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Cell division and the Musсulоskеlеtаl System

Mitosis and Meiosis

Generally, cells divide in two ways; the first way is mitosis, the second way is meiosis. Mitosis is a cell division process whereby an individual cell undergoes cell division which results to two daughter cells. Meiosis is basically a process whereby single cells undergoes cell division, the cells divide twice and produces four cells, whereby each of the cells has half the amount of genetic composition (Nasmyth 2001). Mitosis and meiosis exhibits major differences as follows; for mitosis, two daughter cells formed are usually similar to the original cell while for meiosis, the chromosomes which are homologous normally separate leading to cells which are completely unidentical to the original cell. For mitosis, individual cell usually divides once but for meiosis; the cell undergoes two phase for the cell to completely divide-first and second meiotic divisions. Mitosis occurs mainly in body cells known as somatic cells while meiosis usually occurs mainly on cells referred to as germ cells.

Mitosis takes place in all reproducing organisms while for meiosis; it takes place on organisms that reproduce sexually. Additionally, for mitosis, during the last phase of the cell division the chromosome number remains constant while in meiosis there is a haploid chromosomal number. Mitosis lacks synapsis but for meiosis; there is synapsis in the homologous chromosomes. During mitosis, chromosomes that are similar tend to move to the opposite poles while during meiosis, there is movement of chromosomes that are not similar and hence the chromosomes move to the opposite pole of the cell. Despite the major differences between mitosis and meiosis, both cell divisions are of significance in growth and reproduction.

Importance of Mitosis and Meiosis

Mitosis is important in sexual reproduction as the process allows the development of a cell to a grown individual. Additionally, mitosis sustains meiosis in that, the cells that form gametes undergo mitosis before meiosis in order to replicate. Mitosis also helps in repairing and healing of cells. Meiosis enable in the production of gametes that are used in fertilization. However, cells undergo a cycle called a cell division cycle that leads to replication of the DNA (Nasmyth 2001).

The Cell Cycle

There are four phases involved in the cell cycle. The cell cycle starts at resting state known as G0. In this phase, the cell has stopped dividing and has already left the cycle. In G1 phase, the cell starts increasing in size and the G1 control mechanism ensures that the cell contents are ready for DNA synthesis to take place. The next state is the interphase. Interphase state consists of two phases namely: synthesis(S) and Gap (G2). In the synthesis phase, there is occurrence of DNA replication (Israels & Israels, 2000). In the G2 phase, as the cell grows continually, there is a mechanism found in this phase that facilitates and ensures the individual cell is capable of dividing. Then the cell goes into the cell division state. This is the phase of mitosis. At this phase, the cell focuses on dividing into two cells which are the daughter cells. During mitosis, there is a mechanism which facilitates the completion of the cell division. After the cycle is completed, the daughter cell therefore begins a new cycle which starts with the interphase.

Cell Multiplication

Cell multiplication is a part of cell cycle whereby mitosis allows cells to produce copies hence replacing the cells. For instance in cases of damaged tissue, the cells usually multiply to repair the damaged tissue. As the wound heals, it undergoes several phases: inflammatory phase, maturation phase and proliferation phase. In the inflammatory phase, the body naturally responds to the injury whereby a clot forms through a process known as homeostasis. The vessels then allow enzymes, growth factors and white blood cells to reach the wound. Later, during proliferation, the wound is usually repaired with the help of a new granulation tissue (Marieb, 2007). The healthy granulation tissue is dependent on nutrients which are supplied by blood vessels.

Cell Maturation

This phase involves the remodeling of collagen. It is the final phase that occurs when a wound completely closes. In this phase, the number of blood vessels in the wounded area declines as the wound no longer needs much nutrients to heal (Marieb, 2007).

Cell Differentiation and Cell Reorganization

Cell differentiation also known as embryonic differentiation is the process of development whereby the cells undergo specialization creating diverse tissue structures. This differentiation is essential in tissue and organ identity. When fertilization occurs, a zygote is formed that divides into cells that facilitate embryonic differentiation. The cells then undergo reorganization which enables to define the consequent organism. The differentiation of cells is facilitated by both internal cellular factors and extracellular factors (Marieb, 2007).

Factors Affecting Growth and Reproduction

Nutrients are used by the body to enhance the growth, maintenance and repairing of cells. Proper nutrition facilitates the growth of cells. A child needs proper nutrition and if malnourished, the child’s growth may retard. However, growth is dependent on genetics partially. An individual’s height may be determined by the height of the parents but lack of proper nutrition may inhibit this growth. Diseases also affect growth. When body systems are not functioning properly, the cells are affected which affects growth. On the other hand, reproduction may be affected by an individual’s weight. Excessive weight reduces fertility in both men and women. In women excess oestrogen disrupts the menstrual cycle and insufficient oestrogen also reduces fertility. This can be associated by underweight (Clarke, 2008).Some medications may also interrupt hormones that are responsible for reproduction.

The Structure and Roles of the Skeleton

The structure of the bone consists of various types of cells. Osteoblasts help in building up the bones, and osteocytes allow longitudinal growth. The structure of the skeleton is suited to perform different roles as follows; support- Many bones especially the long bones provide support for the body. The support of the bones allows the development of larger organisms with larger organ capacities. Protection-The skeleton protects the internal organs of the body. For instance, the skull protects the brain. The protection and encased body organs are able to develop grow in size as well as perform in accordance to their functions. Further, the skeleton combines with muscular system hence allowing movement of the body. Additionally, the skeletal muscles and tendons are attached together and the tendons act like lever to facilitate the movement of bones. The muscles pull the bones to facilitate movement. Further, the bone tissues store minerals such as calcium and the yellow bone marrow contain fats that reserve energy for the body. The inner part of the bone consists of red marrow, a tissue that helps in the formation blood cells and platelets. The platelets help in the healing of wounds in cases of injury (Nordin & Frankel, 2001).

Structure of Skeletal Muscle and its Functions

The skeletal muscle is mainly composed of skeletal muscle tissue, the connective tissue which comprises of epimysium, perimysium and endomysium, the nerves and blood vessels. The entire muscle is wrapped in collagen whose ends have tendons (Nordin & Frankel, 2001).The tendons help the muscle to attach to the bone. Additionally, the connective tissue allows the transmission of force generated by cells to the bones. Muscle cells are normally elongated to form a muscle fiber. These fibers tend to be large and are multinucleated. The muscle fiber contains proteins known as the myofibrils which are divided into segments called sarcomeres. The sarcomeres are the contractory units of the muscle. At the end of the sarcomere, there is the Z disc. The myofibrils contain protein filaments known as myofilaments.

There are two types of myofilaments namely; actin and myosin .When the myofibril shortens the muscle contracts. Further, the myosin head binds to the sites that are active hence forming cross bridges. The cross bridges are then attached to the rod portion that bends and at at some point straightens during contractions. They also contain ATP that release energy and part of this energy is used during contraction. The sarcoplasmic reticulum surrounds each myofibril and stores Ca++ when the muscle is not contracting. The structure of the skeletal muscles allows the tissue to enhance movement, maintains body posture through tension in the skeletal muscle, supports and shields internal organs, maintains body temperature through the heat released by working muscles, guards the openings of digestive and urinary tracts and store nutrients.

Sliding Filament Theory

The sliding filament theory gives an explanation of how muscles undergo contraction so as to produce force. The contraction of muscles is a process that starts in the nervous system. An impulse facilitates the release of a chemical known as Acetylcholine. This chemical causes depolarization which later leads to the release of the Ca++ in the sarcoplasmic reticulum. When the Ca++, binds with protein troponin, it creates an avenue for myosin to bind with actin hence cross bridges are created. The formed cross bridges tend to pull the thin filaments which cause shortening of sarcomere. The created cross bridge later releases actin, and there is use of ATP in each cycle. The cycling of the cross bridges continues with the presence of the Ca++ and allows the filaments to slide with respect to each other. Finally, when the Ca++ gets back to the sarcoplasmic reticulum, then the contractions stop (Nordin & Frankel, 2001).

How Skeletal Muscles Enhance Movement.

Movement occurs when the muscles pull on the bone. The bones are usually connected to muscles via tendons and when the muscles contracts or relaxes, the tendon pulls the bone. When a signal of movement is sent, ATP is released which contracts the skeletal muscle, when it shortens, it pulls the corresponding bone at the insertion point and the distance between articulating bones reduces (Anandacoomarasamy et al., 2008). During relaxation, the muscles extend the movable bone back to its position. The agonist muscles shorten when contraction occurs to produce movement while the antagonist muscles returns the limb to its initial position. The synergist muscles similarly act on movable joints. Therefore, the cell division and musculoskeletal system are essential for body development.


Anandacoomarasamy, A., Caterson, I., Sambrook, P., Fransen, M. and March, L., 2008. The impact of obesity on the musculoskeletal system. International journal of obesity32(2), pp.211-222.

Clarke, B., 2008. Normal bone anatomy and physiology. Clinical journal of the American Society of Nephrology3(Supplement 3), pp.S131-S139.

Israels, E.D. and Israels, L.G., 2000. The cell cycle. The oncologist5(6), pp.510-513.

Marieb, E.N. and Hoehn, K., 2007. Human anatomy & physiology. Pearson Education.

Nasmyth, K., 2001. Disseminating the genome: joining, resolving, and separating sister chromatids during mitosis and meiosis. Annual review of genetics35(1), pp.673-745.

Nordin, M. and Frankel, V.H. eds., 2001. Basic biomechanics of the musculoskeletal system. Lippincott Williams & Wilkins.