The parts of the Skeletal system

1. The parts of the Skeletal system

2. Parts of the Skeletal System • Three are two main parts to the skeletal system: • The axial skeleton made up of skull, vertebral column, bony thorax, and hyoid bone. • The appendicular skeleton made up of the upper and lower extremities, the shoulder girdle and the pelvic girdle.

3. The Skull • Consists of the cranium and the facial bones. • The cranium houses and protects the brain. • The facial bones hold and protect the eyes, forms the nose and mouth areas. • Altogether, there are 22 bones associated with the skull.

4. The Cranium • The back portion of the skull. • Consists of 8 flat bones that fuse together. • During infancy, the bones were held together with fibrous membranes that eventually ossified and left immovable joints called sutures.

5. The Cranium

6. The Cranium

7. Frontal Bone • Forms the forehead • Includes the bony projections under the eyebrow and the superior part of each eye orbit. Frontal Bone

8. Parietal Bones (2) • Forms the superior and lateral walls of the cranium. • They meet at the superior midline of the skull at the sagittal suture • Meets the posterior edge of the frontal bone to form the coronal suture

9. Parietal Bones Sagittal Suture Coronal Suture Parietal bone (right) Parietal bone (left) Parietal Bone Frontal Bone

10. Temporal Bones (2) • Lie inferior to the parietal bones. Fuse with the parietal bones at the squamous sutures. Squamous suture Temporal bone Temporal Bone Temporal bone

11. Temporal Bones • Have several important bone markings: • 1. external auditory meatus – the canal that leads into the ear and eventually the ear drum • 2. styloid process – a needle-like projection inferior to the external auditory meatus; for muscle attachment • 3. zygomatic process – a bridge of bone that joins with the cheekbone

12. External auditory meatus Zygomatic process Styloid process

13. Temporal Bones • 4. mastoid process – a rough projection posterior and inferior to the external auditory meatus; an attachment site for some neck muscles. • 5. jugular foramen – an opening at the junction of the occipital and temporal bones; allows for the jugular vein to pass through (drain the brain). • 6. carotid foramen – smaller opening anterior to the jugular foramen that allows the carotid artery to pass (supplies blood to the brain).

14. Carotid foramen Mastoid process Jugular foramen

15. Occipital Bone • The most posterior bone of the cranium. • Joins the parietal bones at the lambdoid suture. • Has a large opening at the base called the foramen magnumwhich allows the spinal cord to connect with the brain.

16. Lambdoid Suture Occipital Bone Foramen Magnum

17. Sphenoid Bone • A butterfly-shaped bone that is seen on the sides of the cranium, anterior to the temporal bones • Forms the backs of the eye orbits. • Separates the brain from the face.

18. Sphenoid Bone Sphenoid Bone

19. Sphenoid Bone

20. Ethmoid Bone • Irregularly shaped bone that is anterior to the sphenoid bone. • Forms the roof of the nasal cavity and part of the medial walls of the orbits (eye sockets).

21. Ethmoid Bone

22. The Young Cranium • The infants face is very small compared to the size of the cranium, but the skull as a whole is large compared to the size of the body. *As mentioned before, some areas of cartilage still have to be converted to bone.

23. The young cranium also has fibrous membranes, or fontanels, where the cranial bones do not quite meet. These are commonly referred to as “soft spots”.

24. Eventually the bones grow and the fontanels ossify.