Lecture- Respiratory System

State the eight functions of the respiratory system

1. Gas exchange

2. Olfaction

4. Communication

5. Blood pressure regulation

6. Platelet production

7. Blood filtration

8. Expulsion of abdominal contents

What gasses are exchanged in the lungs?

Oxygen and Carbon dioxide

What do the lungs release to help with blood pressure regulation?

Angiotensin converting enzyme

What in the lungs is responsible for making platelets

Megakaryocytes

What is the valsalva maneuver?

Forceful exhalation against a closed glottis which increases pressure within the chest and abdomen to help expel abdominal contents

1. Inhale, hold breath, contract abdominal muscles

2. Aids in childbirth, defecation, urination, vomiting

What are they key definitions of respiration?

1. Ventilation

2. External respiration

3. Internal respiration

4. Cellular respiration

What are the structures of the upper respiratory tract?

1. Nose  

2. Pharynx

3. Larynx (contains vocal cords)

What are the structures of the lower respiratory tract?

1. Trachea

2. Bronchi

3. Broncioles

4. Alveoli

Trace the flow of air from the nose to the pulmonary alveoli

1. Nose

2. Pharynx

3. Larynx

4. Trachea

5. Bronchi

6. Bronchioles

7. Alveoli

Difference between conducting versus respiratory zones

1. Conducting zone - passage of air

2. Respiratory zone - gas exchange

What are the structures of the conduction zones?

What are their functions?

1. Mucous membranes- Clean and moisten air

-Goblet cells

-Cilia

-Mucociliary escalator

2. Nasal concha/turbinates - increase surface area covered in mucous membrane

-Inferior concha contains erectile tissue

1. How often do the right and left Inferior nasal concha take turns being enlarged?

2. What happens if one side is blocked

3. What happens if this lasts several days?

1. Every 30-60 minutes

2. The other side is over ventilated

3. The epithelium transitions from ciliated columnar to stratified squamous

What are some of the structures of the respiratory zones?

What are their functions?

1. Some bronchioles

2. Alveolar sacs

-Alveolar duct

-Atrium

-Alveoli

3. Function is gas exchange

What are the cell types found in the respiratory zones?

1. Squamous (type I) alveolar cells

-95% of alveolar surface

-Gas exchange

2. Great (type II) alveolar cells

-5% of alveolar surface

-Produce surfactant

-Repair alveoli when type I cells are damaged

-Repair alveoli when type I cells are damaged

3. Alveolar Macrophage (dust cells)

-Most numerous

-Wander alveoli and associated connective tissues

-Remove dust, bacteria, loose blood cells

What are the different types of pleura?

1. Visceral- on lungs

2. Parietal- on chest wall

3. Pleural cavity “potential space” filled with pleural fluid

What does pleural fluid do?

1. Reduce friction during ventilation

2. Create a pressure gradient

3. Compartmentalization - reduce spread of infections

What muscles are involved in Inspiration?

1. Primary movers of inspiration (quiet inspiration)

-Diaphragm

-External intercostals

2. Accessory muscles for forced inspiration

-Scalenes, pectoralis minor, sternocleidomastoid

-Internal intercostals - intercartilaginous portions 

What muscles are involved in expiration?

1. Quiet Expiration

-Elastic recoil of lungs and thoracic cage

2. Forced Expiration

-Internal intercostas - costal portions

-Rectus and transversus abdominus, obliques

What are the brainstem centers that control breathing?

1.Medulla Oblongata

-Ventral respiratory group

-Dorsal respiratory group (DRG)

2.Pons

-Pontine respiratory group

What is the function of the Ventral respiratory group

1. Primary generator of rhythm of eupnea at about 12 Breaths/min

2. Contains Inspiratory (I) and Expiratory (E) neurons in a reverberating circuit

Explain the reverberating circuit of Inspiratory (I) and Expiratory (E) neurons

1. I neurons fire for about 2 seconds

-Send message through spinal cord to phrenic nerve and intercostal nerves

-Causes contraction of diaphragm and external intercostal muscles

-I neuron firing also inhibits E neurons

2. When I neurons stop firing, E neurons fire for about 3 seconds

-E neurons inhibit I neurons and diaphragm, external intercostals stop contraction

-Elastic recoil causes exhalation

What is the function of the dorsal respiratory group

1. Modifies basic rhythm  

2. Modulates VRG activity

-Alter depth

-Alter rate

Where does the dorsal respiratory group receive inputs from?

-Respiratory centers of the pons

-Chemosensory information from the medulla oblongata

-Chemoreceptors in aorta and carotid arteries

-Stretch and irritant receptors of airways

-Higher brainstem centers that allow for emotional effects

What are the central receptors of Medulla and Pons?

-Where are they concentrated?

-What are they sensitive to?

Chemoreceptors  

-Concentrated in medulla oblongata 

-Sensitive to pH (and indirectly CO₂) of CSF 

What are the peripheral receptors of the Medulla and Pons

Chemoreceptors

Stretch receptors

Irritant receptors

Where are the chemoreceptors of the peripheral receptors located?

-What are they sensitive to?

-What are the pathways they take to DRG?

Concentrated in Aorta and Carotid Arteries 

-Sensitive to pH, CO2, and O2 

-From aorta to DRG of medulla oblongata via vagus nerve 

-From carotid arteries to DRG of medulla oblongata via glossopharyngeal nerve

Where are the stretch receptors of the peripheral receptors located?

-What do they detect?

-What are they responsible for?

-What are the pathways they take to DRG?

1. Concentrated in smooth muscle of bronchi and bronchioles and in visceral pleura 

2. Detect stretch (inflation) of lungs 

3. Responsible for the inflation reflex -

-Protects against overinflation 

-Strong inhibition of I neurons 

4. To DRG of medulla oblongata via vagus nerve 

Where are the Irritant receptors of the peripheral receptors located?

-What are they sensitive to?

-What are they responsible for?

-What are the pathways they take to DRG?

1. Concentrated in epithelium of airways 

2. Sensitive to smoke, dust, pollen, chemical fumes, cold air, excess mucus 

3. Responses include: bronchoconstriction, shallow breathing, cough, breath-holding (apnea)

4. To DRG of medulla oblongata via vagus nerve 

What is the origin and output of voluntary control

1. Originates in motor control areas of cerebral cortex

2. Output to integrating centers in spinal cord via corticospinal tracts (bypass respiratory centers of brainstem)

How does flow relate to pressure differences between two areas, and to resistance?

Flow is directly proportional to pressure differences between two areas, and inversely proportional to resistance

(ex. more pressure difference=more flow

more resistance=Less flow)

What is Boyle’s law?

Pressure of a given quantity of gas is inversely proportional to its volume

(ex. When your lungs expand, volume increases and pressure drops, pulling air inside. When your chest contracts, volume decreases and pressure rises, pushing air out.)

What is Atmospheric pressure, Intrapulmonary pressure, and Intrapleural pressure? How do they relate?

1. Atmospheric pressure: Pressure of air above us (760 mmHg)

2. Intrapulmonary pressure: Pressure inside lungs  

• -0.7 mmHg compared to atmospheric pressure during quiet inhalation

• +0.7 mmHg compared to atmospheric pressure during quiet expiration

5. Intrapleural pressure: pressure between layers of pleura

• generally -3.57 mmHg compared to atmospheric pressure

Describe the pressure changes that cause Inspiration

1. Muscle contraction (diaphragm and external intercostals) causes increased volume and decreases intrapulmonary pressure

2. When intrapulmonary pressure is less than atmospheric pressure, air flows into lungs

How much air in inhaled with each breath during quite inspiration?

Around 500ml of air

Describe the pressure changes that cause Expiration

1. Elastic recoil of lungs and thoracic cage causes decreased volume and increases intrapulmonary pressure 

2. When intrapulmonary pressure is more than atmospheric pressure, air flows out of lungs 

What causes resistance (reduced air flow)

1. Diameter of bronchi and bronchioles

2. Lung compliance

Are bronchi or bronchioles more variable in diameter, why?

Bronchioles are more variable because of high muscle and low cartilage

What is bronchodilation?

What causes it?

Increased diameter

-stimulated by E and sympathetic NS

What is bronchoconstriction

What causes it?

Decreased diameter

-stimulated by histamine, parasympathetic NS, cold air, irritants

What is lung compliance?

How easily lungs expand (change in volume relative to a given pressure

What does the thin layer of water covering the epithelium of alveoli and respiratory bronchioles do?

Causes surface tension and makes lungs less compliant

What is pulmonary surfactant?

-Where is it produced

-What does it do?

-What does deep breathing do to pulmonary surfactant?

Amphipathic proteins and phospholipids

-Produced by type 2 alveolar cells (begins around 7 months of gestation)

-Disrupts hydrogen bonds and reduces surface tension

-Deep breathing helps distribute surfactant

Why is low compliance associated with stiffer lungs

Changes in tissue to scar tissue (tuberculosis, black lung disease)

What is Anatomical dead space

-How much is there?

Air that fills conducting zones

-About 150ml

What is physiological dead space?

-Air in nonfunctional respiratory zones

—scar tissue, edema, or low blood flow

How many ml is alveolar ventilation

Around 350ml

How do you calculate Alveolar ventilation rate?

Multiply respiratory rate by alveolar ventilation(~350)

Residual volume

What happens to it during inspiration?

Air remaining in lungs after expiration

-Mixes with incoming air

How many average breaths does it take to replace all pulmonary air?

About 18 (90 sec)

What does spirometry distinguish between?

Restrictive lung patterns

Obstructive lung patterns

What do restrictive lung patterns affect?

Total volume of respirations

What do obstructive lung patterns affect?

Rate of air flow in conducting zones

What factors affect the rate of diffusion

1. Distance

2. Concentration gradient (for the individual gas)

3. Area available for diffusion

2. Respiratory Membrane (70 m²  or 750 feet²)

1. Simple squamous epithelium of alveoli

2. Simple squamous epithelium of capillaries

3. Shared basement membrane

What is Dalton’s law?

The pressure of a solution of gases is the sum of the partial pressures of each gas

What is Henry’s law?

The amount of gas that dissolves in water is determined by its solubility and partial pressure

What are the variables of exchange?

1. Pressure gradients (Henry’s law)

2. Solubility (Henry’s law)

3. Membrane thickness

4. Membrane area

5. Ventilation-perfusion coupling

Is O2 or CO2 more soluble?

CO2 is about 20x more soluble than O2

What can increase membrane thickness in the lungs?

Fluid in lungs can increase the functional thickness and impact gas exchange

What is the effect of scar tissue and damage to respiratory membrane

Reduced available membrane area for gas exchange

Explain Ventilation-perfusion coupling

Air flow and blood flow need to match

-Low O2 causes vasoconstriction in pulmonary arterioles

-High O2 causes vasodilation in pulmonary arterioles

-This response is opposite the responses of systemic arterioles

What percent of O2 is dissolved is plasma vs bound to hemoglobin

-1.5% dissolved in plasma

-98.5% bound to hemoglobin

How much O2 can 4 peptides with a heme portion carry

Each can carry one O2 molecule and can hold a total of 4 O2 molecules

What is oxyhemoglobin

Hemoglobin with one or more O2 molecules bound

What is Deoxyhemoglobin

Hemoglobin with no O2 molecules bound

What does the Oxyhemoglobin dissociation curve show?

Relationship between hemoglobin saturation and PO2

What is the PO2 of oxygenated blood?

PO2 = 95mHg = 100%+ saturated

What is the PO2 of deoxygenated blood?

PO2 = 40 mHg = 75%+ saturated

How long can venous reserve sustain life?

4-5 minutes

What percent of CO2 is

-dissolved in plasma

-bound to hemoglobin and other proteins forming carbamino compounds

-converted to carbonic acid then to bicarbonate + hydrogen ions

-5%

-5%

-90%

What is the carbonic acid-bicarbonate buffer system

-why does it occur faster in RBC

-what happened to H+ and HCO₃^-

H₂O + CO₂ ↔ H₂CO₃ ↔ H⁺ + HCO₃^-

-Carbonic Anhydrase

-Most H+ binds to hemoglobin

-Most HCO₃^- is pumped out of RBC in exchange for Cl-

What is Oxygen unloading increased by?

Low PO2

High temperature

Low pH: Bohr effect

High Bisphosphoglycerate (BPG)

What is Bisphosphoglycerate (BPG) produced by?

-What increases production?

-Produced by RBC

-Production increases with fever, high thyroid hormone, testosterone, epinephrine

What does low oxyhemoglobin cause

Increased CO2 loading

-increased CO2 binding to hemoglobin

-Hemoglobin bings more H+ and shifts more CO2 to HCO3-

Are adjustments to ventilation more sensitive to

pH changes

What is a normal pH?

-what monitors it?

7.35-7.45

monitored by chemoreceptors in

•medulla oblongata (75%)

•chronic arteries and aorta (25%)

what is Acidosis?

-How does the body respond?

Blood pH is lower than 7.35

-responds by increasing ventilation

What is alkalosis?

-How does the body respond?

Blood pH is above 7.45

-Respond by decreasing ventilation

What is a normal CO2 mmHg

40mmHg

What is hypercapnia?

-How does the body respond?

CO2 above 43 mmHg

-respond with increasing ventilation

What is hypocapnia?

-How does the body respond

CO2 below 37 mmHg

-respond with decreasing ventilation

Normal O2 mmHg

95 mmHg

At what point does O2 levels begin to affect ventilation?

-Who does this usually affect?

Below 60 mmHg (hypoxic drive)

-usually affects people at high elevation, affected by emphysema, or pneumonia

How does the body anticipate the need for increased ventilation before exercise?

When motor commands are sent to the muscles via the spinal cord, there are also signals sent to respiratory centers

How does proprieties feedback affect ventilation?

Proprioceptors of muscles and joints send signals to respiratory centers

Describe the forms and effects of oxygen imbalances

1. Hypoxemic hypoxia: low arterial pO2, often caused by poor gas exchange

2. Ischemic hypoxia: inadequate blood circulation

3. Anemic hypoxia: reduced hemoglobin resulting in the inability to carry O2

4. Histotoxic hypoxia: toxins prevent delivery of O2 to tissues by altering metabolism

What causes Hypoxemic hypoxia

-High elevation

-Impaired ventilation

-Drowning

-Degenerative lung disease

What are the diseases of COPD and how do they begin?

Usually caused by smoking

-Obstructed airways

-Chronic bronchitis

-Emphysema

Describe the effects of obstructed airways caused by COPD

Reduces vital capacity, which leads to:

1. Hypoxia

• Leads to increased EPO from kidneys- resulting in polycythemia, and more blood viscosity. Left ventricle needs to work harder (enlarges and may fail)

2. Hypercapnia

3. Respiratory acidosis

Explain the effects of chronic bronchitis

1. Inflammation of lower respiratory tract

2. Extra mucus, reduced ciliary action = thick, stagnant mucus

3. This mucus gives bacteria a place to grow

4. smoking reduces the activity of macrophage in lungs

5. Reduces gas exchange (increases distance for diffusion)

Explain the effects of emphazima

1. Alveolar walls damaged= reduced surface area for gas exchange

2. Increased scar tissue= more fibrous, less elastic

-More work to exhale

-Air can be trapped in the lungs

-Results in barrel chest

-Overstretched muscles need to work even harder

-Results in 3-4 times the amount of energy to breathe

Explain how lung cancer begins, progresses, and exerts its lethal effects.

-Most often caused by smoking

-Squamous-cell carcinoma

1. The basal cells of bronchial epithelium become squamous rather than pseudostratified columnar

-Invade deeper levels and cause bleeding and scaring

2. Adenocarcinoma: originates in mucous glands of lamina propria

3. Small-cell (oat-cell) carcinoma

-Most dangerous

-Originates in main bronchi and spreads to mediastinum and metastasizes quickly