Chapter 7: The Skeletal System: The Axial System Flashcards
What are the two divisions of the musculoskeletal system and which bones do they each contain?
The axial skeleton consists of the bones that lie around the longitudinal axis of the human body, an imaginary vertical line that runs through the body’s center of gravity from the head to the space between the feet: skull bones, auditory ossicles (ear bones), hyoid bone, ribs, sternum (breastbone), and bones of the vertebral column.
The appendicular skeleton consists of the bones of the upper and lower limbs (extremities or appendages), plus the bones forming the girdles that connect the limbs to the axial skeleton.
What are the five categories of bone based on shape?
Long bones have greater length than width, consist of a shaft and a variable number of extremities or epiphyses (ends), and are slightly curved for strength. They include the major bones of the arms and legs and the phalanges of the fingers and toes.
Short bones are somewhat cube-shaped and are nearly equal in length and width. They include most carpal and tarsal bones.
Flat bones are generally thin and composed of two nearly parallel plates of compact bone tissue enclosing a layer of spongy bone tissue. Flat bones include the cranial bones; the sternum (breastbone) and ribs; and the scapulae (shoulder blades).
Irregular bones have complex shapes and cannot be grouped into any of the previous categories. Such bones include the vertebrae, hip bones, certain facial bones, and the calcaneus.
Sesamoid bones develop in certain tendons where there is considerable friction, tension, and physical stress, such as the palms and soles. They may vary in number from person to person, are not always completely ossified, and typically measure only a few millimeters in diameter. Notable exceptions are the two patellae (kneecaps), large sesamoid bones located in the quadriceps femoris tendon that are normally present in everyone.
What type of bone is categorized by location instead of shape?
Sutural bones are small bones located in sutures (joints) between certain cranial bones. Their number varies greatly from person to person.
What are the two major types of surface markings found on bones?
- Depressions and Openings
- Processes, Projections, and Outgrowths.
What are the five different kinds of Depressions and Openings found on bones?
A Fissure is a narrow slit through which blood vessels or nerves pass.
A Foramen is an opening through which blood vessels, nerves, or ligaments pass.
A Fossa is a shallow depression.
A Sulcus is a furrow along bone surfaces that accommodates blood vessels, nerve, or tendons.
A Meatus is a tubelike opening.
What are the different kinds of Processes, Projections, and Outgrowths found on bones?
Processes that form joints include:
Condyle (large, round protuberances with smooth articular surfaces)
Facets (smooth, flat, slightly concave or convex articular surfaces)
Heads (rounded articular projections).
Processes that form attachment points for connective tissue include:
Crests (prominent ridges)
Epicondyle (roughened projections above condyle)
Lines (long, narrow ridges or lines, less prominent than crests)
Spinous processes (sharp, slender projections)
Trochanters (very large projections)
Tubercles (variably sized rounded projections)
Tuberosities (variably sized projections with rough, bumpy surfaces)
Describe the 8 cranial bones.
The frontal bone forms the forehead, the roofs of the orbits, and most of the anterior part of the cranial floor.
The parietal bones form the greater portion of the sides and roof of the cranial cavity.
The temporal bones form the inferior lateral aspects of the cranium and part of the cranial floor.
The occipital bone forms the posterior part of the cranium and part of the base of the cranium.
The sphenoid bone lies at the middle part of the base of the skull and is known as the keystone of the cranial floor because it articulates with all the other cranial bones, holding them together.
The ethmoid bone is located in the anterior part of the cranial floor medial to the orbits, anterior to the sphenoid and posterior to the nasal bones.
Describe the 14 facial bones.
The nasal bones from the bridge of the nose.
The lacrimal bones are posterior and lateral to the nasal bones and form a part of the medial wall of each orbit.
The palatine bones form the posterior portion of the hard palate, part of the floor and lateral wall of the nasal cavity, and a small portion of the floors of the orbits.
The inferior nasal conchae form a part of the inferior lateral wall of the nasal cavity and project into the nasal cavity.
The vomer forms the inferior portion of the nasal septum.
The maxillae form the upper jawbone.
The zygomatic bones (cheekbones) form the prominences of the cheeks and part of the lateral wall and floor of each orbit.
The mandible is the lower jawbone, the largest and strongest facial bone.
Identify the bones and features from an anterior view of the skull.
Identify the bones and features from a lateral view of the skull.
Identify the bones and features from a posterior view of the skull.
Describe the following special features of the skull: sutures, paranasal sinuses, and fontanels.
A suture is an immovable joint (in most cases in an adult skull) that holds most skull bones together.
The coronal suture unites the frontal bone and both parietal bones.
The sagittal suture unites the two parietal bones on the superior midline of the skull
The lambdoid suture unites the two parietal bones to the occipital bone.
The two squamous sutures unite the parietal and temporal bones on the lateral aspects of the skull.
The paranasal sinuses are cavities within certain cranial and facial bones near the nasal cavity. The paranasal sinuses increase the surface area of the nasal mucosa, thus increasing the production of mucus to help moisten and cleanse inhaled air. In addition, the paranasal sinuses serve as resonating (echo) chambers within the skull that intensify and prolong sounds, thereby enhancing the quality of the voice.
At birth, bone ossification is incomplete, leaving spaces between incompletely developed cranial bones called fontanels, or “soft spots.”
Describe the relationship of the hyoid bone to the skull.
The single hyoid bone is a unique component of the axial skeleton because it does not articulate with any other bone. Rather, it is suspended from the styloid processes of the temporal bones by ligaments and muscles. Located in the anterior neck between the mandible and larynx, the hyoid bone supports the tongue, providing attachment sites for some tongue muscles and for muscles of the neck and pharynx.
Name and locate the 4 sutures of the skull.
The coronal suture unites the frontal bone and both parietal bones.
The sagittal suture unites the two parietal bones on the superior midline of the skull.
The lambdoid suture unites the two parietal bones to the occipital bone.
The two squamous sutures unite the parietal and temporal bones on the lateral aspects of the skull.
Identify and describe the 5 regions of the vertebral column and the 3 parts of a vertebra.
The adult vertebral column typically contains 26 vertebrae. These are distributed as follows:
- 7 cervical vertebrae in the neck region.
- 12 thoracic vertebrae posterior to the thoracic cavity.
- 5 lumbar vertebrae supporting the lower back.
- 1 sacrum consisting of five fused sacral vertebrae.
- 1 coccyx usually consisting of four fused coccygeal vertebrae.
Vertebrae typically consist of a vertebral body, a vertebral arch, and several processes.
Identify and describe the two components of the intervertebral discs.
Intervertebral discs are found between the bodies of adjacent vertebrae from the second cervical vertebra to the sacrum. Each disk has an outer fibrous ring consisting of fibrocartilage called the annulus fibrosus and an inner soft, pulpy, highly elastic substance called the nucleus pulposus.
Name the 4 normal curves of the vertebral column and identify whether they are convex or concave.
The cervical and lumbar curves are convex (bulging out); the thoracic and sacral curves are concave (cupping in).
Describe the axis and the atlas.
The atlas, the first cervical vertebra, is a ring of bone with anterior and posterior arches and large lateral masses. It lacks a body and a spinous process. The superior surfaces of the lateral masses, called superior articular facets, are concave. They articulate with the occipital condyles of the occipital bone to form the paired atlanto-occipital joints. These articulations permit you to move your head to signify “yes.”
The second cervical vertebra (C2), the axis, does have a vertebral body. A peg-like process called the dens or odontoid process projects superiorly through the anterior portion of the vertebral foramen of the atlas. The dens makes a pivot on which the atlas and head rotate. This arrangement permits side-to-side movement of the head, as when you move your head to signify “no.” The articulation formed between the anterior arch of the atlas and dens of the axis, and between their articular facets, is called the atlanto-axial joint.
Identify the bones of the thorax and their functions.
The term thorax refers to the entire chest region. The skeletal part of the thorax, the thoracic cage, is a bony enclosure formed by the sternum, ribs and their costal cartilages, and the bodies of the thoracic vertebrae. (The costal cartilages attach the ribs to the sternum.) The thoracic cage encloses and protects the organs in the thoracic and superior abdominal cavities, provides support for the bones of the upper limbs, and plays a role in breathing.
Identify the 3 parts of the sternum.
The sternum, or breastbone, is a flat, narrow bone located in the center of the anterior thoracic wall. The superior part is the manubrium, the middle and largest part is the body; and the inferior, smallest part is the xiphoid process.
Differentiate between the different kinds of ribs.
The three types of ribs are the true (vertebrosternal) ribs, vertebrochondral ribs, and floating (vertebral) ribs.
The first through seventh pairs of ribs, called true ribs, have a direct anterior attachment to the sternum by a strip of hyaline cartilage called costal cartilage. The remaining five pairs of ribs are termed false ribs because their costal cartilages either attach indirectly to the sternum or do not attach to the sternum at all. The cartilages of the eighth, ninth, and tenth pairs of ribs attach to one another and then to the cartilages of the seventh pair of ribs. These false ribs are called vertebrochondral ribs. The eleventh and twelfth pairs of ribs are false ribs designated as floating (vertebral) ribs because the costal cartilages at their anterior ends do not attach to the sternum at all.
