Human Anatomy and Physiology: The Respiratory System and Respiratory Diseases

The resipratory system is one of the most important systems in our body, responsible for obtaining oxygen for all the cells in our body. It gives this oxygen to the blood and the circulatory system then transports it to all your cells.

Path of air in the Respiratory System

The respiratory system consisits of many different parts. The parts of the respiratory system are as follows:

Nose and Nasal Cavity

The nose is the opening responsible for pulling the air outside of your body into it. During breathing, our enters the nose by passing through the nostrils. The interior of the nose consists of the nasal cavity. The walls of the nasal cavity are lines with thin walled veins that warm the air as it flows past. However, the thin walls of these veins as well as their location make nosebleeds common. Mucous here also moistens the air and traps incoming bacteria and debris. Enzymes in the mucus then destroy these bacteria. The nasal cavity is surrounded by a ring of paranasal sinuses.

Pharynx (Throat)

The pharynx is a muscular passageway that is about 13 cm long. It is more commonly called the throat. The pharynx serves as a passageway for food and air. Air enters from the nasal cavity into the nasopharynx and then descends through the oropharynx and then the laryngopharynx. From there, air then enters the larynx. Food enters the mouth and then travels along with air down the oropharynx and laryngopharynx. However, instead of entering the larynx, food is directed to the esophagus. Clusters of lymphatic tissue called tonsils are also found in the pharynx. The pharyngeal tonsil is found high up in the nasopharynx. The palatine tonsils are in the oropharynx at the end of the soft palate, as are the lingual tonsils which are at the base of the tongue. The role of the tonsils is to stop germs from entering the body through the mouth or the nose.

Larynx (Voice Box)

The larynx routes air and food into the proper channels and also plays a role in speech. It is located inferior to the pharynx and is formed by eight rigid hyaline cartilages and a spoon-like flap of cartilage known as the epiglottis. The largest of the eight hyaline cartilages is called the thyroid cartilage or, as its more commonly known, the Adam’s apple. The epiglottis protects the opening of the larynx. When we are not swallowing, the epiglottis does not restrict passage of air into the lower respiratory passages. However, when we swallow food or fluids, the larynx is pulled upwards and the epiglottis tips, forming a lid over the opening of the larynx. This prevents food or fluid from entering the larynx. If anything other than air enters the larynx, a cough reflex is triggered to try and remove the substance. Part of the mucous membrane of the larynx forms folds called vocal folds, or true vocal cords, that vibrate with expelled air. The ability of the vocal folds to vibrate allows us to speak.

Trachea (Windpipe)

Once air enters the trachea, it travels down to the level of the fifth thoracic vertebrae which is around the mid-chest. The trachea is fairly rigid as its walls are reinforced by C-shaped rings of hyaline cartilage. These rings serve two main purposes. the open parts of the rings touch the esophogus and allow it to expand when we swallow a large piece of food. The solid portions or the ring support the trachea walls and keep it open, in spite of the pressure changes that occur during breathing.

Primary Bronchi

The right and left main (primary) bronchi are formed by the division of the trachea. Each main bronchus runs diagonally until it reaches the medial depression of the lung on its side. The right main bronchus is wider shorter and straighter than the left and, therefore, is a more common site for foreign objects to become stuck. By the time air reaches our lungs, it is warm, cleansed of most impurities and humidified.

Lungs

The lungs are large organs that occupy most of the thoracic cavity. The narrow upper area of each lung is called the apex. The broad lung area resting on the diaphragm is the base. Each lung is divided into lobes. The left lung has two lobes and the right lung has three. The surface of each lung is covered with a smooth tissue membrane called the pulmonary pleura. The walls of the thoracic cavity are ilnes by the parietal pleura. The pleural membranes produce pleural fluid, a slippery secretion that allows he lungs to glide over the thorax wall easily during breathing movements, also causing the pleural layers to cling to each other. The pleurae can slide easily from side to side across one another but they strongly resist being pulled apart, meaning the lungs are held tightly to the thorax wall. The pleural membranes sticking together is critical for breathing.

After entering the lungs, the main bronchi divide into smaller and smaller branches of bronchi, finally ending in bronchioles. The network formed by this branching and branching is often called the bronchial tree or respiratory tree. The bronchioles then lead into respiratory zone structures that are even smaller channels that eventually end in alveoli. The respiratory zone is the site of gas exchange and consists of respiratory bronchioles, alveolar ducts, alveolar sacs and alveoli. All other respiratory passages are called conducting zone structures. In the lung, there are millions of clustered alveoli that resemble grapes. The walls of the alveoli are primarily made of a single, thing layer of squamous epithelial cells.

Common Illnesses and Disorders

Asthma

Asthma is an inflammatory disease that involves the pathways for air to the lung. It is the most common chronic condition in children in the US. One in every twelve children has asthma. Asthma causes the lining of your airways to swell and the muscles surrounding them to also tighten. The airways then fill with mucus, meaning even less air can pass through. These conditions are what cause an asthma attack, coughing and a tightening feeling in the chest.

Some of the most common symptoms of asthma are:

• Shortness of breath
• Tightness in chest
• Coughing
• Wheezing
• Fatigue

There are a few different types of asthma and the symptoms vary depending on the type of asthma. Some of the types of asthma are: allergic asthma, nonallergic asthma, exercise-induced asthma (or EIA), nocturnal asthma and asprin-induced asthma.

Allergic asthma is very common and is triggered by allegens such as certain foods, dust and pollen. Allergic asthma is often seasonal as it usually is paired with seasonal allergens. Nonallergic asthma is caused by irritants in the air that are not allergens. Some examples are burning wood, perfumes, cigarette smoke and air fresheners.

Exercise-induced asthma is trigerred by exercise and usually starts affecting the person within a few moments of starting exercise as well as around 10 minutes after any form of physical activity. An estimated 90% of people that have other forms of asthma also experience EIA but not everyone with EIA experience other forms of asthma.

Nocturnal asthma is a type of asthma in which the symptoms worsen considerably at night. There are many possible triggers, but the primary ones include dust mites and heartburn.Asprin induced asthma is triggered by taking asprins or other similar anti-inflammatory drugs such as Advil or Aleve.

Cystic Fibrosis

Cystic fibrosis (CF) is a rare genetic disease affecting over 4,200 Canadians. Cystic fibrosis is caused by a change, or mutation, in a gene called CFTR. To have cystic fibrosis, you must get a copy of this mutated gene from both parents. CTFR controls the flow of salt and fluids in and out of your cells. When CFTR doesn’t work the way it should, a sticky mucus builds up in your body.

Exocrine glands normally produce thin, slippery secretions such as mucus, sweat, tears and digestive juices. With cystic fibrosis, the mucus is thick and sticky. This unusually thick mucus interferes with the normal functioning of certain body systems. In the lungs, a build-up of thick mucous causes severe respiratory problems.

CF has a number of effects/symptoms that patients have to deal with. Some of these include:

• Recurring chest infections
• Wheezing, coughing, shortness of breath and damage to the airways
• Difficulty putting on weight and growing
• Increased risk of other major diseases

There is no cure or any way to prevent cystic fibrosis but treatment can ease symptoms, reduce complications and improve quality of life. Close monitoring and early intervention helps to slow the progression of cystic fibrosis, leading to a longer life.

Some treatment methods include:

• Mucus-thinning drugs
• Inhaled medications called bronchodilators that help keep your airways open
• Medications that target gene mutations (CTFR Modulators)
• Gene therapy (currently being developed)

Pneumonia

Pneumonia is an infection (typically caused by bacteria, fungi and viruses) that inflames the air sacs in the lungs. The air sacs could even fill with fluid causing fever, coughing with phlegm and difficulty breathing. In extreme cases, pneumonia can even be life threatening. It is more serious for those over 65, infants and young children and those with weakened immune systems.

The symptoms of pneumonia vary depending on the severity of the case. Some of the possible symptoms are:

• Phlegm producing cough
• Fatigue
• Chest pains
• Nausea
• Shortness of breath
• Vomiting
• Fever

Pneumonia is caused by a variety of germs but the most common are bacteria and viruses in the air. While the body will usually prevent these germs from reaching you lungs, they are occasionally unable to stop them. Pneumonia is classified based on how it was caused.

Bacterial pneumonia can occur on its own but can also occur shortly after you have recovered from the flu or from a cold. It also may sometimes onlya ffect one lobe of the lung. In these cases, it is called lobar pneumonia.

Viral pneumonia is a possible side effect of some cold and flu causing viruses. Viral pneumonia is typically fairly mild but it can still become severe in certain cases. Believe it or not, COVID-19 can even cause pneumonia.

Pneumonia caused by fungi is typically found in those with existing health problems or weakened immune systems. The fungi that can cause this type of pneumonia is often found in bird droppings or soil. However, this can vary depending on location.

Chronic Obstructive Pulmonary Disease (COPD)

Chronic obstructive pulmonary disease (COPD) is another inflammatory lung disease. This disease causes obstructed airflow from the lungs. This disease is typically caused by long term exposure to gasses, specifically cigarette smoke. COPD also gives you increased risk for numerous other diseases such as lung cancer and heart disease. While COPD is a disease that gets worse over time, it is treatable. When controlled properly, COPD patients can achieve a good quality of life.

Symptoms of COPD typically don’t occur lung damage has reached a serious level. These symptoms can worsen over time if not managed. Some potential symptoms include:

• Chest tightness
• Wheezing
• Lack of energy
• Coughing that may produce mucus
• Shortness of breath

COPD patients can experience episodes during which their symptoms become significantly worse for a period of time.

The lungs heavily rely on the natural elasticity of the bronchial tubes and air sacs to force air out of your body. Those with COPD have their bronchial tubes lose some of that elasticity and they could then over-expand, causing some air to remain trapped in your lungs when you exhale.

There are two diseases that are common causes of COPD. These are emphysema and chronic bronchitis.

Emphysema is a disease that destroys the walls and the elastic fibres of the alveoli. This causes small airways to collapse when you exhale, affecting the airflow to your lungs.

Chronic bronchitis is a condition in which your bronchial tubes become narrow and inflamed while also causing your lungs to create more mucus. This mucus then blocks your already narrowed tubes, causing you to cough to try and clear the blockage.