HumanA&P 8: Axial Skeleton

3 Major Regions & Number of Bones in Axial Skeleton

1. Skull

2. Vertebral Column

3. Thoracic Cage

80 Bones

Articulation Bone Marking

• Where 2 bones meet

• Knee joint

Head Bone Marking

• Prominent round surface

• Head of femur

Facet Bone Marking

• Flat surface

• Vertebrae

Condyle Bone Marking

• Rounded surface

• Occipital Condyles

Projection Bone Markings

• Raised markings

• Spinous process of vertebrae

Protuberance Bone Marking

• Protruding

• Chin

Process Bone Marking

• Prominence feature

• Transverse process of vertebrae

Spine Bone Marking

• Sharp process

• Ischial spine

Tubercle Bone Marking

• Small, rounded process

• Tubercle of humerus

Tuberosity Bone Marking

• Rough surface

• Deltoid tuberosity

Line Bone Marking

• Slight, elongated line

• Temporal lines of the parietal bones

Crest Bone Marking

• Ridge

• Iliac crest

Hole Bone Marking

• Holes & depressions

• Foramen

Fossa Bone Marking

• Elongated basin

• Mandibular fossa

Fovea Bone Marking

• Small pit

• Fovea capitis on the head of femur

Sulcus Bone Marking

• Groove

• Sigmoid sulcus of temporal bone

Canal Bone Marking

• Passage in bone

• Auditory canal

Fissure Bone Marking

• Slit through bone

• Auricular fissure

Foramen Bone Marking

• Hole through bone

• Foramen magnum in the occipital bones

Meatus Bone Marking

• Opening into canal

• External auditory meatus

Sinus

• Air filled space in bone

• Nasal sinus

2 Sets of Skull Bones

1. Cranial Bones

2. Facial Bones

Cranial Bone Functions

• Enclose brain in cavity

• Provides attachment sites for muscles

Facial Bone Functions

• Framework of face

• Cavities for organs

• Openings for air/food

• Secure teeth

• Anchor muscles

Sutures

• Immoveable joint between cranial bones

Cranial Vault

• Forms superior aspect of cranial cavity

Cranial Base

• Forms inferior aspect of skull

• Divided into anterior, middle & posterior fossae

• Brain sits within fossae

Other Cranial Cavities

• 85 named openings

• Middle/external ears

• Nasal

• Orbits

8 Cranial Bones

• Frontal Bone

• Parietal Bones (2)

• Occipital Bone

• Temporal Bones (2)

• Sphenoid Bone

• Ethmoid Bone

14 Facial Bones

• Mandible

• Maxillary Bones (2)

• Zygomatic Bones (2)

• Nasal Bones (2)

• Lacrimal Bones (2)

• Palatine Bones (2)

• Vomer Bone

• Inferior Nasal Conchae (2)

Cranial Bone Sutures

Foramen Magnum

Large hole that spinal cord passes through to enter vertebral cavity

4 Cavities of the Skull

1. Cranial

2. Orbit

3. Nasal

4. Oral

Cranial Cavity

• Surrounds brain

• Formed by 8 cranial bones

Orbit Cavity

• Houses eyeball, nerves, blood vessels & muscles

• 7 Bones

Nasal Cavity

• First part of respiratory tract

• Formed by several bones with mucous membranes

Oral Cavity

• First part of GI tract

• Houses:

  • teeth

  • tongue

  • other structures

• Roof is hard palate

• Anterior & lateral walls formed by maxillae & mandible

• Floor/posterior are soft tissues

Temporal Bone

• Squamous part

• Petrous Part

• Tympanic Part

Sphenoid Bone

• Hypohyseal fossa of sella turcica

  • Saddle like

Ethmoid Bone

• Deepest skull bone

• Cribriform Plates: superior part

• Crista Galli: Triangular process, dura mater

• Perpendicular Plate: superior part of nasal septum

  • superior & middle nasal conchae

• Orbital Plates: contribute to medial orbits

Mandible

• Largest, strongest facial bone

• Made up of body and 2 rami

Maxillary Bones

• Medially fused to form upper jaw & central facial skeleton

Palatine Bones

• L shaped bones made from 2 bony plates

Vomer

• Plow shaped bone

• Forms part of nasal septum

Inferior Nasal Conchae

• Paired bones that form part of nasal cavity

• Largest of 3 pairs of conchae

Hyoid Bone

• Anterior neck

• Only bone that does not articulate directly to another bone

• Movable base for tongue

• Attachment site for muscles

Vertebral Column General Characteristics

• 26 vertebrae

• ~28” long

• 5 regions

• 4 curves

5 Major Vertebral Regions

1. Cervical: 7 vertebrae

2. Thoracic: 12 vertebrae

3. Lumbar: 5

4. Sacrum: 1 bone made of several fused bones, at the hip

5. Coccyx: Fused bones the form terminus of column

4 Main Vertebral Curves

1. Cervical: Concave posteriorly

2. Lumbar: Concave posteriorly

3. Thoracic: Convex posteriorly

4. Sacral: Convex posteriorly

Vertebrae General Structure

• Body: anterior region

• Vertebral Arch:

  • 2 Pedicles

  • 2 Laminae

• Vertebral Foramen: enclosure formed by body & arch

• Vertebral Canal: series of foramina

• Intervertebral Foramina: lateral openings between vertebrae

7 Vertebral Processes

• Spinous Processes: posteriorly

• Transverse Processes: laterally

• Superior Articular Process: superiorly

• Inferior Articular Process: Inferiorly

Cervical Vertebrae

• Concave

• C1 - C7

Thoracic Vertebrae

• Convex

• T1 -T12

Lumbar Vertebrae

• Concave

• L1 - L5

Vertebrae Comparison

Vertebral Ligaments

• Support vertebral column

• Anterior & posterior longitudinal

  • continuous bands from neck to sacrum

• Supraspinous Ligament

  • interconnects spinous processes of thoracic & lumbar vertebrae

  • nuchal ligament at neck

• Ligamentum Flavum

  • connects adjacent vertebrae

  • provides support during forward bending

Intervertebral Discs

• Cushion-like pad between vertebrae

• Shock absorbers

• 2 Parts:

  • Nucleus Pulposus: Inner gelatinous nucleus

  • Anulus Fibrosis: outer collar of collagen & fibrocartilage

Sacrum

• Triangular bone shapes posterior wall of pelvis

• 5 Fused vertebrae

• Superior articular process articulates with L5

• Auricular Surfaces articulate with coccyx & hip forming sacroiliac joints

• Anterior Sacral Foramina: lateral ends of ridges

Coccyx

• Tailbone formed of 3-5 fused vertebrae

• Articulates with sacrum

Thoracic Cage

• Composed of:

  • Vertebrae

  • Sternum & costal cartilages

  • Ribs

• Functions:

  • Protection

  • Supports shoulders

  • Attachment sites for muscles

Sternum

• 3 Fused bones

  • Manubrium: superior with clavicular notches

  • Body: midportion

  • Xiphoid Process: inferior site of muscle attachment

    • not ossified till 40

Ribs

• Main parts:

  • Shaft: flat bone, most of rib

  • Head: articulates with facets on 2 adjacent vertebrae

  • Neck: constricted portion beyond head

  • Tubercle: knoblike structure later to neck