MBLEX defs:U4: Skeletal System

Catchment

A group of lymph nodes.

Yellow bone marrow

One of two types of bone marrow in the body. It serves primarily as a storehouse for fats, but may be converted to red marrow under certain conditions, such as severe blood loss. As people age, much of the body's red bone marrow is replaced by yellow marrow.

Trapezium

The most lateral of the distal carpal row that articulates with the thumb.

Synovial membrane

A layer of connective tissue that lines the cavities of joints, tendon sheaths, and bursae, and makes synovial fluid.

Synovial joint types

The different types of synovial joints are defined according to the shape of the bone ends, the way they articulate, and the movements they allow. These include pivot joints, gliding joints, condyloid/elipsoid joints, ball-and-socket joints, hinge joints, and saddle joints.

Synchondrosis joint

A type of cartilaginous joint (there are two types) where hyaline cartilage joins the two articulating bones together. An example is the costal cartilage located between a rib and the sternum.

Syndesmosis joint

A joint in which the bones are united by fibrous connective tissue forming an interosseous membrane or ligament, such as the tibiofibular joints.

Synovial fluid

Fluid within the synovial cavity that lubricates and nourishes the joint.

Synovial joint

A type of joint classified by structure where the bones of the joint are held together by a joint capsule. Synovial joints are functionally classified as diarthrotic joints because they allow for a great deal of movement between the bones, as in the hip and shoulder joints.

Synovial joint anatomy

All synovial joints share a number of structural elements including articular cartilage, a joint capsule, a synovial membrane, ligaments, and bursae.

Spongy bone

One of two types of bone tissue made up of small structural beams called trabeculae that give the bone a spongy appearance and lighter weight; also called cancellous or trabecular bone.

Sternal angle

The joint between the manubrium and the body of the sternum.

Structural classification of joints

A classification of joints based on their structure. There are three classifications: fibrous, cartilaginous, and synovial.

Symphysis joint

A type of cartilaginous joint (there are two types) where a fibrocartilage disc between the bodies of the articulating bones joins the bones together. Examples are the intervertebral disc joints of the spine and the symphysis pubis joint of the pelvis.

Synarthrotic joint

A type of joint classified by function, where the joint structures permit very little or no movement. Synarthrotic joints are structurally classified as fibrous joints, where the bones of the joint are held together by dense, fibrous connective tissue. Examples include the interlocking bones of the cranium known as the cranial sutures.

Red bone marrow

One of two types of bone marrow in the body. It consists of highly vascular fibrous tissue containing stem cells, which differentiate into erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets).

Resorption (bone remodeling)

Part of the process of bone remodeling that refers to the breakdown of bone tissue.

Shaft

A common term referring to the diaphysis of a long bone.

Short bone (bone shape)

Bones that are almost equal in length and width with a cube-like shape.

Skeletal system

The body's framework of bones that provide framework, support, protection, levers and fulcrums, mineral storage, and blood cell production. There are 206 distinct bones in the average adult human.

Protection (function of the skeletal system)

A function of the skeletal system where bones provide protection for internal organs and protective channels or openings for blood vessels and nerves.

Periosteum

A dense membrane composed of fibrous connective tissue that closely wraps all bone (except for the articulating surfaces in joints) and serves as the attachment point for ligaments and tendons.

Pedicle

A bony segment between the transverse processes and the vertebral body.

Osteogenic cells

A type of cell found in bone tissue that undergoes mitosis and produces cells that develop into osteoblasts.

Osteogenic

A general term referring to the formation of bone.

Mineral storage (function of the skeletal system)

A function of the skeletal system where bones provide the main storage sites for calcium, phosphorus, and other minerals.

Osseous tissue

A hard form of connective tissue, whose matrix consists of collagen fibers and ground substance and in which are deposited calcium salts (phosphate, carbonate, and some fluoride). Osseous tissue is also called bone tissue and is the major structural and supportive connective tissue of the body.

Osteoblasts

A type of cell found in bone tissue that aids in bone formation.

Osteoclasts

A type of cell found in bone tissue that breaks down bone as part of bone matrix resorption.

Osteocytes

A type of cell found in bone tissue that functions in the exchange of nutrients and wastes, and that maintains bone as living tissue.

Levers and fulcrums (function of the skeletal system)

A function of the skeletal system where bones and joints serve as rigid structures for muscles to move in order to create locomotion.

Ligament

Connective tissue that attaches bone to bone.

Long bone (bone shape)

Bones that are composed of a long shaft (diaphysis) and two heads (epiphyses).

Medullary cavity (bone anatomy)

The cavity within bones that contains bone marrow.

Metaphysis (bone anatomy)

The wide portion of a long bone where the diaphysis and epiphysis meet, and the location of the epiphyseal plate.

Iliac crest

The curved ridge at the top of the pelvic bone.

Irregular bone (bone shape)

Uniquely shaped bones that don't fit into other classifications (e.g., the vertebrae and some facial bones).

Joint

A place where two or more bones are joined together for the purpose of allowing body parts to move; also called an articulation.

Joint capsule

A fibrous connective tissue sleeve that surrounds the articular cavity of a freely movable joint, is attached to the bones, completely encloses the joint, and is composed of an outer fibrous membrane and an inner synovial membrane.

Joint cavity

The closed sac formed by the joint capsule, which contains the synovial fluid.

Hyaline cartilage

A semi-transparent and flexible connective tissue made up of collagen and matrix composed of proteins and water. It functions to withstand both pulling and compressive forces and is found in the trachea, larynx, and joint surfaces.

Functional classification of joints

A classification of joints based on their function (the degree of movement allowed at the joint). There are three classifications: synarthrotic, amphiarthrotic, and diarthrotic.

Framework and support (function of the skeletal system)

A function of the skeletal system is to provide a framework of structure and support for the soft tissues and internal organs.

Flat bone (bone shape)

Thin bones that protect vital organs, such as the pelvis or sternum.

Fibrous joint

A type of joint classified by structure, where the bones of the joint are held together by dense fibrous connective tissue. Functionally classified as synarthrotic joints because they allow for little or no movement between the bones (e.g., suture joints of the skull).

Deposition (bone remodeling)

Part of the process of bone remodeling that refers to the building up of new bone tissue.

Diaphysis (bone anatomy)

The main body of a long bone that is built from compact bone tissue.

Diarthrotic joint

A type of joint classified by function, where the joint structures are freely moveable. Diarthrotic joints are structurally classified as synovial joints where the bones of the joint are held together by a joint capsule. Examples include ball-and-socket-shaped joints of the shoulder and hip, and hinge-shaped joints of the knees and elbows.

Epiphyseal plate (bone anatomy)

A region between the epiphysis and diaphysis where bone growth occurs in children and adolescents; also called the growth plate.

Epiphysis (bone anatomy)

The ends of a long bone composed of spongy bone.

Compact bone

One of two types of bone tissue that is dense, with a hard matrix that renders it resistant to body weight and movement stresses. It is also called cortical bone.

Cartilaginous joint

A type of joint classified by structure, where the bones of the joint are held together by fibrocartilage (called a symphysis joint) or hyaline cartilage (called a synchondrosis joint). Cartilaginous joints are functionally classified as amphiarthrotic joints because they permit a moderate amount of movement. Examples include intervertebral discs and adjacent vertebrae, the articulation between the first rib and sternum, and the pubic symphysis.

Bursae

Small synovial, fluid-filled sacs that create a friction-reducing cushion between structures at joints.

Bony landmarks

The lines, grooves, bumps, marks, and projections on a bone that serve as attachment points for muscles, or passageways for blood vessels and nerves. Often used by massage practitioners as a way to locate structures or determine symmetry or asymmetry, as with a posture assessment.

Bones of the upper extremity

The bones that comprise the upper arm, forearm, and hand: humerus, radius, ulna, carpals, metacarpals, and phalanges.

Bones of the thorax

The bones that form the chest region: the rib cage consisting of the sternum (three fused sections) and 12 pairs of costals (ribs).

Bones of the spinal column

The 33 vertebrae divided into five regions: cervical (7 vertebrae, C1-C7), thoracic (12 vertebrae, T1-T12), lumbar (5 vertebrae, L1-L5), sacral (5 fused vertebrae, S1-S5), and coccygeal (3 or 4 fused vertebrae, Co1-Co4).

Atlas and Axis

In the cervical region of the spinal column, C1 is known as the atlas and C2 is known as the axis.

Bones of the skull

The bones that form the cranium and face, consisting of cranial bones and facial bones.

Cranial bones

The skull bones that form the cranium, including frontal bones, parietal bone, temporal bones, occipital bone, sphenoid bone, and ethmoid bone.

Facial bones

The skull bones that form the face, including lacrimal bones, nasal bones, nasal concha bones, vomer bone, palatine bones, zygomatic bones, maxilla bones, and mandible bone.

Bones of the pelvic girdle

The bones that attach the lower extremity to the axial skeleton: the os coxae formed by the fused ilium, ischium, and pubis.

Bones of the pectoral girdle

The bones that attach the upper extremity to the axial skeleton: clavicle and scapula.

Bones of the lower extremity

The bones that comprise the thigh, leg, and foot: femur, tibia, fibula, tarsals, cuneiforms, metatarsals, and phalanges.

Bone tissue

A hard form of connective tissue, whose matrix consists of collagen fibers and ground substance and in which are deposited calcium salts (phosphate, carbonate, and some fluoride). Bone tissue is also called osseous tissue and is the major structural and supportive connective tissue of the body.

Bone remodeling

An ongoing process where bones are broken down (resorption) and built up (deposition).

Bone marrow

A soft, gelatinous tissue that fills the cavities of bones. It is either red or yellow depending upon the amount of hematopoietic (red) or fatty (yellow) tissue. From birth until approximately seven, all human marrow is red. Fat tissue gradually replaces the red marrow, which in adults is found only in the bones of the vertebrae, hips, sternum, ribs, and skull, and at the ends of the long bones of the arms and legs.

Blood cell production (function of the skeletal system)

A function of the skeletal system where blood cells are produced in the red bone marrow inside bones.

Articular cartilage

A type of hyaline cartilage that covers the articulating surfaces of bones, particularly in a synovial joint.

Articulation

A place where two or more bones are joined together for the purpose of allowing body parts to move; also called a joint.

Atlas (C1)

The first cervical vertebra, which articulates with the occiput superiorly and the axis inferiorly.

Axial skeleton

One of two divisions of the skeleton (appendicular skeleton is the other) that includes the bones of the skull, vertebrae, ribs, and sternum.

Axis (C2)

The second cervical vertebra, characterized by a large projection called the dens, which articulates with the osseous ring of the atlas.

Amphiarthrotic joint

A type of joint classified by function, where the joint structures permit a moderate amount of movement. Amphiarthrotic joints are structurally classified as symphysis joints (held together by a fibrocartilage disc) or synchondrosis joints (held together by hyaline cartilage).

Appendicular skeleton

One of two divisions of the skeleton (axial skeleton is the other) that includes the bones of the pectoral girdle, upper extremity, pelvic girdle, and lower extremity.

Symphysis joint

A structural classification of an amphiarthrotic joint held together by a fibrocartilage disc.

Synchondrosis joint

A structural classification of an amphiarthrotic joint held together by hyaline cartilage.