Lab Week 2 Notes: Skull, Sphenoid/Ethmoid, Paranasal Sinuses, and Spine

Week 2 Notes: Skull, Spine, and Lab Logistics (Comprehensive)

• Week context and logistics

  • Meeting location: week two in the lab space.
  • Weeks left: there are multiple weeks left in the term; discussion mentions “one, two, three” weeks left and that there is no lab next week (today).
  • Office hours: when Chris sends an announcement, the update shows who else reschedules theirs; useful for planning quizzes and lab times.
  • Quizzes and ticket-ins (ticket ins): these act as a 20-point buffer for the quiz to help if some questions are missed, with a max quiz grade of $100$. In practice, you can miss some questions on the quiz and still improve with the buffer.
  • Buffer question: If you select fewer questions, the buffer is still 20 points if you have them all correct; otherwise, it’s a percentage-based adjustment based on how many you got right.

• Quick quiz/logistics Q&A

  • Students ask if the 20-point buffer scales with the number of questions chosen. Answer: 20 points if you have them all right, otherwise it’s a percentage-based adjustment.

• Skull anatomy: overview and orientation

  • Skull bone count: total bones in the human skull = $22$.
  • Connections:
  • The frontal bone connects superiorly to another bone (the frontal), and medially to axial bones.
  • Naming convention: the processes (e.g., zygomatic process) are named for the bone they move toward (toward which bone the projection is oriented).
  • Sutures (fibrous, immovable joints):
  • Coronal suture
  • Sagittal suture
  • Lamboid suture
  • Squamous suture
  • Sutures are immovable and fuse over time.
  • Suture locations and orientation: front view highlights coronal suture across the skull, sagittal runs along the midline top; lamboid runs at the back; squamous is along the temporal region.
  • Temporal bone region: the squamous region is the flat, plate-like portion of the temporal bone.
  • Orientation tips for skull features:
  • Pterion and asterion (landmarks on the skull) help orient skull bones; their prefixes hint at their relationships.
  • Prefix ptery- means “wing-like.” The pteryon is the structure that touches the sphenoid bone (the wing-like connection).
  • Paranasal sinuses (air-filled cavities): there are $5$ paranasal sinuses located around the nasal cavity, aiding lightening of the skull and resonance.
  • Lab practice and study approach: emphasis on prefixes/suffixes to learn anatomical language; anatomy is largely memorization, reinforced by multiple reps and recall during class and quizzes.

• Ethmoid bone: anatomy and orientation

  • Ethmoid bone identification: you should be able to name the ethmoid bone.
  • Crista galli: the most superior projection on the ethmoid; orientation cue: the crista galli is on the anterior and superior part of the ethmoid.
  • Crista galli meaning: translates to “rooster’s nest” (rooster crown).
  • Cribriform plate: top plate with holes called olfactory foramina; these holes transmit olfactory nerves (sense of smell, olfaction).
  • Olfactory foramina/cribriform foramina: holes on the cribriform plate through which the olfactory nerves pass.
  • Perpendicular plate: middle sagittal plate that forms part of the nasal septum; articulates with the vomer bone below to create the bony nasal septum.
  • Conchae (nasal turbinates) in the ethmoid: middle nasal concha and superior nasal concha are part of the ethmoid; inferior nasal concha is a separate bone (not part of the ethmoid).
  • Lateral masses: portions of the ethmoid that house the ethmoid sinuses.
  • Orbital plate: the smooth portion of the ethmoid that contributes to the orbit.

• Sphenoid bone: orientation and key structures

  • Sella turcica (Turkish saddle): saddle-shaped depression on the sphenoid that houses the pituitary gland (hypophysis).
  • Hypophyseal fossa: the depression within the sella turcica where the pituitary sits.
  • Tuberculum sellae: the anterior portion of the saddle.
  • Dorsum sellae: the posterior portion of the saddle.
  • Lesser wings and greater wings of the sphenoid: two wings, with the optic canals located in the lesser wings.
  • Optic canals: canals for the optic nerves pass through the lesser wings of the sphenoid.
  • Superior orbital fissure: opening between the greater and lesser wings through which nerves/vessels pass.
  • Inferior orbital fissure: another orbital opening in the sphenoid region.
  • Pterygoid processes: wing-like projections inferiorly; the term pterygoid means wing-like.
  • Pterion and asterion (anatomical landmarks): pterion is where several bones meet near the sphenoid; asterion is another sutural landmark (in practice, used for orientation in skull anatomy).
  • Foramen landmarks on the sphenoid wing (great wing):
  • Foramen rotundum
  • Foramen ovale
  • Foramen spinosum
  • (Other foramina exist on the skull, but those three are on the greater wing and are commonly tested.)
  • Mnemonic for foramina order on the greater wing (top-to-bottom): “rigatoni over spaghetti”
  • Rotundum = top
  • Ovale = middle
  • Spinosum = bottom
  • Important clinical/memorization notes: these foramina are frequently tested in quizzes and practicals; knowing their relative positions helps with orientation in skull models.

• Zygomatic, maxilla, nasal bones, and vomer (unpaired vs paired)

  • Zygomatic bones: cheekbones.
  • Maxilla: upper jaw bone; paired bones.
  • Nasal bones: paired bones that form the bridge of the nose; listed as paired.
  • Frontal bone: unpaired bone.
  • Ethmoid bone: unpaired bone.
  • Vomer bone: unpaired bone forming part of the nasal septum (often referred to as the vomer; transcript uses “bomer/bomer bone” informally).

• Spine and vertebral column: overview

  • Regions and counts:
  • Cervical vertebrae: $7$
  • Thoracic vertebrae: $12$
  • Lumbar vertebrae: $5$
  • Sacral vertebrae: $5$ (fused)
  • Coccyx vertebrae: $3 ext{ to } 5$ (variable fusion)
  • Mnemonic for counts: “Breakfast at seven, lunch at twelve, dinner at five.”
  • Primary curvatures (present at birth): concave anteriorly (primary curves are thoracic and sacral).
  • Intervertebral discs: two components
  • Nucleus pulposus: inner jelly-like portion.
  • Annulus fibrosus: outer fibrous ring that keeps the nucleus pulposus in place.
  • Disc pathology terminology
  • Herniated disc: annulus fibrosus tears and nucleus pulposus leaks into spinal canal, causing pain due to nerve irritation.
  • Bulging disc: nucleus pulposus bulges without a tear in the annulus fibrosus; may press on nerves and cause pain.

• Cervical vertebrae: Atlas (C1) and Axis (C2)

  • Atlas (C1): supports the skull; articulates with occipital condyles; no vertebral body like other vertebrae.
  • Axis (C2): contains the dens (odontoid process) that allows rotation of the head.
  • Dens (odontoid process): the projection on C2 that nests with C1 to enable rotation.
  • Atlanto-occipital joint: between atlas and occipital bone; permits nodding movement (flexion/extension).
  • Atlantoaxial joint: between atlas (C1) and axis (C2); allows rotation (shake head “no”).
  • Atlantoaxial arrangement: atlas sits on the superior articular facets of the axis; atlas is held in place by the dens rotating atop the axis.
  • Atlas anatomy specifics:
  • Anterior arch and posterior arch
  • Anterior tubercle (anterior) and posterior tubercle (posterior)
  • Lateral masses: house the superior articular facets that contact the occipital condyles
  • Superior articular fossa (facet) on each lateral mass for articulation with the occipital condyles
  • Sagittal orientation cues in atlas: anterior side has the anterior arch with anterior tubercle; posterior side has posterior arch with posterior tubercle; occipital condyles sit on the superior facets.

• Characteristics of the atlas and axis (and vertebral features)

  • Vertebral body orientation: the body faces anteriorly toward internal organs; spinous processes point posteriorly.
  • For cervical vertebrae: distinctive features include
  • Transverse processus with transverse foramina (only in cervical vertebrae) – key diagnostic feature of cervical vertebrae.
  • Spinous process is bifid (split) in many cervical vertebrae (example: some cervical vertebrae have bifid spinous processes).
  • Transverse foramen: holes in the transverse processes; unique to cervical vertebrae.
  • Atlas specifics (C1) and orientation cues:
  • Anterior arch and anterior tubercle (anterior side)
  • Posterior arch and posterior tubercle (posterior side)
  • Lateral masses with superior articular facets that articulate with the occipital condyles
  • The occipital bone and the atlas connection:
  • The atlas articulates with the occipital bone at the superior articular facets, forming the atlanto-occipital joints that permit head nodding.

• Thoracic and lumbar vertebrae: distinguishing features

  • Thoracic vertebrae (12):
  • Body and vertebral foramen similar to other regions
  • Spinous processes are angled and project downward; described as “giraffe-like” in appearance.
  • Costal facets on the body for articulation with ribs; costal facets on the transverse processes for articulation with tubercle of ribs.
  • Ribs: there are $12$ pairs of ribs, so total ribs = $24$.
  • Lumbar vertebrae (5):
  • Larger vertebral bodies than cervical/thoracic due to load-bearing; spinous processes are more horizontal (not as angled downward as thoracic).
  • Appearance reminiscent of a moose (large body, robust processes) when viewed from the side.
  • Costal facets and rib articulation terminology:
  • Costal facets: on the vertebral bodies (head of rib articulation)
  • Transverse costal facets (on transverse processes) for tubercle articulation of ribs

• General vertebral features for orientation and articulation

  • Vertebral foramen: central opening for the spinal cord (present in all vertebrae).
  • Superior articular facets and inferior articular facets: ensure articulation between adjacent vertebrae; orientation determines which way vertebrae articulate.
  • Transverse processes: lateral projections on vertebrae; house the transverse foramina in cervical vertebrae only.
  • Spinous processes: posterior projections along the spine; orientation varies by region (cervical typically bifid, thoracic downward angulation, lumbar more horizontal).

• Practical skull exercise and study tips (lab activity overview)

  • Box with a complete skull is used for hands-on practice; students will assemble the skull with pipe cleaners to label and place foramina.
  • Focus foramina to identify on the model includes: foramen magnum, and major foramina on the sphenoid bone (rotundum, ovale, spinosum, optic canals in lesser wings, superior orbital fissure, etc.).
  • Orientation challenges: note that you may be looking from the opposite direction of the instructor; skull orientation can be tricky when rotating around.
  • Specific foramina and related structures mentioned as practice points: rotundum, ovale, spinosum (the three major foramina on the greater wing); jugular foramen; foramen lacerum; foramina associated with nasal/ethmoid/optic regions.
  • The goal of this hands-on activity is to reinforce recall through repetition and verbal labeling in class discussions, plus exam-style recall in quizzes and practicals.

• Key terms and quick references

  • Bones and landmarks:
  • Zygomatic bone
  • Maxilla
  • Nasal bones (paired)
  • Frontal bone (unpaired)
  • Ethmoid bone (unpaired)
  • Vomer bone (unpaired; sometimes informally misspelled as “bomer bone” in discussion)
  • Suture terms and orientation:
  • Coronal suture
  • Sagittal suture
  • Lamboid suture
  • Squamous suture
  • Ethmoid specifics:
  • Crista galli (superior projection; anterior face of ethmoid)
  • Cribriform plate (with olfactory foramina; olfactory nerves pass here)
  • Perpendicular plate (part of nasal septum; articulates with vomer)
  • Conchae: superior nasal concha, middle nasal concha (ethmoid); inferior nasal concha (separate bone)
  • Orbital plate (part of orbit)
  • Lateral masses (contain ethmoid sinuses)
  • Sphenoid specifics:
  • Sella turcica (hypophyseal fossa houses the pituitary gland)
  • Tuberculum sellae (anterior portion)
  • Dorsum sellae (posterior portion)
  • Lesser wings (contain optic canals)
  • Greater wings (host several foramina and fissures)
  • Optic canals (in lesser wings)
  • Superior orbital fissure; inferior orbital fissure
  • Pterygoid processes (wing-like projections)
  • Foramina and canals (common test targets):
  • Foramen magnum (occipital bone)
  • Foramen rotundum (sphenoid, greater wing)
  • Foramen ovale (sphenoid, greater wing)
  • Foramen spinosum (sphenoid, greater wing)
  • Optic canal (in lesser wing of sphenoid)
  • Superior orbital fissure and inferior orbital fissure (orbit openings)
  • Foramina along the skull base such as jugular foramen and foramen lacerum (referenced as practice items)

• Mnemonics and study aids mentioned

  • “Rigatoni over spaghetti” mnemonic to remember the order of foramina on the greater wing from top to bottom: Rotundum (top), Ovale (middle), Spinosum (bottom).
  • Prefixes and roots to decode anatomy terms (e.g., pterygoid = wing-like; crista galli meaning “rooster’s nest”).

• Summary of practical implications and study approach

  • Anatomy relies heavily on memorization; focusing on prefixes/suffixes helps decode many bone names and regions.
  • Repetition through lab exercises (lab manual and ticket-ins) reinforces recall and prepares for quizzes and practicals.
  • Understanding the function and relationships of structures (e.g., sinuses, nasal septum, orbit, and spinal segments) aids in applying knowledge to real-world anatomy and clinical scenarios.

• Clarifications and common questions addressed in class

  • The 20-point buffer is applied to quizzes to compensate for missed questions, with a maximum possible quiz score of $100$.
  • The number of paranasal sinuses is $5$, with air-filled cavities located around the nasal cavity to support nasal resonance and lightening of the skull.
  • The atlas (C1) lacks a typical vertebral body; the axis (C2) provides the dens/odontoid process that enables rotation of the head.
  • The occipital bone connects with the atlas via the superior articular facets, forming the atlanto-occipital joint that permits nodding.
  • The thoracic region has a characteristic giraffe-like spinous process, while the lumbar region has a moose-like body; this helps with rapid visual identification in models.
  • The intervertebral discs consist of a jelly-like nucleus pulposus enclosed by a fibrous annulus fibrosus; pathology includes herniation and bulging, each with distinct clinical implications.

• Final reminders for exam preparation

  • Be comfortable identifying major skull bones and landmarks on models:
  • Ethmoid bone landmarks: crista galli, cribriform plate, olfactory foramina, perpendicular plate, middle/superior nasal conchae, orbital plate, lateral masses.
  • Sphenoid bone landmarks: sella turcica (hypophyseal fossa), tuberculum sellae, dorsum sellae, optic canals, superior orbital fissure, pterygoid processes, foramen rotundum/ovale/spinosum.
  • Be able to describe and distinguish cervical, thoracic, and lumbar vertebrae by key features (foramina in transverse processes for cervical; costal facets for thoracic; larger bodies in lumbar; bifid spinous processes in many cervical vertebrae).
  • Know the counts and basic relationships of the spine sections: $7$ cervical, $12$ thoracic, $5$ lumbar, $5$ sacral (fused), and $3 ext{ to } 5$ coccygeal.
  • Practice orientation cues for the atlas and axis, and memorize the major joints: atlanto-occipital and atlantoaxial.