how many bones are in the axial skeleton and name what it includes
The axial skeleton contains 80 bones
The axial skeleton includes:
1. Skull (8 cranial and 14 facial bones)
2. Vertebral column - 24 vertebrae, sacrum, coccyx
3. Thoracic cage (24 ribs + sternum)
4. Hyoid bone
5. 6 Auditory ossicles
what does the axial skeleton form along the axis of the body?
the axial skeleton forms the longitudinal axis of the body
how many bones are aprt of the appendicular skeleton and give examples
Appendicular skeleton
Includes 126 bones
Limbs + girdles
Pectoral (shoulder) girdle
Pelvic (hip) girdle
Upper and lower extremities
whats the main difference between axial and appendicular skeleton
👉 Axial = protection + support
👉 Appendicular = movement
what is the primary function of the skull, what does it protect, and what is the total # of bones, associated
Primary function:
Protects brain
Protects entrances to respiratory and digestive system
Total bones = 22
8 cranial → form the braincase/cranium
14 facial → protect and support entrances to digestive and respiratory tracts
what are the bones that are part of the cranium. there are 6 names and 8 in total.
These are the bones that form the cranium. The major bones are:
Frontal → forehead, superior orbits
Parietal (2) → superior lateral skull (on the top bilaterally)
temporal(2) → ear region
Occipital → posterior skull, foramen magnum
Sphenoid → articulates with many bones
Ethmoid → nasal cavity + medial orbit
there is only one movable skull bone that is a facial bone. what is it?
the mandible is the only movable skull bone that is the biggest and strongest, u shaped, and anchors lower teeth!
what are the 6 most improtant facial bones and their functions/structures
- mandible:
This is the largest and strongest facial bone
U shaped
Anchors lower teeth
Only movable skull bone - Maxillae
Upper jaw
Central facial region
Holds upper teeth - Zygomatic
Cheek bones
Contribute to orbit margins - Nasal bones
Bridge of nose - Vomer
Forms nasal septum and separates the cranium from the bottom part, posteriorally located - Lacrimal bones
Tear duct passes here and drainage pathway
what is the external occipital crest
the external occipital crest is a part of the occipital bone and is attachment of ligaments (bone to bone) posture as well!!!
what is the mental protuberance
Mental protuberance → this is the site of attachment for facial muscles. U shaped
Which facial bone articulates with which cranial bone to form the zygomatic arch?
The zygomatic process of the temporal bone articulates with the temporal process of the zygomatic bone.
what are sutures and what are the 4 major sutures functions
Definition: sutures are the immovable joints of the skull of adults that are tied firmly together through dense fibrous connective tissue
Major sutures:
1. Lambdoid suture connect the occipital with parietal
2. Coronal suture connect the frontal attached to parietal
3. Sagittal suture link two parietal together
4. Squamous suture connect temporal to parietal
These allow skull growth in infancy and fuse in adulthood
what are the fontanelles? what are they made up of? how do they relates to babies and how are fontanelles signiifcant?
Fontanelles are soft spots made of cartilage and have bone growth take over
These allow for brain growth and skull flexibility during birth, so overtime fontanelles close and the sutures fuse.
There are sphenoidal fontanelle, mastoid and anterior. The anterior fontanelle is the largest gap and very prominent when babies are born
what bone is the only bone that does not articualte with otehr bones and has a ligament attaching it to the back of the ear ? what is the function of this bone ?
the HYOID bone is Located inferior to the mandible, the
Only bone that does not articulate with other bones and Ligament attaching it to the back of the ear
Supports the tongue and larynx
Functional importance is speech and swallowing
what are paranasal sinuses and their functions
Paranasal sinuses
Paranasal sinuses are air filled spaces in skull bones:
There are:
Frontal sinus
Maxillary sinus
Ethmoid sinus
Sphenoid sinus
Functions:
- lighten the skull
- warm + moisten inhaled air
- protection
- the pressure of air makes the head lighter so it reduces pressure in the skull
what is the vertebral column compartments and functions
Components
24 vertebrae
Sacrum
Coccyx
Functions:
Protects spinal cord
Supports the head and body/trunk
Transfers body weight
what are the vertebral regions 5
Vertebral regions
- Cervical (7) → neck region C1-C7
- Thoracic (12) → rib articulation T1-T12
- Lumbar (5) → lower back, weight bearing L1-L5
- Sacral → 5 fused vertebrae
- Coccyx → tailbone
why is the cervical smaller than lumber
Cervical vertebrae are smaller than lumbar vertebrae because they support significantly less weight (only the head) and require higher mobility for neck movement. Conversely, the lumbar spine requires larger, stronger vertebrae to support the weight of the entire torso
what is normal spinal curvature vs abnormal spinal curvature and health condition linked to it
Normal curves:
Cervical
Thoracic
Lumbar
Sacral
Abnormal curvature:
Scoliosis is a twisted disease of abnormal lateral curvature that occur commonly in the thoracic region
what are intervertebral discs and what are they made up of, as well as what is their function
Invertebral Discs
Located between vertebral bodies
- Invertebral discs are made up of fibrocartilage/collagen fibers and their basic function is to absorb shock (running, jumping, bending)
Functions are:
Shock absorption
Flexibility
Prevent bone on bone friction
WHAT IS THE VERTEBRAL CANAL?
the vertebral canal houses and protects the spinal cord and passes through the head and caudal region
explain C1 and C2 and how they work together
C1 (Atlas)
- lack of vertebral body
- lack of spinous process
- presence of large round vertebral foramen with anterior and posterior arches
- supports skull
C2 (Axis)
- robust/strong spinous process
- fusion with atlas creates dens
Atlas + axis = nodding + rotation movements
what are dens of odontoid process and wht does it allow us to do
dens of odontoid process is a bony projection on C2 (cervical vertebra) and acts as a tooth like projection that sticks upward from the body of the axis and fits into the first cervical vertebra (C1, atlas)
- project superiorly upward from C2 and sit inside C1, held in place by the transverse ligament of the atlas
- allows us to move our head horizontally/right and left
what allows us to move our head up and down and horizontally
C1 allows us to move up and down, articulation between C1 and C2 (dens) allows us to move horizontally
