Anatomy and Physiology: Joints

Name the two types of cartilaginous joints.

A cartilaginous joint, like a fibrous joint, lacks a synovial cavity; its articulating bones are connected by either fibrocartilage or hyaline cartilage; and it allows little or no movement. The two types of cartilaginous joints are: synchondroses symphyses A synchrondrosis is a cartilaginous joint in which the connecting material is hyaline cartilage. (An example is the epiphyseal plate). A symphysis is a cartilaginous joint in which the connecting material is a disc of fibrocartilage. Examples of this joint are the interverterbral discs and the pubic symphysis.

Define a sprain.

A sprain is the forcible wrenching or twisting of a joint that stretches or tears its ligaments but does not dislocate the bone. A strain is a stretched or partially torn muscle

Describe a typical synovial joint.

A synovial joint (diarthrosis) has a synovial (joint) cavity between the articulating bones; this joint is freely movable. Articular cartilage covers the bones at synovial joints. This cartilage reduces friction at the joint during movement and helps to absorb shock. The articular capsule surrounds a diarthrosis, encloses the synovial cavity, and unites the articulating bones. The articular capsule is composed of two layers—the outer fibrous capsule that may contain ligaments, and the inner synovial membrane that secretes a lubricating and joint-nourishing synovial fluid. The flexibility of the fibrous capsule permits considerable movement at a joint, whereas its great tensile strength helps to prevent bones from dislocating. Synovial fluid, secreted by the synovial membrane, lubricates and reduces friction in the joint and supplies nutrients to, and removes metabolic wastes from, the joint. Ligaments help hold bone to bone.

Describe abduction and adduction.

Abduction refers to a motion that pulls a structure or part away from the midline of the body. Adduction refers to a motion that pulls a structure or part toward the midline of the body, or towards the midline of a limb.

What is the purpose of articular discs?

Articular discs modify the shape of the joint surfaces of the articulating bones, help maintain the stability of the joint, and direct the flow of synovial fluid to areas of greatest friction.

Define the term articulation.

Articulation is the point of contact between bone, bone and cartilage, or bone and teeth.

Describe dorsiflexion and plantar flexion.

Dorsiflexion refers to bending of the foot at the ankle in the direction of the superior surface. Plantar flexion involves the bending of the foot at the ankle joint in the direction of the plantar surface.

Describe elevation and depression.

Elevation is an upward movement of a part of the body. Depression is a downward movement of a part of the body.

Review the divisions of fibrous and cartilaginous joints.

Fibrous - interosseous membrane - syndesmoses - sutures Cartilaginous - synchondroses - symphyses

Name the three types of fibrous joints and give an example of each.

Fibrous joints include the following types: sutures syndesmoses interosseous membrane A suture is a fibrous joint composed of a thin layer of dense fibrous connective tissue that unites skull bones. A synostosis is a suture joint that has ossified. An example of a synostosis is the frontal suture between the left and right sides of the frontal bone. A syndesmosis is a fibrous joint that has more fibrous connective tissue than in a suture. A slightly movable fibrous joint in which bones such as the tibia and fibula are joined together by connective tissue. An interosseous membrane is a sheet of dense irregular connective tissue joining two long bones (e.g., radius and ulna).

What are some characteristics of fibrous joints?

Fibrous joints lack a synovial cavity, their articulating bones are held together by fibrous connective tissue, and they permit little or no movement. They include: sutures syndesmoses interosseous membranes Recall that the major difference between connective tissue and cartilage is the existence of chondrocytes in lacunae. Fibrous joints are made of fibrous CONNECTIVE TISSUE. Cartilaginous joints are made of fibrous cartilage.

Describe flexion, extension and hyperextension.

Flexion - decreases the angle between body parts Extension - increases the angle between body parts

What are the four types of movements possible at synovial joints?

Gliding Angular movements Rotation Special movement

Describe inversion and eversion.

Inversion is movement of the soles medially at the intertarsal joints so that they face away from each other. Eversion is a movement of the soles laterally at the intertarsal joints so that they face away from each other.

Compare and contrast the terms synarthroses, amphiarthroses, and diarthroses.

Joints can be synarthroses (immovable), amphiarthroses (partially movable), or diarthroses (freely movable).

List the types of movements allowed by synovial joints and give examples of each.

Movements at synovial joints are grouped into the following four categories: 1. Gliding movements occur when relatively flat bone surfaces move back and forth, and from side to side with respect to one another. 2. Angular movements involve an increase or a decrease in the angle between articulating bones, and can include the following types: Extension Hyperextension Abduction Adduction Circumduction 3. Rotation involves a bone revolving around its own longitudinal axis. 4. Special movement occurs only at certain joints.

Where do the nerves which serve a joint commonly originate from?

Nerves that supply a joint are the same as those that supply the skeletal muscles that move the joint.

Describe the six subtypes of synovial joints.

Planar joints permit mainly side-to-side and back-and-forth gliding movements. In a hinge joint, the convex surface of one bone fits into a concave surface of another bone. In a pivot joint, a round or pointed surface of one bone fits into a ring formed by another bone and a ligament. In an ellipsoidal joint, an oval-shaped condyle of one bone fits into an elliptical cavity of another bone. A saddle joint includes one bone whose articular surface is saddle-shaped and another bone whose articular surface is shaped like a rider sitting in the saddle. In a ball-and-socket joint, the ball-shaped surface of one bone fits into the cuplike depression of another.

Describe protraction and retraction.

Protraction is a movement of a part of the body anteriorly in the transverse plane. Retraction is a movement of a protracted part back to the anatomical position.

How are joints defined, structurally?

Structurally, joints are classified as fibrous, cartilaginous, or synovial. Structural classification is based on the presence or absence of a synovial (joint) cavity and the type of connecting tissue.

Describe supination and pronation.

Supination is a movement of the forearm at the proximal and distal radioulnar joints in which the palm is turned anteriorly or superiorly. Pronation is a movement of the forearm at the proximal and distal radioulnar joints in which the distal end of the radius crosses over the distal end of the ulna, and the palm is turned posteriorly or inferiorly.

How are joints defined, functionally?

The functional classification of joints is based on the degree of movement permitted. Joints can be synarthroses (immovable), amphiarthroses (partially movable), or diarthroses (freely movable).