The Skeletal System – Part 2 Learning Outcome C1

Divisions of the Skeletal System There are two division: Axial Appendicular

Axial Skeleton Bones of the skull Hyoid bone Bones of the middle ear Vertebral column Bony thorax

Appendicular Skeleton Bones of arms and legs Bones of hip and shoulder girdles

Axial Skeleton Skull Formed by two groups of bones: facial bones and cranium Several of these bones contain spaces called sinuses

Axial Skeleton Cranium Bony structure that encases and protects the brain Composed of 8 bones

8 Bones of the Cranium Frontal Bones Parietal bones Forms the forehead, part of the nose and parts of he bony structure surrounding the eye Parietal bones Two Forms most of the top of the head and part of the sides of the head.

8 Bones of the Cranium Temporal Bone Two On side of head close to ears Several important bone markings are found in the temporal bones: Auditory meatus – opening of ear Zygomatic process – forms part of cheekbone Styloid process – sharp projection used for attachment of muscles with tongue and larynx

8 Bones of the Cranium Occipital Bone Located at base of the skull Large hole in bone is called the foramen magnum , on either side of the foramen magnum are bony projections known as occipital condyls.

8 Bones of the Cranium Sphenoid bone Butterfly shaped one Forms part of the floor and sides of cranium Also forms part of eye orbits Has a depression along the midline that houses the pituitary gland

8 Bones of the Cranium Ethmoid Bone Irregularly shaped bone that helps form the bony structures of noses.

Facial Bones There are 14 facial bones, most of which are paired

Facial Bones Mandible Lower jaw Anterior portion of the jaw Has two bony processes that articulate with the temporal bones at the temporal mandibular joint, which is a point of attachment for chewing muscles.

Facial Bones Maxilla Upper jaw An extension of the maxilla is the palatine process that makes up the anterior portion of the hard palate Also form part of the nasal cavity and eye orbits

Facial Bones Pallatine Bones Forms the posterior part of the hard palate and the floor of the nasal cavity Failure of the palatine bones to fuse can result in a cleft palate

Facial Bones Zygomatic Bones Cheek bones Form part of the orbits of the eyes

Facial Bones Other Facial Bones Make up the rest of the facial structures Includes vomer, lacrimal bones and nasal bones Sinuses are named based on their location in the skull bone: frontal sinus, ethoidal sinus, sphenoidal sinus and maxillal sinus

How do skull bones fuse? The adult skull forms a unique joint called a suture. Looks like a zipper The major sutures are: Coronal sutures Lamboidal sutures Aquamosal sutures Prevents the movement of cranial bones

How do skull bones fuse together? An infant skull is not fused to allow the movement of the infant through the birth canal. Microcephalia is a condition where the cranium bones fuse too early preventing the brain from growing and developing Symptoms: small head and impaired intellectual capacity Hydrocephalus occurs when there is too much fluid on the bran, causing the skull to enlarge.

Bones of the Neck and Ear Hyoid Bone U-shaped bone located in the neck Anchors tongue and allows swallowing Only bone that does not articulate with another bone Bones of the Middle Ear Contains 3 small bones called ossicles

Vertebral Column Extends from the skull to the pelvis Small stacked bones Between each vertebra is a cartilaginous disc that acts as a shock absorber. Vertebrae have four major functions: Support structures of head and thorax Allow attachment to pelvic girdle Encase

Vertebral Column Named according to location 7 cervical vertebrae (C1-C7)- located in neck region 12 thoracic vertebrae (T1-T12) – located in chest region 5 lumbar vertebrae (L1- L5) – located in lower back 5 saccral vertebrae fuse to form the sacrum 4-5 coccygeal vertebrae fuse to form the tailbone

Two Special Vertebrae Atlas (C1) Have depressions that fit the projections of the occipital bone of the skull. Supports the skull and allows you to nod “yes”. Axis (C2) Has a projection that fits into the atlas and acts as a pivot for the atlas. Allows head to nod “no”.

Appendicular Skeleton Composed of bones of the shoulder girdle, upper limbs, pelvic girdle and lower limbs. Shoulder Girdle Composed of two bones: clavicle and scapula Should supports arm and serves as a place of attachement for muscles Designed for greater flexibility

Shoulder Girdle Clavicle (AKA collarbone) Long bone that articulates with both the sternum and scapula. Most easily broken bone in the body Scapula Articulates with clavicle and serves as a point of attachment for arm and chest muscles. Glenoid cavity allows the head of the humerus to fit, so you can rotate your shoulder.

Thoracic Cage Surrounds and protects the lungs, heart and large blood vessels Plays a role in breathing Supports the bones of the shoulder Composed of sternum, ribs and thoracic vertebrae Sternum located in the centre of the chest

Thoracic Cage There are 12 pairs of ribs attached posterior to the thoracic cage Top 7 ribs are attached directly to the sternum by costal cartilage and are known as true ribs Next five ribs attach indirectly to the sternum and are known as false ribs Bottom two ribs are known as floating ribs because they do not attach to sternum and can be easily broken

Arms Upper arm – humerus Forearm – radius and ulna Hand – carpels, metacarpels and phalanges

Humerus Long bone of arms Head of bone fits into glenoid cavity of scapula, allows shoulder t rotate Opposite end articulate with bones of forearm

Radius Located on thumb-side when palm is facing forward Head of radius articulates with the ulna and humerus

Ulna Located on little finger side of the forearm Articulates with humerus, radius and bones of the writes

Hand The and is composed of the wrist, palm and fingers 8 bones called carpels are tightly arranged around ligaments 5 metacarpels form the palm of the hand 14 bones – phalanges Each digit has three bones, thumb has two bones