Lab #2: Axial Skeleton and Associated Muscles Flashcards
Osteocytes
Mature bone cells derived from osteoblasts that have become entrapped in the matrix they secreted. They reside in small spaces within the matrix called lacunae. Osteocytes maintain the bone matrix and detect mechanical stress on a bone. This info is communicated to osteoblasts, and may result in the deposition of new bone matrix at the surface.
Osteon (Harversian System)
A cylindrical osteon is the basic functional and structural unit of mature compact bone. Osteons run parallel to the diaphysis of the long bone. An osteon is a 3D structure that has several components.
Central Canal
A cylindrical channel that lies in the center of the osteon. Traveling in the central canal are blood vessels and nerves that supply the bone.
Concentric Namellae
Rings of bone connective tissue that surround the central canal and form the bulk of the osteon. The numbers of concentric lamellae vary among osteons. Each lamella contains collagen fibers oriented in one direction; adjacent lamellae contain collagen fibers oriented in alternating directions. In other words, if one lamella has collagen fibers directed superiorly and to the right, the next lamella will have collagen fibers directed superiorly and to the left. This alternating collagen fiber direction gives bone part of its strength and resilience.
Canaliculi
Tiny, interconnecting channels within the bone connective tissue that extend from each lacuna, travel through the lamellae, and connect to other lacunae and the central canal. Canaliculi house osteocyte cytoplasmic projections that permit intercellular contact and communication. Thus, nutrients, minerals, gases, and wastes can travel through these passagewats between the central canal and the osteocytes.
Perforating Canals
Or volkmann canals. Resemble central canals in that they also contain blood vessels and nerves. However, they run perpendicular to the central canals and help connect multiple central canals, thus creating a vascular and innervation connection among the multiple osteons.
Interstitial Lamellae
Leftover parts of osteons that have been partially resorbed. They often look like a “bite” has been taken out of them. The interstitial lamellae are imcomplete and typically have no central canal.
Sutures
With the exception of the mandible, the bones of the skull articulate with each other through joints known as sutures.
Foramina
Throughout the skill, holes known as foramina serve as passageways for blood vessels and nerves.
Surface Skull Bones
Bones on surface of the skull encase the brain, protect sensory organs, and serve as attachment sites for the muscles of the head and neck. These bones include the occipital bone, parietal bones, temporal bones, and the frontal bone, as well as the nasal bones, the zygomatic bones, the maxilla, and the mandible.
Human Skull Makeup
8 Cranial Bones that surround and protect the brain. 14 facial bones that form the underlying structure of the face and support for the teeth.
Sphenoid Bone
The sphenoid bone makes up the anterior base of the cranium. It is a butterfly shaped bone with a central body and two pairs of laterally projecting wings. These wings form portions of the orbit.
The body of the sphenoid features a depression known as the sella turcica, which houses the pituitary gland.
Ethmoid Bone
Located between the orbits, the ethmoid bone makes up a portion of the cranial floor and also the roof of the nasal cavity. An inferior projection, the perpendicular plate of the ethmoid bone forms part of the nasal septum.
The crista galli projects superiorly from the ethmoid bone and serves as the attachment point for the falx cerebri - a dural fold. Extending laterally from the crista galli is the cribriform plate, a perforated area through which the olfactory nerves pass.
Palatine Bones
Two L-shaped bones that form the posterior third of the hard palate, part of the nasal cavity, and a portion of the orbit. The small, thin lacrimal bones make up the anterior portion of the medial wall of each orbit.
Lacrimal Groove
Helps to form the nasolacrimal canal, which contains a duct that allows tears to travel to the nasal cavity. The vomer is an elongated plow-shaped bone that forms the inferior and posterior part of the nasal septum.
Vertebral Column
Composed of 26 bones, including 24 individual vertebrae and the fused vertebrae that form both the sacrum and the coccyx. Each vertebra (except the first and the last) articulates with one superior and inferior vertebra.
Several functions:
- Providing vertical support for the body.
- Supporting the weight of the head.
- Helping to maintain upright body position.
- Helping transfer axial skeletal weight to the appendicular skeleton of the lower limbs.
- Housing and protecting the delicate spinal cord.
- Providing a passageway for spinal nerves that connect to the spinal cord.
Cervical Vertebrae
(C1-C7) From the bones of the neck. The first cervical vertebra (C1) articulates superiorly with the occipital condyles of the occipital bone of the skull. The seventh cervical vertebra (C7) articulates inferiorly with the first thoracic vertebra.
Thoracic Vertebrae
(T1-T12) Form the superior regions of the back, and each articulates laterally with one or two pairs of ribs. The twelfth thoracic vertebra articulates inferiorly with the first lumbar vertebra.
Lumbar Vertebrae
(L1-L5) Form the inferior concave region (“small”) of the back; L5 articulates inferiorly with the sacrum.
Sacrum
Formed from five sacral vertebrae (S1-S5), which fuse into a single bony structure by the mid to late 20s. The sacrum articulates with L5 superiorly and with the first coccygeal vertebra inferiorly. In addition, the sacrum articulates laterally witht he two ossa coxae.
Coccyx
Commonly called the tailbone. Formed from four coccygral vertebrae (Co1-Co4) that start to unite during puberty. The first coccygral vertebra (Co1) articulates with the inferior end of the sacrum. When a person is much older, the coccyx may also fuse to the sacrum.
Body (Centrum)
The anterior region of each vertebra is a rounded or cylindrical body, also called a centrum, which is the weight bearing structure of almost all vertebra.
Vertebral Foramen
Posterior to the vertebral body is the vertebral arch, also called the neural arch. The vertebral arch and body together enclose a roughly circular opening called the vertebral foramen.
Spinous Process
Projects posteriorly from the right and left laminae. Most of these spinous processes can be palpated through the skin of the back.
Transverse Process
Lateral projections on both sides of the vertebral arch.
Intervertebral Discs
The vertebral bodies are interconnected by ligaments. Adjacent vertebral bodies are separated by pads of fibrocartilage called the intervertebral discs. Intervertebral discs are composed of an outer ring of fibrocartilage, called the anulus fibrosus, and an inner circular region, called the nucleus pulposus.
Transverse Foramina
The transverse processes of the first six, sometimes seventh, cervical vertebrae are unique in that they contain prominent, round transverse foramina, which provide a protective bony passageway for the vertebral arteries and veins supplying the brain.
Atlas (C1)
The first cervical vertebra. Supports the head via its articulation with the occipital condyles of the occipital bone. This vertebra is named for the Greek mythological figure Atlas, who carried the world on his shoulders.
The articulation between the occipital condyles and the atlas, called the atlanto-occipital joint, permits us to nod our heads.
The atlas is distinguished from other vertebrae by lack of a body and a spinous process. Instead, the atlas has lateral masses that are connected by semicircular anterior and posterior arches, each containing slight protuberances, the anterior and posterior tubercles.
The atlas has depressed, oval superior articular facets that articulate with the occipital condyles of the skull. The atlas also has inferior articular facets that articulate with the superior articular facets of the axis.
Finally, the atlas has an articular facet for dens on its anterior arch where it articulates with the dens of the axis.
Axis (C2)
During development, the body of the atlas fuses to the body of the second vertebra, called the axis. This fusion produces the most distinctive feature of the axis, the prominent dens, or odontoid (odont = tooth) process. The dens rests in the articular facet for dens of the atlas, where it’s held in place by a transverse ligament. The dens acts as a pivot for the rotation of both the atlas and the skull. This articulation between the atlas and axis, called the atlantoaxial joint, permits us to shake our heads “no”.
Because both the dens and the spinal cord occupy the vertebral foramen at the level of the axis, any trauma that dislocates the dens often results in severe injury. For example, an impact to the head of even severe shaking of a child can dislocate the dens and cause severe damage to the spinal cord. In an adult, a severe blow at or near the base of the skull is often equally dangerous because dislocation of the atlantoaxial joint can force the dens into the base of the brain, with fatal results.
Tendons
Fiberstructures composed of dense connective regular tissue. Connects muscles to bones.
Origin
Muscle attachment on side of the bone that remains relatively stationary.
Insertion
Muscle attachment point on the side of the bone that’s more mobile.
Fibrous Joint
Occurs where bones are held together by dense regular (fibrous) connective tissue.
Cartilaginous Joint
Occurs where bones are joined by cartilage.
Synovial Joint
Has a fluid-filled joint cavity that separates the cartilage-covered articulating surfaces of the bones. The articulating surfaces are enclosed within a capsule, and the bones are also joined by various ligaments.
Synathrosis
Immobile joint.
Amphiarthrosis
Slightly mobile joint.
Diathrosis
Freely mobile joint.
