Gigantism

3. Dwarfism is growth disorder resulting in an abnormally short individual.?

3. Dwarfism is growth disorder resulting in an abnormally short individual. What are the two major types of dwarfism seen in humans? Describe the physiological basis of these two forms of dwarfism. Do individuals suffering from these two types of dwarfism have the same appearance? Explain.

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1. Categories of Dwarfism: Disproportionate - The individual has an average-sized torso with short arms and legs. It is usually caused by skeletal dysplasia or chondrodystrophy (the failure of cartilage to develop into bone). Proportionate - In this form, the body parts are proportionate, but abnormally short. The primary cause is a growth hormone deficiency or dysfunction with the pituitary gland. These disorders are now often treatable. Types of Dwarfism: There are over 200 types of dwarfism. A compilation of the types of dwarfism and dysplasia types can be found at Dwarfism.org ?Types of Dwarfism page. The most common types are described below. Achondroplasia: Achondroplasia is an autosomal dominant condition which means that there is a 50% chance of having children with achondroplasia. Eighty percent of all Little People have achondroplasia. Incidence ranges from 1 in 10,000 to 1 in 40,000. Characteristics include: Disproportionate, average trunk with short limbs and large head. Facial features include a large head with a prominent forehead. The midface is often small with a flat nasal bridge and narrow nasal passage. Waddling gait Bowed legs Reduction of elbow extension During infancy and childhood, middle ear infections are common due to the small nasal passages, and "ear tubes" may be required to treat multiple ear infections. Occasional airway obstruction or difficulty breathing until the airways grow Respiratory problems can occur in infants and children which may limit aerobic fitness. Average height is 4 ft. 0 inches. Diastrophic Dysplasia: Diastrophic dysplasia is an autosomal recessive condition, and parents have a 25% chance of having a child with it. This is the most disabling of the types. Incidence is 1 in 110,000 births. Characteristics include: Spinal deformity Cleft palate Clubfoot Ears have cauliflower appearance. Hand deformities Broad fingers Hip and knee dislocations Orthopedic problems are frequent and ambulatory assistance required. Usually caused by inefficient nourishment during prenatal bone growth and failure of nerve centers. Respiratory complications cause increased infant mortality, but individuals who survive infancy have a normal life span. The average height of adults is 118 cm (males: 86-127 cm; females 104-122 cm). http://www.twu.edu/inspire/Fact_Sheets/dwarf.htm http://en.wikipedia.org/wiki/Dwarfism http://www.udel.edu/chemo/teaching/CHEM465/SitesF02/Prop03b/dwarfism.html