The Respiratory System

Take a deep breath and dive into the swimming pool.  Now try to swim underwater to the other end of the pool and back without taking a second breath of air.  If you make it to the far end and manage to turn and head back, your heart will start to pound and before you return to your end of the pool your diaphragm begins to work up and down trying to bring in lifesaving air into your lungs.  You finally return where you surface and gasp for a big breath of fresh air.  Your chest heaves up and down as your body strives to replenish the depleted oxygen supply.

The average person can’t even hold their breath for 30 seconds.  Many athletes can hold their breath for a minute or longer.  However, free divers have been known to hold their breath for up to four minutes and longer.

That breath of air is so important.  Without it, our bodies quickly become oxygen depleted and stops operating.  Hence, the respiratory system is one of the most vital of all of the body’s systems.

Most people think of the respiratory system as just the lungs, however, there is a lot more to it than that.  In fact, the respiratory system is divided into the upper and lower systems.

I.  Upper Respiratory System – Consists of the mouth, nose, nasal cavity, pharynx and larynx.

A.  Mouth, Nose & Nasal Cavity – Other than the obvious function of being the openings used for the intake of air, they also serve to stop larger foreign objects from passing down in the rest of the respiratory system and they help to moisten the air as it is inhaled.

1.  Nasal Cavity – The nasal cavity contains a mucous that serves to warm the air as it passes over and add humidity to moisten the air before it travels on to the lungs.  Additionally, the mucous helps to capture tiny particles of foreign substances, which are subsequently passed back out through the nasal cavity in the form of a mucous secretion (snot).

2.  Goblet Cells – Located between the back of the nasal cavity and entrance to the pharynx is a series of goblet cells.  The goblet cells also secrete mucous.  This mucous helps to further filter and clean the air from any foreign particles that manage to pass by the nasal cavity’s cleaning system.  With the help of cilia on the goblet cells, any particles are pushed back up the passage where it can be eliminated through the mouth or nose.

B.  Pharynx – The pharynx is a muscular tube about 4-6 inches long that connects the mouth and nasal cavity to the esophagus and larynx.  The pharynx functions as part of the respiratory and digestive systems.  Its primary function in the respiratory system is to act as a passage way for the air to pass to and from the mouth and trachea.  The pharynx also plays a role in equalizing the air pressure in your middle ear.  The Eustachian tubes run from the middle ear down to the upper region of the pharynx.  The opening to the Eustachian tubes are opened and closed as needed to help balance the pressure of the middle ear.  When you change elevation, yawning or chewing gum or just moving the lower jaw around helps to ‘pop’ your ears by opening the Eustachian tubes and allowing the pressure to equalize.

C. Larynx – The larynx, also called the voice box, is located in the upper part of the neck between C3-C6 vertebra, just below where the pharynx branches off to the esophagus.  It connects the pharynx to the trachea.  The laryngeal structure contains three pairs and three single cartilages that function as part of our ability to speak.  As air passes across them they vibrate to produce sound.  The larynx functions also include swallowing, coughing, laughing, vomiting, hiccupping, postural adjustments, expulsive efforts, airway protection, and breathing.

II.  Lower Respiratory System – The lower respiratory system is composed of the trachea, bronchi, bronchioles, lungs, alveolar sacs and diaphragm.

A.  Trachea – The trachea, also known as the windpipe is a cartilage and muscular tube about 4-5 inches long and nearly an inch in diameter.  It connects to the larynx above and the bronchi below.  The main function of the trachea is the passage of air in and out of the lungs.

B.  Bronchi – The posterior end of the trachea branches into two smaller, but similarly constructed tubes known as the bronchi (bronchus – singular).  The bronchi enter the lungs where they continue to branch into smaller and smaller tubes.

C.  Bronchioles – The smaller branches of the bronchi are referred to as bronchioles.  Bronchioles continue to branch out and reduce in size until they are less than 1 mm in diameter.  Because bronchioles are so much smaller than the bronchi, they do not have the cartilage supports as do the bronchi and trachea.  The branching of the bronchi and bronchioles resembles the inverted branches of a tree.

D.  Alveolar Sacs – At the end of all the tiniest bronchioles are small hollow sacs called the alveolar sacs or alveoli.  The lining of the alveoli are very thin and laced with numerous capillaries.  It is here that gas exchange takes place as the blood releases carbon dioxide into the alveoli and collects as much oxygen as possible to be used by the rest of the body.  It is estimated there are 2.8-3.1 million alveoli in the lungs of a normal healthy person.

E.  Lungs – Each normal healthy person has two lungs.  The lungs are soft spongy organs that fill the bulk of the chest cavity along with the heart.  The right lung is usually larger and divided into three lobes and the left lung is smaller and only divided into 2 lobes.  The lungs contain the bronchi, bronchioles, alveolar sacs and miles of blood vessels and capillaries.  They are highly elastic as they expand and contract with the movement of the diaphragm.

F.  Diaphragm – The diaphragm is a large flat sheet-like muscle that stretches across the bottom of the rib cage.  It separates the thoracic cavity from the abdominal cavity.  When the diaphragm contracts, it causes the thoracic cavity and rib cage to expand, drawing air into the lungs.  Air is expelled from the lungs as the diaphragm relaxes.

Our bodies need oxygen to function and survive but many people don’t realize that oxygen only makes up between 20%-22% of the air we breath.  Nitrogen makes up from 76%-79% of the air.  The rest of the gases, under normal dry conditions, are argon, carbon dioxide, methane, nitrous oxide, ozone and water vapor.

Depending upon where one lives in the world, the water vapor in the air can significantly vary.  Most people are familiar with hearing about the relative humidity in their daily weather reports.  Relative humidity refers to the percentage of water vapor that the air can hold at a given temperature without causing it to precipitate out.  When the relative humidity is high, it means the air you are breathing contains a greater amount of water vapor than normal.  This can create difficulty breathing for some people with respiratory problems because the more water vapor you inhale, the less oxygen you take into your lungs.

The respiratory system is more delicate and easily damaged than most of the other organs found in the body cavity.  And it just so happens they are protected by the ribcage while the other organs in the abdomen, which are more resilient to injury are not so protected.

There are many illnesses and defects that can affect the function of the respiratory system.  They range from thing like the common cold and upper respiratory infections to more serious conditions like asthma, cystic fibrosis, chronic obstructive pulmonary disease (COPD) and cancer.

The respiratory system is far too complex to be the product of evolution.  I have no doubt that God designed the respiratory system when He created Adam and breathed that first breath into him as we read in Genesis 2:7:

Then the LORD God formed the man of dust from the ground and breathed into his nostrils the breath of life, and the man became a living creature.

Fearfully & Wonderfully Made (DVD)

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