1. The Skeletal System – Part 2
Learning Outcome C1

2. Divisions of the Skeletal System
There are two division:
Axial
Appendicular

3. Axial Skeleton Bones of the skull Hyoid bone Bones of the middle ear
Vertebral column
Bony thorax

5. Appendicular Skeleton
Bones of arms and legs
Bones of hip and shoulder girdles

6. Axial Skeleton
Skull
Formed by two groups of bones: facial bones and cranium
Several of these bones contain spaces called sinuses

7. Axial Skeleton Cranium
Bony structure that encases and protects the brain
Composed of 8 bones

8. 8 Bones of the Cranium Frontal Bones Parietal bones
Forms the forehead, part of the nose and parts of he bony structure surrounding the eye
Parietal bones
Two
Forms most of the top of the head and part of the sides of the head.

9. 8 Bones of the Cranium Temporal Bone Two On side of head close to ears
Several important bone markings are found in the temporal bones:
Auditory meatus – opening of ear
Zygomatic process – forms part of cheekbone
Styloid process – sharp projection used for attachment of muscles with tongue and larynx

10. 8 Bones of the Cranium Occipital Bone Located at base of the skull
Large hole in bone is called the foramen magnum , on either side of the foramen magnum are bony projections known as occipital condyls.

11. 8 Bones of the Cranium Sphenoid bone Butterfly shaped one
Forms part of the floor and sides of cranium
Also forms part of eye orbits
Has a depression along the midline that houses the pituitary gland

12. 8 Bones of the Cranium Ethmoid Bone
Irregularly shaped bone that helps form the bony structures of noses.

13. Facial Bones
There are 14 facial bones, most of which are paired

14. Facial Bones Mandible Lower jaw Anterior portion of the jaw
Has two bony processes that articulate with the temporal bones at the temporal mandibular joint, which is a point of attachment for chewing muscles.

15. Facial Bones Maxilla Upper jaw
An extension of the maxilla is the palatine process that makes up the anterior portion of the hard palate
Also form part of the nasal cavity and eye orbits

16. Facial Bones Pallatine Bones
Forms the posterior part of the hard palate and the floor of the nasal cavity
Failure of the palatine bones to fuse can result in a cleft palate

17. Facial Bones Zygomatic Bones Cheek bones
Form part of the orbits of the eyes

18. Facial Bones Other Facial Bones
Make up the rest of the facial structures
Includes vomer, lacrimal bones and nasal bones
Sinuses are named based on their location in the skull bone: frontal sinus, ethoidal sinus, sphenoidal sinus and maxillal sinus

19. How do skull bones fuse?
The adult skull forms a unique joint called a suture.
Looks like a zipper
The major sutures are:
Coronal sutures
Lamboidal sutures
Aquamosal sutures
Prevents the movement of cranial bones

20. How do skull bones fuse together?
An infant skull is not fused to allow the movement of the infant through the birth canal.
Microcephalia is a condition where the cranium bones fuse too early preventing the brain from growing and developing
Symptoms: small head and impaired intellectual capacity
Hydrocephalus occurs when there is too much fluid on the bran, causing the skull to enlarge.

21. Bones of the Neck and Ear
Hyoid Bone
U-shaped bone located in the neck
Anchors tongue and allows swallowing
Only bone that does not articulate with another bone
Bones of the Middle Ear
Contains 3 small bones called ossicles

22. Vertebral Column Extends from the skull to the pelvis
Small stacked bones
Between each vertebra is a cartilaginous disc that acts as a shock absorber.
Vertebrae have four major functions:
Support structures of head and thorax
Allow attachment to pelvic girdle
Encase

23. Vertebral Column Named according to location
7 cervical vertebrae (C1-C7)- located in neck region
12 thoracic vertebrae (T1-T12) – located in chest region
5 lumbar vertebrae (L1- L5) – located in lower back
5 saccral vertebrae fuse to form the sacrum
4-5 coccygeal vertebrae fuse to form the tailbone

24. Two Special Vertebrae Atlas (C1)
Have depressions that fit the projections of the occipital bone of the skull.
Supports the skull and allows you to nod “yes”.
Axis (C2)
Has a projection that fits into the atlas and acts as a pivot for the atlas.
Allows head to nod “no”.

25. Appendicular Skeleton
Composed of bones of the shoulder girdle, upper limbs, pelvic girdle and lower limbs.
Shoulder Girdle
Composed of two bones: clavicle and scapula
Should supports arm and serves as a place of attachement for muscles
Designed for greater flexibility

26. Shoulder Girdle Clavicle (AKA collarbone)
Long bone that articulates with both the sternum and scapula.
Most easily broken bone in the body
Scapula
Articulates with clavicle and serves as a point of attachment for arm and chest muscles.
Glenoid cavity allows the head of the humerus to fit, so you can rotate your shoulder.

27. Thoracic Cage
Surrounds and protects the lungs, heart and large blood vessels
Plays a role in breathing
Supports the bones of the shoulder
Composed of sternum, ribs and thoracic vertebrae
Sternum located in the centre of the chest

28. Thoracic Cage
There are 12 pairs of ribs attached posterior to the thoracic cage
Top 7 ribs are attached directly to the sternum by costal cartilage and are known as true ribs
Next five ribs attach indirectly to the sternum and are known as false ribs
Bottom two ribs are known as floating ribs because they do not attach to sternum and can be easily broken

29. Arms Upper arm – humerus Forearm – radius and ulna
Hand – carpels, metacarpels and phalanges

30. Humerus Long bone of arms
Head of bone fits into glenoid cavity of scapula, allows shoulder t rotate
Opposite end articulate with bones of forearm

31. Radius Located on thumb-side when palm is facing forward
Head of radius articulates with the ulna and humerus

32. Ulna Located on little finger side of the forearm
Articulates with humerus, radius and bones of the writes

33. Hand The and is composed of the wrist, palm and fingers
8 bones called carpels are tightly arranged around ligaments
5 metacarpels form the palm of the hand
14 bones – phalanges
Each digit has three bones, thumb has two bones