L10b Synovial Joints

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1. Synovial joints

2. Learning objectives
•Examine four of our major synovial joints
of the body.
•Appreciate the structure of each of these
synovial joints, both diagrammatically and
physiologically.
•Learn about the directions of movement.
•Understand examples of sporting activities
where these joints are used.

3. Introduction

•Most joints are freely moveable.
•They allow different movement, depending on the shape
of the bones at the joint.
•The shoulder, hip and ankle are susceptible to injury due
to the amount of movement possible at them

4. Ball-and-socket joint
•Most moveable joint in
the body.
•One bone has a bulge
like a a ball at the end.
•This fits into a socket in
the other bone.
•It can turn in many
directions.
Examples
•The hip joint
•The shoulder joint

5. task
1.Why do you think it is difficult to dislocate
a ball-and socket joint?
2.In what joint do you think a cricket bowler
would be want to be very flexible?

6. The hinge joint
•This works like a hinge on
a door.
•The bone can swing
backwards and forward.
•The end of one bone is
shaped like a cotton reel.
•It fits into the hollow of the
other.
•The joint will open until it
is straight and no further.
Examples
•The elbow joint
•The knee joint

7. The pivot joint
•One bone has a bit that
juts out, like a peg or
ridge.
•This fits into a ring or
notch on the other bone.
•The joint only allows
rotation Examples
•The joint between the atlas and
axis.
•The joint between the radius
and ulna.

8. The gliding joint
•Here the end of the
bones are flat enough
to glide over.
•There is little
movement in all
directions.
•Of all synovial joints
this gives the least
movement.
Examples
•Joints between the carpals
(hand) and tarsals (foot).
•Joints between most of the
vertebrae.

9. Cartilage

•Cartilage stops bones knocking together.
•It is a gristly cushion between the bones at slightly
moveable joints.
•It forms a smooth slippery coat on the ends of bones at
synovial joints

10. Ligaments
•Ligaments are strong cords and straps that lash
bones together and hold joints in place.
•They are a bit elastic-enough to let the bones
move.

11. Tendons
•Tendons are the cords and straps that join
muscle to bone.
•The best known joins our calf muscle to our heel
and is called the Achilles tendon.

12. •Achilles, the Heel
•Achilles was the son of Thetis and Peleus, the bravest hero in the Trojan war,
according to Greek mythology.
•When Achilles was born, his mother, Thetis, tried to make him immortal by
dipping him in the river Styx. As she immersed him, she held him by one heel
and forgot to dip him a second time so the heel she held could get wet too.
Therefore, the place where she held him remained untouched by the magic water
of the Styx and that part stayed mortal or vulnerable.
•
To this day, any weak point is called an “Achilles’ heel”. We also refer to the
strong tendon that connects the muscles of the calf of the leg with the heel bone
as the “Achilles’ tendon”.
•Although the above rendition of the Achilles’ story is in current vogue, Michael
Macrone, in his It’s Greek to Me, tells us that Achilles didn’t always have a
vulnerable heel. Oh yes, he had a weak spot, but according to the original story
about Achilles, Homer, in the Iliad, said it was his pride. Later versions indicate
his weakness was his love for the Trojan princess Polyxena. In his
Metamorphoses, Ovid suggested that Achilles had a vulnerable spot on his body;
but the Roman poet, Statius (c. A.D. 45-96), was the first to imply in a poem that
it was his heel.

13. Joints and movement: a
summary
A little movement in all directions
(no bending or circular motions)
gliding
Only rotationPivot
Flexion and extensionHinge
Flexion and extension
Abduction and adduction
Ball-and-socket
MOVEMENT
ALLOWED
TYPE OF JOINT

14. Key revision points
•You need to know the four different
synovial joints (ball-and-socket, hinge,
pivot and gliding joint).
•Understand the differences of each and
the movements that occur at those joints.
•Again, understand the role of cartilage,
ligaments and tendons.