BIO 004 · Human Anatomy
The Vertebral Column and Thoracic Cage
Block 2 · Module 3: Axial Skeleton, Spine
A reference for the spine video and lab. The vertebral column is the central axis of the body, and the thoracic cage is built onto it. This page covers the regions and curvatures, a typical vertebra, each region of vertebrae in detail, and the sternum and ribs.
How to use this sheet Toggle the toolbar above. Notes prints the full reference for review. Study prints as a fill-in-the-blank worksheet. Print it, then write each definition while you watch the video or read your book. Quiz me is on-screen typing practice: type the term, click Reveal to check yourself. The comparison grids respond to Study and Quiz too, with a Reveal button on each row.
The Foundations video gives you a complete foundational understanding of this topic, enough on its own for a foundational course. Learn it first, then move on to the Deep dive, which adds the majors-level material: the regional vertebrae, the atlas and axis, and the thoracic cage.
- Name the regions of the vertebral column and the number of vertebrae in each.
- Identify the normal curvatures of the spine and tell the primary from the secondary.
- Label the parts of a typical vertebra and the structure of an intervertebral disc.
- Distinguish cervical, thoracic, and lumbar vertebrae, and describe the atlas, axis, sacrum, and coccyx.
- Identify the bones and markings of the thoracic cage.
Your pre-work
Work through these the evening before class. None of it is turned in. It is how you learn the material and build your spaced recall.
This is more than a checklist. Ticking these boxes is the start, not the finish. Committing this material to memory and being able to apply it takes considerable time and repeated effort. You are not done when the boxes are checked. Put in the real hours, and keep coming back for frequent recall and review until the material is genuinely yours.
The vertebral column
Add a lateral view showing the regions and the four curvatures.
A typical vertebra
Add a superior view of a vertebra with its parts labeled.
The thoracic cage
Add an anterior view of the sternum and ribs.
The Vertebral Column, an Overview
The adult vertebral column, or spine, is 26 bones: 24 separate vertebrae in three regions, plus the sacrum and the coccyx. It is the central supporting axis of the body. Compare its five regions, superior to inferior.
| Region | Vertebrae | Description |
|---|---|---|
| Cervical region | 7, C1 to C7 | the neck |
| Thoracic region | 12, T1 to T12 | the chest, each vertebra articulates with a pair of ribs |
| Lumbar region | 5, L1 to L5 | the lower back |
| Sacrum | 5, fused | a single triangular bone wedged between the hip bones |
| Coccyx | 4, fused | the tailbone |
- Intervertebral discsfibrocartilage pads between adjacent vertebral bodies
The Curvatures
The adult spine has four front-to-back curves that act like a spring, giving the column strength, flexibility, and balance. Primary curvatures are present at birth; secondary curvatures develop with the milestones of infancy. Compare them.
| Curvature | Type | When it develops |
|---|---|---|
| Cervical curvature | secondary | develops as an infant holds up its head |
| Thoracic curvature | primary | present from birth |
| Lumbar curvature | secondary | develops as a child stands and walks |
| Sacral curvature | primary | present from birth |
A Typical Vertebra
Parts of a vertebra
- Bodythe thick, weight-bearing anterior portion, also called the centrum
- Vertebral archthe bony ring projecting from the back of the body
- Pediclesthe two short bars connecting the arch to the body
- Laminaethe two flat plates that complete the arch behind
- Vertebral foramenthe opening enclosed by the body and arch, the spinal cord runs through it
- Spinous processthe single projection pointing backward from the arch
- Transverse processesthe two projections pointing laterally from the arch
- Articular processesthe superior and inferior pairs that join one vertebra to the next
Between the vertebrae
- Vertebral canalthe stacked vertebral foramina, the channel that holds the spinal cord
- Intervertebral foraminathe gaps between stacked vertebrae where the spinal nerves exit
- Intervertebral disca fibrocartilage pad between two vertebral bodies, a shock absorber
- Anulus fibrosusthe tough outer ring of the disc
- Nucleus pulposusthe soft, gel-like core of the disc
Regional Vertebrae
Each region has a vertebra shaped for its job. Compare the three typical regions by body shape, spinous process, and distinctive feature, then study the specialized cervical vertebrae below.
| Region | Body | Spinous process | Distinctive feature |
|---|---|---|---|
| Cervical, C1 to C7 | small and oval, the smallest vertebrae | short, often bifid, or forked | transverse foramina in the transverse processes, which pass the vertebral arteries |
| Thoracic, T1 to T12 | heart-shaped | long, angled sharply downward | costal facets on the body and transverse processes where the ribs articulate |
| Lumbar, L1 to L5 | thick and kidney-shaped, the largest vertebrae | short and blunt | massive build for weight bearing, no costal facets and no transverse foramina |
The specialized cervical vertebrae
- Atlas (C1)a ring with no body and no spinous process, it holds up the skull
- Atlanto-occipital jointwhere the atlas meets the occipital condyles, the joint for the "yes" nod
- Axis (C2)bears the dens, an upward bony peg
- Densthe odontoid process, the peg of the axis that the atlas pivots around for the "no" rotation
- Vertebra prominens (C7)a long spinous process you can feel at the base of the neck
Sacrum
- Sacrumfive fused vertebrae forming a triangular bone wedged between the hip bones
- Sacral promontorythe anterior ridge of the first sacral vertebra
- Median sacral crestthe fused spinous processes along the posterior surface
- Sacral foraminathe openings that pass the sacral nerves
- Sacral canalthe continuation of the vertebral canal through the sacrum
- Sacral hiatusthe opening at the inferior end of the sacral canal
- Auricular surfacethe ear-shaped surface that joins the hip bone at the sacroiliac joint
Coccyx
- Coccyxthe fused tailbone, an attachment point for pelvic ligaments and muscles
The Thoracic Cage
The thoracic cage is the sternum in front, the ribs on the sides, and the thoracic vertebrae behind. It shields the heart and lungs.
The sternum
- Sternumthe breastbone, a flat bone of three fused parts
- Manubriumthe superior part, articulates with the clavicles and the first ribs
- Bodythe long middle part of the sternum
- Xiphoid processthe small inferior tip, a muscle attachment, cartilage that ossifies with age
- Jugular notchthe central dip at the top of the manubrium, easily felt
- Sternal anglethe ridge where the manubrium meets the body, a landmark level with the second rib
The ribs
- Ribstwelve pairs of flat, curved bones forming the walls of the cage
- Headthe posterior end of a rib, articulates with the vertebral bodies
- Tuberclethe knob near the head, articulates with a transverse process
- Costal cartilagethe hyaline cartilage that connects a rib toward the sternum
The twelve rib pairs are classified by how they reach the sternum. Compare the three groups.
| Rib group | Pairs | Anterior attachment |
|---|---|---|
| True ribs | 1 to 7 | attach to the sternum directly, each by its own costal cartilage |
| False ribs | 8 to 12 | do not reach the sternum directly; pairs 8 to 10 join the costal cartilage of the rib above |
| Floating ribs | 11 and 12 | no anterior attachment at all; a subset of the false ribs |
See also: The Skull, the other region of the axial skeleton, and Bone Histology for the bone tissue.
Study questions
Work on answering these in writing, in your own words. They are the questions to bring to class, and good practice for the reasoning the exams ask for.
- Name the five regions of the vertebral column and how many vertebrae are in each.
- Compare a cervical, a thoracic, and a lumbar vertebra by one feature that identifies each.
- Name the four spinal curvatures and state which are primary and which are secondary.
- Explain how the ribs attach anteriorly, and how that distinguishes true, false, and floating ribs.
Step 2 . Retrieval check
Now explain it back, in your own words.
In 60 words or more, pull together what the video just taught you. Include the key concepts. This is the point where the learning actually sticks. After you submit, your spaced-recall cards for this topic unlock.