The Skeletal and Muscular System

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Anatomy & Physiology –Skeletal, Articular and Muscular Systems

The Skeletal, Articular and Muscular Systems

Task 1

a.        Analyse the effects of hormones, diet and activity on bone growth.

Bone comprises various types of tissue including bone tissue, cartilage, dense connective tissue, epithelium, adipose tissue and nervous tissue.  Bone is continuously growing, remodelling and repairing itself.  The process of formation of bone is called as ossification which occurs under the following four conditions:

a.        Initial formation of bones in an embryo or foetus.  In an embryo or foetus there are two types of ossification, intramembranous ossification and endochondral ossification.  Intramembranous ossification is the formation of the flat bones of the skull and mandible or lower jawbone.  Endochondral ossification involves replacement of cartilage by bone and most bones in the body are formed in this way.

b.        Growth of bones during infancy, childhood and adolescence until adult bone sizes are reached.  Long bones grow in length and bones throughout the body grow in thickness during infancy, childhood and adolescence.

c.        The remodelling of bones is the replacement of old bone tissue by new bone tissue throughout life of the individual.  It involves bone resorption, which is the removal of minerals and collagen fibres from the bone, and bone deposition, which is the addition of minerals and collagen fibres to the bone.

d.        Repairs of fractures or breaks in bones throughout life.  The repair of fractures or breaks sometimes can take months.  This is due to the bone slow and gradual deposition of calcium and phosphate needed to strengthen and harden the new bone, and bones cells generally grow and reproduce slowly.

There are a number of factors that affect the development, growth and repair of bones.  The following three factors will be discussed below:

a.        Hormones.  

b.        Diet.

c.        Activity.

Hormones secreted by various glands in the body such as the pituitary gland, thyroid gland and parathyroid glands affect the growth and development of bones.  For example, the pituitary gland secrets growth hormone, which stimulates division of cartilage cells during ossification.  Some of the bone conditions caused due to hormonal imbalance in the body are as follows:

a.        Dwarfism.  A condition caused by low levels of growth hormone during childhood causing the body to under-develop.  This leads to an individual who is short height with limbs that are in proportion to the rest of the body.

b.        Gigantism.  A condition caused by abnormally high levels of growth hormone during childhood before the bone growth plate has closed.  This causes the child to grow abnormally tall.

c.        Acromegaly.  A condition caused by an excess in production of growth hormone after the bone growth plate has closed.  It causes abnormal enlargement of bones and tissues, most commonly in the limbs, it occurs gradually over numerous years.

d.        Cretinism is the stunted body growth and mental development appearing in the first years of life resulting the inappropriate development of the thymus gland or inadequate maternal intake of iodine during pregnancy, which affects the production of Thyroxine.

Diet or nutrition are very important for the formation and maintenance of healthy bones.  Foods rich in minerals such as calcium and phosphorous, which are the main components of the bone, are essential for bones to be strong.  For instance, such as rickets in children.  The following are bone conditions that are caused by poor diet:

a.        Rickets.  It is a condition that affects children in which the bones are softer and weaker due to lack of calcium and vitamin D, which is necessary for the absorption of calcium in the small intestine and in its absence calcium is poorly absorbed in the body.  This causes the bone to lack in calcium, can causes the bone to soften and thereby cause rickets.

b.        Osteoporosis. It is a condition affecting mostly older people in which the bones become less dense that makes them weak and more prone to breaks and fractures.  Healthy diet rich calcium and vitamin D is beneficial to prevent osteoporosis.

c.        Osteoarthritis.  A condition which causes pain and stiffness in joints.  Food supplements such as glucosamine, chondroitin, avocado and soyabean is beneficial in some cases.

Activity is essential for maintaining healthy bones.  A lack of physical activity can cause the bones to lose density and become weak and prone to fractures.  Exercise helps stimulate bone formation cells and strengthen the bones.  In addition it also gives strength to the muscles supporting the bones.  Regular weight-bearing exercises are particularly good for increasing bone density.

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b.        Explain how bones are joined together to form a framework and list any common distortions.

Bones are connected together by flexible connective tissues called ligaments.  Ligaments are tough, elastic bands of connective tissue connecting bones or cartilage at a joint or they hold organs in position.  They are made of dense fibrous tissue formed by parallel bundles of collagen fibres, which give strength and stability to the joint.  Stability is provided by controlling the range of motion of a joint, for example the ligaments prevent the elbow from bending backwards.  Cartilage is a tough, elastic connective tissue which ...

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