Axial Skeleton - Ch 07

Axial Skeleton  Structures of Bones Articulations - contacts with other bones Marks -areas of muscle and ligament attachment Foraminae - openings for nerves and blood vessels Axial Skeleton - longitudinal axis Supports and protects o...

Axial Skeleton  Structures of Bones Articulations - contacts with other bones Marks -areas of muscle and ligament attachment Foraminae - openings for nerves and blood vessels Axial Skeleton - longitudinal axis Supports and protects organs in body cavities Attaches to muscles of: – head, neck, and trunk – respiration – appendicular skeleton  Bones of the Axial Skull: Skeleton - 80 The thoracic cage: – 8 cranial bones – 24 ribs – 14 facial bones – the sternum Bones associated with the skull: – 6 auditory ossicles – the hyoid bone The vertebral column: – 24 vertebrae – the sacrum – the coccyx  protects: Skull Has 22 bones: – the brain 8 cranial bones: – entrances to respiratory form the braincase or system cranium – entrance to digestive 14 facial bones: system protect and support entrances to digestive and respiratory tracts  Cranial bones – Enclose the cranial cavity – contains the brain and its fluids, blood vessels, nerves, membranes Facial Bones – Superficial facial bones for muscle attachment Maxillary Lacrimal Nasal Zygomatic Mandible – Deep facial bones separate the oral and nasal cavities & form the nasal septum Palatine bones Inferior nasal conchae The 4 Major Sutures (immovable joints of the skull) 1. Lambdoid suture- separates occipital from parietal bones 2. Coronal suture- attaches frontal bone to parietal bones (calvaria consists of occipital, parietal, and frontal bones) 3. Sagittal suture- between the parietal bones lambdoid suture to coronal suture 4. Squamous suture- form boundaries  Skull: Cranial Bones - 8 Occipital Bone (1)- Forms posterior/inferior surfaces of cranium Marks - Occipital condyles - articulate with neck Foramina - Foramen magnum- connects cranial and spinal cavities Parietal Bones (2) - forms part of the superior and lateral surfaces of the cran  Frontal Bone (1) - Forms anterior cranium and upper eye sockets; contains frontal sinuses Marks – Frontal squama (forehead) Glabella Supraorbital notch Temporal Bones (2)- Part of lateral walls and zygomatic arches, surround and protect inner ear, attach muscles of jaws and head Marks Mandibular fossa - articulates with the mandible Styloid process - to attach tendons and ligaments of the hyoid, tongue and pharynx Mastoid Process External Acoustic Meatus  Sphenoid (1)- Part of the floor of the cranium, unites cranial and facial bones, strengthens sides of the skull – Marks Greater Wing Lesser Wing Sella Turcica Hypophyseal Fossa Ethmoid (1) - Forms anteromedial floor of the cranium, roof of the nasal cavity, part of the nasal septum and medial orbital wall – Marks Crista Galli Cribiform Plate Nasal conchae  Skull: Facial Bones - 14 Maxillary (2) – AKA maxilla, support upper teeth, form inferior orbital rim, form lateral margins of external nares, form upper jaw and hard palate, contain maxillary sinuses (largest sinuses) Palatine Bones (2) - Form the posterior portion of the hard palate, Contribute to the floors of the orbits  Nasal Bones (2) - Support the bridge of the nose, connect to cartilages of the distal part of the nose (external nares) Vomer (1) - Forms the inferior portion of the bony nasal septum Inferior Nasal Conchae (2) - create air turbulence in the nasal cavity, increase the epithelial surface area, warm and humidify inhaled air Zygomatic Bones (2) - contribute to the rim and lateral wall of the orbit, form part of the zygomatic arch Lacrimal Bones (2) - form part of the medial wall of the orbit  Mandible (1) - the lower jaw – Marks Body of the mandible - horizontal portion Ramus - ascending from the mandibular angle on either side – Parts of Ramus » Condylar process: » Coronoid process: » Mandibular notch:  Hyoid Bone - supports the larynx, attaches muscles of the larynx, pharynx, and tongue – Articulations The only bone that does not articulate with any other bones – Marks Body of the hyoid Greater horns (greater cornua) Lesser horns (lesser cornua)  Infant Skull Fusion is incomplete at birth Fontanels – Are areas of fibrous connective tissue (soft spots) – Cover unfused sutures in the infant skull – Allow the skull to flex during birth – Anterior fontanel: frontal, sagittal, and coronal sutures – Occipital fontanel: lambdoid and sagittal sutures  Vertebral Column Spine or vertebral column – protects the spinal cord – supports the head and body 26 bones - 24 vertebrae, the sacrum, and coccyx Regions – Cervical (C) – 7 – Thoracic (T) – 12 – Lumbar (L) – 5 – Sacral (S) – Coccygeal (Co)  Curvatures – Cervical curve – Thoracic curve – Lumbar curve – Sacral curve Primary Curves – Thoracic and sacral curves - present during fetal development – aka accommodation curves - accommodate internal organs Secondary Curves – Lumbar and cervical curves- appear after birth – aka compensation curves - shift body weight for upright posture  Vertebrae 3 Parts of a Vertebra – vertebral body (centrum) - transfers weight along the spine – vertebral arch - posterior margin of vertebral foramen – articular processes - lateral projections  Intervertebral Discs – pads of fibrocartilage – separate the vertebral bodies – absorb shocks Vertebrae are numbered by region, from top to bottom – C1 articulates with skull, L5 with sacrum Vertebrae of each region have characteristics determined by functions  Cervical - C1–C7 – small body (support only head) – large vertebral foramen (largest part of spinal cord) – tip of each spinous process is notched (bifid) (except C1 – atlas) – Atlas (C1): articulates with occipital condyles of skull has no body or spinous process – Axis (C2): supports the atlas has heavy spinous process – Axis and atlas bodies fuse during development to form the dens – Whiplash – forceful, rapid back and forth motion of the cervical spine (sprain)  Thoracic - T1–T12 – heart-shaped bodies, larger than C1–C7 – smaller vertebral foramen than C1– C7 – long, slender, knifelike spinous processes – Dorsolateral surfaces of body have costal facets-which articulate with heads of ribs  Lumbar - L1–L5 – largest vertebrae – oval-shaped bodies – thicker bodies than T1–T12 – triangular vertebral foramen – Transverse processes- slender – Spinous process-short, heavy  Sacrum and Coccyx Sacrum (1) – is curved – protects reproductive, urinary, and digestive organs – attaches-the axial skeleton to pelvic girdle of appendicular skeleton Adult sacrum 5 fused sacral vertebrae fuses between puberty & ages 25–30 leaving transverse lines  Sacrum Regions Base - the broad superior surface Ala - wings at either side of the base to attach muscles Sacral promontory - at the center of the base Apex - the narrow inferior portion articulates with the coccyx Coccyx (1) – attaches ligaments and a constricting muscle of the anus – mature coccyx-consists of 3 to 5 fused coccygeal vertebrae  Consists of: Thoracic Cage – thoracic vertebrae – ribs – sternum (breastbone) Protects organs of the thoracic cavity-heart, lungs, and thymus Rib Cage - formed of ribs and sternum  Ribs (costae)-12 pairs of long, curved, flat bones extending from the thoracic vertebrae Rib movements (breathing): – affect width and depth of thoracic cage, thus changing its Ribsvolume 1–7 (true ribs) – vertebrosternal ribs; connected to the sternum by costal cartilages Ribs 8–12 (false ribs): – Vertebrochondral ribs (ribs 8–10); merge with cartilage before reaching the sternum (do not attach directly to the sternum) – Floating or vertebral ribs (ribs 11–12): connect only to the vertebrae; have no  Rib Structures Ribs – Head (capitulum) – Tubercle (tuberculum): at the vertebral a small dorsal end of the rib elevationbody (shaft) – Tubercular – Neck the short area between the head and the tubercle  Sternum Flat bone in the midline of the thoracic wall – Manubrium superior portion of sternum broad, triangular shape articulates with collarbones (clavicles) & cartilages of 1st rib pair has a jugular notch between clavicular – Xiphoid process – Sternal body articulations smallest part of the tongue-shaped sternum attaches to the attaches to the manubrium & costal sternal body & cartilages of ribs 2–7 diaphragm and rectus abdominis muscles