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Chapter 7
The Axial Skeleton
I.
The Axial Skeleton- 80 Bones
A.
B.
C.
D.
II.
The Skull 8 Cranial Bones and 14 Facial Bones
Bones Associated w/Skull 7 (3 per ear and the hyoid bone)
Thoracic Cage 24 Ribs & the Sternum
Vertebral Column 24 Vertebrae, the Sacrum and the Coccyx
The Skull (22 bones)
A. Cranial Bones- enclose brain, fluid, blood vessels:
1. Occipital Bone (1)- Posterior
2. Frontal Bone (1)- Anterior
3. Parietal Bones (2)- Superior
4. Temporal Bones (2)- Lateral
5. Sphenoid-1
6. Ethmoid-1
B. Facial Bones- protect and support entrances to digestive & respiratory
tracts:
1. Superficial Facial Bones- provide attachment sites for muscles that control
facial expressions and assist in manipulating food
a. Maxillary-1
b. Lacrimal-2
c. Nasal-2
d. Zygomatic-2
e. Mandible-1
2. Deeper Facial Bones- help separate the oral and nasal cavities
a. Palatine bones-1
b. Nasal concha- 2
c. Vomer-1
C. Associated Bonesa. Auditory ossicles- 3 per ear
b. Hyoid bone (neck)- ligaments attach it to temporal bone
D. Sutures- immovable joints- connected by dense fibrous connective tissue
a. Lamboidal- Connects occipital to the parietal bones
b. Coronal - Connects the frontal to the parietal bones
c. Squamous- Connects the temporal to the parietal bones
d. Sagittal- Between the left and right parietal bones
e. Occipitomastoid- between the occipital bone and mastoid process
*Sinuses- lighten bones & provides framework for mucus membrane
*Joints (articulations)- two bones connect
III.
The Vertebral Column- Supports and Protects
A. 4 Spinal Curves- S-Shaped fully developed by age 10
1. Cervical
2. Thoracic
3. Lumbar
4. Sacral
B. 4 Regions- each vertebrae separated by Intervertebral Disks
1. Cervical- C1-C7
“Breakfast at 7”
a. C1- Atlas articulates with occipital condyles of the skull
b. C2- Axis articulates with C1, pivot for rotation of atlas
c. Small and light- only job is to support the head
d. Muscles stabilize massive head on small vertebrae has limits i.e.- whiplash
2. Thoracic- T1-T12 “Lunch at 12”
a. Larger Body, smaller vertebral foramen
b. Articulate with ribs
3. Lumbar- L1-L5
“Dinner at 5”
a. Largest vertebrae
b. Bear the most weight
c. Large spinous process for lower back muscle attachment that reinforce the
lumbar curve
4. Sacral- Sacrum and Coccyx
a. Sacrum- Composed of 5 fused sacral vertebrae (fused by age 30) protects
reproductive, digestive and urinary organs
b. Coccyx (tailbone- 3-5 fused vertebrae) attachment site for ligaments for a
muscle that constricts the anal opening.
IV.
The Thoracic Cage- made of thoracic vertebrae, ribs and sternum
A. Protects organs of the thoracic cavity and serves as attachment points for muscles
B. The Ribs (costae)- 12 pairs
1. Pairs 1-7  “True Ribs” or Vertebrosternal Ribs
a. Connect to the sternum via costal cartilage
2. Pairs 8-10 “ False Ribs” or Vertebrochondral Ribs
a. Connect to the cartilage of rib pair 7 which then connects to the sternum
3. Pairs 11-12 “False Ribs” or Floating Ribs
a. Only attached to vertebrae
4. Sternum- “breastbone”
a. Manubrium- articulates with the collar bones
b. Body- rib pairs 1-7 attach here
c. Xyphoid Process- diaphragm and rectus abdominus attach here