The Skeletal System:
Axial Division
Introduction
The axial skeleton:
Functions as a framework that supports and protects organs in the dorsal and ventral body cavities.
Contains the special sense organs for taste, smell, hearing, balance, and vision.
Serves as attachment sites for muscles that:
Adjust the posture of the head, neck and trunk.
Move the thoracic cage for respiration.
Stabilize the appendicular skeleton.
The Skull and Associated Bone
Sutures
The Cranium
The cranial cavity is a fluid-filled chamber that supports and protects the brain.
Bones of the cranium are the:
Occipital
Parietal (2)
Frontal
Temporal (2)
Sphenoid
Ethmoid
Occipital Bone
Parietal Bone
Frontal Bone
Temporal Bone
Sphenoid Bone
Ethmoid Bone
The Cranial Fossae
The Facial Bones
The skull contains 14 total facial bones:
Paired bones:
Maxillae
Palatine
Nasal
Zygomatic
Lacrimal
Inferior nasal conchae
Single bones:
Vomer
Mandible
Maxillary Bones
The Palatine Bones
The Nasal Bones
The Inferior Nasal Conchae
The Inferior Nasal Conchae
The Zygomatic Bones and Lacrimal Bones
The Vomer
The Mandible
The Orbital and Nasal Complexes
The Orbital and Nasal Complexes
Paranasal Sinuses
Found in frontal, ethmoid, sphenoid, and maxillary bones.
Reduce the weight of the skull, produce mucus, and allow air to resonate for voice production.
Frontal sinus, maxillary sinus, sphenoidal sinus, and the ethmoidal air cells
The Hyoid Bone
The Skulls of Infants
The Vertebral Column
The adult vertebral column has 26 bones:
Vertebra (24), sacrum (1), and coccyx (1)
Performs several functions:
Encloses and protects the spinal cord
Supports the skull
Supports the weight of the head, neck, and trunk
Transfers weight to the lower limbs
Helps maintain the upright position of the body
The Vertebral Column
Divided into regions from superior to inferior:
Cervical (7)
Thoracic (12)
Lumbar (5)
Sacral (1); 5 fused vertebrae
Coccygeal (1); 3–5 fused vertebrae
Spinal Curves
Spinal curves are weight transferring anterior and posterior curves.
The spinal curves are named for the region of the vertebral column they occur in:
Cervical curve
Thoracic curve
Lumbar curve
Sacral curve
Spinal Curves
Primary curves - posterior curves
Secondary curves – anterior curves
Vertebral Anatomy
Vertebral Anatomy
Cervical Vertebrae
Seven total - smallest
The spinous processes: relatively stumpy; may have bifid process.
Costal processes
Transverse foramina
The Atlas (C1)
No body, articulates with occipital condyles.
Anterior and posterior vertebral arches.
Superior and inferior articular facets do not extend beyond the arches.
The Atlas (C1)
The Axis (C2)
The body of the atlas fuses with the body of the axis during development to form the dens (odontoid process).
No intervertebral disc
The Axis (C2)
Vertebra Prominens (C7)
Resembles the thoracic vertebra
Long, slender spinous process, and enlarged transverse processes that may or may not contain a transverse foramen.
An elastic ligament called the ligamentum nuchae extends from the spinous process cranially to the occipital crest.
Thoracic Vertebrae
12
Spinous process points on a posterocaudal angle.
The transverse processes point dorsolateral.
Extra facets for ribs
Lumbar Vertebrae
5
Largest Vertebrae
Square Spinous process
Lateral transverse process
The relatively small vertebral foramen is triangular.
Sacrum and Coccyx
The Thoracic Cage
Has two functions:
Protects the heart, lungs, thymus, and other structures within the cavity.
Serves as the attachment site for muscles involved in:
Respiration
Positioning the vertebral column
Movements of the pectoral girdle and upper limb
The Thoracic Cage
Ribs
12 pairs
7 pairs of true ribs
5 pairs of false ribs
2 pairs of floating ribs
Sternum
Manubrium, body and xiphoid process