7 The Skeleton

The bones of the axial skeleton SKELETAL SYSTEM 206 Cranium 8 APPENDICULAR SKELETON (see Section 2) Skull 126 Face 14 Skull and associated bones 29 Auditory ossicles 6 Associated bones Hyoid 1 AXIAL SKELETON Costal cartilages (cartilages of ribs) 80 Sternum 1 Thoracic cage 25 Ribs 24 Intervertebral discs (cartilage) Vertebrae 24 Vertebral column 26 Sacrum 1 Coccyx 1 Figure 7 Section 1 The Axial Skeleton Figure 7 Section 1 2

The 22 bones that form the skull, plus the seven bones associated with the skull SKULL FACE 14 CRANIUM 8 ASSOCIATED BONES (see Module 7.7) 7 Maxillary bones 2 Occipital bone 1 Palatine bones 2 Parietel bones 2 Nasal bones 2 Frontal bone 1 Inferior nasal conchae Temporal bones 2 Hyoid bone 1 2 Auditory ossicles enclosed in temporal bones Sphenoid 1 6 Zygomatic bones 2 Ethmoid 1 Lacrimal bones 2 Figure 7.1.1 The skull has cranial and facial components that are usually bound together by sutures Vomer 1 Mandible 1 Figure 7.1 1 3

Frontal bone Parietal bone Temporal bone The facial and cranial bones of the skull Cranial Bones Frontal bone Parietal bone Temporal bone Sphenoid Ethmoid Figure 7.1.4 The skull has cranial and facial components that are usually bound together by sutures Occipital bone Figure 7.1 4 4

The major sutures of the skull Frontal bone Coronal suture Parietal bone Squamous suture Temporal bone Occipital bone Lambdoid suture Lateral view of skull Sagittal suture Figure 7.1.5-6 The skull has cranial and facial components that are usually bound together by sutures Parietal bone Parietal bone Sutural bone Lambdoid suture Occipital bone Posterior view of skull Figure 7.1 5 – 6 5

The bones of the skull in anterior view Facial Bones Cranial Bones Nasal bone Parietal bone Frontal bone Lacrimal bone Palatine bone Sphenoid Zygomatic bone Maxilla Ethmoid Figure 7.2.1 Facial bones dominate the anterior aspect of the skull, and cranial bones dominate the posterior surface Inferior nasal concha Vomer Mandible Figure 7.2 1 6

The bones of the skull in posterior view Cranial Bones Sagittal suture Parietal bones Occipital bone Lambdoid suture Temporal bone Squamous suture Mastoid process Figure 7.2.2 Facial bones dominate the anterior aspect of the skull, and cranial bones dominate the posterior surface Styloid process External occipital crest Mandible Figure 7.2 2 7

Frontal bone Parietal bone Temporal bone Zygomatic bone Occipital bone The skull in lateral view Coronal suture Superior and inferior temporal lines Frontal squama (forehead) Squamous part (of temporal bone) Squamous suture Sphenoid Frontal bone Parietal bone External acoustic meatus Ethmoid Lacrimal bone Temporal bone Nasal bone Maxilla Lambdoid suture Zygomatic bone Alveolar processes Occipital bone Figure 7.3.1 The lateral and medial aspects of the skull share many surface features Mastoid process Styloid process Mandible Zygomatic arch (cheekbone) Mental protuberance Mandibular angle Figure 7.3 1 8

The interior of the skull, as revealed by sagittal section that passes just to the left of the midline Frontal bone Coronal suture Sphenoidal sinus (right) Sphenoid Sella turcica Petrous part (of temporal bone) Frontal sinuses Parietal bone Squamous suture Lambdoid suture Nasal bone Temporal bone Ethmoid Vomer Figure 7.3.2 The lateral and medial aspects of the skull share many surface features Internal acoustic meatus Occipital bone Palatine bone Hypoglossal canal Maxilla Mandible Styloid process Figure 7.3 2 9

External occipital crest An inferior view of the skull Zygomatic bone Frontal bone Palatine bone Maxilla Vomer Foramina Foramen lacerum Sphenoid Foramen ovale Zygomatic arch Styloid process Carotid canal Mandibular fossa Jugular foramen Temporal bone Figure 7.4.1 The foramina on the inferior surface of the skull lead into the interior of the cranium Occipital condyle Stylomastoid foramen Occipital bone Lambdoid suture Foramen magnum Inferior and superior nuchal lines External occipital crest Figure 7.4 1 10

Internal occipital crest The interior of the skull, as revealed by horizontal section Nasal bones Frontal bone Crista galli Ethmoid Cribriform plate Sella turcica Foramen rotundum Sphenoid Foramen lacerum Temporal bone Foramen ovale Foramen spinosum Carotid canal Internal acoustic meatus Figure 7.4.2 The foramina on the inferior surface of the skull lead into the interior of the cranium Mastoid foramen Parietal bone Jugular foramen Hypoglossal canal Occipital bone Internal occipital crest Figure 7.4 2 11

Two views of the sphenoid Greater wing Optic canal Lesser wing Superior surface of the sphenoid Hypophyseal fossa Figure 7.5.1 The shapes and landmarks of the sphenoid, ethmoid, and palatine bones can best be seen in the isolated bones Sella turcica Foramen spinosum Foramen ovale Foramen rotundum Superior orbital fissure Sphenoidal spine Figure 7.5 1 12

The ethmoid Cribriform plate Crista galli Lateral masses Figure 7.5.2 The shapes and landmarks of the sphenoid, ethmoid, and palatine bones can best be seen in the isolated bones Superior and middle nasal conchae Perpendicular plate Superior surface Posterior surface Figure 7.5 2 13

The palatine bones Orbital process Perpendicular plate of the palatine bone Nasal crest Figure 7.5.3 The shapes and landmarks of the sphenoid, ethmoid, and palatine bones can best be seen in the isolated bones Horizontal plate Figure 7.5 3 14

The bones of the orbital complex Supra-orbital margin Lacrimal fossa Supra-orbital notch Frontal bone Palatine bone Ethmoid Lacrimal sulcus Sphenoid Temporal bone Figure 7.6.1 Each orbital complex contains one eye, and the nasal complex encloses the nasal cavities Nasolacrimal canal Zygomatic bone Middle nasal concha Zygomaticofacial foramen Intra-orbital foramen Inferior nasal concha Maxilla Figure 7.6 1 15

The bones of the nasal complex Cranial cavity Frontal bone Ethmoidal air cells Orbit Zygomatic bone Maxillary sinus Maxilla Frontal section Figure 7.6.2 Each orbital complex contains one eye, and the nasal complex encloses the nasal cavities Mandible Nasal cavities Figure 7.6 2 16

The bones that form and surround the nasal cavity, as revealed by a sagittal section with nasal septum removed Frontal sinuses Frontal bone Sphenoidal sinus Sphenoid Nasal bone Ethmoid Lacrimal bone Superior nasal concha Inferior nasal concha Middle nasal concha Perpendicular plate of palatine bone Pterygoid plates Figure 7.6.3 Each orbital complex contains one eye, and the nasal complex encloses the nasal cavities Maxilla Hard palate Figure 7.6 3 17

The mandible in lateral view Coronoid process Teeth (molars) Condylar process Alveolar process Figure 7.7.1 The mandible forms the lower jaw, and the associated bones of the skull perform specialized functions Mental foramen Mandibular notch Body of the mandible Ramus of the mandible Figure 7.7 1 18

The medial surface of the mandible Coronoid process Condylar process Mylohyoid line Head Mandibular foramen Alveolar part Figure 7.7.2 The mandible forms the lower jaw, and the associated bones of the skull perform specialized functions Position of the submandibular salivary gland Figure 7.7 2 19

The hyoid bone Greater horn Lesser horn Body of the hyoid Figure 7.7.3 The mandible forms the lower jaw, and the associated bones of the skull perform specialized functions Figure 7.7 3 20

The auditory ossicles, bones associated with the skull SKULL ASSOCIATED BONES 7 FACE 14 CRANIUM 8 Maxillary bones 2 Occipital bone 1 Palatine bones 2 Parietal bones 2 Auditory ossicles enclosed in temporal bones (see Chapter 15) Nasal bones 2 Frontal bone 1 Hyoid bone 1 6 Inferior nasal conchae 2 Temporal bones 2 Sphenoid 1 Zygomatic bones 2 Ethmoid 1 Lacrimal bones 2 Vomer 1 Mandible 1 Figure 7.7.4 The mandible forms the lower jaw, and the associated bones of the skull perform specialized functions Figure 7.7 4 21

Right parietal bone Left parietal bone The anterior fontanelle (“soft spot”) and associated sutures in the skull of an infant Sagittal suture Right parietal bone Left parietal bone Anterior fontanelle Coronal suture Frontal suture Figure 7.8.1 Fontanelles permit cranial growth in infants and small children Frontal bone Frontal suture Figure 7.8 1 22

Left parietal bone Right parietal bone The occipital fontanelle and associated sutures in a posterior view of the skull of an infant Left parietal bone Right parietal bone Sagittal suture Occipital fontanelle Figure 7.8.2 Fontanelles permit cranial growth in infants and small children Lambdoid suture Occipital bone Figure 7.8 2 23

Frontal bone Parietal bone Temporal bone A lateral view of the skull of an infant Sphenoidal fontanelle Coronal suture Frontal bone Parietal bone Sphenoid Squamous suture Mastoid fontanelle Nasal bone Temporal bone Maxilla Figure 7.8.3 Fontanelles permit cranial growth in infants and small children Mandible Lambdoid suture Occipital bone Figure 7.8 3 24

Parietal bone Frontal bone Sagittal suture Frontal bone Parietal bone A superior view of the skull of an infant Parietal bone Lambdoid suture Frontal bone Frontal suture Sagittal suture Occipital fontanelle Anterior fontanelle Frontal bone Parietal bone Occipital bone Figure 7.8.4 Fontanelles permit cranial growth in infants and small children Coronal suture Figure 7.8 4 25

The spinal curves and vertebral regions in the adult vertebral column Primary curves develop before birth, and secondary curves after birth. Regions are defined by anatomical characteristics of individual vertebrae. C1 C2 Cervical curve (a secondary curve) C3 C4 Cervical (7 vertebrae) C5 C6 C7 T1 T2 T3 T4 T5 Thoracic curve (a primary curve) T6 T7 Thoracic (12 vertebrae) T8 T9 T10 T11 T12 Figure 7.9.1 The vertebral column has four spinal curves, and vertebrae have both anatomical similarities and regional differences L1 L2 Lumbar curve (a secondary curve) L3 Lumbar (5 vertebrae) L4 L5 Sacral Sacral curve (a primary curve) Coccygeal Figure 7.9 1 26

Figure 7.9.1 The vertebral column has four spinal curves, and vertebrae have both anatomical similarities and regional differences Figure 7.9 1 27

The parts of a typical vertebra Parts of a Vertebra Articular processes Vertebral arch Vertebral body Figure 7.9.2 The vertebral column has four spinal curves, and vertebrae have both anatomical similarities and regional differences Superior view Figure 7.9 2 28

The parts of the vertebral arch The Vertebral Arch Spinous process Vertebral foramen Laminae Transverse process Figure 7.9.3 The vertebral column has four spinal curves, and vertebrae have both anatomical similarities and regional differences Pedicles Inferior view Figure 7.9 3 29

A lateral view of three vertebrae Pedicle Intervertebral disc Intervertebral foramina Figure 7.9.4 The vertebral column has four spinal curves, and vertebrae have both anatomical similarities and regional differences Vertebral body Vertebral canal Figure 7.9 4 30

Superior articular process Inferior articular process A posterior view of two vertebrae Articular facet Superior articular process Inferior articular process Figure 7.9.5 The vertebral column has four spinal curves, and vertebrae have both anatomical similarities and regional differences Figure 7.9 5 31

A typical cervical vertebra Bifid spinous process Vertebral foramen Transverse foramen Transverse process Figure 7.10.1 There are seven cervical vertebrae and twelve thoracic vertebrae Vertebral body Costal process Figure 7.10 1 32

The first two cervical vertebrae: the atlas and the axis Anterior arch of atlas Atlas Dens (odontoid process) Ligament that enables rotation (as in shaking the head to indicate “no”) Joint that permits nodding (as in indicating “yes”) Figure 7.10.2 There are seven cervical vertebrae and twelve thoracic vertebrae Axis Posterior arch of atlas Figure 7.10 2 33

A lateral view of the seven cervical vertebrae prominens Figure 7.10.3 There are seven cervical vertebrae and twelve thoracic vertebrae Figure 7.10 3 34

Figure 7.10.4 There are seven cervical vertebrae and twelve thoracic vertebrae 35

A typical thoracic vertebra in superior view Transverse process Spinous process Superior articular facet Vertebral foramen Superior costal facet Figure 7.10.5 There are seven cervical vertebrae and twelve thoracic vertebrae Vertebral body Figure 7.10 5 36

A typical thoracic vertebra in lateral view Superior costal facet Transverse costal facet Vertebral body Spinous process Inferior costal facet Figure 7.10.6 There are seven cervical vertebrae and twelve thoracic vertebrae Transverse process Figure 7.10 6 37

An anterior view of the thoracic cage Jugular notch T1 1 2 3 Sternum Manubrium 4 5 Ribs Figure 7.12.1 The thoracic cage protects organs in the chest and provides sites for muscle attachment Vertebrosternal ribs (ribs 1–7) 6 Body 11 T11 Vertebrosternal ribs (ribs 8–10) 7 T12 12 8 9 Floating ribs (ribs 11 and 12) Xiphoid process 10 Costal cartilages Figure 7.12 1 38

Posterior view of a representative rib (ribs 2–9) Articular facets on head Capitulum Tubercle Angle of the rib Shaft Figure 7.12.2 The thoracic cage protects organs in the chest and provides sites for muscle attachment Superficial surface Costal groove Figure 7.12 2 39

The action of a typical rib, which can be likened to the movement of a bucket’s handle Sternum Ribs Figure 7.12.4 The thoracic cage protects organs in the chest and provides sites for muscle attachment Figure 7.12 4 40

Superior view of a representative rib Transverse process Tubercular facet Superior articular facet Transverse costal facet Figure 7.12.3 The thoracic cage protects organs in the chest and provides sites for muscle attachment Inferior articular facet Figure 7.12 3 41

The bones of the appendicular skeleton SKELETAL SYSTEM 206 AXIAL SKELETON 80 Clavicle 2 Pectoral girdle 4 Scapula 2 Humerus 2 Radius 2 Ulna 2 Upper limbs 60 Carpal bones 16 Metacarpal bones 10 APPENDICULAR SKELETON 126 Phalanges (proximal, middle, distal) 28 Hip bone (coxal bone) 2 Pelvic girdle 2 Figure 7 Section 2 The Appendicular Skeleton Femur 2 Patella 2 Tibia 2 Fibula 2 Lower limbs 60 Tarsal bones 14 Metatarsal bones 10 Phalanges 28 Figure 7 Section 2 42

The relationship of the clavicle to adjacent bones Jugular notch Scapula Humerus Figure 7.13.1 The pectoral girdles—the clavicles and scapulae—connect the upper limbs to the axial skeleton Anterior view Figure 7.13 1 43

Two views of the right clavicle Superior view LATERAL MEDIAL Acromial end Sternal end Figure 7.13.2 The pectoral girdles—the clavicles and scapulae—connect the upper limbs to the axial skeleton LATERAL Inferior view MEDIAL Figure 7.13 2 44

Two views of the right scapula Scapular spine Acromion Coracoid process Superior border Superior angle Acromion Supraspinous fossa Subscapular fossa Process that supports the cup-shaped glenoid cavity Figure 7.13.3-4 The pectoral girdles—the clavicles and scapulae—connect the upper limbs to the axial skeleton Medial border Infraspinous fossa Lateral border Anterior view Posterior view Inferior angle Figure 7.13 3 – 4 45

A lateral view of the right scapula Coracoid process Glenoid cavity Acromion Figure 7.13.5 The pectoral girdles—the clavicles and scapulae—connect the upper limbs to the axial skeleton Figure 7.13 5 46

Surface features of the right humerus Anterior view Posterior view Head Greater tubercle Greater tubercle Lesser tubercle Intertubercular groove Anatomical neck Surgical neck Radial groove Shaft Deltoid tuberosity Figure 7.14.1 The humerus of the arm articulates with the radius and ulna of the forearm Radial fossa Coronoid fossa Olecranon fossa Lateral epicondyle Medial epicondyle Trochlea Capitulum Trochlea Figure 7.14 1 47

Surface features of the right ulna and radius Posterior view Anterior view Radial head Trochlear notch Olecranon Neck of the radius Coronoid process Proximal radio-ulnar joint Radial notch at proximal radio-ulnar joint Radial tuberosity Ulna Radius Radius Ulna Figure 7.14.2 The humerus of the arm articulates with the radius and ulna of the forearm Interosseous membrane Ulnar notch Distal radio-ulnar joint Ulnar head Styloid process of the radius Ulnar head Styloid process of the ulna Figure 7.14 2 48

The bones of the carpus (wrist) Proximal Carpal Bones Scaphoid Lunate Pisiform Triquetrum Right wrist and hand, anterior (palmar) view Radius Ulna I II III IV V Metacarpal bones Figure 7.15.1 The wrist is composed of carpal bones, and the hand consists of metacarpal bones and phalanges Proximal phalanx Distal Carpal Bones Trapezium Trapezoid Capitate Hamate Middle phalanx Distal phalanx Figure 7.15 1 49

The metacarpal bones (designated I–V) and the phalanges of the hand Radius Ulna Proximal Carpal Bones Scaphoid Lunate Triquetrum Distal Carpal Bones Pisiform Trapezium Trapezoid Capitate Hamate I V III II IV Proximal phalanx of pollex Metacarpal bones Proximal phalanx Distal phalanx of pollex Figure 7.15.2 The wrist is composed of carpal bones, and the hand consists of metacarpal bones and phalanges Middle phalanx Right wrist and hand, posterior (dorsal) view Distal phalanx Figure 7.15 2 50

A hip bone, which consists of an ilium, an ischium, and a pubis Ilium A lateral view of the right hip bone POSTERIOR ANTERIOR Pubis Ischium Iliac crest Gluteal Lines Anterior Inferior Anterior superior iliac spine Posterior Posterior superior iliac spine Lunate surface Posterior inferior iliac spine Figure 7.16.1-2 The hip bone forms by the fusion of the ilium, ischium, and pubis Greater sciatic notch Acetabulum Ischial spine Ischial ramus Ischial tuberosity Acetabular notch Figure 7.16 1 – 2 51

A medial view of the right hip bone Ilium ANTERIOR POSTERIOR Pubis Ischium Iliac crest Iliac tuberosity Iliac fossa Auricular surface of the ilium Arcuate line of the ilium Figure 7.16.3 The hip bone forms by the fusion of the ilium, ischium, and pubis Greater sciatic notch Pectineal line Obturator foramen Superior pubic ramus Pubic symphysis Ischial ramus Inferior pubic ramus Figure 7.16 3 52

The structures of the pelvis Sacrum Hip Bone Ilium Coccyx Pubis Ischium L5 Iliac crest Iliac fossa Ilium Sacrum Figure 7.17.1 The pelvis consists of the two hip bones plus the sacrum and the coccyx Sacro-iliac joint Acetabulum Pubic tubercle Obturator foramen Ischium Pubic symphysis Figure 7.17 1 53

Superior view Inferior view The locations and extents of the true (lesser) pelvis (in purple) and the false (greater) pelvis Superior view Inferior view Pelvic outlet False pelvis Ischial spine Figure 7.17.2 The pelvis consists of the two hip bones plus the sacrum and the coccyx Pelvic inlet Pelvic brim Pelvic outlet Figure 7.17 2 54

The shapes of the pelvis in females and males The pelvis of a female The pelvis of a male Female Male Ischial spine Ischial spine Figure 7.17.3 The pelvis consists of the two hip bones plus the sacrum and the coccyx 100° or more 90° or less Figure 7.17 3 55

Figure 7.18.1-2 The femur articulates with the patella and tibia Landmarks of the right femur Neck Fovea capitis Greater trochanter Greater trochanter Femoral head Intertrochanteric crest Gluteal tuberosity Intertrochanteric line Linea aspera Lesser trochanter Anterior view Posterior view Figure 7.18.1-2 The femur articulates with the patella and tibia Shaft Lateral supracondylar ridge Popliteal surface Adductor tubercle Patellar surface Lateral epicondyle Medial epicondyle Intercondylar fossa Lateral condyle Medial condyle Lateral epicondyle Lateral condyle Figure 7.18 1 - 2 56

Anterior view Posterior view The surface features of the patella Base of patella Lateral facet, for lateral condyle of femur Attachment area for quadriceps tendon Medial facet, for medial condyle of femur Attachment area for the patellar ligament, which attaches the patella to the tibia Articular surface of patella Apex of patella Figure 7.18.3 The femur articulates with the patella and tibia Anterior view Posterior view Figure 7.18 3 57

Anterior view Posterior view The features of the right tibia and fibula Superior tibiofibular joint Articular surface of medial tibial condyle Intercondylar eminence Lateral tibial condyle Articular surface of lateral tibial condyle Medial tibial condyle Head of the fibula Lateral tibial condyle Tibial tuberosity Head of fibula Interosseous membrane Anterior view Posterior view Anterior margin of the tibia Figure 7.18.4 The femur articulates with the patella and tibia Tibia Fibula Fibula Medial malleolus of the tibia Inferior tibiofibular joint Lateral malleolus of the fibula Lateral malleolus (fibula) Inferior articular surface Figure 7.18 4 58

The Ankle (Tarsus) The bones of the ankle and foot The ankle consists of seven tarsal bones. Calcaneus Talus Navicular Trochlea Cuboid Cuneiform bones Metatarsals Articulations of the cuboid and the cuneiform bones with the metatarsal bones V IV III II I Figure 7.19 The ankle and foot contain tarsal bones, metatarsal bones, and phalanges Metatarsal bones (designated I–V) Proximal phalanx Phalanges Distal phalanx Proximal, middle, and distal phalanges Hallux Figure 7.19 1 59

A lateral view of the right ankle and foot Cuboid bone Navicular bone Cuneiform bones Metatarsal bones (I–V) Lateral surface of the trochlea Phalanges Lateral view I II Attachment site for the calcaneal tendon (Achilles tendon) III IV V Figure 7.19.2 The ankle and foot contain tarsal bones, metatarsal bones, and phalanges Figure 7.19 2 60

A medial view of the right ankle and foot Phalanges Metatarsal bones Medial cuneiform bone Navicular bone Talus Medial view I Calcaneus Figure 7.19.2 The ankle and foot contain tarsal bones, metatarsal bones, and phalanges Longitudinal arch Transverse arch Figure 7.19 2 61