EMT Exam: Anatomy and Physiology - Body Systems

As an EMT-Basic, you should already be familiar with the physiology and anatomy of the human body and the functions of different body systems. In this section, you’ll find a brief review of the different body systems and their functions.

1. The Respiratory System
The respiratory system is made up of the parts of the body through which air passes, including the mouth, nose, lungs, pharynx, trachea, and bronchi. Collectively, these passageways are known as the airway. The main function of the respiratory system is to take oxygen into the lungs through either the nose or the mouth and then release carbon dioxide back through the nose or the mouth.

The respiratory system further breaks down into the upper respiratory system and the lower respiratory system, which work together to inhale and exhale air. The upper respiratory system consists of the nose, nasal cavity, and pharynx (throat). The lower respiratory system consists of the larynx (voice box), trachea (windpipe), bronchi, and lung tissues. When you breathe in oxygen, it passes through the upper respiratory system into the lower respiratory system and then to the lungs, where it’s exchanged for carbon dioxide, which is released from the body through the mouth or nose when you exhale.
Each lung works independently of the other to ensure that if one lung is damaged, the other lung remains functional. The left lung is smaller than the right lung to accommodate the heart. The lungs are divided into sections called lobes. The left lung has two lobes and the right lung has three lobes.
The EMT-Basic should be familiar with how the respiratory system works and be able to recognize the signs of irregular breathing. You must ensure that the patient’s airway remains open and clear at all times. A blocked airway can result in death if not properly treated.

2. The Circulatory System
The circulatory system comprises the heart, blood vessels, and blood. The heart is the main organ of the circulatory system. It’s also one of the most important muscles in the body. Its main function is to pump blood to other organs throughout the body for survival. The heart has four chambers: two upper chambers, called the atria, and two lower chambers, called the ventricles. The atria pump blood into the ventricles, and the ventricles pump blood out of the heart. One-way valves pump blood in one direction and prevent blood from pumping back into the heart. The heart contains cells that generate electrical impulses that cause the heart to beat. The number of times the heart beats per minute is called the heart rate. A normal resting heart rate for an adult can range from 60–80 beats per minute.

Fact: The heart can pump more than 3,000 gallons of blood per day.

The heart pumps blood through the body’s blood vessels, which deliver blood to the organs. Arteries are blood vessels that carry blood away from the heart. The largest artery in the human body is the aorta, which is connected to the left ventricle of the heart and travels straight down the spine to the abdomen. Arteries expand and contract with each beat of the heart to help push blood through the body. These vessels branch off into smaller vessels called arterioles. Arterioles are responsible for regulating blood flow and blood pressure. These small vessels branch off into even smaller blood vessels called capillaries.

Gas exchange takes place within the thin walls of capillaries. These vessels join together to form a venule, which returns blood to the heart. Unlike arteries, which branch into smaller vessels the farther they are from the heart, venules expand as they get closer to the heart and become veins. The largest veins in the body are the inferior vena cava and the superior vena cava. The blood travels directly into the heart from the inferior vena cava and the superior vena cava.

Fact:The aorta has a diameter the size of your thumb.

Blood is an important bodily fluid that serves many functions throughout the body. It’s made up of the following components:
- Red blood cells: contain hemoglobin, which transports oxygen and carbon dioxide in the blood
- White blood cells: help the body fight off disease and infection
- Platelets: responsible for blood clot formation
- Plasma: liquid part of the blood that carries the rest of the components through the circulatory system



The pathway of blood through the chambers and valves of the heart.


3. The Skeletal System
The skeletal system involves the bones of the body. The skeletal system contains 206 bones that are responsible for the structure, protection, and movement of the body. Bones enable us to stand upright, protect our organs, and allow us to move. The skeletal system further breaks down into the axial skeleton and the appendicular skeleton.

a. Axial Skeleton
The axial skeleton contains the skull, spinal column, and ribs. It’s very important for the EMT-Basic to be familiar with the different bones that make up the skull. The skull contains the cranium and the bones of the face. The cranium, which consists of eight bones, protects the brain. Bones fit together with joints called sutures, which enable the bones to move slightly without breaking. The face consists of 14 bones and includes the mandible (lower jaw), maxilla (upper jaw), zygomatic bones (cheekbones), nasal bones (nose), and orbits (eye sockets).
The spinal column, rib cage, and sternum form the thoracic cavity, which provides the shape for the chest and protects the organs. The spinal column’s main functions are to provide structure and support for the body and protect the spinal cord. The bones of the spinal column are called vertebrae, and there are 33 vertebrae in the spinal column. The vertebrae stack on top of each other, with soft discs between them for support.

The rib cage consists of 12 pairs of ribs. Each rib is attached to the back of the body to one of the thoracic vertebrae. The first 10 ribs are attached to the front of the body to the sternum. The last two ribs are called floating ribs because they extend laterally from the vertebrae. The sternum (breastbone) is an important bone of the body because it protects the heart. It is split into three sections of bones: manubrium (upper), body (middle), and xyphoid (lower).

b. Appendicular Skeleton
The appendicular skeleton contains the rest of the bones in the body. It’s impossible to cover each bone of the appendicular skeletal system in this section, so we’ll give an overview of some of the bones in the lower and upper parts of the skeleton. The EMT-Basic exam asks questions about the many different bones located throughout the body, so be sure that you’re familiar with all of the bones in the body.
The lower part of the skeletal system refers to the pelvis, legs, and feet. The pelvis is the connecting point between the lower skeleton and the spinal column. It’s split into left and right halves, and each side contains the ilium (hip bone), ischium (lower pelvis), and pubis bones. The ischium attaches to the femur (thigh bone), which is the largest bone of the body. The lower femur attaches to the tibia (shin bone) and fibula of the lower leg. The point of connection between the femur and the tibia and fibula is called the patella (kneecap). The fibula connects to the ankle bone. The bones of the feet are called tarsals, which branch into the phalanges (toes).

The upper part of the skeletal system includes the trunk, arms, and hands. The arms connect to the shoulder girdle, which consists of two bones: the scapula, which attaches to the rib cage, and the clavicle (collarbone). The shoulder bones connect to the humerus, the largest bone of the upper skeleton. The humerus attaches to the lower arm bones: the radius and the ulna. The radius runs along the thumb side of the lower arm and the ulna runs along the pinky finger side of the lower arm. These bones connect to the carpal bones, metacarpal bones, and phalanges (fingers) of the hand.




Major bones of the axial and appendicular skeletons.


4. The Muscular System
The muscular system includes the muscles of the body, which attach to the skeletal system. Muscles enable the bones to move. They contract and then relax, which causes the body to move in any direction. If you didn’t have any muscles, you wouldn’t be able to move. Muscles split into three different types: skeletal, cardiac, and smooth.

Fact:Muscle tissue accounts for half of a person’s body weight.
 

Skeletal muscles attach to the bones of the body. The primary function of the skeletal muscles is to provide movement. These muscles are also called voluntary muscles because you use your brain to move these muscles. When you want to move your hand, a signal travels from the brain to your hand to cause it to move. These muscles account for the greatest amount of muscle mass within the body.
The heart is made up of cardiac muscles. These muscles keep the heart beating and blood moving throughout the body. These muscles are called involuntary muscles because they contract and relax on their own. You don’t have to think about the muscles that make your heart beat.
Smooth muscles control the flow through the tubes of the body. They move blood through the blood vessels and food through the digestive system. (The digestive system is explained later in this guide.) These are also involuntary muscles.

5. The Integumentary System
The skin is not only the largest organ of the human body, but also one of the most important. Skin is part of the integumentary system. It protects the body from environmental factors, such as extreme heat and cold. The skin prevents us from drying out and prevents bacteria and other organisms from entering the body. Skin also plays an important role in regulating body temperature. When your body gets too hot, the blood vessels dilate, and sweat is released. As sweat evaporates, your body cools down. When your body gets too cold, the blood vessels contract to prevent heat loss. Skin is also a sensory organ that contains receptors that can detect heat, cold, touch, pressure, and pain. These receptors transmit information to the central nervous system.

The skin has three layers: epidermis (outer layer), dermis (middle layer), and subcutaneous (innermost layer). The sweat glands, hair follicles, blood vessels, and nerve endings are found in the dermis. The subcutaneous layer connects the skin to the body’s tissues and stores fat, which aids the body with insulation and storing energy.

6. The Nervous System
The nervous system is a highly complex system that controls all of the functions of the human body, including voluntary and involuntary activities, thoughts, memory, and emotion. It’s split into two components: the central nervous system and the peripheral nervous system.
The brain and spinal cord make up the central nervous system, which regulates the body’s functions and is responsible for communication and making decisions. The peripheral nervous system consists of the sensory and motor nerves in the rest of the body. Sensory nerves carry information from the body to the central nervous system. These nerves enable the brain to make decisions using information about the environment, pain, pressure, and body position. Motor nerves carry information from the central nervous system to the body. Signals from the motor nerves enable the movement of skeletal muscles.
The brain controls all of the functions of the body. It’s one of the largest organs in the body, and it’s also one of the most complicated. It sends signals to other body parts, and it controls the movement of muscles and nerves and the functions of the organs. The brain is divided into four different sections or lobes:

- Frontal lobe: controls the body’s movement, reasoning skills, language, and cognition
- Parietal lobe: controls the body’s senses and sensory information such as pressure, touch, and pain
- Temporal lobe: controls hearing, language, and memories
- Occipital lobe: controls vision
The lobes of the brain further divide into smaller sections:
- Brain stem: controls heart rate, respiratory rate, swallowing, and coughing
- Diencephalon: controls emotions, hunger, thirst, and body temperature
- Cerebrum: controls the senses, including hearing, vision, taste, smell, and touch; also controls personality
- Cerebellum: controls balance and fine motor skills

Because the brain is one of the most important organs of the body, it needs a lot of protection. In addition to the cranial cavity, it’s protected by different coverings, or meninges, that are split into three layers: dura mater (outer later), arachnoid layer (middle layer), and pia layer (inner layer). It’s also surrounded by a cerebrospinal fluid that circulates throughout the brain and spinal cord.
The brain contains 12 pairs of cranial nerves that are responsible for the sensory and motor functions of the body. You should be familiar with the different parts and nerves within the brain and how they work.

Fact: The average brain weighs between 3 and 3.5 pounds.




The four lobes of the adult brain and the cerebellum.

7. The Gastrointestinal System
The gastrointestinal system, also called the digestive system, provides the human body with nourishment and energy through the digestion of food. This system breaks the food we eat into the essential nutrients we need for survival. The process of digestion is divided into two stages. The first state is actual digestion, during which food breaks down into molecules that the body can use for energy. The second stage is absorption. In the absorption stage, the molecules that result from actual digestion are absorbed into the body for use.



The parts of the digestive system.

Anatomically, the gastrointestinal system is made up of two distinct sections: the gastrointestinal tract and the alimentary canal. The gastrointestinal tract includes all of the organs and structures used in digestion. The alimentary canal is the long, continuous tube that runs between the mouth and the anal opening. Food travels through the alimentary canal as it’s digested.
The process of digestion begins in the mouth as you chew your food. Chewing grinds up food, making it easier to swallow. Saliva produced by the parotid glands contains digestive enzymes that assist in this early stage of digestion. As you swallow food, it passes through the pharynx (throat) and into the esophagus, which is a muscular tube that secretes mucus and expands and contracts to push food downward into the stomach. No digestion occurs in the esophagus.
The stomach serves as a holding tank in the digestive process. The stomach produces digestive enzymes that contribute to the breakdown of food, and this is where protein digestion takes place. When these enzymes are released, the stomach converts the food into chime, which is a semi-fluid mass of undigested food that is passed into the small intestine.
The small intestine is a long tube that measures 10–12 feet in length. This section of the gastrointestinal system is responsible for the majority of digestion and absorption in the body. The small intestine has three distinct parts: the duodenum (first portion), the jejunum (middle portion), and the ileum (last portion). The small intestine leads into the large intestine. The two connect at the ileocecal valve. The large intestine, also called the colon, is the site of the last steps in the digestive process. The absorption of water stops, thereby solidifying the food. Intestinal bacteria help to convert proteins into various substances that may be absorbed or eliminated.
A substance called bile is produced by the liver. Bile assists in the breakdown of fats and metabolizes carbohydrates and proteins. It also serves as a filter for toxic substances and stores glucose and vitamins. The gallbladder houses bile made by the liver. When necessary, the gallbladder excretes this bile into the large intestine. The pancreas is responsible for the secretion of some digestive enzymes and hormones that regulate blood sugar. Finally, the colon pushes the remaining indigestible food into the rectum. The rectum forces these waste products out of the body through the anus. Liquid waste is eliminated by the urinary system.

8. The Urinary System
The urinary system produces, stores, and eliminates urine. It’s composed of two kidneys, two ureters, a bladder, and a urethra. The kidneys filter blood and remove toxins and then send these toxins to the bladder for elimination. The kidneys also regulate blood volume and the body’s pH level. The kidneys need a constant supply of blood. An EMT-Basic should keep this in mind when treating patients in a state of hypoperfusion, a condition that causes the flow of blood from the kidneys to stop and redirect to the heart, lungs, and brain. If blood flow to the kidneys stops, kidney failure could result. If the kidneys fail, toxins can build up in the body and lead to infection or death.
The ureters are muscular tubes that move urine from the kidneys to the bladder. The bladder stores the urine until it’s ready to be eliminated by way of the urethra, a tube that connects the bladder to the genitals.



The urinary system.

9. The Endocrine System
The endocrine system is a highly complex system composed of a series of glands located throughout the body. These glands produce chemicals known as hormones. Hormones help regulate the activities and functions of many other body systems. The structures that make up the endocrine system include the pituitary, pineal, parathyroid, thyroid, and adrenal glands.
The pituitary gland is the primary gland of the endocrine system. Often called the “master gland,” this tiny gland, which is located at the base of the brain, is responsible for the secretion of hormones that move throughout the body and stimulate the production of various hormones in other glands. Among the most important hormones released by the pituitary gland is growth hormone, which is responsible for normal growth and development during childhood.
The pineal gland produces melatonin, which is thought to inhibit the production of gonadotropin. It’s also thought to play a role in the control of sleep patterns. The parathyroid glands produce hormones that regulate the body’s levels of calcium and phosphorus. The thyroid gland secretes hormones that regulate metabolism, which plays a vital role in digestion.
The adrenal glands are composed of two separate endocrine organs: adrenal cortex and adrenal medulla. The adrenal cortex secretes hormones that help control blood sugar and burn proteins and fats. It also plays an important role in the body’s response to fever, illness, and injury. The adrenal medulla is responsible for the production of epinephrine, which can elevate heart rate, open airways to increase respiration, and increase muscular blood flow. The release of epinephrine is often a reaction to a sudden, intense emotion.
Some body parts are not actually part of the endocrine system but contain endocrine tissue. The pancreas, for example, produces insulin and glucagon. These two hormones are vital to the regulation of blood sugar.
The endocrine system also plays an important role in sexual development. The testicles and ovaries are both endocrine organs that produce testosterone and estrogen and progesterone, respectively.

11. The Reproductive System
The reproductive system consists of sexual organs, gonads, and genitalia. Males and females have different reproductive organs. The female gonads are the ovaries and the male gonads are the testes (testicles). Gonads secrete hormones such as testosterone in males and estrogen and progesterone in females. They also produce eggs in females and sperm in males. These are necessary to create another life.
The male’s reproductive organs are located outside the body. These organs include the testes (testicles), the duct system, the accessory glands, and the penis. In a mature male, the testes produce and store sperm. The male’s duct system includes the epididymis and the vas deferens. The epididymis is a set of coiled tubes that connects to the vas deferens, which is a muscular tube used to transport semen, the fluid that contains sperm. The epididymis and testes are located in a sac called the scrotum. This sac helps regulate the temperature of the testes so they can produce sperm. The accessory glands include the seminal vesicles and prostate gland. These provide fluids to lubricate the duct system and nourish the sperm. The seminal vesicles are attached to the vas deferens and the prostate gland is situated near the base of the urethra, which eliminates urine and transports semen outside the body through the penis.
The penis is made up of a shaft and glans. The shaft is the main part of the penis and the glans is the tip or head. Semen and urine pass through a small opening at the end of the glans. The male sexual organs work together to produce and release semen into the reproductive system of the female during sexual intercourse.
Unlike the male’s reproductive organs, the female’s reproductive organs are located inside the body. These organs include the vulva, labia, vagina, uterus, fallopian tubes, and ovaries. The vulva is the external part of the reproductive organs, which covers the vaginal opening. The labia are two flaps of skin surrounding the vaginal opening. The labia open up to the vagina, which is a long, muscular tube that extends to the uterus. The vaginal walls can stretch and contract to accommodate a penis during intercourse and a fetus during childbirth.
The uterus is the organ responsible for contracting and expelling the fetus during childbirth. The two fallopian tubes connect the uterus to the ovaries, which produce, store, and release eggs into the fallopian tubes in a process called ovulation. Ovulation is the point in a woman’s cycle when a mature egg is released from the ovary. A woman can get pregnant during ovulation.


Related Topics You Should Review:
- Functions of the different parts of the respiratory system
- Blood circulation
- Bones of the skeletal system
- Vertebrae of the spinal column
- Muscles of the muscular system
- Tissues of the body
- Divisions and functions of the brain
- Nerves of the brain
- Differences between an adult’s brain and a child’s brain
- Diet and nutrition
- Hyperglycemia and hypoglycemia
- Endocrine disorders
- Sexual intercourse and reproduction
- Other systems of the body, such as the lymphatic and immune systems