AN3.1-3 | General features of Muscle — Glossary

Striated voluntary muscle attached to bones; characterised by long cylindrical fibres with multiple peripheral nuclei and visible striations

Striated involuntary muscle of the heart wall; characterised by branched fibres with single central nuclei and intercalated discs

Non-striated involuntary muscle of hollow organs; characterised by spindle-shaped cells with single central nuclei

Dense irregular connective tissue wrapping the entire muscle; continuous with the deep fascia and merging into the tendon

Connective tissue surrounding fascicles (bundles of muscle fibres); carries blood vessels and nerves to reach individual fibres

Delicate reticular connective tissue surrounding each individual muscle fibre; contains capillaries and satellite cells

A bundle of muscle fibres surrounded by perimysium; the intermediate structural unit between the whole muscle and individual fibres

Cord-like structure of dense regular connective tissue (Type I collagen) transmitting the pulling force of muscle contraction to bone

Flat sheet-like expansion of dense regular connective tissue serving as a broad tendinous attachment distributing force across a wide area

Largest tendon in the body connecting the gastrocnemius and soleus to the calcaneus; avascular critical zone 2-6 cm above insertion is the site of rupture

A muscle whose line of pull passes mostly across the bone, producing large rotary force at the joint (e.g., brachialis at the elbow)

A muscle whose line of pull passes mostly along the bone, providing joint stabilisation against distraction forces (e.g., brachioradialis at the elbow)

Elevated intracompartmental pressure from muscle swelling within a tight fascial envelope, compromising blood supply; requires emergency fasciotomy

Emergency surgical incision through the fascia to relieve elevated compartment pressure and restore blood flow to muscles and nerves

Specialised junctions between cardiac muscle cells containing desmosomes and gap junctions for mechanical coupling and electrical synchronisation

The component of muscle force acting perpendicular to the bone, causing rotation at the joint

The component of muscle force acting along the bone, compressing the joint surfaces together and preventing distraction

Fibrosis and thickening of the palmar aponeurosis causing progressive flexion contracture of the fingers, particularly ring and little fingers

Midline fibrous raphe formed by the fusion of the aponeuroses of the three flat abdominal muscles; extends from the xiphoid to the pubic symphysis

Clinical test for Achilles tendon rupture: squeezing the calf should produce plantar flexion; absent plantar flexion indicates complete rupture

A single motor neuron and all the muscle fibres it innervates; the functional unit of muscle contraction