The Skeleton

Question 1

Skeletal Subdivisions

Answer 1

Axial -Postcranial -Vertebrae

                          - Thorax
     - Cranial (Skull) - Canium
                              - Facial

Appendicular - Pelvic girdle

                    - Pelvic Limb
                    - Pectoral girdle
                    - Pectoral limb

Question 2

What is a skeleton?

-5 functions of the skeleton

Answer 2

-Skeleton comprises of bone that is articulated at joints and are united by ligaments. Also includes cartilage

FUNCTIONS:

• provides body form
• Forms non-collapsible cavities
• Levers for muscle action
• Houses bone marrow
• Calcium/Phosphate store

Question 3

Number of bones in the different components of skull

Answer 3

Skull = 22 bones

• Cranial bones = 8 (direct contact w/ brain)
• Facial Bones = 13 (no brain contact)
• Mandible = 1 (lower jaw)

Question 4

Sutures: what they are & 3 types

Answer 4

• Suture: generally convoluted thick fibrous joints between plates (in skull)
  
  • some fuse, though some maintain through life

3 types w/in skull:

• Coronal suture: separates frontal bone from parietal bones
• Sagittal suture: between left and right parietal bones
• Lambdoid suture: between parietal bones and occipital bones

Question 5

What is the:

Hyoid

Hard palate

Answer 5

-Hyoid chain of single bones that have fused in humans - supports and protects larynx

• Hard palate: mammalian features allowing infants to suckle
  
  • separates nasal and oral cavities
  • formed by shelf-like horizontal extensions of maxilla and palatine bones
    
    • failure of process = cleft plate

Question 6

The Human Spine

Answer 6

-has a triple curvature to balance body weight vertically

FORMULA: C7-T12-L5-S5-Co4

• Cervical vertebrae (7 bones)
• Thoracic vertebrae (12 bones)
• Lumbar vertebrae (5 bones)
• Sacrum (5 fused bones)
• Coccyx (4 fused bones)

Kyphosis: curves backwards (spine curves more towards posterior)
Lordosis: curves forwards (spine curves more towards anterior)
Scoliosis: curves to side

Question 7

The Atlas & the Axis (C1 & C2 of cervical vertebrae)

Answer 7

Atlas:

• articulates w/ condyles of occipital bone (in skull)
• has deep superior artiular facets
• lacks a body
• allows us to nod our head*

Axis:

• has odonoid process or dens
• acts as axis of rotation between atlas and skull
• dens is what fits inside atlas
• atlanto-axis = no movement

X for no

Question 8

Thorax

Answer 8

• 7 pairs of true ribs (1-7) [directly connect to sternum]
• 5 pairs of false ribs (8-12) [not directly connected to sternum]
  
  • 2 of which are floating ribs (11-12) - not connected to sternum at all

Question 9

Pectoral Girdle

Answer 9

• consist of 3 main elements: scapula, clavicle and coracoid (fused to scapula)
• clavicle derived from dermal bone of skull and forms by intramembranous ossification
• more highly evolved than pelvic girlde

Question 10

Pelvic Girdle

Answer 10

-Retains its 3 ancestral elements: ilium, ishium and pubis (all unite at acetabulum

Question 11

Limb Homology

Answer 11

• Both limbs consist of similar sequence of bones and joints
• *modern tetrapods are all ancestrally pentadactyl
• carpus and tarsus (wrist and ankle) consist of jumble of short bones
• carpals = hands
• tarsals = feet