Activity 9.6 ture and Function Synovial Joints: Examining the Struc of Pivot and

Question

Activity 9.6 ture and Function Synovial Joints: Examining the Struc of Pivot and Ellipsoid Joints As perot joints, rounded surface of one bone nts into a of another bone. On a skeleton, identily the proximal and distal radiounar joints. Observe the articulations for these joints At the proximal joint, the head of the radius articulates with the radial notch on the ulna Al the distal joint, the head of the una articulates with the h ulnar notch on the radius Rad At the radiounar joints, the rotational movements are pronation and supination of the forearm, Perform these actions on the right forearm, Notice that movement occurs at the two radioulnar joints, and as a result, the entire radius rotates around the una. The actions of pivot joints are restricted to rotational movements around a central axis. They are classified as uniasial joints.Explain why. Dens Anterior arch On a skeleton, identify the atlantoaxial joint. This joint is an articulation between the first two cervical vertebrae, the atlas (CJ and the axis (Cal. Notice how the dens of the axis articulates with a shallow depression on the anterior arch of the atlas. The atlantoaxial joint is another example of a pivot joint. Explain why 140 EXERCISE9 Arsulartions

Explanation / Answer

Ans 3)

A pivot joint is an uniaxial joint as it allows movemnet over one axis only. The bone rotates within a ring. Since the rotation occurs around a single axis, hence a n uniaxial joint.

Ans 4)

The pivot in the atlanto axial joint is formed between the ring by anterior arch and the transverse ligament of atlas and the depression by the odontoid process of the axis. The complex structure formed by four bones allows the up and down movement of the head as donee while nodding "yes" or side way movements as done while nodding "no". Thus as the axis remains single one, it is a type of pivot joint which are uniaxial.

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