Respiratory System

Otorhinolaryngology - branch of medicine that deals with the ears, nose and throat

Pulmonologist – specialist in the diagnosis and treatment of lung disease

Functions of Respiratory System

1. Respiration-exchange of gases within the body: O2

& CO2

2. Regulates blood pH3. Contains receptors for smell4. Filters inspired air5. Sound production

Stages of Respiration Pulmonary Ventilation (breathing)

› Gas exchange between atmosphere and the lungs

External Respiration› Gas exchange between lungs & pulmonary

capillaries (pulmonary capillary blood gains O2, loses CO2)

Internal Respiration› Gas exchange between systemic capillaries &

body tissue cells (systemic capillary blood gains CO2, loses O2)

Structures of the Respiratory System

1. The Nose› Warms, moistens & filters air› Detects odors› Modifies speech vibrations› Conchae & meatuses

Increase surface area Trap exhaled water droplets during

exhalation Prevents dehydration

Nasal Membranes

Goblet cells secrete mucus › Moistens air› Traps debris

Cilia- tiny hairs that trap debris Blood capillaries – warm inhaled air

Sneezing

Stimulus irritates nasal mucosa Spasmodic contraction of respiratory

muscles occurs Air focefully expelled out of nose &

mouth Sneezes can travel up to 200 mph Sputum can be spread 2-3 meters

2. The Pharynx› Part of both GI Tract & Respiratory Tract› Passageway for both food and air› Resonating chamber for speech sounds› Houses the tonsils› 3 Regions of Pharynx

Nasopharynx – 5 openings (internal nares, eustacian tubes and into oropharynx)

Oropharynx – respiratory & digestive function Laryngopharynx – contains the epiglottis,

which is a flap of cartilage that covers the glottis during swallowing. Glottis – opening to the larynx/trachea

3. The Larynx› “Voice box”› Connects laryngopharynx with the trachea› Lies anterior to C4 – C6 Vertebrae

› Composed of cartilage› Air passing across vocal folds & vibration

of folds creates sound› Pharynx, mouth, nasal cavity: act as

resonating chambers to give sound human quality

› Muscles of face, mouth & tongue allow for enunciation

Pitch of voice is controlled by tension on the vocal cords› More tension = higher pitch› Less tension = lower pitch

Men have longer, thicker vocal cords that vibrate more slowly which creates a lower pitch› This is due to testosterone

4. The Trachea› Windpipe› 12 cm in length; 2.5 cm in diameter› Anterior to the esophagus› Contains 16-20 arcs (rings) of cartilage –

helps to prevent collapse during breathing› Divides at carina (T-5) into right and left

primary bronchi

Respiratory TractNose

Nasal CavityPharynx

Primary BronchiSecondary Bronchi

Lungs Tertiary BronchiBronchioles

Terminal BronchiolesRespiratory Bronchioles

Alveolar DuctsAlveoli

The Lungs

Right lung: 3 lobes Left lung: 2 lobes Pleural membrane - (2 layers) covers

each lung Pleural cavity - space between layers;

contains lubricating fluid Hilus - region where primary bronchi,

blood and lymph vessels, and nerves enter or exit the lung

Alveoli Tiny air sacs 300 million Very thin tissue: 0.5 μm Diffusion of gases occurs here (exchange

of CO2 and O2 between lungs & blood) Contains macrophages, which are cells

that remove dust/debris Alveoli secrete fluid for moisture

› Contains surfactant – lowers the surface tension of alveolar fluid to prevent alveolar collapse

Blood Supply to the Lungs Lungs receive blood from two sets of

arteries› Pulmonary Arteries – bring deoxygenated

blood (O2 poor blood) to the lungs from the body

› Bronchial Arteries – (branch from the aorta) bring oxygenated blood (O2 rich blood) to the lungs from the heart

Pulmonary Veins – bring O2 rich blood to the heart from the lungs

Pulmonary Ventilation (Breathing)

Gases are exchanged between atmosphere & lung alveoli

O2 in or CO2 out Due to differences in pressure when

respiratory muscles contract & relax Inspiration – breathing in Expiration – breathing out Boyle’s Law explains how this occurs

Boyle’s Law

The pressure of a gas varies inversely with the volume› If pressure goes up, volume goes down› If pressure goes down, volume goes up

Application of Boyle’s LawInhalation

Diaphragm contracts (flattens), lungs expand

Volume of lungs increases Pressure of lungs decreases Air moves into lungs

Inhalation is an ACTIVE process: it requires muscle contraction & ATP

After Inhalation Occurs….Exhalation

Diaphragm relaxes – returns to “dome” shape

Pressure in lungs increases Air moves out of lungs (volume of

lungs decrease)

Exhalation is a PASSIVE process: it does not require muscle contraction & ATP

External Respiration

Exchange of O2 and CO2 between alveoli and blood in pulmonary capillaries

Occurs by passive diffusion Controlled by two gas laws:

› Dalton’s Law› Henry’s Law

Dalton’s Law

Each gas in a mixture of gases exerts its own pressure as if all the other gases were not present

This is its partial pressure (Px)› Ex.; Atmospheric air is made up of N2, O2,

H2O, CO2 and other gases

› PN2 + PO2

+ PH2O + PCO2

+ Pother = Ptotal

› Ptotal = 760 mm Hg

How does Dalton’s Law relate to respiration??

The gases will diffuse from the area of higher pressure to the area of lower pressure› Ex.; if O2 is high in alveoli & low in blood, O2

will diffuse across the alveoli and into the blood

› **it determines the movement of O2 between: Atmosphere & lungs Lungs & blood Blood & body cells

Henry’s Law

the quantity of a gas that will dissolve in a liquid is proportional to the partial pressure of the gas and its solubility coefficient

If a gas has high partial pressure, and a high solubility coefficient = high gas content in solution

How does Henry’s Law relate to Respiration??

Oxygen crosses into blood because:› PO2

(alveolar air) = 105 mm Hg

› PO2(deoxygenated blood in pulmonary

capillaries) = 40 mm Hg› …so O2 moves from alveoli to blood

Carbon dioxide crosses into alveoli because:› PCO2 (deoxygenated blood in pulmonary

capillaries) = 45 mm Hg

› PCO2(alveolar air) = 40 mm Hg

› …so CO2 moves from blood to alveoli

Rate of Gas Exchange

Rate of gas exchange depends on› 1. partial pressure difference of gases› 2. surface area for gas exchange

Bigger the area, the higher the rate of exchange

› 3. diffusion distance Smaller the distance, the higher the rate of

exchange

Internal Respiration

Exchange of gases at the cellular level (Dalton’s Law applies)

O2 leaves blood and diffuses into cell

CO2 leaves cells and diffuses into blood

Oxygen Transport

O2 does not dissolve well in water

Transportation requires hemoglobin

Hemoglobin – an iron-rich protein that turns bright red when combined with O2

Oxyhemoglobin – 1 hemoglobin + 4 O2

Carbon Dioxide Transport

Dissolves well in water Most found in blood as bicarbonate ions Blood detects this & transports it to

lungs to be exhaled Controls rate of breathing:

› High ion level – high respiratory rate› Low ion level – low respiratory rate

Medulla oblongata – part of brain that controls the respiratory rate

Lung Volumes

Adult – 12 breaths/min Tidal volume – volume of one breath ~

500ml Spirometer – device used to measure

volume of respiration Residual volume – air that remains in

lungs after maximum exhalation (~1200 ml)› Prevents lung collapse› Can’t be measured with spirometer