7 The Axial Skeleton

7-3 The Facial Bones of the Skull The Mandible Foramina of the mandible Mental foramina For sensory nerves of lips and chin Mandibular foramen Entrance to the mandibular canal For blood vessels and nerves of lower teeth

7-3 The Facial Bones of the Skull The Hyoid Bone Functions of the hyoid bone Supports the larynx Attaches muscles of the larynx, pharynx, and tongue Articulations of the hyoid bone Connects lesser horns to styloid processes of temporal bones

7-3 The Facial Bones of the Skull The Hyoid Bone Marks of the hyoid bone Body of the hyoid Attaches muscles of larynx, tongue, and pharynx

7-3 The Facial Bones of the Skull The Hyoid Bone Marks of the hyoid bone Greater horns (greater cornua) Support larynx Attach muscles of the tongue Lesser horns (lesser cornua) Attach stylohyoid ligaments Support hyoid and larynx

Figure 7-12b The Mandible and Hyoid Bone Articular surface Alveolar process Condylar process Coronoid process Mandibular foramen Mylohyoid line Depression for submandibular salivary gland A medial view of the right mandible 6

Figure 7-12c The Mandible and Hyoid Bone Greater horn Lesser horn Body An anterior view of the hyoid bone 7

7-4 The Orbital and Nasal Complexes The Eye Sockets (Orbits) Frontal bone (roof) Maxilla (floor) Maxillary, lacrimal, and ethmoid bones (orbital rim and medial wall) Sphenoid and palatine bones

Figure 7-13 The Orbital Complex FRONTAL BONE Supra-orbital notch SPHENOID Optic canal ETHMOID Superior orbital fissure LACRIMAL BONE Lacrimal sulcus Inferior orbital fissure Nasolacrimal canal ZYGOMATIC BONE PALATINE BONE Infra-orbital groove Infra-orbital foramen MAXILLA 9

Figure 7-13 The Orbital Complex Supra-orbital notch FRONTAL BONE SPHENOID Optic canal Superior orbital fissure ETHMOID Nasolacrimal canal Inferior orbital fissure Infra-orbital groove ZYGOMATIC BONE MAXILLA Infra-orbital foramen 10

7-4 The Orbital and Nasal Complexes Bones of the Nasal Cavities and Paranasal Sinuses Make Up the Nasal Complex Frontal bone, sphenoid, and ethmoid Superior wall of nasal cavities Maxillae, lacrimal bones, ethmoid, and inferior nasal conchae Lateral walls of nasal cavities Maxillae and nasal bones Bridge of nose

Figure 7-14a The Nasal Complex FRONTAL BONE Frontal sinuses Sphenoidal sinuses ETHMOID NASAL BONE SPHENOID PALATINE BONE (bony palate) Superior Nasal conchae of ethmoid MAXILLA (bony palate) Middle INFERIOR NASAL CONCHA A sagittal section through the skull, with the nasal septum removed to show major features of the wall of the right nasal cavity. The sphenoidal sinuses are visible. 12

Figure 7-14b The Nasal Complex FRONTAL BONE Cranial cavity Frontal sinus Right orbit Ethmoidal air cell Superior nasal concha Perpendicular plate of ethmoid Middle nasal concha Maxillary sinus ZYGOMATIC BONE INFERIOR NASAL CONCHA VOMER MAXILLA (bony palate) Tongue MANDIBLE A frontal section through the ethmoidal air cells and maxillary sinuses, part of the paranasal sinuses. 13

7-4 The Orbital and Nasal Complexes Paranasal Sinuses Air-filled chambers connected to the nasal cavities Lighten skull bones Provide mucous epithelium (flushes nasal cavities)

7-5 Fontanelles The Infant Skull Grows rapidly Is large compared to the body Has many ossification centers

7-5 Fontanelles The Infant Skull Fusion is not complete at birth Two frontal bones Four occipital bones Several sphenoidal and temporal elements

7-5 Fontanelles Fontanelles Are areas of fibrous connective tissue (soft spots) Cover unfused sutures in the infant skull Allow the skull to flex during birth

7-5 Fontanelles Anterior Fontanelle Occipital Fontanelle Frontal, sagittal, and coronal sutures Occipital Fontanelle Lambdoid and sagittal sutures Sphenoidal Fontanelles Squamous and coronal sutures Mastoid Fontanelles Squamous and lambdoid sutures

Figure 7-15a The Skull of an Infant Coronal suture FRONTAL BONE PARIETAL BONE Sphenoidal fontanelle NASAL BONE Squamous suture Lambdoid suture MAXILLA OCCIPITAL BONE SPHENOID MANDIBLE TEMPORAL BONE Mastoid fontanelle Lateral view 19

Figure 7-15b The Skull of an Infant PARIETAL BONE FRONTAL BONE Lambdoid suture Coronal suture Sagittal suture Frontal suture Anterior fontanelle OCCIPITAL BONE FRONTAL BONE PARIETAL BONE Occipital fontanelle Superior view 20

7-6 The Vertebral Column The Vertebral Column (Spine) Protects the spinal cord Supports the head and body 26 bones 24 vertebrae, the sacrum, and the coccyx

Figure 7-16 The Vertebral Column Spinal Curves Vertebral Regions Primary curves develop before birth, and secondary curves after birth. Regions are defined by anatomical characteristics of individual vertebrae. The cervical curve, a secondary curve, develops as the infant learns to balance the weight of the head on the vertebrae of the neck. Cervical (7 vertebrae) The thoracic curve, a primary curve, accommodates the thoracic organs. Thoracic (12 vertebrae) The lumbar curve, a secondary curve, balances the weight of the trunk over the lower limbs; it develops with the ability to stand. Lumbar (5 vertebrae) The sacral curve, a primary curve, accommodates the abdominopelvic organs. Sacral Coccygeal 22

7-6 The Vertebral Column Vertebrae The neck The upper back Seven cervical vertebrae The upper back 12 thoracic vertebrae Each articulates with one or more pair of ribs The lower back Five lumbar vertebrae

7-6 The Vertebral Column The Sacrum and Coccyx The fifth lumbar vertebra articulates with the sacrum The sacrum articulates with the coccyx

7-6 The Vertebral Column Four Spinal Curves Cervical curve Thoracic curve Lumbar curve Sacral curve

7-6 The Vertebral Column Thoracic and Sacral Curves Are called primary curves (present during fetal development) Or accommodation curves (accommodate internal organs) Lumbar and Cervical Curves Are called secondary curves (appear after birth) Or compensation curves (shift body weight for upright posture)

Figure 7-17a Abnormal Curvatures of the Spine Kyphosis 27

Figure 7-17b Abnormal Curvatures of the Spine Lordosis 28

Figure 7-17c Abnormal Curvatures of the Spine Scoliosis 29

7-6 The Vertebral Column Vertebral Anatomy The vertebral body (centrum) Transfers weight along the spine The vertebral arch Posterior margin of vertebral foramen The articular processes Lateral projections between laminae and pedicles

Figure 7-18a Vertebral Anatomy Articular processes Vertebral arch Vertebral body The major components of a typical vertebra 31

7-6 The Vertebral Column Vertebral Anatomy The vertebral arch Pedicles Walls of the vertebral arch Laminae Roof of the vertebral arch

7-6 The Vertebral Column Vertebral Anatomy The vertebral arch Spinous process Projection where vertebral laminae fuse Transverse process Projection where laminae join pedicles

7-6 The Vertebral Column Vertebral Anatomy The articular processes Superior articular process Inferior articular process Have articular facets on articular faces

Figure 7-18b Vertebral Anatomy Superior articular process Pedicle Transverse process Vertebral body Spinous process Inferior articular facet Arrow passing through vertebral foramen Inferior articular process A lateral and slightly inferior view of a vertebra 35

Figure 7-18c Vertebral Anatomy Spinous process Superior articular process Inferior articular process Transverse process Pedicle Inferior articular facet Vertebral foramen Vertebral body An inferior view of a vertebra 36

7-6 The Vertebral Column Vertebral Foramina Intervertebral foramina Gaps between pedicles of adjacent vertebrae For nerve connections to spinal cord Vertebral canal Formed by vertebral foramina Encloses the spinal cord

7-6 The Vertebral Column Intervertebral Discs Are pads of fibrocartilage Separate the vertebral bodies Absorb shocks

Figure 7-18d Vertebral Anatomy Superior articular facets Superior articular process Lamina of vertebral arch Spinous process Intervertebral disc Transverse process Vertebral body Inferior articular process An posterior view of three articulated vertebrae 39

Figure 7-18e Vertebral Anatomy Superior articular facets Lamina of vertebral arch Intervertebral foramen Intervertebral disc Spinous process Transverse process Vertebral body Inferior articular facet Arrow passing through vertebral canal A lateral and sectional view of three articulated vertebrae 40

7-7 Vertebral Regions Vertebral Regions Vertebrae are numbered By region, from top (superior) to bottom (inferior) C1 articulates with skull, L5 with sacrum Vertebrae of each region Have characteristics determined by functions

7-7 Vertebral Regions Regions of the Vertebral Column Cervical (C) Thoracic (T) Lumbar (L) Sacral (S) Coccygeal (Co)

7-7 Vertebral Regions The Cervical Vertebrae Small body (support only head) Large vertebral foramen (largest part of spinal cord) Concave superior surface Slope posterior to anterior C1 (atlas) has no spinous process All others have short spinous processes Tip of each spinous process is notched (bifid)

Figure 7-19a The Cervical Vertebrae Spinous process of vertebra prominens C7 A lateral view of the cervical vertebrae, C1–C7 44

Figure 7-19b The Cervical Vertebrae Vertebral arch Spinous process Lamina Vertebral foramen Superior articular process Pedicle Vertebral body Transverse process Superior articular facet Transverse foramen Costal process A superior view of a representative cervical vertebra showing characteristics of C3–C6. Notice the typical features listed in Table 7–2. 45

Figure 7-19c The Cervical Vertebrae Superior articular process Transverse process Inferior articular process Spinous process Bifid tip of spinous process Location of transverse foramen Inferior articular facet Vertebral body A lateral view of the same vertebra as in b. 46

7-7 Vertebral Regions The Cervical Vertebrae Transverse processes Are fused to costal processes Which encircle transverse foramina (protect arteries and veins) Atlas (C1) Articulates with occipital condyles of skull Has no body or spinous process Has a large, round foramen within anterior and posterior arches

7-7 Vertebral Regions The Cervical Vertebrae Axis (C2) Supports the atlas Has heavy spinous process To attach muscles of head and neck Axis and atlas bodies fuse during development to form the dens

Figure 7-19d The Cervical Vertebrae Dens of axis Anterior arch Transverse ligament Atlas (C1) Posterior arch Axis (C2) The atlas (C1) and axis (C2). 49

7-7 Vertebral Regions The Cervical Vertebrae Vertebra prominens (C7) Transitions to thoracic vertebrae Has a long spinous process with a broad tubercle Has large transverse processes Ligamentum nuchae (elastic ligament) extends from C7 to skull

7-7 Vertebral Regions Thoracic Vertebrae (T1–T12) Have heart-shaped bodies Larger bodies than in C1–C7 Smaller vertebral foramen than in C1–C7 Long, slender spinous processes Dorsolateral surfaces of body have costal facets Which articulate with heads of ribs

7-7 Vertebral Regions Thoracic Vertebrae (T1–T12) T1–T10 Have transverse costal facets On thick transverse processes for rib articulation Ribs at T1–T10 Contact costal and transverse costal facets T1–T8 articulate with two pairs of ribs At superior and inferior costal facets T9–T11 articulate with one pair of ribs T10–T12 transition to lumbar vertebrae

Figure 7-20a The Thoracic Vertebrae Intervertebral foramen T4 T5 T6 Thoracic vertebrae (T1–T12) T7 T8 T9 T10 T11 T12 A lateral view of the thoracic region of the vertebral column. The vertebra prominems (C7) resembles T1, but lacks facets for rib articulation. Vertebra T12 resembles the first lumbar vertebra (L1) but has a facet for rib articulation. 53

Figure 7-20b The Thoracic Vertebrae Spinous process Transverse process Lamina Transverse costal facet Superior articular facet Vertebral foramen Superior costal facet Vertebral body Thoracic vertebra, superior view. 54

Figure 7-20c The Thoracic Vertebrae Superior articular facet Superior costal facet for head of superior rib Transverse costal facet for tubercle of superior rib Transverse process Vertebral body Spinous process Inferior costal facet for head of inferior rib Thoracic vertebra, lateral view. 55

7-7 Vertebral Regions Lumbar Vertebrae (L1–L5) Largest vertebrae Oval-shaped bodies Thicker bodies than T1–T12 No costal or transverse costal facets Triangular vertebral foramen Superior articular processes Face up and in Inferior articular processes Face down and out

7-7 Vertebral Regions Lumbar Vertebrae (L1–L5) Transverse processes Slender Project dorsolaterally Spinous process Short, heavy For attachment of lower back muscles

Figure 7-21a The Lumbar Vertebrae Sacrum Coccyx A lateral view of the lumbar vertebrae and sacrum 58

Figure 7-21b The Lumbar Vertebrae Superior articular process Pedicle Transverse process Vertebral body Spinous process Inferior articular process Inferior articular facet A lateral view of a typical lumbar vertebra 59

Figure 7-21c The Lumbar Vertebrae Spinous process Superior articular facet Lamina Superior articular process Transverse process Transverse process Vertebral foramen Pedicle Vertebral body A superior view of the same vertebra shown in part b 60

7-7 Vertebral Regions The Sacrum Is curved, more in males than in females Protects reproductive, urinary, and digestive organs Attaches: The axial skeleton to pelvic girdle of appendicular skeleton Broad muscles that move the thigh

7-7 Vertebral Regions The Sacrum The adult sacrum Consists of five fused sacral vertebrae Fuses between puberty and ages 25–30 Leaving transverse lines Sacral canal Replaces the vertebral canal

7-7 Vertebral Regions The Sacrum Sacral cornua Horn shaped Formed by laminae of the fifth sacral vertebra Which do not meet at midline Sacral hiatus Opening at the inferior end of the sacral canal Formed by ridges of sacral cornua Covered by connective tissues

7-7 Vertebral Regions The Sacrum Median sacral crest Fused spinous processes Four pairs of sacral foramina open to either side Lateral sacral crest Fused transverse processes Attach to muscles of lower back and hip

7-7 Vertebral Regions The Sacrum Auricular surface Sacral tuberosity Thick, flattened area Articulates with pelvic girdle (forming sacroiliac joint) Sacral tuberosity Rough area Attaches ligaments of the sacroiliac joint

7-7 Vertebral Regions The Sacrum Base Ala Sacral promontory Apex 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

7-7 Vertebral Regions The Coccyx Attaches ligaments and a constricting muscle of the anus Mature coccyx Consists of three to five fused coccygeal vertebrae First two coccygeal vertebrae Have transverse processes Have unfused vertebral arches Coccygeal cornua Formed by laminae of first coccygeal vertebra

Figure 7-22a The Sacrum and Coccyx Articular process Entrance to sacral canal Sacral tuberosity Lateral sacral crest Median sacral crest Sacral hiatus Sacral cornu Coccygeal cornu A posterior view 68

Figure 7-22b The Sacrum and Coccyx Sacral promontory Auricular surface Lateral sacral crest Median sacral crest Sacral cornu Sacral curve Coccygeal cornu Coccyx A lateral view from the right side 69

Figure 7-22c The Sacrum and Coccyx Base Sacral promontory Ala Ala Sacral foramina Transverse lines Apex Coccyx An anterior view 70

7-8 The Thoracic Cage The Thoracic Cage The Rib Cage The skeleton of the chest Supports the thoracic cavity Consists of: Thoracic vertebrae Ribs Sternum (breastbone) The Rib Cage Formed of ribs and sternum

Figure 7-23a The Thoracic Cage Jugular notch T1 Clavicular articulation 1 Manubrium 2 3 Sternum Body True ribs (ribs 1–7) 4 Xiphoid process 5 Costal cartilages 10 T11 6 T12 11 7 Vertebrochondral ribs (ribs 8–10) 12 8 9 False ribs (ribs 8–12) Floating ribs (ribs 11–12) An anterior view, showing the costal cartilages and the sternum 72

Figure 7-23b The Thoracic Cage 1 T1 1 2 T2 2 3 3 T3 4 T4 4 5 T5 5 True ribs (ribs 1–7) 6 T6 6 7 T7 7 8 T8 8 T9 9 9 T10 10 T11 10 False ribs (ribs 8–12) 11 T12 11 12 12 L1 A posterior view, showing the articulations of the ribs and vertebrae 73

7-8 The Thoracic Cage Functions of the Thoracic Cage Protects organs of the thoracic cavity Heart, lungs, and thymus Attaches muscles For respiration Of the vertebral column Of the pectoral girdle and the upper limbs

thoracic cavity is similar to the movement of a Figure 7-24c The Ribs Sternum Ribs The effect of rib movement on the thoracic cavity is similar to the movement of a bucket handle. Elevation of curved ribs increases the volume of the thoracic cavity. 75

7-8 The Thoracic Cage Ribs (Costae) Are 12 pairs of long, curved, flat bones Extending from the thoracic vertebrae Ribs are divided into two types True ribs False ribs

7-8 The Thoracic Cage Ribs 1–7 (True Ribs) Vertebrosternal ribs Connected to the sternum by costal cartilages

7-8 The Thoracic Cage Ribs 8–12 (False Ribs) Do not attach directly to the sternum Vertebrochondral ribs (ribs 8–10) Fuse together Merge with cartilage before reaching the sternum Floating or vertebral ribs (ribs 11–12) Connect only to the vertebrae and back muscles Have no connection with the sternum

Figure 7-23a The Thoracic Cage Jugular notch T1 Clavicular articulation 1 Manubrium 2 3 Sternum Body True ribs (ribs 1–7) 4 Xiphoid process 5 Costal cartilages 10 T11 6 T12 11 7 Vertebrochondral ribs (ribs 8–10) 12 8 9 False ribs (ribs 8–12) Floating ribs (ribs 11–12) An anterior view, showing the costal cartilages and the sternum 79

7-8 The Thoracic Cage Structures of the Ribs The head (capitulum) At the vertebral end of the rib Has superior and inferior articular facets The neck The short area between the head and the tubercle

7-8 The Thoracic Cage Structures of the Ribs The tubercle (tuberculum) A small dorsal elevation Has an auricular facet that contacts the facet of its thoracic vertebra (at T1–T10 only) The tubular body (shaft) Attaches muscles of the pectoral girdle and trunk Attaches to the intercostal muscles that move the ribs

A superior view of the details of rib Figure 7-24a The Ribs Transverse costal facet Tubercle of rib Angle Neck Vertebral end Demifacet Head (capitulum) A superior view of the details of rib structure and the articulations between the ribs and thoracic vertebrae. 82

A posterior view of the head of a Figure 7-24b The Ribs Head Neck Attachment to costal cartilage (sternal end) Articular facets Tubercle Body Angle Costal groove A posterior view of the head of a representative rib from the right side (ribs 2–9). 83

7-8 The Thoracic Cage The Sternum A flat bone In the midline of the thoracic wall Three parts of the sternum The manubrium The sternal body The xiphoid process

7-8 The Thoracic Cage Manubrium The superior portion of sternum Broad, triangular shape Articulates with clavicles (collarbones) Articulates with cartilages of first rib pair Has a jugular notch, a shallow indentation between clavicular articulations

7-8 The Thoracic Cage The Sternal Body The Xiphoid Process Is tongue-shaped Attaches to the manubrium Attaches to costal cartilages of ribs 2–7 The Xiphoid Process Is the smallest part of the sternum Attaches to the sternal body Attaches to diaphragm and rectus abdominis muscles

Figure 7-23a The Thoracic Cage Jugular notch T1 Clavicular articulation 1 Manubrium 2 3 Sternum Body True ribs (ribs 1–7) 4 Xiphoid process 5 Costal cartilages 10 T11 6 T12 11 7 Vertebrochondral ribs (ribs 8–10) 12 8 9 False ribs (ribs 8–12) Floating ribs (ribs 11–12) An anterior view, showing the costal cartilages and the sternum 87

7-8 The Thoracic Cage Development of the Sternum The developing sternal body Consists of four unfused bones Completes fusion about age 25 Leaving transverse lines The xiphoid process Is the last part of sternum to fuse Can easily be broken away