The study of the body’s systems and structures and how they interact is known as anatomy and physiology. Anatomy is concerned with the physical arrangement of body parts, whereas physiology is concerned with the inner workings of cells, tissues, and organs. This section will go over the body’s major systems, including the musculoskeletal, circulatory, nervous, digestive, respiratory, and integumentary systems.
Musculoskeletal System (MSS)
The musculoskeletal system gives the body structure, allows movement, and physically protects the body’s other systems. Because of the large number of muscles and bones, the anatomy of the musculoskeletal system is complex. Memorizing each structure’s exact positions and roles is unimportant for national registry exams and EMS practice. Understanding the general structure of how the bones and muscles are arranged (spine, skull, ribcage, limbs, etc.) is important for understanding the effects of trauma and medical conditions.
The musculoskeletal system’s anatomy is based on the larger structures formed by the bones and muscles. The skull, spine, thoracic cage, pelvic girdle, and limbs are examples of these structures.
The skull consists of several flat bones that interlock to form a protective space for the brain. They also build the structure of the face and mouth and many muscle attachments that allow for full head movement.
The spine comprises interlocking vertebrae with a central channel for the spinal cord and nerve exit points. It, like the skull, protects the spinal cord and serves as an attachment point for muscles and ribs.
The thoracic cage, also known as the “rib cage,” provides rigidity to the chest, which is necessary for lung expansion and contraction, making the rib cage essential to the respiratory system. It also protects the vital organs inside the chest.
The pelvic girdle is one of the body’s most complex anatomical structures. It transfers the upper body’s weight from the spine to the legs and has numerous attachment points for various large muscle groups in both the trunk and the legs.
The limbs, like the pelvis, are complex, with numerous joints and attachment points that allow for precise and varied movement.
Muscles comprise a bundle of smaller fibres (myofibrils) attached to a bone by a fibrous tendon and innervated by one or more nerves from the peripheral nervous system, allowing for voluntary and involuntary contraction. All bodily movements are caused by muscles pulling against bones across joints. Because of the arrangement of the muscle fibres, this type of muscle is known as “Striated” or “Skeletal” muscle. Another type of muscle in the body is “smooth muscle,” which is found in many bodily systems. This type of muscle is loosely arranged and lacks the distinctive striations of the previously mentioned skeletal muscle.
Musculoskeletal physiology focuses on the structure of muscle cells and the chemical processes that allow them to contract.
Muscles are composed of bundles of muscle fibres containing a large number of sarcomeres. A specialized protein in these sarcomeres contracts in response to calcium release from the sarcolemma, a sheath surrounding the muscle fibres. A signal from a nerve that connects to the muscle causes calcium release. Glucose and oxygen provide the energy for contraction. Large blood vessels that run into them deliver these to the muscle.
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The Cardiovascular System
The circulatory system’s function is to deliver oxygen and glucose to the body’s cells and remove waste. It is made up of the heart, blood vessels, and blood. The circulatory system’s anatomy and physiology are extremely complex, but its essential elements can be broken down into a relatively simple framework.
On the surface, the circulatory system is simple: it consists of a pump, pipes, and the fluid they transport.
The heart is a four-chamber pump that fills with blood when relaxed and propels it through the body when pressed. The chambers are separated by valves that prevent blood from flowing backwards. The coronary arteries run across the heart’s surface, supplying oxygen to the muscle. A network of modified heart muscle cells within the heart muscle acts almost like neurons, transferring electrical signals through the heart in a precise and structured manner.
Blood vessels transport blood and regulate its flow to various body parts. The vessels are smooth muscle tubes that can expand and contract in response to hormone and nervous system signals. Vessels come in various sizes, with the largest near the heart and the smallest within the body’s various tissues. There are various types of vessels; arteries, arterioles, veins, venules, and capillaries all serve distinct functions that will be discussed in later sections.
Blood is not traditionally thought to have anatomy. Still, it does have many parts in the form of different cells, including red blood cells, white blood cells, platelets, and a variety of proteins/hormones/chemicals, all of which play different roles.
The many different types of cells in the heart and blood complicate the physiology of the circulatory system.
The heart’s muscle cells (cardiac myocytes) are electrically connected and do not require a nerve signal to contract. This allows them to beat rhythmically, allowing for effective blood pumping. The SA node, a collection of specially modified myocytes, acts as the pacemaker for a healthy heart, producing electrical signals that spread through the myocytes and result in a heartbeat. Other specialized myocytes serve as fast pathways for electrical signals, ensuring that the spread of electricity through the heart results in a coordinated and effective contraction.
As previously stated, blood is a complex mixture of cells and other compounds. The most important of these are red blood cells, which have a protein called hemoglobin that allows them to transport large amounts of oxygen from the lungs to tissue throughout the body. White blood cells fight infection, and platelets help seal any system holes.
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The Central Nervous System
The nervous system is in charge of the entire body. It has fibres that run across the entire body, controlling muscles, organs, and glands while also returning information to the spinal cord and brain, allowing them to make decisions. Dendrites receive signals, axons transmit them, and the cell body maintains the nerve cell are all parts of a neuron.
The nervous system is divided into two parts: the central and peripheral nervous systems. The central nervous system serves as the body’s control system, while the peripheral serves as communication lines relay information to and from the central system.
The brain and spinal cord comprise the central nervous system (CNS); these structures are made up of many neurons and support cells, with large blood vessels and capillaries supplying the energy required by the neurons.
The peripheral nervous system (PNS) is extensive and spans the entire body. These nerves perform various functions, including controlling movement in the body, controlling organ function, and returning sensory information from all over the body to the spinal cord and brain. The PNS nerves arise from the spinal cord.
The physiology of the nervous system revolves around nerves’ ability to transmit signals. They do so through “action potentials,” which allow signals to travel down the nerve’s axon and to receptors at the other end.
The opening and closing of voltage-sensitive ion channels on the neuron’s surface generate action potentials. This causes a “wave” of electrical energy to travel down the neuron and eventually release neurotransmitters from the neuron’s end.
The variety of receptors on neurons and muscles allows neurotransmitters to be released due to an action potential to affect other neurons by stimulating other action potentials or causing calcium to be released, causing muscles to contract.
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The Digestive Process
The digestive system’s purpose is to break down and absorb ingested material to be used for energy and create new cells within the body.
The digestive system anatomy is divided into hollow and solid organs. The hollow organs transport and process food, while the solid organs act as support systems, ensuring the digestion process runs smoothly.
The esophagus, stomach, and intestines are hollow organs: The physical tube that connects the mouth to the stomach is known as the esophagus. Food is physically ground up in the stomach and chemically digested with acid. The nutrients and water from the ground-up food are then absorbed by the intestines with the help of liver bile and pancreatic enzymes.
The liver and pancreas are solid organs: The liver has two functions: it produces bile, which aids in fat absorption by the intestines, and it detoxifies the blood. The pancreas, like the liver, serves two functions. It generates enzymes that degrade protein and hormones, thereby balancing blood glucose.
The digestive system’s physiology heavily depends on the organ in question, and many play multiple roles. The hollow organs are typically specialized in mechanical food breakdown and absorption. On the other hand, solid organs produce and secrete substances that aid in the chemical breakdown of food.
The stomach and intestines contain various special cells and receptors that detect and absorb their contents.
Hepatocytes, or liver cells, produce bile from waste in the body, which aids in fat absorption in the intestines. These same hepatocytes contain complex enzymes that break down the countless toxins the body produces.
There are various types of cells in the pancreas. Some secrete enzymes that degrade proteins, while others, known as “islets,” secrete insulin and glucagon hormones, which regulate glucose balance in the blood.
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System of Respiration
The respiratory system is similar to the circulatory system. Its function is to bring oxygen from the surrounding environment into contact with the blood inside microscopic capillaries. It has a close relationship with the cardiovascular and musculoskeletal systems. The lungs contain some of the largest blood vessels in the body, and the chest wall is essential in the inspiration and expiration of air.
The respiratory system is divided into upper and lower respiratory tracts. The division takes place at the level of the larynx. The nasopharynx and oropharynx make up the upper respiratory tract. In comparison, the lower respiratory tract comprises the trachea, bronchi, bronchioles, and lungs, with the diaphragm moving air through the system.
The upper respiratory tract is in charge of cleaning and warming the air before passing it to the lower airways. The upper respiratory tract also transports food and fluids to the esophagus and aids speech production.
The larynx is a cartilage “box” that separates the gastrointestinal and respiratory systems. The epiglottis is a physical flap that protects the airway from food and fluids. The rest of the larynx is specialized for speech production; the vocal cords and various cartilages can change shape to allow air to pass over them, allowing speech to be produced.
The lower respiratory tract transports air to the alveoli via an inverted branching tree composed of the trachea, bronchi, and bronchioles. These microscopic sacks have thin walls and thin-walled capillaries. These allow blood to come into direct contact with air.
The diaphragm is a sheet of muscle at the base of the lungs that creates negative pressure in the chest to pull air into the airways. When the diaphragm contracts, the air is drawn into the chest, a process known as inspiration.
The respiratory system’s physiology is best divided into the airways and the lungs.
The airways have physiologic mechanisms that protect them from the environment’s countless viruses and bacteria. Countless mucus-secreting cells form a protective layer around the inner nose/mouth, trachea, and bronchi/bronchioles, inhibiting bacterial growth and trapping inhaled contaminants. In the lower airway, these musical cells are paired with cilia (trachea, bronchi, etc.) They move around, pushing mucus and contaminants up and out of the lower airways.
The primary physiologic function of the lung is the exchange of gases between the blood and the air. They do so through the alveoli’s incredibly thin walls, allowing diffusion to move gases from high-concentration areas to low-concentration areas naturally.
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The Intestinal System
The integumentary system is a physical barrier between the body’s internal systems and the outside world. It is critical to regulating the body’s internal environment, keeping fluids in and bacteria out, and providing a regenerating layer that prevents permanent damage to the body’s more fragile cells.
The anatomy of the integumentary system is more complicated than it appears. The epidermis, dermis, and subcutaneous layers are the three main layers.
The epidermis is a layer of dead cells that serves as a “sacrificial layer” for the body. This layer of cells gradually peels away, protecting the more vulnerable layers beneath. The dermis is the living skin layer that contains nerves, blood vessels, sweat glands, oil glands, nerves, blood vessels, sweat glands, and oil glands. The subcutaneous layer is a major area of fat storage that also serves as a significant insulating layer for the body.
The integumentary system’s physiology is based on continuously dividing stem cells in the dermis that form the thick epidermis. The dermis also contains numerous capillaries, nerves, and glands that regulate temperature via vasoconstriction/vasodilation and diaphoresis mechanisms (sweating).
The use of human bodily fluids such as urine has been in the past commonly used in teaching labs’ This
practice has been severely restricted for various reasons, one being the potential for exposure to
infectious agents. There are alternatives to using actual bodily fluids for learning although they are not
often the best practice for learning disease infection and prevention or practicing the scientific method
and use of controls. The following is adapted from the Student Urinalysis and Analysis Activity Kit from
Carolina Biological Supply, 20i”7.
This virtual lab exercise on Urinalysis is designed to help understand some of the basics of using
biological samples compared to controls in determining an interpretation of real data. Urinalysis is used
by doctors to assess various factors of urine, including color and pH, that could indicate disease. These
factors are normally kept in balance by the kidneys as they filter blood and produce urine but may
change under certain conditions like disease or medication use, or even with certain foods. Table L
shows the urine colors and possible things that affect color change and potential disease associated with
the specific urine color (Carolina Biological Supply, 2017).