In the following diagram, the structure marked with arrow has all of the following cell junctions except?
(A) Zona occludens (B) Zona adherens (C) Macula adherens (D) Gap junction
(A) The image given is cardiac muscle, as it is showing Intercalated discs which is typical for cardiac muscle & Perinuclear halo is seen. It is striated muscle (not as striated as skeletal muscle) Usually in a cell, the following cell junctions are seen in a sequence Surface of cell Tight junctions (most superficial) - Absent in cardiac muscle Zona adherens (20nm) Desmosomes/Macula adherens (25mm) - holds 2 cells together Gap Junctions - imp in cardiac muscle Gap Junctions are narrow gaps usually working as electrical synapses, they let pass ca+2 ions & maintain quick transfer of cardiac impulses & maintain rhythmic contractions If gap junctions are compromised, Problem occurs in electrical synapses which leads to arrhythmia. Tight junctions (Zona occludens) are absents in cardiac muscle. Hemi-desmosomes attach cell to basement membrane. Given structure is not skeletal muscle because skeletal muscle is more striated & there is no peri-nuclear halo in it. It is not smooth muscle because smooth muscle is spindle shaped and is not striated.