Lecture 15 respiratory system

Respiration encompasses 3 related functions:

ventilation, gas exchange, and O2 utilization

What is ventilation?

movement of air in and out of the lungs for gas exchange (which occurs via passive diffusion) with blood

What is external respiration? What is internal respiration?

- Gas exchange between air and blood in lungs
- gas exchange between blood and tissues & O2 use by tissues

What is the passage way of air from the mouth to the alveoli?

Air goes from mouth, pharynx, trachea, right & left bronchi, bronchioles, terminal bronchioles, respiratory bronchioles, to alveoli

Gas exchange occurs only in .... and all other structures constitute what?

Respiratory bronchioles and alveoli, which is known as the respiratory zone
-all other structures constitute conducting zone

Gas exchange occurs across ___ million alveoli. Only 2 thin cells are between lung air and blood: ____ and ____

300 million
-1 alveolar and 1 endothelial cell

What is shape and structure of alveoli?

Are polyhedral in shape, clustered at ends of respiratory bronchioles, like honeycombs
-air in 1 cluster can pass to others through pores

What is is the function of the conducting zone?

Warms and humidifies inspired air
-has mucus lining filters and cleans inspired air
-musics moved by cilia to be expelled

Thoracic cavity is created by the what?

The diaphragm, a dome shaped sheet of skeletal muscle

What is above the diaphragm? Below the diaphragm?

Above: heart, large blood vessels, trachea, esophagus, thymus and lungs
Below: abdominopelvic cavity which contains liver, pancreas, GI, spleen, and genitourinary tract

What is the intrapleural space?

space between parietal and visceral pleura

What does Boyle's law states?

States that changes in intrapulmonary pressure (pressure in alveoli and rest of lungs) occur as a result of changes in lung volume
-pressure of gas is inversely proportional to volume

Increase in lung volume _____. While decrease in lung volume _____.

Decreases intrapulmonary pressure causing inspiration
Increases intrapulmonary pressure causing expiration

What is compliance? ***

How easily lung expand with pressure
-reduced by factors that cause resistance to distension

What is elasticity? What is it due to? And elastic tension increases when? *****

-is tendency to return to initial size after distension
- due to high content of elastin proteins that resist distension
-increases during inspiration and is reduced by recoil during expiration

What is ST? What does it promote? ******

-ST is created by intermolecular forces within fluid molecules that attract molecules to each other
- ST and elasticity are forces that promote alveolar collapse and resist distension

The lungs secrete and absorb fluid, normally leaving a thin film of fluid on alveolar surface. Know this


What are surfactants? What is impact on ST and how? What do they prevent? ****

-phospholipids secreted by alveolar cells
-lower ST by getting between H2O molecules, reducing their ability to attract each-other via hydrogen bonds
-prevent surface tension from collapsing alveoli

Inspiration occurs mainly because ?
Expiration is due to ___

Diaphragm contacts, increasing thoracic volume vertically
-due to passive recoil

In quiet breathing, ___ and ____ contraction contributes a little by raising ribs, increasing thoracic volume laterally

Parasternal and external intercostal

In deep breathing, inspiration involved contraction of extra muscles to elevate ribs which are:

Scalenes, pectoralis minor, sternocleidomastoid muscles

In deep breathing, expiration involves

Contraction of internal intercostals and abdominal muscles

What is dyspnea?

difficulty breathing, shortness of breath

What does asthma result from? Caused by? Provoked by? Treated with?

Results from episodes of obstruction of air flow through bronchioles
-caused by inflammation, mucus secretion, and broncho-construction (inflammation contributes to increased airway responsiveness to agents that promote bronchial constriction)
-provoked b

Emphysema is what? What does it result in? And reduced what?

Chronic, progressive condition that destroys alveolar tissue
-results in fewer larger alveoli
-reduces surface area for gas exchange and ability of bronchioles to stay open during expiration (air trapping; decreased gas Ex.)

What is pulmonary fibrosis Characterized by? Occurs from?

-accumulation of fibrous connective tissue
-occurs from inhalation of particles such as coal dust

What is partial pressure? What is Dalton's law? What is atmospheric pressure

-is pressure that a particular gas in a mixture exerts independently
-states that total pressure of a gas mixture is the sum of partial pressures of each gas in mixture

Gas exchange in lungs is driven by ? What is it facilitated by?

differences in partial pressures of gases between alveoli and capillaries
-facilitated by:
�enormous surface area of alveoli
� short diffusion distance between alveolar air & capillaries
�tremendous density of capillaries

When blood and alveolar air are at gaseous equilibrium, the amount of O2 in blood____

Reached a maximum value

What does Henry's law state? ******

Says that this value depends on solubility if O2 in blood (constant), temperature of blood (constant) and partial pressure of O2
-so the amount of O2 dissolved in blood depends directly on its partial pressure, which varies with ALTITUDE

O2 toxicity can develop rapidly at ?

More than 2.5 atmospheres under sea level
-lead to coma and death (bc of oxidation damage)
-breathing O2 at less than 2 atmospheres can be tolerated for a few hours
-at depth, increase dissolved O2 and N2 can be dangerous

At sea level, nitrogen is physiologically inert and it dissolved slowly in blood. But under hyperbaric conditions, N2 takes more than an hour for dangerous amounts to accumulate. Nitrogen narcosis resembles

Alcohol intoxication

Amount of nitrogen dissolved in blood as diver ascends ____ due to decrease in ____. What happens if ascend is too rapid?

Decreases ; PN2 (excess N2 is expired over time)
If ascent is too rapid, decompression sickness occurs as bubbles of N2 form in tissues and ensued blood, blocking small blood vessels and producing bends

Automatic breathing is generated by a _____ in ____

Rhythmicity center in medulla oblongata

____ ____ drive inspiration . _______ inhibit inspiration.

Inspiratory neurons ; expiratory neurons

Inspiratory neurons stimulate _______. Expiration is ____

Spinal motor neurons that innervate respiratory muscles
- passive and occurs when inspiratory muscles are inhibited

Activities of medullary rhythmicity center are influenced by centers in pons. Apneustic center promotes _______ . Pneumotaxic center antagonizes _____

Promotes inspiration by stimulating neurons
-antagonized apneustic center, inhibiting inspiration

Automatic breathing is influenced by activity of ____ that monitor blood PCo2, P02, and Ph


_____ are in the medulla. ____ are in large arteries near heart and carotids

Central chemoreceptors ; peripheral chemoreceptors

Chemoreceptors modify ventilation maintain normal Co2, O2 and pH levels. Why is PCO2 most crucial?

Bc of its effects on blood PH, combined with H2O forming carbonic acid)

Hyperventilation causes ____. Hypoventilation causes____

Low CO2 (hypocapnia) and high Ph
High CO2 (hypercapnia) and low PH
-brain chemoreceptors are responsible for greatest effects on ventilation

Hering-Breuer reflex is mediated by? And activated during? What does it inhibit respiratory centers to prevent?

-stretch receptors
-activated during inspiration
-inhibits respiratory centers to prevent over inflation of lungs

Loading of HB with O2 occurs where? Each HB has 4 ___ polypeptide chains and 4 ___ that bind O2

-4 globin polypeptides & 4 heme groups that bind O2

Most O2 in blood is bound to _____ inside RBCs as what?


_____ is heme combined with carbon monoxide

-200 times stronger than bind with o2

In anemia, ___ levels are below normal. In polycythemia, ____ levels are above normal.


What is HB production controlled by? Stimulated by?

Erythropoietin EPO
-by low PO2 in kidneys

Why are HB levels higher in men?

Because androgens promote RBC production