An Introduction to Human Biology (Joints)

7/30/2019 An Introduction to Human Biology (Joints)

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Joints


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Types of the Joint

Joint: articulation between two or more

bones which allows more or less motion

Classified into 3 types, based on the

connecting soft tissues:

Fibrous Joint

Cartilaginous Joint

Synovial Joint


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Fibrous Joint

united by dense

connective tissue

consisting of

collagen fibers

NO JOINT CAVITY

immoveable (most)


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Fibrous Joint

Three subtypes of fibrous joints:

Suture, e.g: skull

Syndesmosis, e.g: interosseous

membrane,tibia/fibula joint

Gomphosis, e.g: the articulations of teethwith their alveolar sockets in the mandible

or the maxillae


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Cartilaginous Joint

united with each

other by cartilage

NO JOINT CAVITY


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Cartilaginous Joint

Two subtypes of cartilaginous joints:

Synchondroses (primary cartilaginous joint) only hyaline cartilage is involved

Immoveable e.g:epiphyseal plate,joint between first

rib&sternum

Symphyses (secondary cartilaginous joint) involves both hyaline and fibrocartilage

limited movement is permitted

e.g: pubic symphysis, intervertebral discs


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Synovial Joint

majority ofarticulationsbetween bones

freely moveablejoints (ALL)

characterized by thepresence of thesynovial cavity


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Synovial Joint

Components:

The articulating surfaces,

covered by hyaline

cartilage (articular

cartilage)

synovial fluid, secreted by

the synovial membrane

the articular capsule:synovial membrane (the

inner layer) & fibrous

capsule (the outer layer)

bursae in between


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Synovial Joint

Three factors determine thestrength or stability of thesynovial joint & the range ofmovement:

1. The shape of the articular

surfaces of the bones

2. The ligaments (strongbands of dense fibrousconnective tissue which bind

the adjacent bones together)

3. Muscles


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Synovial Joint

According to the shape of the articulatingsurfacesix majorcategories of synovial joint:

Ball & socket

Hinge

Pivot

Gliding

Ellipsoidal (condyloid)

Saddle


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Hinge Joint

Convex surface of one

bone fits smoothly into

concave surface of the

second bone

the joints are uniaxial

flexion/extension


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Ball and Socket Joint

Ball-shaped head fits into

a cup-shaped depression

Multiaxial (all

axes&planes):

flexion/extension,

adduction/abduction,

circumduction and

rotation

Found in the hips andshoulders


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Gliding Joint

Opposite bone surfacesare flat or slightly curved

Only sliding motion in

all directions areallowed

Since there is no bonemovement around an

axis, the joints arenonaxial

Midcarpal and midtarsaljoints are gliding joints


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Saddle Joint

First bone's articular surfaceis concave in one direction and

convex in the other while the

second bone is just the

opposite (like a saddle&itsrider)

Biaxial joint:

flexion/extension,

adduction/abduction and

circumduction areallowed,but NO ROTATION

Similar to the Ellipsoidal

Joint, but the movements are

freer


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Ellipsoid and Pivot Joints

Ellipsoid joints Oval-shaped surface fits into

an oval-shaped cavity (ellipsemeans oval)

Biaxial joint: the movementsallowed areflexion/extension,adduction/abduction andcircumduction but NOROTATION

Pivot joints A rounded, pinted or conical

surface of one bone isinserted into a ring madepartly of another bone andpartly of a ligament

Uniaxial joint: the onlymovement allowed is therotation of one bone aroundits own axis

e.g: the neck and forearms in the neck the occipital bonespins over the top of the axis.In the forearms the radius andulna twist arround each other
http://www.shockfamily.net/skeleton/ARM.MOVhttp://www.shockfamily.net/skeleton/ARM.MOV

An Introduction to Human Biology (Joints)

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