Joints of the Skeletal System - Bio-Guru

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Transcript Joints of the Skeletal System - Bio-Guru

Joints of the Skeletal System

Chapter 8

What’s a Joint? Is it legal?

• • •

Functional junctions between bones Also called articulations Classified by the type of tissue that attaches the bones at the junction

Also classified by the way in which they move at

Joints Classified by Tissue




• • •

Fibrous Joints

Dense connective tissue abundant in collagenous fibers found in these joints Usually found between bones that lie very close to each other 3 types of fibrous joints: Syndesmosis, Suture and Gomphosis • •

Cartilaginous Joints

Either Hyaline cartilage or Fibrocartilage connects the bones in these joints 2 types of cartilaginous joints: Synchondrosis and Symphysis • • • • •

Synovial Joints

The most common type of joint in the skeletal system

Allow free movement More complex than fibrous or cartilaginous joints Consist of: 1) articular cartilage 2) Joint capsule 3) synovial membrane that secretes synovial fluid 6 types of synovial joints: Ball-and-socket, Condyloid, Gliding joint, Hinge joint, Pivot joint, and Saddle joint.

Joints Classified by Degree of Movement

• • •

Synarthrotic – immovable Amphiarthrotic – partially movable Diarthrotic – freely movable

Fibrous Joints

1. Syndesmosis • • Amphiarthrotic (allows slight movement) Bones in this type of joint are connected to each other with long stands of connective tissue that are collectively called an interosseous ligament (between bones) • Found in places such as the distal ends of fibula and tibia, between the tarsals and carpals



Fibrous Joints

2. Suture • • • Synarthrotic - immovable Exist between flat bones of the skull only – joined by a thin layer of dense connective tissue Starts out as a fontanel – wide membranes of dense connective tissue between the skull bones, and allows compression of skull during childbirth, as well as room for growth • Fontanels are replaced by sutures


Fibrous Joints

3. Gomphosis • • Synarthrotic - immovable A strange joint that is formed when a cone shaped process of a bone is located within a socket of another bone • The root of a tooth located within the jawbone and held together by the periodontal ligament is a good example

Tooth enamel


Blood vessels and nerve endings Periodontal ligament Root of tooth Jawbone

Cartilaginous Joints

1. Synchondrosis • • • • Synarthrotic – immovable Bands of hyaline cartilage join parts of bones Much of this cartilage disappears upon maturity Example: epiphyseal plate – replaced by bone when full growth is reached (before age 25) – no more movement after this point • Another example: articulation between manubrium and first rib by costal cartilage (also synarthrotic and permanent)


Cartilaginous Joints

2. Symphysis • • Amphiarthrotic – slightly movable Bones that meet at these joints have a layer of hyaline cartilage covering their ends • The hyaline cartilage is also attached to a pad of fibrocartilage which allows a “spring” to movement • Examples: Pubic symphasis and joints formed between adjacent vertebrae separated by intervertebral discs Intervertebral discs are also made up of fibrocartilage that surrounds a gelatinous core


Synovial Joints

• Diarthrotic – freely moving • Most common type of joint in the body • More complex than fibrous and cartilaginous joints • Consist of: – Articular cartilage – Joint capsule – Synovial membrane

Synovial Joints

• Articular cartilage – made up of hyaline cartilage and cover the articular surfaces of bones in the joint – these bone ends are made up of spongy bone (like in epiphysis). The articular cartilage minimizes friction and wear • Joint Capsule – Holds the bones in a synovial joint together. – The outer layer of the capsule is made up of dense connective tissue and reinforced with collagenous fibers called ligaments. The outer layer attaches to the periosteum of the bones in the joint – A inner layer of the joint capsule is made of a shiny vascular lining of loose connective tissue called the synovial membrane • Synovial Membrane – only a few cells thick, surrounds a closed sac called the synovial cavity that is filled with synovial fluid (secreted by the cells of the synovial membrane

A Typical Synovial Joint


Some synovial joints…

• Are divided (partially or completely) into 2 compartments by discs of fibrocartilage called menisci or meniscus (singular). These are located between the articular surfaces of the bones • Found in joints like the knee, where the menisci cushion the articulating surfaces • Other synovial joints have synovial fluid filled sacs called bursae


them – usually between the skin and the bones of the synovial joint

Meniscus and Bursa

• Menisci are crescent-shaped and attach to the joint capsule on its lateral sides

View of menisci from the top

Synovial fluid

• A thick, stringy fluid found in the cavities of synovial joints. With its egg-like consistency (


comes from Latin for “egg"), synovial fluid reduces friction between the articular cartilage and other tissues in joints to lubricate and cushion them during movement. • Normal synovial fluid contains hyaluronic acid and a glycoprotein called Lubricin • Synovial fluid is secreted by cells of the synovial membrane and supply nutrients to the articular cartilage (remember – the synovial membrane is made of loose connective tissue and therefore has blood vessels)

Arthrocentesis: extraction of synovial fluid from joint

The sample can be examined to determine the cause of joint problems

pus-like fluid aspirated from a patient with acute bacterial infectious arthritis cloudy but translucent inflammatory synovial fluid taken from a patient with rheumatoid arthritis (left) and gout (right) respectively.

bloody fluid aspirated from a patient with a tibial fracture into the joint space

Types of Synovial Joints

• • •

1. Hinge Joint

Movement in one plane only Convex surface of one bone fits into concave surface of another Example: trochlea of humerus into trochlear notch of ulna

2. Gliding Joint

• Articulating surfaces of both bones in this joint are almost flat – or maybe very slightly curved • Back-and-forth and twisting movements • Example – carpals, tarsals, vertebrae, clavicle

3. Saddle Joint

• Between bones that have both concave as well as convex regions on their articulating surfaces • 2 planes of movement – Forward and back – Side-to-side

4. Ball-and-Socket Joint

• Bone with a round protrusion at the articular end fits into a cup-shaped cavity of another bone • Movement in all planes • Example: femur head and acetabulum of coxa

5. Pivot Joint

• Cylindrical surface of one bone rotates within another bone • Examples: the dens (odontoid process) of the axis within a facet of the atlas

6. Condyloid Joint

• A condyle of one bone articulates with an elliptical cavity of another bone • Example: Joints between carpals and metacarpals, Occipital condyles with facets of atlas

Types of Joint Movement

• Flexion – Bending the lower limb at the knee or bending the hand downward at the wrist • Extension – Straightening lower limb at the knee or straightening the hand at the wrist • Hyperextension – Moving head upward, toward back or hand toward upper arm • Dorsiflexion – bending foot upward, toward the shin • Plantar Flexion – bending foot downward, toward the heel • Abduction – Moving a leg away from midline, horizontally • Adduction – Returning leg from horizontal position back to midline • Rotation – twisting head from side to side • Circumduction – moving finger in a circular motion without moving hand • Supination – palms facing anteriorly • Pronation – palms facing posteriorly • Eversion – Pushing foot away from body laterally • Inversion – Pushing foot laterally toward body (medially) • Protraction – Pushing chin forward • Retraction – Pulling chin back • Elevation – Raising, Shrugging shoulders • Depression – lowering, drooping shoulders



Supination vs. Pronation

Supination: Palm faces upward Pronation: Palm faces downward

Extension, Hyperextension, and Flexion

Another example: raising and lowering of hand, without moving arm

Dorsiflexion vs. Plantar flexion

Abduction, Adduction, and Circumduction


Inversion vs. Eversion

Protraction vs. Retraction

Elevation vs. Depression

Another example: Shrugging and relaxing of shoulders


Examples of Synovial Joints

I. Shoulder Joint – Includes the glenoid cavity of the Scapula and the head of the humerus . It is a Ball-and socket joint.

– The joint capsule is attached to the circumference of the glenoid cavity of the scapula and the anatomical neck of the humerus – The joint capsule is reinforced by several ligaments and tendons of muscles to create a

rotator cuff

which supports the shoulder joint

Ligaments of the Shoulder Joint

1. Coracohumeral

– connects the coracoid process of the scapula to the greater tubercle of the humerus

Coracoid process Acomion process Greater tubercle of humerus Coracohumeral Ligament MADE UP OF CONNECTIVE TISSUE

2. Glenohumeral Ligament

• These 3 bands of ligament fibers extend from the edge of the glenoid cavity of the scapula to the lesser tubercle and the anatomical head of the humerus

Acromion Process Clavicle Coracoid process Glenohumeral Ligament MADE UP OF CONNECTIVE TISSUE

3. Transverse Humeral Ligament

• Connects the greater and lesser tubercles of the humerus

Acomion process Greater tubercle of humerus Coracoid process Lesser Tubercle of humerus Transverse Humeral Ligament MADE UP OF CONNECTIVE TISSUE

4. Glenoid Labrum

Joint Capsule

• Attaches along the circumference of the glenoid cavity of the scapula and forms a cup-like shape with a free rim

Glenoid Labrum MADE OF FIBROCARTILAGE Glenoid cavity


• There are several bursae associated with the shoulder joint. The major ones are: – Subscapular bursa – Subdeltoid bursa – Subacromial bursa – Subcoracoid bursa

II. Elbow Joint

Has 2 articulations: • The hinge joint between the trochlea of the humerus and the trochlear notch of the ulna • The gliding joint between the capitulum of the humerus and the fovea on the head of the radius A joint capsule encloses the joint and it is reinforced by ulnar and radial ligaments and muscle fibers form the brachialis muscle

The Elbow Joint

Capitulum Trochlea Trochlear notch


Ligaments of the Elbow Joint

Ulnar Collateral Ligament - Located in the medial wall of the joint capsule - thick band of dense connective tissue - anterior portion of the ligament joins the medial epicondyle of the humerus to the medial margin of the coronoid process of the ulna - The posterior portion of the ligament joins the medial epicondyle of the humerus to the olecranon process of the ulna

Coronoid process of ulna Olecranon process of ulna Medial epicondyle

2. Radial Collateral Ligament

• Located in the lateral wall of the elbow joint capsule • Fibrous band that extends between the lateral epicondyle of the humerus and the annular ligament of the radius – The annular ligament of the radius joins the edge of the trochlear notch of the ulna and envelopes the head of the radius

Annular ligament of the radius

Types of Movement at the Elbow

• The humerus and the ulna are a hinge joint and can only allow flexion and extension.

• The Radius moves freely inside the annular ligament - this allows the pronation and supination of the hand.

Bursa of the elbow

The Hip Joint

• Ball-and-socket joint – head of femur into acetabulum of coxa • Heavy, cylindrical joint capsule surrounds the neck of the femur with the edge of the acetabulum.

• The joint capsule is reinforced by ligaments such as the pubofemoral ligament

Hip Joint Capsule

Ligaments of the Hip Joint

1. Ligamentum Capitis (

ligamentum teres femoris

) • Attaches the pit in the femur head (fovea capitis) to the inside of the acetabulum of the coxa • Carries blood vessels to the head of the femur • Not very essential in holding the joint together – not known for strength

2. Acetabular Labrum

• Horse-shoe shaped ring of fibrocartilage • Attaches to the edge of the acetabulum and makes it deeper • Encloses head of femur and holds it in place • Remember the glenoid labrum? Similar setup to that

3. Iliofemoral Ligament

• Strongest ligament in the body!

• Y-shaped band of fibers • Connect the anterior inferior iliac spine of the coxa to the bony line between the greater and lesser trochanters of the femur

4. Pubofemoral ligament

• Joins the superior portion of the pubis and the iliofemoral ligament

5. Ischiofemoral Ligament

• Connects the ischium behind the acetabulum and joins the fibers of the joint capsule

Iliofemoral Ligament Bursa Pubofemoral Ligament

Knee Joint

• Largest and most complex synovial joint • Medial and lateral condyles of the femur’s distal end articulate with the medial and lateral condyles of the proximal end of the tibia • Femur also articulates with the patella • Knee is a joint with multiple movements – hinge joint - flexion and extension – Condyloid - allows some rotation (between femur and tibia) – and a gliding joint (between femur and patella) • Joint Capsule – relatively thin, but strengthened by ligaments and tendons

Ligaments of the Knee Joint

1. Patellar Ligament • The fibers of this ligament are fused with the fibers of a tendon (from the thigh muscle quadriceps femoris) • Strong flat band that extends from the edge of the patella, to the tibial tuberosity

Patellar Ligament

2. Oblique Popliteal

• Connects the lateral condyle of the femur to the edge of the head of the tibia (posterior side of knee)

Oblique Popliteal Ligament

3. Arcuate Popliteal Ligament

• Y-shaped ligament that extends from the lateral condyle of femur to the head of the fibula

Arcuate Popliteal Ligament

4. Tibial(medial) Collateral Ligament

Broad, flat ligament that extends from the medial epicondyle of the femur to the medial condyle of the tibia 5. Fibular (Lateral) Collateral Ligament • Extends between lateral epicondyle of femur to head of fibula