Chapter 8 Skeletal System Mosby items and derived

Chapter 8 Skeletal System Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 1

Introduction Skeletal tissues form bones—the organs of the skeletal system The relationship of bones to each other and to other body structures provides a basis for understanding the function of other organ systems The adult skeleton is composed of 206 separate bones Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 2

Divisions of Skeleton (Figure 8 -1; Table 8 -1) Axial skeleton—the 80 bones of the head, neck, and torso; composed of 74 bones that form the upright axis of the body and six tiny middle ear bones Appendicular skeleton—the 126 bones that form the appendages to the axial skeleton; the upper and lower extremities Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 3

Axial Skeleton Skull—made up of 28 bones in two major divisions: cranial bones and facial bones (Figures 8 -2 to 8 -7; Table 8 -3) Ø Cranial bones • Frontal bone (Figure 8 -8, C) Forms the forehead anterior part of the top of the cranium Contains the frontal sinuses Forms the upper portion of the orbits Forms the coronal suture with the two parietal bones Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 4

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Axial Skeleton Ø Cranial bones (cont. ) • Parietal bones (Figure 8 -8, A) Form the bulging top of the cranium Form several sutures: lambdoidal suture with occipital bone; squamous suture with temporal bone and part of sphenoid; and coronal suture with frontal bone Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 6

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Axial Skeleton Ø Cranial bones (cont. ) • Temporal bones (Figure 8 -8, B) Form the lower sides of the cranium and part of the cranial floor Contain the inner and middle ears Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 8

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Axial Skeleton Ø Cranial bones (cont. ) • Occipital bone (Figure 8 -8, D) Forms the lower, posterior part of the skull Forms immovable joints with three other cranial bones and a movable joint with the first cervical vertebra Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 10

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Axial Skeleton Ø Cranial bones (cont. ) • Sphenoid bone (Figure 8 -8, E) A bat-shaped bone located in the central portion of the cranial floor Anchors the frontal, parietal, occipital, and ethmoid bones and forms part of the lateral wall of the cranium and part of the floor of each orbit (Figure 8 -7) Contains the sphenoid sinuses Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 12

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Axial Skeleton Ø Cranial bones (cont. ) • Ethmoid bone (Figure 8 -8, F) A complicated, irregular bone that lies anterior to the sphenoid and posterior to the nasal bones Forms the anterior cranial floor, medial orbit walls, upper parts of the nasal septum, and sidewalls of the nasal cavity The cribriform plate is located in the ethmoid Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 14

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Axial Skeleton Ø Facial bones (Table 8 -4) • Maxilla (upper jaw) (Figure 8 -8, H) Two maxillae form the keystone of the face Maxillae articulate with each other and with nasal, zygomatic, inferior concha, and palatine bones Forms parts of the orbital floors, roof of the mouth, and floor and sidewalls of the nose Contains maxillary sinuses Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 16

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Axial Skeleton Ø Facial bones (cont. ) • Mandible (lower jaw) (Figure 8 -8, M) Largest, strongest bone of the face Forms the only movable joint of the skull with the temporal bone • Zygomatic bone (Figure 8 -8, I) Shapes the cheek and forms the outer margin of the orbit Forms the zygomatic arch with the zygomatic process of the temporal bones Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 18

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Axial Skeleton Ø Facial bones (cont. ) • Nasal bone (Figures 8 -8, L, and 8 -10) Both nasal bones form the upper part of the bridge of the nose, whereas cartilage forms the lower part Articulates with the ethmoid bone, nasal septum, frontal bone, maxillae, and the other nasal bone Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 21

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Axial Skeleton Ø Facial bones (cont. ) • Lacrimal bone (Figure 8 -8, K) Paper-thin bone that lies just posterior and lateral to each nasal bone Forms the nasal cavity and medial wall of the orbit Contains groove for the nasolacrimal (tear) duct Articulates with the maxilla and the frontal and ethmoid bones Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 23

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Axial Skeleton Ø Facial bones (cont. ) • Palatine bone (Figure 8 -8, J) Two bones form the posterior part of the hard palate Vertical portion forms the lateral wall of the posterior part of each nasal cavity Articulates with the maxillae and the sphenoid bone Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 25

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Axial Skeleton Ø Facial bones (cont. ) • Inferior nasal conchae (turbinates) Form lower edge projecting into the nasal cavity and form the nasal meati Articulate with ethmoid, lacrimal, maxillary, and palatine bones • Vomer bone (Figure 8 -8, G) Forms posterior portion of the nasal septum Articulates with the sphenoid, ethmoid, and palatine bones and maxillae Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 27

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Axial Skeleton Eye orbits (Figure 8 -7) Ø Right and left eye orbits • Contain eyes, associated eye muscles, lacrimal apparatus, blood vessels, and nerves • Thin and fragile orbital walls separate orbital structures from cranial and nasal cavities and paranasal sinuses • Traumatic injuries may result in “blowout fractures” (Figure 8 -7, C) • “Raccoon eyes”—clinical sign of blowout fracture (Figure 8 -7, D) Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 29

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Axial Skeleton Fetal skull (Figure 8 -11) Ø Characterized by unique anatomic features not seen in adult skull Ø Fontanels or “soft spots” (4) allow skull to “mold” during birth process and permit rapid growth of brain (Table 8 -5) Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 31

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Axial Skeleton Fetal skull (cont. ) Ø Permits differential growth or appearance of skull components over time • Face—smaller proportion of total cranium at birth (1/8) than in adult (1/2) • Head at birth is ¼ total body height; at maturity is about 1/8 body height • Sutures appear with skeletal maturity (Table 8 -5) • Paranasal sinuses—change in size and placement with skeletal maturity (Figure 8 -9) • Appearance of deciduous and, later, permanent teeth Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 33

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Axial Skeleton Hyoid bone (Figure 8 -12) Ø U-shaped bone located just above the larynx and below the mandible Ø Suspended from the styloid processes of the temporal bone Ø Only bone in the body that articulates with no other bones Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 35

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Axial Skeleton Vertebral column (Figure 8 -13) Ø Forms the flexible longitudinal axis of the skeleton Ø Consists of 24 vertebrae plus the sacrum and coccyx Ø Segments of the vertebral column: • Cervical vertebrae, 7 • Thoracic vertebrae, 12 • Lumbar vertebrae, 5 • Sacrum—in adult, results from fusion of five separate vertebrae • Coccyx—in adult, results from fusion of four or five separate vertebrae Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 37

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Axial Skeleton Vertebral column (cont. ) Ø Characteristics of the vertebrae (Figure 8 -14; Table 8 -6) • All vertebrae, except the first, have a flat, rounded body anteriorly and centrally, a spinous process posteriorly, and two transverse processes laterally • All but the sacrum and coccyx have vertebral foramen • Second cervical vertebra has upward projection, the dens, to allow rotation of the head • Seventh cervical vertebra has long, blunt spinous process • Each thoracic vertebra has articular facets for the ribs Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 39

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Axial Skeleton Vertebral column (cont. ) Ø Vertebral column as a whole articulates with the head, ribs, and iliac bones Ø Individual vertebrae articulate with each other in joints between their bodies and between their articular processes Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 41

Axial Skeleton Sternum (Figure 8 -15) Ø Dagger-shaped bone in the middle of the anterior chest wall made up of three parts: • Manubrium—the upper, handle part • Body—the middle, blade part • Xiphoid process—the blunt cartilaginous lower tip, which ossifies during adult life Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 42

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Axial Skeleton Sternum (cont. ) Ø Manubrium articulates with the clavicle and first rib Ø Next nine ribs join the body of the sternum, either directly or indirectly, by means of the costal cartilage Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 44

Axial Skeleton Ribs (Figures 8 -15 and 8 -16) Ø Twelve pairs of ribs, with the vertebral column and sternum, form the thorax Ø Each rib articulates with the body and transverse process of its corresponding thoracic vertebra Ø Ribs 2 through 9 articulate with the body of the vertebra above Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 45

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Axial Skeleton Ribs (cont. ) Ø From its vertebral attachment, each rib curves outward, then forward and downward Ø Rib attachment to the sternum: • Ribs 1 through 8 join a costal cartilage that attaches it to the sternum • Costal cartilage of ribs 8 through 10 joins the cartilage of the rib above to be indirectly attached to the sternum • Ribs 11 and 12 are floating ribs, because they do not attach even indirectly to the sternum Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 47

Appendicular Skeleton Upper extremity (Table 8 -7) Ø Consists of the bones of the shoulder girdle, upper arm, lower arm, wrist, and hand Ø Shoulder girdle (Figure 8 -17) • Made up of scapula and clavicle • Clavicle forms only bony joint with trunk, the sternoclavicular joint • At its distal end, clavicle articulates with the acromion process of the scapula Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 48

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Appendicular Skeleton Upper extremity (cont. ) Ø Humerus (Figures 8 -18 and 8 -19) • The long bone of the upper arm • Articulates proximally with the glenoid fossa of the scapula and distally with the radius and ulna Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 50

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Appendicular Skeleton Upper extremity (cont. ) Ø Ulna • Long bone found on little finger side of forearm • Articulates proximally with humerus and radius and distally with a fibrocartilaginous disk Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 53

Appendicular Skeleton Upper extremity (cont. ) Ø Radius • Long bone found on thumb side of forearm • Articulates proximally with capitulum of humerus and radial notch of ulna; articulates distally with scaphoid and lunate carpals and with head of ulna Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 54

Appendicular Skeleton Upper extremity (cont. ) Ø Carpal bones (Figure 8 -20) • Eight small bones that form wrist • Carpals are bound closely and firmly by ligaments and form two rows of four carpals each Proximal row is made up of pisiform, triquetrum, lunate, and scaphoid Distal row is made up of hamate, capitate, trapezoid, and trapezium • The joints between radius and carpals allow wrist and hand movements Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 55

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Appendicular Skeleton Upper extremity (cont. ) Ø Metacarpal bones • Form framework of hand • Thumb metacarpal forms the most freely movable joint with the carpals • Heads of metacarpals (knuckles) articulate with phalanges Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 57

Appendicular Skeleton Lower extremity Ø Consists of the bones of hip, thigh, lower leg, ankle, and foot (Table 8 -8) Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 58

Appendicular Skeleton Lower extremity (cont. ) Ø Pelvic girdle is made up of the sacrum and the two coxal bones, bound tightly by strong ligaments (Figure 8 -21) • A stable circular base that supports the trunk and attaches the lower extremities to it • Each coxal bone is made up of three bones that fuse together (Figure 8 -22): Ilium—largest and uppermost Ischium—strongest and lowermost Pubis—anteriormost Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 59

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Appendicular Skeleton Lower extremity (cont. ) Ø Femur—longest and heaviest bone in the body (Figure 8 -23) Ø Patella—largest sesamoid bone in the body Ø Tibia • The larger, stronger, and more medially and superficially located of the two leg bones • Articulates proximally with the femur to form the knee joint • Articulates distally with the fibula and the talus Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 62

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Appendicular Skeleton Lower extremity (cont. ) Ø Fibula • The smaller, more laterally and deeply placed of two leg bones • Articulates with tibia Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 64

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Appendicular Skeleton Lower extremity (cont. ) Ø Foot (Figures 8 -24 and 8 -25) • Structure is similar to that of the hand, with adaptations for supporting weight • Foot bones are held together to form spring arches Medial longitudinal arch is made up of calcaneus, talus, navicular, cuneiforms, and medial three metatarsals Lateral longitudinal arch is made up of calcaneus, cuboid, and fourth and fifth metatarsals Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 66

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Skeletal Differences in Men and Women Male skeleton is larger and heavier than female skeleton Pelvic differences (Figure 8 -26; Table 8 -9) Ø Male pelvis—deep and funnel-shaped with a narrow pubic arch Ø Female pelvis—shallow, broad, and flaring with a wider pubic arch Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 68

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Cycle of Life: The Aging Skeleton Aging changes begin at fertilization and continue over a lifetime Ø Changes can be positive or negative Normal bone development is a skeletal aging process Ø Intramembranous ossification Ø Endochondral ossification Ø Appearance of ossification centers and closure of epiphyseal plates can be used to estimate potential growth and height Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 70

Cycle of Life: The Aging Skeleton Characteristics of bone during age Bone produced early in life is properly calcified but not brittle • Osteoblastic activity during early periods of bone remodeling results in deposition of more bone than is resorbed Prior to puberty results in growth of bones After puberty and until early thirties, replaced bone is stronger Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 71

Cycle of Life: The Aging Skeleton Ø Negative outcomes of skeletal aging begin between 30 and 40 years of age • Decrease in osteoblast numbers with production of lower quality matrix • Increase in osteoclast numbers and activity with increased bone loss • Mature osteocytes coalesce and shrink, producing a honeycomb of tiny holes in the compact bone Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 72

Cycle of Life: The Aging Skeleton Ø Negative outcomes (cont. ) • Skeleton as a whole loses strength, and fracture risk increases • Decrease in number of trabeculae in spongy bone in vertebral bodies and other bones results in “spontaneous” as well as compression fractures • Overall height decreases beginning at about age 35 • Osteoporosis is a common and very serious bone disease in old age Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 73

The Big Picture Skeletal system is a good example of increasing structural hierarchy in the body Ø Skeletal tissues are grouped into discrete organs—bones Ø Skeletal system consists of bones, blood vessels, nerves, and other tissues grouped to form a complex operational unit Ø Integration of skeletal system with other body organ systems permits homeostasis to occur Ø Skeletal system is more than an assemblage of individual bones—it represents a complex and interdependent functional unit of the body Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 74

Mechanisms of Disease— Bone Fractures Fracture defined as partial or complete break in continuity of a bone Ø Mechanical stress and traumatic injury are most common causes Ø Pathological or spontaneous fractures occur in absence of trauma Ø Stress fractures may not be apparent in clinical examination or standard x-ray images but can be seen in bone scans • Bone damage is microscopic • Caused by repetitive trauma (e. g. , marathon runners) Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 75

Mechanisms of Disease— Bone Fractures Fracture defined (cont. ) Ø Displaced, open or compound fractures—do not produce a break in the skin and pose less danger of infection Ø Nondisplaced, closed or simple fractures—do not produce a break in the skin and pose less danger of infection Ø Fracture types: • • Impacted—one end of fracture driven into diaphysis of other fragment Complete—break extends across entire section of bone Incomplete—some fracture components still partially joined Dentate—fracture components jagged and fit together like teeth on a gear • Comminuted—crushed, small, crumbled bone fragments near fracture Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 76

Mechanisms of Disease— Bone Fractures Ø Fracture types (cont. ) • Avulsion—bone fragments pulled away from underlying bone surface or bone totally torn from body part • Linear—fracture line parallel to the bone’s long axis • Transverse—fracture line at right angle to long axis of bone • Oblique—fracture line slanted or diagonal to longitudinal axis • Spiral—fracture line spirals around long axis • Hairline—common in skull—fracture components small and aligned; if fracture is pushed downward, called a depressed fracture Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 77

Mechanisms of Disease— Bone Fractures Ø Fracture types (cont. ) • Greenstick—bone bent but broken only on one side (common in children) • Pott’s—fracture of lower tibia • Colles’—fracture of distal radius • Le. Fort—fracture of face and/or base of skull • Hangman’s—fracture of posterior elements in upper cervical spine, especially the axis • Blowout—fracture of the eye orbit Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 78

Mechanisms of Disease— Bone Fractures Ø Osgood-Schlatter disease Ø Avulsion fracture of tibial tuberosity fragments the surface • Caused by powerful contraction of quadriceps muscle group pulling on patellar ligament attached to tibial tuberosity • Common in adolescent athletes in whom patellar ligament is stronger than underlying bone Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 79

Mechanisms of Disease— Treatment of Fractures Clinical signs of fracture include pain, loss of function, false motion, soft tissue edema, deformity, and crepitus Initial treatment is realignment and immobilization of bone fragments Ø Closed reduction—alignment completed without surgery Ø Open reduction—surgery required to align and internally immobilize bone fragments with screws, wires, plates, or other orthopedic devices Ø After reduction, immobilization generally accomplished by casts, splints, and bandages Ø Traction sometimes used—especially in children Ø Restoration of function is treatment priority following healing Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 80

Mechanisms of Disease—Mastoiditis Inflammation of air spaces within mastoid portion of temporal bone Ø Pus may enter mastoid air spaces from middle ear infection or otitis media Ø Mastoid air cells do not drain into nose as do paranasal sinuses Ø Infectious material may erode thin, bony partition separating air cells from cranial cavity, causing intracranial infection Ø Treatment is antibiotic therapy and surgical incision of eardrum to drain pus from middle ear Ø Surgical removal of part of mastoid process of temporal bone —mastoidectomy—is rare Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 81

Mechanisms of Disease— Abnormal Spinal Curvatures Normal curvature of spine is convex through the cervical and lumbar regions Ø Normal curves give spine strength for support of body and balance required to stand walk Abnormal curvatures Ø Lordosis—abnormally accentuated lumbar curve (“swayback”) • Frequently seen during pregnancy • May be secondary to traumatic injury Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 82

Mechanisms of Disease— Abnormal Spinal Curvatures Abnormal curvatures (cont. ) Ø Kyphosis—abnormally accentuated thoracic curvature (“hunchback”) • Frequent consequence of vertebral compression fractures in osteoporosis • Sign of Scheuermann’s disease, which may develop in children at puberty Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 83

Mechanisms of Disease— Abnormal Spinal Curvatures Abnormal curvatures (cont. ) Ø Scoliosis—abnormal side-to-side spinal curvature • Often appears before adolescence • Treatments vary with severity of curvature Milwaukee brace Transcutaneous stimulation Surgical grafting to the deformed vertebrae of bone from elsewhere in skeleton or of metal rods Mosby items and derived items © 2007, 2003 by Mosby, Inc. Slide 84