Deck 2: Head spaces, Vascular Supply to neck

List the 2 parts of the Cranium/skull.

1. Neurocranium - “Cranial vault”

2. Viscerocranium - “Facial skeleton”

What is the Neurocranium?

→ encases the brain & cranial meninges

• contains proximal parts of the cranial nerves & brain vasculature 

How many bones form the Neurocranium? List them.

8 bones

• 4 singular (midline) bones:

  1. Frontal

  2. Ethmoid

  3. Sphenoid

  4. Occipital

• 2 paired bones (bilateral):

  1. Temporal (2)

  2. Parietal (2)

How many bones form the Viscerocranium? List them.

“My pal zoe likes indoor vacations.. never mind”

• Maxilla (x2)

• Palatine (x2)

• Zygoma (x2)

• Lacrimal (x2)

• Inferior nasal concha (x2)

• Vomer

• Nasal (x2)

• Mandible

• Ethmoid*→ this appear in Neurocranium too

What’s the difference b/w an internal view vs inferior view?

What are cranial sutures?

Strong fibrous joints holding the bones of the skull together

List the major sutures.

1. Coronal - “crown”

2. Sagittal - splits left and right

3. Lambdoid

The cranial base is divided into 3 regional depressions called _______. They are:

1)

2)

3)

The cranial base is divided into 3 regional depressions called fossa

1. Anterior

2. Middle

3. Posterior

   

What 2 bony landmarks delineate the boundaries between the cranial fossae, and which fossae do they separate?

1) Sphenoid lesser wing → separates the anterior & middle fossae

2) Temporal bone petrous ridge → separates the middle & posterior fossae

“solid” portion)

What is a foramen, and what is its function in the skull?

→ Opening or hole in a bone

• allows passage of nerves, blood vessels, and other structures

• connects the brain with other parts of the body

List the main rooms of the house.

ACF – Anterior Cranial Fossa

MCF – Middle Cranial Fossa

PCF – Posterior Cranial Fossa

MS – Maxillary Sinus (paranasal sinus inside maxilla)

OC – Oral Cavity

NC – Nasal Cavity

OR – Orbit

Label the main rooms of the house laterally and frontally. Mentions which rooms the 3 main rooms (ACF, MCF, PCF), can’t directly connect to.

ACF = Middle or Posterior fossae

MCF = Nasal cavity, Oral cavity

PCF = Orbit, Nasal cavity, Oral cavity

What’s the only way the Pterygopalatine Fossa be viewed?

can only be viewed laterally

What are Ethmoid Air cells?

has multiple air spaces; considered a sinus

What is the Tentorium Cerebelli? Where is it attached?

→ a fold of the dura mater that separates the occipital and temporal lobes from the cerebellum and brainstem

• also separates the posterior cranial fossa

• attached along the petrous ridge of the temporal & occipital bone

• looks like a “tent”

What is the falx cerebri?

→ fold of dura mater that divides the brain hemispheres into left and right, running along the sagittal plane

• create spaces within the dura, which form part of the venous drainage system

Note: Orange part shows the part of the Falx Cerebri that split the hemispheres into 2. 

• it’s also near the front (whereas tentorium is near the back)

What is the Temporal Fossa?

→ contains the upper portion of the temporalis muscle

Location: area above the cheekbone

What is the Infratemporal Fossa?

→ Irregularly shaped space

Location:

• deep and inferior to the zygomatic arch (cheekbone)

  • under the temporal fossa

• deep to the ramus of the mandible (jawbone)

What are the arteries that make up the Infratemporal Fossa?

Branches of the Maxillary Artery:

1. Middle meningeal artery

2. Inferior alveolar artery

3. Deep temporal artery

4. Buccal artery

What are the veins that make up the Infratemporal Fossa?

Pterygoid venous plexus

What are the nerves that make up the Infratemporal Fossa?

1) Mandibular nerve (CN V3)

2. Auriculotemporal nerve

3. Buccal (long buccal) nerve

4. Lingual nerve

5. Inferior alveolar nerve

6) Chorda tympani nerve (CN VII)

7) Otic ganglion (PNS)

What are the muscles that make up the Infratemporal Fossa?

1. Temporalis muscle (inferior)

2. Pterygoid muscles (lateral & medial)

What are the joints that make up the Infratemporal Fossa?

Temporomandibular joint (TMJ) - allows for chewing, but also the first jaw that feel painful when ur stressed

List the muscles used for Mastication (chewing).

1. Masseter

2. Temporalis

3. Lateral pterygoid

4. Medial pterygoid

Where do the muscles used for mastication attach?

attach to the mandible creating the TMJ

List the nearby spaces the Infratemporal fossa is connected with. Mention the fissure

What’s the downside to these interconnected spaces within the Infratemporal fossa?

Infections (such as dental or deep facial infections) can spread from the teeth or jaw into deeper regions, potentially reaching the cranial cavity

What bones is Pterygopalantine fossa (PPF) bounded by?

1. Maxilla

2. Sphenoid

3. Palantine

List the contents of the Pterygopalantine fossa (PPF)?

→ major neurovascular hub in the deep face

1) Maxillary nerve (CNV2) + its branches

2) Maxillary artery (terminal) + its branches

3) Nerve of the pterygoid canal (Vidian nerve)

• Greater superficial petrosal nerve → preganglionic PNS fibers

• Deep petrosal nerve → postganglionic SNS fibers

4) Pterygopalatine ganglion

5) Accompanying veins (tributaries of the pterygoid venous plexus)

Which nerve and artery pass through the Pterygopalatine fossa, and what do they supply?

Maxillary nerve (CN V2) & Maxillary artery course through the PPF → supply the nasal cavity & palate

Which fibers synapse in the pterygopalatine ganglion?

pre-ganglionic PNS fibers from the Facial nerve (CNVII) via the greater petrosal nerve

What major regions does the Pterygopalatine fossa (PPF) communicate with? How?

Major regions of the viscerocranium

Which muscles connect the head to the thoracic skeleton and form boundaries of the neck regions? How are these muscles innervated?

1) Sternocleidomastoid (SCM)

2) Trapezius muscles

→ innervated by the spinal accessory nerve (CN XI), which exits the jugular foramen and passes deep to the SCM toward the trapezius to provide motor innervation

What are the actions of the sternocleidomastoid (SCM)?

Unilaterally: Tilts the head to the same side and rotates it to the opposite side

Bilaterally: Moves the neck in the sagittal plane (head moves down)

What are the actions of the trapezius?

Upper fibers: Elevate the scapula

Middle fibers: Retract the scapula

Lower fibers: Depress the scapula

Where are the SCM and trapezius located relative to each other?

SCM = anterior

Trapezius = posterior

What is the Platysma?

is a thin muscle of facial expression that overlies the deeper structures of the neck

What are Neck triangles?

→ musculoskeletal landmarks divide the neck into cervical triangles

What forms the palpable borders of the Posterior triangle of the neck?

• Clavicle (base)

• Trapezius muscle (posterior border)

• SCM (anterior border)

What are the main palpable landmarks in the neck region?

• Mastoid process

• Angle of mandible

• Laryngeal prominence (Adam’s apple)

• Jugular notch

List borders of the Carotid Triangle.

Superior – Digastric muscle

Lateral – SCM muscle

Inferior – Omohyoid muscle

Carotid Triangle

List the arteries of the Carotid Triangle.

1) Common carotid

2) Internal carotid

3) External carotid + its 5 branches:

1. Superior thyroid artery

2. Ascending pharyngeal artery

3. Lingual artery

4. Occipital artery

5. Facial artery

Carotid Triangle

List the veins of the Carotid Triangle.

1) Internal jugular vein

2) IJV Tributaries:

1. Superior/Middle thyroid vein

2. Lingual vein

3. Pharyngeal vein

4. Common facial vein

Carotid Triangle

List the nerves of the Carotid Triangle.

1) Cranial nerves - Vagus, Spinal Accessory & Hypoglossal

2) Other nerves - Ansa cervicalis + sympathetic chain (cervical part)

Carotid Triangle

List the lymph nodes of the Carotid Triangle.

Deep cervical lymph nodes

Carotid Triangle

List the other structures of the Carotid Triangle.

1. Carotid sinus

2. Carotid body

Where do the vertebral arteries originate and how do they travel?

Origin: Subclavian arteries

1. Ascends through the transverse foramina of the cervical vertebrae

2. Enter the cranium via the foramen magnum to supply the brain

3. After entering, they fuse to form the basilar artery

   • it’s formed along the medulla oblongata’s ventral surface

What does the Common carotid artery branch into? What do these branches supply?

1. External carotid - supplies the neck, lower jaw, and face

2. Internal carotid - supplies the brain

   

Where is the Common carotid artery enclosed?

enclosed within the carotid sheath in the neck

What is the Carotid sheath?

→ a fascial compartment that extends from the cranial base to the root of the neck

• sheath ends at the inferior opening of carotid canal 

What is the Carotid Sinus? Where is it found?

→ “Blood pressure sensor” - contains baroreceptors to monitor BP in the brain

• Action: Reads BP & stimulates reflex vasoconstriction if blood supply to brain drops (e.g., when standing up)

- it’s a “dilation” at the base of the internal carotid artery

What are the contents of the Carotid sheath?

Medial: Common & internal carotid arteries

Lateral: Internal jugular vein

Posterior: Vagus nerve (CN X)

List all the veins of the neck.

External jugular vein - drains superficial structures of the head and neck

Internal jugular vein - drains deep structures of the head and neck

Vertebral vein - drains the cervical spinal cord & posterior surface of the skull

What do the veins of the neck merge with, and what do they form?

All 3 veins merge with the subclavian vein → form the brachiocephalic vein

What is the Carotid body?

→ small piece of tissue b/w origins of the internal & external carotid

• chemoreceptor = mainly reads pO₂ (less pCO₂ and pH)

Which nerve primarily innervates the carotid sinus and carotid body? Describe the innervation path

Glossopharyngeal nerve

1) Sensory signals from the carotid body and carotid sinus travel through the sinus nerve (of Hering)

2) Signals reach the glossopharyngeal nerve (CN IX) → brainstem

What happens when glomus cells in the Carotid body detect ↓pH, ↑CO₂, or ↓O₂?

Sympathetic activation leading to:

1. ↑BP

2. ↑ HR

3. ↑ respiratory rate

How does the Carotid body respond to changes in BP?

↓ BP → afferents stimulate vasoconstriction

↑ BP → afferents stimulate vasodilation

List the branches of the External Carotid Artery. Mention what they supply.

SALFOP

List the Terminal branches of the External Carotid Artery. Mention what they supply.

“Terminal” - don’t anastomose 

What is the course of the internal carotid artery as it enters the cranial cavity?

Each internal carotid artery enters the cranial cavity via the carotid canal found in the temporal bone (petrous/hard part)

What is the Cavernous Sinus?

→ venous sinus located on either side of the pituitary gland

• “vein with contents” — meaning many important structures pass through or along it

• portion of the dura mater

Which cranial nerve travels alongside the internal carotid artery in the cavernous sinus?

Abducent nerve (CN VI)

Which cranial nerves are located in close proximity to the cavernous sinus, within its lateral wall?

1. Oculomotor nerve (CN III)

2. Trochlear nerve (CN IV)

What part of the brain do the internal carotid arteries supply?

anterior half of the cerebrum

Name the 3 branches of the Internal Carotid artery & what they supply. What is the internal carotid artery + its branches collectively referred to as?

1. Ophthalmic artery - eyes

2. Anterior cerebral artery - frontal and parietal lobes

3. Middle cerebral artery - midbrain and lateral surfaces of cerebral hemispheres

“Anterior circulation of the brain”

Which arteries supply the rest of the brain (not the anterior half)?

1. Vertebral arteries

2. Basilar arteries (comes from vertebral arteries)

List the 3 principal arteries of the brain. What are their origins?

1. Anterior cerebral artery (L & R)

2. Middle cerebral artery

3. Posterior cerebral artery

- Terminal branches of the Internal carotid arteries

-Terminal branches of the Basilar artery from the vertebra

What are the terminal branches of the Internal carotid arteries?

1. Anterior arteries (left & right)

2. Middle cerebral arteries

How are the left & right Anterior arteries connected to eachother?

Anterior communicating artery

What is another name for the posterior circulation of the brain?

vertebrobasilar system

How does the posterior circulation connect to the anterior circulation?

via the right and left posterior communicating arteries

Draw out the diagram showing how the following at connected.

• Anterior cerebral artery

• Anterior communicating artery

• Middle cerebral artery

• Posterior communicating artery

• Posterior cerebral artery

• Basilar artery

• Vertebral artery

• Arterial circle

The Cerebral Arterial Circle (Circle of Willis) reunites 3 vascular systems. What are they?

1) Vertebrobasilar system (posterior circ)

2) Left Internal carotid system (anterior circ)

3) Right Internal carotid system (anterior circ)

Which arteries connect the internal carotid arteries to the posterior cerebral arteries?

Posterior communicating arteries → allow the posterior and anterior circ (internal carotid) to form an anastomosis and complete the cerebral arterial circle (Circle of Willis)

If symptoms appear on both sides/bilateral of the body, what does that suggest about the artery supply?

1 artery supply (vertebrobasilar)

• b/c vertebral arteries anastomose into a single central vessel (basilar artery) → bilateral symptoms

If symptoms appear on only one side/unilateral, what does that suggest about the artery supply?

2 artery supply (internal carotids)

• b/c internal carotid arteries remain separate → unilateral symptoms

What does venous drainage from the brain occur via?

occurs via cerebral and cerebellar veins that drain into the adjacent dural venous sinuses

What is the function of the Meninges? 

1. Line the skull

2. Surround, and protect the brain

What is the Dura Mater?

→ Tough, fibrous outermost layer

• has 2 layers: Periosteal & Meningeal

  • layers are fused except where they form dural folds and dural venous sinuses

Which nerves transmit pain sensations from the dura mater?

1. Cervical nerves C2–C3

2. Trigeminal nerve (main)

3. Vagus nerve (CN X)

What is the Arachnoid Mater?

Thin, transparent, middle meningeal layer

What is the Pia Mater?

→ Delicate, vascularized innermost layer

• adheres tightly to the brain, following its gyri and sulci

What are Dural Venous Sinuses?

→ endothelium-lined venous channels located b/w the 2 layers of dura mater

• Drain venous most of the blood from the brain into the internal jugular vein

What is the Middle Meningeal Artery?

External carotid artery → Maxillary artery → Middle meningeal artery

• main blood supply to the Dura mater

• enters the skull through the foramen spinosum

  • lies in the middle cranial fossa (on internal surface of skull base)

What are grooves on the skull formed by?

1. Dural venous sinuses

2. Meningeal arteries (especially the MMA)

What is the pterion? Why is a fracture at the pterion clinically significant?

Pterion: is where the frontal, parietal, temporal, and sphenoid bones meet

• MMA runs under it, so a fracture in this area can rupture the MMA → epidural hematoma

  • Epidural hematoma: bleeding b/w the dura & skull that rapidly ↑ intracranial pressure