AP1 M 4.1 Anatomy of the skeleton Flashcards
skeleton
The skeleton, comprised of a network of bones held together at joints, has many functions. The skeleton protects vital internal organs. For example, the skull forms a protective encasement for the brain. The rib cage provides protection for the heart and lungs. Flat bones, such as those of the skull, ribs, and breastbone, produce blood cells.
The five basic bone shapes: Long, flat, short, irregular, and sesamoid
Figure 4.1
bones
All bones are storage areas for inorganic calcium and phosphorus salts. Bones also provide sites for attachment of muscle, tendons, and ligaments. The long bones, particularly those of the legs and the arms, permit flexible body movement. The large, heavy bones of the legs support the body against the pull of gravity
five types of bones
- Long bones are long and thin, designed to support body weight and enable movement. Examples of long bones include the humerus, ulna, radius, tibia, fibula, metacarpals, and metatarsals.
- **Flat **bones (such as in the cranium) form the roof of the skull to protect the brain.
- **Short **bones are small and cube-shaped. The carpals in the hand and tarsals in the foot are short bones.
- ** Irregular **bones are varied in structure with ridges or irregular surfaces. The vertebrae are irregular bones designed to protect the spinal cord as well as enable spinal movements. The pelvic bones (ilium, ischium, and pubis) are also irregular bones.
- **Sesamoid **bones are small and round, reinforcing tendons. The patella is an example of a sesamoid bone.
bone landmarks
Each bone has distinct markings, ridges, grooves, or holes called bone landmarks. Bone landmarks serve several functions. Some bone landmarks allow for tendons to attach. Other markings indicate where nerves and blood vessels run alongside the bone or penetrate the bone to provide blood and nervous supply.
Foramen, canal, fissure
bone landmarks
Foramen, canal, fissure - openings in bone to allow for nerves, blood supply, or a passageway
Sinus
bone landmarks
Sinus - hollow chamber in bone, usually filled with air
Process, ramus
bone landmarks
Process, ramus - elevations in bone
Trochanter, tuberosity, tubercle, crest, line, spine
bone landmarks
Trochanter, tuberosity, tubercle, crest, line, spine - processes or projections for tendon or ligament attachment
Head, neck, condyle, trochlea, facet -
bone landmarks
Head, neck, condyle, trochlea, facet - processes designed for articulation with adjacent bones
Fossa, sulcus
bone landmarks
Fossa, sulcus - depressions in bone
human skeleton
The human skeleton has two main divisions: the axial skeleton and appendicular skeleton.
Figure 4.2 The axial skeleton (blue) includes the skull, vertebral colum
Figure 4.3 Lateral view of the axial skeleton, appendicular skeleton removed
axial skeleton
The axial skeleton lies on the midline of the body and consists of the skull, vertebral column, sternum, laryngeal skeleton, and thoracic (rib) cage
skull
The skull is formed by 22 bones: the cranium (8 bones) and facial bones (14 bones).
Figure 4.4 Fontanelles are present in newborns until around two years of
cranium
The cranium protects the brains and is composed of eight bones fitted tightly together in adults. In newborns, certain bones are not completely formed and instead are joined by membranous regions called fontanelles (see Figure 4.4), commonly called “soft spots.” Fontanelles allow the bones of the skull to compress during childbirth and expand to accommodate a rapidly growing infant brain. These regions begin to close around two months but may last up to two years.
Figure 4.5 and 4.6 Lateral view of the cranial bones.
large bones of the cranium
The large bones of the cranium have the same names as the lobes of the brain: frontal, parietal, temporal, and occipital.
Figure 4.5 and 4.6 Lateral view of the cranial bones.
frontal bone
large bones of the cranium
On the top of the cranium, the frontal bone forms the forehead
Figure 4.5 and 4.6 Lateral view of the cranial bones.
(one bone)
parietal bones
large bones of the cranium
the parietal bones extend to the sides,
Figure 4.5 and 4.6 Lateral view of the cranial bones.
(two, paired bones)
occipital bone
large bones of the cranium
the occipital bone curves to form the base of the skull.
Figure 4.5 and 4.6 Lateral view of the cranial bones.
(one bone)
temporal bone
Below the much larger bones of the cranium
Below the much larger parietal bones, each temporal bone has an opening that leads to the middle ear.
two, paired bones
sphenoid bone
Below the much larger bones of the cranium
The sphenoid bone not only completes the sides of the skull, it also contributes to the floors and walls of the eye sockets.
(one bone)
ethmoid bone
Below the much larger bones of the cranium
the ethmoid bone, which lies in front of the sphenoid, is a part of the orbital wall and, in addition, is a component of the nasal septum.
(one bone)
foramen magnum
reference to the skull
The occipital bone contains a large opening, the foramen magnum, through which the spinal cord passes to become the brain stem. Note the bone landmarks in Figure 4.7,
Figure 4.7 Posterior view of the occipital bone with major bone landmark
sinuses
reference to the skull
The bones of the cranium contain the sinuses, air spaces lined by mucous membrane (see Figure 4.8). Sinuses reduce the weight of the skull and give a resonant sound to the voice. Two sinuses called the mastoid sinuses drain into the middle ear.
Mastoiditis
reference to the skull
Mastoiditis, a condition that can lead to deafness, is an inflammation of the mastoid sinuses. A sinus infection (sinusitis) occurs when the soft tissues inside the sinuses become inflamed from a virus, bacteria, or allergy.
foramina
reference to the skull. Plural for foramen
The foramina of the skull allow for many functions, such as passage for blood vessels, nerves, and the spinal cord
A foramen (pl. foramina) is an opening that allows the passage of structures from one region to another. In the skull base, there are numerous foramina that transmit cranial nerves, blood vessels and other structures – these are collectively referred to as the cranial foramina.
foramen magnum
reference to the skull
The foramen magnum allows for passage of the spinal cord into the skull.
carotid canal
reference to the skull…foramina
The carotid canal is an opening of the temporal bone for the internal carotid artery.
external acoustic meatus
reference to the skull….foramina
The external acoustic meatus (Figure 4.9, Figure 4.12) is for transmission of sound, also located within the temporal bone.
mandible
There are fourteen facial bones
The mandible, lower jaw, is the only movable portion of the skull (Figure 4.10). The mandible and vomer (Figure 4.11, Figure 4.12) are the only non-paired bones of the facial skeleton; all other facial bones are paired.
maxillae
There are fourteen facial bones
The maxillae, the upper jaw, forms the anterior portion of the hard palate and contains the infraorbital foramen. Tooth sockets are found in both the mandible and maxillae
zygomatic bones
There are fourteen facial bones
The zygomatic bones give us our cheekbone prominences, and the nasal bones form the bridge of the nose
palatine bones
There are fourteen facial bones
The palatine bones make up the posterior portion of the hard palate and floor of the nasal cavity
lacrimal bone
There are fourteen facial bones
Each thin, scale-like lacrimal bone lies between an ethmoid bone and a maxillary bone
vomer
There are fourteen facial bones
Each thin, scale-like lacrimal bone lies between an ethmoid bone and a maxillary bone, and the thin, flat vomer joins with the perpendicular plate of the ethmoid to form the nasal septum
inferior nasal conchae
There are fourteen facial bones
The inferior nasal conchae are bones located inferiorly to the middle conchae
middle and superior nasal conchae
There are fourteen facial bones
The middle and superior nasal conchae are formed from the grooves of the ethmoid bone. The nasal conchae act to swirl the air as it is breathed in through the nasal passages, helping to warm and humidify the air before it enters the lower respiratory system.
vertebral column
The vertebral column extends from the skull to the pelvis. In a typical spine, the vertebral column has four curvatures that provide more resilience and strength in an upright posture than a straight column could
cervical
groups names (anatomical regions)
(neck)
thoracic
groups names (anatomical regions)
back, ribs
lumbar
groups names (anatomical regions)
lower back
sacrum, and coccyx
groups names (anatomical regions)
tail
The structure of an individual vertebrae
The structure of an individual vertebrae varies slightly from region to region
spinous processes
The spinous processes are located on the dorsal side of the vertebrae and can be **palpated **(examined externally by touch) as bony projections along the midline of the neck and back.
palpated
can be **palpated **examined externally by touch
vertebral body
structure of an individual vertebrae varies slightly from region to regi
The vertebral body is located on the anterior portion and is the part of the vertebrae with the most surface area.
articular facets
structure of an individual vertebrae varies slightly from region to regi
The articular facets allow adjacent vertebrae to articulate with each other. Note how the spinal cord is protected in the center of the vertebrae and the spinal nerves exit between the vertebrae.
cervical vertebra
There are seven cervical vertebrae. A typical cervical vertebra has a long spinous process with a bifid tip that splits into two parts posteriorly (except for C1). The cervical vertebral bodies are small, and the vertebral foramen are large.
See Figure 4.15
transverse processes
cervical vertebrae
The transverse processes have transverse foramina for the passage of the vertebral arteries and vertebral veins.
See Figure 4.15
A typical thoracic vertebra
A typical thoracic vertebra has a long, thin spinous process that does not split (Figure 4.16). The spinous process points inferiorly. The vertebral bodies are medium-sized and contain facets for rib articulations. The transverse processes also have costal facets for rib articulations. There are twelve thoracic vertebrae, all of which contain the facets for rib articulation on the transverse processes except for T11 and T12.
A typical lumbar vertebra
A typical lumbar vertebra (Figure 17) has a shorter spinous process that is broader and points posteriorly. The vertebral bodies of the lumbar spine are the largest, enabling it to support the weight of the head, neck, trunk, and upper limbs.
transverse processes
lumbar area of spine
The transverse processes are shorter and have no costal facets. The vertebral foramen of the lumbar spine are the smallest and triangular-shaped. Note the other labeled regions in Figure 17 below.
sacrum
The sacrum is comprised of five fused bones at the base of the spine (Figure 4.18). The base of the sacrum is the widest portion, which articulates with the L5 vertebra above it.
coccyx
The coccyx is comprised of four to five fused vertebrae, which typically begin to fuse by around age 25 (Figure 4.18). The sacrum and coccyx provide attachment sites for many ligaments and tendons. The stability of the sacrum, coccyx, and ligaments anchoring them to the pelvis are key for pelvic stability.
Thoracic Cage
All twelve pairs of ribs connect directly to the thoracic vertebrae posteriorly (Figure 4.19). Ribs 1-7 connect directly to the sternum. Ribs 8-10 connect to the sternum indirectly via shafts of cartilage to the sternum.
floating ribs
The lower two pairs of ribs (ribs 11 and 12) are called “floating ribs” because they do not attach to the sternum.
sternum
The sternum is comprised of three parts: the manubrium, body, and xiphoid process.
