The Axial Skeleton

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Skeletal system includes both:  Axial skeleton  Skull  Vertebral column  Thoracic cage  Appendicular skeleton  Pectoral and pelvic girdles  Upper and lower limbs 2

The Skull

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The cranium 

Cranial vault or calvaria

 Superior, lateral, and posterior walls of the skull 

Cranial floor or base

 Anterior fossa  Middle fossa  Posterior fossa 4

The skull  Consists of the

cranium

and the

bones of the face



Sutures

 Lambdoid-between occipital and parietal bones  Coronal-between parietal and frontal bones  Sagittal-between parietal bones  Squamous-between parietal and temporal bones 5

The skull

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The skull

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The skull

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Cranial Bones

 one occipital bone  foramen magnum  two parietal bones  one frontal bone  frontal sinuses  glabella  two temporal bones  auditory ossicles  one sphenoid  one ethmoid 9

The Sectional Anatomy of the Skull

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The Sectional Anatomy of the Skull

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The Occipital and Parietal Bones

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Occipital and Parietal Bones 

Occipital bone

 Foramen magnum  Occipital condyle  External occipital protuberance 

Parietal bone



Frontal bone

 Supraorbital foramen  Glabella 13

Frontal bone

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Temporal bone

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Temporal bone  Squamous suture  Zygomatic process  Zygomatic arch  Mandibular fossa  External auditory meatus  Styloid process 16

Temporal bone is divided in regions  Mastoid process  Mastoiditis  Meningitis  Stylomastoid foramen  Passage for cranial nerve VII  Internal acustic meatus  Passage for cranial nerves VII and VIII 17

The Sphenoid

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Sphenoid bone  Greater wings  Sella turcica  For the pituitary gland 19

The Ethmoid

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Ethmoid bone  Crista galli  Attachment of the dura mater  Cribiform plate  Passage of olfactory nerves 21

Ethmoid bone  Perpendicular plate  Forms the superior part of the nasal septum  Superior and middle nasal conchae (turbinates)  Covered by mucosa  Warms and humidifies the air 22

Facial bones

 Maxillary bones  Mandible  Palatine bones  Nasal bones  Vomer  Inferior nasal conchae  Zygomatic bones  Lacrimal bones 23

Maxillae  Alveolar margim  Palatine process- anterior hard palate  Incisive fossa- passage for nerves and blood vessels 24

Maxillary bone

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Vomer, Zygomatic and Lacrimal bones  Zygomatic bone  articulates with zygomatic process of temporal bone forming the zygomatic arch 26

Facial bones

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Mandible  Body- horizontal portion  Ramus-vertical portion  Mandibular condyle- articulates with temporal bone  Coronoid process  Angle  Alveolar margin- with sockets for the teeth  Mandibular foramen – site of Novocain injection 28

The mandible

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The Mandible and

Hyoid Bones

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Cranial Foramens to identify  External view: 

Supraorbital foramen

-for blood vessels and nerves 

Infraorbital foramen

-blood vessels and nerves 

Mental foramen

-blood vessels and nerves 

Stylomastoid foramen

nerve VII 

Carotid canal

-for carotid artery 

External auditory meatus

-leads to eardrum 

Incisive fossa

-for blood vessels and nerves 31

Cranial Foramens to identify  Internal view 

Optic canal

-for optic nerve 

Superior and inferior orbital fissure

 “ROS” 

R otundum

- for a branch of V 

O vale

-for a branch of V 

S pinosum

-for middle meningeal artery 32

Cranial Foramens to identify 

Foramen lacerum

-internal carotid 

Jugular foramen

cranial nerves -for jugular vein; IX, X,XI 

Internal acustic meatus

-for VII,VIII 

Hypoglossal canal

-for XII 

Foramen magnum

-for spinal cord 33

The Fetal Skeleton

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Fontanels  Anterior or frontal  Palpable for the first 1 ½ to 2 years of age  Posterior of occipital  Closes by the end of the first year of age  Mastoid  Closes by the end of the first year of age  Sphenoid  Closes by the end of the first year of age 35

Cranial bones  Frontal  It is parted  Temporal  It is incompletely ossified  Presence of ossification centers  Conical protusions on the cranial bones 36

The Vertebral Column

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Vertebral column  7 cervical vertebrae  12 thoracic vertebrae  5 lumbar vertebrae  5 sacrum fused vetebrae  3-5 fused coccyx vertebrae 38

Vertebral column  Intervertebral discs- pads of fibrocartilage between the vertebrae  Nucleus pulposus- central soft region  Annulus fibrosus- outer ring. Collagen fibers  Herniated disc- protusion of the nucleus pulposus 39

Spinal curvatures

Spinal curvatures  Four spinal curves- posterior view  Primary curvatures – present at birth  Thoracic - convex  Sacral- convex  Secondary curvatures – develops after birth  Cervical- concave  Lumbar- concave 41

Abnormal Curvatures of the Spine 42

Structure of a typical vertebra  Body- rounded portion. Anterior part  Vertebral Foramen-for the spinal cord  Transverse process  Spinous process-single and posterior  Intervertebral foramina-it is seen when 2 vertebras are put together. Passage of the spinal nerves 43

Cervical vertebra  Transverse foraminas- only present in cervical vertebrae  Atlas or C1  No body  Join with the head and provides for range of motion (when you nod yes) 44

Cervical vertebra  Axis or C2  Odontoid process or dens-allows rotation of the head (when you nod no) 45

Thoracic vertebrae  Spinous process-long and downward  Rib facet – for articulation with 1 rib 46

Lumbar vertebrae  Massive body  Short and thick and more horizontal spinous processes  No rib facets  No transverse foramem  Superior and inferior articular processes 47

Sacrum  Medial sacral crest-remnant of the spinous processes  Alae- formed by fusion of the transverse processes. It articulates with the hip bones  Sacral foramina- passage for blood vessels and nerves  Sacral canal- continuation of the verterbral canal 48

Sacrum and coccyx  Sacral hiatus-inferior opening of the sacral canal  Sacral promontory- rim on the anterior and superior part of the sacrum  Coccyx  Attached to the sacrum by ligaments 49

The bony thorax  Sternum  Manubrium-articulates with the clavicle  Body  Xiphoid process-inferior end. Made of hyaline cartilage in children and is ossified in adults  Jugular notch  Sternal angle-between the body and the manubrium 50

The ribs  Tubercle – is inferior  Costal groove –depression along the inferior side  Sternal end-articulates with sternum 51

Types of ribs  True  Ribs 1-7  Attached to the sternum through their own cartilage 52

Types of ribs  False  8-12  8-10 are vertebrochondral ribs  Attaches to the sternum indireclty through the cartilage of the C7  11-12 are floating ribs  No attachment to the sternum 53