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Muscles Beginning With I
9 muscles in the reference begin with the letter I. Every name links to a page giving the muscle’s origin, insertion, main actions and nerve supply.
A B C D E F G H I L M N O P Q R S T V Z
| Muscle | Main actions | Nerve supply |
|---|---|---|
| Iliacus | Flexes the thigh at the hip (principal hip flexor, with psoas major) | Femoral nerve (L2–L4) |
| Iliocostalis Lumborum | Extends the lumbar spine; Tilts the trunk to the same side | Dorsal rami of lumbar spinal nerves |
| Iliopsoas (Group) | Flex the thigh at the hip — the strongest hip flexor; Flexes the trunk when rising from lying | Ventral rami L1–L3 (psoas) and femoral nerve (iliacus) |
| Infraspinatus | Rotates the arm outward (lateral rotation); Stabilises the shoulder joint | Suprascapular nerve (C5–C6) |
| Internal Intercostal Muscles | Depress the ribs during forced breathing out | Intercostal nerves |
| Internal Oblique | Rotates the trunk to the same side; Flexes and side-bends the trunk | Lower intercostal nerves and iliohypogastric/ilioinguinal nerves (L1) |
| Interossei and Lumbricals (Intrinsic Group) | Fine control of finger posture — bend at the knuckle, straighten beyond it | Mainly ulnar nerve deep branch; lateral lumbricals median (C8–T1) |
| Interspinales | Extend the spine slightly; Stabilise neighbouring vertebrae | Dorsal rami of spinal nerves |
| Intertransversarii | Tilt the spine to the same side; Stabilise neighbouring vertebrae | Ventral and dorsal rami of spinal nerves |
Please note: This page is an anatomy education summary for students and curious readers, not medical advice. Attachment points are given in their classic short form; individual anatomy varies, and detailed dissection-level descriptions belong in an anatomy atlas.