Skeletal System-2
Honors Anatomyfor copy
Essential Question• What is the main contribution
the axial skeleton makes to homeostasis?
Divisions of the Skeleton• AXIAL SKELETON• Skull– Cranium– Face
• Hyoid• Auditory Ossicles• Vertebral Column• Thorax
• APPENDICULAR SKELETON:
• Pectoral Girdle• Upper Limbs• Pelvic Girdle• Lower Limbs
Types of Bone• bones fall into 1 of 5 main types
based on shape:– Long – Short– Flat– Irregular – Sesamoid
Short Bones• somewhat cube-shaped• nearly equal in length as width• consist of:– spongy bone except @ surface
Flat Bones• Composed of:– 2 nearly parallel plates of compact
bone enclosing spongy bone inside• Function:– give considerable protection– place for muscle attachment
Irregular Bones• complex shapes (do not fit in
other categories)• vary in amt spongy bone
Sesamoid Bones• develop w/in certain tendons
where there is considerable friction, tension, & physical stress
• function: protect tendon from excessive wear & tear
• vary in # person to person but everyone has 2 patella which develop in quadriceps femoris tendon
Sutural Bones• classified by location (w/in a
suture: a seam between 2 cranial bones)
• not everyone has them
Bone Surface Markings• 2 major types:1. depressions & openings– form joints or allow passage of
vessels & nerves2. processes– projections or outgrowths that
either help form joints or serve as attachment points for ligaments & tendons
Axial skeleton
Skull • 22 bones in 2 categories:1. Cranium– 8 bones that form cranial cavity
1. 1 frontal bone2. 2 parietal bones3. 2 temporal bones4. 1 occipital bone5. 1 sphenoid bone6. 1 ethmoid bone
Skull 2. Facial Bones
14 bones that form the face• 2 nasal bones
»2 maxillae»1 mandible»2 zygomatic»2 lacrimal»2 palantine»2 inferior nasal conchae»1 vomer
Skull: Cavities1. Cranial Cavity2. Nasal Cavity3. Orbits4. Paranasal Sinuses5. Middle & Inner Ear Cavities
Cavities of the Skull
Functions of Cranial Bones
1. protecting brain2. stabilizing position of brain,
vessels, & nerves through attachments to the meninges
3. outer surfaces provide large areas of attachment for muscles that move parts of the head & some for facial expression
Frontal Bone
Parietal Bones• form greater portion of sides &
roof of cranial cavity
Temporal Bones• form inferior, lateral aspects of
the cranium & part of the cranial floor
• its zygomatic process forms the lateral half of the zygomatic arch
• mandibular fossa: where condylar process of mandible forms TMJ (temporal mandibular joint)
Temporal Bones• external auditory meatus: ear
canal• mastoid: posterior & inferior to
external auditory meatus, contains “air cells” (mastoiditis: inflammation in air cells)
Temporal Bone: Petrous Portion
• base of skull between sphenoid & occipital bones
• houses middle & inner ear• Carotid foramen & Jugular
foramen
Temporal Bones• internal auditory meatus:
passage of Cranial nerves VII (facial n.) and VIII (vestibulocochlear n.)
• styloid process: point of attachment for muscles & ligaments of the tongue & neck
Temporal Bone: Internal Surface
Occipital Bone• forms back of head & most of
base of skull• foramen magnum: large hole
spinal cord passes thru, • occipital condyles: articulate
with 1st cervical vertebra (atlas)
Sphenoid Bone• middle base of skull• *articulates with all other cranial
bones• shape resembles a bat
Sphenoid Bone• sella turcica: (Turkish saddle)
the “seat” of the saddle is the hypophyseal fossa: where the pituitary gland sits
• optic foramen: between body & lesser wings, cranial nerve II (optic n.) and opthlamic artery pass thru
Ethmoid Bone• “like a sieve”• midline of anterior part of cranial floor,
anterior to sphenoid, posterior to nasal bones
• cribiforme plate: forms roof of nasal cavity, the holes of the sieve where olfactory nerves pass from roof of nasal cavity to brain
• crista galla: triangular process which serves as pt of attachment for meninges of brain
Facial Bones• shape of face changes
dramatically during 1st 2 yrs of life: – brain & cranial bones expand– 1st set of teeth erupt– paranasal sinuses enlarge– growth of face stops ~16 years old
Facial Bones• 14 facial bones:1. 2 nasal bones2. 2 maxillae3. 2 zygomatic bones4. 1 mandible5. 2 lacrimal bones6. 2 palatine bones 7. 2 inferior nasal conchae8. 1 vomer
Nasal Bones• form part of the bridge of the
nose (rest is cartilage)
Maxillae• = upper jaws• *articulate with every bone in face
except the mandible• form part of floor of orbits, parts of
nasal cavity, & most of the hard palate (bony roof of mouth)
• each one has large maxillary sinus• alveolar process is small arch that
contains the alveolar sockets for upper set of teeth
Cleft Palate & Cleft Lip• 10-12 wks gestation the palatine
processes of maxillae typically join
• not doing so cleft palate +/- cleft lip– speech & swallowing can be
affected–many ear infections– reparative surgery recommended
1st few wks of life / surgery needs to be completed by 12 – 18 mos b/4 speech: speech therapy & orthodontic care frequently necessary
Zygomatic Bones• “cheekbones”:
the temporal process of the zygomatic bone articulates with the zygomatic process of the temporal bone
• also part of floor of orbit
Inferior Nasal Conchae• inferior to the middle nasal
conchae of the ethmoid bone forming part of lateral wall of nasal cavity
• same function as superior & middle conchae: swirling inhaled air to deposit particulates but not involved in sense of smell
Vomer • Δ shaped bone on the floor of
nasal cavity forming inferior portion of nasal septum
Mandible • largest & strongest facial bone
(lower jaw)• alveolar processes hold lower
teeth sockets• mental foramen: dentist numb
mental nerve
Sutures • an immovable joint in an adult
found only between skull bones & holds most skull bones together
• name generally reflects bones they unite
Hyoid Bone • “U-shaped “• *does not articulate with any other bone
in skeleton• suspended by ligaments from styloid
process of temporal bone• in anterior neck between mandible &
larynx• function: supports tongue• *frequently fractured during
strangulation
Hyoid Bone
Vertebral Column• Fetus has
anteriorly concave curve
• 3 mos old when holds head cervical curve develops
• lumbar curve develops as infant sits up, stands, walks
Intervertebral Discs• between bodies of consecutive
vertebra– under compression they flatten &
broaden– harden, less elastic w/aging &
narrow loss of height• annulus fibrosus: outer fibrous
ring• nucleus pulposus: inner soft,
highly elastic
Parts of a Vertebra• Body– thicker, anterior portion, weight bearing
portion• Vertebral Foramina– contains spinal cord, adipose, areolar CT,
blood vessels• Spinous Process– 1 of 7 processes, posterior, palpable on
back of bodyTransverse Processes: on each side,
extending laterally
Vertebrae: 1st & 2nd Cervical
• Atlas– ring-shaped– articulates with
condyles of occipital bone
– allows you to nod head “yes”
• Axis – 2nd cervical v.– allows you to
shake head “no”
Typical Thoracic Vertebrae
• T-1 to T-12• larger &
stronger than cervical v.
• distinguishing feature: articulate with ribs (facets on transverse processes of T-1 to T-10
Typical Lumbar Vertebrae
• L-1 to L-5• largest &
strongest of the vertebrae
• processes are short & thick
Sacrum • triangular bone
formed by union of S-1 to S-5
• fusion begins ~16, complete by age 30
• female: shorter, wider, more curved S-2 to S-3
Coccyx• small triangle• formed by fusion
of 4 coccygeal v. (Co-1 to Co-4), start between 20 & 30
• females points inferiorly; males it points anteriorly
Thorax• refers to entire chest• skeletal part of thorax is thoracic
cage– Sternum– Ribs
Sternum• aka “breastbone”• flat bone in center of anterior
thorax• 3 bones that fuse by age 25
Sternum1. Manubrium• superior portion• suprasternal notch• clavicular notches• articulates with
costal cartilage of 1st & 2nd rib
• sternal angle: where it articulates with body
Sternum2. Body• middle & largest
portion• articulates with
costal cartilage of 2nd thru 10 ribs
Sternum 3. Xiphoid Process• cartilagenous in
infancy • not completely
ossified until ~age 40
• avoid it during CPR
Ribs: 12 Pair
• increase in length 1st thru 7th then decrease in length to 12th
• 1st thru 7th ribs (true ribs) have direct anterior attachment to sternum by strip of hyaline cartilage which contribute to elasticity of thoracic cage
• 8th thru 10th ribs attach to each other & then to cartilages of 7th rib
• 11th & 12th ribs: floating ribs
Ribs• all 12 attach posteriorly to
vertebrae• Parts of a Rib1. Head2. Neck3. Tubercle 4. Body 5. Costal Angle
Abnormal Curvatures of Spine
• Scoliosis • lateral bending• usually in
thoracic region
Abnormal Curvature of Spine
• Kyphosis • exaggeration of
the thoracic curve
• seen in TB of spine, congenital malformation, elderly