The Articular System: Introduction, Cartilaginous Joints and Amphiarthrosis, Synovial Joints and Diarthrosis, and the Anatomical Movements of the Body PDF

Preview

Summary

This is the lecture part of the General Anatomy Class. It is composed of the articular system of the human body. It includes the introduction, amphiarthrosis, diarthrosis, and the anatomical movement of the body....

Description

M4: Introduction Arthrology is a term derived from the ancient Greek word arthros (meaning “articulated”). When 2 bones are joined together at different parts of their surfaces, it forms an articulation or joint. Articular system refers to the study of the structures that hold bones allowing body movement in varying degrees. Aside from movement, a joint function also for stability and protection of internal organs. The absence of movement or slight movement in the joints provide strong union between bones. Cranial vault is formed by the bones of the skull that protects the brain and in the pelvic region, the joint that exist between the pubis provides for the weight bearing stability of the pelvis. Joints or articulation are classified according to their structure and function. Structural classification of joints is based on the material that joins the articulating surfaces of bones. Bones may be held together by a fibrous tissue or cartilage or a lubricating fluid is present in the cavity. A fibrous joint is held together by a dense connective tissue consisting of collagen fiber. In a cartilaginous joint a hyaline cartilage or fibrocartilage is between the 2 bones. A cartilage is described as a tough but flexible type of connective tissue. A synovial joint unites together bones with a fibrous joint capsule that is continuous with the periosteum of the adjoining bones. It constitutes the outer boundary of a synovial cavity, and surrounds the bones' articulating surfaces. The inner layer of the capsule forms the synovial membrane, which secretes and seals in the synovial fluid. An articular disk may completely or partially separate the articulating bones. Ligaments support the joint by holding the bones together and resisting excess or abnormal joint motions. Functional classification of joint is based on the movement produced by the joint. Joint is classified as synarthrosis, amphiarthrosis and diarthrosis. Synarthrosis is a type of joint where there is little or no movement at all. The absence of cavity or space between articulating surfaces makes the joint immobile. However, this contributes to a solid and sturdy joint protecting the internal organs like the cranial cavity where the brain is lodged. Amphiarthrosis are joints with slight or limited movement. The gap between bones is filled by a cartilage that is capable of withstanding great amount of pressure & tension brought by the movement. This stabilizes the joint to cushion the impact of movement in the joint. Diarthrosis are joints capable

of movement in different anatomical axes. This type of joint allows movement in the 3 anatomical planes namely frontal, transverse and sagittal. However, this range of motion in different planes makes it the weakest among the joints mentioned. Lesson 1 Fibrous Joint and Synarthrosis A fibrous joint is characterized by the presence of a fibrous tissue that holds the bones together. The fibers joining the bones may be short or long, thus the gap between bones at fibrous joints vary from narrow to wide. Most of the fibrous joint are synarthrosis joint where there is little or no movement at all. Examples: 1. Sutures 2. Syndesmoses 3. Gomphoses 4. Schindylesis

Sutures A form of articulation where the narrow gap between the margins of the bones is united by a thin layer of fibrous tissue. All the bones of the skull except the mandible are joined by suture. It forms the cranial vault and forms the face. 1. Sutura Vera / True Suture The margins of the bones are connected by a series of processes, and indentations interlocked together. Examples are sagittal suture and coronal suture

2. Sutura Notha/ False Suture The articulation is formed by roughened surfaces placed in apposition with one another. Examples of this are squamosal suture and intermaxillary suture

Syndesmoses This joint occurs between 2 parallel bones where the space varies from narrow to wide. In a narrow gap, a strap of fibrous connective tissues called ligament unites the bone. If the gap between bones is wide it is called an interosseous membrane. These bands of connective tissue can restrict movements of the joint or it can stretch repeatedly and return to their original forms. Example is between radius and ulna

Gomphosis/Peg and Socket Joint A type of articulation formed by the insertion of a conical process into a socket. The narrow space is filled by periodontal ligament. Example is root of tooth fits into the sockets of the alveolus like a peg

Schindylesis A form of articulation in which a thin plate of bone is received into a groove or slit in another. Examples are between sphenoid & perpendicular plate of ethmoid with vomer, between the perpendicular plate of ethmoid into the fissure between maxilla & palatine

Lesson 2 Cartilaginous Joint and Amphiarthrosis A cartilaginous joint is characterized by a broad, flat piece of fibrocartilage or a hyaline cartilage. There is no joint cavity however, the space filled by the fibrocartilage cushions the joint and allows some movement. The bodies of the vertebra and pubis are held by fibrocartilage. Movements of this joint though little it may be, provides stability and strength to the joint. According to function, these are classified as amphiarthrosis joint. On the contrary, though a joint is united by a hyaline cartilage but lacking in movement, as can be seen between a bone and a cartilage, the joint is functionally classified as synarthrosis joint. Types of Cartilaginous Joint: 1. Synchondrosis 2. Symphysis Synchondrosis The bones in synchondrosis are joined together by hyaline cartilage, or where bone is united to hyaline cartilage. It is a temporary form of joint if the cartilage is converted into bone before adult life, a synostosis type of joint. Permanent synchondrosis is when the hyaline cartilage remains a cartilage throughout life and did not ossify with age Example for temporary synchondrosis is at epiphyseal plates while for permanent synchondrosis is between the sternum and first rib.

Symphyses It is a type of joint where bones are united together by fibrocartilage. Movement is possible because fibrocartilage contains numerous bundles of thick collagen fibers that provides a much greater ability to resist pulling and bending forces. Examples of a fibrocartilage are the intervertebral disc and symphysis pubis. Functionally, it is classified as amphiarthrosis as seen from the movements along the vertebral column, at the pelvis and sternum.

Lesson 3 Synovial Joint and Diarthrosis A synovial joint is characterized by the presence of a cavity. The adjoining bones are not directly connected with each other. An articular capsule surrounds the joint. The outer layer may contain ligaments and the inner layer secretes the synovial fluid that acts as a lubricant and nourishment to the joint as well as a shock absorber. The articulating ends of the bone are covered with articular cartilage that reduces friction during movement and facilitates transmission of load to the underlying bone. Accessory structures of the joint include tendon, ligament, and bursa. Synovial joints allows movement in various planes thus all synovial joints are functionally classified as diarthrosis. This is the most common type of joint, a freely movable joint. It is capable of the greatest movement of the three structural joint types; however, it is said that the more mobile a joint is, the weaker the joint is. Types of Diarthrosis  Planar  Hinge  Pivot  Condyloid  Saddle  Ball and Socket

Planar Joints The articulating surfaces of the bones are flat or slightly curved which allow gliding movements; therefore, the joints are sometimes referred to as gliding joints. Range of motion is limited and does not involve rotation Examples: carpal bones (except that of the capitate with the navicular and lunate) and the intertarsal bones (except that between talus & navicular), between articular processes of vertebrae, acromioclavicular, intermetacarpal, proximal tibiofibular

Hinge/ Ginglymus Joints The articulating end of a bone is slightly-rounded, fitting into the slightly-hollow end of the other bone. One bone moves while the other bone remains stationary, similar to the hinge of a door Examples: elbow joint & knee joint, interphalangeal joints

Pivot Joints The joint is between the rounded end of a bone fitting into a ring formed by the other bone. The pivot joint allows rotational movement, as the rounded bone moves around its own axis. Examples: atlantoaxial joint, proximal radioulnar articulation

Condyloid /Ellipsoid Joint The joint is formed between a bone with an oval-shaped end fitting into a similarly oval-shaped hollow of another bone. This joint allows angular movement along two axis (permit of flexion, extension, adduction, abduction, and circumduction, but no axial rotation) Example: radiocarpal joint, metacarpophalangeal joint, atlanto-occipital joint

Saddle Joints As the term suggests, it resembles a saddle, the articulating surface of a bone is concave and the other bone has a convex surface that fits together. The joint allow angular movements similar to condyloid joints, but with a greater range of motion Example: thumb joint ( trapeziometacarpal joint) , sternoclavicular joint

Ball-and-Socket / Enarthrosis Joints The articulating surface of one bone possesses a rounded, ball-like end fitting into a cup-like socket of another bone. The joint allows the greatest range of motion, as all movement types are possible in all directions Examples: shoulder and hip joints.

Lesson 4 Anatomical Movements of the Body Diarthrosis is a freely movable joint and it covers all the synovial joints in the body. The joint between the long bones of the appendicular skeleton exhibits most of the movements descriptive of the diarthrosis joint. Other movements possible in the synovial joint includes gliding, angular, rotational, or special movement namely inversion, eversion, protraction, retraction, elevation, depression, supination, pronation, dorsiflexion, plantarflexion and opposition. Gliding Movement Occur as relatively flat bone surfaces move past each other and it produces very little rotational or angular movement of the bones. Example : joints of the carpal and tarsal bones

Angular Movement Produced by changing the angle between the bones of a joint and commonly seen in the long bones. The different types of angular movements include flexion, extension, hyperextension, abduction, adduction, and circumduction.

a. Flexion or bending It occurs when the angle between the bones decreases as in moving the forearm upward at the elbow or moving the wrist to move the hand toward the forearm. b. Extension The opposite of flexion where the angle between the bones of a joint increases like straightening a limb after flexion. Extending a part of the body past the normal anatomical position is referred to as hyperextension c. Abduction When a bone moves away from the midline of the body as in moving the arms or legs laterally to lift them straight out to the side

d. Adduction When a bone moves toward the midline of the body as in moving the limbs inward after abduction e. Rotational Movement The movement of a bone as it rotates around its longitudinal axis. Rotating toward the midline of the body is called medial rotation while rotating away from the midline of the body is called lateral rotation

f. Circumduction Refers to the movement of a limb in a circular motion, as in swinging an arm around

Lesson 4 Special Movements Special Movements Cannot be classified as gliding, angular, or rotational are called special movements. Supination Movement of the radius and ulna bones of the forearm so that the palm faces forward or up. (lateral rotation of forearm) Pronation Opposite movement in which the palm faces backward or down. (medial rotation of forearm)

Protraction Refers to anterior movement of a bone in the horizontal plane Retraction It occurs as a joint moves back into position after protraction. *Protraction and retraction can be seen in the movement of the mandible as the jaw is thrust outwards and then back inwards. Opposition Movement of the thumb toward the fingers of the same hand

Inversion It involves moving the soles of the feet inward, toward the midline of the body (medial rotation of foot) Eversion The opposite of inversion, involves moving of the sole of the foot outward, away from the midline of the body (lateral rotation of foot)

Elevation Movement of a bone upward, such as shrugging the shoulders or lifting the scapulae. Depression Opposite of elevation and involves moving the bone downward, such as after the shoulders are shrugged and the scapulae return to their normal position from an elevated position.

Dorsiflexion Bending at the ankle such that the toes are lifted toward the knee. Plantarflexion Bending at the ankle when the heel is lifted, such as when standing on the toes

Lesson 4 : Range of Motions Ranges of Motion Four general classifications of joint movements based on their location 1. Nonaxial Arthrodia/gliding- the bones slide over each other as in the case of flat bones Examples:  between the carpal bones of the wrist  between the carpals and the metacarpals of the palm  between the tarsal bones of the ankle  between the tarsals and the metatarsals of the foot  acromioclavicular (AC) joint of the shoulder  between the sternum (breast bone) and ribs at the sternocostal joints  between the vertebrae and ribs at the vertebrocostal joints  facets of the twenty-six vertebrae at the intervertebral joints.

2. Uniaxial: movement occurs on one plane Hinge joint : flexion & extension (transverse)  between the proximal ends of the ulna and radius Pivot : rotational (longitudinal)  between atlas and axis 3. Biaxial: moves about two distinct axes (biaxial) Condyloid and Saddle : flexion, extension, abduction, adduction 4. Polyaxial/ Multiaxial: moves on all three axis ( transverse, sagittal & frontal planes) Enarthrosis or ball-and-socket joint : flexion, extension, abduction, adduction limbs - adduction, abduction, extension and flexion...