Chapter 7 The Skeletal System The Axial Skeleton

Chapter 7 The Skeletal System: The Axial Skeleton l 80 bones l lie alongitudinal axis l skull, hyoid, vertebrae, ribs, sternum, ear ossicles l Appendicular l 126 Skeleton bones l upper & lower limbs 1

Types of Bones l 5 basic types of bones: long = compact l short = spongy except surface l flat = plates of compact enclosing spongy l irregular = variable l sesamoid = develop in tendons or ligaments (patella) l l Sutural bones = in joint between skull bones 2

Bone Surface Markings Surface features-- rough area, groove, openings, process l Specific functions l passageway for blood vessels and nerves l joint formation l muscle attachment & contraction l 3

Bone Surface Markings from Table 7. 2 l l l l l Foramen = opening Fossa = shallow depression Sulcus = groove Meatus = tubelike passageway or canal Condyle = large, round protuberance Facet = smooth flat articular surface Trochanter = very large projection Tuberosity = large, rounded, roughened projection Learning the terms found in this Table will 4

The Skull l 8 Cranial bones protect brain & house ear ossicles l muscle attachment for jaw, neck & facial muscles l l 14 Facial bones protect delicate sense organs -- smell, taste, vision l support entrances to digestive and respiratory l 5

The 8 Cranial Bones Frontal Parietal (2) Temporal (2) Occipital Sphenoid Ethmoid 6

Frontal Bone Forehead, roof of orbits, & anterior cranial floor l Frontal suture gone by age 6 (metopic suture) l Supraorbital margin and frontal sinus l 7

Parietal & Temporal Bones l Parietal l l sides & roof of cranial cavity Temporal temporal squama l zygomatic process forms part of arch l external auditory meatus l mastoid process l stylomastoid foramen(VII) l mandibular fossa (TMJ) l petrous portion (VIII) l 8

Temporal and Occipital bones l Temporal carotid foramen (carotid artery) l jugular foramen (jugular vein) l l Occipital foramen magnum l occipital condyles l external occipital protuberance attachment for ligamentum nuchae l superior & inferior nuchal lines l 9

Sphenoid bone Base of skull l Pterygoid processes are attachment sites for jaw muscles l 10

Sphenoid in Anterior View Body is a cubelike portion holding sphenoid sinuses l Greater and lesser wings l Pterygoid processes l 11

Sphenoid from Superior View Lesser wing & greater wing l Sella turcica holds pituitary gland l Optic foramen l 12

Ethmoid Bone l l l Cranial floor, lateral nasal walls & nasal septum Cribriform plate & olfactory foramina Crista galli for attachment of membranes cover the brain 13

Ethmoid bone Lateral masses contain ethmoid sinuses l Perpendicular plate is upper part of nasal septum l Superior & middle nasal concha or turbinates l l filters & warms air 14

14 Facial Bones Nasal (2) Mandible (1) Inferior nasal conchae (2) Maxillae (2) Lacrimal (2) Zygomatic (2) Palatine (2) Vomer (1) 15

Maxillary bones l l Floor of orbit, floor of nasal cavity or hard palate Maxillary sinus Alveolar processes hold upper teeth Cleft palate is lack of union of maxillary bones 16

Zygomatic Bones l l l Cheekbones Lateral wall of orbit along with sphenoid Part of zygomatic arch along with part of temporal 17

Lacrimal and Inferior Nasal Conchae l Lacrimal bones l l l part of medial wall of orbit lacrimal fossa houses lacrimal sac Inferior Nasal Conchae Inferior nasal concha or turbinate (not part of ethmoid) 18

Palatine & Vomer l Palatine l l L-shaped : one end is back part of hard palate, other end is part of orbit (see previous picture) Vomer l posterior part of nasal septum 19

Mandible l l Body, angle & rami Condylar & coronoid processes Alveolar processes for lower teeth Mandibular & mental foramen 20

Sutures l Lambdoid suture unites parietal and occipital l Sagittal suture unites 2 parietal bones 21

Sutures l Coronal bones suture unites frontal and both parietal 22

Paranasal Sinuses Paired cavities in ethmoid, sphenoid, frontal and maxillary l Lined with mucous membranes and open into nasal cavity l Resonating chambers for voice, lighten the skull l 23

Fontanels of the Skull at Birth. l Dense connective tissue membrane-filled spaces (soft spots) l Unossified at birth but close early in a child's life. l Fetal skull passes through the birth canal. l Rapid growth of the brain during infancy 24

Bones of the Orbit l l l Roof is frontal and sphenoid Lateral wall is zygomatic and sphenoid Floor is maxilla, zygomatic and sphenoid Medial wall is maxilla, lacrimal, ethmoid and sphenoid Orbital fissures and optic foramen 25

Nasal Septum Divides nasal cavity into left and right sides l Formed by vomer, perpendicular plate of ethmoid and septal cartilage l Deviated septum does not line in the midline l l developmental abnormality or trauma 26

Hyoid Bone l U-shaped single bone l Articulates with no other bone of the body l Suspended by ligament and muscle from skull l Supports the tongue & provides attachment for tongue, neck and pharyngeal muscles 27

Vertebral Column l Backbone or spine built of 26 vertebrae l Five vertebral regions l cervical vertebrae (7) in the neck l thoracic vertebrae ( 12 ) in the thorax l lumbar vertebrae ( 5 ) in the low back region l sacrum (5, fused) l coccyx (4, fused) 28

Intervertebral Discs Between adjacent vertebrae absorbs vertical shock l Permit various movements of the vertebral column l 29

Normal Curves of the Vertebral Column l Primary curves l l thoracic and sacral are formed during fetal development Secondary curves l l cervical if formed when infant raises head at 4 months lumbar forms when infant sits up & begins to walk at 1 30 year

Typical Vertebrae l Body l weight bearing l Vertebral arch l pedicles l laminae l Vertebral foramen l Seven processes l 2 transverse l 1 spinous l 4 articular l Vertebral 31

Intervertebral Foramen & Spinal Canal Spinal canal is all vertebral foramen together l Intervertebral foramen are 2 vertebral notches together l 32

Typical Cervical Vertebrae (C 3 C 7) Smaller bodies l Larger spinal canal l Transverse processes l shorter l transverse foramen for vertebral artery l l 1 st and 2 nd cervical vertebrae are unique l atlas & axis 33

Atlas & Axis (C 1 -C 2) l Atlas -- ring of bone, superior facets for occipital condyles l l nodding movement at atlanto-occipital joint signifies “yes” Axis -- dens or odontoid process is body of atlas l pivotal movement at atlanto-axial joint signifies “no” 34

Thoracic Vertebrae (T 1 -T 12) l l Larger and stronger bodies Longer transverse & spinous processes Facets or demifacets on body for head of rib Facets on transverse processes (T 1 -T 10) for tubercle of rib 35

Lumbar Vertebrae Strongest & largest l Short thick spinous & transverse processes l l back musculature 36

Sacrum l Union of 5 vertebrae (S 1 - S 5) by age 30 l l median sacral crest was spinous processes sacral ala is fused transverse processes Sacral canal ends at sacral hiatus Auricular surface & sacral tuberosity of SI joint 37

Coccyx l l Union of 4 vertebrae (Co 1 - Co 4) by age 30 Caudal or epidural anesthesia during delivery into sacral hiatus anesthetize sacral & coccygeal nerves l sacral and coccygeal cornu are important l 38

Thorax l Bony cage flattened from front to back l Sternum (breastbone) l Ribs l 1 -7 are true ribs (vertebrosternal) l 8 -12 are false ribs (vertebrochondral) l 11 -12 are floating l Costal cartilages l Bodies of the thoracic vertebrae. 39

Sternum l Manubrium 1 st & 2 nd ribs l clavicular notch l l Body l l costal cartilages of 210 ribs Xiphoid ossifies by 40 l CPR position l abdominal 40 mm. l l Sternal

Ribs Fracture at site of greatest curvature. Increase in length from ribs 1 -7, thereafter decreasing l Head and tubercle articulate with facets l Body with costal groove containing nerve & blood vessels l 41

Rib Articulation Tubercle articulates with transverse process l Head articulates with vertebral bodies l 42

Herniated (Slipped) Disc l l Protrusion of the nucleus pulposus Most commonly in lumbar region Pressure on spinal nerves causes pain Surgical removal of disc after laminectomy 43

Clinical Problems l Abnornal curves of the spine. l scoliosis (lateral bending of the column) l kyphosis (exaggerated thoracic curve) l lordosis (exaggerated lumbar curve) l Spina bifida is a congenital defect l failure of the vertebral laminae to unite l nervous tissue is unprotected l paralysis 44