submental veins) before uniting with anterior branch of retromandibular vein - Communicates with pterygoid venous plexus

Question 39

Deep Facial Veins and Pterygoid Venous Plexus

Answer 39

- Facial vein communicates with pterygoid venous plexus via deep facial veins and infraorbital vein -From pterygoid venous plexus, blood can reach cavernous sinus POTENTIAL SPREAD OF INFECTION

Question 40

Routes for Spread of Infection of Embolism

Answer 40

1. Facial vein --> deep facial vein --> pterygoid venous plexus --> emissary vein --> cavernous sinus 2. Infraorbital vein --> pterygoid venous plexus --> emissary vein --> cavernous sinus 3. Supraorbital vein --> ophthalmic vein --> cavernous sinus