Ex. 9 & 10
Overview of the
Skeleton & The Axial
Skeleton
Important figures & quiz knowledge
• All figures (except 10.9) and tables are
important to know & understand
• Review sheet ex. problems are important to
next week’s quiz
– Probably will use a diagram from the review sheet
ex. problems (either Ex. 9 or 10) on the quiz
• Need to know sheets
Bone markings
• Know primary bone marking names &
descriptions
• Be able to use bone markings to ID
disarticulated bones
• Be able to use bone markings to understand
articulation morphology
• Table 9.1, pg. 113
Classification of bones
• Two basic kinds of osseous tissue (differ in their texture):
– Compact bone – smooth and homogeneous.
– Spongy bone/cancellous bone – composed of small trabeculae (bars) of bone
and lots of open space.
– Further classification (based on gross anatomy):
• Long bones – Bones are much longer then they are wide. In general consists of a
shaft with heads at either end. Composed predominantly of compact bone.
– Ex.: Femur and bones of the fingers – phalanges.
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Short bones – cube shaped. Contain more spongy bone than compact bone.
– Ex.: Tarsals and carpals.
• Flat bones – thin, with two layers of compact bone with a layer of spongy bone in
between them. Many are curved.
– Ex.: bones of the skull.
• Irregular bones – bones that do not fall into one of the preceding categories.
– Ex.: vertebrae.
• Sesamoid bones – special types of short bones formed in tendons.
– Ex.: Patellas – kneecaps.
• Wormian/ Sutural bones – tiny bones between cranial bones.
– Except for patellas, the Sesamiod bones and Wormian bones are not included
in the 206 bone count because they vary in number and location in different
individuals.
Bone markings
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Bone Markings
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Two categories:
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Projections/ processes that grow out from the bone and serve as sites of muscle attachment or help form joints
Depressions /cavities are indentations or openings in bones that serve as conduits for nerves and blood vessels
Table 9.1; page 113
Projections that are sites of muscle and ligament attachment:
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Reveal where bones form joints with another bones, where muscles, tendons, and ligaments were attached, and
where blood vessels and nerves passed
Tuberosity – Large rounded projection that may be roughened
Crest – Narrow, usually prominent, ridge of bone
Trochanter – Very large, blunt, irregularly shaped process
Line – Narrow ridge of bone that is less prominent than a crest
Tubercle – Small rounded process
Epicondyle – Raised area on or above a condyle
Spine – Sharp, slender, often pointed projection
Process – Prominence or projection
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Processes that help to form joints:
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Head – Bony expansion carried on a narrow neck
Facet – Smooth, nearly flat articular surface
Condyle – Rounded articular projection
Ramus – Armlike bar of a bone
Cavities:
Antrum – Chamber within a bone
Sinus – Space/cavity within a bone, filled with air and lined with mucous membrane
Depressions and openings that allow blood vessels and nerves to pass:
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Meatus – Canal-like passageway
Fossa – Shallow, basinlike depression in a bone, often serving as an articular surface
Groove – Furrow
Fissure – Narrow, slitlike opening
Foramen – Round or oval opening through a bone
Gross anatomy of long bone
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Major features, figure 9.3, page 115
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Diaphysis – shaft
Periosteum – fibrous membrane covering. Blood vessels and nerves travel through to invade the bone
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Cells:
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Osteoblasts – bone – forming cells
Osteoclasts – bone – destroying cells
Shaft:
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Medullary cavity – central cavity of the shaft
Yellow marrow - adipose tissue
Red marrow – forms blood cells
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Contains osteoblasts and osteoclasts
Epiphysis – the end of long bone. Thin layer of compact bone with a layer of spongy bone in between.
Articular cartilage – covers epiphyseal surface in place of the periosteum
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Found in Marrow cavities in infant
In adult occupies spaces b/n trabeculae of spongy bone, to the interior of the epiphyses
Endosteum – lines inside of the shaft, trabeculae of spongy bone, and canals of compact bone
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Perforating (Sharpey’s) fibers – fibers of the periosteum the penetrate into the bone
Perforating (Volkmann's) canals – run into compact bone and marrow cavity from the periosteum, at the right angles of
the shaft. Complete the communication pathway between the bone interior and its external surface.
Glassy hyaline cartilage provides a smooth surface to prevent friction at joint surfaces
Epiphyseal plate – thin area of hyaline cartilage that provides for longitudinal growth of the bone
during youth
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Epiphyseal lines – remnants of epipyseal plate, ones the bone has stopped growing
Histology
• Osteon /Haversian system – central canal and all the concentric lamellae
surrounding it
– Central (Haversian) canal – runs parallel to the long axis of the bone and
carries blood vessels nerves, and lymph vessels through the body matrix
– Osteocytes – mature bone cells in lacunae (chambers), arranged in concentric
circles (circumferential lamellae) around the central canal
– Lamellae – one of the tubular layers of bone surrounding the central canal in
an osteon
– Interstitial lamellae – remnants of circumferential lamellae that have been
broken down due to bone remodeling
– Canaliculi – tiny canals radiating outward from a central canal to the lacunae
of the 1st Lamella and then form lamella to lamella
• Form dense transportation network through the hard bone matrix, connecting all
living cells of the osteon to the nutrient supply
• Allow each cell to make what it needs for nourishment and to pass along the excess
to the next osteocyte
Cartilages of skeleton
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Perichondrium – dense connective tissue, surrounding cartilage
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Location and Basic Structure
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Chondrocytes and chondroblasts are responsible for the cartilage growth and repair
Acts like a girdle to resists distortion, when cartilage is subjected to pressure
Articular cartilages – cover the bone ends at movable joints
Costal cartilges – connect ribs to the sternum (breast bone)
Laryngeal cartilages – constructs larynx (voice box)
Tracheal and bronchial cartilages – reinforce other passageways of the respiratory system
Nasal cartilages – support external nose
Intervertebral discs – separate and cushion bones of the spine (vertebrae)
External ear cartilage – cartilage that support external ear
Classification of cartilage (Chapter 6, page 78-9)
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Matrix – non-living material secreted by chondrocytes, containing jelly like ground substance and fibers
Hyaline cartilage – most of the skeletal cartilages
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Elastic cartilage – More elastic fibers
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Only collagen fibers are present in the matrix
Provides sturdy support with some resilience
More flexible
Cartilages of external ear and epiglottis
Fibrocartilage – two rows of chondrocytes alternating with rows of thick collagen fibers
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Found where hyaline cartilage joins tendon or ligament
Has a great tensile strength and can withstand heavy compression
Constructs inervertebral discs and the cartilage within the knee joint
Divisions of the skeleton & skull
• Subdivisions of skeleton
– Axial skeleton – bones that lie around the body's center of gravity
– Appendicular skeleton – bones of the limbs/ appendages
• 28 skull bones (8 cranial, 14 facial, and 6 ear bones)
– Cranium – encloses and protects brain tissue
– Facial bones – present eye in an anterior portion and form the base for the
facial muscles
• All facial bones except for mandible (lower jawbone) join the maxilla (upper jaw
bone)
• Sutures – interlocking joint, joins most skull bones (except TMJ)
– Notes from Chapter 12:
• At birth the human body has about 375 bones
• By adulthood, some of the bones have fused together to give us a total of 206
bones in our body
• Fontanels – fibrous membranes
– Indentations between the bones of the fetal skull
– These will ossify as fetus ages (20-22 month). Allow the fetal skull to be compressed
slightly during birth, and allow brain growth during late fetal life.
Skull: cranium
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The Cranium: Eight large, flat (mostly) bones. All single except for Parietals and Temporals, which
come in pairs.
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Frontal Bone – anterior portion of the cranium. Forms forehead, superior part of the orbit, and a floor of
anterior cranial fossa
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Parietal Bone (2) – Posterior to the frontal bone, forming sides of the cranium
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Supraorbital foramen (notch) – opening above each orbit allowing blood vessels and nerves to pass
Sagittal suture – midline articulation point of the two parietal bones
Coronal suture – point of interaction of parietals with frontal bones
Temporal Bone (2) – Inferior to parietal bone on lateral skull
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Four major parts:
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External auditory meatus – canal leading to eardrum and middle ear
Styloid process – needlelike projection inferior to external auditory meatus; attachment point for muscles and ligaments
of the neck
Mastoid region – area posterior to the ear
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Mastoid process – rough projection inferior and posterior to external auditory meatus; attachment site for muscles
Petrous region – forms the lateral portion of the skull base
Occipital Bone – most posterior bone of the cranium, forms floor and back wall
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Squamous region – adjacent to the parietals
Zygomatic process – bridgelike projection joining the zygomatic bone (cheekbone) anteriorly, forming zygomatic arch
Mandibular fossa – rounded depression on the inferior surface of the zygomatic process, point where mandibular condyle of the
mandible (lower jaw) joins the cranium
Tympanic region – surrounds the external ear opening.
Foramen magnum – large opening in base of occipital, which allows the spinal cord to join with the brain
Occipital condyles – rounded projections lateral to the foramen magnum that articulate with the facets of the 1st
cervical vertebrae – atlas
Sphenoid Bone – bat-shaped bone forming the anterior plateau of the middle cranial fossa across the width
of the skull
Ethmoid Bone – irregularly-shaped bone anterior to the sphenoid; forms roof of nasal cavity, upper nasal
septum & part of medial orbit walls
Skull: facial bones
• Fourteen facial bones; all paired except for Mandible and Vomer
– Mandible – lower jaw bone, articulates with the temporal bones in the freely
movable joints of the skull
• Mandibular ramus – vertical extension of the body in either side
• Mandibular condyle – articulation point of the mandible with the mandibular fossa of the
temporal bone
• Coronoid process – protruding anterior portion of the ramus, site of muscle attachment
• Mental foramen – prominent opening on the body (lateral to midline) that transmits the
mental blood vessels and nerve to the lower jaw
– Maxillae – two bones fused in a median suture, form upper jaw-bone and part of the
orbits
• Infraorbital foramen – large bilateral opening located posterior to the central incisor tooth
of the maxilla and piercing the hard palate; transmits the nasopalatine arteries and blood
vessels
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Lacrimal – fingernail-sized pair of bones forming part of medial orbit walls
Palatine – paired bones forming posterior hard palate & part of orbit
Zygomatic – lateral to the maxilla, forms cheekbone, and part of the lateral orbit
Nasal – small rectangular bones forming the bridge of the nose
Vomer – blade-shaped bone forming posterior & inferior nasal septum
Inferior Nasal Conchae (turbinates) – thin, curving bones protuding from lateral
nasal cavity walls
Located in the throat above the larynx, where it serves as a point of
attachment of many tongue and neck muscles
Bony thorax
• Sternum (breast bone): 3 fused bones
– Manubrium
– Body
– Xiphoid process
• Ribs: walls of thoracic cage
– Articulate posteriorly with the vertebral column via their heads and
tubercles
– Curve downward and toward anterior body surface.
– 12 pairs
• 7 pairs of true (vertebrosternal) ribs: attach directly to the sternum by
their own costal cartilage
• 5 pairs of false ribs: attach indirectly or lack sternal attachment
– 3 vertebrochondral: indirectly attach to sternum via costal cartilage of rib 7
– 2 floating (vertebral) ribs: no sternal attachment
7, 12, 5: “Come in at 7, lunch at 12, leave at 5.”
Vertebral column
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26 vertebrae
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Expends from the skull to the pelvis, forms the body’s major axial support
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Surrounds and protects spinal cord while allowing the spinal nerves to issue from the cods via openings between adjacent
vertebrae
Intervertebral discs – fibrocartilage pads with fluid components, separate and cushion the vertebrae and absorb
shocks
S-shape
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7 cervical or neck
12 thoracic
5 lumbar or loins
Sacrum: 5 fused vertebrae
Coccyx: vestigial tail; 4 fused vertebrae
Increases strength of the back
Helps vertebral column absorb the shock of walking upright
Helps to maintain balance
Structure of a Typical Vertebra
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Centrum – rounded central portion, which faces anteriorly in the human vertebral column
Vertebral arch – composed of pedicles, laminae, and spinous process, it represents he junction of all posterior extensions
from the vertebral body
Vertebral (spinal) foramen – opening enclosed by the body and vertebral arch; a channel for the spinal cord
Transverse processes – two lateral projections from the vertebral arch
Spinous process – single medial and posterior projection from the vertebral arch
Superior and inferior articular processes – paired projections lateral to the vertebral foramen that allows contact with
adjacent vertebrae
Intervertebral foramina – right and left pedicles have notches on their inferior and superior surfaces that create openings ,
for spinal nerves to leave the spinal cord between adjacent vertebrae
Rule of Thumb: Body
gets thicker as
proceeding down spine
to support weight – so
do the vertebrae
• Ways to distinguish
– Size
– # of foramina (1 or 3)
– Size & direction of
processes
• Note on atlas and axis
– “Atlas holds up the world”
• No spinous process
– “Atlas spins on the axis”
• Funny shape to spinous
process
• Dens is the pivot that atlas
sits on