Pima Medical Institute BIO 120 Hole’s Essentials of Human Anatomy & Physiology Bone Joints BIO 120 Lesson 7 – Skeletal System David Shier, Jackie Butler, Ricki Lewis, Hole’s Essentials of Human Anatomy & Physiology, 10th Ed. CopyrightThe McGraw-Hill Companies, Inc. Created by Dr. Melissa Eisenhauer, Trevecca Nazarene University

Joints A. Joints (articulations) are the functional junctions between bones. B. Joints enable a wide variety of body movements. C. Joints can be classified according to the degree of movement possible and can be immovable, slightly movable, or freely movable. Joints (articulations) are functional junctions between bones. They bind parts of the skeletal system, make possible bone growth, permit parts of the skeleton to change shape during childbirth, and enable the body to move in response to skeleton muscle contractions. Joints vary considerably in structure and function. If classified according to the degree of movement they make possible, joints can be immovable (synarthrotic), slightly movable (amphiarthrotic), or freely movable (diarthrotic). Joints also can be grouped according to the type of tissue (fibrous, cartilaginous, or synovial) that binds the bones together at each junction. Currently, this structural classification by tissue type is more commonly used.

Joints: continued D. Joints can also classified according to the type of tissue that binds them together. E. Fibrous Joints 1. Fibrous joints are held close together by dense connective tissue and are immovable (sutures of skull) or only slightly movable (joint between the distal tibia and fibula). Fibrous joints lie between bones that closely contract one another. A thin layer of dense connective tissue joins the bones at such joints, as in a suture between a pair of flat bones of the skull (see figure 7.34, slide 88). Generally, no appreciable movement (synarthrotic) takes place at a fibrous joint. Some fibrous joints, such as the joint in the leg between the distal ends of the tibia and fibula, have limited movement (amphiarthrotic).

Figure 7.34 (a) Fibrous joints called sutures (b) Connective tissue connects bones at the suture. Fibrous joints. The fibrous joints between the bones of the skull are immovable and are called sutures. A thin layer of connective tissue connects the bones at the suture. Figure 7.34

F. Cartilaginous Joints Joints: continued . F. Cartilaginous Joints 1. Hyaline cartilage or disks of fibrocartilage unite the bones in cartilaginous joints. 2. Intervertebral disks between vertebrae help absorb shock and are slightly movable. 3. Other examples of cartilaginous joints include the symphysis pubis and the first rib with the sternum. Hyaline cartilage, or fibrocartilage, connects the bones of cartilaginous joints. For example, joints of this type separate the vertebrae of the vertebral column. Each intervertebral disc is composed of a band of fibrocartilage (annulus fibrosus) surrounding a pulpy or gelantinous core (nucleus pulposus). The disc absorbs shocks and helps equalize pressure between adjacent vertebrae when the body moves (see figure 7.17, slide 46). Due to the slight flexibility of the discs, cartilaginous joints allow limited movement (amphiarthrotic), as when the back is bent forward or to the side or is twisted. Other examples of cartilaginous joints include the symphysis pubis and the first rib with the sternum.

Joints: continued G. Synovial Joints 1.  Most joints of the skeleton are synovial joints, which are more complex than fibrous or cartilaginous joints. 2. The articular ends of bone in a synovial joint are covered with hyaline cartilage. Most joints within the skeletal system are synovial joints, which allow free movement (diarthrotic). They are more complex structurally than fibrous or cartilaginous joints. The articular ends of the bones in a synovial joint are covered with hyaline cartilage (articular cartilage), and a surrounding, tubular capsule of dense connective tissue holds them together (figure 7.35, slide 91).

The generalized structure of a synovial joint. Figure 7.35 Synovial joint

Joints: continued . 3. A joint capsule consists of an outer layer of dense connective tissue that joins the periosteum, and an inner layer made up of synovial membrane. a. Synovial fluid has the consistency of egg whites and lubricates articulating surfaces within the joint. 4. Some synovial joints contain shock- absorbing pads of fibrocartilage called menisci. 5. Some synovial joints have fluid-filled sacs called bursae. This joint capsule is composed of an outer layer of ligaments and an inner lining of synovial membrane, which secretes synovial fluid. Having a consistency similar to that of uncooked egg white, synovial fluid lubricates joints. Some synovial joints have flattened, shock-absorbing pads of fibrocartilage called menisci between the articulating surfaces of the bones (see figure 7.36, slide 93). Such joints may also have fluid-filled sacs called bursae associated with them. Each bursa is lined with synovial membrane, which may be continuous with the synovial membrane of a nearby joint cavity. Bursae are commonly located between tendons and underlying bony prominences, as in the patella of the knee or the olecranon process of the elbow. They aid the movement of tendons that glide over these bony parts or over other tendons.

Figure 7.36 shows and names some of the bursae associated with the knee. Menisci separate the articulating surfaces of the femur and tibia. Several bursae are associated with the knee joint. Figure 7.36

Joints: continued 6. Based on the shapes of their parts and the movements they permit, synovial joints can be classified as follows: a. A ball-and-socket joint consists of a bone with a globular or egg- shaped head articulating with the cup-shaped cavity of another bone; a very wide range of motion is possible; examples include the hip and shoulder joint. Synovial joints are classified as follows: Ball-and-socket joint consists of a bone with a globular or slight egg-shaped head that articulates with the cup-shaped cavity of another bone. Such a joint allows a wider range of motion than does any other kind, permitting movements in all planes, as well as rotational movement around a central axis. The shoulder and hip have joints of this type (see figure 7.37, slide 98).

Synovial joints: continued b. A condyloid joint consists of an ovoid condyle fitting into an elliptical cavity, permitting a variety of motions; an example is the joint between a metacarpal and a phalange. c. Gliding joints occur where articulating surfaces are nearly flat or slightly curved, allowing a back-and-forth motion; the joints of the wrist and ankle, as well as those between vertebrae, are gliding joints. In a condyloid joint or ellipsoidal joint, an oval-shaped condyle of one bone fits into an elliptical cavity of another bone, such as in the joints between the metacarpals and phalanges (figure 7.37, slide 98). This type of joint permits a variety of movements in different planes; rotational movement, however, is not possible. The articulating surfaces of gliding joints, or plane joints, are nearly flat or slight curved. Most of the joints within the wrist (see figure 7.37, slide 98) and ankle, as well as those between the articular processes of adjacent vertebrae, belong to this group,. They allow sliding and twisting movements. The sacroiliac joints and the joints formed by ribs 2-7 connecting with the sternum are also gliding joints.

Synovial joints: continued d. In a hinge joint, a convex surface fits into a concave surface, as is found in the elbow and phalange joints; movement is in one plane only. e. In a pivot joint, a cylindrical surface rotates within a ring of bone and fibrous tissue; examples include the joint between the proximal ends of the radius and ulna. In a hinge joint, the convex surface of one bone fits into the concave surface of another, as in the elbow (see figure 7.37) and the joints of the phalanges. Such a joint resembles the hinge of a door in that it permits movement in one plane only. In a pivot joint, the cylindrical surface of one bone rotates within a ring formed of bone and ligament. Movement is limited to the rotation around a central axis, the joint between the proximal ends of the radius and the ulna is of this type (see figure 7.37, slide 98).

Synovial joints: continued f. A saddle joint forms where articulating surfaces have both concave and convex areas, permitting a wide range of movements; the joint between the trapezium and the metacarpal of the thumb is of this type. A saddle joint forms between bones whose articulating surfaces have both concave and convex regions. the surface of one bone fits the complementary surface of the other. This physical relationship permits a variety of movements, as in the joint between the carpal (trapezium) and metacarpal bones of the thumb (see figure 7.37).

Figure 7.37 types and examples of synovial (freely movable) joints.

Types of Joints Table 7.4 summarizes the types of joints.

H. Types of Joint Movements. 1 H. Types of Joint Movements 1. When a muscle contracts, its fibers pull its movable end (insertion) toward its stationary end (origin), causing movement at a joint. 2. These terms describe movements that occur at joints: flexion, extension, dorsiflexion, plantar flexion, hyperextension, abduction, adduction, rotation, circumduction, pronation, supination, eversion, inversion, retraction, protraction, elevation, and depression. Skeletal muscle action produces movement at synovial joints. Typically, one end of a muscle is attached to a relatively immovable or fixed part on one side of a joint, and the other end of the muscle is fastened to a moveable part on the other side. When the muscle contracts, its fibers pull its movable end, the insertion, toward its fixed end, the origin, and a movement occurs at the joint.

Joint movements adduction, abduction, dorsiflexion, plantar flexion, hyperextension, extension, and flexion Figure 7.38

Joint movements: rotation, circumduction, supination, and pronation. Figure 7.39

Joint movement: eversion, inversion, retraction, protraction, elevation, and depression. Figure 7.40

Skeletal System Relationship of skeletal system to all other systems… Bones provide support, protection, and movement and also play a role in calcium balance