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At the completion of this chapter, the reader will be able to:


  1. Discuss the various periods of normal prenatal development

  2. Describe the normal sequence in which nervous tissue, connective tissue, and skeletal muscle develop

  3. Describe how the motor unit works

  4. List the different kinds of feedback receptors

  5. Describe the various physiologic processes by which the body produces energy

  6. Discuss the external and internal forces of the body that are either generated or resisted during the course of daily activities

  7. Describe the various types of levers and give real-life examples of each

  8. Describe the various components of the stresses and strains that occur with connective tissues

  9. List the various planes and axes of the body

  10. Explain the concept of degrees of freedom and give examples of each

  11. Explain the difference between osteokinematic motion and arthrokinematic motion

  12. Discuss the difference between open and closed kinetic chains

  13. Describe the various theories of motor development, motor control, and motor learning

  14. List the different kinds of motor tasks and describe the differences

  15. Describe how early motion develops in terms of stability and mobility

  16. Discuss the various methods of skill acquisition

  17. Describe the factors that affect normal development and the impact that physical therapy can have




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 number of decisions about the overall clinical program of a patient (see Chapter 7).




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).



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


From a clinical perspective, the course of pregnancy is divided into three-month intervals called trimesters:


  • First trimester (first 12 weeks)

  • Second trimester (weeks 13 to 24)

  • Third trimester (week 25 to birth)


From a biological perspective, human development occurs in three main stages. The first two weeks (approximately 16 days) after conception are known as the pre-embryonic period; day 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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