Chapter 22 Respiratory System

Respiration

• Is the exchange of gases between the atmosphere, blood, and the cells

• It supplies cells with O2

• It eliminates CO2 from the blood

Pulmonary Ventilation

The exchange of gas between the atmosphere and the lungs

External Respiration

The exchange of gas between the lungs and the blood

Internal Respiration

The exchange of gas between the blood and the cells 

Root

Region located between the eyebrows

Bridge

Connects the root to the rest of the nose

Dorsum Nasi

Bridge of length of the nose

Apex

Tip of the nose

Nares

Terminal openings of the nose (nostrils); singular = naris

Ala

Cartilginous structure forming the lateral side of each nostril

Philtrum

Concave structure connecting the end of the nose to the upper lip

Internal Nose

• Contains hairs and mucuc membranes

• It is highly vascular to warm, moisten, and filter the air

• Contains receptor for send of smell

• It is dived laterally intwo two chambers by a nasal septum

  • Paranasal Sinus

  • Nasolacrimal Duct

Paranasal Sinuses

• Air-containing soaces in several bones of the walls of the nasal cavity

• Function to warm and humidify incoming air and reduce the weight of the skull, serves a resonating chambers for speech

Nasolacrimal Duct

• From the eyesw opens into nasal cavity

• This is why your nose geswt runny when you cry

Pharynx

• Considered the Throat

• Common passageway for food and air

• It is connected to nasal passaes via internal nares

• It is also connected to oral cavity

• There are three sections

  • Nasopharynx (uppermost portion, connects internal nares)

  • Ororpharynx (behind oral cavity)

  • Larynopharynx (bottom portion, above larynx)

Larynx

• Considered the Voicebox

• It connects the pharunx to the trachea

• Helps to regulate the volume of air that enters and leaves the lungs

• Formed by three cartilages:

  • Thyroid Cartilage

  • Circoid Cartilage

Thryoid Cartilage

• Forms the laryngeal prominence, or “Adam’s apple”

Cricoid Cartilage

• Forms a ring of cartilage with a wide postertior region and a thinner anterior region

• Provides attachments to the epiglottis, vocal cords, and muscles that aid movement of the vocal cords during speech

Epiglottis

• Attached to the thyroid cartilage

• It is a very flexible piece of elastic cartilage that covers the glottis or opening of the trachea

• It prevents food from entering the trachea when swallowing

Trachea

• Considered the “windpipe”

• Tube from larynx, located in neck and thorax

• At base, it splits into left and right bronchi

• Anter to esophagus

• 16-20 C-shaped cartilage located around it to prevent collapse

• Lined with cells bearing cilia that sweep mucus out

Bronchi & Bronchioles

• A series of tubes, of decreasing diameter, which connect the trachea and alveoli

• The first large diameter branches, off of the trachea, are called the primary bronchi

• The secondary and tertiary brocnhi branch off subsequently, andeventually branch into the bronchioles

• There are complete cartilage rings or plates that function to maintain shape of the bronchi

• Bronchioles lack cartilage rings

Lungs

• They are pyramid-shaped, paired organs located in the thoracic cavity

• They are connected to the trachea by the right and left bronchi

• The lungs are bordered inferiorly by the diaphragm

• Contain > 350 million alveoli

• Alveoli contain the actual respiratory epithelial surface

• Bronchioles deliver air to the alveoli via alveolar ducts

Pulmonary (visceral) pleura

• The connective tissue on the surface of the lungs

Parietal pleura

• The connective tissue sac containing the lungs

Diaphragm

• Is the flat, dome-shaped muscle located at the base of the lungs and thoracic cavity

• It is composed of skeletal muscle

  • You can voluntarily hold your breath

• Changes the volume of the thoracic cavity

Boyle’s Law

The pressure of a gas in a closed container is negatively related to the containers volume

Inspiration

• The air pressure in lungs must be less than atmospheric air pressure

• Reducing air pressure is accomplished by increasing lung volume

• Lungs pulled outward and downward by contraction of diaphragm and intercostal muscles, increasing the volume of the thoracic cavity

• Causes the lungs to expand

• Air pressure in the lungs decreases as the volume increases

• When pressure in the lungs is less than atmospheric pressure, air rushes into the lungs

• Summay (Boyle’s Law):

  • Increase lung volume, decrease air pressure
    

Expiration

• A passive process caused by a reverse pressure gradient

• When the diaphragm and inter coastal muscles relax, the volume of the thoracic cavity decreases and the lungs elastically recoil, thereby reducing their volume

• The pressure in lungs increases, and when the pressure inside the lungs is greater than atmospheric pressure, air is pushed out of lungs

• Summay (Boyle’s Law):

  • Decrease lung volume, increase air pressure

Gas Laws

• Gas exchange between the air and blood and between the blood and tissues is passive, it requires no energy expenditure by the body

• Gas exchange follows the law of diffusion, so it always moves from an area of higher concentration or pressure to one of lower concentration or pressure 

Dalton’s Law

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

• Each gas has its own partial pressure which is independent of the partial pressure of the other gases in the atmosphere

• The partial pressures of all of the gases are summed, to yield the total atmospheric pressure

Henry’s Law

• Quantity of a gas that will dissolve in a liquid is proportional to the partial pressure and solubility of the gas at a constant temperature

• Solubility coefficients (Higher the number, higher the solubility)

  • EX: CO2 = 0.57, O2 = 0.024, N2 = 0.012, CO2 higher solubility

• Result is that the concentration that the concentration of a gas in the liquid will depend on:

  • Partial pressure of the gas

  • Solubility of the gas

  • Temperature

    • Solubility & temperature are relatively constant in a human so it is the partial pressure that matters most

      
      

Oxygen Transport

• O2 is not very water soluble 

• O2 is carried in the form of oxyhemoglobin:

  • oxygen bound to hemoglobin

• Fully saturated

  • Occurs when deoxyhemoglobin is fully converted to oxyhemoglobin

• Partly saturated 

  • A mixture of deoxyhemoglobin & oxyhemoglobin

• A positive relationship exist between the partial pressure of O2 and the percent saturation of hemoglobin

  • The higher the partial pressure, the more the blood is saturated (more O2 is carried in blood)

• When the partial pressure of O2 is high, O2 bind to hemoglobin to form oxyhemoglobin

• When the partial pressure of oxygen is low, O2 is released from hemoglobin

Factors that Affect the O2 Saturation

• Acidity - pH

• Partial pressure of CO2 

  • When CO2 dissolves in H2O, it combines with the H2O to form carbonic acid

  • Carbonic acid then dissociates or breaks apart to form a H+ ion and bicarbonate ion

  • The H+ ion causes acidity, so the effect of other acids and the effect of CO2 ends up being similar

• Temperature

  • Promotes O2 unloading, or being released, from hemoglobin

  • Permits active tissues that metabolize to receive more O2

• BPG (Bisphophaglycerate)

  • Binds to hemoglobin and promotes O2 unloading or releasing

  • Fever and hormones like growth hormone, testosterone, and epinephrine stimulate BPG production and cause more O2 to be released

Carbon Dioxide Transport

• Deoxygenated blood contains - 55ml CO2/100 ml in three forms

  • CO2 is dissolved in the water in the blood

  • Carbaminohemoglobin - bound to the amino acids in hemoglobin

• Bicarbonate ions:

  • CO2 + H2O ←> H2CO3 ←> H+ + HCO3-

  • Otherwise CO2 transport is the opposite of O2 transport

External Respiration

• Gas exchange between the alveolus (lungs) and the blood

• O2 diffuses from the alveolus into the blood

• CO2 simultaneously diffuses out of the blood into the alveolus

• The gases move from an area of greater partial pressure (concentration)  to one of lower partial pressure

• Rate of external respiration depends on:

  • Partial pressure difference of the gases

  • Surface area for gas exchange (constant unless pneumonia or TB causes scarring)

  • Diffusion distance (constant unless mucus accumulates in the alveoli)

  • Solubility and molecular weight of the gas (constant)

    
    

 Internal Respiration

• This is gas exchange that occurs between the blood and body tissues

• It is similar to external respiration, in that the concentration of O2 is higher in the blood than in the tissues so the O2 diffuses from the blood into the tissues

• The reverse is true for CO2 (moves into blood)

O2: into the blood

CO2: out of the blood

When diffusion of gases occurs between the lungs and blood, which way do O2 and CO2 move?

O2: out of the blood

CO2: into the blood

When diffusion of gases occurs between blood and body tissues, which way do O2 and CO2 move?

 Carbon Monoxide Poisoning

• CO is a colorless, orderless gas

• The gas occurs in cigarette smoke, engine exhaust, fumes from furnaces, space heaters, and generators

• CO bins to iron in hemoglobin

• It competes with O2 for the binding site

• But CO binds 210 times as tightly as O2 (tie up hemoglobin longer)

• Atmospheric concentration of 0.1% CO is enough to bind 50% if a person’s hemoglobin

• Atmospheric concentration of 0.2% is lethal 

Respiratory Center

• Located bilaterally in the medulla oblongata & the pons

• Increases & decreases the size of the thoracic cavity

• Three areas: Controls the basic rhythm of respiration

  • Inspiratory Area

  • Expiratory Area

  • Pneumonic Area

Inspiratory Area

• At beginning of expiration, the inspiratory region is inactive

• After 3 sec it becomes active

• Results from autorhythmic cells

• APs last about 2 sec & are transmitted to inspiratory muscles

• Inspiratory muscles contract 2 sec later respiratory muscles relaX & cycle continues

Expiratory Area

• Inactive during most, quiet, normal expirations

• Labored breathing stimulates APs, which cause contraction of the internal intercoastal & abdominal muscles

• Further reducing the size of the thoracic cavity causes a greater expiration 

Pneumonic Area

• Located in the pons

• Coordinates the transitions between inspiration & expiration

• Transmits inhibitory impulses to the inspiratory area

• Prevents the lungs from becoming too full, by limiting the duration of inspiration

Apneustic Area

• Located in pons

• Also coordinates the transition between inspiration & expiration

• Sends impulses to stimulate a prolonged inspiration 

• It inhibits expiration

• When the pneumonic area is active it overrides the apneustic area

Cortical Effects

• Cerebral cortex has connections with the respiratory center and regulates it

• We can voluntarily prevent an inspiration or expiration when we need to hold our breath

• Limited by the buildup of CO2 & H+ in the blood

• H+ hydrogen strongly influences the inspiratory center

• When H+ hydrogen levels are high, action potentials are sent to respiratory muscles

• Causes an inspiration whether the person wants to breath or not

Chemical Regulation

1. Particular chemical cues determine how fast & deeply we breath

2. Chemoreceptors monitor the levels of O2 & CO2 & provide info to the respiratory center

3. Also causes Hypercapnia & Hypocapnia

Hypercapnia

• Occurs when there is a slight increase in the partial pressure of Co2

• Stimulates the central chemoreceptors

Hypocapnia

Occurs when there is a decrease in the partial pressure of CO2