Why must inhaled air be warmed

In each case the materials move from an area of high concentration to an area of lower concentration. Here the blood flows from the lungs to the body cells.

The alveoli take in the water and the carbon dioxide:. The alveoli are well suited for the important job they have. There are about ,, alveoli per lung!

That means there is a great surface area for gas exchange. Also, the walls of the alveoli as well as the capillaries are very thin so that the gases can diffuse readily.

When the blood picks up the diffused gases the gases are carried to their destinations. Carbon dioxide and water are carried in the plasma of the blood. The following chart compares the content of air before as it is inhaled Inspired Air and as it is exhaled Expired Air.

Inspired and Expired Air Comparison. Inspired Air. Expired Air. No real change. Reduced by about a quarter. Carbon Dioxide. Increased by about a hundred and five times. Water Vapour. Increased about five times. Note: a lot of water is lost from the body each day due to breathing. Inspiration or inhalation is said to be an active process because it involves muscle contraction. The diaphragm and intercostal muscles contract.

The contracting diaphragm flattens and stretches the elastic lungs downward. The contracting intercostals pull the ribcage up and out causing the elastic lungs to stretch. The expanding lungs cause the air inside to expand a gas will always fill its container. The expansion of air causes a drop in air pressure in the lungs.

The air in the lungs is at a lower pressure than the air outside. Air flows from higher to lower pressure so air flows into the lungs from outside. Expiration or exhalation is said to be a passive process because it does not involve muscle contraction.

The diaphragm and the intercostal muscles relax. The deforming force on the elastic lungs has been removed. The lungs recoil elastically reducing their volume a passive process. The volume of air in the lungs decreases causing an increase in the air pressure. The air in the lungs is at a higher pressure than the air outside.

Air flows from higher to lower pressure so the air flows out of the lungs. The elastic recoil of the lungs pulls up the adhering diaphragm and drags in the adhering ribcage. Breathing is normally under unconscious control. The major respiratory structures span the nasal cavity to the diaphragm. For the sake of convenience, we will divide the respiratory system in to the upper and lower respiratory tracts:.

The upper respiratory tract , can refer to the parts of the respiratory system lying above the sternal angle outside of the thorax , above the vocal folds, or above the cricoid cartilage. The tract consists of the nasal cavity and paranasal sinuses, the pharynx nasopharynx, oropharynx and laryngopharynx and sometimes includes the larynx.

Its primary function is to receive the air from the external environment and filter, warm, and humidify it before it reaches the delicate lungs where gas exchange will occur. Air enters through the nostrils of the nose and is partially filtered by the nose 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 further filters the air. The endothelial lining of the nasal cavity also contains tiny hairlike projections, called cilia. The cilia serve to transport dust and other foreign particles, trapped in mucous, to the back of the nasal cavity and to the pharynx.

There the mucus is either coughed out, or swallowed and digested by powerful stomach acids. After passing through the nasal cavity, the air flows down the pharynx to the larynx. The lower respiratory tract or lower airway is derived from the developing foregut and consists of the trachea, bronchi primary, secondary and tertiary , bronchioles including terminal and respiratory , and lungs including alveoli.

It also sometimes includes the larynx, which we have done here. This is where gas exchange actually takes place. The larynx plural larynges , colloquially known as the voice box, is an organ in our neck involved in protection of the trachea and sound production. The larynx houses the vocal cords, and is situated just below where the tract of the pharynx splits into the trachea and the esophagus. The larynx contains two important structures: the epiglottis and the vocal cords.

The epiglottis is a flap of cartilage located at the opening to the larynx. During swallowing, the larynx at the epiglottis and at the glottis closes to prevent swallowed material from entering the lungs; the larynx is also pulled upwards to assist this process. Stimulation of the larynx by ingested matter produces a strong cough reflex to protect the lungs. Note: choking occurs when the epiglottis fails to cover the trachea, and food becomes lodged in our windpipe.

The vocal cords consist of two folds of connective tissue that stretch and vibrate when air passes through them, causing vocalization. The length the vocal cords are stretched determines what pitch the sound will have. The strength of expiration from the lungs also contributes to the loudness of the sound. Our ability to have some voluntary control over the respiratory system enables us to sing and to speak. In order for the larynx to function and produce sound, we need air. Air travels from the larynx to the trachea Figure 1.

The lungs also contain elastic tissues that allow them to inflate and deflate without losing shape and are covered by a thin lining called the pleura PLUR-uh. The chest cavity, or thorax THOR-aks , is the airtight box that houses the bronchial tree, lungs, heart, and other structures. The top and sides of the thorax are formed by the ribs and attached muscles, and the bottom is formed by a large muscle called the diaphragm DYE-uh-fram.

The chest walls form a protective cage around the lungs and other contents of the chest cavity. The cells in our bodies need oxygen to stay alive. Carbon dioxide is made in our bodies as cells do their jobs. The lungs and respiratory system allow oxygen in the air to be taken into the body, while also letting the body get rid of carbon dioxide in the air breathed out. When you breathe in, the diaphragm moves downward toward the abdomen, and the rib muscles pull the ribs upward and outward.

This makes the chest cavity bigger and pulls air through the nose or mouth into the lungs. In exhalation, the diaphragm moves upward and the chest wall muscles relax, causing the chest cavity to get smaller and push air out of respiratory system through the nose or mouth.

Every few seconds, with each inhalation, air fills a large portion of the millions of alveoli. In a process called diffusion, oxygen moves from the alveoli to the blood through the capillaries tiny blood vessels lining the alveolar walls. Once in the bloodstream, oxygen gets picked up by the hemoglobin in red blood cells. This oxygen-rich blood then flows back to the heart, which pumps it through the arteries to oxygen-hungry tissues throughout the body.