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- Formed by two sets of bones
- All bones in skull are held together sutures, which are interlocking immovable joints
- Only the mandible is attached to the rest of the skull by a freely movable joint
- Encloses and protects the fragile brain tissue.
- Eight large flat bones
- Except for two paired bones (the pariental and temporal), they are single bones
Skull: Frontal Bone
- Forms the forhead
- Forms the bony projections under the eyebrows and the superior part of each eyes orbit
Skull: Pariental Bones
- Paired pariental bones form most of the superior and lateral walls of the cranium.
- They meet in the midline of the skull at the sagital suture
- Form the coronal suture where they meet the frontal bone.
Skull: Temporal Bones
- Lie inferior to the pariental bones
- Join pariental bones at sqaumous sutures
Important bone markings on the temporal bone
- External auditory meatus is a canal that leads to the eardrum and the middle ear
- Styliod process a sharp needlelike projection is just inferior to the external auditory meatus. Many neck muscles use the styloid process as an attachment piont.
- Zygomatic process is a thin bridge of bone that joins with the cheek bone anteriorly
- Mastiod process is a rough projection posterior and inferior to external auditory metus which is full of air cavities (mastiod sinuses) it povides an attchment site for some muscles of the neck.
- Jugular foramen at the juction of the occipital and temporal bones allows passage of the large jugular vein which drains the brain. Just anterior to it is the carotid canal through which the internal carotid artery runs, supplying blood to most of the brain.
Skull: Occipital Bone
- Most posterior bone of the Cranium
- Forms floor and back wall
- Joins the pariental bone anteriorly at the lamboid suture
- Base of the occipital bone is a large opening called the foramen magnum ("large hole")
- Foramen magnum surrounds lower part of the brain and allows the spinal cord to connect with the brain
- Lateral to the foramen magnum on each side are rocker like occipital condyles which rest on the first vertebra of the spinal column.
Skull: Spheniod bone
- Butterfly shaped
- Spans the width of the skull and forms part of the floor of the cranial cavity
- In the middle of the speniod cavity is a small depression called sella turica or Turks Saddle which holds the pituitary gland in place
- The foramen ovale, a large oval opening in line with the posterior end of the sella turcica allows fibers of cranial nerve V to pass to the chewing muscles of the lower jaw
- Parts of the spheniod can be senn exteriorly forming part of the eye orbits and the lateral part of the skull
- Central part of the spheniod bone is riddled with air cavities, the shpeniod sinuses
Skull: Ethmoid bone
- Very irregular Shaped
- Lies anterior to the spheniod
- Forms the roof of the nasal cavity and part of the medial wall of the orbits
- Projecting from its superior surface is the crista galli ("cocks comb")
- The outermost covering of the brain attaches to this projection
- On each side of the crista galli are many small holes
- These holey areas, the cribriform plates allow nerve fibers carrying impulses from the olfactory receptors of the nose to reach the brain.
- Holds eyes in an anterior position and allow the facial muscles to show our feelings
- Twelve are paired, only the mandible and the vomer are single.
- Maxillary bones fuse to form the upper jaw
- All facial bones except mandible join the maxillae
- Maxillae carry the upper teeth in the alveolar margin
- Extentions of the maxillae are called palatine processes form the anterior part of the hard palate of the mouth
- Contains sinuses which drain into the nasal passages
- Paranasal sinuses surrounding the nasal cavity lighten the skullbones and probably act to amplify the sounds we make as we speak
Face: Palatine Bones
- Lie posterior to the palatine processes of the maxillae
- Form posterior part of hard palate
Face: Zygomatic Bones
- Commonly referred to as cheekbones
- Aso form a goodsized portion of the lateral walls of the orbit or eye sockets
Face: Lacrimal Bones
Are fingernail sized bones forming part of the medial walls of each orbit or eye sockets
Face: Nasal Bones
Small rectangular bones forming the bridge of the nose are the nasal bones
Face: Vomer bone
- The single bone in the median line of the nasal cavitty is the vomer
- The vomer form most of the nasal septum
Face: Inferior Conchae
Thin curved bone projecting from the lateral walls of the nasal cavity
- Lower jaw
- Largest and strongest bone of the face
- Joins temporal on each side of the face
- Forms the only freely movable joint in the skull
- Horzantal part of the mandible forms the chin
- Two upright bars of bone extend from the body to connect the mandible with the temporal bone
- Lower teeth lie in the alveoli sockets in the alveolar margin
- At the superior edge of the mandibleular body
- Closely related to the mandible and temporal bones
- Unique in the fact that it is the only bone in the body that does not articulate with any other bone in the body
- Suspended in the midneck region
- Achored by ligaments to the styliod process of the temporal bones
- Horse shoe shaped with a body, and two pairs of horns.
- Serves as a movable base for the tongue and an attachment point for the neck muscles
- Infants face is small compared to the size of its cranium
- The skull as a whole is large compared to The infancts total body length
- When a baby is born the skeleton is unfinished
- Some areas of hyline cartilage still remain to be ossified, or converted to bone
- Fibrous membranes connecting to the ranial bones are called fontanels
- The rhythm of te babys pulse can be felt through these 'soft spots'
- Largest fontanels are the diamond shaped anterior fontanel and the smaller triangular shaped posterior fontanel
- Fontanels allow the fetal skull to be compressed slightly during birth
- And because they are flexible they allow the infants brain to growduring the later part of pregnancy and early infancy
Vertebral Column (Spine)
- serves as the axial support of the body and extends from the skull, which is supports, to the pelvis where it transmits the wieght of the body to the lower limbs
- 26 irregular bones connected and reinforced by ligaments in such a way that a flexible , curved structure results
- running through the central cavity of the vertebral column is the delecate spinal cord
- Birth before the spine consist of 33 separate bone, eventually nine of these fuse forming the two composite bones, the sacrum and coccyx
- of the 24 single bones the 7 vertebral of the neck are cervical vertebral, the next 12 are the thoracic vertebral, the remaining 5 support the lower back are lumbar vertebral.
- intervertebral discs: flexible fibrocartilage - cushion vertebral and absorb shocks
- young person has water filled spongy likediscsbut as they age they become harder and less compressible
- Because they become harder and less compressible older people are more suseptible to slipped discs
- if the protruding disc presses the spinal cord or the spinal nerves exiting from the card numbness and excrutiating pain can result.
- The discs and s-shaped structure or the vertebral column work together to prevent shock to the head when we walk or run.
- the spinal curvatures in thoracic and sacral regions are referred to as primary curvuratures because they are present when we are born later secondary curvuratures develop
- the cervical curvurature develops when the baby starts to lift its head, and the lumbar curvurature develops when the baby begins to walk
Abnormal spinal curvatures
- Scoliosis: curved one way or another
- Kyphosis: hump backed
- Lordosis: Butt out
- Congenital, result from disease, poor posture, or unequal muscle pull on spine
Common Features of Vertebrae
- Body or centrum: disclike, wieghtbearing part of the vertebra facing anteriorly in th vertebral column
- Vertebral arch: arch formed from the joining of all posterior extentions, the laminae and pedicles from the vertebral body
- Vertebral foramen: canal through which the spinal cord passes
- Transverse Processes: two lateral projections from the vertebral arch
- Spinous Process: single projection rising from the posterior aspect of the vertebral arch
- Superior and inferior articular processes: paired projections lateral to the vertebralforamen allowing a vetebrea to form joints with adaject vertebrae
- C1 to C7
- First two atlas and axis are different because they perform functions other cervical vertebrea dont
- The atlas has no body. The superior surfaces of its transverse processes contain large depressions that recieve the occipital condyles of the skull. This joint allows you to nod yes.
- The axis ats as a pivit for the rotation of the atlas and skull above. It has a large upright process, the odontoid process,or dens which act as the pivit piont.
- Joints inbetween allow you to indicate no.
- Typical cervical vertebrea, they are the smallest lightest vertebrea, and most often there spinous processes are short and divided into two branches.
- The transverse processes of the cervical vertrbreacontainforamina(openings) through whcih the vertebral arteries pass on there way to the brain above.
- All typical
- Larger than cervical
- Somewhat heart shapedTwo costal demifacets (articulating surfaces) on each side which recieve the heads of the ribsSpinous process is long and hooks sharply downward, causeing the vertebra to look like a giraffes head veiwed from the side
- Massive block like boduies
- Short hatchet-shaped spinous processes make them look like a moose head from the lateral acspect
- Most stress on vertebral column occurs in the lumbar regoin
- Sturdiest of the all vertebral
- Formed by the fusion of the five vertebral
- Winglike alae articulate laterally with the hip bones forming he sacrillic joints
- Sacrum forms the posterior wall of the pelvis
- Its dorsal midline surface is roughened by the median sacral crest, the fused spinous process of the sacral vertebra.
- The vertebral canal continues inside the sacrum as the sacral canal
- Formed by the fusion of three to five tiny, irregular shaped vertebral
- Sternum, ribs, and thoracic vertebrae
- Called thoracic cage because it forms a protective cone shaped cage of slender bones around organs of the thoracic cavity
- Breast bone
- Result of the fusion of three: manubrium, body, and xiphoid process.
- Attach to the first seven pairs of ribs
Sternum: Three important bony landmarks
- Jugular Notch: concave upper border of the manubrium can be palpated easily; generally it is at the level of the third thoracic vertebrae.
- Sternal Angle: results where the manubrium and body meet at a slight angle to eachother so that a transverse ride is formed at the level of the second ribs. Provides handy reference piont for counting ribs to locate the second intercostal space for listening to certain heart valves.
- Xiphisternal joint: the piont where the sternal body and xiphiod process fuse, lies at the level of the ninth thoracic vertebrae.
- Twelve pairs form the walls of the throacic cage
- All the ribs articulate with the vertebral column posteriorly and then curve downward and toward the anterior body surface
- The true ribs, the first seven pairs, attach directly to the sternum by costal cartilages
- The false ribs the next five pairs either attach indirectly to the sternum or not at all
- The last two pairs of the false ribs lack sternal attachment therefore they are called floating ribs
- Intercostal spaces are filled with the intercostal muscles that aid in breathing.