Ch.7 - The Skeletal System: The Axial Skeleton Flashcards
Bones, joints, and muscles all form the
musculoskeletal system
Orthopedics
the branch of medical science concerned with prevention or correction of the musculoskeletal system.
Divisions of the Skeletal System
Axial Skeleton
- consists of bones arranged along the axis of the body
- 80 bones
- skull (22), hyoid bone (1), vertebral column (26), sternum (1), and ribs
Appendicular Skeleton
- 126 bones
- upper and lower extremities and the pectoral (shoulder) and pelvic (hip) girdles which attach them to the rest of the skeleton
Bones can be classified on the basis of shape
long, flat, short, sesamoid, and irregular
Sutural bones are classified on the basis of location.
Surface Markings
are structural features adapted for specific functions; there are 2 types:
a. Depressions and openings - participate in joints and allow the passage of soft tissue (blood vessels, nerves, tendons, ligaments )
- fissure, foramen, fossa, sulcus, meatus
b. Processes - projections or outgrowths that either help form joints or serve as attachment points for connective tissue, such as ligaments and tendons
- Processes that form joints: condyle, facet, head
- Processes that form attachment points for connective tissue: Crest, Epicondyle, Line Spinous process, Trochanter, Tubercle, Tuberosity
The skull and its functions
composed of 22 bones (8 cranial and 14 facial bones).
Functions to:
a. Protect the brain
b. Their inner surface attach to membranes that stabilize the positions of the brain, blood vessels, and nerves
c. The outer surface of the cranial bones provide large areas of attachment for muscles that move the various parts of the head.
d. facial bones form the framework of the face and protect and provide support for the nerves and blood vessels in that area
e. Cranial and facial bones protect the special sense organ
Cranial bones
- Frontal - forms the forehead, the roofs of the orbits, and most of the anterior part of the cranial floor
- Parietal (x2) - form the greater portion of the sides and roof of of the cranial cavity
- Temporal (x2) - form the inferior lateral aspects of the cranium and part of the cranial floor
- Occipital - forms the posterior part and most of the base of the cranial cavity
- Sphenoid - the KEYSTONE of the cranial floor because it articulates with all the other cranial bones, holding them together.
- Ethmoid - forms part of the anterior portion of the cranial floor, the medial walls of the orbits, the superior portion of the nasal septum, and most of the superior side walls of the nasal cavity. It is a major superior supporting structure of the nasal cavity; it separates the nasal cavity from the brain.
Clinical Connection: A “black eye” results from accumulation of fluid and blood in the upper eyelid following a blow to the relatively sharp supraorbital margin (brow line) or blow to the nose or surgical procedures.
Facial Bones
- Nasal Bones (x2) - form part of the bridge of the nose
- Lacrimal (x2) - form a part of the medial wall of each orbit and are the SMALLEST bones of the face
- Palatine (x2) - form the posterior portion of the hard palate, part of the floor and lateral wall of the nasal cavity, and a small portion of floors of the orbits
- Nasal Conchae (x2) - form a part of the inferior lateral wall of the nasal cavity
- Vomer - found on the floor of the nasal cavity and is one of the components of the nasal septum
- Maxillae (x2) - unite to form the upper jawbone and articulate directly with every bone of the face except the mandible
- Zygomatic (cheekbones x2) - form the prominences of the cheeks and part of the lateral wall and floor of each orbit
- Mandible (jawbone) - the largest and strongest facial bone and the only moveable skull bone other than the ear ossicles.
- The mandible articulates with the temporal bone to form the temporomandibular joint.
Clinical Connection: Cleft Palate and Cleft Lip result from lack of fusion of portions of the palatine and maxillary bones during fetal development.
Clinical Connection: Temporomandibular joint (TMJ) syndrome is dysfunction to varying degrees of the temporomandibular joint. causes appear to be numerous and the treatment is similarly variable.
Nasal Septum
a vertical partition that divides the nasal cavity into right and left sides; consists of bone and cartilage
Clinical Connection: A Deviated Nasal Septum is a lateral deflection of the septum from the midline, usually resulting from improper fusion of septal bones and cartilage.
The orbits (eye sockets)contain the eyeballs and associated structures and are formed by seven bones:
Frontal, sphenoid, ethmoid, palatine, zygomatic, lacrimal, and maxilla
Unique features of the skull
- Sutures - immovable joints found only between skull bones and hold skull bones together. Sutures include the: coronal, sagittal, lambdoidal, and squamous sutures
- Paranasal sinuses - cavities in bones of the skull that communicate with the nasal cavity that are lined by mucous membranes serving to lighten the skull and serve as resonating chambers for speech. The frontal, ethmoid, sphenoid, and maxillae contain the sinuses.
- Fontanels - mesenchymal, dense connective tissue membrane-filled spaces between the cranial bones of fetuses and infants. They remain unossified at birth but close early in a child’s life.
- major fontanels are the anterior, posterior, anterolateral, and posterolaterals
- fontanels have 2 major functions: enable the fetal skull to modify its size and shape (1) and permit rapid growth of the brain during infancy (2)
Clinical Connection: Sinusitis occurs when membranes of the paranasal sinuses become inflamed due to infection or allergy.
Hyoid Bone
A unique component of the axial skeleton because it Dows not articulate with any other bones. it consists of a horizontal body and paired projections, the lesser and greater horns. It functions to support the tongue and provide attachment sites for muscles and the pharynx
Vertebral Column
Provides the body with support and protect the spinal cord from injury.
26 bones of the vertebral column are arranged into five regions
- Cervical (7)
- Thoracic (12)
- Lumbar (5)
- Sacral (1)
1-4 are normal curves of the vertebral column - Coccygeal (1)
- In the fetus, there is only a single anteriorly concave curve.
- The cervical curve develops as the child begins to hold his head erect
- The lumbar curve develops as the child begins to walk
- All curves are fully developed by age 10
- Between adjacent vertebrae , from the first cervical (atlas) to the sacrum, are intervertebral discs that form strong joints, permit various movements of the vertebral column, and absorb vertical shock.
- Parts of a typical vertebra include a body, a vertebral arch, and several processes
Clinical Connection: Caudal Anesthesia (epidural block), frequently used during labor (in childbirth), causes numbness in the regions innervated by the sacral and coccygeal nerves (approximately from the waist to the knees)
Cervical Region (7)
- First cervical vertebra is the atlas which supports the skull
- Second cervical vertebra is the axis which permits side-to-side rotation of the head
- Third to sixth cervical vertebras correspond to the structural patterns of the typical cervical vertebrae
- Seventh cervical vertebra is somewhat different
