Respiratory System

A&P Exam 3

Functions of the respiratory system

Provides O2 to blood, gets rid of CO2 in blood, speech, defends against inhaled microbes, traps and dissolves blood clods, converts angiotensin to influence arterial concentrations

Describe conversion of angiotensin

Endothelial cells of pulmonary capillaries contain ACE → converts angiotensin I into angiotensin II → vasoconstricts arterioles

ACE must be in the lungs because 100% of blood goes through lungs

Anatomy and function of respiratory system

Nasal cavity - warms, filters, and moistens air

Pharynx - pathway for air, liquid, food

• Esophagus - travels to stomach to deliver food and liquid

• Larynx - part of airways and has vocal cords

• Epiglottis is a flap that covers the glottis, which goes to the lungs, prevents food from going into lungs

Cartilaginous C rings that hold airway open

Explain ciliary mucus

Epithelial surfaces at end of bronchioles have cilia that flow up towards pharynx, secretes watery mucus/goblet cells

Particulates matter and dust that’s moved by cilia to pharynx where it’s swallowed, keeps lungs clear

Order branching from top to bottom

Conducting zone (anatomical dead space, no gas exchange): Trachea → bronchi → bronchioles → terminal bronchioles →

Respiratory zone (gas exchange): respiratory bronchioles → alveolar ducts → alveolar sacs

Describe alveoli

Tiny hollow sacs that are continuous at the ends with a large surface area, main site of gas exchange

Describe the types of alveoli

Type I - flat epithelial cells, single layer thick, make up alveolar walls

Type II - secrete surfactant that prevents collapse of alveoli

Describe the pleural sac and its parts

Intrapleural sac, parietal pleaura, visceral pleura

Intrapleural sac is very thin, has few mL of fluid that reduces friction

Explain the steps of respiration

Bulk flow between air in atmosphere in alveoli

Exchange of O2 and CO2 in alveolar air and blood in lung capillaries via diffusion

Transport of blood through circulation with bulk flow

Exchange of gas between tissues and blood

Cellular utilization of O2 and production of CO2

What must match in the steps of respiration

The amount of ventilation needed matches the amount of cellular respiration occurring.

Equation for transpulmonary pressure

= P alveolar - P interpleural

Equation for chest wall pressure

= P interpleural - P atmospheric

How does alveolar P change with the lungs

When air comes into the alveoli, the lungs expand, P alv < P atm.

When air leaves the alveoli, the lungs become smaller, Palv > P atm

What is Boyle’s Law

States that at constant temperature and at a fixed number of gas molecules, pressure is inversely proportional to the volume of the container

Name and explain skeletal muscles used in respiration

Diaphragm - contacts to move abdomen down and enlarge the thorax

External intercostals - contracts to pull ribs up and out to increase thoracic cavity

Accessory muscles - for deeper and forceful inhalations

• Includes sternocleidomastoids and scalenes, pulls ribs up

Internal intercostals - forceful, exercised exhalation and depresses ribs to narrow thoracic cavity

Abdominal muscles - moves diaphragm up and compresses abdominal organs

How is the chest wall aided by elastic recoil

Elastic recoil holds the chest wall inward and downward by attachment to parietal wall of pleural sac, transmural pressure gradients, and surface tension

How are the lungs aided by elastic recoil

Elastic recoil open the lungs to a larger volume by attachment to visceral wall of pleural sac, transmural pressure gradients, and surface tension

What does it mean when the transpulmonary pressure is pos or neg?

Pos - P is greater in alveoli → lungs are bigger and held open

Neg - P is greater in IPS → lung collapses (fatal)

What does it mean when the chest wall pressure is pos or neg?

Pos - P is greater in the IPS → chest wall is stretched and recoils inward

Neg - P is greater in the atm → chest wall caves inward and recoils outward

Define, point out, and equation of functional residual capacity

FRC is the volume of air remaining in lungs at the end of a quiet exhale when muscles are relaxed

RV + ERV

At FRC, _____ _____ of chest wall = _____ ____ of the lung

Outward recoil ; inward recoil

At FRC, _______ pressure = _________ pressure

Alveolar ; atmospheric → no movement of air

Describe pneumothorax

Puncture of chest wall → air from atm goes into the IPS → Pip becomes 0 and loses pressure gradient → Ptrans becomes 0 and lungs are free to collapse

Describe atelectasis

Collapse or blockage of lungs by disease, genetics, infections, ventilation malfunction

Air leaks from lungs → IPS → lungs lose air and collapse

What is meant by pneumothorax and atelectasis being unilateral

Usually affects just one lung at a time because the pleural sacs are different from right and left

Explain the phase of the cycle at the end of exhalation and beginning of inhalation

At FRC

• No air flow

• Palv = Patm

• Pip = 4

• Muscles are relaxed

Explain the phase of the cycle at mid-inhalation

Diaphragm and external intercostals are pulling chest wall out to increase volume of IPS and lungs

• Air flows from atm → lungs

• Pip decreases to -6

• Palv decreases to -1

• P trans increases (is held more open)

Explain the phase of the cycle at end of inhalation and beginning of exhalation

Diaphragm and external intercostals are no longer contracting, lungs are at largest volume

• No air flow

• P atm = P alv

• Pip = -7

• Ptrans = 7

• Reached tidal volume

Define, exact #, and point out tidal volume

The amount of air inhaled or exhaled during a single breath, 500 mL

Explain the phase of the cycle at mid-exhalation

Diaphragm and external intercostals are relaxing and thoracic cavity is decreasing

• Pip increases to -5

• Palv = 1

• Ptrans decreased → lungs recoil inward

• Air flows out of lungs to atm

Define work of breathing

Effort, metabolic cost to expand lung volume, move air, and quietly exhaled

What two factors affect work of breathing

Lung compliance and airway resistance

Define and explain lung compliance

The stretchability of lungs

Increasing compliance → easier to inflate. You get a substantial amount of increase of lung inflation when increasing muscular effort

Explain emphysema in lung compliance

Emphysema is floppy lung tissue where elastic recoil is reduced. No elastic recoil = no elastic fibers to pull inward → more difficult to exhale and deflate lungs

Right shift

Explain pulmonary fibrosis in lung compliance

Lung tissue is scarred and stiffer → less compliant → more effort to get air into lungs to inflate them

Explain surfactant in lung compliance

Increases lung compliance by decreasing hydrogen bonding between water molecules and decreases surface tension → easier for lungs to expand

• Prevents collapse of alveoli by releasing more surfactant in smaller alveoli to decrease its P that will make it collapse

• Released by type II alveolar cells, increased by deep breaths

Explain airway resistance in work of breathing

The larger radius the airways, the less resistance

Explain asthma in airway resistance

Bronchioles constrict → inflammation → lower radius → increased resistance

Explain emphysema in airway resistance

Elastic fibers that hold open airways are lost → bronchial radius narrows → increased resistance

Explain bronchitis in airway resistance

Inflammation and swelling of bronchioles → excessive production of mucus → airways narrow

How much metabolism does it take to breath? With COPD?

3% of total metabolism

With chronic obstructive pulmonary disease → 30% of total metabolism

Define and point out inspiratory reserve volume (IRV)

Amount of air inhaled with max effort in excess of tidal volume

Define and point out expiratory reserve volume (ERV)

Amount of air exhaled with max effort in excess of tidal volume

Define and point out residual volume (RV)

Amount of air remaining in lungs after max exhalation

Keeps alveoli inflated between breaths, mixes with fresh air

Define, point out, and equation of vital capacity

Amount of air exhaled with max effort after max inspiration

Used to assess thoracic muscle strength and pulmonary function

ERV + TV + IRV

Define, point out, and equation of inspiratory capacity (IC)

Max amount of air inhaled after a normal tidal expiration

TV + IRV

Define, point out, and equation of total lung capacity (TLC)

Max amount of air that lungs can contain

RV + VC

Define forced expiratory volume in one second (FEV1) and its fraction

Person takes max inhalation then exhales maximally as fast as possible

The fraction is the FEV1/VC x 100%

Define alveolar dead space

Volume of air that reaches alveoli but fails to participate in gas exchange due to lack of adequate blood flow → in diseased states

Explain anatomical dead space

A conducting zone volume, naturally doesn’t participate in gas exchange, usually 150 mL

When the tidal volume comes into the conducting airways, the fresh air will push the dead space air into the alveoli, so 150mL of air will be dead space while the rest is fresh air

Define + equation of minute ventilation

The total amount of air moved into and out of the lungs per minute

Define + equation of alveolar ventilation

The total amount of FRESH air moving into and out of the lungs per minute that’s available for gas exchange

Will always be less than the minute ventilation

Must match metabolism for homeostasis to be maintained

When person is maintaining homeostasis, what values of O2 are all equal

• Net O2 entering lungs

• O2 entering blood

• O2 entering tissues

• O2 burned by cells

Explain pathway of O2 movement (starting with inhalation)

O2 enters the alveoli → leaves lung capillaries at greater vol → left heart → arrives at capillaries where vol lowers → right heart → lung capillaries → leaves alveoli

Explain details of net O2 movement

• Lots of O2 is breathed out

• More O2 is needed to be carried in systemic arterial blood

When person is maintaining homeostasis, what values of CO2 are all equal

• CO2 produced by tissues

• CO2 diffused into blood

• CO2 diffusing into lungs

• CO2 breathed into air

Explain the pathway of CO2 movement (starting with production)

CO2 is made in the cells and diffused into the blood → travels to right heart at greater vol → goes to lung capillaries where CO2 is exhaled → travels to the left heart at lower vol → arrives at tissue capillaries

Explain details of net CO2 movement

• Not enough CO2 in atmosphere to inhale

• Lots of CO2 is needed in both arterial and venous blood for pH balance (buffer system with bicarbonate to maintain pH)

Equation of respiratory quotient (RQ)

= CO2 produced/O2 consumed

Doesn’t 100% match since it depends on which nutrients are being used for energy

List the 4 physical properties of gases

1. Collisions with walls determines pressure

2. Dalton’s Law

3. Only unbound molecules exert pressure

4. Henry’s Law

Explain Dalton’s Law with gases

In a mixture of gases, the pressure each gas exerts is independent of each other. The partial pressures can be added up

What percentages of gas makes up the atmosphere at sea level?

79% N2, 21% O2, 0.03% CO2

Makes up 760 mmHg atm

Explain Henry’s Law + equation

The amount of gas dissolved in liquid is proportional to the partial pressure and solubility of the gas where the liquid is in equilibrium.

• Higher pressure → dissolves more

Amount of gas = partial pressure * solubility coefficient

List the main typical gas pressures of O2 and CO2 in respiration

O2 → atm = 160 mmHg, alveoli = 105 mmHg, lungs to tissue = 100 mmHg, tissue to lungs = 40 mmHg

CO2 —> tissue to lungs → 46 mmHg, alveoli = 40 mmHg, atm = 0.3 mmHg, alveoli to tissue = 40 mmHg

List and describe factors that vary alveolar gas pressures

1. PO2 of inspired air - breathing air with low PO2 decreases alveolar PO2

2. Rate of ventricular ventilation - hypoventilation and hyperventilation

3. Rate of metabolism - increased or decreased metabolism

Explain how rate of ventricular ventilation affects alveolar gas pressures

Hypoventilation - producing CO2 faster than exhaling it → decreases PO2, increases PCO2

Hyperventilation - blowing off CO2 faster than producing it → increases PO2 → decreases PCO2

Explain how rate of metabolism affects alveolar gas pressures

Decreased metabolism → not enough production of CO2 and use of O2 → increased PO2, decreased PCO2

Increased metabolism → too much production of CO2 and use of O2 → decreased PO2, increased PCO2

Explain equilibrium in gas exchange + disease states

Normally - equilibrium occurs 1/3 length of capillary

Diseased - never reaches equilibrium due to decreased rate of diffusion

• Pulmonary fibrosis, pneumonia, congestive heart failure

Define matching of ventilation (V) and blood flow (Q) in alveoli

Making sure that each alveolus gets an appropriate amount of air and blood flow to make gas exchange as efficient as possible

Explain matching of ventilation (V) in alveoli

In poor ventilation, the alveoli receives little air but still receives blood → makes that blood O2 poor → low alveolar PO2

Pulmonary arteries will constrict so that the blood can be redirected to other alveoli with more oxygen

Explain matching of blood flow (Q) in alveoli

In low blood flow → alveolus receives lots of air but little blood → wasted ventilation → low alveolar CO2

Bronchioles will constrict to reduce airflow to that alveolus and be redirect to alveoli with better blood flow

How is ventilation-perfusion inequality responsible for drop of PO2 from alveoli to pulmonary venous blood?

Due to the effects of gravity. The lower chest will have increased perfusion but the upper chest will have decreased perfusion. The blood from the upper and lower will mix into the pulmonary vein to make it = 100 mmHg

What are the two methods of O2 transport in blood

1. Dissolved O2 due to partial pressure gradient → only 1.5% because O2 is poorly soluble

2. Bound to hemoglobin (98.5%)

Explain the hemoglobin dissociation curve

Shows how a higher PO2 contributes to a higher hemoglobin saturation

• Plateau region (60-100 mmHg) → still has high hemoglobin saturation

• Steep region (0-40mmHg) → even a small change in PO2 changes the hemoglobin saturation

Explain the features of O2 transport from alveolus to blood

O2 in alveolus → dissolved/diffused into plasma → increases PO2 → dissolved O2 binds to Fe in Hb → down pulmonary vein

PO2 in alveolus = 105 mmHg

PO2 at pulm artery = 40 mmHg

PO2 at pulm vein = 100 mmHg

Order of movement in O2 and CO2 transport

Dissolved gases always moves first, then hemoglobin

Then CO2 from bicarbonate

Explain the features of O2 transport from blood to tissues

O2 unbinds from Hb → dissolved into plasma → dissolved into ISF → dissolved into cell cytosol (<40 mmHg) → dissolved into mitochondria (< 5mmHg)

PO2 in syst arteriole = 100 mmhg

PO2 in syst venule = 40 mmHg

Explain effects of temp and pH on O2 transport

↑ temp → ↑ CO2 = ↑ H+ (acid)

• Has a right shift → less affinity and O2 release is promoted

↓ temp → ↓ CO2 = ↓ H+ (acid)

• Has a left shift → higher affinity and O2 binding is promoted

Explain effects of carbon monoxide (CO) on O2 transport

CO binds to the same site on Hb as O2 at a much higher affinity

Reduces content of O2 in blood

Shifts O2-Hb curve to the left

Can suffocate without knowing because PO2 looks normal to the chemoreceptors so you don’t gasp

Explain effects of anemia on O2 transport

Significant decreases Hb concentration of the blood → reduces O2 carrying capacity of blood

List and describe 3 methods of transport of CO2 in blood

1. Dissolved - 10% since CO2 is more soluble in plasma than O2

2. Bound to Hb - 30%, on a different site than O2

3. As bicarbonate - 30%

Explain CO2 binding to hemoglobin and blood transport

CO2 binds to the “globin” part of hemoglobin

Promoted in venous blood where unbinding of O2 makes Hb have a higher affinity for CO2

Explain transport of CO2 in blood

CO2 produced in cells → dissolved into plasma → binds to Hb/made into bicarbonate → plasma → alveoli

Explain chloride shift

Occurs in Hb with CO2. Cl- will move in while bicarbonate moves out of RBC so that the membrane potential is maintained

Explain role of carbonic anhydrase

Ensures that making CO2 into bicarbonate is fast, makes a lot, and reversible

How is Hb a H+ buffer

It can reversibly bind to H+ to keep the pH at an appropriate range

Describe hypoventilation with CO2

Hypoventilation → ↑ arterial PCO2 → ↑ [H+] → respiratory acidosis

Describe hyperventilation with CO2

Hyperventilation → ↓ arterial PCO2 → ↓ [H+] → respiratory alkalosis