Silelihaskoe

Silelihaskoe, in Finnish, refers to smooth muscle tissue, a type of involuntary non-striated muscle found in the walls of hollow organs and structures such as the gastrointestinal tract, blood vessels, airways, bladder, uterus, and parts of the reproductive and urinary systems. It is commonly studied in histology and pathology using tissue samples (silelihaskoe-biopsies or resections) to understand structure and disease.

Histology and structure stabilize the core concepts. Smooth muscle cells are spindle-shaped with a single central nucleus and lack the distinct cross-striations seen in skeletal muscle. The contractile apparatus consists of actin and myosin anchored to dense bodies and the cell membrane, with contraction regulated by calcium binding to calmodulin and activation of myosin light-chain kinase rather than the troponin-tropomyosin system. Two functional categories exist: unitary (single-unit or visceral) smooth muscle, which contracts as a coordinated syncytium via gap junctions, and multiunit smooth muscle, which contracts more independently and is found in certain ocular and vascular tissues.

Control and function rely on autonomic innervation and local factors. Smooth muscle is under autonomic nervous system influence, but it also responds to hormones, stretch, and mechanical cues. It can sustain long-lasting, tonic contractions and is capable of rapid shifts in tone, enabling processes such as peristalsis, vasomotion, and the regulation of sphincters.

Clinical relevance includes benign and malignant neoplasms such as leiomyoma (fibroids) and leiomyosarcoma, as well as disorders of motility and tone in the gastrointestinal, urinary, and vascular systems. In research and diagnostics, silelihaskoe samples are examined with light microscopy and immunohistochemistry (markers like smooth muscle actin and desmin) to confirm smooth muscle origin and assess pathology.