Chapter 13 Respiratory system

what is the function of the respiratory system?

to obtain O2 from the environment and dispose of CO2

What are the 5 processes that compose respiration

• pulmonary ventilation

• external respiration

• gas transport

• internal respiration

• Cellular respiration

Pulmonary ventilation

• breathing

• 2 components

  • inspiration: air that goes into the lungs

  • expiration: air that goes out of the lungs

External respiration

• between the lung capillaries and the air in the alveoli

• O2 diffuses from the I\air in the alveoli into the blood

• CO2 diffuses from the blind into the air in the alveoli

Gas transport

• by the cardiovascular system

• O2 from the lungs to the tissues

• CO2 from the tissues to the lungs

Internal respiration

• between the tissues capillaries and the cells in the tissues

• O2 diffuses from the blood to the tissues

• CO2 diffuses from the tissues to the blood

what composes the upper respiratory system

• paranasal sinuses

• nose

• pharynx

• larynx

what composes the lower respiratory system

• trachea

• bronchi

• bronchioles

• lungs

Cellular respiration

• Cells use O2 and produce CO2 during ATP synthesis

The respiratory system is a _____ pathway

one-way

general function of the upper aerial pathway

conduct, filter, moisten and warm inspired air

Vibrissae

• found in the naval cavity

• hair that lines the nasal vestibule

• filter coarse particles from inspired air

Nasal conchae

• found in the naval cavity

• warms up, filters, moisturizes and heats the inhaled air

• cool down and recover moisture from the expired air

two structures found in the naval cavity

• vibrissae

• nasal conchae

Respiratory mucosa where is found, structure and function

• found along the respiratory tract up to the respiratory bronchioles

• structure:

  • ciliated epithelium + goblet cells

  • mucous glands in the lamina propria

  • richly innervated -→ sneeze and cough reflexes

• function

  • creates a sticky surface to trap particulate matter

  • cilia continuously move mucus + trapped particulate matter towards the pharynx to be swallowed → mucous escalator

mucous escalator

• cilia continuously move mucus + trapped particulate matter towards the pharynx to be swallowed

Anatomical pathway was air enters

• larynx

• trachea

• bronchi

• lungs

• bronchioles

• alveoli

• this pathway is split into two functional zones based on whether or not they handle gas exchange

anatomical division of the lower respiratory system, which structures fall into each category and what are their functions

• conducting zone and respiratory zone

  • conducting zone:

    • trachea, bronchi, bronchioles and terminal bronchioles

    • acts as rigid conduits to transport air into and out of the lungs while cleansing, warming and moisturizing it

    • there is no gas exchange that occurs here

  • respiratory zone

    • respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli

    • the active site where oxygen and carbon dioxide are exchanged between the air and the blood stream

two divisions of the lower respiratory system

• conducting zone

• respiratory zone

explain the 3 changes that occur as the bronchi branch from the main bronchi down to the alveoli

• cartilage and elastic fibers

  • hyaline cartilage decreases

  • elastic fibers increase, providing flexibility needed for the airways to expand and recoil

• Epithelial transition

  • pseudostartified columnar → bronchi

  • simple columnar → bronchioles

  • simple cuboidal → terminal bronchioles

  • simple squamous → alveoli

• smooth muscle and airflow regulation

  • smooth muscle increases

  • increased pathway contractility to allow the nervous system and local chemical signals to actively regulate resistance to air flow

epithelium in the terminal bronchioles

simple cuboidal

epithelium in the alveoli

simple squamous

Epithelium in the bronchi

• pseudostartified columnar

Alveolar structures: capillaries, elastic fibers

• dense network of capillaries in the abluminvl side of the alveolar sav

  • large surface of gas exchange

• mesh of elastic fibers around each alveolus

  • facilities the alveolar recoil during expiration

alveoli

• pouch-like structures of simple squamous epithelium that bundle to form the alveolar sac

Components of the alveolar

• Type I alveolar cells

• Type II alveolar cells

• Alveolar marcophases

• alveolar porse

• respiratory membrane

Type I alveolar cells

• thin, simple squamous epithelial cells that form the structural walls of the alveoli

Type II alveolar cells

• specialized secretory cells that produce pulmonary surfactant

Alveolar macrophages

wandering immune cells that phagocytize and clear out inhaled dust, bacteria and debris

alveolar pores

• openings connecting neighboring alveoli that allow air pressure to equalize across different lung regions

Respiratory membrane function

• an ultra thin blood-air barrier which permits rapid diffusion of oxygen and carbon dioxide

what composes the respiratory membrane in the alveolar

• Type I alveolar cells

• basement membrane

• and endothelial cells

function of alveolar surfactant

• liquid coating the liminal alveolar surface produces surface tension that drives the alveoli to their smaller size and collapse

surfactant produced by the type II alveolar cells …..

• reduces surface tension and prevents alveoli from collapsing

the lung is an organ made out of ….

air-filled spaces

Lungs: ______ _______ ______ that occupy most of the thoracic cavity

spongy elastic organs

Anatomical landmarks of the lungs:

• cone shaped

• apex: superior tip of the lung (at the level of the clavicle)

• base: concave inferior surface (rest in the diaphragm)

• hilum: receive the blood vessels, bronchi, fevers and lymphatic vessels

2 Lung coverings (pleura)

• visceral pleurae

• parietal pleurae

Visceral pleurae

covers the lung and lines its fissures

Parietal pleurae

covers the walls of the thoracic cavity and the diaphram

The pleurae produces pleural fluid that: (3)

• fills the pleural cavity

• prevent the friction between the organs

• create surface tension between the parietal and visceral pleurae

when the thoracic cavity expands what happens to the lungs

the lungs also expand

4 muscles that are associated to the ribcage

• diaphragm

• external intercostals

• internal intercostals

• innermost intercostals

Diaphragm: points of attachment and actions

• points of attachment: xiphoid process of sternum; ribs and costal cartilages 7-12; lumbar vertebrae. central tendon of diaphragm

• actions: prime mover of inspiration (responsible for about two-thirds of air intake); contraction expands the thoracic cavity, compresses abdominal viscera (aids in childbirth and expulsion of urine and feces)

External intercostals: points of attachments and actions

points of attachment: inferior margins of ribs 1-11. Superior margin of next lower rib

Actions: elevate and protract ribs 2-12 expanding the thoracic cavity

Internal intercostals: points of attachments and actions

points of attachment: superior margins and costal cartilages of ribs 2-12: margin of sternum. Inferior margin of next higher rib

actions: air in inspiration. in forceful expiration, depresses and retracts the ribs

Innermost intercostals: points of attachments and actions

• points of attachment: superomedial surface of ribs 2-12. medial edge of coastal groove of next higher rib

• actions: same action as the internal intercostals

pulmonary ventilation

• exchange of air between the atmosphere and the alveoli

As with blood, we need a differential of pressure to circulate the air form one point to another as ……..

air flows from areas of high pressure to areas of low pressure

equation that represents air flowing form an area of high pressure to low pressure

F = deltaP / R

What 2 pressures need to change to move air in and out in this dead-end system?

• atmospheric pressure (Patm)

• Intrapulmonary alveolar pressure (Palv)

Atmospheric pressure (Patm) and when does it change

• pressure exerted by the column of gas molecules above your head

• Patm changes with the altitude, it is lower at higher altitudes because of the column of gases is smaller

Patm at the level of the sea

• 760 mmHg

Intrapulmonary alveolar pressure (Palv)

• pressure inside the lungs alveoli

If the air must flow in and out of the alveoli following the same pathway how must the Palv change during each breath cycle?

• to pull air in (inspiration), Palv must be lower than Patm

• to push air put (expiration), Palv must be higher than Patm

The pressure of a given gas is determined by …….

the collisions of the molecules in the gas against the walls of the container

Boyles law, equation and explain it

P1V1 = P2V2

• at constant temperature, the pressure of a gas varies inversely with its volume

What happens to Palv when the alveolus stretches / contracts

stretches: Palv decreases

contracts: Palv increases

The lungs are elastic stcutres that tend to recoil to their minimal size because of:

• the large number of elastic fibers that alveoli and the airways have

• the surface tension of the liquid that coats the alveolar lumen

What happens when we force the lungs to expand and increase their size?

They will recoil and contact by themselves

What happens if we replace these elastic fibers with scar tissue made of collagen fibers that cannot be stretched? what decreases?

• the lung tissues loses its stretchability and becomes rigid

• Vital capacity and total lung capacity decreases

Mechanics of inspiration: 5 steps (Muscle relaxation, volume reduction, elastic recoil, pressure rise, airflow)

• muscle action: the diaphragm contacts and moves downwards and the intercostal muscles contract to elevate the ribs

• volume expansion: these msucle movements increase the overall volume of the thoracic cavity by about 500 mL during normal breather

• lung stretching: as the thoracic cavity expands, it streches the lungs and alveoli, increasing their internal volume

• pressure drop: Boyles law - increasing the volume lowers the Palv pressure so that it drops below atmospheric pressure

• airflow: air flows from high pressure to low pressure, air is pulled into the lungs

Mechanics of expiration: 5 steps (Muscle relaxation, volume reduction, elastic recoil, pressure rise, airflow)

• muscle relaxation: the diaphragm relaxes and ascends, and the external intercostal muscles relax, allowing the ribs to descend

• volume reduction: the volume of the thoracic cavity decreases

• elastic recoil: the stored energy in the lungs elastic fibers causes the tissue to recoil, shrinking the volume of the lungs and the alveoli

• pressure rise: decreasing the volume compresses the air inside, causing Palv to rise above Patm

• airflow: with internal pressure now higher than the outside atmosphere, air flows out of the lungs

The walls of the thoracic cavity are not physically attached to the lungs, how do they stretch when the thoracic cavity expands?

• the thoracic cavity is sealed so that the surface tension of the molecules in the pleural fluid is sufficient to work as adhesive between the parietal and visceral pleurae

• when respiratory muscles expand the chest wall outward, the fluid cohesive forces prevent a gap from forming, forcing the visceral plural and the lung tissue to be stretch along

The difference between Palv and Pip

transpulmonary pressure (Ptp)

How is Transpulmonary pressure (Ptp) created?

It is created by the adhesion of the parietal and visceral pleurae, keeping the lungs inflated against their natural elastic recoil

factors that affect the flow of air into the lungs

• lung compliance

• chest wall compliance

• change in airway resistance

lung compliance

• the magnitude of the change in lung volume delta V, produced by a given change in the transpulmonary pressure

• C_L= deltaV_L / deltaP_tp

• As C_l increases, it makes it easier to expand the lungs by chaining transpulmonary pressure

Major determinants of lung compliance (2)

• stretchability of the lung tissues

  • replacing elastic fibers by collagen fibers → decrease in Cl → lung fibrosis

• action of surfactant

  • decreased surfactant causes increase in alveolar surface tension → decrease in Cl → respiratory distress syndrome in premature newborns

Chest wall compliance can be impaired by:

• paralyzed intercostal muscles

• thorax deformities that restrict normal expansion of the thoracic cavity

what does an increase in lung compliance mean?

the lungs are overly stretchy and require very little pressure to inflate

what does a decrease in lung compliance mean?

the lungs are stiff and rigid, requiring a much larger pressure change just to get a small volume of air inside

Changes in airway resistance:

• bronchoconstriction increases airway resistance

• air flow = deltaP / R

• inhalation of irritants that activate the parasympathetic nervous system

• release of histamine during an asthma attack

Respiratory volumes

• volume of air flushed in and out of the lungs during a breathing cycle

  • give info about the individual respiratory status

  • measured using a spirometer

• tidal volume (TV)

• inspiratory reserve volume (IRV)

• expiratory reserve volume (ERV)

• residual volume (RV)

tidal volume (TV)

• volume of air inspired or expired during a normal breathing cycle (`500 mL)

Inspiratory reserve volume (IRV)

• volume of air that can be forcibly inspired beyond the tidal volume (2100-3200 mL)

Expiratory reserve volume (ERV)

• volume of air that can be forcibly expired beyond the tidal volume (1000 - 1200 mL)

Residual volume (RV)

• volume of air that remains in the lungs after a forced expiration (~1200 mL)

Respiratory capacities

• Inspiratory capacity (IC)

• Functional residual capacity (FRC)

• Vital capacity (VC)

• Total lung capacity (TLC)

Inspiratory capacity (IC)

• total volume of air that can be inspired after a normal tidal expiration (~3600 mL)

• IC = TV + IRV

functional residual capacity (FRC)

• volume of air that remains in the lungs after a normal tidal expiration (~2400 mL)

• FRC = ERV + RV

Vital capacity (VC)

• total volume of air that can be exchanged (~4800 mL)

• VC = TV + IRV + ERV

Total lung capacity (TLC)

• total volume of air in the lung (~6000 mL)

• TLC = TV + IRV + ERV + RV

Other pulmonary function tests

• forced vital capacity (FVC)

  • patient takes a deep breath and exhales maximally as fast as possible → vital capacity is determined

  • restrictive pulmonary disease will have a lower FVC because their lungs are small or still but more than 80% of tot

• forced expiratory volume in one second (FEV1)

  • patient takes a deep breath and forcefully exhales maximally as fast as possible → volume of air exhaled in one second is determined and referred to as percentage of the viral capacity

  • normal will exhale roughly 80% or more of their total vital capacity in the first second

  • obstructive pulmonary disease will exhale less than 80% of their total volume in the first second because of narrow airways

obstructive pulmonary disease:

• increase airway resistance

• measurements may increase because of lung hyperinflation:

  • total lung capacity

  • functional residual capacity

  • residual volume

restrictive pulmonary disease

• reduced lung capacity due to reduced lung or chest comliance

• measurements may decrease because of lower lung expansion

  • vital capacity

  • total lung capcity

  • functional residual capacity

  • residual volume

Dead space

• the volume of air contained in the respiratory system that does not participate in gas exchange

Alveolar dead space:

• alveoli that dont participate in exchange of gases

  • they are ventilated but under perfused, collapsed or filled with mucus

Physiological dead space =

• anatomical dead space + alveolar dead space

• fresh inspired air mixes with old air retained in the dead space

What happens during external respiration

• gas exchange occurs across the respiratory membrane

• oxygen enters the blood

• carbon dioxide leaves the blood

what happens during internal respiration

• gas exchange occurs between capillary blood and the intersritum

• oxygen leaves the blood

• carbon dioxide enters the blood

in the steady state, the net volume of O2 consumed by the body cells is equal to the volume that…..

diffuses into the blood at the lungs

in the steady state, the net volume of CO2 produced by the body cells is equal to the volume that…..

diffuses out of the blood at the lungs

4 gases in the air

• nitrogen 78.6%

• oxygen 20.9%

• water vapor 0.5%

• carbon dioxide 0.04%

daltons law of the partial pressures

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

• pressure that correlated with the proportion of each gas in the mixture

what is the main determinant of how much gas is dissolved in a liquid

the pressure of the gas - Henrys law

when a gas is in contact with a liquid, the gas will dissolve in the liquid in proportion to its partial pressure until ….

it reaches an equilibrium

describe henrys law

the amount of gas dissolved in a liquid is proportional to its partial pressure

what are two factors that determine how much gas is dissolved in a liquid

• solubility of the gas

• temperature of the solution

why are alveolar gas pressures not identical to atmospheric pressures?

because we never fully empty out lungs

the new inspired air mixes with the Functional residual capacity FRC