BIO200N Human Anatomy & Physiology: The Skeletal System and Joints

These flashcards provide vocabulary and definitions for the primary components of the axial and appendicular skeleton, bone tissue types, microscopic bone structures, and joint classifications and movements.

Axial Skeleton

The division of the skeleton that forms the body’s longitudinal axis, consisting of the skull, the bony thorax, and the vertebral column.

Appendicular Skeleton

The division of the skeleton composed of 126 bones, including the limbs and the pectoral and pelvic girdles that attach the limbs to the axial skeleton.

Compact Bone

Osseous tissue that is dense and appears smooth and homogeneous.

Spongy Bone

Osseous tissue composed of small, needlelike bars called trabeculae and significant open space.

Long Bones

Bones that are much longer than they are wide, consisting mostly of compact bone; examples include the femur and phalanges.

Short Bones

Typically cube-shaped bones that contain more spongy bone than compact bone.

Flat Bones

Thin bones consisting of a layer of spongy bone sandwiched between two waferlike layers of compact bone, such as bones of the skull.

Irregular Bones

Bones that do not fit into the long, short, or flat categories; examples include the vertebrae.

Diaphysis

The shaft of a long bone.

Epiphysis

The end portion of a long bone.

Periosteum

The fibrous membrane covering the external surface of the diaphysis.

Osteon

The functional unit of compact bone, consisting of a central canal and all the concentric lamellae surrounding it.

Red Marrow

The site within bones responsible for blood cell formation.

Calcium Salts

Inorganic components in the bone matrix that provide hardness and compressional strength.

Collagen Fibers

Organic elements of the bone matrix that provide flexibility and tensile strength to resist stretching.

Cranium

The portion of the skull composed of eight large flat bones that encloses and protects the brain.

Sagittal Suture

The joint where the left and right parietal bones meet superiorly.

Coronal Suture

The joint where the parietal bones articulate with the frontal bone.

Squamous Suture

The joint on the lateral aspect of the skull where each parietal bone meets a temporal bone.

Lambdoid Suture

The joint where the parietal bones meet the occipital bone posteriorly.

Foramen Magnum

A large opening in the base of the occipital bone that allows the spinal cord to join with the brain.

Mandible

The lower jawbone; it articulates with the temporal bones and is the only freely movable joint in the skull.

Maxillae

Two fused bones forming the upper jawbone; they are considered the keystone bones of the face because all other facial bones except the mandible join them.

Hyoid Bone

A horseshoe-shaped bone located in the throat above the larynx that serves as an attachment point for tongue and neck muscles.

Paranasal Sinuses

Mucosa-lined air cavities in the maxillary, sphenoid, ethmoid, and frontal bones that lighten the skull and act as resonance chambers for speech.

Intervertebral Discs

Pads of fibrocartilage between vertebrae that absorb shocks and provide flexibility to the spine.

Atlas ($C_1$)

The first cervical vertebra, which lacks a body and allows the head to nod 'yes' by articulating with the occipital condyles.

Axis ($C_2$)

The second cervical vertebra, featuring a vertical process called the dens that acts as a pivot for rotating the head 'no'.

Thoracic Vertebrae

The 12 vertebrae ($T_1$ through $T_{12}$) that have heart-shaped bodies and costal facets for articulating with the ribs.

Lumbar Vertebrae

The five vertebrae ($L_1$ through $L_5$) with massive, blocklike bodies and short, thick spinous processes; they are built for strength and stress resistance.

Sacrum

A bone formed by the fusion of five vertebrae that forms the posterior border of the pelvis.

Coccyx

The human tailbone, resulting from the fusion of three to five small, irregularly shaped vertebrae.

Sternum

The breastbone, composed of the fusion of the manubrium, body, and xiphoid process.

True Ribs

The first seven pairs of ribs (1–7) that attach directly to the sternum by their own costal cartilages.

False Ribs

Rib pairs 8–12; they either have indirect cartilage attachments to the sternum or no sternal attachment.

Floating Ribs

Rib pairs 11 and 12, which have no sternal attachment.

Pectoral Girdle

Consists of the clavicle and scapula; it provides high mobility for the upper limb but possesses less stability.

Humerus

The single long bone of the arm.

Radius

The lateral bone of the forearm when in the anatomical position.

Ulna

The medial bone of the forearm when in the anatomical position.

Pelvic Girdle

Formed by two hip (coxal) bones, each composed of the fused ilium, ischium, and pubis; built for strength, stability, and weight-bearing.

Acetabulum

The deep socket where the ilium, ischium, and pubis fuse, which receives the head of the femur.

Female Pelvis

Tilted forward and adapted for childbearing; features a broader pubic arch ($80^{\circ}-90^{\circ}$), a wider/shorter sacrum, and a wider/oval pelvic inlet.

Male Pelvis

Tilted less forward and adapted for a heavier build; features a narrow/heart-shaped pelvic inlet and a more acute pubic arch ($50^{\circ}-60^{\circ}$).

Femur

The strongest and heaviest bone in the body, located in the thigh.

Articulations

Also known as joints; the site where two or more bones meet to hold the skeleton together and allow movement.

Fibrous Joints

Joints where bones are joined by fibrous tissue and are mostly immovable, such as skull sutures and syndesmoses.

Cartilaginous Joints

Joints where bones are connected by cartilage and are slightly movable; examples include symphyses and synchondroses.

Synovial Joints

Freely movable joints (diarthroses) characterized by a fluid-filled joint cavity separating the articulating bones.

Origin

The stationary or less movable attachment point of a muscle to a bone.

Insertion

The more movable attachment point of a muscle; it moves toward the origin during contraction.

Flexion

A movement, generally in the sagittal plane, that decreases the angle of the joint and brings two bones closer together.

Extension

A movement that increases the angle or the distance between two bones or parts of the body.

Abduction

The movement of a limb away from the midline or median plane of the body in the frontal plane.

Adduction

The movement of a limb toward the body midline.

Rotation

The movement of a bone around its longitudinal axis; common in ball-and-socket joints and at the atlas/axis joint.

Supination

A movement of the forearm where the radius and ulna are parallel and the palm faces upward.

Pronation

A movement of the forearm where the radius rotates over the ulna and the palm faces downward.

Bursitis

Inflammation of a bursa, sometimes referred to as 'water on the knee'.

Sprain

An injury where the ligaments reinforcing a joint are damaged by excessive stretching or are torn.