Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

Musculoskeletal System
Muscular System
Muscles and Fascia of the Limbs - Development and Age-Related Features of Skeletal Muscles

Human body Muscles develop from the middle germ layer (mesoderm), specifically its dorsolateral portion, which forms part of the body segments known as somites. These muscular primordia—myotomes—proliferate: their posterior (dorsal) sections give rise to the back muscles, while their anterior (ventral) sections form the Muscles of the chest and abdomen. The limb muscles develop from the anterior sections of certain trunk myotomes that grow into the limb buds. The HEAD muscles (mastoid, facial) and certain Neck Muscles develop from the Muscle primordia of the visceral and branchial arches.

Muscle fibers originate from mononuclear embryonic muscle Cells known as myoblasts. Myoblasts aggregate and fuse into multinucleated structures (fibers), within which myofibrils and cross-striations emerge.

By the time of birth, the muscles of the head, trunk, and upper limbs are the most developed. In a newborn, muscle mass accounts for approximately 20% of total body weight. Muscle tendons and fascia are poorly developed at birth.

After birth, muscles grow, gradually increasing in size and mass. Tendons elongate. Longitudinal muscle growth continues until the age of 23–25. The most intensive growth of muscle fibers and muscles as a whole occurs during childhood and adolescence. Driven by motor activity and Physical Exercise, muscle fibers thicken and overall muscle mass increases. The elasticity (extensibility) of muscle fibers improves, and the number of myofibrils within the fibers increases. In physically developed muscles, the density of Blood capillaries also rises.

Review and Self-Assessment Questions:

1. List the muscles associated with the Lower limb girdle (Pelvic Girdle). Where are these muscles located and what Functions do they perform?

2. Name the muscle groups of the thigh and leg. Which muscles comprise each group, and what functions do they perform?

3. Name the muscle groups of the FOOT. What functions do these muscles perform?

4. Name the canals and synovial sheaths present in the lower limb. Where are they located, and what is their practical significance?

5. Describe the Development and Age-related characteristics of skeletal muscles.



Last update: 10/08/2026

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