A&P1 - Ch. 12 Outline - Summary Anatomy and Physiology PDF

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CHAPTE R 12 Skeleton  The adult skeleton is composed of 206 named bones.  Variations can occur as a result of anomalies, such as extra ribs, or from failure of certain small bones to fuse together in the course of development. Division of the Skeleton  Two main divisions: o The Axial skeleton  74 bones that form the upright axis of the body and 6 tiny middle ear bones o The Appendicular skeleton  126 bones  More than half again as many as in the axial skeleton.  These bones form appendages to the axial skeleton:  The shoulder girls  Arms  Wrists  Hands  Hip girdles  Legs  Ankles  Feet Skull  28 irregular shaped bones form the skull.  Two major divisions: o The Cranium (or brain)  Formed by 8 bones  Frontal o Help shape the face, but not counted in the facial bones  2 Parietal  2 Temporal  Occipital  Sphenoid  Ethmoid o Help shape the face, but not counted in the facial bones

CHAPTE R 12  All are unpaired except the Parietal and Temporal o The Face  Formed by 14 bones  2 Maxillae  2 Zygomatic (marlar)  2 Nasal  Mandible  2 Lacrimal  2 Palatine  2 Inferior Nasal Conchae (turbinates)  Vomer  All are paired except the mandible and the vomer Cranial Bones  Frontal bone forms the forehead and the anterior part of the calvaria, or the top of the cranium. o Contains the mucosa-lined, air-filled spaces, or sinuses (frontal sinuses).  The sinuses are often called paranasal sinuses because they have narrow channels that open into the nasal cavity.  Located in the frontal, sphenoid, ethmoid, and maxillae o A portion of the frontal bone forms the upper part of the orbits. o It unites with the two parietal bones posteriorly in an immovable joint, or suture- the coronal suture.  Two Parietal bones give shape to the bulging topside of the cranium. o They form immovable joints with several bones:  The lambdoid suture with the occipital bone  The squamous suture with the temporal bones and part of the sphenoid  The coronal suture with the frontal bone.  The lower part of the cranium and parts of its floor are fashioned from two Temporal bones. o The contain the middle and inner ear structures, and the mastoid sinuses  Notably because of the occurrence of mastoiditis, an inflammation of the mucous lining of these spaces.  The Occipital bone creates the framework of the lower, posterior part of the skull.

CHAPTE R 12 o It forms immovable joints with three other cranial bones:  Parietal  Temporal  Sphenoid o It forms movable joints with the first cervical vertebra  The Sphenoid bone shape resembles a bat with its wings outstretched and legs extended down and back. o It is located in the central portion of the cranial floor. o It serves as the keystone in the architecture of the cranium. o It anchors the parietal, frontal, occipital, and ethmoid bones. o It forms part of the lateral wall of the cranium and part of the floor of each orbit. o Contains a large amount of mucous-lined, air-filled spaces called the sphenoid sinuses.  The Ethmoid bone is a complex, irregular bone. o It lies anterior to the sphenoid, but posterior to the nasal bones, o It helps:  Fashion the anterior part of the cranial floor  The medial walls of the orbits  The upper parts of the nasal septum  The sidewalls of the nasal cavity  Part of the nasal roof perforated by small foramina, which olfactory nerve branches reach the brain.  Called the cribriform plate o The lateral masses of the ethmoid bones are honeycombed with sinus spaces called ethmoid air cells. Facial bones  Two maxilla serve as the keystone in the architecture of the face. o It articulates with:  The other maxilla  A Nasal  A Zygomatic  An inferior conchae  A palatine bone o Of all the facial bones, the mandible is the only one that does not articulate with the maxilla o Forms:

CHAPTE R 12  Part of the floor of the orbits  Part of the roof of the mouth  Part of the floor and sidewalls of the nose o Each contains a mucosa-lines space known as the maxillary sinuses  It is the largest of the paranasal sinuses  Sinuses connected by channels to the nasal cavity.  The lower jaw consists of a single bone known as the mandible. o It is the largest and strongest bone of the face o It articulates with:  The temporal bone in the only moveable joint of the skull  The cheek is shaped by the zygomatic bone or marlar bone. o The zygomatic:  Forms the outer margin of the orbit  With the zygomatic process of the temporal bone, it makes up the zygomatic arch o It articulates with four other facial bones:  Maxillary  Temporal  Frontal  Sphenoid  The shape of the nose is given by two nasal bones o They form the upper part of the bridge of the nose, and by the septal cartilage, which forms the lower part. o The nasal bones enter into several articulations:  Perpendicular plate of the ethmoid bone  Cartilaginous part of the nasal septum  The frontal bone  The maxillae  Each other o A paper- thin bone, shaped and sized about like a fingernail, lies juts posterior and lateral to each nasal bone. o It helps form the sidewall of the nasal cavity and the medial wall of the orbit. o It contains grooves for the nasolacrimal (tear) duct, this bone is called the lacrimal bone.  It joins the maxilla, frontal bone, and ethmoid bone.

CHAPTE R 12  Two palatine bones join to each other in the midline like two L’s facing each other. o The horizontal portions form the posterior part of the hard plate. o The vertical portions form the lateral walls of the posterior part of the nasal cavity. o The tip of the vertical portion is the orbital process, which forms part of the eye orbit. o They articulate with:  The maxilla  The sphenoid bone  Two inferior nasal conchae o Each is scroll-shaped and forms a kind of ledge projecting into the nasal cavity from its lateral wall. o Each nasal cavity has three such ledges:  Superior conchae  Projections of the ethmoid bone  Form the upper and middle ledges  Middle conchae  Projections of the ethmoid bone  Form the upper and middle ledges  Inferior conchae (separate bone)  Forms the lower ledge  Forms immovable joints with the ethmoid, lacrimal, maxilla, and palatine bones o They are covered in mucous and divide each nasal cavity into three narrow, irregular channels, the nasal meatus.  The vomer bone completes the septum posteriorly. o It forms immoveable joints with four bones:  Ethmoid  Sphenoid  Palatine  Maxillae Eye Orbits  Right and left orbital cavities contain the eye, associated muscles, lacrimal apparatus, and important blood vessels and nerves.  Separated by a very thin and fragile orbital wall from the cranial cavity, nose, paranasal sinuses, and mouth.

CHAPTE R 12 Fetal Skull  Placement of the cranial bones in the fetal skull allows it to change its shape during the birth process.  Fontanels are the best known of the unique feature of the infant skull.  Without the fontanels, molding of the head shape as the baby passes through the birth canal could result in a fracture of one or more cranial bones. o They also allow brain growth without causing damaging increases if intracranial pressure.  When fontanels close, they fuse together to form sutures in an adult skull. Hyoid Bone  A single bone in the neck that is a part of the axial skeleton.  U shaped  Can be found just above the larynx and below the mandible where it is suspended from the styloid process of the temporal bone.  Several muscles attach to the hyoid bone. o Extrinsic tongue muscles o Certain muscles of the floor of the mouth  The only bone in the body that articulates with no other bones. Vertebral Column  Also known as the spinal column  It is flexible rather than a rigid column because it is segmented.  Consists of 24 vertebrae plus the sacrum and coccyx  Joints between the vertebrae permit forward, backward, and sideways movement of the column.  There are 7 cervical vertebrae  There are 12 thoracic vertebrae  There are 5 lumbar vertebrae  In an adult, the sacrum is a single bone that has formed the fusion of five separate vertebrae and the coccyx is a single bone that has formed from the fusion of four or five vertebrae.  All vertebrae (except the first cervical vertebrae) have: o A flat, rounded body anteriorly and centrally, plus a sharp or blunt spinous process projecting inferiorly in the posterior midline o Two transverse processes projecting laterally.  All but the sacrum and coccyx have a central opening, a vertebrae foramen.  The vertebral column, as a whole, articulates with:

CHAPTE R 12 o Head o Ribs o Iliac bones  The vertebral column is curved to maintain balance in an upright position.  If individual vertebrae cannot bear the weight put on them, compression fractures may occur. o These may cause the vertebrae to partially collapse and this affect the spinal curvature and overall stature. Thorax Sternum  The medial part of the anterior chest wall is supported by the sternum.  A dagger-shaped bone consisting of three parts: o Upper handle  Manubrium  Articulates with the clavicle, the first rib o Middle blade part  The body  Articulate with the next 9 ribs after the first, either directly or indirectly, by means of the costal cartilage. o A blunt cartilaginous lower tip o The xiphoid process. o Ossifies as an adult Ribs  12 pairs of ribs, the vertebral column, and the sternum form most of the bony cage known as the thoracic cage, or thorax.  Each rib articulates with: o The body and transverse process of its corresponding thoracic vertebrae.  Th head of the rib articulates with the body of the corresponding thoracic vertebrae  The tubercle of each rib articulates with the vertebrae’s transverse process  The 2nd through 9th ribs articulate with the body of the vertebrae above.  Each rib curves outward, then forward and downward. o A mechanical fact important for breathing.  Anteriorly, each rib of the first 7 pairs joins a costal cartilage that attaches to the sternum. o These ribs are called true ribs

CHAPTE R 12  The remaining 5 pairs are called false ribs. o They do not attach directly to the sternum o Instead, each costal cartilage of pairs 8,9, and 10 attaches to the costal cartilage of the rib above it; indirectly attaching it to the sternum.  The last 2 pairs of ribs are designated to floating ribs o They do not attach even indirectly to the sternum....