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Infraspinatus
The infraspinatusLateral rotator Infraspinatus Lateral rotator Back of shoulder blade; rotates arm outward. is one of the four rotator cuff muscles (along with supraspinatusAbductor Top of shoulder blade; starts arm lift away from body., teres minorLateral rotator Small muscle below infraspinatus; rotates arm outward., and subscapularisMedial rotator Front of shoulder blade; rotates arm inward.). Its job involves motion. It also provides security. It keeps the humeral headRounded proximal end that fits into the acetabulum of the hip bone. snug in the glenoid cavity. This is similar to a golf ball stabilized on a tee.
Photography, text, and labels by Rob Swatski, Assistant Professor of Biology, Harrisburg Area Community College – York Campus, York, PA.
Origin
The infraspinatus muscle originates from the infraspinous fossaLarger depression below the spine on posterior surface., a concave depression on the scapula’s posterior surface. It specifically arises from the medialToward the midline of the body two-thirds of the infraspinous fossa.
Insertion
The infraspinatus muscle inserts onto the greater tubercleLarge bump lateral to the head; muscle attachment site. of the humerusLong bone of the upper arm; articulates with scapula at shoulder and radius/ulna at elbow.. This is a bony prominence on the lateralAway from the midline of the body. side of the humerus. The tendon of the infraspinatus muscle inserts into the posterior aspect of the greater tubercle. It provides stability and control over the shoulder joint.
Actions
Shoulder External Rotation
Stabilization of the Shoulder Joint
Assistance in Shoulder Extension
Interactive Materials
Use this 3D Viewer to Explore the Muscles of the Upper Body
“Open3DModel – Upper limb – English labels” by Open3D project, Jan Kooloos, RadboudUMC, Eungyeol Lee, LUMC et al, license: CC BY-SA
Identify More Muscles
Link to more Muscle Identification
Upper Arm Muscles
Forearm Muscles
Calf Muscles
Anterior Thigh Muscles
Posterior Thigh Muscles
Knee Structures
Chest Muscles
Back Muscles
Abdominal Muscles
Neck Muscles
Head Muscles
List of terms
- infraspinatus
- supraspinatus
- teres minor
- subscapularis
- head
- infraspinous fossa
- medial
- greater tubercle
- humerus
- lateral