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Chapter 4 Skeletal System
4.4 Joints - The area where two bones are attached for the purpose of permitting body parts to move.
- range of motion is affected by the tightness of soft tissues crossing the joint
- direction of motion is determined by the structure of the bony articulation
- Three types of movement
1. Immovable joints – Synarthroses
2. Slightly movable joints – Amphiarthroses
3.
Freely Movable joints – Diarthroses
A.
Immovable joints – Synathroses
“ syn
” = together “ arthron
” = joint
1.
Fibrous joints – absorb shock – little or no movement
2.
Two types of immovable joints a.
Sutures – join irregularly grooved articulating bone sheets with fibrous tissues that ossify with age. Only sutures in the human body are in the skull. b.
Syndemoses = “held by bands” Held together by dense fibrous tissue bands that allow for very limited movement. Coracoacromial joint and distal tibiofibular joints in humans.
B.
Slightly movable joints – Amphiarthroses
“ amphi-
“ = on both sides
1.
Cartilaginous joints allow for slight motion and better shock absorption.
2.
Two types of Amphiarthroses a.
Synchondroses – “held by cartilage” Bones are held together by a thin layer of hyaline cartilage. Examples: sternocostal joints (ribs) and epiphyseal plates (growth plates) b.
Symphyses – Thin plates of hyaline cartilage separate a disc of fibrocartilage. Examples are vertebral joints and pubis symphysis.
C.
Freely Movable joints – Diarthroses Page 140 in text.
1.
Also called synovial joints due to all diarthroses being surrounded by an articular capsule with a synovial membrane lining secreting synovial fluid as a lubricant.
2.
Six different types of diarthroses – dependent on motion type a.
Gliding joint – articulating surfaces nearly flat, only movement permitted is gliding b.
Hinge joint – one surface is convex and one concave. Strong ligaments restrict movement to hinge like movement. c.
Pivot joint – permit rotation around one axis d.
Condyloid joint – one surface oval and convex shape, the other is concave. Allows flexion, extension, abduction, adduction, and circumduction. e.
Saddle joints
– both articulating surfaces are saddle shaped (“U”) – movement as with
Condyloid joints but with greater range of motion f.
Ball and socket joint
– most freely moveable in the body, opposite articulating surfaces are convex “ball” and concave “socket”.

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3.
Structures associated with diarthrotic joints: a.
Bursae – small capsules lined with synovial membranes. They hold synovial fluid to lubricate the joint. Most bursae separate tendon from the bone to reduce friction on the tendons. b.
Tendon sheath – double layer synovial structures separating tendons that lie close to bone.
Many long muscle tendons crossing the wrist and fingers are protected by tendon sheaths.
D.
Articular Tissues
1.
Articular fibrocartilage – disc shaped, known as a meniscus , located between articulating bones. a.
Help distribute forces evenly over the joint surfaces b.
Absorb shock at the joint c.
Examples include intervertebral discs and meniscus of the knee
2.
Tendons – structures that connect muscle to bone. Composed of collagen and elastic fibers, if crossing over a joint it helps with stability. Present in diarthrodial joints
3.
Ligaments – structures that connect bone to bone. Same composition as tendons, help with stability and present in diartrodial joints.