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Axial Skeleton
The Cranium
Characteristics of the Human Skull
• Made up of 22 bones
• Except for the mandible, all of the bones are held together by sutures•Rigid articulations permitting very little movement
Coronoid process – mandibleADD THIS
Characteristics of the Human Skull
• The neurocranium includes 8 bones•1 frontal 2 parietals•1 occipital 2 temporals•1 sphenoid 1 ethmoid
• The hyoid bone (supports the tongue) does not articulate with any other bones
Mental Foramen
Characteristics of the Human Skull
• Sinus Cavities•Several of the bones have developed air spaces that are lined with mucous membranes
• It is this mucous membrane that becomes infected in sever cases of sinusitis
• It is also irritation of the mucous membrane that results in excessive fluid production that can fill the air spaces and give you a stuffy nose feeling.
Characteristics of the Human Skull
• Since these sinuses are embedded in bone, they cannot be seen easily on regular skull preparations and usually require sawing into the bone to see them.
• Some believe that the function of the sinuses are: • 1) makes the skull lighter to carry around• 2) serve as resonating chambers during
speech
Cranial Development• Formed by intramembranous and endochondral
ossification
• Intramembranous (dermal) ossification• The skull roof• Sides and roof of the neurocranium
• Endochondral ossification• Temporal bones• Occipital• Sphenoid• Ethmoid
Cranial Development
• The cranium changes rapidly during fetal development
• The 1st trimester is crucial for development of skull defects
• At birth, the skull is made up of 44 separate bony elements
Pathology
• The skull normally protects the brain from damage•The skull is one of the least deformable substances found in nature
• Head injuries can raise intracranial pressure•Subdural hematoma - Concussions•No space for the brain to expand•Brain damage or death
Sexual Dimorphism of Skulls
• Male skulls tend to be more robust• Female skulls are lighter and smaller
• The male body is larger than the female body, so proportionally the male skull is about the same size as the female skull
• Males – more prominent supraorbital ridges, more prominent temporal lines, squarer orbits, squarer chins and thicker mandibles
Axial SkeletonThe Cranium Review
(Teeth & Ears)
Skull Bones Review
Mental Foramen
The Teeth
• Human teeth show a morphology mainly differentiated by:•1. The SHAPE of their upper surface = crown•2. The NUMBER of tooth roots•3. The PURPOSE of each tooth type• Cutting• Shredding•Grinding
The Teeth
The Teeth
• Incisors•Cutting teeth•8 incisors•Very front of the mouth•Rather flat surfaces•A straight sharp horizontal edge for cutting and biting•1 long conical root
The Teeth• Canines•4 canines•Very strong, pointed corner teeth•Used for tearing and shredding•Larger and stronger than the incisors•Upper canines are sometimes called “eyeteeth”•1 single root
The Teeth
• Premolars•8 premolars•Used for chewing food•Placed lateral to & behind the canine teeth•Flat upper surface•1-2 roots•Crown has 2 cusps
The Teeth
• Molars•12 molars•Back of the mouth•Large and flat upper surface•2-4 roots•Largest of the permanent teeth•Used for final chewing and grinding before swallowing•3rd molars = Wisdom teeth
The Auditory Ossicles
• 3 smallest bones in the body• Ossicles mean “tiny bones”• Contained within the middle ear space • Serve to transmit sounds from the air
• In order from the eardrum to the inner ear (superficial to deep)•1. Malleus•2. Incus•3. Stapes
The Auditory Ossicles
• Malleus – Hammer•Articulates with the incus and is attached to the eardrum (or tympanic membrane)
• Incus – Anvil•Connected to the other ear bones
• Stapes – Stirrup•Articulates with the incus
The Auditory Ossicles
Malleus – aka Hammer
Incus – aka Anvil
The Auditory Ossicles
Stapes – aka Stirrup
The Auditory Ossicles
The Vertebral Column
The Vertebral Column• Major Functions•Cervical (7) – Support the weight of the head and trunk
•Thoracic (12) – Protect spinal cord
•Lumbar (5) – Allow spinal nerves to exit spinal cord
•Sacral – Site for muscle attachment
The Vertebral Column
• Abnormalities•Scoliosis• Lateral curvature of spine (usually inchildren)
The Vertebral Column
• Abnormalities•Lordosis• Exaggerated anterior curve of lumbar spine • Barrel chest
The Vertebral Column
• Abnormalities•Kyphosis• Exaggerated posterior curve of thoracic spine •Humpback
The Vertebral Column
• Each bone consists of:•A body•An arch•Several processes
The Vertebral Column• Body •Weight bearing portion
• Vertebral arch•Surround vertebral foramen•Formed from joining laminae and pedicales
• Vertebral foramen•All form the vertebral canal = spinal cord
The Vertebral Column
BODY
ARCH
Foramen
The Vertebral Column
• Transverse Process• Extends laterally from each side of the arch between the pedicle and lamina
• 2 Laminae•Extend from transverse processes to spinous process
The Vertebral Column
• Transverse Process
• 2 Laminae
The Vertebral Column• Articular Processes•Where vertebrae articulates with each other
• Spinous Process•Extends dorsally from 2 laminae
The Vertebral Column
• Articular Processes
• Spinous Process
The Vertebral Column
• Intervertebral discs•Dense fibrous connective tissue•Drying along with the weakening of ligaments of the vertebral column• Predisposes older
people to herniated discs • “Slipped discs”
The Vertebral Column
• Cervical - 7•1st – Atlas• “Yes” motion•No body
•2nd – Axis• “No” motion
The Vertebral Column
• Cervical•Small bodies•Each transverse process has transverse foramen•Whiplash – hyperextension of the cervical vertebrae
The Vertebral Column
• Thoracic - 12•Long, thin spinous processes•Articulates with the ribs
The Vertebral Column
• Lumbar - 5•Large, thick bodies•Heavy rectangular transverse and spinous processes•Sturdiest of the vertebrae
The Vertebral Column
• Sacrum•Alae – wings•Articulates with the hip bones•5 fused vertebrae
The Vertebral Column• Coccyx•Tailbone•Usually 4 fused vertebrae•Very reduced bodies•No foramina or processes
The Rib Cage (Bony Thorax)
The Bony Thorax
• The Rib Cage•Bony and cartilaginous structure•Supports the pectoral girdle•Provides attachments for the muscles of the neck, thorax, upper abdomen and back•Consists of • 24 ribs• The sternum• 12 thoracic vertebrae
The Bony Thorax• The rib parts:•Head – end of the rib closest to the vertebral column
•Neck - is the flattened portion which extends laterally
•Tubercle - articulates with the transverse process
•Angle – bending portion
The Bony Thorax• Manubrium • The broad, upper part of the sternum• Articulates with the clavicles and first 2 ribs
• Body• The lengthier and narrow part of the sternum• Below the manubrium
The Bony Thorax• Xiphoid Process• Small cartilaginous process of the lower sternum• Ossified in adults
• Costal Cartilage• Bars of hyaline cartilage• Push ribs forward• Contribute to the elasticity of the rib cage
The Bony Thorax
• Vertebrosternal or “True Ribs”•Upper 7 ribs•Attached to the sternum (costal cartilage)•Allow movement (breathing)
• False ribs•5 sets of ribs below true ribs•Has no direct attachment to the sternum
The Bony Thorax• Vertebrocostal ribs•Those ribs connected to the lower thoracic vertebrae with costal cartilage
•Ribs 7 or 8 down to rib 10
•Each rib is attached to the costal cartilage of the rib located superiorly to it (above it)
•AKA “False ribs” because their costal cartilage does not attach directly to the sternum