Sarcomere of skeletal muscle (mammalian): TEM and diagram. The sarcoplasmic reticulum extends over the A band and into the I band and forms a tubular network in the region of the H band. Longitudinal tubules give rise to terminal cisternae closely associated with the transversely oriented T tubule (arrows). The triads are located near the junction of the A and I bands. The part of the sarcoplasmic reticulum that connects with that of the succeeding sarcomere is incomplete in this plane of section. Portions of it are visible between paired I-band mitochondria (M), which are closely aligned with the triad. (diaphragm, rat)
Weiss, L. ed., Cell and Tissue Biology, 6th ed., Urban & Schwarzenberg, Baltimore, 1988, p. 267.
A gap junction (GJ) is present in the longitudinal portion of the disk. In the transverse portions, the actin filaments of the sarcomere insert into the filamentous web underlying the extensive fascia adherens junction. there are also occasional spot desmosomes (D) I, associated with intermediate filaments (desmin in muscle). Note the abundant glycogen (small particles) and the large mitochondria.
Weiss, L. ed., Cell and Tissue Biology, 6th ed., Urban & Schwarzenberg, Baltimore, 1988, p. 409.
Longitudinal section of portion of smooth muscle fiber showing part of centrally located nucleus (N). Mitochondria, Golgi and ribosomes are abundant in conical perinuclear region. The remainder of the fiber is occupied by thin filaments and dense bodies (arrows) into which the filaments appear to insert. There are no transverse striations. (ileum of 13 day-old rat)
Weiss, L. ed., Cell and Tissue Biology, 6th ed., Urban & Schwarzenberg, Baltimore, 1988, p. 275.
