Ch 7 axial skeleton

Axial Skeleton Forms the trunk or middle or longitudinal axis of the body. It has 80 bones, 40% of the bones in the human body. Made of: 1) skull – 8 cranial bones and 14 facial bones 2)bones associated w/ the skull – 6 auditory ossicles and the hyoid bone 3) vertebral column – 24 vertebrae, the sacrum, and the coccyx 4) thoracic cage – sternum and 24 ribs

Axial skeleton provides a framework that supports and protects the brain, spinal cord, and the organs in the ventral body cavities. It also provides a large surface area for attachment of muscles that 1) adjust the positions of the head 2) perform respiratory movements 3) stabilize or position parts of the appendicular skeleton

Skull 8 cranial bones and 14 facial bones 8 cranial bones Occipital bone Frontal bone Sphenoid Ethmoid Two parietal bones Two temporal bones

Sinuses Under facial bones are the sinuses(air-filled chambers). These function to: 1. they make a bone much lighter 2. the mucous membrane lining them produces mucus that moistens and cleans the air in and around the sinus

Sutures Joints or articulations, form where two bones interconnect. The skull bones of adults are immovable joints called sutures. At a suture, bones are tied firmly together w/ dense fibrous connective tissue. Each one has a name. 4 Main sutures: 1. Lambdoid Suture – arches across the posterior surface of the skull – separates the occipital bone from the two parietal bones 2. Coronal suture – attaches the frontal bone to the parietal bones of either side The calvaria is the skullcap made of the occipital,parietal, and frontal bones

Sutures (cont’d) 3. Sagittal Suture – extends from the lambdoid suture to the coronal suture between the parietal bones 4. Squamous sutures – One is one each side of the skull . They form a boundary b/t the temporal bone and the parietal bone of that side.

Know the diagrams on pp 216-217

Vertebral Column has 4 spinal curves Made of 26 bones (24 vertebrae, sacrum and coccyx) Provide a column of support, bearing the weight of the head, neck, and trunk. It also protects the spinal cord and helps maintain an upright position

4 spinal curvatures 1. cervical curve 2. Thoracic curve 3. lumbar curve 4. sacral curve See pg. 231 Fig. 7-16

Kyphosis – the normal thoracic curvature becomes exaggerated posteriorly, producing a “round-back” appearance Lordosis – “swayback” Scoliosis – lateral curvature of the spine

Between each vertebrae is a pad of fibrous cartilage called the intervertebral discs. 5 vertebral regions are: 1. cervical vertebrae (7) neck- C1-C7 2. thoracic vertebrae (T1-T12)-articulates w/ ribs 3. lumbar vertebrae (L1-L5) – articulates w/ sacrum which then articulates w/ the coccyx

Atlas – first cervical vertebra Cervical are the smallest vertebrae Thoracic vertebrae are typically heart shaped Lumbar vertebrae are the largest. Sacrum – made of 5 sacral vertebrae fused together(us. By age 20-25) Coccyx- 3-5 fused coccygeal vertebrae (us. By age 26)

Thoracic cage 1. protects heart, lungs, thymus, and other structures 2. serves as an attachment point for muscles involved in 1) respiration 2) maintenance of the position of the vertebral column and 3) movements of the pectoral girdle and upper limbs

Ribs 12 pairs 1st seven pairs are called “true ribs”. They are connected to the sternum by costal cartilages. Ribs 8-12 are called “false ribs” b/c they do not attach to the sternum Ribs 11 and 12 are specifically called “floating ribs” b/c they have no connection w/ sternum