Skeletal System: Axial Skeleton Flashcards
Skull
22 bones
Auditory Ossicles
6 bones
Hyoid Bone
1 bone
Vertebrae
26 bones
Thorax: Sternum and Ribs
25 bones
What is an Axial Skeleton composed of?
Skull, Auditory Ossicles, Hyoid Bone, Vertebrae, and Thoracic Cage
What is the total number of Axial Bones?
80
Bone Markings
reference for functionality of a certain bones
Articulating
attaches or articulates itself to another bone structure
What are the 3 Articulating bones?
Head, Condyle, and Facet
Head
- enlarged end
- found mostly in the long bones
Condyle
smooth rounded articular surface
Facet
smooth flattened surface
Non-Articulating
- do not attach bones
- attachment to muscles, nerves, and blood vessels
What are the 5 non-articulating bones?
Tuberosity, Process, Crest, Tubercle, and Line
Tuberosity
knob or enlargement
Process
prominent projection
Crest
prominent ridge or curvature
Tubercle
- bump
- small rounded projections
Line
embedded on bone surface
What are the 5 depression and opening bones?
Fossa, Foramen, Meatus, Fissure, and Sinus
Fossa
- depression
- where articulating bones attach
- houses body structures and glands
Foramen
- opening or hole
- passageway of veins and arteries
Meatus
tunnel-like opening
Fissure
cleft
Sinus
- cavity
- spaces mostly located in skull
Calvarium
- also known as cranium
- superior aspect
- step of 8 (sphenoid, temporal (2), ethmoid, parietal (2), occipital, and frontal)
Frontal bone
- forms the forehead
- superior part of orbits and most of anterior cranial fossa
- contains sinuses
Squamous
- forehead
- most anterior part of frontal area
Supraorbital Margin
- thickened part which lies under eyebrows
- where the forehead ends
Supraorbital Foramen
- passageway of the supraorbital artery (eyesight) and nerves
Glabella
- region between supraorbital margin and supraorbital foramen
- serves as a landmark for radiographic positioning
Parietal bone
- location: superolateral
- forms most of the superior and lateral aspects of the skull
Sutures
- wormian bones
- interlocking joints of skull
Coronal Suture
parietal - frontal
Lambdoid Suture
parietal - occipital
Squamosal Suture
parietal - temporal
Sagittal Suture
- interparietal
- parietal - parietal
Temporal Bone
- below parietal bone
- forms inferolateral aspects of the skull
- contribute to the middle cranial fossa
- best viewed on lateral position
Zygomatic Process
contributes to the formation of cheek bones
Zygomatic Arch
- zygomatic process of temporal bone meets zygomatic bone forming an arch
Zygoma
facial bone
Temporomandibular Joint (TMJ)
condylar process where the mandible articulates with mandibular fossa
Condylar Process
temporal; unstable
Mandibular Process
frontal; stable
External Auditory Meatus (EAM)
- where sound enters the ear, enables soundwaves to reach eardrum
Petrous
- much inferior
- thickest
- deep seated
- houses the middle and internal ear cavities
Foramen of Petrous
small structure
Middle Cranial Fossa
supports temporal brain
Jugular Foramen
- most lateral foramen
- passageway of jugular vein
Carotid Canal
- anterior to jugular foramen
- transmits internal carotid artery into cranial cavity
Foramen Lacerum
- between petrous temporal and sphenoid
- most medial portion
- prone to tearing
Internal Acoustic Meatus
transmits cranial nerves 7 and 8
Foramen Rotundum
maxillary nerve = passageway
Foramen Ovale
mandibular nerve = passageway
Foramen Spinosum
- middle meningeal artery and vein
- nervous spinosus
Mastoid Process
- lump behind ear
- acts as an anchoring site for some neck muscles
- functions as attachment of neck muscles
Mastoid Air Cells
- has lots of air cavities
- provides functions for sound resonance and thermoregulation
Styloid Process
needle-like process for neck muscle and tongue muscle attachment
Occipital Bone
forms most of skull’s posterior wall and base
Posterior Cranial Fossa
supports cerebellum
Foramen Magnum
largest foramen of the skull where spinal cord passes through
Occipital Condyles
located on each lateral side of foramen magnum where C1 articulates
External Occipital Protuberance
most bulging part of the posterior skull
Sphenoid Bone
- bat-shaped
- keystone because it acts as a central wedge
Body
forms the center of the sphenoid bone
Hypophyseal Fossa of the Sella Turcica
houses pituitary gland
Pituitary Gland
part of endocrine system
Lesser wing
- medial process
- horn-like
Greater wing
projects laterally
Pterygoid process
- interior portion
- serves as attachment for pterygoid muscle for chewing
Ethmoid Bone
- complex shape like sphenoid
- helps form the anterior cranial fossa
- forms part of nasal septum and lateral walls and roofs of nasal cavity
- contributes to medial wall of orbit
Cribiform Plate
flat plates that helps form root of nasal cavity and floor of anterior cranial fossa
Crista Galli
dura mater of brain is attached here, which secures brain in the cranial activity
Perpendicular Plate
- inferior portion
- divides nasal cavity from right to left
- visible from outside of skull
What is the Cranial Base composed of?
Vomer, Inferior Nasal Conchae (2), Nasal (2), Maxilla (2), Mandible, Palatine (2), Zygoma (2), and Lacrimal (2)
Mandible
- lower jaw bone
- forms chin and anchors lower teeth
- largest and strongest bone of the face
- condylar process
- mandibular foramen
- mental foramen
Ramus
meets central body for chin formation
Mandibular Angle
between ramus and body of mandible
Mental Foramen
houses nerves for tooth sensation
Maxilla
- upper jaw bone and parts of hard plate, orbits, and nasal cavity walls
- contains maxillary sinus
Maxillary Sinus
largest paranasal sinus
Zygoma
forms cheeks and parts of the orbits
Articulation of Zygoma
Maxilla, Frontal, and Temporal
Nasal
forms bridge of nose
Articulation of Nasal
Frontal, Maxilla, and Perpendicular plate
Lacrimal Bone
- fingernail-shaped structure
- forms part of medial orbit wall
- serves as passageway for tears to drain from the eye surface to nasal cavity
Deep Groove
- each lacrimal bone contains this
- helps for the lacrimal fossa
Lacrimal Fossa
houses lacrimal sac
Palatine
forms posterior part of hard plate and small part of nasal cavity and orbit walls
Horizontal Plates
- joined at median palatine suture
- complete the posterior portion of hard plate
Perpendicular Plates
form part of posterolateral walls of nasal cavity and small parts of orbit
Vomer
- slender, plow-shaped, lies in the nasal cavity
- forms part of nasal septum
Inferior Nasal Conchae
- paired inferior nasal conchae are thin, curved bones in nasal cavity
- projets medially from lateral walls of nasal cavity, just inferior to middle nasal conchae of ethmoid bone
Hyoid Bone
unique as it is the only bone of the body that does not articulate with any other bone
Auditory Ossicle
three bones in middle ear that are amongst the smallest bones in the human body
What are the 3 bones in the middle ear?
Malleus, Incus, and Stapes
Malleus
hammer
Incus
anvil
Stapes
- stirrup
- smallest among all bones
Vertebral Column
- backbone
- 33 bones (infant)
- 26 bones (adult)
What are the 5 regions of vertebral column?
Cervical (7), Thoracic, (12), Lumbar (5), Sacral (1-5); 5 for children = fused, and Coccygeal (1-4); 4 for children = fused
General Structures
each vertebra consists of a body, or centrum = anteriorly and a vertebral arch = posteriorly
Laminae
flattened plates that fuse in median plane, complete the arch posteriorly
Pedicles
hort bony pillars projecting posteriorly from vertebral body, forms sides of arch
What are the 3 types of processes?
Spinous process, Transverse process, Superior and Inferior articular facet
Spinous process
median posterior projection arising at junction of two laminae
Transverse process
extends laterally from each side of vertebral arch
Superior and Inferior Articular Facet
protrude superiorly and inferiorly respectively from the pedicle - lamina junction
Facets
bone markings
What are the 4 types of curves?
Cervical lordosis, Thoracic kyphosis, Lumbar lordosis, and Sacral kyphosis
Cervical Lordosis
Concave
Thoracic Kyphosis
Convex
Lumbar Lordosis
Concave
Sacral Kyphosis
Convex
C1
- atlas
- body: none
- spinous process - none
- has superior articular facets
- “YES” (nodding)
C2
- axis
- not as specialized as atlas
- unique feature: knoblike dens
- “NO”
Dens
allows rotational movement side to side
C3-C7
- body: oval
- spinous process: short and bifid
- vertebral foramen = triangular
- C7 - palpable (vertebra prominens)
Bifid
- has clefts or partition
What are the 3 types of joints formed?
Atlanto-occipital joint, Atlanto-axial joint, and Zygapophyseal joint
Atlanto-occipital joint
Atlas + Occipital condyles
Atlanto-axial joint
Atlas + Axis
Zygapophyseal joint
superior articulating facet + inferior articulating facet
T1-T12
- body: heart shaped
- spinous process = long and sharp
- demifacets (costal facets)
- transverse process (Y)
- vertebral foramen = round
- ribcage articulation
L1-L5
- body: massive kidney-shaped
- spinous process = short and flat
- pedicles and laminae = thicker and shorter
- transverse process (T)
- vertebral foramen = triangular
Thoracic Cage
- 25 bones
- protects the vital organs in thorax
what are the elements of the thoracic cage?
Thoracic vertebrae, Ribs, Sternum and Costal cartilages
Thoracic vertebrae
posteriorly
Ribs
laterally
Sternum and Costal Cartilages
anteriorly
What are the joints formed in the thoracic cage?
Costovertebral joints, Costochondral joints, Sternochondral joints, and Interchondral joints
Costovertebral joints
Ribs + Vertebrae
Costochondral joints
Ribs + Costal cartilages
Sternochondral joints
- Sternum + Costal cartilages
Interchondral joints
False ribs costal cartilages
Sternum
- breastbone
- lies in the anterior midline of the thorax
- superior portion = manubrium
- inferior protion = xiphoid process
Ribs
- 24 bones
- 12 pairs
True Ribs
7 pairs (1-7)
False Ribs
5 pairs, last two ribs: floating ribs (8-12)
8-10
attached to cartilages of true ribs
11-12
floating ribs