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CHAPTER OBJECTIVES
At the completion of this chapter, the reader will be able to:
Discuss the various periods of normal prenatal development
Describe the normal sequence in which nervous tissue, connective tissue, and skeletal muscle develop
Describe how the motor unit works
List the different kinds of feedback receptors
Describe the various physiologic processes by which the body produces energy
Discuss the external and internal forces of the body that are either generated or resisted during daily activities
Describe the various types of levers and give real-life examples of each
Describe the various components of the stresses and strains that occur with connective tissues
List the various planes and axes of the body
Explain the concept of degrees of freedom and give examples of each
Explain the difference between osteokinematic motion and arthrokinematic motion
Discuss the difference between open and closed kinetic chains
Describe the various theories of motor development, motor control, and motor learning
List the different kinds of motor tasks and describe the differences
Describe how early motion develops in terms of stability and mobility
Discuss the various methods of skill acquisition
Describe the factors that affect normal development and the impact that physical therapy can have
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Normal movement, which is an amalgamation of strength, endurance, speed, and accuracy, is essential to normal functioning. In turn, normal functioning is dependent on normal development. A physical therapist can be viewed as an expert on movement, both normal and abnormal, through an acquired knowledge of neuromusculoskeletal development. This working knowledge is applied to make a variety of decisions about the overall clinical program of a patient (see Chapter 7).
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Human development is a continuum, starting with fertilization, prenatal development, birth, and ending with growth up to adulthood. Embryology is the study of prenatal development. Prenatal development, or fetal development, is the term given to the process of gestation (pregnancy) that an embryo undergoes. Human gestation lasts an average of 266 days (38 weeks) from conception (fertilization) to parturition (childbirth).
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CLINICAL PEARL
Because the date of conception is seldom known with certainty, the gestational calendar is usually measured from the day a woman’s last menstrual period began, and birth is predicted to occur about 280 days (40 weeks) thereafter.1
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From a clinical perspective, the course of pregnancy is divided into 3-month intervals called trimesters:
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First trimester (first 12 weeks)
Second trimester (weeks 13 to 24)
Third trimester (week 25 to birth)
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From a biological perspective, human development occurs in three main stages. The first 2 weeks (approximately 16 days) after conception are known as the pre-embryonic period; days 17 through the eighth week are known as the embryonic period, and the time from the beginning of the ninth week until birth is known as the fetal period.
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