The Respiratory System

Introduction

As you learned in the previous lesson, the respiratory system, also known as the pulmonary system, is intimately related to the cardiovascular system. The lungs supply oxygen to the blood and get rid of the carbon dioxide waste that the blood brings back to the heart. Without a properly functioning respiratory system, the cardiovascular system can't fulfill its own duties.

You may hear people refer to cardiopulmonary disease, or you may have heard of cardiopulmonary resuscitation (CPR). The respiratory and cardiovascular systems are so interdependent that they're sometimes considered one.

 

Respiration

The main function of the respiratory system is to supply oxygen to the body's cells and remove carbon dioxide. This requires coordination among all the organs of the respiratory and cardiovascular systems.

Respiration actually occurs on two separate levels, external and internal. External respiration is the type of respiration that you're already familiar with. When you breathe in, oxygen is brought into the lungs for the blood to pick up. When you breathe out, you blow out carbon dioxide that has moved from the blood to the lungs. 

 

Internal respiration, or cellular respiration, is parallel to the process involved in external respiration, but conducted at the cellular level. 

After blood passing through the lungs picks up oxygen, the heart pumps the blood to the rest of the body. The oxygen passes through the capillary walls and into the interstitial space, where the cells absorb the oxygen. The cells release carbon dioxide as a byproduct of metabolism. This carbon dioxide waste is picked up by the bloodstream and carried to the lungs for expiration. 

 

Anatomy and Physiology 

The respiratory system is comprised of the nose, pharynx, trachea, bronchi, lungs, and diaphragm. 

All of these organs work in coordination to maintain appropriate breathing to supply needed oxygen to the body and remove carbon dioxide via exhalation. 

Breathing can be done via the nose or mouth.

Nose: The nose has two main jobs. First, it provides our bodies with warm, filtered, and moistened oxygen. Second, it holds the olfactory nerve that enables us to smell. Although you can breathe through either your nose or mouth, the nose has features that are designed specifically for the act of inspiration, or the movement of air into the lungs.

The main advantage to breathing through the nose is that this passageway warms, moistens, and filters the air before it reaches the lungs. The external nares (or nostrils) are lined with mucous membranes and short, coarse hairs, or cilia, that filter out foreign particles such as dust. Another filter system is provided by the mucus, which also traps foreign particles. The mucus also provides another benefit: it kills some germs and stops the growth of others. 

Larynx: The larynx is located between the pharynx and trachea. It's also called the voice box because it houses the vocal chords. Vocal chords are tough bands of ligamentous tissue that vibrate to produce speech. The size and tightness of the vocal chords determine the sound of your voice. The space between the vocal chords is the glottis. The epiglottis, a leaf-shaped flap on top of the larynx, is responsible for sealing off the airway to the lungs when you swallow food or water. 

Bronchi: The branches of the bronchi (singular: bronchus) lead to the right and left lungs. After entering the lungs, the bronchi continue branching to smaller and smaller airways. The smallest ones are called bronchioles. The bronchioles open out into balloon-like pouches called alveoli (plural). Each alveolus (singular) expands and contracts with each inhalation or exhalation of air. Capillary beds contain the smallest blood vessels of the lungs, and they lie next to the thin tissue membranes of the alveoli. Here, oxygen from the alveoli combines with hemoglobin, a protein in the red blood cells, and is carried to all parts of the body. At the same time, carbon dioxide is transferred to the alveoli to be discarded by the body when you breathe out. Recall this transfer of the gases from the blood into lung spaces from the discussion of the cardiovascular system in the previous lesson.

Diaphragm: The diaphragm sits at the bottom of the lungs. Each breathe is initiated by the coordinated movement of the diaphragm, internal intercostal muscles, and external intercostal muscles.

Pharynx: The pharynx, or throat, is a multipurpose tube leading from the back of the nose and mouth. down to the trachea (windpipe) and to the esophagus. It allows air to reach your lungs and food to reach your stomach.

Trachea: The larynx leads to the trachea. The trachea is a long, hollow, smooth muscle tube that runs down the chest in front of the esophagus. The trachea separates the upper respiratory system (above the neck) from the lower respiratory system (below the neck). Those who are severely ill, undergoing surgery, or in an emergency situation can receive continuous, artificial ventilation by having a mechanical ventilator connected directly to the trachea—either through the mouth or by puncturing the skin in the neck area. The ventilator then pushes and pulls air in and out of the lungs to continue supplying oxygen and removing carbon dioxide. The trachea branches off into two main bronchi, and then the bronchi branch off to several bronchioles.

Lungs: Although the body consists of several paired structures that are identical, the lungs aren't exactly alike. The right lung is divided into three lobes, and the left lung is divided into two lobes. The left lung also has a notch in it to accommodate the heart, and the right lung accommodates the liver. Lungs are balloon-like organs that inflate and deflate to continue normal breathing. The lungs and the heart are protected by the chest wall.

 

Key Points

• The upper respiratory system includes the nose, pharynx, larynx, and trachea.
• The lower respiratory system includes bronchi, bronchioles, and lungs.
• Breathing is a coordinated effort of various respiratory system organs to receive oxygen and eliminate carbon dioxide.
• The cardiovascular system works in coordination with the respiratory system to receive oxygen into the blood and remove carbon dioxide out of the blood.
• Artificial breathing is done by a mechanical ventilator in emergency situations when a person is unable to breathe on his or her own.