The Respiratory System is crucial to every human being. Without it, we would certainly cease to live external of the womb. Let us start by acquisition a look in ~ the framework of the respiratory tract system and how an important it is come life. During inhalation or exhalation waiting is pulled towards or far from the lungs, by numerous cavities, tubes, and openings.

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The organs of the respiratory device make certain that oxygen enters ours bodies and carbon dioxide pipeline our bodies.

The respiratory tract tract is the course of air from the nose to the lungs. It is divided into 2 sections: Upper respiratory tract Tract and the Lower respiratory tract Tract. Contained in the upper respiratory tract are the Nostrils, Nasal Cavities, Pharynx, Epiglottis, and also the Larynx. The lower respiratory tract is composed of the Trachea, Bronchi, Bronchioles, and the Lungs.

As wait moves follow me the respiratory tract it is warmed, moistened and filtered.

Figure 1. Click because that a larger image. The major respiratory structures expectations the sleep cavity to the diaphragm.


There are 4 processes that respiration. Castle are:

Breather or ventilationExternal Respiration, which is the exchange that gases (oxygen and also carbon dioxide) between inhaled air and the blood.Internal Respiration, which is the exchange that gases in between the blood and tissue fluids.Cellular Respiration

In addition to these key processes, the respiratory system serves for:

Regulation that Blood pH, which occurs in coordination with the kidneys,Defense against microbesControl of body temperature due to loss that evaporate during expiration

Respiratory System: Upper and Lower respiratory tract Tracts

For the services of convenience, we will divide the respiratory mechanism in come the upper and lower respiratory tract tracts:

Upper respiratory tract Tract

The upper respiratory tract, can refer to the parts of the respiratory device lying over the sternal angle (outside that the thorax), above the vocal folds, or over the cricoid cartilage. The tract consists of the nasal cavity and also paranasal sinuses, the pharynx (nasopharynx, oropharynx and laryngopharynx) and sometimes contains the larynx. That primary duty is to obtain the wait from the outside environment and also filter, warm, and also humidify it before it will the fragile lungs whereby gas exchange will occur.

Air enters v the nostrils of the nose and is partly filtered by the sleep hairs, then flows into the nasal cavity. The nasal cavity is lined with epithelial tissue, containing blood vessels, which help warm the air; and secrete mucous, which additional filters the air. The endothelial lining the the nasal cavity additionally contains small hairlike projections, referred to as cilia. The cilia offer to transport dust and other foreign particles, trapped in mucous, to the ago of the sleep cavity and also to the pharynx. There the rubber is either coughed out, or swallowed and digested by powerful stomach acids. After passing with the nasal cavity, the waiting flows down the pharynx to the larynx.

Lower respiratory Tract

The reduced respiratory tract or reduced airway is acquired from the occurring foregut and consists that the trachea, bronchi (primary, secondary and tertiary), bronchioles (including terminal and also respiratory), and lungs (including alveoli). It additionally sometimes includes the larynx, i beg your pardon we have done here. This is wherein gas exchange actually takes place.


The larynx (plural larynges), colloquially well-known as the voice box, is an organ in our neck involved in protection of the trachea and sound production. The larynx residences the vocal cords, and also is positioned just below where the street of the pharynx splits into the trachea and the esophagus. The larynx includes two crucial structures: the epiglottis and the vocal cords.

The epiglottis is a flap that cartilage located at the opened to the larynx. Throughout swallowing, the larynx (at the epiglottis and also at the glottis) close the door to protect against swallowed product from beginning the lungs; the larynx is additionally pulled upwards to help this process. Stimulation of the larynx through ingested issue produces a strong cough reflex to protect the lungs. Note: choke occurs once the epiglottis falls short to sheathe the trachea, and also food i do not care lodged in ours windpipe.

The vocal cords consist of of 2 folds that connective tissue that stretch and also vibrate as soon as air passes through them, causing vocalization. The length the vocal cords are stretched identify what key the sound will certainly have. The toughness of expiration native the lungs also contributes come the loudness that the sound. Our capability to have some voluntary control over the respiratory tract system allows us to sing and also to speak. In order because that the larynx to function and produce sound, we require air. That is why we can’t talk when we’re swallowing.


Air travel from the larynx come the trachea (Figure 1). The trachea is a tubular structure consisting of dense connective tissue and rings that hyaline cartilage. The trachea is lined with ciliated pseudostratified columnar epithelium v goblet cells. The epithelium move substances towards the larynx and esophagus for swallowing. The cartilage rings carry out not completely encircle the trachea but are open up posteriorly. The posterior section of the trachea includes a ligament and also smooth muscle recognized as the trachealis muscle. The trachealis muscle deserve to contract and constrict the trachea. The trachea usually ends at about the level that the 5th thoracic segment. The inferior end of the trachea divides right into right and also left bronchi in ~ an area recognized as the carina. The carina is the critical tracheal cartilage and forms a cartilage division between the 2 bronchi.

Bronchial Tree

The trachea ends at the carina and divides into two tubular structures dubbed the right and left main bronchi. The bronchi then divide right into smaller branches called secondary or lobar bronchi and also then even smaller branches dubbed tertiary or segmental bronchi. The framework of the bronchi is similar to the trachea through incomplete cartilage rings and smooth muscle. Together the bronchi obtain smaller there is less cartilage and much more smooth muscle until getting to the tertiary bronchi that consists entirely of smooth muscle. The smooth muscle deserve to constrict the bronchi and also impede wait passage. The bronchi continue to branch and type small bronchioles which division to type terminal bronchioles. The terminal bronchioles divide to kind respiratory bronchioles that connect with alveolar ducts. The alveolar ducts give rise come alveoli. Alveoli are thought about the practical unit the the lung and consist the Dr. Bruce Forciea page 560 small hollow locations for gas exchange. The alveolar ducts and alveoli room lined with straightforward squamous epithelium that allows for gas exchange. The cell of the simple squamous epithelium room called type I pneumocytes. The alveoli additionally contain various other cells known as form II pneumocytes. This cells secrete a substance recognized as surfactant that helps come decrease the surface tension in the alveoli. The lungs contain around 300 million alveoli.

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The Lungs

The lungs are two cone shaped structures residing in the thoracic cavity. The inferior portion of every lung reaches to the diaphragm. The superior section extends around one inch above each clavicle. The right lung includes three lobes (superior, middle and also inferior) and also is bigger than the left lung which contains two lobes (superior and also inferior). The lobes are separated through fissures. The ideal lung includes a horizontal and also oblique fissure if the left lung only includes an tilt fissure. The medial surface of each lung contains an area recognized as the hilum where vessels enter and exit. The left lung also contains the cardiac notch i m sorry is one indentation for the heart. The lungs space surrounded by two pleural membranes. The surface ar of each lung consists of a visceral pleural membrane that very closely adheres to the lung’s surface. Lining the internal of the thoracic wall is the parietal pleural membrane. Both are serous membranes. A liquid known as pleural liquid is secreted by each membrane the reduces friction and also helps to organize the membranes together.