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H-band is the zone of the thick filaments that has no actin. Within the H-zone is a thin M-line (from the German "mittel" meaning middle), appears in the middle of the sarcomere formed of cross-connecting elements of the cytoskeleton. Molecular model of the Sarcomere in the A-band. Organization of the central region of the A-band (C-zone).
The H zone becomes smaller and smaller due to the increasing overlap of actin and myosin filaments, and the muscle shortens. Thus when the muscle is fully contracted, the H zone is no longer visible. Note that the actin and myosin filaments themselves do not change length, but instead slide past each other.
Regional anatomy is the study of the interrelationships of all of the structures in a specific body region, such as the abdomen. In contrast, systemic anatomy is the study of the structures that make up a discrete body system—that is, a group of structures that work together to perform a unique body function, such as the digestive system. [11]
In histology (microscopic anatomy), the lobules of liver, or hepatic lobules, are small divisions of the liver defined at the microscopic scale. The hepatic lobule is a building block of the liver tissue, consisting of portal triads, hepatocytes arranged in linear cords between a capillary network, and a central vein.
The darker bands within skeletal muscle, known as anisotropic bands (A bands), encompass both thick and thin filaments and constitute the central region of the sarcomere, extending across the H-zone. Collectively, the A bands and the I bands create the distinctive striped appearance of skeletal muscle tissue. [ 3 ]
Watershed area is the medical term referring to regions of the body, [1] that receive dual blood supply from the most distal branches of two large arteries, such as the splenic flexure of the large intestine.
The epiphyseal plate, epiphysial plate, physis, or growth plate is a hyaline cartilage plate in the metaphysis at each end of a long bone.It is the part of a long bone where new bone growth takes place; that is, the whole bone is alive, with maintenance remodeling throughout its existing bone tissue, but the growth plate is the place where the long bone grows longer (adds length).
The primitive streak is a structure that forms in the early embryo in amniotes. [1] In amphibians, the equivalent structure is the blastopore. [2] During early embryonic development, the embryonic disc becomes oval shaped, and then pear-shaped with the broad end towards the anterior, and the narrower region projected to the posterior.