SKELETAL SYSTEMPART 2THE AXIAL SKELETON

Honors Anatomy & Physiology

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

Long Bones longer than they are wide may be slightly curved (to absorb

stress of weight at more points along the bone i.e. straight bones would fracture more easily)

consist of: shaft & variable #s of ends compact bone in diaphysis and spongy

bone in epiphysis

Long Bones

Short Bones somewhat cube-shaped nearly equal in length as width consist of:

spongy bone except @ surface

Short Bones

Flat Bones Composed of:

2 nearly parallel plates of compact bone enclosing spongy bone inside

Function: give considerable protection place for muscle attachment

Flat Bones

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

Sesamoid Bone

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 & nerves

2. processes projections or outgrowths that either

help form joints or serve as attachment points for ligaments & tendons

Bone Surface Markings

Bone Surface Markings-2

Axial skeleton

SKULL

Skull 22 bones in 2 categories:1. Cranium

8 bones that form cranial cavity1. 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

Movable Joints of the Skull1. Mandible2. Auditory Ossicles

Functions of Cranial Bones1. 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

Cranial Bones: Frontal Bone forms:

forehead upper part of eye socket most of anterior part of cranial floor in newborns: rt & lt which fuse

shortly after birth

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

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)

Occipital Bone

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

Sphenoid Bone

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

Ethmoid Bone perpendicular plate: forms superior

portion of nasal cavity superior & middle nasal conchae: (or

turbinate) increase vascular & mucous membrane surface area in nasal cavities: aids in sense of smell, warms, filters & moistens air being inhaled. Filters because the turbinates cause air to swirl as a result inhaled particles strike & become trapped in mucus

Ethmoid Bone

“Sometimes when you study anatomy, you start seeing others differently.”

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

Lacrimal Bones thin, about the size of pinky

fingernail (smallest bones of face part of medial wall of each orbit each contain lacrimal fossa that

houses lacrimal sac: gathers tears nasal cavity

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

Sutures

Newborn Skull

Newborn Skull

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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 aka spine, backbone 2/5 of person’s height 26 in adult (starts as 33, some fuse

to form sacrum & coccyx) 7 cervical 12 thoracic 5 lumbar 1 sacrum 1 coccyx

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

Intervertebral Discs

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 body

Transverse 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 Cervical Vertebrae

C-3 to C7 smaller than

other v. except coccyx but vertebral foramen largest

all cervical v. have extra foramen: 2 transverse foramen for vertebral a., v., & n.

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

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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

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

Kyphoscoliosis

THAT’S ALL FOLKS