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Week 4 (Scientist and Scholar Theme (Meiosis (Results in the formation of…

- - - - Skeletal muscle
        
        Skeletal muscle on the other hand are also striated, however it is multinucleated. This means that it contains many nuclei within the one cell, and these nuclei are located peripherally to ensure maximum contractibility. The skeletal muscle cells are also located parallel to one another. This muscle type is voluntary.
        
        Hierarchy of skeletal muscle: The muscle, fascicle, myofibre, myofibril, sarcomere is in between, and myofilament.
        
        The muscle is encapsulated in the epimysium, the fascicle is encapsulated in the perimysium, and the myofibre is encased in the endomysium.
        
        The myofibre is a collection of many myofibrils and these within them contain the sarcomeres, which contain the myofilaments. The myofilaments are the thick fibres of the muscle as opposed to the thin actin molecules.
        
        Skeletal muscle also contains A-bands and I-bands. These refer to the thick and thin striations of a muscle cell respectively. These are determined by how much light passes through the muscle. The A-bands are present where there are thick filaments, and I-bands where there are thin filaments only. The M line marks the middle of the sarcomere, the H line is where there are only thick filaments present at all, and the Z lines mark the ends of the sarcomere (there is one Z line present on each end of the sarcomere).
        
        T-tubules are channels that run from the surface of the muscle and into the fascicles. They conduct nerve impulses deep into the cell and allow for the muscle to contract as a whole.
        
        Elastic filaments contain titin and run from the Z line to M line and hold thick filaments in place. It also assists in the muscle cell to spring back into shape after being stretched.
      - Smooth muscle
        
        Smooth muscle cells are another type of involuntary muscle that contain centrally-located nuclei. These cells are spindle-shaped and are not striated. They are arranged in sheets and held together by dense bodies which are homologous to the Z lines in striated muscle. The method of contraction for these cells is very slow and weak.
      - Cardiac muscle
        
        Cardiac muscle is striated, it contains intercalated discs which also contain gap junctions which ensure the transfer of molecules across the cells, and desmosomes as well which mean that the cardiac muscle cells can contract as one. Cardiac muscle can also be highly branched in its nature, and contains a centrally located nucleus, similar to smooth muscle. This muscle type involves involuntary contractions.
        
        The zone around the intercalated disc is called the zonula adherens, the desmosomes are referred to as macula adherens.
      - There are myofibres, myofibrils, and myofilaments present in muscle. The myofilaments are the smallest and are the contractile proteins in the muscle. There are thick bundles of myosin present in the sarcomeres. Myofibrils are made up of many myofilaments and myofibres, which are encapsulated by the endomysium, are a combination of many myofibrils.
      - Sarcolemma: Muscle cell membrane. Sarcoplasm: The cytoplasm of a muscle cell. Sarcoplasmic reticulum: The smooth endoplasmic reticulum of muscle. Sarcomere: Contractile unit composed of myofilaments.
- - - - Most abortions that were carried out on medical grounds were carried out due to chromosomal abnormalities.
      - Usually women are happy with their abortion and the methods are either having a surgical or medical abortion.