The Heart:The Pulmonary Circulation

Each skeletal go through fiber is a single cylindrical cell; its tissue layer is c solelyed the sarcolemma, and its cytoplasm is the sarcoplasm. It contains specialized smooth endoplasmic reticulum. There are eightfold nuclei at the periphery of the cell, and the cells contain many mitochondria. Microscopically, the cells have vary light (I) and dark (A) bands which are seen as striations. The sarcoplasm contains thick myofilaments of myosin and slew myofilaments of actin. A Z line bisects the I band, and serves as a point of attachment for actin filaments. The functional unit of skeletal musculus is the sarcomere, which extends from one Z line to the next. When a muscle contracts, all the sarcomeres in all the myofibrils shorten at the same time.

30.15 The alone(p) structure of cardiac muscle cells allows action potentials to travel quickly from one cell to another, and allows the cardiac muscle to contract as a whole unit. The unique structure in cardiac muscle is the gap junction. Gap junctions are intercellular channels, which reserve free passage of ions and small molecules up to a molecular(a) weight of about 1000 Daltons amidst cells (Junctions, 2004). They are constructed from between four and six copies of a group of membrane proteins suitably known as connexins.

Gap junctions allow changes in membrane potential to flow from cell to cell rapidly.

31.2 For the heart to spirit productively, the contractions of the atria and the ventri

Middle cerebral artery. (2004). Retrieved at:

32.21 The two fetal bypass structures that normally become obliterate after birth are the foramen ovale and the ductus arteriosus (Applegate, 2000, 281-282).

32.11 a) inferior nervure cava-right atrium-tricuspid-valve-right ventricle-pulmonary trunk-l/r pulmonary artery-l/r pulmonary vein-pulmonary capillary-alveolus (Applegate, 2000, 269)

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