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A typical anther contains four microsporangia. The microsporangia form sacs or pockets (locules) in the anther (anther sacs or pollen sacs). The two separate locules on each side of an anther may fuse into a single locule. Each microsporangium is lined with a nutritive tissue layer called the tapetum and initially contains diploid pollen mother ...
This occurs during myogenesis with the fusion of myoblasts each contributing a nucleus to the newly formed muscle cell or myotube. [12] Fusion depends on muscle-specific proteins known as fusogens called myomaker and myomerger. [13] A striated muscle fiber contains myofibrils consisting of long protein chains of myofilaments.
Muscle cells are attached to the collagenous myo-tendon space via hemidesmosomes. The myo-tendon space is then attached to the base of the tendon cells via basal hemidesmosomes, while apical hemidesmosomes, which sit atop microvilli , attach the tendon cells to a thin layer of collagen .
A single muscle fiber can contain from hundreds to thousands of nuclei. [25] A muscle fiber for example in the human biceps with a length of 10 cm can have as many as 3,000 nuclei. [25] Unlike in a non-muscle cell where the nucleus is centrally positioned, the myonucleus is elongated and located close to the sarcolemma.
A classic example of a syncytium is the formation of skeletal muscle.Large skeletal muscle fibers form by the fusion of thousands of individual muscle cells. The multinucleated arrangement is important in pathologic states such as myopathy, where focal necrosis (death) of a portion of a skeletal muscle fiber does not result in necrosis of the adjacent sections of that same skeletal muscle ...
Smooth muscle is grouped into two types: single-unit smooth muscle, also known as visceral smooth muscle, and multiunit smooth muscle. Most smooth muscle is of the single-unit type, and is found in the walls of most internal organs (viscera); and lines blood vessels (except large elastic arteries), the urinary tract , and the digestive tract .
A main component in the cytoskeleton that helps show the true function of this muscle contraction is the microfilament. Microfilaments are composed of the most abundant cellular protein known as actin. [10] During contraction of a muscle, within each muscle cell, myosin molecular motors collectively exert forces on parallel actin filaments.
He called this protein myosin. [ 3 ] [ 4 ] The term has been extended to include a group of similar ATPases found in the cells of both striated muscle tissue and smooth muscle tissue . Following the discovery in 1973 of enzymes with myosin-like function in Acanthamoeba castellanii , a global range of divergent myosin genes have been discovered ...