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Questions and Answers
Which structure does the axial skeleton primarily support and protect?
What is the total number of bones in the human skull?
Which of the following bones is considered a part of the facial bones?
Which structure is formed by the fusion of the cranial bones?
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How many auditory ossicles are associated with the skull?
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Which suture separates the occipital bone from the parietal bones?
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What is the function of foraminae in bones?
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Which component is NOT part of the vertebral column?
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What is the primary function of the occipital condyles?
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Which bones collectively form the lower jaw?
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What is the main characteristic of the cervical vertebrae?
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What type of curves are formed after birth in vertebral column development?
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Which suture covers the unfused areas of an infant's skull?
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Which of the following is NOT a mark of the sphenoid bone?
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How many pairs of ribs are classified as true ribs?
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What is the primary role of the intervertebral discs?
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Where does the sacrum articulate with the coccyx?
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What structure on the temporal bone articulates with the mandible?
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What is the purpose of the greater and lesser wings of the sphenoid bone?
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Which bone does NOT contribute to the formation of the nasal cavity?
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Which part of the mandible is the horizontal portion?
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What characteristic is associated with the thoracic vertebrae?
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Study Notes
Axial Skeleton
- The axial skeleton is the longitudinal axis of the body.
- It supports and protects internal organs, and provides an attachment point for various muscles.
- It includes the skull, the thoracic cage, and the vertebral column.
Skull
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Cranial bones:
- Form the braincase, also known as the cranium.
- Protect and support the brain.
- Enclose the cranial cavity, which contains vital structures like the brain, fluids, blood vessels, nerves, and membranes.
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Facial bones:
- Protect and support the entrances to the digestive and respiratory tracts.
- Provide attachment points for facial muscles.
Cranial Bones
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Occipital bone (1):
- Forms the posterior and inferior surfaces of the cranium.
- Has occipital condyles that articulate with the neck.
- Contains the foramen magnum, connecting the cranial and spinal cavities.
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Parietal bones (2):
- Form part of the superior and lateral surfaces of the cranium.
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Frontal bone (1):
- Forms the anterior cranium and the upper eye sockets.
- Contains the frontal sinuses.
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Temporal bones (2):
- Part of the lateral walls and zygomatic arches.
- Surround and protect the inner ear.
- Attach muscles of the jaws and head.
- Contain the mandibular fossa, which articulates with the mandible.
- Have styloid, mastoid, and external acoustic meatus processes.
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Sphenoid bone (1):
- Part of the floor of the cranium.
- Unites cranial and facial bones, strengthening the sides of the skull.
- Contains the sella turcica and hypophyseal fossa.
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Ethmoid bone (1):
- Forms the anteromedial floor of the cranium, roof of the nasal cavity, part of the nasal septum, and medial orbital wall.
Facial Bones
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Maxillary bones (2):
- Support upper teeth.
- Form the inferior orbital rim, lateral margins of the external nares, upper jaw, and hard palate.
- Contain maxillary sinuses.
-
Palatine bones (2):
- Form the posterior portion of the hard palate.
- Contribute to the floors of the orbits.
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Nasal bones (2):
- Support the bridge of the nose and connect to cartilages of the nose.
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Vomer bone (1):
- Forms the inferior portion of the bony nasal septum.
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Inferior nasal conchae (2):
- Create air turbulence in the nasal cavity, increasing epithelial surface area, warming, and humidifying inhaled air.
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Zygomatic bones (2):
- Contribute to the rim and lateral wall of the orbit, forming part of the zygomatic arch.
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Lacrimal bones (2):
- Form part of the medial wall of the orbit.
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Mandible bone (1):
- The lower jaw, with a body and a ramus on each side.
- Has a condylar process, coronoid process, and mandibular notch.
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Hyoid bone:
- Supports the larynx, attaching muscles of the larynx, pharynx, and tongue.
- It's the only bone that doesn't articulate with any other bone.
Infant Skull
- Fusion is incomplete at birth, with areas of fibrous connective tissue called fontanels.
- Fontanels cover unfused sutures, allowing skull flexibility during birth.
- The anterior fontanel is where the frontal, sagittal, and coronal sutures meet.
- The occipital fontanel is between the lambdoid and sagittal sutures.
Vertebral Column
-
General characteristics:
- Protects the spinal cord.
- Supports the head and body.
- Composed of 26 bones: 24 vertebrae, the sacrum, and the coccyx.
-
Regions:
- Cervical (C) - 7 vertebrae.
- Thoracic (T) - 12 vertebrae.
- Lumbar (L) - 5 vertebrae.
- Sacral (S) - 1 fused vertebrae.
- Coccygeal (Co) - 1 fused vertebrae.
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Curvatures:
- Cervical curve.
- Thoracic curve.
- Lumbar curve.
- Sacral curve.
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Primary curves:
- Thoracic and sacral curves are present during fetal development.
- They accommodate internal organs.
-
Secondary curves:
- Lumbar and cervical curves appear after birth.
- They shift body weight for upright posture.
Vertebrae
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Three parts:
- Vertebral body (centrum): Transfers weight along the spine.
- Vertebral arch: Posterior margin of the vertebral foramen.
- Articular processes: Lateral projections.
-
Intervertebral discs:
- Pads of fibrocartilage between vertebral bodies.
- Absorb shocks.
-
Numbering:
- Vertebrae are numbered by region from top to bottom.
- C1 articulates with the skull, and L5 articulates with the sacrum.
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Region-specific characteristics:
- Vertebrae in each region have characteristics determined by their functions.
Cervical Vertebrae (C1-C7)
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General characteristics:
- Small body to support only the head.
- Large vertebral foramen.
- Bifid (notched) spinous process, except for C1.
-
Atlas (C1):
- Articulates with the occipital condyles of the skull.
- Has no body or spinous process.
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Axis (C2):
- Supports the atlas.
- Has a heavy spinous process.
- The bodies of the axis and atlas fuse during development to form the dens.
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Whiplash:
- Forceful, rapid back-and-forth motion of the cervical spine (sprain).
Thoracic Vertebrae (T1-T12)
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General characteristics:
- Heart-shaped bodies, larger than C1-C7.
- Smaller vertebral foramen than C1-C7.
- Long, slender, knifelike spinous processes.
- Costal facets on dorsolateral surfaces of the body articulate with the heads of ribs.
Lumbar Vertebrae (L1-L5)
-
General characteristics:
- Largest vertebrae.
- Oval-shaped bodies, thicker than T1-T12.
- Triangular vertebral foramen.
- Slender transverse processes.
- Short, heavy spinous processes.
Sacrum (1)
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General characteristics:
- Curved bone that protects reproductive, urinary, and digestive organs.
- Attaches the axial skeleton to the pelvic girdle of the appendicular skeleton.
-
Formation and structure:
- Formed by 5 fused sacral vertebrae.
- Fusion occurs between puberty and ages 25-30, leaving transverse lines.
- Has a broad superior surface (base), alae, a sacral promontory, and a narrow inferior portion (apex).
Coccyx (1)
-
General characteristics:
- Attaches ligaments and a constricting muscle of the anus.
- Formed by 3 to 5 fused coccygeal vertebrae.
Thoracic Cage
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Components:
- Thoracic vertebrae.
- Ribs.
- Sternum (breastbone).
-
Functions:
- Protects organs of the thoracic cavity (heart, lungs, and thymus).
- Forms the rib cage with the ribs and sternum.
Ribs (Costae)
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General characteristics:
- 12 pairs of long, curved, flat bones extending from the thoracic vertebrae.
-
Rib movements:
- Affect the width and depth of the thoracic cage, changing its volume for breathing.
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Types:
- True ribs (1-7): Vertebrosternal ribs, connected to the sternum by costal cartilages.
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False ribs (8-12):
- Vertebrochondral ribs (8-10): Merge with cartilage before reaching the sternum.
- Floating or vertebral ribs (11-12): Connect only to the vertebrae, without a sternal connection.
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Structures:
- Head (capitulum): At the vertebral end.
- Neck: Short area between the head and tubercle.
- Tubercle (tuberculum): Small dorsal elevation.
- Body (shaft): Main part of the rib.
Sternum (Breastbone)
-
General characteristics:
- Flat bone in the midline of the thoracic wall.
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Parts:
-
Manubrium:
- Superior portion, broad and triangular.
- Articulates with collarbones and cartilages of the first rib pair.
- Has a jugular notch.
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Sternal body:
- Attaches to the manubrium and costal cartilages of ribs 2-7.
-
Xiphoid process:
- Smallest part of the sternum, tongue-shaped.
- Attaches to the sternal body, diaphragm, and rectus abdominis muscles.
-
Manubrium:
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Description
Test your knowledge on the axial skeleton, including the skull and its components. This quiz will cover the cranial and facial bones' functions, locations, and importance. Challenge yourself with questions that delve into how these structures support and protect vital organs.
