Respiratory System

Processes of the respiratory system

pulmonary ventilation, external respiration, transport of respiratory gases in the blood, internal respiration

External respiration

movement of oxygen from lungs into blood and carbon dioxide from blood to lungs

Internal respiration

movement of oxygen from the blood into tissue cells and carbon dioxide from cells into the blood

Conducting zone

moves air, consists of the trachea, bronchi, bronchioles, and terminal bronchioles

Respiratory zone

where gas exchange occurs, includes the respiratory bronchioles, alveolar ducts, and alveolar sacs

How many layers does the trachea have?

three

What is in the mucosa of the airway?

goblet cells which make mucous, cilia to move mucous and pathogens around

Why does smoking make you cough?

smoking kills the cilia, so coughing is the only way to keep mucus from accumulating in the lungs

Alveoli

tiny, hollow sacs whose open ends are continuous with the lumen of the airway

Type I alveolar cells

flat epithelial cells in a continuous layer lining most of the air-facing surfaces

Type II alveolar cells

produce surfactant

Surfactant

a detergent like substance that lowers surface tension and increases lung compliance

Why is the surface area of the alveoli so large?

permits rapid exchange of large quantities of oxygen and carbon dioxide by diffusion

What lines the alveolar surface?

water

Visceral pleura

cells lining the lung

Parietal pleura

cells lining the inside of the chest wall

Intrapleural fluid

fluid found between the two layers of the thoracic cavity

Ventilation

exchange of air between the atmosphere and alveoli by bulk flow

Flow-pressure equation

How does changing the volume of the lungs change the flow of gases?

leads to a pressure change which causes gases to flow to equalize the pressure

Boyle’s law

P_alv

pressure in the alveoli, rises and falls with breathing and determines the direction of air flow

Negative pressure breathing

when P_alv<P_atm, air flows into the lung

P_ip

pressure in the pleural cavity, fluctuates with breathing but is always 4 mmHg less than P_alv

What happens when P_ip=P_alv?

the lungs collapse

Transpulmonary pressure

transmural pressure governing the static properties of the lungs

Transpulmonary pressure equation

P_tp= P_alv - P_ip

What does transpleural pressure determine?

size of the lung

How is negative intrapleural pressure useful?

holds the lung open by putting negative pressure on the outside, puts negative pressure on the inside of the chest wall to prevent it from flailing out

Intercostals

muscles between the ribs that pull up and out

Compliance

inverse of stiffness

What is the effect of greater lung compliance?

easier to expand the lungs at any given change in transpulmonary pressure

determinants of lung compliance

stretchability of the lung tissue, surface tension at the air-water interface within alveoli

Compliance equation

What lung problem commonly occurs in premature babies and why?

their type II cells are not mature enough to produce surfactant, so the alveoli collapse and have to re-inflate

What affects airway resistance?

changes in airway radii in response to physical, neural, and chemical factors

Tidal volume

amount of air inhaled or exhaled in one breath

Residual volume

amount of air remaining in the lungs after maximum expiration

Why is residual volume important?

keeps alveoli inflated between breaths and mixes with fresh air on the next inspiration

Inspiratory reserve volume

amount of air in excess of tidal inspiration that can be inhaled with maximum effort

Expiratory reserve volume

amount of air in excess of tidal expiration that can be exhaled with maximum effort

Vital capacity

amount of air that can be exhaled with maximum effort after maximum inspiration

Vital capacity equation

VC = ERV + TV + IRV

total lung capacity

maximum amount of air the lungs can hold

Total lung capacity equation

Total capacity = RV + VC

Inspiratory capacity

maximum amount of air that can be inhaled after a normal tidal expiration

Inspiratory capacity equation

Inspiratory capacity = TV + IRV

Functional residual capacity

amount of air remaining in the lungs after a normal tidal expiration

Functional residual capacity equation

Functional residual capacity = RV + ERV

Alveolar ventilation

amount of air that can actually access the alveoli for exchange

Alveolar ventilation equation

alveolar ventilation = (TV - anatomical dead space) x respiratory rate

Minute ventilation

how much air you can introduce in a minute

Minute ventilation equation

minute ventilation = TV x respiratory rate

Why does a pressure gradient need to exist between the blood and the lungs?

so that oxygen will diffuse from the alveolus to the blood and so that carbon dioxide will diffuse from the blood to the alveolus

P_O2 in venous blood

40 mmHg

P_O2 in arterial blood

100 mmHg

P_CO2 in venous blood

46 mmHg

P_CO2 in arterial blood

40 mmHg

What determines alveolar P_O2?

percentage of oxygen in the air you breathe, rate at which you ventilate, rate at which your body consumes O₂

Equation for determining alveolar P_O2

CO₂ production or O₂ consumption/alveolar ventilation

Hypoventilation

more CO₂ is produced or O₂ is consumed than the alveoli are ventilating

Hyperventilation

alveoli are ventilating more than CO₂ is being produced or O₂ Is being consumed

Ventilation-perfusion mismatch

part of the lung is getting successfully ventilated, but not successfully receiving blood or vice versa

How is oxygen transported in the blood?

bound to hemoglobin

What subunits does hemoglobin have?

two alpha and two beta subunits

What is the partial pressure of oxygen a function of?

oxygen dissolved in plasma, not oxygen bound to hemoglobin

Cooperative binding in the blood

oxygen binding to hemoglobin initiates a conformational change that causes hemoglobin to increase its affinity for oxygen, making oxygen an allosteric modulator

Why does oxygen get into red blood cells?

It is less concentrated in the red blood cells than outside of them

What is oxygen tension like within mitochondria?

lower than the rest of the system

How do overdoses of morphine, barbituates, or alcohol affect breathing?

suppress the neurons in the ventral respiratory group and stop respiration

ventral respiratory group

regulates how many breaths you take per minute

Where are peripheral chemoreceptors for gases located?

sensory nerves near the carotid arteries, carotid arteries, aortic bodies, aorta, heart

Which gas’s chemoreceptors are more sensitive?

the carbon dioxide ones because having too much carbon dioxide is more critical than not enough oxygen

How does low arterial pressure affect ventilation?

causes hyperventilation

Hypoxia

inadequate oxygen delivery to tissues

Anemic hypoxia

poor oxygen delivery because there are too few red blood cells or abnormal hemoglobin

Ischemic hypoxia

impaired blood circulation

Histotoxic hypoxia

impaired oxygen metabolism caused by a defect in enzymes responsible for oxidative phosphorylation

Effect of cyanide on the body

causes histotoxic hypoxia

Hypoxemic hypoxia

reduced arterial oxygen due to a lack of oxygen in the air, pulmonary problems, or lack of ventilation-perfusion coupling

How does carbon monoxide cause death?

competes with oxygen for hemoglobin binding sites, and has a 200x greater affinity for binding sites

Symptoms of carbon monoxide poisoning

confusion, respiratory distress, skin color becoming cherry red, no cyanosis

Cyanosis

bluish discoloration of the skin caused by lack of oxygen in the blood

How does acclimatization to hypoxia at high altitude happen?

peripheral chemoreceptors stimulate ventilation, kidneys produce more erythropoeitin to stimulate erythrocyte synthesis, DPG shifts the curve to the right, increased capillary density in skeletal muscle, decreased plasma volume

How does DPG shift the oxygen-hemoglobin curve to the right?

facilitates oxygen unloading in the tissues

How can DPG be problematic?

rightward shift impairs oxygen loading in the lungs

How does decreasing plasma volume help with acclimatization to hypoxia at high altitudes?

causes increased concentration of the erythrocytes and hemoglobin in the blood

Functions of the respiratory system

provides oxygen, eliminates carbon dioxide, regulates blood’s pH with the kidneys, forms speech sounds, defends against microbes, influences arterial concentrations of chemical messengers by removing some from pulmonary capillary blood and producing and adding others to blood, traps and dissolves blood clots arising from systemic veins

How does temperature affect the hemoglobin curve?

lower temperatures shift it to the left, higher temperatures shift it to the right

How does acidity affect the hemoglobin curve?

high acidity shifts it to the right, low acidity shifts it to the left

How is the fetal hemoglobin curve different from the adult one?

shifted left

What does it mean when the hemoglobin curve is shifted to the left?

increases affinity, hemoglobin picks up more oxygen in the lungs but drops less off in the tissues

What does it mean when the hemoglobin curve shifts to the right?

Decreased affinity, hemoglobin picks up less oxygen in the lungs but drops more off in the tissues