Ch 5 Skeletal System The Axial Skeleton

Do Now: What is the difference between a projection and a depression? What is something interesting you have learned about the skeletal system so far?

The Axial Skeleton Forms the longitudinal part of the body Divided into three parts Skull Vertebral column Bony thorax (Ribs)

The Axial Skeleton Figure 5.6

The Skull Two sets of bones Bones are joined by sutures Cranium Facial bones Bones are joined by sutures Only the mandible is attached by a freely movable joint

Cranium Frontal bone Parietal bone Temporal bones Composed of eight large flat bones, all single, except for two paired bones (parietal and temporal) Frontal bone Forms the forehead, under the eyebrows, and the superior part of each eye’s orbit Parietal bone Paired bones that form the most superior and lateral walls of the cranium Temporal bones Inferior to the parietal bones

Cranium Occipital bone Sphenoid bone Ethmoid bone Most posterior bone of the cranium. Forms the floor and back wall of the skull In the base of this bone, is the foramen magnum, a large opening that allows the brain to connect to the spinal cord Sphenoid bone Goes the width of the skull and forms part of the floor of the cranial cavity Ethmoid bone Anterior to the sphenoid and forms the roof of the nasal cavity and part of the medial walls of the orbits(eyes)

The immovable joints of the skull Sutures Figure 7–3a, b

Sutures - Four Major Ones Lambdoid suture – separates occipital from parietal Coronal suture – attaches frontal to parietal Sagittal suture – between parietal bones Squamous suture – between temporal and parietal

Facial Bones Fourteen bones compose the face. Twelve paired, only the mandible and vomer are single

Facial Bones Maxillae or maxillary bones Fuse to form the upper jaw All facial bones, except the mandible join the maxillae Palatine bones Paired bones that form the posterior part of the hard palate Zygomatic bones Cheekbones Also form parts of the lateral walls of the eye orbit Lacrimal bones Form the medial walls of each orbit Serves as a passageway for tears

Form the bridge of the nose Vomer bone Single bone Nasal bones Form the bridge of the nose Vomer bone Single bone Forms the nasal septum Inferior conchae Thin curved bones projecting from the lateral walls of the nasal cavity Mandible Lower jaw Largest and strongest bone of the face Joins the temporal bones on each side of the face Forming the only freely movable joint in the skull

The Skull

Bones of the Skull

Human Skull, Superior View

Human Skull, Inferior View

Paranasal Sinuses Hollow portions of bones surrounding the nasal cavity Figure 5.10

Paranasal Sinuses Functions of paranasal sinuses Lighten the skull Give resonance and amplification to voice Figure 5.10

The Hyoid Bone Serves as a moveable base for the tongue The only bone that does not articulate with another bone It is suspended in the midneck region above the larynx Figure 5.12

The Fetal Skull The fetal skull is large compared to the infants total body length Figure 5.13

The Fetal Skull Fontanelles – fibrous membranes connecting the cranial bones Allow the brain to grow Convert to bone within 24 months after birth Figure 5.13

Axial Bones

Assignment Ch5 WS Pg3-4 Cranial and Facial Bones Matching Skull Labeling Diagram Due in twenty minutes

The Vertebral Column

The Vertebral Column Spine extends from the skull, which it supports, to the pelvis, where it transmits the weight of the body to the lower limbs

It is formed of 26 irregular bones connected by ligaments The Vertebral Column It is formed of 26 irregular bones connected by ligaments The spine has a normal curvature

Region Name Specific Vertebrae The Vertebral Column Each vertebrae is given a name according to its location Region Name Specific Vertebrae Cervical C1-C7 Atlas C1 Axis C2 Thoracic T1-T12 Lumbar L1-L5 Sacrum Fused Coccyx Fused

The Vertebral Column Vertebrae separated by intervertebral discs Intervertebral discs cushion and absorb shock between the vertebrae As a person ages, they are susceptible to herniated discs (slipped)

Vertebrae 7 cervical 12 thoracic 5 lumbar sacrum coccyx

Vertebral Column Figure 5.14

Form of the vertebral column Cervical vertebrae (C1 – C7) Forms the neck C1 – the atlas, allows you to nod “yes” C2 – the axis, allows for the rotation and you to move from side to side to say “no” C3-C7 – smallest and lightest vertebrae

Form of the vertebral column Thoracic vertebrae (T1-T12) Lumbar vertebrae (L1-L5) Sacrum -- heartshaped Formed by the fusion of five vertebrae Forms the posterior wall of the pelvis Articulates with the sacroiliac joints Coccyx Formed by the fusion of three to five small irregularly shaped vertebrae Tailbone

Structure of a Typical Vertebrae Figure 5.16

Regional Characteristics of Vertebrae Figure 5.17a–b

Regional Characteristics of Vertebrae Figure 5.17c–d

Curvature of the spine The disks and S-shaped structure of the vertebral column work to prevent shock Primary curvatures – curvatures of the thoracic and sacral regions and are present at birth Secondary curvatures – cervical curvature develops as a baby raises their head, and lumbar curvature develops as a baby begins to walk

Abnormal curvature of the spine May be present at birth or result from disease or poor posture Scoliosis – medial or lateral (right or left) curve Kyphosis – curve at the superior or thoracic part of the spine Lordosis – curve at the inferior or lumbar part of the spine

Scoliosis

Lordosis

Assignment for Part 2 Skeletal WS Pg5-6 Paranasal Sinuses Vertebral Column Spine Labeling Diagram

The Bony Thorax Forms a cage to protect major organs Made-up of three parts Sternum Ribs Thoracic vertebrae Figure 5.19a

Sternum – breastbone Flat bone and the result of the fusion of three bones: Manubrium Body Xiphoid process It attaches to the first 7 ribs

Ribs 12 pairs of ribs forms the walls of the thoracic cage True ribs – first 7 pairs of ribs attach directly to the sternum by costal cartilages False ribs – next 5 pairs, either attach indirectly to the sternum or are not attached to the sternum at all Floating ribs – last two pairs of false ribs lack the sternal attachments Intercostal spaces are filled with intercostals muscles that aid in breathing

Axial Skeleton Video 05 Human Body Skeletal System 5:09-7:42

Ch5 Ws Pg6 Ribs Labeling Diagram Assignment Ch5 Ws Pg6 Ribs Labeling Diagram