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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 ...
An anther and its filament together form a typical (or filantherous) stamen, part of the male floral organ. The typical anther is bilocular, i.e. it consists of two thecae. Each theca contains two microsporangia, also known as pollen sacs. The microsporangia produce the microspores, which for seed plants are known as pollen grains.
Molluscan tendon cells appear columnar and contain a large basal cell nucleus. The cytoplasm is filled with granular endoplasmic reticulum and sparse golgi . Dense bundles of microfilaments run the length of the cell connecting the basal to the apical hemidesmosomes.
Muscle cells develop from embryonic precursor cells called myoblasts. [1] Skeletal muscle cells form by fusion of myoblasts to produce multinucleated cells in a process known as myogenesis. [4] [5] Skeletal muscle cells and cardiac muscle cells both contain myofibrils and sarcomeres and form a striated muscle tissue. [6]
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 .
An impulse from a nerve cell causes calcium release and brings about a single, short muscle contraction called a muscle twitch. If there is a problem at the neuromuscular junction, a very prolonged contraction may occur, such as the muscle contractions that result from tetanus. Also, a loss of function at the junction can produce paralysis. [5]
The cardiac muscle cells, (also called cardiomyocytes or myocardiocytes), predominantly contain only one nucleus, although populations with two to four nuclei do exist. [ 16 ] [ 17 ] [ page needed ] The myocardium is the muscle tissue of the heart and forms a thick middle layer between the outer epicardium layer and the inner endocardium layer.