Mdolue 26 - Axial Skeleton (Vertebrae & Ribs)

Name the 5 functions of the vertebral column

1. Supports weight of head and trunk

2. Protects the spinal cord

3. Allows spinal nerves to exit the spinal cord

4. Provides site for muscle attachment

5. Movement of head and trunk

How many vertebrae in the vertebral column?

26

Name the types of vertebrae + their number of vertebrae

- Cervical: 7

- Thoracic: 12

- Lumbar: 5

- Sacral: 1 (but 5 fused)

- Coccygeal: 1 (but 4 fused)

How many curves in the vertebral column + types

4 curves: 2 concave, 2 convexe

- Convexe curves: cervical & lumbar vertebrae

- Concave: thoracic & sacral vertebrae

Body of vertebrae (orientation and features)

- Faces the anterior side

- Largest part of the vertebrae

Spinous process

- Posterior side

- Sticks out

How many arches in the vertebral arch?

2: lamina & pedicle

Lamina

- concave arch on posterior end, close to spinous process

Pedicle

bone from spinous process to the back side of the body

What does the pedicle + lamina form?

Vertebral foramen

When vertebrae are stacked, it forms the...

Vertebral canal

Transverse process

Large lateral bony projection

Articular process

Forms joints w/another bone

- "body" of superior articular facet

- Lateral bony projections but sticks out upwards

Superior articular facet

flattened curved region on top of articular facet

Using the articular processes, what happens when vertebrae is stacked?

Inferior processes come in contact w/superior processes of vertebrae

How many structures doe a vertebra have?

1 body + 7 processes ( 1 spinous, 2 transverse. 2 superior articular, 2 inferior articular)

What do thoracic vertebrae articulate with and how?

- Ribs

- By the superior demifacets to fit the rib head

What rib structure forms the joint w/the vertebrae?

Tubercle

What is unique about C1 (atlas)

- No body or spinous process

- Large vertebral foramen (aligns with foramen magnum → spine to brainstem connection)

- Has small holes for blood vessel passage

- Articulates with occipital condyles → "yes" motion

- Has facet for dens of C2

What is unique about C2?

- Has Dens (odontoid process) that acts as a pivot for C1 -> Allows "no" head rotation

- Held against C1 by a posterior ligament

- Small body and spinous process

- Smaller vertebral foramen

- Has flat superior and inferior facetse > side-to-side rotation

How are C3-C6 characterized?

- Small bodies

- Bifid spinous processes (muscle attachment)

- Transverse foramina for blood vessels

- Flat articular facets → high mobility, less stability

Why is C7 called vertebra prominens?

- Long, non-bifid spinous process

- Easily palpable at base of neck

What are the key features of thoracic vertebrae?

- Medium-sized, heart-shaped bodies

- Long spinous processes that point downward

- Oblique articular processes to lock vertebrae together

(stability > mobility)

Why do thoracic vertebrae have oblique articular processes?

To limit motion (bc it kinda locks them)

- Makes it more stable than cervical vertebrae

How do thoracic vertebrae articulate with ribs?

- Demifacets on vertebral bodies for rib heads (shared by 2 vertebrae)

- Transverse facet for rib tubercle

What distinguishes lumbar vertebrae from other regions?

Largest vertebral bodies → weight-bearing

What structural features make lumbar vertebrae stable?

- Short, thick, rectangular spinous processes

- Superior facets face medially, inferior facets laterally

- Facets interlock tightly, limiting movement

Why is the vertebral foramina of the lumbar vertebrae smaller?

Bc it has the cauda equina

What is the sacrum and when does it fuse?

- fusion of 5 sacral vertebrae

- begins ~16-18 years, completed by ~30 years

What unique structures are associated with the sacrum?

- Contains the sacral canal (continuation of vertebral canal)

- Superior articular facets articulate with the last lumbar vertebra

What features are found on the posterior sacrum?

- Median sacral crest = fused spinous processes

- Posterior sacral foramina = exit site for spinal nerves

What is the sacral hiatus and why is it important?

- Opening due to missing 5th spinous process

- Allows sacral spinal nerves to exit toward the coccyx

What is the coccyx and when does it fuse?

- Fusion of 4-5 small bones

- Completed around 20-30 years

What attaches to the coccyx?

Filum terminale (pia mater extension anchoring the spinal cord)

What are intervertebral disks and where are they found?

- Pads of fibrocartilage (strongest cartilage)

- Located between vertebral bodies

Function of intervertebral disks

- Provide support

- Absorb vertical shock + compressive force

- Movement (bending and twisting)

What are the 2 parts of the intervertebral disks?

1. Annulus fibrosus

2. Nucleus pulposus

What is the annulus fibrosus?

- Tough outer ring of fibrocartilage (for strength and containment of the disc)

What is the nucleus pulposus ?

- Soft, gelatinous inner core (for better shock absorption + resilience)

What occurs during a herniated disk?

- Tear in annulus fibrosus

- Nucleus pulposus oozes out towards intervertebral foramen

- Substance compresses spinal nerve route

- Lead to pain, tingling or loss of function

What is the healing process of a herniated disk?

- Getting rid of pressure on the annulus fibrosus (stops the nucleus pulposus from oozing)

- Healing is slow because discs are avascular and lack perichondrium

Function of thoracic cage

Protects heart and lungs (vital organs)

What are the bones like in the thoracic cage?

Semi rigid

- Bones are movable + flexible

Why is it important that the bones of the thoracic cage are flexible?

- To accomodate inflation + deflation of lung

- Assists in breathing by moving with lung expansion

What composes the thoracic cage (3)?

1. Thoracic vertebrae

2. Ribs + costal cartilages

3. Sternum

How many pairs of ribs and the types?

- 12 pairs of ribs

- 7 true ribs

- 5 false ribs

What are true ribs?

AKA: vertebrosternal ribs

- Pair 1-7

- Directly attaches to the sternum via costal cartilage

What are false ribs?

- Pair 8-10 (3): vertebrochondral ribs > attaches indirectly to sternum by connecting to the cartilage of rib 7

- Pair 11-12 (2): Floating ribs (vertebral) > no connection to sternum, only connects to vertebral column

What are the 3 parts of the sternum (breastbone) + Functions

1. Manubrium: articulates with clavicle and 1st pair of ribs

2. Body: main portion

3. Xiphoid process: small inferior tip

When does the xiphoid process ossify and what is it made of?

- Around age 40

- Made up of hyaline cartilage

What are the 2 parts of the manubrium and their functions?

1. Jugular/suprasternal notch: depressio between clavicles

2. Sternal angle: joint between manubrium + body

What role does the cartilage play in the true ribs?

Flexibility (of lungs)

What do the floating ribs protect

Kidneys (on the side of your body)

Why is the sternum split during heart surgery (midline sternotomy) instead of the cartilage?

- For access

- Bone heals faster than cartilage

- Avoids multiple rib repairs

Why don't surgeons cut through costal cartilage in surgery?

- Cartilage heals poorly compared to bone