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TEST in ITINERE n. 1 2020

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JOINTS 4.b

JOINTS (articulations)

each of 206 bones (only exception of the hyoid bone in the neck) connected to at least one other

joints = location where bones come together: 1) some joints allow for movement between bones

(=articulating surfaces of the adjacent bones can move smoothly against each other, but are the least stable),

2) others designed for stability and providing for little or no movement (joined by connective tissue or cartilage).

Functional = describe

the degree of movement available between the bones, ranging from immobile, to slightly mobile, to freely moveable joints, related to the functional requirements for that joint ( immobile or slightly moveable joints serve to protect internal organs, give stability to the body, and allow for limited body movement, but freely moveable joints allow for much more extensive movements of body and limbs).

Classification of Joints

Structural = take

into account whether the adjacent bones are strongly anchored to each other by fibrous connective tissue or cartilage, or whether the adjacent bones articulate with each other within a fluid-filled space called a joint cavity.

1. fibrous joint = adjacent bones united by fibrous connective tissue.

2. cartilaginous joint = bones joined by hyaline cartilage or fibrocartilage.

3. synovial joint = articulating surfaces not directly connected, but instead come into contact with each other within a joint cavity that is filled with a lubricating fluid, allowing for free movement between the bones (most common joints of the body).

Structural Classification of Joints

based on whether the articulating surfaces of the adjacent bones are directly connected by fibrous connective tissue or cartilage, or whether the articulating surfaces contact each other within a fluidfilled joint cavity.

3 in structural classifications:





1. synarthrosis = immobile

2. amphiarthrosis = slightly moveable

3. diarthrosis = freely moveable

Functional Classification of Joints

determined by the amount of mobility found between the adjacent bones:

fibrous joints

cartilaginous joints

synovial joints


Functional Classification of Joints

1. Synarthrosis (functional)

= immobile nature of these joints provide for a strong union between articulating bones. This is important at locations where bones provide protection for internal organs: sutures (fibrous joints between bones of the skull that surround and protect the brain) and the manubriosternal joint (cartilaginous joint that unites manubrium and body of the sternum for heart protection).

2. Amphiarthrosis (functional)

= joint that has limited mobility: 1. cartilaginous joint

that unites bodies of adjacent vertebrae

2. pubic symphysis of the pelvis.

3. Diarthrosis (functional)

= freely mobile joint (include all synovial joints of the body, which provide the majority of body movements), most of them are found in the appendicular skeleton, thus giving the limbs a wide range of motion. divided into 3 categories, based on number of axes of motion 1. uniaxial joint only allows for a motion in a single plane (around a single

axis): elbow joint 2. biaxial joint allows for motions within two planes: metacarpophalangeal 3. multiaxial joint (polyaxial or triaxial joint) allows for the several

directions of movement: shoulder and hip joints

= adjacent bones directly connected to each other by fibrous connective tissue (thus bones do not have a joint cavity between them) with a gap between bones narrow or wide. 3 types: 1. suture = narrow fibrous joint found between most bones of the skull 2. syndesmosis = bones more widely separated but held together by a

narrow band of fibrous connective tissue called a ligament or a wide sheet of connective tissue called an interosseous membrane (between shaft regions of the long bones in the forearm and in the leg)

3. gomphosis = narrow fibrous joint between the roots of a tooth and the bony socket in the jaw into which the tooth fits.

a. Fibrous Joints (structural)

a1. Suture

= all joints of bones of the skull, except for the mandible, are joined to each other by a fibrous joint called a suture. The fibrous connective tissue found at a suture (“to bind or sew”) strongly unites the adjacent skull bones and thus helps to protect the brain and form the face. In adults, the skull bones are closely opposed and fibrous connective tissue fills the narrow gap between the bones. The suture is frequently convoluted, forming a tight union that prevents most movement between the bones. (functionally classified as a synarthrosis, although some sutures may allow for slight movements between the cranial bones).

a2. Syndesmosis

= type of fibrous joint in which 2 parallel bones are united to each other by fibrous connective tissue: gap between bones may be narrow, with bones joined by ligaments, or wide and filled in by a broad sheet of connective tissue called an interosseous membrane. The syndesmoses found in the forearm and leg serve to unite parallel bones and prevent their separation: however, a syndesmosis does not prevent all movement between bones, and thus this type of fibrous joint is functionally classified as an amphiarthrosis.

a3. Gomphosis = specialized fibrous joint that anchors the root of a tooth into its bony socket within maxillary (upper jaw) or mandible bone (lower jaw), also known as a peg-and-socket joint. Spanning between bony walls of socket and root of tooth are numerous short bands of dense connective tissue, each of which is called a periodontal ligament. Due to immobility gomphosis is functionally classified as a synarthrosis.

Fibrous Joints

a1. Suture

a2. Syndesmosis

Fibrous Joints

a3. Gomphosis

b. Cartilaginous Joints (structural)

= adjacent bones united by cartilage, a tough but flexible type of connective tissue, lacking a joint cavity 2 types of cartilaginous joints: 1. synchondrosis = bones are joined by hyaline cartilage (also places where

bone is united to a cartilage structure, such as between anterior end of a rib and costal cartilage of thoracic cage)

2. symphysis = bones joined by fibrocartilage

Cartilage: Characteristics

Develops from mesenchyme and consists of cells, connective tissue fibers, and ground substance

Nonvascular, gets nutrients via diffusion through ground connective tissue fibers, and ground substance

Performs numerous supportive functions Cells include chondrocytes and chondroblasts 3 types of cartilage:

1.hyaline

2.elastic

3.fibrocartilage



Perichondrium: Found on peripheries of hyaline and elastic cartilage Peripheral layer is dense vascular connective tissue with type I collagen Inner layer is chondrogenic and gives rise to chondroblasts that

secrete cartilage matrix

Articular hyaline cartilage of bones and fibrocartilage NOT lined by perichondrium


Cartilage Matrix Produced and maintained by chondrocytes and chondroblasts Contains large proteoglycan aggregates and is highly hydrated (high

water content) Allows diffusion and is semirigid shock absorber Adhesive glycoprotein chondronectin binds cells and fibrils to the

surrounding matrix Elastic cartilage provides structural support and increased flexibility


Cartilage Matrix


Cartilage Cells Primitive mesenchymal cells differentiate into chondroblasts that

synthesize matrix Mesenchyme also differentiates into fibroblasts of the perichondrium Mature cartilage cells, chondrocytes, become enclosed in lacunae Main function of chondrocytes is to maintain the cartilage matrix Inner layer of surrounding connective tissue perichondrium is

chondrogenic Cartilage grows by both interstitial and appositional growth

1. Hyaline Cartilage Most common in the body and

serves as a skeletal model for most bones

In developing bones, cartilage present in epiphyseal plates for bone growth in length

Replaced by bone during endochondral ossification

Contains type II collagen fibrils, which are not seen in histologic sections due to reflective index that is similar to that of ground substance

In adults, present on articular surfaces of bones, ends of ribs, nose, larynx, trachea, and bronchi

1. Hyaline Cartilage



Articular Cartilage


Articular cartilage

Articular hyaline cartilage has a complex structure formed by several different layers of cells. Its primary components are water, collagen type II and proteoglycans. In the uppermost zone (tangential zone) the chondrocytes are small and round and the collagen fibres are oriented parallel to the surface. In the deeper zone (radial) the chondrocytes are larger and arranged in vertical columns and the collagen fibres also have more vertical orientation. The deepest zone contains calcified cartilage which separate hyaline cartilage from subchondral bone.


Articular cartilage


Contains branching elastic fibers in matrix and is highly flexible

Found in external ear, auditory tube, epiglottis, and larynx

2. Elastic Cartilage




3. Fibrocartilage

Filled with dense bundles of type I collagen fibers that alternate with cartilage matrix

Provides tensile strength, bears weight, and resists compression

Found in intervertebral disks, symphysis pubis, and certain joints

3. Fibrocartilage

3. Fibrocartilage

b. Cartilaginous Joints (structural)

= adjacent bones united by cartilage, a tough but flexible type of connective tissue, lacking a joint cavity 2 types of cartilaginous joints: 1. synchondrosis = bones are joined by hyaline cartilage (also places where bone is

united to a cartilage structure, such as between anterior end of a rib and costal cartilage of thoracic cage)

2. symphysis = bones joined by fibrocartilage

b1. Synchondrosis

= bones joined together by hyaline cartilage, or where bone united to hyaline cartilage; may be: a. temporary = epiphyseal plate (growth plate) of a growing long bone, ie the region of growing hyaline cartilage that unites the diaphysis (shaft) of the bone to the epiphysis (end of the bone) [bone lengthening involves growth of the epiphyseal plate cartilage and its replacement by bone: for many years during childhood growth, the rates of cartilage growth and bone formation are equal and thus the epiphyseal plate does not change in overall thickness as the bone lengthens, during the late teens and early 20s, growth of the cartilage slows and eventually stops epiphyseal plate is then completely replaced by bone, and the diaphysis and epiphysis portions of the bone fuse together to form a single adult bone. This fusion of diaphysis and epiphysis = synostosis. Once this occurs, bone lengthening ceases.]

b1. Synchondrosis

b. permanent = found in the thoracic cage, like first sternocostal joint, where the first rib is anchored to the manubrium by its costal cartilage. (The articulations of the remaining costal cartilages to the sternum are all synovial joints.) Additional synchondroses are formed where the anterior end of the other 11 ribs is joined to its costal cartilage. [Unlike the temporary synchondroses of the epiphyseal plate, these permanent synchondroses retain their hyaline cartilage and thus do not ossify with age] Due to the lack of movement between the bone and cartilage, both temporary and permanent synchondroses are functionally classified as a synarthrosis.

b1. Synchondrosis (temporary)

b1. Synchondrosis (definitive)

b2. Symphysis

= cartilaginous joint where the bones are joined by fibrocartilage (= very strong because it contains numerous bundles of thick collagen fibers, thus giving it a much greater ability to resist pulling and bending forces when compared with hyaline cartilage) giving ability to strongly unite adjacent bones, but still allowing for limited movement to occur thus functionally classified as an amphiarthrosis.

b2. Symphysis

Gap separating the bones at symphysis may be narrow (pubic symphysis: the pubic portions of the right

and left hip bones of the pelvis are joined together by fibrocartilage across a narrow gap, and manubriosternal joint: fibrocartilage unites the manubrium and body portions

of the sternum) or wide (intervertebral symphysis between

bodies of adjacent vertebrae of the vertebral column: a thick pad of fibrocartilage called an intervertebral disc strongly unites adjacent vertebrae by filling the gap between them width of intervertebral symphysis allows for small movements between the adjacent vertebrae and provides cushioning between vertebrae)

b. Cartilaginous Joints

b1

b2

c. Synovial Joints (structural)

= most common type of joint in the body with structural characteristic of presence of a joint cavity (= fluid-filled space articulating surfaces of the bones contact each other) giving ability to move smoothly against each other, allowing for increased joint mobility.

Synovial Joints: Structural Features

characterized by presence of a joint cavity (walls of this space formed by the articular capsule = fibrous connective tissue structure that is attached to each bone just outside the area of the bone’s articulating surface).


bones of the joint articulate with each other within the joint cavity: friction between bones at a synovial joint is prevented by the presence of articular cartilage, a thin layer of hyaline cartilage that covers entire articulating surface of each bone, articular cartilages of each bone are not continuous with each other, acting like a coating over bone surface, allowing articulating bones to move smoothly against each other without damaging the underlying bone tissue.


lining inner surface of the articular capsule = thin synovial membrane with cells secreting synovial fluid (synovia = “a thick fluid”), a thick, slimy fluid providing lubrication to further reduce friction between the bones of the joint and also providing nourishment to the articular cartilage, which does not contain blood vessels.

synovial joint = functionally classified as a diarthrosis.


outside articulating surfaces, bones connected together by ligaments (= strong bands of fibrous connective tissue, strengtheing and supporting joint by anchoring bones together and preventing their separation, allowing for normal movements at a joint, but limiting range of these motions, thus preventing excessive or abnormal joint movements) classified based on their relationship to the fibrous articular capsule:

1. extrinsic = located outside of articular capsule,

2. intrinsic = fused to or incorporated into the wall of the articular capsule,

3. intracapsular ligament = located inside of articular capsule

at many synovial joints, additional support is provided by the muscles and their tendons (= dense connective tissue structure that attaches a muscle to bone) acting across the joint


articular disc, (generally small and oval-shaped), or meniscus, (Larger and C-shaped) = in few synovial joints, fibrocartilage structure located between the articulating bones serving several functions (depending on the specific joint): in some places, an articular disc may act to strongly unite the bones of the joint to each other (articular discs found at the sternoclavicular joint or between the distal ends of the radius and ulna bones) at other synovial joints, provide shock absorption and cushioning between the bones (each meniscus within the knee joint), finally, an articular disc can serve to smooth the movements between the articulating bones (temporomandibular joint)

Additional Structures Associated

with Synovial Joints

Fat pad = serving as a cushion between the bones


Additional Structures Associated

with Synovial Joints


Additional

Structures

Associated with

Synovial Joints


Additional Structures Associated with Synovial Joints


Bursa = thin connective tissue sac filled with lubricating

liquid, located outside of a synovial joint serving to prevent

friction between bones of joint and overlying muscle

tendons or skin, classified by their location: subcutaneous

bursa = located between skin and underlying bone,

allowing skin to move smoothly over the bone (prepatellar

bursa located over kneecap and olecranon bursa at the tip

of the elbow), submuscular bursa = found between a

muscle and an underlying bone, or between adjacent

muscles, preventing rubbing of the muscle during

movements (trochanteric bursa found at the lateral hip,

between the greater trochanter of the femur and the

overlying gluteus maximus muscle), subtendinous bursa =

between a tendon and a bone (subacromial bursa that

protects the tendon of shoulder muscle as it passes under

the acromion of the scapula, and the suprapatellar bursa

that separates the tendon of the large anterior thigh

muscle from the distal femur just above the knee).

tendon sheath = similar in structure to a bursa, but smaller,

a connective tissue sac that surrounds a muscle tendon at

places where the tendon crosses a joint, containing

lubricating fluid that allows for smooth motions of the

tendon during muscle contraction and joint movements.

Additional Structures

Associated with

Synovial Joints

Types of Synovial Joints subdivided based on shapes of articulating surfaces of the bones 6 types : 1. pivot, 2. hinge, 3. condyloid, 4. saddle, 5. plane, 6. ball-and socket

Types of Synovial Joints

perno,

cerniera,

condyloid,

sella,

piano,

sfera e presa

1. Synovial Joints Types: Pivot Joint

= rounded portion of a bone is enclosed within a ring formed partially by the articulation with another bone and partially by a ligament with bone rotating within this ring. since the rotation is around a single axis, pivot joints

are functionally classified as a uniaxial diarthrosis type of joint.

examples: 1.atlantoaxial joint, found between the C1 (atlas) and C2 (axis) vertebrae, where upward projecting dens of the axis articulates with the inner aspect of the atlas, where it is held in place by a ligament and rotation at this joint allows to turn head from side to side. 2.proximal radioulnar joint, where head of radius is largely encircled by a ligament that holds it in place as it articulates with the radial notch of the ulna, allowing rotation of radius for forearm movements.

Synovial Joints Types: Pivot Joint

= convex end of one bone articulates with the concave end of the adjoining bone , allowing only for bending and straightening motions along a single axis thus functionally classified as uniaxial joints Examples: 1. elbow joint, with the articulation

between the trochlea of the humerus and the trochlear notch of the ulna, 2. knee, 3. ankle, 4. interphalangeal joints between the phalanx bones of the fingers and toes.

2. Synovial Joints Types: Hinge Join

Synovial Joints Types: Hinge Join

= (ellipsoid joint), the shallow depression at the end of one bone articulates with a rounded structure from an adjacent bone or bones Functionally, condyloid joints are biaxial joints allowing

for 2 planes of movement (one movement involves bending and straightening of fingers or anterior-posterior movements of hand + second movement is a side-to-side movement, allowing spreading fingers apart and bringing them together, or moving hand in a medial-going or lateral-going direction).

Examples: 1. knuckle (metacarpophalangeal) joints of the hand between the distal end of a metacarpal bone and the proximal phalanx bone, 2. radiocarpal joint of the wrist, between shallow depression at the distal end of the radius bone and the rounded scaphoid, lunate, and triquetrum carpal bones (articulation area has a more oval [elliptical] shape).

3. Synovial Joints Types: Condyloid Joint

Synovial Joints Types: Condyloid Joint

= both articulating surfaces for bones have a saddle shape, which is concave in one direction and convex in the other, allowing 2 bones to fit together like a rider sitting on a saddle functionally classified as biaxial joints. Example: 1. first carpometacarpal joint, between the

trapezium (a carpal bone) and the first metacarpal bone at the base of the thumb (providing thumb ability to move away from the palm of the hand along two planes, thus, the thumb can move within the same plane as the palm of the hand, or it can jut out anteriorly, perpendicular to the palm: this movement of first carpometacarpal joint is what gives humans their distinctive “opposable” thumbs 2. sternoclavicular joint

4. Synovial Joints Types: Saddle Joint

Synovial Joints Types: Saddle Joint

= (gliding joint) articulating surfaces of bones are flat or slightly curved and of approximately same size, allowing bones to slide against each other, with motion usually small and tightly constrained by surrounding ligaments. based only on their shape, can allow multiple movements,

including rotation, thus being functionally classified as multiaxial joint (however, not all movements available to every plane joint due to limitations placed on it by ligaments or neighboring bones, thus, depending upon specific joint, a plane joint may exhibit

only a single type of movement or several movements). examples: 1. between the carpal bones (intercarpal

joints) of the wrist or tarsal bones (intertarsal joints) of the foot, 2. between clavicle and acromion of the scapula (acromioclavicular joint), 3. between the sup and inf articular processes of adjacent vertebrae (zygapophysial joints).

5. Synovial Joints Types: Plane Joint

Synovial Joints Types: Plane Joint

= joint with greatest range of motion, because rounded head of one bone (the ball) fits into the concave articulation (the socket) of the adjacent bone classified functionally as multiaxial joints Only examples: 1. hip (femur head articulates with the

acetabulum of hip bone) 2. glenohumeral (shoulder) joint (humerus head articulates with glenoid cavity of scapula).

femur + humerus able to move in both A-P and medial-lateral directions and also rotate around their long axis: shallow socket of glenoid cavity allows shoulder joint an extensive range of motion, but deep socket of acetabulum (+strong supporting ligaments of hip joint) serve to constrain movements of the femur, reflecting the need for stability and weight-bearing ability at the hip.

6. Synovial Joints Types: Ball-and-Socket Joint

Synovial Joints Types: Ball-and-Socket Joint

many types of movement that can occur at synovial joints generally paired, with one being the opposite of the other. always described in relation to anatomical position of the body [=upright stance, with upper limbs to the side of body and palms facing forward]

Types of Body Movements






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