Muscle, Connective Tissue, and Neonatal Disorders

Muscle, Connective Tissue, and Neonatal Disorders

DOI: 10.4018/978-1-5225-8066-9.ch017

Abstract

The skeleton provides the framework and anchor points against which muscles, attached via tendons, can exert force. Three types of cells are involved in making bone: osteoblasts, osteoclasts, and cartilage. The human muscle system is made up of three types of muscle tissue: skeletal, cardiac, and smooth. The neonate period of life is the first 4 weeks after the birth of an infant. This chapter presents 11 genetic disorders that affect muscles, connective tissue, and newborns. These include achondroplasia, Charcot-Marie tooth syndrome, Duchenne Muscular Dystrophy, Ellis-Van Creveld syndrome, amyotrophic lateral sclerosis, Marfan syndrome, fibrodysplasia ossificans progressive, myotonic dystrophy, Angelman syndrome, Prader-Willi syndrome, fragile-X syndrome, and Waardenburg syndrome.
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Chapter Outline

  • 17.1 Overview

  • 17.2 Achondroplasia

  • 17.3 Charcot-Marie-Tooth Syndrome

  • 17.4 Duchenne Muscular Dystrophy

  • 17.5 Ellis-Van Creveld Syndrome

  • 17.6 Amyotrophic Lateral Sclerosis

  • 17.7 Marfan Syndrome

  • 17.8 Fibrodysplasia Ossificans Progressiva

  • 17.9 Myotonic Dystrophy

  • 17.10 Angelman Syndrome and Prader-Willi Syndrome

  • 17.11 Fragile-X Syndrome

  • 17.12 Waardenburg Syndrome

  • Chapter Summary

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Learning Outcomes

  • Identify each genetic disorder affecting each system

  • Outline the symptoms of each disorder

  • Explain the genetic basis of each disorder

  • Summarize the current therapies available to treat each disorder

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17.1 Overview

Humans have endoskeletons which are rigid internal body parts made up of bone that receive the applied force of muscles. The skeleton provides the framework and anchor points against which muscles, attached via tendons, can exert force (Figure 1). It is made up of 206 bones divided into 2 systems: a) axial skeleton with skull bones, 12 pairs of ribs, the sternum, and the 26 vertebrae; b) appendicular skeleton which is made up of the pectoral girdles (shoulders); pelvic girdle (hips) and pairs of arms, hands, legs and feet. Bones are complex organs that function in movement, providing support by anchoring muscles, protecting internal organs, storage of minerals particularly calcium and phosphorous, and blood cell production (white blood cells, red blood cells and platelets). There are two types of bone tissue: compact bone which is found in the shaft and at both ends of long bones. Compact bone is made up many thin, cylindrical, dense layers around interconnected canals for blood vessels and nerves and it resists mechanical shock. Spongy bone tissue has abundant air spaces but very firm and is found inside both ends and shaft of bone. Spongy tissue contains red bone marrow where blood cells are formed. It also contains yellow bone marrow which is largely fat but can be converted to red marrow in severe blood loss cases.

Figure 1.

The structure and bones of the human skeleton

Source: Image used under license from Shutterstock.com

Three types of cells involved in making bone. 1) Osteoblasts: In the developing embryo cartilage models are first constructed, into which osteoblasts secrete organic substances which mineralize; cartilage then breaks down to form bone marrow cavities. Once osteoblasts are imprisoned by these secretions, they become osteocytes or mature living bone cells. In adults, large amounts of minerals and many osteocytes are removed and replaced routinely in a process called bone remodeling which adjusts bone strength and maintains calcium and phosphorous levels in the blood. 2) Osteoclasts secrete enzymes that digest bone in the routine bone remodeling activities in the body. 3) Cartilage are collagen fibres embedded in a rubbery matrix of protein and carbohydrate secreted by cells called chondrocytes. In the adult body cartilage is retained in the flexible parts of our skeleton (ears, nose, intervertebral discs, and windpipe). Physical exercise stresses bone such that the process of mineral deposition exceeds withdrawal—making the bones denser and stronger. With age, bones decline in mass where mineral deposits lag behind withdrawal making the bones hollow and brittle—a condition known as osteoporosis.

Key Terms in this Chapter

Kyphosis: An abnormally excessive outward curvature or forward rounding of the spine.

Bone Remodeling: A highly regulated cycle where osteoclasts destroy old bone so that osteoblasts make new bone.

Dysphagia: Difficulty swallowing.

Benzothiazepines: A subclass of calcium channel blocking drugs that can be used to reduce the force of cardiac contractions as well as a vasodilator.

Stoichiometry: Expression of the quantitative relationship between products and reactants in a chemical reaction.

Phenylalkylamines: A subclass of calcium channel blocking drugs that is used to target cells of the heart.

Pseudohypertrophy: Enlargement of calf muscles.

Lumbar Lordosis: Inward curvature of the lower back.

Macroorchidism: A condition affecting males that is characterized by abnormally large testes relative to age.

Prognathism: A facial deformity characterized by the protrusion of either the upper or lower jaw.

Microcephaly: A birth defect in which an infant’s head is smaller than other infants of the same age and sex.

Dyspnoea: Shortness of breath or difficulty breathing.

Dihydropyridines: A subclass of calcium channel blocking drugs that is often used to reduce peripheral resistance and arterial pressure.

Spinal Stenosis: The narrowing of the spinal canals.

Hirschsprung Disease: A birth defect in which nerve cells that line the intestine do not properly form during development causing the inability to pass stool.

Dolichocephaly: A condition characterized by an abnormally elongated head relative to head width.

Neurocristopathy: A group disorders involving abnormal neural crest cell differentiation and migration.

Multiple Myeloma: Cancer of the plasma cells.

Cardiomyopathy: A disease of the heart muscle in which the heart muscle can become thick, enlarged, or stiff.

Antisense Oligonucleotides: Short synthetic polymers that can bind to specific RNA molecules to alter protein expression.

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