Title: The Axial Skeletal System
1The Axial Skeletal System
2Divisions of the Skeletal System
- Humans are born with approximately 300 bones
which fuse to 206 bones as adults. - There are 2 main divisions of the skeletal
system axial skeleton and appendicular skeleton.
3Divisions of the Skeletal System
- Axial skeleton forms the vertical axis of the
body. - 80 bones skull (22), vertebral column (26),
ribcage (25), auditory ossicles (6), and hyoid
(1) - Appendicular skeleton forms the arms, legs and
the girdles - Girdles attach the arms and legs to the axial
skeleton - 126 bones pectoral girdle (4), arms (60), legs
(60) and pelvic girdle (2)
4Skull
- Superior end of the vertebral column
- Composed of flat and irregular shaped bones
- Large hollow space within the skull is called the
cranial vault or cranial cavity. - Functions to
- Surround and protect the brain
- Be points of attachment for the facial muscles
(landmarks)
5Divisions of the Skull
- Cranial division consists of 8 flat bones that
form a protective box around the brain. - Help to form the cranial vault (cavity)
- Frontal (1) forms the anterior portion of the
cranial cavity - Forms the superior orbits of the eyes and forms
the forehead
6Frontal Bone Landmarks
- Supraorbital margin a thickened ridge of bone
found superior to the orbit of the eye. - Just deep to the eyebrow and more prominent on
the lateral portion - Point for muscle attachment (PFMA)
- Supraorbital foramen a small opening found on
the medial aspect of the supraorbital margin. - Can feel it best inferior to the margin
- Allows blood vessels and nerves to enter the
frontal bone
7Frontal Bone Landmarks
- Frontal sinus A hollow space found within the
frontal bone, superior and medial to the
supraorbital margin. - Can only be seen with a sagittal cut
- ¼ inch superior to the eyebrows
- House mucus and macrophages for trapping and
destroying foreign particles.
8Frontal Bone Landmarks
- Frontal sinus A hollow space found within the
frontal bone, superior and medial to the
supraorbital margin. - Can only be seen with a sagittal cut
- ¼ inch superior to the eyebrows
- House mucus and macrophages for trapping and
destroying foreign particles.
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16Parietal Bones (2)
- Form the lateral walls and the superior portion
of the cranium. - Landmarks
- Temporal fossa A large, shallow depression that
begins on the parietal bone and extends to the
frontal bone. - PFMA
17Temporal Bones (2)
- Form the inferior lateral walls and a portion of
the floor of the cranium. - Articulate with the mandible (lower jaw) to form
the temporomandibular joint (TMJ) - Temporal bone landmarks
- Mastoid process A large, blunt projection found
posterior to the external auditory meatus. - Bump behind the ear
- PFMA
18Temporal Bone Landmarks cont..
- Styloid process A thin, sharp projection found
inferior and medial to the external auditory
meatus. - Covered with muscle so it is more difficult to
identify - PFMA
- Zygomatic process A thin, flat projection found
anterior to the external auditory meatus. - PFMA
- External auditory meatus The external ear canal
- Opening through which the auditory nerve runs.
19Temporal Bone Landmarks cont..
- Mandibular fossa A shallow depression found
inferior and slightly anterior to the external
auditory meatus - This forms an articulation with the mandible
- Easy to see inferiorly if the mandible is removed
20Occipital Bone (1)
- Forms the posterior wall and the floor of the
cranium. - The spinal cord passes through this as it exits
the cranial vault. - Occipital bone landmarks
- External occipital protuberance A prominent
midline projection found on the superior surface. - Where the occipital bone turns to form the
horizontal part.
21Occipital Bone Landmarks cont..
- Superior nuchal line Two curved ridges that
extend laterally from the external occipital
protuberance. - PFMA
- Inferior nuchal line Two curved ridges that
extend laterally from the external occipital
protuberance, inferior to the superior nuchal
line. - PFMA
- Foramen magnum A large opening in the inferior
surface of the occipital bone that allows the
spinal cord to exit the cranial cavity. - Largest foramen in the body.
22Occipital Bone Landmarks cont..
- Occipital condyles Paired oval-shaped
projections found lateral to the foramen magnum. - Form an articulation with the 1st bone of the
spine (atlas)
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24Sphenoid Bone (1)
- Forms the anterior floor of the cranial cavity.
- Also forms a portion of the lateral walls of the
cranial cavity. - Forms the posterior wall of the orbits of the
eyes. - The keystone bone for the cranium because it
articulates with all other cranial bones. - Shape resembles a bat with outstretched wings
when viewed superiorly.
25Sphenoid Bone Landmarks
- Greater wing The larger, inferior projection of
the sphenoid that forms a portion of the floor
and the lateral walls of the cranium. - Also forms the posterior wall of the orbits of
the eyes. - Lesser wing The smaller, superior projection of
the sphenoid bone located posterior to the
frontal bone.
26Sphenoid Bone Landmarks cont..
- Sella turcica A small, saddle-like depression
found between the greater and lesser wings that
surrounds and protects the pituitary gland. - Pituitary is an important endocrine gland
- 3 parts to the sella turcica
- Tuberculum sellae The anterior portion of the
sella turcica. - Closest to the lesser wing.
27Sphenoid Bone Landmarks cont..
- 3 parts to the sella turcica continued
- Hypophyseal fossa The seat of the saddle.
- Where the pituitary gland resides
- Dorsum sellae The posterior portion of the sella
turcica. - Closer to the greater wing
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33Ethmoid Bone (1)
- The small bone located anterior to the sphenoid
bone in the middle of the frontal bone. - Forms a small portion of the anterior floor of
the cranium. - Also forms a small portion of the medial wall of
the eye orbits. - Also forms the superior portion of the nasal
septum.
34Ethmoid Bone Landmarks
- Cribriform plate Paired projections found
lateral to the crista galli. - Has small openings called the olfactory foramina.
- Olfactory foramina A series of small openings
found within the cribriform plate that allow
nerves from the olfactory epithelium to pass
directly into the brain. - These nerves give us our sense of smell.
35Ethmoid Bone Landmarks cont..
- Crista galli A small triangular projection found
in the center of the ethmoid bone. - Near the front of the cranial cavity.
- Point of attachment for the meninges (protective
coverings of the brain). - Perpendicular plate A small vertical projection
arising from the inferior surface of the ethmoid
bone. - Forms the superior portion of the nasal septum.
- Articulates with the vomer (facial bone).
36Ethmoid Bone Landmarks cont..
- Superior and middle nasal conchae Two thin,
scroll-shaped projections found lateral to the
perpendicular plate - The middle nasal conchae is inferior to the
superior nasal conchae. - These increase surface area of the nasal
passageways - Ethmoidal cells Air spaces found within the
lateral masses of the ethmoid bone. - Small sinuses
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42Sutures
- Fibrous joints found between the bones of the
cranium. - There are 4 major sutures
- Coronal unites the frontal bone and both
parietal bones - Sagittal unites the two parietal bones on the
superior midline of the skull - Lambdoid unites the two parietal bones to the
occipital bone. - Squamous (2) unite the parietal and temporal
bones on the lateral sides of the skull
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46The Facial Division
- A group of 14 irregular bones that serves as
points of attachment for muscles of the face. - Nasal (2) form the bridge of the nose.
- Rectangular shaped bones
- PFMA
- Maxillae (2) Form the upper jaw.
- Articulate with every face bone except the lower
jaw. - Form part of the floors of the orbits, lateral
walls and floor of the nasal cavity, and most of
the hard palate (bony roof of the mouth).
47Maxillary Landmarks
- Infraorbital foramen Small openings found
inferior to the orbits of the eyes. - Allows passage of blood vessels and nerves.
- Palatine process a lateral projection that forms
one half of the anterior portion of the hard
palate. - Typically the 2 processes unite during weeks
10-12 of embryo development. If not, cleft
palate will result. This negatively impacts
speech and swallowing.
48Maxillary Landmarks cont
- Maxillary sinuses a series of small spaces
within the maxillae. - Empty into the nasal cavity.
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52Zygomatic Bone (2)
- Form the prominence of the cheeks.
- Also form part of the lateral wall and floor of
each orbit. - Articulate with the frontal, maxilla, sphenoid
and temporal bones. - Zygomatic bone landmarks
- Temporal process a thin, flat projection arising
from the lateral, posterior surface of the
zygomatic bone. - Articulates with the zygomatic process of the
temporal bone.
53Zygomatic Bone Landmarks cont..
- Zygomatic arch created by the articulation of
the temporal process of the zygomatic bone and
the zygomatic process of the temporal bone.
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55Lacrimal Bones (2)
- The smallest bones of the facial division.
- Resemble the shape and size of a fingernail
- Posterior and lateral to the nasal bones and form
part of the medial wall of each orbit. - Lacrimal bone landmark
- Lacrimal fossa a small vertical groove formed
with the maxilla, that helps drain fluid away
from the eye. - Houses a lacrimal sac that gathers tears and
passes them into the nasal cavity.
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58- Palatine Bones (2) L shaped bones that form
the posterior portion of the hard palate. - The parts that make-up the hard palate are called
horizontal plates. - Inferior Nasal Conchae (2) scroll shaped bones
that form a portion of the inferior, lateral
walls of the nasal cavity. - Increase surface area and help filter air along
with the superior and middle nasal conchae of the
ethmoid bone.
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63- Vomer (1) a triangular bone that forms a portion
of the posterior floor of the nasal cavity. - Articulates with the perpendicular plate of the
ethmoid bone to form the inferior portion of the
bony nasal septum. - Mandible (1) the largest bone of the facial
division. - Except for the ossicles, it is the only moveable
skull bone.
64Mandibular Landmarks
- Mandibular body a triangular bone that forms a
portion of the posterior floor of the nasal
cavity. - Ramus the short, vertical portion of the
mandible. - Angle the area where the ramus and the body of
the mandible meet. - Coronoid process a small triangular projection
found on the superior anterior portion of the
ramus.
65Mandibular Landmarks cont
- Condylar process a small rounded projection
found on the superior posterior portion of the
ramus. - Articulates with the mandibular fossa to create
the temporomandibular joint (TMJ). - Mental foramen small openings found in the
anterior surface of the body of the mandible that
allow blood vessels and nerves to enter the
mandible. - Alveoli sockets for teeth
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67Auditory Ossicles
- The 6 smallest bones in the human body.
- Located medial to the eardrum.
- Connected by synovial joints.
- Function to transfer sound waves from the eardrum
to the inner ear. - The bones are as follows
- Malleus- attaches to the eardrum and is commonly
called the hammer. - Incus- middle bone that is commonly called the
anvil. - Stapes- Smallest bone and is commonly called the
stirrup.
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70Hyoid Bone
- Located superior to the larynx (voice box).
- U shaped
- The only bone that does not articulate with
another bone. - Suspends from the styloid processes by ligaments
and muscles. - Often fractured during strangulation.
- Functions to support the tongue.
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73The Vertebral Column
- Also called the spine, backbone or spinal column.
- Consists of 33 (children) or 26 (adults) bones
called vertebrae. - Functions to protect the spinal cord, support the
head, and serve as attachment points for the
ribs, pelvis, back muscles and arm muscles.
74Vertebrae
- Vary in size, shape and detail but have many
similarities. - Consist of 3 main parts vertebral body,
vertebral arch and several processes. - Vertebral body the thickened anterior portion of
a vertebra. - Holds the intervertebral disc and contains
foramina for the entrance of blood vessels. - Intervertebral discs pads of fibrocartilage that
help hold the vertebrae in place. - Compress throughout the day due to weight and
water loss. This compression does not change
height as we age.
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76Vertebrae continued
- Vertebral arch located posterior to the
vertebral body. - Forms the vertebral foramen with the vertebral
body. - The vertebral arch consists of the pedicles and
the laminae. - Pedicles the shorter anterior portions of the
vertebral arch. - Laminae the longer posterior portions of the
vertebral arch.
77Vertebrae continued
- Vertebral foramen the opening formed by the
vertebral body and the vertebral arch. - Contains the spinal cord, adipose tissue, areolar
connective tissue and blood vessels. - Processes bony projections that arise from the
vertebral arch. - Transverse processes paired lateral projections
that arise from the vertebral arch. - Spinous process the single posterior projection
that arises from the vertebral arch. - Both of these are PFMA
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80Cervical Vertebrae
- The first 7 vertebrae (C1-C7).
- Smaller bones than other vertebrae but larger
vertebral foramen. - Also have 2 transverse foramen through which the
vertebral artery, vein and nerve fibers pass. - C2-C6 have a branching spinous process.
- C1 is called the atlas.
- Supports the skull.
- It lacks a body and a spinous process.
81Cervical Vertebrae cont
- C2 is called the axis.
- Has a body and a peglike process called the dens
or the odontoid process. - The dens makes a pivot on which the atlas and
head rotate. - C7 is called the vertebra prominens.
- Has a large spinous process that is not branched
and can be felt at the back of the neck.
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83Thoracic Vertebrae
- The next 12 vertebrae (T1-T12).
- Have facets (flat surfaces) where they articulate
with the 12 rib pairs. - Movement of these vertebrae are most limited
because the ribs attach to the sternum anteriorly.
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85Lumbar Vertebrae
- The next 5 vertebrae (L1-L5).
- The largest and strongest of the bones of the
spine. - Spinous processes are thick and broad.
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87Sacrum
- The next vertebra in the adult vertebral column.
- A triangular shaped bone formed from the fusion
of 5 bones. This starts around age 16 and is
usually completed by age 30. - Auricular surfaces large, ear-shaped roughened
surfaces found on the lateral aspect of the
sacrum. - This articulates with the hip bones of the pelvis.
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89Coccyx
- The last vertebra in the adult vertebral column.
- The tailbone that is formed by the fusion of 4
vertebrae that occurs between the age of 20-30. - In males, it points anteriorly and in females it
points inferiorly.
90ACT-UP
91ACT-UP
- What region of the vertebral column might be most
affected by osteoporosis? - Why?
- What would we expect to see (on the outside) when
looking at a person suffering from osteoporosis?
92Thorax
- Includes the sternum, ribs and the bodies of the
thoracic vertebrae. - Sternum located along the anterior midline of
the thorax. - Also known as the breastbone
- Consists of 3 parts that fuse by age 25 and the
points of fusion can be seen as transverse
ridges. - If thoracic surgery is necessary, the sternum may
be cut along the midline.
93Regions of the Sternum
- Manubrium the superior portion of the sternum
- Articulates with the clavicles (collarbones) and
the costal cartilages of the 1st-2nd rib pairs. - Sternal body the intermediate portion of the
sternum. - Articulates directly or indirectly with the
costal cartilages of the 2nd-10th rib pairs. - Xiphoid process the inferior portion of the
sternum. - Where some abdominal muscles attach.
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95Ribs
- 12 pairs of flat bones that form a protective
cage around the heart and the lungs. - Increase in length from 1-7 and then decrease
from 7-12. - Each rib pair articulates posteriorly with its
corresponding thoracic vertebra. - Costal cartilage elongated pads of hyaline
cartilage used to attach the ribs to the sternum. - Allows the ribcage to be more elastic and limits
fracturing from blows to the chest.
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98Types of Ribs
- True ribs Rib pairs 1-7
- Their costal cartilages attach directly to the
sternum. - False ribs Rib pairs 8-12
- Their costal cartilages do not attach directly to
the sternum. Rib pairs 8-10 have cartilages that
attach to the cartilage of 7 (which attaches to
the sternum. - Floating ribs Rib pairs 11-12
- The costal cartilages do not attach to the
sternum at all.
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