Chapter 7 Axial Skeleton

I can name and identify all of the bones of the axial skeleton. I can describe the major landmarks of the cranial and facial bones I can describe and discuss the differences between the cervical, thoracic, lumbar, sacral and coccygeal vertebrae Learning Targets

Section 1 I. Axial skeleton The axial skeleton forms the central axis of the body. 1. made up of: a. skull b. vertebral column c. ribs d. sternum 2. functions: supports & protects brain, provides surface area for muscle attachment

Section 2 B. Skull 1. can be divided into two categories a. cranium - enclosed brain b. facial bones 2. Cranial bones: 8 cranial bones form case to protect & contain brain a. Frontal bone - single convex bone -extends from orbits to the coronal suture - forms forehead & roof of the eye orbits -Frontal sinuses: air filled cavities, lie within the frontal bone

b. Occiptal bone- forms back bottom part - foramen magnum: opening in occipital bone, connects cranium to spinal cavity -Occipital condyles mark articulation w/ vertebra of neck c. Parietal bones (2)- form middle top portion d. Temporal Bones (2)- form lower sides, temple region -zygomatic process helps form cheek bone - external acoustic meatus- opening to outer ear - mastoid process: attachment site for muscles that rotate or extend the head - styloid process: attachment site of tendons of muscles associated w/ tongue

e. Sphenoid- forms part of the floor of the cranium (inside top) -looks like bat w/ wings extended -great wing: form back wall of eye orbit -pterygoid process: attachment sites for muscles that move jaw f. Ethmoid-inside, top, forms roof of nasal cavity -cribriform plate: forms floor of cranium - perpendicular plate: forms part of nasal septum

3. sutures- immovable joints that form between bones of the skull (pg 215) a. lamboid- btwn occipital & parietal bones b. coronal- btwn frontal & parietal bones c. sagittal- btwn 2 parietal bones d. squamous- btwn temporal & parietal (on R & L sides)

4. Facial bones a. Maxillae (2)- support upper teeth, form upper jaw, inferior orbital rim, & most of hard palate b. Palatine bones (2)- form posterior portion of hard palate & bottom of orbit c. Nasal bones (2)- supper bridge of nose d. Vomer (1) – forms inferior part of nasal septum e. Inferior nasal conchae (2)- inside nasal cavity, help increase epithelial surface area to warm humidify air

f. Lacrimal bones (2)- smallest facial bone, forms medial part of eye orbit g. Mandible (1)- forms the lower jaw, alveolar processes support teeth, condylar process articulates with the temporal bone (tmj- temporal mandibular joint)

Section 3 C. Foramina & Fissures of Skull 1. allow passageway for nerves and blood vessels in skull a. examples: *supra-orbital foramen: nerve and blood vessel supply to eyebrow/eyelid * optic canal in sphenoid- optic nerve brings info from eye to brain

7.4 D. Orbital & Nasal complexes 1. orbits- bony recesses that contain eyes a. orbit is formed by 7 bones of orbital complex b. frontal bone forms most of roof; maxilla most of the floor c. lacrimal, ethmoid, sphenoid, zygomatic bone, & palatine bone help make up orbit as well

7.5 E. Fontanelles 1. largest fibrous areas btwn cranial bones 2. at birth, cranial bones are connected by fibrous connective tissue- allow distortion of skull (delivery) 3. anterior fontanelle is the largest- where frontal, sagittal, & coronal sutures meet a. known as soft spot b. present until nearly 2 yrs of age! 4. occipital, sphenoidal, & mastoid fontanelles disappear w/in 1-2 months after birth 5. growth of cranium is coordinated w/ expansion of brain- brain stops growing before age 5, cranial sutures develop

7.6 F. Vertebral column 1. spine has 26 bones: 24 vertebrae, sacrum, 1 coccyx (tailbone) 2. functions a. provides support for head, neck & trunk b. protects spinal cord 3. structure- four curves- help bring body weight in line with body axis a. cervical, thoracic, lumbar, & sacral b. primary curves- curves in infants- C shape from thoracic & sacral curves c. secondary curves- lumbar & cervical, form months after birth

4. vertebra- three basic parts a 4. vertebra- three basic parts a. body- transfers weight along vertebral column, separated by cartilage (intervertebral discs) b. arch- forms part of vertebral foramen -has walls (pedicles) - roof (lamina) - forms vertebral canal, which encloses the spinal cord c. articular processes - spinous process is located where laminae fuse, projects out (you see/feel these) - transverse processes project laterally; sites of muscle attachment or rib articulation

-articular processes: superior & inferior: where each vertebra articulates with the one above & below it d. intervertebral foramina- gaps btwn pedicles of successive vertebrae, allow passage of nerves running to/from spinal cord

Section 7 G. Regions of the vertebrae * cervical (1-7): neck * thoracic ( 1-12): superior portion of back * lumbar (1-5): inferior portion of back * sacrum (fused) * coccyx (fused)- tailbone 1. cervical vertebrae a. most mammals have 7 b. smallest in vertebra column- small body, large vertebral foramen

c. head is large in comparison- rapid change is speed can cause whiplash, partial or complete dislocation of cervical vertebrae d. C1 is called the Atlas * holds up head, articulates w/occipital condyles *permits you to nod “yes” *doesn’t have a body or a spinous process * large round vertebral foramen e. C2 is called the Axis * fused to atlas, creating the dens- a process on the axis, allows you to shake “no” *fusion is not complete in children- shaking can cause damage to spinal cord

f. c7 is the vertebra prominens. last cervical vertebra f. c7 is the vertebra prominens * last cervical vertebra * large transverse processes for muscle attachment * ligamentum nuchae- ligament begins at c7 and extends to occipital crest-helps you lift your head

2. Thoracic vertebrae *12 total, heart shaped body that is larger than cervical *smaller vertebral foramen *each articulates w/ ribs at costal facets of vertebrae * T1-T8 each articulate w/ 2 pair of ribs, have superior and inferior sets of facets * T9-T11 articulate w/ one pair- single set of facets 3. Lumbar vertebrae * 5 total, largest of vertebrae, have thicker body * don’t have costal facets *transverse process stick out (most like a “t”)

*bear the most weight, massive spinous processes provide area for attachment of lower back muscles 4. Sacrum- five fused sacral vertebrae * vertebrae begin fusing after puberty & are fused by age 25- 30 * protects reproductive, digestive, & urinary organs * attaches axial skeleton to pelvic girdle * crests – ridges that form where process of individual vertebrae fused * base- superior portion, apex- narrow inferior portion, ala- (wing)- extends on either side

5. coccyx- small, consists of 3-5 vertebrae, fused by age 26 5. coccyx- small, consists of 3-5 vertebrae, fused by age 26 * provides attachment site for ligaments & a muscle associated w/ anal opening * coccygeal cornua- stick out of 1st vertebrae, curve to meet sacrum

Section 8 H. Thoracic Cage- chest 1. consists of : thoracic vertebrae, ribs, & sternum 2. functions include: a. protection of heart, lungs, thymus b. attachment site for muscles involved in respiration, maintaining position of spine, & movements of pectoral girdle & upper limbs 3. Ribs (costae) a. elongate, flattened bones b. 12 pairs c. true ribs- 1st-7th pair, are connected to sternum by costal cartilages

d. false ribs- 8th -12th pairs, don’t attach directly to sternum, but fuse together e. 11th & 12th pair- floating ribs, no connection w/ sternum f. Parts of Ribs - head (capitulum)- end that articulates w/ vertebra - tuberculum- contacts transverse process of vertebra - long shaft is the body g. ribs can bend/move to absorb blows, sudden impact can result in fracture h. ribs are bound tightly in CT, so can heal w/o cast

4. Sternum- breastbone a. three parts 4. Sternum- breastbone a. three parts * manubrium- widest, most superior part, has jugular notch btwn clavicle articulations * body- where ribs 2-7 attach to sternum * xiphoid process- smallest, inferior part, diaphragm & rectus abdominis muscles attach, easily broken by impact b. ossification of sternum- age 6-10, not complete until age 25 (before fusion, body alone is 4 separate bones)