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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Axial Skeleton Eighty bones segregated into three regions Skull Vertebral column Bony thorax Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Bones of the Axial Skeleton Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.1 The Skull The skull, the body’s most complex bony structure, is formed by the cranium and facial bones (22 in all) Cranium Made up of cranial bones protects the brain and is the site of attachment for head and neck muscles Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Facial bones Facial bones Form the framework of the face Contain cavities for special sense organs (smell, sight, taste, hearing) Provide openings for the passage of air and food Secure the teeth Anchor the facial muscles of expression Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Facial bones Facial bones Form the framework of the face Contain cavities for special sense organs (smell, sight, taste, hearing) Provide openings for the passage of air and food Secure the teeth Anchor the facial muscles of expression Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Overview of Skull Geography The cranium can be divided into a vault and a base The cranial vault forms the superior, lateral, and posterior aspects of the skull (and forehead) The cranial base (floor) forms the skull’s inferior aspect Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Overview of Skull Geography The internal bony ridges divide the base into 3 steps (or fossae): Anterior cranial fossae Middle cranial fossae Posterior cranial fossae The brain sits within these 3 cranial fossae Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Temporal Bones: Mastoid Region The mastoid region contains the large mastoid process which anchors some neck muscles Feel it right behind your ear…go ahead, feel it! The stylomastoid foramen allows cranial nerve VII (the facial nerve) to leave the skull Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Temporal Bones: Petrous Region The petrous region contributes to the cranial base It lies between the occipital bone and the sphenoid bone Together w/ the sphenoid bone they form the middle cranial fossa which supports the temporal lobes of the brain This region also houses the middle & internal ear cavities Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Temporal Bones: Petrous Region Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sphenoid Bone Butterfly-shaped bone that spans the width of the middle cranial fossa The Keystone Bone: Forms the central wedge that articulates with all other cranial bones Consists of a central body, greater wings, lesser wings, and pterygoid processes Contains the sphenoid sinuses Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sphenoid Bone The superior surface bears the sella turcica which bears the hypophyseal fossa that forms the enclosure for the pituitary gland (hypophysis) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sphenoid Bone The greater wings project laterally from the body and form: Middle cranial fossa Dorsal walls of the orbits External wall of the skull (medial to the zygomatic arch) The lesser wings form: Part of the floor of the anterior cranial fossa Part of the medial walls of the orbits Terminate medially at the anterior clinoid process (an anchoring site for the brain) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sphenoid Bone The pterygoid processes project inferior from the body. Function to anchor the pterygoid muscles that we use when we chew (see arrows) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Ethmoid Bone Deepest of the skull bones; lies between the sphenoid and nasal bones Forms most of the bony area between the nasal cavity and the orbits The cribiform plates (seen from above) form the roof of the nasal cavities and the floor of the anterior cranial fossa The olfactory foramina: allow the olfactory nerves to pass Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Ethmoid Bone Crista galli: (triangular process) Attachment site for the dura mater (the outermost covering of the brain) Perpendicular plate Projects inferiorly in the median plane Forms the superior part of the nasal septum (which divides the nasal cavity right and left) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Ethmoid Bone Right & left lateral masses: Superior/middle nasal conchae (turbinates) Riddled w/ ethmoid sinuses (acts as sieve) Protrude into the nasal cavity. Circulate air w/i nasal passages Orbital plate: Located on the lateral surfaces of the lateral masses Contribute to the medial walls of the orbits Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Facial Bones 14 bones (6 paired sets) of which only the mandible and vomer are unpaired Most sources include: Maxillae Zygomatics Nasals Lacrimals Palatines inferior nasal conchae Vomer Mandible Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mandible and Its Markings The body forms the chin The rami meet the body posteriorly at the mandibular angle The mandibular notch separates the coronoid and condyle processes or the rami The coronoid process (anterior) is the insertion point for the large temporalis muscle that elevates the lower jaw during chewing Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mandible and Its Markings The mandibular condyle (posterior) articulates with the mandibular fossa of the temporal bone forming the temporomandibular joint Mandibular body anchors the teeth Alveolar margin: the superior border of the body contains the sockets w/i which the teeth are embedded Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Maxillary Bones (maxillae) Medially fused bones that make up the upper jaw and the central portion of the facial skeleton Facial keystone bones that articulate with all other facial bones except the mandible Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Zygomatic Bones Irregularly shaped bones (cheekbones) Articulate with the zygomatic processes of the temporal bones posteriorly, the zygomatic process of the frontal bone superiorly, and the zygomatic process of the maxillae anteriorly Form part of the inferolateral margins of the orbits Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Other Facial Bones Nasal bones Thin medially fused bones that form the bridge of the nose Articulate with the frontal bone superiorly, the maxillary bones laterally, and the perpendicular plate of the ethmoid bone posteriorly Cartilages form the “skeleton” of the external nose inferiorly Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Other Facial Bones Lacrimal bones: Contribute to the medial walls of the orbit Smallest and most fragile of the facial bones Articulate with the frontal bone superiorly, ethmoid bone posteriorly, and the maxillae anteriorly Contains a deep groove (lacrimal fossa) that houses the lacrimal sac that is part of the passage that allows tears to drain from the eye to the nasal cavity Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Other Facial Bones Palatine bones: Fashioned from 2 bony plates Horizontal: complete posterior portion of the hard palate Perpendicular: forms the posterior walls of the nasal cavity and the small parts of the orbits 3 articulating processes: Pyramidal Sphenoidal orbital Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Other Facial Bones Vomer – plow-shaped bone that forms part of the nasal septum Inferior nasal conchae – paired, curved bones in the nasal cavity that form part of the lateral walls of the nasal cavity Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Orbits Bony cavities in which the eyes are firmly encased and cushioned by fatty tissue Formed by parts of seven bones: Frontal Sphenoid Zygomatic Maxilla Palatine Lacrimal ethmoid Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Orbits Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.9b Nasal Cavity Constructed of bone and hyaline cartilage Roof – formed by the cribriform plate of the ethmoid Lateral walls – formed by the superior and middle conchae of the ethmoid, the perpendicular plate of the palatine, and the inferior nasal conchae Floor – formed by palatine process of the maxillae and palatine bone Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Nasal Cavity Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.10b Nasal Cavity Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.10a Paranasal Sinuses Mucosa-lined, air-filled sacs found in five skull bones: Frontal Sphenoid Ethmoid Paired maxillary bones Air enters the paranasal sinuses from the nasal cavity and mucus drains into the nasal cavity from the sinuses Lighten the skull and enhance the resonance of the voice Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Paranasal Sinuses Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.11 Hyoid Bone Lies just inferior to the mandible in the anterior neck Only bone of the body that does not articulate directly with another bone Anchored by stylohyoid ligaments to the styloid processes of the temporal bones Acts as a movable base for the tongue Body & horns (cornu) are points of muscle attachment that raise and lower the larynx during swallowing and speech. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Vertebral Column Formed from 26 irregular bones (vertebrae) connected in such a way that a flexible curved structure results Axial support of the trunk (skull to pelvis) Surrounds / protects the spinal cord Attachment point for the ribs and muscles Fetus: 33 bones, 9 fused to form 2 composite bones: the coccyx and sacrum Cervical vertebrae – 7 bones of the neck Thoracic vertebrae – 12 bones of the torso Lumbar vertebrae – 5 bones of the lower back Sacrum – bone inferior to the lumbar vertebrae that articulates with the hip bones Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Vertebral Column Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.13 Vertebral Column: Curvatures Posteriorly concave curvatures – cervical and lumbar Posteriorly convex curvatures – thoracic and sacral Abnormal spine curvatures include scoliosis (abnormal lateral curve), kyphosis (hunchback), and lordosis (swayback) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Vertebral Column: Ligaments Major supporting ligaments are: Anterior and Posterior Continuous bands down the front and back of the spine from the cervical vertebrae to the sacrum Anterior longitudinal ligaments: Posterior longitudinal ligaments Broad, resists bending backwards attached to both the vertebrae and the discs Not as broad, resists bending forward, attaches only to discs Ligamentum flavum: Connect vertebra above and below. Elastic consistency and strong Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Vertebral Column: Intervertebral Discs Cushion-like pad composed of two parts Nucleus pulposus – inner gelatinous nucleus that gives the disc its elasticity and compressibility Annulus fibrosus – surrounds the nucleus pulposus with a collar composed of collagen fibers (superficially) and fibrocartilage (internally) Limits the expansion of the nucleus pulposus when the spine is compressed Binds successive vertebrae together Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Bony Thorax (Thoracic Cage) Functions Forms a protective cage around the heart, lungs, and great blood vessels Supports the shoulder girdles and upper limbs Provides attachment for many neck, back, chest, and shoulder muscles Uses intercostal muscles to lift and depress the thorax during breathing Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Sternum (Breastbone) Anatomical landmarks: CAN PALPATE ALL OF ‘EM jugular (suprasternal) notch: Superior border of the maubrium In line with T2-T3 intersection Point where left common carotid artery splits from the aorta sternal angle: Hinge Allows sternal body to move forward upon inhalation Inline with T4-T5 intersection Inline with 2nd pair of ribs xiphisternal joint: Lies opposite T9 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Gimme some of them Ribs! There are twelve pair of ribs forming the flaring sides of the thoracic cage All ribs attach posteriorly to the thoracic vertebrae The superior 7 pair (true, or vertebrosternal ribs) attach directly to the sternum via costal cartilages Ribs 8-10 (false, or vertebrochondral ribs) attach indirectly to the sternum via costal cartilage (or not at all) Costal margin: inferior margin of the rib cage Each joins the costal cartilage immediately above it Formed by costal cartilage of ribs 7-10 Ribs 11-12 (floating, or vertebral ribs) have no anterior attachment Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Appendicular Skeleton The appendicular skeleton is made up of the bones of the limbs and their girdles Pectoral girdles attach the upper limbs to the body trunk Pelvic girdle secures the lower limbs Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Pectoral Girdles (Shoulder Girdles) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.22a Pectoral Girdles (Shoulder Girdles) The pectoral girdles consist of: Clavicle anteriorly & scapula posteriorly Anteriorly, the medial end of each clavicle joins the sternum The distal ends of the clavicle meet the scapulae laterally The scapulae are attached to the thorax & vertebral column by muscles The clavicle and scapula are light weight and very mobile However, there is a price to pay…greater mobility means poor stability often resulted in a painful dislocated shoulder Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Clavicles (Collarbones) The acromial (lateral) end articulates with the scapula, and the sternal (medial) end articulates with the sternum The superior surface is smooth while the inferior surface is ridged and grooved by ligaments Provide attachment points for numerous muscles, and act as braces to hold the scapulae and arms out laterally away from the body The clavicles transmit compression force from the upper limbs to the axial skeleton Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Scapulae (Shoulder Blades) The posterior surface of the scapula has a prominent spine (palpate) The spine terminates laterally at the acromion process The acromion articulates with the acromial end of the clavicle forming the acromioclavicular joint The coracoid process anchors the biceps The suprascapoid notch allows a passage way for nerves The infraspinous, supraspinous, subscapular fossae are sites for muscle attachment (later this semester) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings