1. The Axial Skeleton
Chapter 5

2. The bones of the axial skeleton
The axial skeleton is composed of:
the cranium & facial bones (the skull)
hyoid bone
vertebral column
cervical vertebrae
thoracic vertebrae
lumbar vertebrae
Sacrum & coccyx
Thorax (ribs and sternum)

3. The Skull
The skull is composed of the cranium and facial bones. These bones are joined together by sutures which are immovable joints.

4. Cranium
Cranium – has 8 large flat bones. They are all single bones except for the parietal and temporal bones.

6. Cranium – Frontal bone & Parietal bone
The Frontal Bone – the forehead, the bony part of the eyebrow and the bottom of the eye’s orbit.
Parietal bone – forms the superior and lateral walls of the cranium. They meet at the sagittal suture and coronal suture.

7. Cranium – temporal bone
3) Temporal bone – forms the superior and lateral walls of the cranium. The “temple”
a) external auditory meatus – eardrum & middle ear
b) styloid process – sharp projection which is the attachment point for many muscles
c) zygomatic process – thin bridge of bone that is the cheek bone
d) mastoid process – bone below the ear that provides attachment point for neck muscles
e) jugular foramen - junction of occipital and temporal bone. Houses the jugular vein that drains the brain.

8. Cranium – Occipital bone & Sphenoid bone
4) Occipital bone – forms the floor and back wall of the cranium
5) Sphenoid bone – spans the width of the skull. The turk’s saddle holds the pituitary gland in place. The sphenoid sinuses are housed in the area
6) Ethmoid bone – very irregular shape. It forms the roof of the nasal cavity. The area houses the cristi galli (attachment point for the brain covering) and the cribriform plates that receive messages from the smell receptors (olfactory).

9. Facial Bones
Fourteen bones make up the face. Twelve are in pairs, the mandible and vomer are single bones.
Maxillae – the upper jaw bones
Palentine – the posterior part of the hard palate
Zygomatic – cheekbones/ eye sockets
Lacrimal – located near the tear ducts
Nasal – forms the bridge of the nose
Vomer – forms the nasal septum
Inferior Conchae – forms lateral walls of the nasal cavity
Mandible – lower jaw bones/ largest and strongest bone of the face

11. The Hyoid Bone
The hyoid bone does not connect (articulate) with any other bone. This is unique compared to the other bones. It is located in front of the larynx where it connects to the styloid process by ligaments.

12. Fetal Skull & body
The newborn skull is different from the adult skull.
Adults – 1/8 of body length
Infants – ¼ of body length
Infant skeletal system is mostly made of cartilage which ossifies later. The cartilage regions of the skull are known as fontanels. The anterior and posterior fontanel allows the baby’s head to change slightly as it passes through the birth canal. They disappear at months.

13. Fetal Skull

14. Fetal Skull

15. My daughter Isabel after birth

16. Vertebral Column The vertebrae extends from the skull to the pelvis.
There are 26 irregular shaped bones in the vertebrae.
They are surrounded by reinforcing ligaments and cover the spinal cord.
The sacrum and coccyx are made of 9 bones that fuse together.
They are as follows: 7 cervical, 12 thoracic, 5 lumbar, sacrum, and coccyx

18. Vertebral Column
Each vertebrae has a flexible fibrocartilage that acts as a cushion and shock absorber. As the bones get older, they are more susceptible to herniated (protruding) disks. These disks compress the nerves and create numbness and pain.

19. Abnormal Spinal curvatures:
1) scoliosis – “S” shaped spine

20. Abnormal Spinal curvatures:
2) kyphosis – hunched shoulders (often associated with age)

21. Abnormal Spinal curvatures:
3) lordosis – sway back

22. Features of Vertebrae:
1) body – weight bearing part of disk
2) vertebral arch – joining of lamina & pedicle
3) Vertebral foramen – hold the spinal cord
4)Transverse process – two lateral projections
5) spinous process – single medial projection
6) superior/inferior articular processes – allows the vertebrae to join with the other vertebrae

24. Cervical Vertebrae Neck region of the spine The first two are:
1) atlas – receives the occipital condyles of the skull. The “yes” motion
2) axis – a pivot point for rotation of the head. The “no” motion”.
Nerves and blood supply this area with feeling and blood.
Remember, there are 7 cervical vertebrae, C1 – C7

26. Thoracic Vertebrae There are 12 thoracic vertebrae.
They are larger than cervical vertebrae. T1-T12

27. Lumbar Vertebrae
Lumbar – there are 5 lumbar vertebrae. They are the strongest of the vertebrae because it supports the most weight of the body (L1-L5)
Sacrum – five fused vertebrae that connect with the hips forming the sacroiliac joint.
Coccyx – the fusion of 3-5 small irregularly shaped tail bones. The tail is very similar to other species of animals.

29. Bony Thorax
The sternum, ribs, and thoracic make up the bony thorax. The thoracic cavity protects the heart, lungs, and major blood vessels (aorta/vena)

30. Bony Thorax - Sternum
Sternum – flat breastbone that extends to the xiphoid process. There are 7 sets of ribs attached to the sternum. A sternal puncture is sometimes used to diagnose suspected blood diseases.

31. Bony Thorax - Ribs There are 12 pairs of ribs.
The first 7 pairs are true ribs while the last 5 pair are false ribs because they are not attached to the sternum.
The last two sets of ribs are floating ribs because they are not attached to the sternum or cartilage extending from the sternum.
The intercostals spaces (muscles) between each rib aid in breathing.