Physiological and Anatomical Characteristics of the Skeletal and Muscular Systems in the Human Body

Anatomy and Physiology of the Skeletal and Muscular Systems

Introduction

Today, human health is being threatened on multiple fronts and it is not surprising that there is growing interest in developing a better understanding about the human body’s various systems and the respective roles they play in maintaining good health. Some people may intuitively recognize the importance of the skeletal and muscular systems to human health, but far too few understand the fundamental anatomy and physiology of these systems. In response to this constraint, the purpose of this paper is to provide a discussion concerning the anatomy and physiology of the skeletal and muscular systems in the human body as well as selected associated disorders that are associated with those systems. Following this review, a summary of the findings is provided in the conclusion.

The Skeletal System

1. Anatomy

It is important to note that although the human skeletal system is widely regarded as a static structure that provides the human body with structural support only, the bones that make up the skeletal system also function as organs. In addition, the other organs that comprise the skeletal system include cartilage, tendons and ligaments (Cowen & Kahai, 2021). Comprised mainly of water and collagen, cartilage is a durable, smooth substance that serves to prevent individual bones in the skeletal system from rubbing against each other by coating the ends of bones (Anatomy of the joints, 2007). Similarly, tendons and ligaments are situated proximately to joints and also support individual bones in the skeletal system and facilitate the movement of joints (Anatomy of the joints, 2007). While tendons are comprised of fibrous cords that serve as connection points for bones and muscles (discussed further below), ligaments are strong tissues that connect bones to each other at joints (Anatomy of the joints, 2007).

2. Physiology

The skeletal system provides a number of physiologically essential features for the human body. These critical features include defining the body’s overall shape, maintaining homeostasis, facilitating breathing and locomotion, serving as a protective framework for internal vital organs, and generating the blood cells that are essential for life (Cowen & Kahai, 2021). In addition, it is also noteworthy that despite their rigid and static appearances, bones continue to grow and experience biological and structural changes throughout the human lifecycle in response to what types of demands on the body that are involved (Cowen & Kahai, 2021).

The human skeletal system is divided into two main parts: 1) the axial skeleton and 2) the appendicular skeleton (Docherty, 2007). The axial skeleton segment provides the physical structure for the human body’s central axis while the appendicular skeleton segment is comprised of the bones in the lower and upper limbs as well as the pelvis and shoulders (Human skeletal systems, 2022). The 206 total bones that are contained in these two main parts of the skeletal system are not impervious to injury, however, as noted below.

3. Disorders

The cozy scene of injured skiers sitting in front of a fireplace sipping a hot beverage while nursing a broken leg in a plaster cast is stereotypical, but this picture does not accurately reflect the major impact that broken bones can have on the entire human anatomy. Bone fractures, though, exist along a continuum ranging from simple fractures that can be treated with supportive interventions such as reduction (e.g., lining the fractured bones up so they heal properly) as well as placing the fracture in a splint or cast. In other cases, however, complicated fractures may require surgical interventions in order to repair the damage to the maximum extent possible (Cowan & Kahai, 2022). In any event, bone fractures represent major disorders that can adversely affect the skeletal system in ways that diminish quality and length of human life (Cowan & Kahai, 2022).

Given the major impact that bone fractures can have on the entire body, it is not surprising that orthopedists are interested in identifying the most efficacious interventions. In this regard, a retrospective study of 88 pediatric patients with bone fractures was conducted by Abdelgawad et al. (2013) to determine how long internal reductions required since casting for these patients was impracticable. The results of this study showed that although all 20 fractures healed successfully, the average time for healing varied depending on the number of fractures that were involved, ranging from 6.7 weeks for two fractures, 9.3 weeks for three fractures and 13.3 weeks for four fractures (Abdelgawad et al., 2013). These findings indicate that not only does the severity of the fracture itself affect healing rates, but the number of fractures does as well.

The Muscular System

1. Anatomy

The human skeletal system would just be a static structural framework without the muscular system. Although they differ in their physiology (discussed further below), the fibrous tissues that comprise human muscles are generally strong and function in pairs through flexion and contraction to generate movement in joints (Anatomy of the joints, 2007). Because different muscles perform different functions in the human body, they do not share the same type of structures. In sum, the three kinds of muscles in the human muscular system are: 1) skeletal muscles, 2) smooth muscles and 3) cardiac muscles (Robertson, 2015) and the respective functioning of these muscles is described below.

2. Physiology

Skeletal muscles stretch and contract in order to support the human body and facilitate locomotion as well as other bodily movements and their operation is voluntary; however, they are vulnerable to easy fatigue (Robertson, 2015). The cause of such easy fatigue relates to the fact that skeletal muscles contain large numbers of blood vessels and nerves which are only designed to function for comparatively short amounts of time (Robertson, 2015). In other words, skeletal muscles help people walk, run, jump, reach for things and generally navigate their surroundings.

In contrast to skeletal muscles, smooth muscles are also muscles that are located in the body in locations besides the heart and are termed “smooth” to differentiate them from skeletal muscles’ striated appearance. Although smooth muscles are not as powerful as skeletal muscles, they do not require the same level of strength since their primary function is to move foods and fluids through the digestive system (Robertson, 2015), In very sharp contrast to both skeletal and smooth muscles, the structure of cardiac muscles ensures that they never completely fatigue until death when they cease powering the heart’s blood pumping action. In appearance, cardiac muscles resemble striated skeletal muscles (Robertson, 2015).

The malleability of skeletal muscle tissues is controlled by muscle protein synthesis and the corresponding rate of their breakdown (Smeets et al., 2019). The research to date indicates that the balance of protein synthesis and breakdown rates of skeletal muscle plasticity ranges between 0.02 and 0.09% per hour, but there is a clear need for additional research in this area to more clearly define these breakdown rates (Smeets et al., 2019).

3. Disorders

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease and motor neurone disease, is a neurodegenerative disease that results in the loss of control over the muscular system. The cause or causes of ALS remain undetermined, although genetics and various environmental factors are believed to be involved (Riacho et al., 2021). This disorder is essentially incurable at present, although there are some proven rehabilitative and palliative care steps that can help sufferers retain their quality of life for as long as possible (Riacho et al., 2021).

Integration

While it is possible to describe the skeletal and muscular systems discretely, it is far more difficult to discuss the manner in which the musculoskeletal system operates separately from each other. Both of these systems depend on each other to achieve locomotion and other movements, with the skeletal system providing the muscular system with the mechanical structure that is needed to secure muscles and move them through contraction. In many ways, the inextricable interrelationship between the muscular and skeletal systems is analogous the mechanical functioning of the recently deployed James Webb Space Telescope which features several motors and stainless-steel cables to manipulate its mirror array. In sum, the skeletal and muscular systems combine to provide humans with the abilities they need to survive in a hostile environment through fight or flight as well as simply standing (and staying) upright to survey their surroundings.