skeletal system-2

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

Ethmoid Bone

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

Maxillae

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

Newborn Skull

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