The function of the respiratory system is to deliver air to the lungs. Oxygen in the air diffuses out of the lungs and into the blood, while carbon dioxide diffuses in the opposite direction, out of the blood and into the lungs. Respiration includes the following processes:

• Pulmonary ventilation is the process of breathing—inspiration (inhaling air) and expiration (exhaling air).

• External respiration is the process of gas exchange between the lungs and the blood. Oxygen diffuses into the blood, while CO₂ diffuses from the blood into the lungs.

• Gas transport, carried out by the cardiovascular system, is the process of distributing the oxygen throughout the body and collecting CO₂ and returning it to the lungs.

• Internal respiration is the process of gas exchange between the blood, the interstitial fluids (fluids surrounding the cells), and the cells. Inside the cell, cellular respiration generates energy (ATP), using O₂ and glucose and producing waste CO₂.

1. Pulmonary ventilation is the movement of air into and out of the lungs (breathing).
2. External respiration is the exchange of O₂ (loading) and CO₂ (unloading) between blood and alveoli (air sacs).
3. Transport of respiratory gases between lungs and tissues.
4. Internal respiration is gas exchange between blood and tissue cells.

The difference between the respiratory and conducting zones is their function: the conducting zone transports the air into and out of the lungs; the respiratory zone allows gas exchange between the lungs and the blood.

the main function of the nose is to help us breathe. When we inhale through our nose, air passes through our nostrils into a short and narrow area known as the nasal passage that leads to the back of the throat (pharynx), and on down into the windpipe and lungs. From there it continues throughout the respiratory system.

It helps filter air using nasal hairs so particles do not reach our lungs.

We are able to smell as the air flows through the nose and over structures called turbinates in the nasal cavity. The turbinates slow the air and direct it toward the olfactory epithelium, where odor molecules reach olfactory receptor neurons that send electrical impulses to our brain. 

the biological role of the sinuses is debated, but a number of possible functions have been proposed:

• Decreasing the relative weight of the front of the skull, and especially the bones of the face.
• Increasing resonance of the voice.
• Providing a buffer against blows to the face.
• Insulating sensitive structures like dental roots and eyes from rapid temperature fluctuations in the nasal cavity.
• Humidifying and heating of inhaled air because of slow air turnover in this region.

The main function of pharynx is to act as a common passage for both food and air. Thus the pharynx should channel food without choking. Pharynx plays a major role in the first phase of swallowing. As the food bolus is pushed by the tongue into the pharynx, it pushes the food down by muscular contraction down the esophagus.

The other important function of Pharynx is to equalize pressure that gets built near the ear drums. This is made possible by the two eustachian tubes (one from each ear) that connect the middle ear with pharynx.

Nasophraynx: Solely for air.

Oropharynx & Laryngopharynx: Passage for food and air

The main function is to prevent choking. 

Secondary is voice production.

What is the value of cilia & mucus in the respiratory system passages?

cilia are tiny hairs that protect the nasal passageways and other parts of the respiratory tract, filtering out dust and other particles that enter the nose with the breathed air. As air is inhaled, the cilia move back and forth, pushing any foreign matter (like dust) either toward the nostrils, where it is blown out, or toward the pharynx, where it travels through the digestive system and out with the rest of the body's waste.

In the lungs, mucus functions to smooth the airways linings and traps foreign substances that invade the respiratory system. When foreign substances make their way into the lungs they will be coughed out instantly.

How is sound (your voice) produced?

Connection tissue called hyaline cartilage forms the larynx. 

The function of hyaline cartilage is to provide flexible support. It has great tensile strength (due to the collagen) and is highly resistant to pressure (due to the ground substance)

Even though they may look alike in pictures or diagrams, our lungs have a difference, and that is in its number of lobes. The left lung is composed of only two lobes, separated midway by an interlobular fissure. Basically, these lobes are named according to their position in reference to the fissure, thus named superior and inferior lobes.

The right lung, on the other hand, has three lobes still separated by a fissure. It is comprised of a superior lobe, middle lobe, and inferior lobe. This makes it different from the left lung.

The anatomical reason for the difference between the left and right lungs is to leave room in the chest for the heart, while the actual developmental reason is genetic cues set up in the embryo before the lungs form that tell the left lung to branch less and grow less than the right.

Surfactant reduces surface tension. Without surfactant, the wet surfaces of the alveoli in your lungs would stick together and your lungs would not be able to expand - so, you would not be able to breath.
 

Transpulmonary pressure is a term used to describe the difference between the alveolar pressure and the intrapleural pressure in the lungs. During human ventilation, air flows because of pressure gradients.

760 mm Hg

–756 mm Hg

= 4 mm Hg = value

756 mm Hg

(–4 mm Hg) = value

760 mm Hg

(0 mm Hg) = value

1. Airway Resistance

(•Friction is major source of resistance to gas flow)

2. Alveolar surface tension

(•Surface tension – attraction of liquid molecules to one another

What is the relationship between flow, pressure, & resistance?

            Amount of air inhaled or

           exhaled with each breath

            under resting conditions

average male AND female  = 500 ml

dead space is air that is inhaled by the body in breathing, but does not take part in gas exchange. Not all the air in each breath is able to be used for the exchange of oxygen and carbon dioxide. About a third of every resting breath has no change in O₂ and CO₂ levels. In adults, it is usually in the range of 150 mL.^[a]

Because of dead space, taking deep breaths more slowly (e.g. ten 500 mL breaths per minute) is more effective than taking shallow breaths quickly (e.g. twenty 250 mL breaths per minute). Although the amount of gas per minute is the same (5 L/min), a large proportion of the shallow breaths is dead space, and does not allow oxygen to get into the blood.

Dead space can be enlarged (and better envisaged) by breathing into a long tube. Even though one end of the tube is open to the air, when one inhales, it is mostly the carbon dioxide from expiration. Using a snorkel increases a diver's dead space in the airways.

External respiration is the exchange of gases between the alveoli and lung capillaries. Oxygen diffuses from the alveoli into the blood, while carbon dioxide moves from the blood in the alveoli. Internal respiration, in contrast, is the exchange of gases in body tissues.

External respiration is the exchange if oxygen and carbon dioxide between the blood and air in the lungs, and internal resparation is the exchange of gases between blood cells of the body.

matching of alveolar ventilation & pulmonary blood perfusion.

'coupling between amount of gasreaching alveoli & blood flow in pulmonary capillaries; local autoregulation'