Anatomy Lab Notes: Skull, Vertebrae, Os Coxa, Pelvis, and Ribs

Skull and Skull Features

• The mandible is the only skull bone that can be removed to test individually; all other skull bones are fused together in the intact skull.
• You can view the skull from multiple angles: frontal (front), lateral (side), posterior (back), superior (top), and inferior (bottom) after flipping. The base of the skull (when the cranial cap is removed) reveals many internal structures.
• In your atlas, the Skull pictures are around page 24–28; use the atlas to orient views.
• Pointers: when you identify a hole on one side, you can project a line through to locate the corresponding hole on the opposite side. This helps verify the same for different views.
• If the atlas checklist doesn’t include everything, consult the textbook. If still unclear, use Google Image Search to find the specific hole/feature.
• Dr. Hinton has set up a skull quiz in the course (D2L) for self-testing; you can see what you got right or wrong.
• Skull is one of the more complex structures since most bones are fused; don’t delay reviewing it.
• Plan: today focus on bones; Monday will cover articulations (shoulder, elbow, knee, ankle) and hands-on practice; Wednesday will have articulations out again; microscope work and phone-related activities are the last lab before the exam on Friday.

Vertebral Column Overview

• The vertebral column consists of three regions with different numbers of vertebrae:
  • Cervical: $7$ vertebrae
  • Thoracic: $12$ vertebrae
  • Lumbar: $5$ vertebrae
• Special cervical units:
  • Atlas (C1) and Axis (C2) are two cervical vertebrae with unique features.
• Common checklist terms on every vertebra (found on the checklist): vertebral foramen, spinous process, transverse process, pedicle, lamina, vertebral notches, articular facets.

Cervical Vertebrae: Atlas (C1) and Axis (C2)

• All cervical vertebrae have transverse foramina (holes on the sides) in addition to the vertebral foramen.
• Atlas (C1):
  • No body; the opening in the middle is enlarged because it supports the skull.
  • Supports the base of the skull and allows the head to nod.
• Axis (C2):
  • Has a dens (odontoid process) that projects upward; the dens fits into the large space of C1.
  • The dens creates a joint that allows pivotal movement of the head.
• The atlas and axis fit together with the dens forming a peg-like articulation; the space on C1 accommodates the dens.
• Transverse foramina serve as passageways for vertebral arteries up to the head.

Thoracic Vertebrae and Costal Facets

• Thoracic vertebrae have features that support the rib cage, notably costal facets.
• Costal facets occur in three sets:
  • On the body of the vertebra (superior and inferior costal facets) to articulate with heads of ribs.
  • On the transverse process (transverse costal facets) to articulate with the tubercles of ribs.
• Quick visualization cue (90% rule): when you look at the spinous process and body alignment, a thoracic vertebra often resembles a giraffe (long nose/ears) with antlers; this heuristic helps identify thoracic vertebrae quickly, though it’s not perfect.

Lumbar Vertebrae

• Lumbar region contains $5$ vertebrae.
• Key distinguishing features: absence of transverse foramina and costal facets.
• Quick-immersion heuristic (moose): if the front and side views resemble a moose’s face, you’re likely looking at a lumbar vertebra.
• The transition zone between thoracic and lumbar can present a tricky moose-giraffe hybrid appearance; when in doubt, check for the absence of costal facets.

Os Coxae (Hip Bone) and Pelvis Anatomy

• The pelvis consists of two ossa coxae (hip bones) and a sacrum at the back.
• Important landmarks and concepts:
  • Obturator foramen (large opening on the pelvis).
  • Greater sciatic notch (large curved notch on the posterior aspect).
  • A rough area on the bone (back side) near the greater sciatic notch that is used as a landmark for various attachments.
• The “telephone receiver” analogy (handy for memory): pretend the os coxae is a telephone handset. The obturator foramen is the mouth of the receiver, and the greater sciatic notch is the ear hold. If you place your ear against the rough area and your mouth toward the obturator foramen, you’re using the same side of the bone to identify its orientation.
• The rough area on the bone is important for orientation; the smooth/curved portions are not the focus here.
• Left vs. right orientation: this is the tricky part when you’re given a single pelvis bone on the table; practice with both sides to learn the orientation.
• Pelvis components: two ossa coxae + sacrum.

Male vs Female Pelvis: Sex Determination

• The easiest distinguishing feature is the pubic arch (pubic angle) at the front where the hips meet.
• Gender indicators based on the pubic arch angle:
  • Female pelvis: pubic arch angle is greater than $90^ ext{o}$ (wider open).
  • Male pelvis: pubic arch angle is 60 or less (narrower).
• Additional distinguishing features (not exhaustively listed here) can also include overall pelvic brim shape and subpubic angle, but the primary quick method is the pubic arch angle > or ≤ $90^ ext{o}$.

Hands and Feet: Anatomical Position and Left/Right Identification

• Feet are shown in a standing position (anatomical position) and not upside down.
• Hands are shown in anatomical position, with the palm facing toward you.
• Right vs Left orientation should be derivable on the feet and hands; this may be indicated on the checklist.
• Some atlas pictures may show non-anatomical positions; do not rely on those for orientation.

Ribs: Structure and Classification

• Each rib has key parts to identify: head, tubercle, angle, and the costal groove.
• Rib classification in relation to the sternum:
  • True ribs: $1 ext{ through } 7$; connect directly to the sternum via single costal cartilage.
  • False ribs: $8 ext{ through } 10$; connect to the sternum indirectly via cartilage that connects to cartilage that connects to the sternum.
  • Floating ribs: $11 ext{ and } 12$; do not connect to the sternum at all (also considered false).
• For true ribs, the cartilage attaches directly to the sternum; for false ribs, the connection is indirect; for floating ribs, there is no anterior connection to the sternum.
• When using articulated skeletons, you can demonstrate right and left orientations and the rib classifications more easily.
• Use the articulated bones as a visual aid to practice identifying parts and determining left vs right.

Study Resources and Practice Opportunities

• D2L links provide external 3D images of bones with labels (great for dimensional understanding). If you enjoy interactive 3D resources, these links are useful.
• In-class practice emphasizes handling real bones for three-dimensional understanding rather than relying solely on pictures.
• A skull quiz is available (Doctor Hinton) for self-assessment; use it to gauge what you know and what you need to review.
• There is a built-in plan for the week: full-bone study today; articulations Monday and Wednesday; last day of in-room questions with microscope and phones before the exam Friday.

Practical Tips for Lab Prep and Exam Readiness

• Always try to identify big-picture features first (region, major landmarks) before focusing on small details.
• For the skull, use multiple views and the hole-pointers strategy to match features across sides.
• For vertebrae, memorize region-specific features (e.g., transverse foramina in cervical, costal facets in thoracic) to quickly classify vertebrae.
• For the os coxae, practice determining left vs right by examining the orientation of landmarks like the greater sciatic notch and obturator foramen, using the “telephone receiver” analogy as a memory aid.
• For the pelvis, use the pubic arch angle to distinguish sex quickly in a visual assessment.
• When uncertain, use a three-step check: identify the region, verify key landmarks, and cross-check with left/right orientation and neighboring bones.

Quick Reference: Key Terms to Remember

• Vertebral features: vertebral foramen, pedicle, lamina, spinous process, transverse process, vertebral notches, articular facets.
• Cervical special features: transverse foramina; atlas (C1) has no body; axis (C2) has the dens (odontoid process).
• Thoracic features: costal facets (on the body superior/inferior; on the transverse process); giraffe-like appearance heuristic.
• Lumbar features: absence of transverse foramina and costal facets; moose analogy for quick identification.
• Os coxae features: obturator foramen, greater sciatic notch, rough posterior area; orientation and left/right differentiation.
• Pelvis sex-determining trait: pubic arch angle > $90^ ext{o}$ in females; ≤ $90^ ext{o}$ in males.
• Rib anatomy: head, tubercle, angle, costal groove; true ribs ($1-7$) direct to sternum; false ribs ($8-10$) indirect to sternum; floating ribs ($11-12$) do not connect to sternum.