Anatomy: Axial Skeleton - Skull

• AHS 101 covers Anatomy and Physiology.
• Chapter 12 focuses on the Axial Skeleton.

Skeletal System Introduction

• Skeletal tissues form the bones.
• Bones are the organs of the skeletal system.
• The human skeletal system has 206 bones.

Divisions of the Skeleton

• Key divisions of the skeleton include the Axial and Appendicular skeletons.
• The Axial skeleton consists of the skull, hyoid, spine, and thorax
• The Appendicular skeleton consists of upper extremities (including the shoulder girdle) and lower extremities (including the hip girdle).

Divisions of the Skeleton – Axial - Skull

• The skull comprises 28 bones, categorized mainly as cranial or facial bones.

Cranial Bones (8)

• Frontal (1)
• Parietal (2)
• Temporal (2)
• Occipital (1) forms a moveable joint with C1
• Sphenoid (1)
• Ethmoid (1)

Facial Bones (14)

• Maxilla (2)
• Mandible (1) is the largest and strongest facial bone; forms the only moveable joint of the skull (w/temporal).
• Zygomatic (2) shapes cheeks
• Nasal (2)
• Lacrimal (2) contains a groove for the tear duct.
• Palantine (2)
• Inferior nasal conchae (2)
• Vomer (1)

Ear Bones

• Malleus/hammer 2, one of in each ear
• Incus/anvil 2, one in each ear
• Stapes/stirrup 2, one in each ear
• In summary there are 8 cranial + 14 Facial + 6 Ear = 28 skull bones total

Skull Spaces/Cavities/Caverns

• Numerous spaces, cavities, and caverns exist in the skull bones, referred to as sinuses, and are named based on the bones that contain them.

Fetal Skull

• The fetal skull has unique anatomical features not seen in the adult skull.
• 4 soft spots called fontanels allow the skull to be ‘flexible’ during birth and allow for rapid brain growth.

Divisions of the Skeleton – Axial- Hyoid

• The hyoid bone is U-shaped, located just above the larynx and below the mandible.
• It is suspended from the styloid processes of the temporal bone.
• The hyoid is the only bone in the body that doesn't articulate with any other bones.
• Is responsible for tongue movement and swallowing
• It is attached to muscles of the tongue & floor of the mouth

Divisions of the Skeleton – Axial - Spine

• The spine contains 24 vertebrae: 7 cervical, 12 thoracic, and 5 lumbar, as well as the sacrum and coccyx (tail bone).
• Curvature gives strength to support the body allowing people to stand and walk

Vertebrae

• Vertebrae are stacked in a way to give spine flexibility and strength
• The various parts of the vertebrae play an important role in controlling the movement of the spine.
• All have similar features, except C1.
• All vertebrae have a foramen.
• C2 has an upward projection (dens) to allow rotation of the head.
• C7 has a long, blunt spinous process
• Vertebrae articulate with each other.
• Thoracic vertebrae articulate with the ribs.
• As a whole, the vertebral column articulates with the head, ribs, iliac bones.

Divisions of the Skeleton-Axial - Thorax

• The thorax is the vertebral column + sternum + ribs.

Thorax

• Sternum is 'dagger' shaped
• The sternum sits in the middle of the chest
• Sternum contains 3 parts: Manubrium, Body and Xiphoid process
• Manubrium articulates with the clavicle & 1st rib.
• The Next 9 ribs are joined to the sternum body directly or via costal cartilage

Thorax and Ribs

• Each 12 pairs of ribs attach posteriorly to a thoracic vertebrae.
• All, except the lower 2 pairs, also attach anteriorly to sternum by costal cartilage.
• 8th, 9th & 10th pairs attach to the cartilage of the 7th ribs ('false ribs')
• 11th & 12th pairs don't attach to any costal cartilage ('floating ribs').

This lesson covers the axial skeleton, specifically the skull, as part of AHS 101 Anatomy and Physiology. It discusses the cranial and facial bones, including the frontal, parietal, and temporal bones, as well as the maxilla, mandible, and zygomatic bones.