The Axial Skeleton Flashcards
What are the functions of the axial skeleton?
- Provides protection for spinal cord and nerve roots
- Strong but flexible support for the trunk
- Posture and support of body weight
What are the structures of the axial skeleton?
33 vertebrae (# in fetus)- drops to 24 as you age
- 7 cervical; A characteristic of all animals
- 12 thoracic
- 5 lumbar
- 5 sacral; fuse together to form the sacrum
- 4 coccygeal; fuse together to form coccyx
(Side note: There can be variations among the # of vertebrae a person has typically in T, L, or S)
What are the characteristics of a typical vertebra?
- Body- found anteriorly: supports weight- gets bigger as you move inferiorly
- Vertebral/neural arch: Found posteriorly; helps protect tissue from injury
a. Pedicle (Pedicles)- attach to body
b. Lamina (laminae)- attach to pedicle - Vertebral foreman: hole where the spinal cords pass through- line up to create vertebral canal
- Spinous process: Projects posteriorly and sometimes inferiorly; where muscles + ligaments attach
5 +6. Superior articular process with articular facet (2) + Inferior articular process with articular process (2): Smooth surfaces where joints between vertebra form- The direction/orientation of a facet determines the movement within a region
- Transverse attachment (2): Posterior and lateral; allow for attachment from deep back muscles
What kind of joint is between the body of vertebra?
A symphysis joint; fibrocartilage
How many times do vertebra articulate with one another?
In most cases each vertebra articulate w/ one another 3 times
- > Joint between bodies
- > Articular process with facets (2)
What do the notch in pedicles create?
Notches in pedicles create a foreman around the lateral walls of vertebra known as the intervertebral foreman ; where spinal cords pass through
How do superior and inferior articular processes articulate?
An inferior articular process articulates with the superior articular process above it
What does the spinal cord pass through?
The vertebral canal
Intervertebral Disc
Function- connects the body of vertebra, acts as shock absorber
Composition:
- Outer portion; Anulus fibrosus (fibrocartilage); weakest posterior and laterally
- Center; Nucleus pulpous (jelly like substance); when this leaks through this is what we call a herniated disc
Most superior intervertebral disc: C2- C3
Most inferior functional disc: Between L5 and S1
Cervical Vertebrae
Most superior; 7 vertebra, the boney skeleton of the neck, smallest moveable vertebra
Specializations ->
- Hole in transverse processes; create transverse foramen- where vertebral arteries pass though (they pass through superiorly to go through the base of the skull to serve the brain)
- Spinous process split into two- Y shape; bifid spinous process
C1
Name- The Atlas; in greek mythology atlas held the earth- supports skull
Function: Ring shape supports the skull; occipital condyles of skull articulate with c1 superior articular facets
Anterior + posterior arch
NO BODY
NO SPIONUS PROCESS
C2
Name- The Axis
Dens
strongest cervical vertebra
C1 rotates on C2- Allows for head movement no
Has a body and spinous process
Atlantoaxial Joint
C1 rotates on C2- Allows for head movement no
Dens of axis goes into C1; held by the transverse ligament
Is a pivot joint- Projection of one bone sitting in another bone/ligament
Thoracic Vertebrae
Bodies have a heart shape + Look like a giraffe hehe
Specializations-
- Have costal facets; articulate with the ribs (Tubercle of rib w/ the transverse process, head of rib with the vertebral body)
- Long and slender spinous processes (point inferiorly)
Synovial joints between articular processes
- These joints are in the coronal plane; limits flexion + extension
- Slide past one another for rotation
Lumbar Vertebra
- Bodies have a kidney bean shape
- Found in small of back
- Have large bodies; have to transfer weight of body + head + neck
Specializations-
- Thick and strong lamina
- Vertebral foreman have a triangular shape
- blunt spinous process
Angle of articulation in sagittal plane - Allows for flexion and extension
Sacrum
- Wedge shaped bone; 5 fused vertebra
- Sacral foremana allow for passage of rami
- Allows for transfer of body weight into the pelvic girdle
Coccygeal
- Remnant of the tail the embryo has until 8 weeks
- Common to have an extra vertebra here or have a missing one
Normal Curvatures of the Human Vertebral Column
(fully developed by 10)
4 curvatures-
The thoracic and Sacral; convex posteriorly
- primary curvatures- develop during fetal development
- Accommodation curvature- makes room for organs
Sacrum less curved for females to increase size of pelvic outlet
Cervical and Lumbar; convex anteriorly
- Secondary curvatures- no not form until after birth
Cervical; when they start to hold their head up
Lumbar; when they start to walk
- Composition curvatures; Help bring center of gravity forward- hold head up
Abnormal Curvatures of Vertebral Column
1) Kyphosis- Hunch back; posterior curve
2) Scoliosis- Lateral curve
3) Lordosis- Too much forward curve in lumbar region
The Sternum
The breast bone (anterior wall of thoracic cavity medially)
Ribs
Pairs 1-7 attach directly to the sternum via their own costal cartilage- TRUE RIBS
Pairs 8-12- have costal cartilage that attaches to the costal cartilage of the rib superior(above) it; indirectly attached to sternum- FALSE RIBS
Pairs 11 and 12- do NOT attach to sternum; FLOATING RIBS
Posteriorly- Tubercle of rib articulates w/ the transverse process and the head of rib articulates w/ the vertebral body- Rib and transverse process share #
Angle of rib- Curves anteriorly and inferiorly provides support when you lay on your back
Parts of the sternum
Jugular notch/Suprasternal notch- notch at the most superior part of the sternum
Clavicular notch- Articulation between the axial skeleton and the appendicular skeleton (Clavicle)
Sternal angle; where you find the second rib
