The job of the respiratory system is the exchange of gases between the body and the outside air.
This process, called respiration, actually consists of two parts. In the first part, oxygen in the air is drawn into the body and carbon dioxide is released from the body through the respiratory tract.
In the second part, the Circulatory System delivers the oxygen to body cells and picks up carbon dioxide from the cells in return.
The use of the word respiration in relation to gas exchange is different from its use in the term cellular respiration.
Recall that cellular respiration is the metabolic process by which cells obtain energy by “burning” glucose.
Cellular respiration uses oxygen and releases carbon dioxide. Respiration by the respiratory system supplies the oxygen and takes away the carbon dioxide.
Organs of the Respiratory System
The organs of the respiratory system that bring air into the body are shown in Figure below.
Refer to the figure as you read below about the passage of air through these organs
Journey of a Breath of Air
Take in a big breath of air through your nose. As you inhale, you may feel the air pass down your throat and notice your chest expand.
Now exhale and observe the opposite events occurring. Inhaling and exhaling may seem like simple actions, but they are just part of the complex process of respiration, which includes these four steps:
Ventilation
Pulmonary gas exchange
Gas transport
Peripheral gas exchange
Ventilation
Respiration begins with ventilation. This is the process of moving air in and out of the lungs. The lungs are the organs in which gas exchange takes place between blood and air.
Air enters the respiratory system through the nose. As the air passes through the nasal cavity, mucus and hairs trap any particles in the air. The air is also warmed and moistened so it won’t harm delicate Tissues of the lungs.
Next, the air passes through the pharynx, a long tube that is shared with the Digestive System. A flap of connective tissue called the epiglottis closes when food is swallowed to prevent choking.
From the pharynx, air next passes through the larynx, or voice box. The larynx contains vocal cords, which allow us to produce vocal sounds
After the larynx, air moves into the trachea, or wind pipe. This is a long tube that leads down to the chest.
In the chest, the trachea divides as it enters the lungs to form the right and left bronchi.
The bronchi contain cartilage, which prevents them from collapsing. Mucus in the bronchi traps any remaining particles in air. Tiny hairs called cilia line the bronchi and sweep the particles and mucus toward the throat so they can be expelled from the body.
Finally, air passes from the bronchi into smaller passages called bronchioles. The bronchioles end in tiny air sacs called alveoli.
Pulmonary Gas Exchange
Pulmonary gas exchange is the exchange of gases between inhaled air and the blood. It occurs in the alveoli of the lungs.
Alveoli (singular, alveolus) are grape-like clusters surrounded by networks of thin-walled pulmonary capillaries.
After you inhale, there is a greater concentration of oxygen in the alveoli than in the blood of the pulmonary capillaries, so oxygen diffuses from the alveoli into the blood across the capillaries (see Figure below).
Carbon dioxide, in contrast, is more concentrated in the blood of the pulmonary capillaries than in the alveoli, so it diffuses in the opposite direction.
Gas Transport
After the blood in the pulmonary capillaries becomes saturated with oxygen, it leaves the lungs and travels to the heart.
The heart pumps the oxygen-rich blood into arteries, which carry it throughout the body.
Eventually, the blood travels into capillaries that supply body tissues. These capillaries are called peripheral capillaries.
Peripheral Gas Exchange
The cells of the body have a much lower concentration of oxygen than does the oxygenated blood in the peripheral capillaries.
Therefore, oxygen diffuses from the peripheral capillaries into body cells.
Carbon dioxide is produced by cells as a byproduct of cellular respiration, so it is more concentrated in the cells than in the blood of the peripheral capillaries. As a result, carbon dioxide diffuses in the opposite direction.
Back to the Lungs
The carbon dioxide from body cells travels in the blood from the peripheral capillaries to veins and then to the heart.
The heart pumps the blood to the lungs, where the carbon dioxide diffuses into the alveoli.
Then, the carbon dioxide passes out of the body through the other structures of the respiratory system, bringing the process of respiration full circle.
Gas Exchange and Homeostasis
Gas exchange is needed to provide cells with the oxygen they need for cellular respiration. Cells cannot survive for long without oxygen. Gas exchange is also needed to carry away carbon dioxide waste. Some of the carbon dioxide in the blood dissolves to form carbonic acid, which keeps blood pH within a normal range.
Blood pH may become unbalanced if the rate of breathing is too fast or too slow. When breathing is too fast, blood contains too little carbon dioxide and becomes too basic. When breathing is too slow, blood contains too much carbon dioxide and becomes too acidic. Clearly, to maintain proper blood pH, the rate of breathing must be regulated.
Regulation of Breathing
To understand how breathing is regulated, you first need to understand how breathing occurs.
How Breathing Occurs
Inhaling is an active movement that results from the contraction of a muscle called the diaphragm. The diaphragm is large, sheet-like muscle below the lungs (see Figure below).
When the diaphragm contracts, the ribcage expands and the contents of the abdomen move downward. This results in a larger chest volume, which decreases air pressure inside the lungs.
With lower air pressure inside than outside the lungs, air rushes into the lungs. When the diaphragm relaxes, the opposite events occur.
The volume of the chest cavity decreases, air pressure inside the lungs increases, and air flows out of the lungs, like air rushing out of a balloon.
Control of Breathing
The regular, rhythmic contractions of the diaphragm are controlled by the brain stem. It sends nerve impulses to the diaphragm through the autonomic nervous system.
The brain stem monitors the level of carbon dioxide in the blood. If the level becomes too high, it “tells” the diaphragm to contract more often.
Breathing speeds up, and the excess carbon dioxide is released into the air.
The opposite events occur when the level of carbon dioxide in the blood becomes too low. In this way, breathing keeps blood pH within a narrow range.
Diseases of the Respiratory System
When you have a cold, your nasal passages may become so congested that it’s hard to breathe through your nose.
Many other diseases also affect the respiratory system, most of them more serious than the common cold.
The following list includes just a sample of respiratory system diseases.
Asthma is a disease in which the air passages of the lungs periodically become too narrow, often with excessive mucus production. This causes difficulty breathing, coughing, and chest tightness. An asthma attack may be triggered by allergens, strenuous exercise, Stress, or other factors.
Pneumonia is a disease in which some of the alveoli of the lungs fill with fluid so gas exchange cannot occur. Symptoms usually include coughing, chest pain, and difficulty breathing. Pneumonia may be caused by an infection or injury of the lungs.
Emphysema is a lung disease in which walls of the alveoli break down so less gas can be exchanged in the lungs. This causes shortness of breath. The damage to the alveoli is usually caused by smoking and is irreversible
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The respiratory system is a group of organs that work together to take in oxygen and release carbon dioxide. It is made up of the nose, pharynx, larynx, trachea, bronchi, bronchioles, lungs, alveoli, diaphragm, ribs, intercostal muscles, and pleura.
The nose is the organ of smell. It is also the first part of the respiratory system. The nose is divided into two nostrils, which lead to the nasal cavity. The nasal cavity is lined with mucus membranes, which help to warm and moisten the air that we breathe. The nasal cavity also contains hair follicles and mucus glands, which help to filter the air that we breathe.
The pharynx is a muscular tube that connects the nose and mouth to the larynx. The pharynx is also involved in swallowing and speaking.
The larynx is a voice box. It is located at the top of the trachea. The larynx contains the vocal cords, which vibrate to produce Sound.
The trachea is a tube that connects the larynx to the bronchi. The trachea is also known as the windpipe.
The bronchi are two tubes that branch off from the trachea. The bronchi lead to the lungs.
The bronchioles are small tubes that branch off from the bronchi. The bronchioles lead to the alveoli.
The alveoli are tiny air sacs in the lungs. The alveoli are where gas exchange takes place.
The diaphragm is a muscle that separates the chest cavity from the abdominal cavity. The diaphragm helps to move air in and out of the lungs.
The ribs are bones that protect the lungs. The ribs are attached to the spine and the sternum.
The intercostal muscles are muscles that lie between the ribs. The intercostal muscles help to move the ribs, which helps to move air in and out of the lungs.
The pleura is a membrane that surrounds the lungs. The pleura helps to keep the lungs in place.
The respiratory system works by taking in oxygen from the air and delivering it to the blood. The blood then carries the oxygen to all of the cells in the body. The cells use the oxygen to produce energy. The respiratory system also removes carbon dioxide from the blood. The carbon dioxide is then exhaled out of the body.
The respiratory system is a vital system that is essential for life. It is important to take care of your respiratory system by eating a healthy diet, exercising regularly, and getting enough sleep. You should also avoid smoking and secondhand smoke. If you have any concerns about your respiratory Health, you should see a doctor.
Here are some common respiratory problems:
Asthma: Asthma is a chronic condition that causes the airways to become inflamed and narrow. This can make it difficult to breathe.
Bronchitis: Bronchitis is an inflammation of the bronchial tubes. This can cause coughing, wheezing, and shortness of breath.
Pneumonia: Pneumonia is an infection of the lungs. This can cause fever, cough, and shortness of breath.
Emphysema: Emphysema is a chronic condition that causes the air sacs in the lungs to break down. This can make it difficult to breathe.
Chronic obstructive pulmonary disease (COPD): COPD is a group of lung diseases that includes emphysema and chronic bronchitis. COPD can make it difficult to breathe.
If you have any of these problems, it is important to see a doctor. They can help you manage your condition and prevent complications.
Circulatory System
What is the circulatory system? The circulatory system is an organ system that permits blood to circulate and transport nutrients (such as amino acids and electrolytes), oxygen, carbon dioxide, HORMONES, and blood cells to and from the cells in the body to nourish it and help to fight diseases, stabilize body temperature and pH, and to maintain homeostasis.
What are the parts of the circulatory system? The circulatory system is made up of the heart, blood vessels, and blood. The heart is a muscular organ that pumps blood throughout the body. The blood vessels are tubes that carry blood to and from the heart. The blood is a fluid that carries oxygen and nutrients to the cells and removes carbon dioxide and waste products from the cells.
What are the functions of the circulatory system? The functions of the circulatory system are to:
Transport blood to and from the cells in the body
Supply oxygen and nutrients to the cells
Remove carbon dioxide and waste products from the cells
Stabilize body temperature
Maintain homeostasis
What are some diseases of the circulatory system? Some diseases of the circulatory system include:
Heart disease
Stroke
High blood pressure
Atherosclerosis
Heart attack
Angina
Digestive System
What is the digestive system? The digestive system is an organ system that takes in food, digests it into smaller and smaller pieces, and absorbs nutrients into the bloodstream. The digestive system also eliminates waste products from the body.
What are the parts of the digestive system? The digestive system is made up of the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus. The mouth is where food is chewed and mixed with saliva. The esophagus is a muscular tube that carries food from the mouth to the stomach. The stomach is a muscular sac that churns and digests food. The small intestine is a long, coiled tube that absorbs nutrients from food. The large intestine is a shorter, wider tube that absorbs water from food and stores waste products. The rectum is a short tube that connects the large intestine to the anus. The anus is the opening through which waste products are eliminated from the body.
What are the functions of the digestive system? The functions of the digestive system are to:
Take in food
Digest food into smaller and smaller pieces
Absorb nutrients into the bloodstream
Eliminate waste products from the body
What are some diseases of the digestive system? Some diseases of the digestive system include:
What is the excretory system? The excretory system is an organ system that helps to maintain homeostasis by removing waste products from the body. The excretory system is made up of the kidneys, ureters, bladder, and urethra.
What are the functions of the excretory system? The functions of the excretory system are to:
Remove waste products from the blood
Regulate blood volume
Regulate blood pressure
Maintain acid-base balance
What are some diseases of the excretory system? Some diseases of the excretory system include:
What is the endocrine system? The endocrine system is an organ system that produces hormones that regulate many of the body’s functions, including Metabolism, Growth and development, tissue function, sexual function, Reproduction, sleep, and mood.
What are the parts of the endocrine system? The endocrine system is made up of glands that produce hormones. The glands of the endocrine system include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries, and testes.
What are the functions of the endocrine system? The functions of the endocrine system are to:
Regulate metabolism
Regulate growth and development
Regulate tissue function
Regulate sexual function
Regulate reproduction
Regulate sleep
Regulate mood
What are some diseases of the endocrine system? Some diseases of the endocrine system include:
Diabetes
Hyperthyroidism
Hypothyroidism
Cushing’s syndrome
Addison’s disease
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The respiratory system is responsible for: (a) exchanging oxygen and carbon dioxide (b) digesting food (c) circulating blood (d) excreting waste
The main organs of the respiratory system are: (a) the lungs, trachea, and bronchi (b) the heart, lungs, and blood vessels (c) the stomach, intestines, and liver (d) the brain, spinal cord, and nerves
The lungs are located in the: (a) chest (b) abdomen (c) head (d) neck
The trachea is also known as the: (a) windpipe (b) esophagus (c) pharynx (d) larynx
The bronchi are the tubes that branch off from the trachea and lead to the lungs. (a) True (b) False
The diaphragm is a muscle that separates the chest from the abdomen. (a) True (b) False
The ribs protect the lungs. (a) True (b) False
The alveoli are tiny air sacs in the lungs where gas exchange takes place. (a) True (b) False
The respiratory system is responsible for producing sound. (a) True (b) False
The respiratory system is responsible for regulating body temperature. (a) True (b) False
