1. The Skeletal System: The Axial Skeleton
Chapter Seven
The Skeletal System:
The Axial Skeleton

2. Introduction
Familiarity with the names, shapes, and positions of individual bones helps to locate other organs and to understand how muscles produce different movements due to attachment on individual bones and the use of leverage with joints.
The bones, muscles, and joints together form the musculoskeletal system.

3. Division of the Skeleton
Adult has 206 named bones. Most are in pairs (one right, one left). Infants and children have more, because some of them fuse later together)
Axial skeleton:
Consists of bones along the axis of the body
Consists of 80 bones: skull, hyoid bone, bertebral column, sternum, and ribs
Appendicular skeleton
Consists of 126 bones (arms and legs)
Attached to the axial skeleton

4. Types of Bones
Bones are classified according to their shape: long bones, short bones, flat bones, irregular bones, sesamoid bones (shaped like a sesame seed)

5. 1. Skull Consists of 22 bones
Located on superior end of the vertebral column.
Includes two sets of bones:
8 cranial bones (brain case) = encloses + protects
the brain
14 facial bones (form the face)
Consists of 22 bones
Located on superior end of the vertebral column.
Includes two sets of bones:
8 cranial bones (brain case) = encloses + protects the brain
Frontal bone, two parietal bones, two temporal bones, occipital bone, sphenoid bone, and the ethmoid bone.
14 facial bones (form the face)
Two nasal bones, two maxillae, two zygomatic bones, mandible, two lacrimal bones, two palatine bones, two inferior nasal conchae, and the vomer

6. Two frontal bones
Two parietal bones
Two temporal bones
The occipital bone
The sphenoid bone
The ethmoid bones
Facial:
Two nasal bones
Form part of the bridge for the nose
Two maxillae
Form the upper jawbone
Two zygomatic bones
Form the cheekbones
The mandible
Is the jawbone – the largest and strongest facial bone and the only movebale skull bone
Two lacrimal bones (inside the eye)
Form part of the wall inside the eye socket. Is the smallest bone of the face
Two palatine bones (see figure 7.7. Underneath the teeth (light purple)

7. Two inferior nasal conchae (see figure 7.3, above vomer)
Form inside wall of nasal cavity
Vomer (see figure 7.3, middle of the nose
Now if you look closer at this picture you realize what the frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal and ethmoid bones do? They form the orbit (eye socket) Look at Fig. 7.12

8. Unique Features of the Skull
Sutures
Immovable joints that
hold the parietal bones
and the occipital bone
together (7.6) (7.4)
squamous suture
lambdoid suture
coronal suture

9. Unique Features of the Skull
Paranasal Sinuses
Spaces in the frontal, sphenoid, ethmoid and maxillary bones that connect nasal cavity

10. Unique Features of the Skull
Fontanels
Cartilage
and connective
tissue
Close up
Babies heads consists mainly of cartilage and connective tissue. Later ossification occurs and bone replaces the cartilage.
Fontanels are fibrous connective tissue between the cranial bones. They are flexible (they must be, in order to be pushed through the birth canal. Allow rapid growth of the brain during infancy.
anterior fontanel: closes months
posterior fontanel: closes around 2 months
anterolateral fontanels: closes around 3 month
posterolateral fontanel: start closing around 1,2 months, finished by 12 months.

11. Hyoid Bone Is not in contact with any of the other skull bones
Supports the tongue by attachment to muscles of the tongue, neck and pharynx.

12. 2. Vertebral Column
The vertebral column, along with the sternum and ribs make up the trunk of the skeleton
4 vertebral curves, 26 bones are divided into 5 regions:
Cervical
Thoracic
Lumbar
Sacrum
Coccyx
The vertebral column, along with the sternum and ribs make up the trunk of the skeleton
4 vertebral curves, 26 bones are divided into 5 regions:
Cervical : the neck
Thoracic : chest
Lumbar : lower back
Sacrum : 5 fused vertebrae
Coccyx : (KOK-siks) = means cuckoo (looks like the bill of a cockoo) 4 fused vertebrae
Check out the hand-out VAHA page 73

14. Cervical Region There are 7 cervical vertebrae
The first is called atlas = supports the skull
The second is called axis = permits side to side rotation of the head
3 – 6 = go along with the body movement
7 a bit different (vertebra prominens)

16. Thoracic Region 12 thoracic vertebrae
Must larger and stronger than the cervical vertebrae.
Connection with the ribs.
3 basic features:
Body – bears weight and increases in size as one moves down the vertebral column
Vertebral ach –
Articular processes (2) to join the vertebra together
Page 77 VAHA

17. Lumbar Region
The largest and strongest – supports large amount of body weight.
5 vertebrae
VAHA page 79

18. Sacrum and Coccyx
Sacrum (5 sacral vertebrae) strong foundation for the pelvic girdle
Coccyx (COC-siks) formed by the fusion of 4 vertebrae.
Used during labor
If broken – paralyses from hip down

19. 3. Thorax The entire chest: Collar bone (cavicle) Sternum
Breastbone: flat narrow bone of about 6 inches. Connected to ribs by costal cartilage.
Ribs
12 pair of ribs. First 7 are true ribs, 5 false ribs (last 2= floating ribs)

20. 3. Thorax False ribs Floating ribs Costal cartilages
Do not directly connect to the sternum via costal cartilage
Floating ribs
Last 2 ribs (11, 12) do not attach at all
Costal cartilages
Now according to the Bible God created Eve out of a rib of Adams. So Adam has only 11 pair of ribs. Which means that men have one rib pair less than women. Is this a true statement?

21. Disorders: Homeostatic Imbalances
Herniated Disc (slipped disc)
Often happens in lumbar region (most weight and stress) nucleus pulposus may herniate (protrude) causing pain and nerve damage
Spina Bifida
A defect in which part of one or more vertebrae fail to develop completely.