16.2 Review of Anatomy & Physiology

This chapter discusses a wide range of common pediatric disorders that affect many body systems, including gastrointestinal, integumentary, neurological, cardiovascular, and musculoskeletal, as well as the eyes and ears. A review of the anatomy and physiology of these body systems, as well as pediatric life span considerations, are discussed in the following subsections.

Gastrointestinal System

Table 16.2a provides an overview of the major components of the gastrointestinal system and their associated functions, and these components are illustrated in Figure 16.1.^[1]

Table 16.2a. Components and Functions of the Gastrointestinal System^[2]

Pediatric Differences

Although the gastrointestinal systems of adults and children have the same components and functions, there are some pediatric differences that must be considered^[4],[5],[6]:

• The exocrine functions of the pancreas are not mature until one year of age.
• Infants have quicker gastric emptying times when compared to adults.
• The small intestine is shorter in children than adults, providing less surface area for absorption of nutrients.
• The production of gastric acid is decreased at birth when compared to adults.
• Children do not gain control of bowel movements until around two years of age.

Integumentary System

Table 16.2b provides an overview of the major components of the integumentary system and their associated functions, and Figure 16.2^[7] illustrates the anatomy of the skin.

Table 16.2b. Components of the Integumentary System^[8]

Pediatric Differences

Adults and children have the same integumentary system components, but there are some pediatric differences that must be considered^{[10],[11],[12]}:

• Sebaceous glands are present in pediatric clients, but do not become active until puberty.
• Infants have thinner and more fragile skin when compared to adults.
• The skin of infants is more permeable to water when compared to adults.
• The skin of children is more susceptible to damage from ultraviolet rays.

Neurological System

The neurological system is a complex system that is divided into two main areas called the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and spinal cord. The peripheral nervous system is made up of nerves and ganglia. Ganglia are large clusters of nerve cells. See Figure 16.3^[13] for an illustration of the central and peripheral nervous systems.

There are three basic functions of the nervous system, including sensation, response, and integration. Sensation involves the receival of information from the world around us. Response is when the nervous system acts based on the information it has received, including voluntary or involuntary responses. Integration refers to the processing of sensory information via the nervous system.^[14]

Pediatric Differences

Although the neurological systems of adults and children have the same components and functions, there are pediatric differences that must be considered^[16],[17]:

• Newborns and infants have underdeveloped temperature regulation that can result in hypothermia if their heads are left exposed.
• Children have increased fall risk due to incomplete motor development.
• Children are more susceptible to head injuries due to their larger head in relationship to their body size.
• The cranial bones of pediatric clients are thin and leave brain tissue less protected, resulting in hemorrhages, head trauma, and diffuse brain injury as a result of accidents or injuries.
• The brain of infant clients develops rapidly, requiring an adequate supply of oxygen and glucose.

Cardiovascular System

Review Table 16.2c for an overview of the major components of the cardiovascular system and their associated functions. See Figure 16.4^[18] for an illustration of the heart.

Table 16.2c. Overview of the Anatomy and Physiology of the Cardiovascular System^[19]

Pediatric Differences

Although the cardiovascular systems of adults and children have the same components and functions, there are some pediatric differences that must be considered^{[20],[21],[22]}:

• Many profound changes occur in a newborn’s cardiovascular anatomy and physiology over the first few days and weeks following birth.
• Newborns have incomplete sympathetic innervation of the heart, predisposing them to bradycardia.
• A small volume of blood loss in small children can be significant. For example, 100 mL of blood loss in an infant weighing 5 kg is 10% of their total blood volume.
• Establishing IV access in infants and children can be challenging due to their small veins and increased subcutaneous tissue.
• Children have a higher metabolic rate and, therefore, an increased workload on their heart.

Musculoskeletal System

Table 16.2d provides an overview of the musculoskeletal system. See Figures 16.5^[23] and 16.6^[24] for images depicting the skeleton and muscles.

Table 16.2d. Overview of the Anatomy and Physiology of the Musculoskeletal System^[25],[26]

Pediatric Differences

Here are some pediatric considerations in regards to the anatomy and physiology of the musculoskeletal system^[28]:

• Children have more bones than adults, but as they grow up, some of their bones fuse together.
• When compared to older children, infants lack muscle tone and coordination so they require support while being held.
• The bones of children are softer than adults, meaning they will bend before breaking. Because they are more flexible, they can have severe injuries without the presence of a fracture.
• Children have growth plates in their long bones. Fractures to this area can affect their growth.

Eyes & Ears

Table 16.2e provides an overview of the eyes and ears and their associated functions. See Figures 16.7^[29] and 16.8^[30] for illustrations of the eyes and ears.

Table 16.2e. Overview of the Anatomy and Physiology of the Eyes and Ears^[31]

Figure 16.7 Anatomy of the Eye

Pediatric Differences

The eyes and ears of adults and children have similar components and functions, but there are pediatric differences that must be considered^[32],[33]:

• Children do not reach the full level of visual acuity of adults until seven years old.
• The eyes of children nine years old and younger are more sensitive to the sun when compared to adults.
• The eustachian tubes of children are smaller and positioned differently when compared to adults. This makes fluid drainage difficult and ear infections more likely.