SKELETAL SYSTEM PART 2 THE AXIAL SKELETON Honors

SKELETAL SYSTEM PART 2 THE 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 1. 2 major types: depressions & openings � 2. form joints or allow passage of vessels & nerves 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 1. 22 bones in 2 categories: Cranium 8 bones that form cranial cavity � 1. 2. 3. 4. 5. 6. 1 frontal bone 2 parietal bones 2 temporal bones 1 occipital bone 1 sphenoid bone 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: Cavities 1. 2. 3. 4. 5. Cranial Cavity Nasal Cavity Orbits Paranasal Sinuses Middle & Inner Ear Cavities

Cavities of the Skull

Movable Joints of the Skull 1. 2. Mandible Auditory Ossicles

Functions of Cranial Bones 1. 2. 3. protecting brain stabilizing position of brain, vessels, & nerves through attachments to the meninges 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 1 st 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 1 st 2 yrs of life: � brain & cranial bones expand � 1 st set of teeth erupt � paranasal sinuses enlarge � growth of face stops ~16 years old

Facial Bones 1. 2. 3. 4. 5. 6. 7. 8. 14 facial bones: 2 nasal bones 2 maxillae 2 zygomatic bones 1 mandible 2 lacrimal bones 2 palatine bones 2 inferior nasal conchae 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 1 st 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

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 vessels spinal cord, adipose, areolar CT, blood Spinous Process � 1 of 7 processes, posterior, palpable on back of body Transverse Processes: on each side, extending laterally

Vertebrae: st 1 & Atlas � ring-shaped � articulates with condyles of occipital bone � allows you to nod head “yes” Axis � 2 nd cervical v. � allows you to shake head “no” nd 2 Cervical

Typical Cervical Vertebrae C-3 to C 7 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

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

Sternum 1. Manubrium superior portion suprasternal notch clavicular notches articulates with costal cartilage of 1 st & 2 nd rib sternal angle: where it articulates with body

Sternum 2. Body middle & largest portion articulates with costal cartilage of 2 nd 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 1 st thru 7 th then decrease in length to 12 th 1 st thru 7 th ribs (true ribs) have direct anterior attachment to sternum by strip of hyaline cartilage which contribute to elasticity of thoracic cage 8 th thru 10 th ribs attach to each other & then to cartilages of 7 th rib 11 th & 12 th ribs: floating ribs

Ribs

Ribs 1. 2. 3. 4. 5. all 12 attach posteriorly to vertebrae Parts of a Rib Head Neck Tubercle Body 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

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