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Carbon Dioxide

waste product the body must get rid of

Respiratory System

action of supplying the body with oxygen and disposing of carbon dioxide is the major function

4 Processes of the Respiratory System

1.pulmonary ventilation
2. external respiration
3. respiratory gas transport
4. internal respiration

Pulmonary Ventilation

movement of air into and out of the lungs
-allows the gases in the lungs to be continuously refreshed
-commonly called breathing

External Respiration

movement of oxygen from the lungs to the blood and of carbon dioxide from the blood to the lungs

Respiratory Gas Transport

transport of oxygen from the lungs to the tissue cells and of carbon dioxide from the tissue cells

Internal Respiration

movement of oxygen from blood to the cells and of carbon dioxide from cells to blood

Path of Air Flow

nostrils/mouth, pharynx (upper respiratory), larynx, trachea, primary bronchis, bronchioles, alveolar ducts, alveolar sac, alveoli

Function of Nose

-moistens and warms entering air
-filters and cleans inspired air
-serves as resonating chamber for speech
-houses the olfactory receptors

Function of Larynx

provide patent airway and contains vocal cords

hyaline cartilage

u-shaped rings prevent trachea from collapsing


create tracheal walls


catches any inhaled particles and cilia move it out toward the esophagus where it is swallowed or spit out

Heimlich Manuever

rapidly squeezing out the air in the victim's lungs to pop out the obstruction

Primary Bronchi

goes to each lung, subdivides into secondary bronchi which supply one lung lobe

Secondary Bronchi

supply one lung lobe, divide into tertiary bronchi

respiratory tree

divisions of the bronchials

difference of bronchioles and bronchi

-bronchioles have no supportive cartilage
-epithelium pseudostratified columnar to simple columnar to simple cubodial
-no cilia or mucus producing cells(removed by macrophages)
-more smooth muscle

smooth muscle in bronchioles

muscle and lack of supportive cartilage allow bronchioles to dilate and constrict

respiratory bronchioles

feed into alveolar ducts and sac

alveolar sacs

contain alveoli where gas exchange occurs

Type II cells

produce surfactant, reduces surface tension

Infant Respiratory Distress Syndrome (IRDS)

treated with positive-pressure respirators that force air into the alveoli

alveolar pores

connect adjacent alveoli, allows equalized air pressure

alveolar macrophages

crawl freely along the internal alveolar surfaces

respiratory membrane

composed of alveolar wall, capillary wall, and basement membrane

gas exchange

oxygen dissolves into moist film coating the alveolar walls, O2 passes from alveolus into the blood, and CO2 leaves the blood to enter the gas-filled alveolus


composed of air space and elastic tissue

left lung

2 lobes superior and inferior

right lung

3 lobes superior, middle, and inferior

bronchopulmonary segments

each lung lobe contains a number of pyramid shaped segments, separated by septa, and each has its own artery and vein

pulmonary circulation

delivers systemic venous blood to be oxygenated in the lungs

pulmonary arteries

deliver deoxygenated blood to the lungs, feed into the capillary networks

pulmonary veins

return freshly oxygenated blood from the respiratory zones of the lungs to the heart

bronchial circulation

provide systemic blood that nourishes the lung tissue

bronchial arteries

arise from the aorta and run along the branching bronchi, ultimately supply all lung tissues except the alveoli

parasympathetic fibers

constrict the air tubes

sympathetic fibers

dilate the air tubes

atmospheric pressure (Patm)

pressure exerted by the air surrounding the body
-Patm 760 mm Hg at sea level=1atm

intrapulmonary pressure (Ppul)

pressure in the alveoli, rises and falls with the phases of breathing

intrapleural pressure (Pip)

pressure in the pleural cavity, fluctuates with breathing
*always negative relative to Ppul- prevents collapse

lung elasticity

natural tendency to recoil causes the lungs to always assume the smallest size possible

surface tension of alveolar fluid

constantly acts to draw the alveoli to their smallest size possible

lung collapse

due to equalizing of intrapleural pressure and intrapulmonary pressure

transpulmonary pressure

Ppul-Pip keeps lungs from collapsing
-determines the size of the lungs


lung collapse
1.plugged bronchiole
2. pneumothorax

plugged bronchiole

causes associated alveoli to absorb all of their air and collapse, could be result of pneumonia


condition in which air enters the pleural cavity either through a chest wound or rupture of the visceral pleura

chest wound

allows atmospheric air to enter the pleural cavity directly

rupture of visceral pleura

allows air to enter the pleural cavity from the respiratory tract

pulmonary ventilation

1. inspiration
2. expiration


period when air flows into the lungs. Pulmonary pressure decreases to 1 mm Hg below atmospheric


period when air flows out of the lungs, volume of thoracic cavity decrease as inspiratory muscles relax. Pulmonary pressure rises to about 1 mm Hg above atmospheric


contraction causes it to push down--> expands thoracic cavity and pushes lungs downward

external intercostals

expand the ribcage by pulling the ribs upward and the sternum downward

tidal volume

usually 500 ml of air that enters the lungs during normal inspiration--> pulmonary pressure decreases

thoracic volume decreases

1. intra-abdominal pressure increases
2. depressing the rib cage

airway resistance

friction, causes gas flow to decrease due to inhalation of irritants


constriction of bronchioles--> increases resistance


dilates bronchioles and reduces airway resistance--> sympathetic stimulation

lung compliance

1. distensibility of the lung tissue
2. alveolar surface tension- low due to surfactant

diminished lung compliance

decrease elasticity, inflammation/infection--> scar tissue, decreased surfactant

Dalton's Law of Partial Pressures

total pressure exerted by a mixture of gases is the sum of the pressures exerted independently by each gas in the mixture

partial pressure

pressure exerted by each constituent gas in a mixture, directly proportional to the percentage of that gas in the gas mixture


makes up 78.6% of air
Pn2= 78.6% x 760 mm Hg=597 mm Hg


makes up 20.9% of the atmosphere
Po2= 20.9% x 760 mm Hg=159 mm Hg

Henry's Law

mixture of gases is in contact with a liquid, each gas will dissolve in the liquid in proportion to the partial pressure

atmospheric air

mostly all O2 and N2


contain more CO2 and O2

Po2 of blood entering the lungs in pulmonary arteries

40 mm Hg

Po2 in the alveoli

104 mm Hg

Pco2 of blood entering the lungs in the pulmonary arteries

45 mm Hg

Pco2 of air in the alveoli

40 mm Hg

ventilation-perfusion coupling

for efficient gas exchange, there must be a close match between ventilation and perfusion


amount of gas reaching the alveoli


the blood flow in pulmonary capillaries

inadequate ventilation

Po2 is low and pulmonary arterioles constrict

ventilation maximum

Po2 is high and arterioles dilate

bronchioles dilate when

Pco2 is high

bronchioles constrict when

Pco2 is low

Respiratory membrane

0.5-1 mm thick in healthy lungs, efficiency of gas exchange is dependent on the thinnest of the membrane and shortness of diffusion

alveolar surface area



walls of adjacent alveoli break through and the alveolar chambers become larger, decreases surface area available for gas exchange

oxygen carried in blood

1. bound to hemoglobin and RBC(98.5%)
2. dissolved in plasma(1.5%)


composed of 4 polypeptide chains- each chain is bound to an iron-containing heme group. Iron binds to oxygen. Each combines to 4 molecules of O2


hemoglobin bound to oxygen, fully saturated when all 4 heme groups are bound


hemoglobin that has released oxygen

Rate the Hb binds to O2

1. partial pressure
2. Temperature
3. blood pH
4. PCO2

Partial Pressure of PO2 and Hb Saturation

increases as PO2 increases, plateau around a PO2 OF 100 mm Hg, fully saturated when leaves lungs. Not linear relationship with PO2

Temperature, blood pH, PCO2 and Hb Saturation

increases in temp, PCO2, and H+(decrease pH) decrease Hb's affinity for oxygen


inadequate oxygen delivery to body tissues- bluish cast when Hb saturation falls below 75%

anemic hypoxia

reflects poor O2 delivery resulting from too few RBCs or from RBCs that contain abnormal or too little Hb

ichemic hypoxia

results when blood circulation is impaired or blocked
-congestive heart failure

histotoxic hypoxia

occurs when the body cells are unable to use O2 even though adequate amounts are delivered. Results from poisons(cyanide)

hypoxemic hypoxia

indicated by reduced arterial PO2, abnormal ventilation-perfusion coupling, pulmonary diseases that impair ventilation, and breathing poorly oxygenated air

carbonic monoxide

hypoxemic hypoxia- gas competes with O2 for heme binding sites. Confused, throbbing H/A, rare cases cherry red skin. Hyperbaric therapy or 100% O2 until CO cleared from body

Transportation of Carbon Dioxide

1. dissolved in plasma(7-10%)
2. bound to hemoglobin(20%) carried in the RBCs as carbaminohemoglobin
3. as bicarbonate ion in plasma(70%)

Neural control of breathing

medulla oblongata and pons

medulla oblongata

1. ventral respiratory group VRG
2. Dorsal respiratory Group DRG

ventral respiratory group

primary rhythm generating and integrative center. Inspiratory neurons fire along the phrenic and intercostals to excite the diaphragm and intercostals. Expiratory neurons stop the muscles


normal respiratory rate and rhythm 12-15 breaths per minute

morphine and alcohol

can suppress the VRG

Dorsal Respiratory group

integrates input from peripheral stretch and chemoreceptors

Pontine Respiratory Centers

transmit impulses to the VRG of the medulla. Fine tunes breathing rhythms

apneustic breathing

prolonged inspiration with a pause at the end followed by expiration

Factors influencing Breathing

1. inspiratory depth
-greater stimulation=greater # of motor units=greater force
2. respiratory rate

central chemoreceptors

located in the ventolateral medulla, regulate arterial PCO2(40+/- mm Hg)

carbonic acid

formed when CO2 combines with water in CSF


PCO2 levels rise, CSF pH drops


increase in the rate and depth of breathing that exceeds the body's need to remove CO2, dizziness low CO2 level

cerebral ischemia

reduced brain perfusion


breathing cessation

peripheral chemoreceptor

in the aortic arch and common carotid arteries are sensitive to arterial O2 levels (has to drop at least 60 mm Hg before major stimulus)

arterial pH

changes can modify respiratory rate and rhythm even when CO2 and O2 levels are normal

drop in arterial pH

1. CO2 retention
2. accumulation of lactic acid during exercise
3. accumulation fatty acid metabolites (ketone bodies)

hypothalmic controls

strong emotions and pain can modify respiratory rate and depth via interactions between the hypothalamus and respiratory centers

cortical controls

during voluntary control sends signals to the motor neurons that stimulate respiratory muscles

pulmonary irritant reflexes

the lungs contain receptors that respond to an enormous variety of irritants. Communicate via the vagus nerve. Stimulate a bronchiole constriction, cough, or sneeze.

Chronic Obstructive Pulmonary Disease (COPD)

4th leading cause of death in US. Chronic bronchitis and emphysema


insufficient ventilation in relation to metabolic needs causing CO2 retention


episodes of coughing, labored breathing, wheezing, and chest tightness. Exacerbations and remissions. Obstruction is reversible. Inflammation due to T cells

T cells

secrete interleukins, stimulate the productions of antibodies and recruit inflammatory cells to the site

Tuberculosis (TB)

infectious disease caused by mycobacterium. Spread by coughing and primarily enters the body in inhaled air.

latent TB

immune system usually contains the primary infection in fibrous or calcified nodules of the lungs

active TB

fever, night sweats, weight loss, racking cough, and spitting up blood


inflammation of the lungs caused by an infection from bacteria, virus, or fungi. Air sacs in the lungs fill with pus and other fluids which makes it difficult for oxygen to reach the blood

bacterial pneumonia

tend to be the most serious- streptococcus pneumoniae

mycoplasma pneumoniae

school aged pneumonia

lung cancer

leading cause of cancer death

squamous cell carcinoma

25-30% rises in the epithelium of the bronchi or their larger subdivisions. Tends to form masses that may hollow out and bleed


40% originates in the peripheral lung areas as solitary nodules that develop from bronchial glands and alveolar cells

small cell carcinoma

20% cancer that contains small round cells that originate in the main bronchi and grow aggressively in small grape-like clusters within the mediastinum

cystic fibrosis

most common lethal genetic disease in North America. Causes secretion of abnormally viscous/sticky mucuos. Impairs digestion by clogging the pancreatic ducts that deliver enzymes and bile to the small intestine

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