The Axial Skeleton. PowerPoint Lecture Presentations prepared by Jason LaPres. Lone Star College North Harris Pearson Education, Inc.

Transcription

1 7 The Axial Skeleton PowerPoint Lecture Presentations prepared by Jason LaPres Lone Star College North Harris

2 Skeletal System The skeleton forms the framework for the body Provides support: Attachment site for muscles; allowing movement Identification of bones, their landmarks and openings allows one to identify other structures found in the body 206 bones found in the adult body (infants with more some bones fuse later) How many bones are there in the axial skeleton? 2

3 Skeletal system divided into the Axial skeleton and the appendicular skeleton Axial skeleton: bones forming the longitudinal axis of the skeleton. Tan Composed of the skull (cranium and facial bones), vertebral column (vertebrae, sacrum, coccyx), thorax (ribs and sternum), auditory ossicles and hyoid bone Total 80 bones Appendicular skeleton: bones making up the extremities (upper and lower limbs) and the pelvic and pectoral girdles (bones connecting extremities to axial skeleton). Green Total of 126 bones Skeletal System 3

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5 Bone Types Long bones: typically longer than wide. Ex. humerus (arm bone) Compact bone at diaphysis; compact bone covering spongy bone at the epiphyses Short bones: length and width relatively equal. Ex. Carpal bones Compact bone covering spongy bone 5

6 Bone Types Flat bones: bones relatively flat. Ex. Cranial bones Compact bone sandwiching spongy bone Irregular bones: bones with complex shapes. Ex. vertebral bones Variable amount of compact bone covering spongy bone Sesamoid: bones with sesame seed shape. Ex. patella (knee caps) Compact bone covering spongy bone Protect tendons from wear 6

7 Bone Surface Markings Foramen- oval to round opening in bone Fossa- depression on bone large or small Meatus- canal-like passage Sulcus/Grovedepression or furrow Fissure- narrow, slitlike opening Sinus- cavity within bone filled with AIR Alveolus- pit or socket= teeth Openings and Depressions 7

8 Bone Surface Markings Facet flat articulating surface on bone Head- bony expansion on neck of bone Condyle- round articulating projection Ramus- arm-like portion of bone: jaw 8

9 Bone Markings - Projections Tuberosity- rough elevated surface Trochanter- very large, blunt projection Tubercle- small rounded process Crest- narrow ridge Line- narrow ridge; smaller than crest (nuchal line) Epicondyle- raised areas near condyle Spine- sharp, slender projection Protuberance- bony outgrowth- chin Process- bony projection Match: a)trochanter b)condyle c)fossa 4. round articulating projection 5. depression on bone Extra Credit very large, blunt projection 9

10 The Skull 22 bones joined together by sutures (immovable joints) 8 cranial bones surround cranial cavity which encloses the brain 14 facial bones support teeth, facial and jaw muscles Cavities - orbits, nasal cavity, oral (buccal) cavity, middle-, and inner ear cavities, and paranasal sinuses paranasal sinuses frontal, sphenoid, ethmoid, and maxillary lined by mucous membrane and air-filled lighten the anterior portion of the skull act as chambers that add resonance to the voice 8-10

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12 The Skull Cranial Bones (8) 1 Occipital, 2 Parietal, 1 Frontal, 2 Temporal, 1 Sphenoid, 1 Ethmoid Sutures The immovable joints of the skull The four major sutures 1. Lambdoid suture 2. Coronal suture 3. Sagittal suture 4. Squamous suture

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14 Cranial Fossa Anterior cranial fossa Frontal lobe Temporal lobe Middle cranial fossa Cerebellum Posterior cranial fossa Posterior cranial fossa Middle cranial fossa Anterior cranial fossa cranium (braincase) protects the brain and associated sense organs; does not expand-serious problem if brain swells base is divided into three basins that comprise the cranial floor anterior cranial fossa holds the frontal lobe of the brain middle cranial fossa holds the temporal lobes of the brain posterior cranial fossa contains the cerebellum 8-14 (a) Superior view (b) Lateral view

15 Axial Skeleton- Skull Facial Bones: 14 Form the framework of the face and protect openings to digestive and respiratory systems Protect and support special sense organs involved in vision, taste, smell, hearing and balance. Include: Maxillary (paired) Zygomatic (paired) Nasal (paired) Lacrimal (paired) Palatine (paired) Inferior nasal conchae/turbinates (paired) Vomer Mandible 3. 15

16 Facial Bones PALATINE BONE LACRIMAL BONE ZYGOMATIC BONE NASAL BONE MAXILLA INFERIOR NASAL CONCHA MANDIBLE VOMER Which of the following is NOT a facial bone? (maxilla, nasal, zygomatic, vertebrae or mandibule)

17 Cranial cavity: holds the brain Nasal cavity Buccal cavity: mouth Middle and inner ear cavities Orbits: eye sockets Paranasal sinuses Cavities of the Skull 17

18 Axial Skeleton--Skull Sinus cavities found within several bones Paranasal sinuses---open into the nasal cavity; lined with mucous membranes and function as resonating chambers. Filled with air- lightens the weight of anterior facial bones Frontal sinuses Ethmoid sinuses Sphenoid sinuses Maxillary sinuses 18

19 The Cranial Bones of the Skull Occipital (2)Parietal Frontal (2)Temporal Sphenoid Ethmoid Bones enclose the cranial cavity which contains the brain and its fluids, blood vessels, nerves, and membranes

20 The Cranial Bones of the Skull The Frontal Bone Located in the anterior cranium Forms the roofs of the orbits Forms most of the cranial floor (anterior) Frontal squama (forehead) Supra-orbital margin (protects eye) Frontal sinuses Supra-orbital foramen/notch For blood vessels of eyebrows, eyelids, and frontal sinuses

21 The Cranial Bones The Parietal Bones Form the roof and lateral sides of the cranium Articulates with parietal, occipital, temporal, frontal, and sphenoid bones

22 Temporal Cranial Bones Functions of the temporal bones i. Part of lateral walls of cranium and zygomatic arches ii. Articulate with mandible iii. Surround and protect inner ear iv. Attach jaw and head muscles Sections: squamous, tympanic and petrous Squamous part anterior and superior portion; attachment for temporalis muscle Petrous Part Contains the essential parts of the organ of hearing; one of hardest bone in the body Tympanic part surrounds the external acoustic meatus Mandibular fossa: depression that articulates with the mandibular condyle of the mandible (lower jaw bone) forming temporomandibular joint (TMJ)

23 The Cranial Bones- Temporal Bone External auditory meatus: bony canal that allows sound waves to enter middle ear Mastoid Process For muscle attachment Contains mastoid air cells connected to middle ear Zygomatic process: bony lateral projection--meets up with the temporal process of the zygomatic bone; forming zygomatic arch (cheekbone) Styloid Process To attach tendons and ligaments of the hyoid, tongue, and pharynx

24 Carotid canal Opening for carotid artery Cranial Bones Temporal Bones Jugular foramen Between occipital and temporal bones. Opening for jugular vein Squamous Petrous Internal auditory meatus: opening that allows facial nerve and vestibulocochlear nerve to pass 24

25 The Cranial Bones The Occipital Bone Foramen magnum connects cranial and spinal cavities; large opening for the spinal cord External occipital protuberance- bony projection that serves as an attachment site for connective tissue- ligament to 7 th vertebrae, binds skull to vertebral column Occipital condyles oval bony projections that articulate with superior articulating facets of C1 (first cervical vertebra forming atlanto-occipital joint) Inferior and superior nuchal lines: bony ridges that extend from the external occipital protuberance; serve as attachment sites for muscles and ligaments

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27 Sphenoid Found at the middle part of the base of the skull Cranial Bones Unites cranial and facial bones Strengthens sides of the skull Forms the floor and posterior and lateral walls of the orbit Appearance of a butterfly when viewed anteriorly Sella turcica: Turkish saddle on superior surface; houses the pituitary gland. Greater wing: form part of the anterio-lateral floor of the cranium and lateral wall of the skull; fits between squamous and petrous parts of temporal bone; contains numerous foramen, remains a separate bone even after birth Lesser wing: just superior and anterior to greater wings; form the posterior walls of the orbit; contains optic canal, superior orbital fissure allows access to several cranial nerves The sella turcica is found in what cranial bone? 27

28 Sphenoid

29 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Optic foramen Lesser wing Greater wing Sella turcica Dorsum sellae (a) Superior view Hypophyseal fossa Foramen rotundum Anterior clinoid process Foramen ovale Foramen spinosum Lesser wing Greater wing Body Foramen ovale Dorsum sellae Superior orbital fissure Foramen rotundum Lateral pterygoid plate Medial pterygoid plate (b) Posterior view Pterygoid processes

30 Cranial Bones: Sphenoid Bone Optic foramen: opening for the optic nerve; seen between the lesser wings and the body of the sphenoid Superior orbital fissure: bony slit between the greater and lesser wings where nerves controlling eye movement pass Pterygoid processes: inferiorly directed bony projections; attachment site for muscles of the lower jaw and soft palate used in mastication (chewing) Hypophyseal Fossa: A depression within the sella turcica holds the pituitary gland Foramen associated with the sphenoid: foramen ovale and foramen rotundum- trigeminal nerve foramen spinosum arteries for meninges; trigeminal Sphenoid sinuses: found in the body of the sphenoid; empty into the nasal cavity 30

31 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Optic foramen Lesser wing Greater wing Sella turcica Dorsum sellae (a) Superior view Hypophyseal fossa Foramen rotundum Anterior clinoid process Foramen ovale Foramen spinosum Lesser wing Greater wing Body Foramen ovale Lateral pterygoid plate Medial pterygoid plate (b) Posterior view Dorsum sellae Superior orbital fissure Foramen rotundum Pterygoid processes

32 Cranial Bones Ethmoid Bone: Anterior cranial floor location; medial to the orbits Forms part of the medial walls of the orbits Superior portion of nasal septum (bony divider of nasal cavity) Superior potion of the nasal cavity Bone is delicate; susceptible to injury from a sharp blow. Force of a blow can drive bone fragments into the brain. Damage can lead to infection, loss of smell and/or taste Ethmoid sinuses: formed by ethmoid cells 32

33 Cranial Bones: Ethmoid Structures Cribiform plate: forms roof of nasal cavity; Crista galli: projection from cribiform plate; attachment point for the dura mater (outermost membrane covering the brain) Cribiform (olfactory) foramina- olfactory bulbs rests in these depressions-allows passage of olfactory nerves to brain Perpendicular plate: midline bony plate forming the superior, anterior portion of the nasal septum Septum divides nasal cavity into left and right spaces called nasal fossae Two lateral masses: (Labyrinth) superior and middle nasal conchae: bony projections in the nasal cavity; cause inhaled air to make contact with mucous membranes warming, filtering and humidifying the air before going to the lungs 33

34 Ethmoid Bone Cribiform plate Crista galli

35 Nasal Septum images/en/8870.jpg&imgrefurl= m&usg= TzAoX8V7s14Li7_3z8a5KMX7OLE=&h=320&w=400&sz=13&hl=en&start= 13&zoom=1&tbnid=NS3osIMJUwoMnM:&tbnh=137&tbnw=171&prev=/images%3Fq% 3Dethmoid%2Bbone%26um%3D1%26hl%3Den%26biw%3D1009%26bih%3D749%26 tbs%3disch:10%2c449&um=1&itbs=1&iact=hc&vpx=548&vpy=290&dur=109&hovh=2 01&hovw=251&tx=102&ty=80&ei=R96lTICGNoiengfb9LiQAQ&oei=Pt6lTMLfK8vGnAe VviQAQ&esq=2&page=2&ndsp=20&ved=1t:429,r:3,s:13&biw=1009&bih=749

36 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Crista galli Cribriform plate Cribriform foramina Sella turcica Sphenoid sinus Occipital bone Frontal bone Frontal sinus Nasal bone Nasal conchae: Superior Middle Inferior Nasal cartilages Sphenoid bone Palatine bone Lacrimal bone Maxilla Anterior nasal spine Incisive foramen Lip Incisor

37 Ethmoid Bone Structures Perpendicular plate Ethmoid air cells ( Sinuses) Middle nasal concha

38 y854.png/250px-gray854.png

39 Ethmoid Bone Structures

40 The Facial Bones 2 Maxillae (maxillary bones) 2 Palatine bones 2 Nasal bones 2 Inferior nasal conchae 2 Zygomatic bones 2 Lacrimal bones 1 Mandible 1 Vomer

41 Fig. 8.3 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Frontal bone Glabella Coronal suture Squamous suture Sphenoid bone Lacrimal bone Nasal bone Middle nasal concha Infraorbital foramen Vomer Supraorbital foramen Parietal bone Supraorbital margin Temporal bone Ethmoid bone Zygomatic bone Inferior nasal concha Maxilla Mandible Mental protuberance Mental foramen

42 Facial Bones NASAL BONES Form the bridge of the nose Pearson Education, Inc.

43 MAXILLAE Originally paired bones--fuse midline; the upper jawbone Supports upper teeth Forms the floor of the orbits, lateral walls and floor of the nasal cavity (the hard palate--divides the oral from the nasal cavity; called the palatine process of the maxilla) Failure of the maxillary bones to fuse at the palatine process result in a cleft palate. Soft palate skeletal muscle and glandular tissue no bone Contains maxillary sinuses that drain into the nasal cavity Facial Bones Palatine Bone palatine process 43

44 Facial Bones: Maxilla Infraorbital foramen: openings for nerve and blood vessels just inferior to the orbits via foramen rotundum of sphenoid Alveolar processes (bony ridge): where teeth articulate at alveoli (sockets) Orbital rim protects eye and orbit 44

45 The Facial Bones The Maxillae Incisive foramen: opening in the palatine process for the passage of blood vessels and nerves Palatine Bones Form the posterior 1/3 rd of hard palate (maxilla makes up the anterior 2/3) Contributes a small portion of the eye orbit

46 Inferior Nasal conchae/turbinates bony projections in the nasal cavity; creates air turbulence and increases surface area for the warming, filtering and humidifying of incoming air Facial Bones Vomer Inferior and slightly posterior portion of the nasal septum. Articulates with the perpendicular plate of the ethmoid to form the nasal septum 46

47 Inferior Nasal Conchae 8-47

48 Vomer Inferior half of the nasal septum Supports cartilage of nasal septum 8-48

49 FRONTAL BONE Frontal sinuses ETHMOID NASAL BONE PALATINE BONE (bony palate) MAXILLA (bony palate) Sphenoidal sinuses SPHENOID Superior 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. Nasal conchae of ethmoid

50 Lacrimal Bones Form part of the medial walls of the orbit Smallest facial bone Include lacrimal fossa which allow tears to drain into lacrimal sacs Zygomatic Bones Form the cheekbones Temporal process of the zygomatic bone joins the zygomatic process of temporal bone to form zygomatic arch Forms lateral wall of the orbit Facial Bones 50

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52 Mandible Facial Bones Only movable bone jaw joint between mandibular fossa of the temporal bone and condyloid process of the mandible Holds the lower teeth Attachment of muscles of mastication temporalis muscle onto coronoid process masseter muscle onto angle of mandible The lower jaw bone Strongest of the facial bones A depression on the medial surface for submandibular salivary gland 8-52

53 Mandible Characterized by several landmarks: Body: main portion of the mandible; curved horizontal portion Rami: the arm of the mandible; vertical portions Angle: point where the rami project off of the body Mandibular condyle and condylar process: rounded knob and projection articulates mandibular fossa and articular tubercle of the temporal bone- -forms temporomandibular joint (TMJ) Mental Protuberance: attachment for facial muscles Facial Bones 53

54 Mandible Coronoid process: projection that is the attachment site for the temporalis muscle (used in chewing) Mandibular foramen: opening allows a branch of the trigeminal nerve to innervate the lower teeth, blood vessels to profuse the area Mental foramen: opening in the anterior surface of mandible body for the passage of blood vessels and nerves to lips/chin Alveolar process: bony ridge where teeth articulate with alveoli Mandibular symphysis: midline fusion point of the two parts of the mandible Facial Bones

55 Hyoid Bone U shaped bone--does not articulate with another bone Found in the anterior cervical region--inferior to the mandible Connects to styloid process of temporal bone via ligaments and muscles Attaches muscles of the larynx, pharynx, and tongue muscles involved in chewing and swallowing Consists of body and lesser and greater horns Hydoid bone is often examined in forensics to determine cause of death from strangulation 55

56 Figure 7-13 The Orbital Complex Optic canal/foramen - transmits optic nerve Superior orbital fissure- opening for several cranial nerves Inferior orbital fissure opening for maxillary nerve FRONTAL BONE SPHENOID Supra-orbital notch Optic canal Superior orbital fissure Inferior orbital fissure ZYGOMATIC BONE Infra-orbital groove Infra-orbital foramen MAXILLA ETHMOID LACRIMAL BONE Lacrimal sulcus Nasolacrimal canal PALATINE BONE

57 Fontanelles Areas of incomplete cranium intramembranous ossification Will eventually ossify to form sutures Provide flexibility for fetal head as it goes through birth canal Allows for growth of brain Anterior Fontanelle Frontal, sagittal, and coronal sutures/ closes within 2 yrs Occipital Fontanelle Lambdoid and sagittal sutures / closes within 2 mos Sphenoidal Fontanelles Squamous and coronal sutures / closes 3 months Mastoid Fontanelles Squamous and lambdoid sutures/ closes by one year

58 Vertebral Column Composed of vertebrae that function to: Support the body Protect the spinal cord Act as anchoring sites for muscle Support the head Act as attachment points for the ribs and pelvic girdle. Composed of 26 vertebrae in the adult (33 in children) Sacral and coccygeal vertebrae fuse in adulthood 58

59 Vertebral Column Five major regions Cervical (7) Thoracic (12) Lumbar (5) Sacral (1); 5 vertebrae fused Coccygeal (1); 4 vertebrae fused 59

60 Vertebral Column Curves of the vertebral column: Function to absorb shock, provide strength 4 normal curves: Cervical (3 mo) and Lumbar (1 yr) curves are convex; SECONDARY curves (appear after birth) or compensation curves (shift body weight for upright posture) Develop as infant is able to hold up the head and balance weight to stand /walk Thoracic and sacral curves are concave; PRIMARY curves (present during fetal development) or accommodation curves (accommodate internal organs) These four curves develop from the single thoracic curve of the newborn 60

61 Abnormal Curvatures Kyphosis (hunchback): exaggerated curvature of the thoracic region; due to : osteroporosis, osteomalacia, adolescence boys-wrestling, weight lifting Lordosis (swayback): exaggerated curvature of the lumbar region Scoliosis: Abnormal lateral bending of the spinedevelopment issue-adolescent girls

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63 Vertebrae Vertebrae of different regions differ in their shape, size, and bony landmarks A typical Vertebra consists of the following: Body: thick, anterior disc shaped bony structure. Intervertebral discs sit on the superior and inferior surface. Supports most of the weight Pedicles: Walls of the vertebral arch; bony bridges projecting laterally and posteriorly from the body to the laminae Laminae: Roof of the vertebral arch; bony bridges that connect with the pedicles anteriorly and with the spinous process posteriorly. Transverse processes: lateral bony projections from the junction of the pedicles and laminae; attachment site for muscles Spinous process: posteriorly oriented bony projection; attachment sites for muscles 63

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65 Vertebral foramen: opening formed by the pedicles and laminae of the vertebrae Vertebral canal Formed by vertebral foramina Encloses and protects the spinal cord Intervertebral foramen: opening formed between adjoining vertebrae where spinal nerves exit to the periphery Superior articulating processes: processes that allow articulation with the inferior articulating process of the vertebra just above it Inferior articulating processes: processes that allow articulation with the superior articulating processes of the vertebra just below it. Vertebrae 65

66 Intervertebral discs Discs found between the vertebrae from cervical region to the lumbar region Disc consists of two portions: Nucleus fibrosus: outer ring of fibrocartilage Nucleus pulposus: soft elastic material inside the nucleus fibrosus Discs allow for a strong joint between bones, allows for flexibility, and flatten to absorb shock With aging the disc become stiffer and less thick---- results in decreased height 66

67 Disorders Herniated disc 1% shorter at the end of the day due to body weight compressing the disc and squeezing out fluid. During sleep fluid reabsorbed Stressors cause shift of discs--may result in rupture of nucleus fibrosus and protrusion of nucleus pulposus If nerves leading to the lower extremity affected, may be neurological symptoms muscle weakness, numbness, tingling. Typically occurs in the lumbar region due to supporting weight and providing flexibility for bending Spina bifida a congenital (birth) defect Failure of vertebral laminae to unit Nervous tissue is unprotected paralysis 67

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69 Vertebral Regions Vertebrae are numbered By region, from top (superior) to bottom (inferior) C 1 articulates with skull, L 5 with sacrum Vertebrae of each region Have characteristics determined by functions Regions of the Vertebral Column Cervical (C) Thoracic (T) Lumbar (L) Sacral (S) Coccyxgeal (Co)

70 Vertebral Column Regions The typical cervical vertebrae : Small/ small oval body Triangular shaped vertebral foramen that are large Transverse foramen present: foramen for the passage of vertebral arteries, veins and nerves 70

71 C1 known as the atlas; supports weight of the skull no spinous process; Superior articulating facets articulate with occipital condyles of occipital bone (atlantooccipital joint) allows nodding of head ( yes ) C2 known as the axis Tip of each spinous process is notched (bifid) Contains a tooth like projection at the body known as the dens or odontoid process--forms a pivot point with C1 (atlanto-axial joint) allows for the lateral turning of the head. ( no ) attach muscles of head and neck Transverse ligament- arches across ring of atlas; holds the dens in contact with the anterior arch Cervical 71

72 Atlas and Axis Articulation Superior YES articulate facet That holds the head NO Atlas = C1 Has no body Just a ring Axis = C2 8-72

73 Vertebral Column Regions Thoracic Vertebrae: T1-T12 Larger than cervical vertebrae Round vertebral foramen Heart-shaped bodies; contain facets or edifices for the articulation with the heads of ribs Longer and larger transverse processes T1-T10 have facets that articulate with rib tubercles Long, sharp, inferior directed spinous processes Facets for the articulation of ribs 73

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75 Thoracic Vertebrae 75

76 Vertebral Column Regions Lumbar Vertebrae Largest of the vertebrae--support large amounts of body weight Bodies large and oval shaped Vertebral foramen triangular in shape Projections are short and blunt Spinous process short and hatchet shaped; attachment of lower back muscles Superior articulating facets are medially directed rather than superiorly directed 76

77 Lumbar Vertebrae 77

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79 Vertebral Regions -The Sacrum Is curved, more in males than in females Consists of five fused sacral vertebrae Fusion of sacral vertebrae; begins midteens completed by early 30 s Leaving transverse lines Protects reproductive, urinary, and digestive organs Attaches: The axial skeleton to pelvic girdle of appendicular skeleton Lateral auricular surface articulates with ilium of coxal bones forming sacroiliac joint. Broad muscles that move the thigh

80 The Sacrum Sacral hiatus Opening at the inferior end of the sacral canal Forms opening for exit of inferior spinal nerves Anterior and Posterior sacral foramina-opening for nerves and blood vessels Median sacral crest Fused spinous processes Lateral sacral crest-attach to muscles of lower back and hip Fused transverse processes Auricular surface Thick, flattened area Articulates with pelvic girdle (forming sacroiliac joint) Sacral tuberosity Rough area Attaches ligaments of the sacroiliac joint Sacral canals- continuation of vertebral cavity- passageway for spinal cord; Replaces the vertebral canal

81 The Sacrum

82 Coccyx Single, small bone Commonly called the tailbone Attaches ligaments and a constricting muscle of the anus Mature coccyx (20-30 yrs) Consists of three to five fused coccygeal vertebrae Coccygeal cornua Two knob-like upward extensions for the attachment of ligaments that hold the coccyx to the sacrum Attachment site for muscles of pelvic floor Fractured by fall or during childbirth

83 Thorax Thoracic cage Consists of sternum, ribs, costal cartilage and thoracic vertebral bodies Supports the thoracic cavity Protects organs of the thoracic cavity Heart, lungs, and thymus Attaches muscles for respiration the vertebral column the pectoral girdle and the upper limbs 83

84 Sternum (a flat bone): Thorax Consists of four unfused bones. Completes fusion about age 25 Jugular notch a target for finger strikes in such martial arts as Jiu-Jitsu. Seen in Matrix movie point of attraction by many men and women. Jewelry enhancement Manubrium: Broad, triangular superior portion; articulates with the clavicles and the first two ribs Body: forms most of the sternum; articulates with cartilage of ribs 3-10 Xiphoid process: the last part of sternum to fuse; made of hyaline cartilage that ossifies at around 40. Can easily be broken away therefore caution must be used for administering CPR to in older individuals Attachment site for abdominal muscle Attaches to the sternal body, the diaphragm and rectus abdominis muscles

85 Thorax Ribs: True ribs (1-7) join directly with sternum via costal cartilage False ribs (8-12) do not directly attach to sternum via own cartilage or do not connect at all Ribs fuse together and merge with cartilage before reaching the sternum Floating ribs (11 and 12) connect only to the vertebrae and back muscles; do not connect to sternum at all; 85

86 Thorax Ribs: 12 pairs Each rib articulates with posteriorly with the corresponding thoracic vertebra the head of each rib fits into a facet on the body of a vertebra or the superior and inferior demifacets on adjacent vertebrae Articular part of rib tubercle joins to vertebra articulating facet on transverse process of inferior vertebra Costal groove protects blood vessels and nerves Body is the main part of the rib Costal angle: area of the rib with the greatest increase in curvature 86

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