2.4 Remainder of the Axial Skeleton

Question 1

Vertebral Column

Answer 1

The s-shape bony structure that runs down the middle of the back

*aka the spine

consists a total of 32-34 vertebrae, which can be unfused vertebrae (singular: vertebra) & fused vertebrae

Question 2

intervertebral foramina

Answer 2

spaces between the vertebrae

Question 3

4 curvatures within the vertebral column

Answer 3

• 2 concave (curved inward or caved in) cervical & lumbar curvatures
• The cervical & lumbar curvatures are particularly important to our ability to walk upright
• 2 convex (curved outward) thoracic & sacral curvatures
• Are called primary curvatures since they exist from birth

Question 4

unfused vertebrae (singular)

Answer 4

24 unfused vertebrae consists of 7 cervical, 12 thoracic, & 5 lumbar vertebrae

remember this as “breakfast at 7am, lunch at 12pm, dinner at 5pm”

Question 5

fused vertebrae

Answer 5

8-10 fused vertebrae consists of the 5 sacral & 3-5 coccyx vertebrae.

Question 6

9 common features of a typical vertebra

Answer 6

1. A pointy posterior spinous process (the pointy part that sticks out from the back of each vertebra)
2. Two flat transverse processes on the sides (the two flat, wing-like projections that stick out to the sides of each vertebra)
3. A central hole called the vertebral foramen, where the spinal cord passes through.
4. A big anterior vertebral body (the large, thick, round part at the front of each vertebra)
5. Two short, pillar-like pedicles connecting the body to the side processes
6. Two flat, plate-like laminae (single: lamina) that connect the sides to the back process
7. Two superior articular processes with facets that articulate with the vertebra above.
   - These are round projections (process) containing a joint (facets) located superiorly on the laminae.
   - These superior & inferior processes restrict twisting of the vertebral column, to prevent damage to the spinal cord
8. Two inferior articular processes with facets that articulate with the vertebra below.
   - These are round projections (process) containing a joint (facets) located inferiorly on the laminae or spinous process
9. Between each vertebra, there’s a soft, cushiony pad called an intervertebral disc. This disc helps absorb shock when you move, so your spine doesn’t get damaged. If the disc ruptures, it’s called a herniated disc, and it can be very painful.

Question 7

7 Cervical Vertebrae (C1-C7)

Answer 7

• They have small holes in the side parts of the vertebrae (called transverse foramina) that allow blood vessels, like the vertebral artery and vein, to pass through.
• The spinous processes (the pointy parts at the back) are often split or bifid in these vertebrae.
• The vertebral bodies (the thick parts in front) are smaller compared to other vertebrae.

• The first two cervical vertebrae, C1 (called the atlas) and C2 (called the axis), are special because they allow the head to move up and down (like nodding) and side to side (like shaking your head).

Question 8

Atlas Vertebra (C1)

Answer 8

• the first cervical vertebra &
  has round structures called lateral masses which contains a layer of superior articular facets on its surface. These facets articulates with the occipital condyles, forming the atlanto-occipital joint, which enables the nodding motion of the head.

• Instead of a typical vertebral body, it has an anterior tubercle.
• It doesn’t have a spinous process; instead, it has a posterior tubercle.
• Instead of regular pedicles, it has anterior arches, and instead of laminae, it has posterior arches.
• It has a very large vertebral foramen (the hole where the spinal cord passes through).

Question 9

Axis Vertebra (C2)

Answer 9

• the second cervical vertebra
• uniquely identified by a superior round projection (round or knob-like bump that sticks up from the top (superior) part of a bone.) on its vertebral body called the dens (aka odontoid process).
• The dens fits inside & articulates with the atlas’ anterior tubercle to form the atlantoaxial joint, which allows rotation of the head

Question 10

12 Thoracic Vertebrae (T1-T12)

Answer 10

• located in the posterior chest region & each single vertebrae articulates with a pair of ribs
• Spinous processes are thin and point downward (inferiorly).
• They don’t have transverse foramina (holes in the side like in cervical vertebrae).
• They have costal facets that connect to the ribs:
• Superior & inferior costal facets connect to the heads of the ribs.
• Transverse costal facets on the side parts (transverse processes) connect to the rib tubercles.
• The vertebral body is roughly triangular or heart-shaped. It’s bigger than the cervical vertebrae but smaller than the lumbar vertebrae.

If you look at a thoracic vertebra from the side, it kind of looks like a giraffe.

Question 11

5 Lumbar Vertebrae (L1-L5)

Answer 11

• located in the lower back

a. All have a large block-like vertebral body
b. The spinous processes are thick, blocky, squarish & point posteriorly
c. They lack transverse foramina & costal facets
d. If you look at a lumbar vertebra from the posterolateral side, it looks like a moose.

Question 12

Sacrum Vertebrae (S1-S5)

Answer 12

• On the top surface, we find the sacral promontory, which is the part of the first sacral body that projects anteriorly (forward) into the pelvic cavity (the space inside the pelvis, located below the abdomen) & articulates with the L5 vertebra, forming the lumbosacral joint.
• On the side of the sacral promontory are the alae (plural) or wings, which are smooth, wing-shaped areas.
• Just behind the sacral promontory is the sacral canal, where the nerve roots from the lower spine pass through.
• On the back of the sacrum, you can see the fused spinous processes as the median sacral crest.
• Spinal nerves pass through openings called the anterior and posterior sacral foramina on both sides of the sacrum.
• On the sides of the sacrum are the auricular surfaces, which connect with the hip bones to form the sacroiliac joints.

• consists of five vertebrae that are fused together to form one solid bone.

Question 13

The Coccyx Vertebrae (Co1-Co5)

Answer 13

• made up of 3-5 small, fused vertebrae that articulate superiorly with the sacrum vertebrae. (the top of the coccyx connects to the bottom of the sacrum)
• provides an attachment point to the the many muscles & ligaments of the pelvic floor

• also known as the tailbone

Question 14

Sternum Bone

Answer 14

• sternum is the central bone of the chest, and it has three parts: the manubrium (top part, shaped like a necktie knot), the gladiolus (the long middle section), and the xiphoid process (the small, pointed bottom part)
• During CPR, chest compressions are performed on the gladiolus, and care must be taken not to break the xiphoid process, as its sharp end can cause damage to internal organs like the liver, leading to internal bleeding.

Question 15

Rib Bones

Answer 15

• The 12 pairs of ribs (not just 12 ribs) form a protective cage around the thoracic cavity and its vital organs.
• The spaces between the ribs are called intercostal spaces and these spaces contain muscles, blood vessels, nerves, and lymphatic vessels.
• The ribs connect to the sternum at the front via costal cartilage. Ribs are classified based on how their costal cartilage connects to the sternum

Question 16

Ribs 1–7 (7 pairs)

Answer 16

• are called true ribs or vertebrosternal ribs because they directly attach to the sternum using their own costal cartilage.
• vetebro - referring to the vertebra & sternal- referring to the sternum bone.
• indicating their connection to both the spine and sternum.

Question 17

Ribs 8–12 (ribs 8, 9, 10, 11, & 12 = 5 pairs)

Answer 17

• called false ribs because they don’t directly attach to the sternum.
• Ribs 8–10 (3 pairs) connect to the sternum indirectly, using the cartilage of the true ribs, and are called vertebrochondral ribs (with “chondral” meaning cartilage).
• Ribs 11–12 (2 pairs) don’t attach to the sternum at all and are known as floating ribs or vertebral ribs.

costal margin refers to the medial border (inner edge) of the cartilage of the false ribs.

Question 18

rib’s superior & inferior facets

Answer 18

• The rib has superior and inferior facets on its posterior head
• These facets help the rib connect to two vertebrae: the superior facet of the rib connects with the inferior costal facet of the vertebra above, and the inferior facet of the rib connects with the superior costal facet of the vertebra below.
• Lateral to the head we find the neck, which contains a tubercle that articulates with a vertebra’s transverse processes with costal facets.
• The rib curves around anteriorly at its angle, after which the main anterior portion becomes known as the shaft. On the shaft’s interior surface is the costal groove, which is where blood vessels and nerves travel.

Question 19

Hyoid Bone

Answer 19

• U-shaped bone located in the upper neck, and it is sometimes classified as part of the skull.
• doesn’t connect to any other bone, making it a floating or suspended bone.
• It’s held in place by muscles and ligaments and plays a key role in supporting the larynx (voice box), as well as providing attachment for the tongue muscles & aids in swallowing.