Ch 7 - Axial Skeleton s2009

8/10/2019 Ch 7 - Axial Skeleton s2009

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Chapter 7:

The Axial Skeleton

part 1


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Structures of Bones

Articulations:

contacts with other bones

Marks:

areas of muscle and ligament attachment

Foraminae:

openings for nerves and blood vessels


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The Axial Skeleton - longitudinal axis

Supports and protects organsin body cavities

Attaches to muscles of:

head, neck, and trunk

respiration

appendicular skeleton


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Bones of the Axial Skeleton - 80 The skull:

8 cranial bones 14 facial bones

Bones associated

with the skull: 6 auditory ossicles

the hyoid bone

The vertebral column:

24 vertebrae

the sacrum

the coccyx

The thoracic cage:

24 ribs the sternum

Th Sk ll


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The Skull The skullprotects:

the brain

entrances torespiratory system

entrance to digestive

system

Has 22 bones:

8 cranial bones:

form the braincase or cranium 14 facial bones:

protect and support entrances

to digestive and respiratory

tracts


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Cranial Bones Enclose the cranial cavity

Which contains the brain:

and its fluids, blood vessels, nerves, membranes


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The Facial Bones Superficial facial bones

for muscle

attachment Maxillary

Lacrimal

Nasal

Zygomatic Mandible

Deep facial bones

separate the oral and

nasal cavities & form the

nasal septum Palatine bones

Inferior nasal conchae

Vomer


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The 4 Major Sutures (immovable joints of the skull)1. Lambdoid suture-

separates occipital from

parietal bones2. Coronal suture-attaches

frontal bone to parietal

bones (calvaria consists

of occipital, parietal,and frontal bones)

3. Sagittal suture-between

the parietal bones

lambdoid suture to

coronal suture

4. Squamous suture-form

boundaries between

temporal bones and

parietal bones


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The Hyoid Bone (assoc w/facial bones) Functions

Supports the larynx

Attaches muscles of the

larynx, pharynx, and tongue

Articulations

Does not articulate with anyother bone

Connects lesser hornsto

styloid processes of

temporal bones

Marks Body- attaches muscles of larynx, tongue, and pharynx

Greater hornssupport larynx & attach muscles of the tongue

Lesser hornsattach stylohyoid ligaments & support hyoid andlar nx


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The Infant Skull

Figure 715

Grows rapidly

Is large compared to the body

Has many ossification centers

Fusion is not complete at birth:

2 frontal bones

4 occipital bones

several sphenoid and temporal elements


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Fontanels Are areas of fibrous connective tissue (soft spots)

Cover unfused sutures in the infant skull Allow the skull to flex during birth

Anterior fontanel-frontal, sagittal, and coronal

sutures soft spot

Occipital fontanel-lambdoid and sagittal sutures

Th A i l Sk l 2


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The Axial Skeleton part 2

The Vertebral Column

The spine or vertebral column:

protects the spinal cord

supports the head and body

26 bones:

24 vertebrae, the sacrum,and coccyx

Regions

Cervical(C) 7 v

Thoracic(T) 12 v

Lumbar(L) 5 v

Sacral(S)

Coccygeal(Co)


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Curvatures

Cervical curve

Thoracic curve

Lumbar curve

Sacral curve

Primary Curves Thoracicand sacral curves present during fetal development

aka accommodation curves-

accommodate internal organs

Secondary Curves Lumbarand cervical curves-appear after birth

Aka compensation curves-shift body weight for upright

posture

V b


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Vertebrae

3 Parts of a Vertebra

vertebral body (centrum)-transfers weight along

the spine

vertebral arch-posterior margin of vertebral

foramen

articular processes-lateral projections between

laminae and pedicles


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Figure 717d,e

Intervertebral

Discs Are pads of

fibrocartilage

Separate the

vertebralbodies

Absorb shocks

V b l R i


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Vertebral Regions

Figure 716

Vertebrae are numbered: by region, from top to bottom

C1 articulates with skull, L5

with sacrum Vertebrae of each region:

have characteristics

determined by functions

Th C i l V t b


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Characteristics of C1C7:

small body (support only head)

large vertebral foramen (largest part of spinal

cord)

C1(atlas) has no spinous process all others have

short spinous processes tip of each spinous process is notched (bifid)

The Cervical Vertebrae

l


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Atlas(C1):

articulates with occiptal condyles of skull

has no body or spinous process

has a large, round foramen within anteriorand posteriorarches

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

V b i (C )


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Vertebra prominens(C7):

transitions to thoracic vertebrae

has a long spinous process with a broad tubercle

Whiplash:

a traumatic dislocation of cervical vertebrae

Th Th i V t b


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The Thoracic Vertebrae

Characteristics T1T12:

have heart-shaped bodies

larger bodies than in C1C7

smaller vertebral foramen thanin C1C7

long, slender spinous processes Dorsolateral surfaces of body

have costal facets-whicharticulate with heads of ribs

T T


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T1T10:

Ribs at T1T10:-contact costaland transverse costal

facets T1T8articulate with 2 pairs of ribs-at superiorand

inferiorcostal facets

T9T11articulate with 1 pair of ribs

T10T12transition to lumbar vertebrae

Th L b V t b


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The Lumbar Vertebrae

Characteristics L1L5: largest vertebrae

oval-shaped bodies

thicker bodies than T1T12

no costal or transverse

costal facets

triangular vertebral

foramen

Transverse processes-

slender

Spinous process-short,

heavy

for attachment of lower

back muscles

C i g V t b


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Comparing Vertebrae

Table 72

The Sac m and Cocc


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The Sacrum and Coccyx

Characteristics -

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

The adult sacrum:

consists of 5 fused sacral

vertebrae fuses between puberty

and ages 2530

leaving transverse lines

S l l


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Sacral canal:

replaces the vertebral canal

Sacral cornua:

horn-shaped formed by laminae of the 5th 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

M di l t


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Median sacral crest:

fused spinous processes

Lateral sacral crest:

attach to muscles of lower back and hip Auricular surface:

articulates with pelvic girdle (sacroiliac joint)

Sacral tuberosity:

attaches ligaments of the sacroiliac joint

4 R i f th S


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4 Regions of the Sacrum

Base-the broad superior surface

Ala-wings at either side of the base to attach

muscles

Apex-the narrow inferior portion articulates with

the coccyx

Ch t i ti


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Characteristics - coccyx:

attaches ligaments and a constricting muscle of

the anus

mature coccyx-consists of 3 to 5 fused coccygealvertebrae

first 2 coccygeal vertebrae-have transverse

processes and have unfused vertebral arches

Th Th i C


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The Thoracic Cage The skeleton of the chest-supports the

thoracic cavity

Consists of:

thoracic vertebrae

ribs

sternum (breastbone)

Rib Cage - formed of

ribs and sternum

A ti l ti f Rib d V t b


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Articulations of Ribs and Vertebrae

Figure 722b

Functions

Protects organs of

the thoracic cavity-

heart, lungs, and

thymus

Attaches muscles: for respiration

of the vertebral column

of the pectoral girdle

of the upper limbs

Th Rib


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The Ribs Functions

are flexible

are mobile

can absorb shock

Rib movements

(breathing): affect width and depth

of thoracic cage

changing its volume

Ribs(costae)-12 pairs of long, curved, flat

bones extending from the thoracic vertebrae

Ribs 1 7 (true ribs)


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Ribs 17 (true ribs)

vertebrosternal ribs

connected to the sternum by costal cartilages

Ribs 812 (false ribs):

do not attach directly to the sternum Vertebrochondral ribs(ribs 810):

fuse together

merge with cartilage before reaching the sternum

Floatingor vertebral ribs(ribs 1112):

connect only to the vertebrae have no connection with the sternum


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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 thehead and the tubercle

The tubercle(tuberculum):

a small dorsal elevation

has an auricular facet that

contacts the facet of its

thoracic vertebra (at T1

T10

only)

The tubercular body(shaft): attaches muscles of the

pectoral girdle and trunk

attaches to the intercostal

muscles which move the ribs

The Sternum


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The Sternum The sternum-a flat bone in the midline of the

thoracic wall

3 parts 1-manubrium:

superior portion of

sternum

broad, triangular

shape

articulates with

collarbones (clavicles)

& cartilages of 1st rib

pair

has a jugular notch

between clavicular

articulations

2-sternal body:

tongue-shaped

attaches to the

manubrium& costal

cartilages of ribs 27


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3-xiphoid process:

smallest part of the

sternum

attaches to thesternal body &

diaphragmand

rectus abdominis

muscles Development

Sternum

completes fusion about age 25

Xiphoid process:

last part of sternum to fuse

can easily be broken away

Ch 7 - Axial Skeleton s2009

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Transcript of Ch 7 - Axial Skeleton s2009