Axial Skeleton: Skull, Vertebral Column, and Thoracic Cage Study Guide

Axial Skeleton Overview

Introduction

The axial skeleton forms the central axis of the human body and consists of the skull, vertebral column, and thoracic cage. These structures protect vital organs and provide support for the body. Understanding the bones and their specific features is essential for students of anatomy and physiology.

Skull Anatomy

Overview of the Skull

The skull is a complex structure composed of multiple bones that protect the brain and form the structure of the face. It is studied in various forms: disarticulated skull and bones, articulated skeleton, complete skulls, and median sectioned skulls.

• Frontal bone: Forms the forehead and part of the eye socket.

• Parietal bone: Paired bones forming the sides and roof of the cranium.

• Temporal bone: Houses structures of the ear and forms part of the skull base.

• Occipital bone: Forms the back and base of the skull.

• Sphenoid bone: Contributes to the floor of the cranium and orbits.

• Ethmoid bone: Forms part of the nasal cavity and orbits.

• Mandible: The lower jawbone, the only movable bone of the skull.

• Maxilla: Forms the upper jaw and part of the orbits.

• Lacrimal, nasal, palatine, zygomatic, vomer: Small bones contributing to the structure of the face and nasal cavity.

Additional info: The skull also contains various foramina (openings) for nerves and blood vessels, and processes (projections) for muscle attachment.

Major Sutures of the Skull

• Coronal suture: Between frontal and parietal bones.

• Sagittal suture: Between the two parietal bones.

• Lambdoid suture: Between parietal and occipital bones.

• Squamous suture: Between parietal and temporal bones.

Key Skull Features and Openings

• External acoustic (auditory) meatus: Canal leading to the middle ear.

• Foramen magnum: Large opening for the spinal cord.

• Occipital condyles: Articulate with the first cervical vertebra.

• Styloid and mastoid processes: Projections for muscle attachment.

• Supraorbital foramen: Opening above the eye socket for nerves and vessels.

• Cribriform plate: Part of the ethmoid bone, allows passage of olfactory nerves.

• Mandibular condyle and coronoid process: Articulate with the temporal bone and provide muscle attachment.

Skull Table: Bones and Features in Different Models

The following table summarizes which bones and features are visible in different types of skull models.

Bone/Feature	Disarticulated Skull & Bones	Articulated Skeleton	Complete Skulls	Median Sectioned Skull
Frontal bone	x	x	x	x
Parietal bone	x	x	x	x
Temporal bone	x	x	x	x
Occipital bone	x	x	x	x
Sphenoid bone	x	x	x	x
Ethmoid bone	x	x	x	x
Mandible	x	x	x
Maxilla	x	x	x	x
Lacrimal bone	x	x	x	x
Nasal bone	x	x	x	x
Palatine bone	x	x	x	x
Zygomatic bone	x	x	x	x
Vomer	x	x	x	x

Additional info: 'x' indicates the feature is present in the model.

Vertebral Column Anatomy

Overview of the Vertebral Column

The vertebral column, or spine, is composed of individual vertebrae and intervertebral discs. It supports the body, protects the spinal cord, and allows movement. The vertebral column is divided into cervical, thoracic, lumbar, sacral, and coccygeal regions.

• Cervical vertebrae (C1-C7): Support the head and allow neck movement.

• Thoracic vertebrae (T1-T12): Articulate with the ribs.

• Lumbar vertebrae (L1-L5): Support the lower back.

• Sacrum: Five fused vertebrae forming the back of the pelvis.

• Coccyx: Four fused vertebrae forming the tailbone.

Key Features of Vertebrae

• Body (Centrum): Main weight-bearing part.

• Vertebral arch: Encloses the spinal cord.

• Spinous process: Posterior projection for muscle attachment.

• Transverse process: Lateral projections for muscle and rib attachment.

• Vertebral foramen: Opening for the spinal cord.

• Superior and inferior articular processes: Form joints between vertebrae.

• Intervertebral foramen: Openings for spinal nerves.

Vertebral Column Table: Features in Different Models

Feature	Articulated Skeleton	Disarticulated Skeleton	Typical Vertebrae Model	Disc Model
Cervical curvature	x		x
Thoracic curvature	x		x
Lumbar curvature	x		x
Body of vertebra	x	x	x	x
Spinous process	x	x	x	x
Transverse process	x	x	x	x
Vertebral foramen	x	x	x	x
Intervertebral foramen				x

Thoracic Cage Anatomy

Overview of the Thoracic Cage

The thoracic cage protects the heart and lungs and supports the upper body. It consists of the sternum, ribs, and thoracic vertebrae.

• Sternum: Flat bone at the center of the chest, composed of the manubrium, body, and xiphoid process.

• Ribs: Twelve pairs of curved bones attached to the thoracic vertebrae.

• Costal cartilage: Connects ribs to the sternum.

Thoracic Cage Table: Features in Different Models

Feature	Articulated Skeleton	Disarticulated Skeleton
Sternum	x	x
Manubrium	x	x
Body of sternum	x	x
Xiphoid process	x	x
Ribs	x	x (Ribs vs. L1)
Head of rib	x	x
Angle of rib	x	x
Costal groove	x	x

Lab Exam Preparation: Key Terms and Questions

Common Lab Exam Questions

• Identify the specific bone or part of the bone labeled on a model or figure.

• Distinguish between right and left bones (e.g., right rib vs. left rib).

• Identify specific openings, curvatures, and structures (e.g., foramen magnum, vertebral foramen).

• Recognize features such as sutures, processes, and foramina.

Sample Lab Exam Table: Main Parts and Possible Answers

Main Part of Question	Possible Answers
Right or Left	right rib, left rib
Specific bone(s)	frontal bone, mandible, maxilla, nasal bone, zygomatic bone, sphenoid, ethmoid, lacrimal bone, palatine bone, vomer, inferior nasal concha, hyoid bone, cervical vertebra, atlas, axis, thoracic vertebra, lumbar vertebra, sacrum, coccyx, sternum, rib, auditory ossicles
Specific curvature	cervical curvature, thoracic curvature, lumbar curvature, sacral curvature
Specific opening	external auditory meatus, foramen magnum, optic foramen, superior orbital fissure, inferior orbital fissure, mental foramen, supraorbital foramen, transverse foramen, vertebral foramen, sacral canal, sacral hiatus, sacral foramina, intervertebral foramen
Specific part of the bone	zygomatic process of temporal bone, mandibular fossa, mastoid process, styloid process, occipital condyle, external occipital protuberance, greater wings, lesser wings, crista galli, cribriform plate, perpendicular plate, lateral masses, middle cranial fossa, posterior cranial fossa, condylar process, coronoid process, ramus of mandible, body of mandible, angle of mandible, palatine process, horizontal plate, temporal process, nasal septum, zygomatic arch, hyoid bone, costal groove, head of rib, neck of rib, tubercle of rib, angle of rib, shaft of rib
Specific structure	sagittal suture, coronal suture, squamous suture, lambdoid suture

Example Lab Questions

• Identify the specific part of the bone that is labeled #2.

• Identify the specific vertebral curvature that is labeled #4.

• Identify the specific bone that is labeled #6. Be specific!

• Identify the specific structure that is labeled #8.

• Identify the specific part of the bone that is labeled #22. If you do not know the specific part, identify the bone for half credit.

• Right or Left? Name bone #24 too.

• Identify the specific part of the bone and name the bone that is labeled #43.

Summary and Study Tips

• Review all bones, features, and structures listed in the tables above.

• Practice identifying bones and features on models and diagrams.

• Use the tables to quiz yourself and prepare for lab exams.

• Focus on understanding the function and location of each bone and feature.

Additional info: For more detailed descriptions, refer to the laboratory manual pages listed in the notes. The study guide covers the essential bones and features of the axial skeleton for Anatomy & Physiology students.