Axial Skeleton Concepts

Question 1

Describe how the skeleton is organized into axial and appendicular divisions, accounting for all 80 Axial bones and grouping them into categories (cranial, facial…)

Answer 1

-The skull contains 22 bones, of which 8 are cranial and 14 are facial
- 6 middle ear ossicles (3 in each ear)
- 1 hyoid bone in the neck
- 26 bones of the vertebral column
- 1 chest bone (sternum)
- 24 ribs (12 pairs)

Question 2

Compare and Contrast 5 “major” types of bones based on shape and one “minor” bone type. Know, roughly, some examples of each type of bone.

Answer 2

Major:
long= greater in length than the width (tibia, humerus)
short= cube-shaped (carpals and tarsals)
flat= thin, composed of two parallel plates of compact bone enclosing a layer of spongy bone (sternum, ribs)
irregular= complex shapes (vertebrae and some facial bones)
sesimoid= shaped like sesame seed (patella)
Minor:
Suture= small extra bone plates located within the sutures of cranial bones (coronal sutures, lambdoidal sutures)

Question 3

Roughly know which bones of the skeleton are hematopoietic

Answer 3

Bones of the axial skeleton and the proximal ends of the humerus and femur are hematopoietic

Question 4

What are the 8 cranial bones?

Answer 4

frontal (1)
parietal (2)
temporal (2)
occipital (1)
sphenoid (1)
ethmoidal (1)

Question 5

What does the frontal bone compose?

Answer 5

-forms the anterior roof, wall, and floor of the cranium
-Roof and medial walls of the orbits

Question 6

What do the parietal bones compose?

Answer 6

Forms majority of lateral walls and posterior roof cranium

Question 7

What do the temporal bones compose?

Answer 7

-Vertical part forms the inferior lateral walls and the horizontal part forms the central floor of the cranium
-Articulate with zygomatic bones

Question 8

What does the occipital bone compose?

Answer 8

-makes up the posterior part of the cranial floor
-Articulates with the first vertebra

Question 9

What does the sphenoid bone compose?

Answer 9

• Makes up a tiny part of the lateral wall, floor of the cranium, and posterior wall of the orbit, and some of the medial and lateral walls of the orbit
• Articulates with all 7 cranial bones as it sits in the center

Question 10

What does the ethmoid bone compose?

Answer 10

-A small portion of the anterior cranial floor
-Large part of the nasal cavity

Question 11

Give the role of sutures, sinuses & foramina.

Answer 11

Suture= holds bones together
sinuses= cavities within bone lined with mucous membranes and are extensions of the lining of the nasal cavity, help to clean inhaled air
formina= facial nerves and vessels

Question 12

Give the height, composition & roles of the vertebral column

Answer 12

• Encloses and protects the spinal cord, supports the head, and provides attachment points
• 60-70cm long
• 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae
• Sacrum and coccyx

Question 13

Contrast primary and secondary curves of the vertebral column

Answer 13

Primary curve= original fetal curves (thoracic and sacral)
Secondary curve= develop to support upright living (cervical and lumbar)

Question 14

Describe the unique anatomical features of the atlas and axis, focusing on the atlantooccipital and atlantoaxial articulations – the structures that make up these articulations, and the function of each articulation.

Answer 14

The atlas’ superior articular facets are concave to receive the occipital condyles to form the atlantooccipital joints. This allows your head to move up and down.

The axis has unique dens that protrude superiorly to articulate with the anterior arch of the atlas, forming the Atlanto axial joint that lets you shake your head.

Question 15

Contrast demi facets with facets and explain the role of each.

Answer 15

Facets are found on T10-T12. There’s only one facet on vertebrae and each facet articulates with one rib.

Demifacets are found on T1-T8. A demi facet is half of a facet. The inferior and superior side of a vertebra joins with another demi facet or another vertebra to articulate with one rib. The rib coming in splits its articulation with two vertebrae.

Question 16

Discuss the relationship between vertebrae and vertebral discs (which 2 vertebrae are NOT separated by a vertebral disc), and describe the structure and function of vertebral discs.

Answer 16

The vertebral discs between vertebrae are filled with a gelatinous substance, nucleus pulposus, that cushions the spinal column.C1 and C2 are not separated by a vertebral disc

Question 17

Explain how the intervertebral foramina are formed, focusing on the anatomical structures of vertebrae involved in forming these foramina.

Answer 17

Intervertebral foramina are formed from the articulation of inferior vertebrae to a superior vertebra. The superior articular facet of an inferior vertebra articulates with the inferior articular facet of a superior vertebra, forming an intervertebral foramen.

Question 18

Describe the location of the sacrum, the bones it articulates with, the bony landmarks of the sacrum, and the role of these bony landmarks.

Answer 18

The sternum is anterior to the vertebrae and ribs. They articulate with the ribs at the body and clavicle at the clavicular notch

Question 19

Describe the location of the coccyx, the bones it articulates with, the bony landmarks of the coccyx, and the role of these bony landmarks.

Answer 19

The coccyx is inferior to the sacral. Has 4 transverse processes that are attachments for muscles.

Question 20

Contrast sex-specific differences in the orientation of the coccyx relative to the birth canal

Answer 20

In females, the coccyx faces inferiorly for the birth of a child, and in males, the coccyx faces anteriorly

Question 21

Describe the role of the thoracic cage and the axial bones (and cartilages) involved

Answer 21

The thoracic cage encloses and protect the organs in the thoracic and abdominal cavities. The axial skeleton provides support and cushioning for your brain, spinal cord, and organs in your body.

Question 22

Name the 3 parts of the sternum, the bony landmarks of the sternum, and their roles

Answer 22

The three parts of the sternum are the manubrium, body, and xiphoid process. The manubrium is the point of articulation for the 1st rib. The body is the point of articulation for true ribs. The xiphoid process is a point of attachment for muscles in the body.

The sternal angle separates the manubrium from the body. At the most superior, medial edge of the manubrium is the suprasternal notch. Laterally, is the clavicular notches to receive the medial ends of the clavicles

Question 23

Separate the 12 ribs into 4 separate categories depending on how they articulate with the sternum (articulate with the manubrium, articulate directly with the body, articulate indirectly with the body of the sternum, don’t articulate at all with the sternum!).

Answer 23

1st rib: articulate with manubrium
2nd-7th rib: articulate with sternum body
8-10th rib: articulate indirectly with the body of sternum through coastal cartilage of 7th rib
11-12th rib: floating rib (don’t articulate at all)

Question 24

Identify which of the 4 categories describes true ribs, and which describes false ribs.

Answer 24

True ribs are ribs that articulate directly to the sternum. False ribs are ribs that attach indirectly to the sternum or are floating ribs.

Question 25

Be able to trace the direction of a rib from posterior articulation with thoracic vertebrae to anterior articulation with the sternum, using relevant anatomical directions.

Answer 25

Posteriorly, ribs 1-8 articulates with demi facets of vertebrates, and ribs 10-12 articulates with facets of vertebrates. Anteriorly, the first rib articulates with the manubrium of the sternum, ribs 2-7 articulates directly to the body, ribs 8-10 indirectly articulate with the body, and ribs 11-12 do not articulate at all.