Respiratory System

1. Ventilation (breathing)
2. Gas exchange(lungs)
3. Oxygen utilization (cellular respiration)

Internal and external respiration

Diffusion determines the direction of gasses from an area of high to low concentration.

Structure

Respiratory zone includes area of gas exchange.

Gas exchange at alveoli.

Alveoli attached to brochioles.

Conduction zone is where the air goes.

Warms, filter, clean, and humidifies air.

Macrophages and cilia/mucus clean lungs.

Brochioles go to bronchi

Go to trachea (in front of esophagus)

Through glottis at Larynx (Adam's apple)

Go to Pharynx

Nose and mouth.

Thoracic Cavity

Above the diaphragm

Parietal pleura lines the cavity

Viseral pleura covers the lungs.

Between pleura is intrapleural space and is potential space in healthy person.

Intrapulmonary and intrapleural pressures

When atmospheric pressure is greater than intrapulmonary pressure air goes in lungs.

Opposite for expiration.

Intrapleural pressure is lower than intrapulmonary pressure and lungs are snug on thoracic cavity.

Chest wound will equalized intrapleural pressure and atmospheric pressure and lung will collapse.-

Boyle's Law

Pressure of gas is inversely proportional to its volume.

Volume of lungs determines pressure of gas.

Physical Properties of the Lung

Compliance: ability to stretch.

ΔV/ΔP: Lung volume/transpulmonary pressure

Pulmonary fibrosis decreases compliance

Elasticity: recoil ability

Protein elastin

Surface Tension

In alveoli fluid absorbed by osmosis by active transport of Na+ in.

Fluid secretion driven by active transport of Cl-out.

Cystic fibrosis linked to Cl- transporters.

The surface tension of aveoli does not collapse because of Surfactant.

Surfactant and Respiratory Distress Syndrome

Dipalmitoyl lecithin (phospholipid)

Goes in between water molecules reducing surface tension (caused by hydrogen bonds between water molecules).

Type II alveolar cells produce surfactant late in fetal life.

No surfactant = collapsed lungs

Respiratory Distress Syndrome (RDS).

ARDS occurs in septic shock

Inflammation caused permeability reduces compliance and surfactant.

First breath takes 20 times the effort of the next breath.

RDS is always that hard.

Breathing

Inspiration and Expiration

Between bone part of ribs

External intercostal muscles

Internal intercostals muscles

Between rib cartilage (midline of body)

Parasternal intercostals

Inspiration: Diaphram goes down and contracts.

External and parasternal intercostal muscles contract lifting rib cage.

Other muscles get involved too: scalenes, pectoralis minor, sternocleidomastoid muscles.

Pressure in intrapulmonary space lowers, and air rushes in.

Expiration is passive. Pressure increases in lungs due to volume change.

Internal intracostal muscles contract and abdominal muscles contribute.

Pulmonary Function Tests

Spirometry: blow air into closed system.

Lung Volumes and Capacities

Capacity is two or more lung volumes.

Tidal volume: amount of air expired in each breath

Vital Capacity: the most air that can be expired after max inhalation.

Vital capacity= inspiratory reserve volume(most you can inhale) + tidal volume + expiratory reserve volume(most you can exhale).

Tidal volume x breath per minute =total minute volume. Increases during exercise.

Dead space is air that is in conduction zone and it has a lower oxygen concentration.

Increasing tidal volume is an adaptation to exercise and high altitude because an increase in tidal volume increases the amount of fresh air to the alveoli.

Restrictive and Obstructive Disorders

Diagnosis of disease using spirometry.

Restrictive disorders (pulmonary fibrosis)

Vital capacity is reduced. Expiration is not affected

Obstructive disorder (asthma)

Vital capacity is fine. Expiration is reduced Forced expiratory volume(FEV) or (FEV1)

FEV1 decreases on smoggy days. Smoking decreases FEV1 as does age.

Pulmonary Disorders

Asthma: Dyspnea, wheezing.

Inflammation, brochioconstriction

Allergic reaction where IGE produced, exercise, or cold,dry air, asprin.

Histamine, leukotrienes.

Treatment: Stop leukotreine production, stop inflammation, epinephrine  B2-adrenegic receptor (terbutaline).

Emphysema

Fewer/larger aveoli.

Decreased surface area for gas exchange.

Smokers

Cigarette smoke stimulates macrophages to secrete protein digesting enzymes that destroy lung tissue.

Genetics can cause this disease also.

Chronic Obstructive Pulmonary Disease (COPD) caused by emphysema, asthma, and chronic bronchitis.  Cause respiratory failure.

5^th leading cause of death in US.

Other complications:

Edema

Inflammation,

Hyperplasia

Pulmonary fibroisis

Pneumonia

Pulmonary emboli

Heart failure

Pulmonary Fibrosis

Parts of lung disrupted by fibrous connective tissue proteins

Black Lung from coal dust.

Gas Exchange in Lungs

Dalton 's law says you sum all the partial pressures(PP) of each gas to get total pressure of gas.

PO2

At altitude PP of gas decreases.

Under ocean PP increased.

Atmospheric pressure x % of gas  and take into account PPH2O and gas exchange in aveoli.

PP of Gasses in blood

Solubility of gas in fluid

Temperature of fluid

Partial pressure of gas

Measuring blood gas

Oxygen electrode

Standardize to PO2

Measure dissolved O2 (about 0.3ml/100ml blood)

Po2 and Pco2

Useful for diagnosing lung disease, surgery, or premature baby care.

Breathing oxygen can decrease oxygen diffusion rate.

Pulmonary circulation and Ventilation/perfusion ratio

Pulmonary circuit has low pressure and low resistance.

Pulmonary arterioles constrict when low PO2.

Shunts blood away from aveoli that are not working well.

Extreme mismatches of ventilation/perfusion ratio show up in lung disorders.

High PP disorders

Atmosphere increases by 1 (or 760 mmHg) for every 33 ft below sea level.

Oxygen toxicity

Oxidation of enzymes and nervous system disorders occur over 2.5 Atm. Too much oxygen  can be bad. Oxygen is diluted for divers.

High oxygen 2-3 Atm. Is sometimes used to treat carbon monoxide poisoning, decompression sickness, crush injury, gas gangrene where it is beneficial.

 Nitrogen Narcosis

Too much nitrogen dissolved in blood.

Dizziness and drowsiness.

Decompression Sickness

Nitrogen gas can turn into bubbles because the pressure decreases as you ascend from the deep.

Can block blood channels and cause pain known as "bends."

At altitude sudden loss of pressurized cabin has the same effect.

Regulation of Breathing

Voluntary and involuntary control of breathing.

Autonomic breathing controlled by PCO2, pH and PO2.Medulla Oblongata and cerebral cortex involved.

Brain Stem

Medulla Oblongata and Pons

Rhythmicity center has I and E neurons

I neurons inhibited by E neurons.

Pacemaker neurons…

Rhythmicity center controlled by Pons.

Apneustic center promotes inspiration

Pneumotaxic center blocks inspiration.

Chemoreceptors respond to PCO2, pH, PO2

Central in medulla oblongata.  (indirectly through CO2)

Peripheral at aorta and carotid arteries. (blood H+ levels )

Send information to  medulla via vagus and glossophryngeal nerve.

CO2 + H2O --H2CO3--H+ + HCO3-

CO2 can cross blood brain barrier by sneaking into cerebrospinal fluid.

Too much oxygen causes cerebral vasoconstriction.

Causes acidity in brain, and too much breathing.

Breath into paper bag.

PO2 has a slight effect on breathing only when PCO2 has been modified by high altitude or breathing O2 or emphysema.

SIDS may be caused by failure of respiratory control center.

Pressure of gasses and receptors

Many receptors can affect ventilation.

Unmyelinated C fibers.

Hemoglobin

4 subunits

2 alpha

2 beta

Each with heme group that can bind oxygen.

Each RBC can carry over 1 billion oxygen molecules

Hemoglobin can be oxidized and not be able to carry oxygen (rare) or it can bind with CO.

Anemia is not enough hemoglobin

Body makes more hemoglobin at high altitude.

Erythropoietin, from kidney,  controls hemoglobin and RBC production.

Also controlled by androgens.

PO2, pH, and temperature affect loading and unloading of hemoglobin.

22% of O2 unloaded at tissues.

More unloading occurs during exercise.

pH and temperature changes causes shift of curve.

2,3 DPG a side product of glycolysis promotes unloading of oxygen.

Fetal Hemoglobin

Has gamma chain instead of B chains.

Can't bind 2,3 DPG and has higher affinity for oxygen than mom's hemoglobin.

Sickle Cell anemia-

valine position 6 instead of glutamic acid.

Thallassemias

Myoglobin has one heme and a higher affinity for oxygen than hemoglobin.

Carbon Dioxide Transport

Carbonic anhydrase

Inside RBC becomes + due to H trapping

Attracts inward movement of Cl-

Chloride shift.

Body will attempt to maintain homeostasis through ventilation or physiological compensation of kidneys etc.

Exercise and High Altitude

Ventilation matches effort.

1)       nerves

2)       chemicals

Trained athletes can raise their lactic acid threshold due to training effect, increased mitochondria, Kreb's cycle enzymes, better blood delivery.

At altitude changes occur

1)       Changes in ventilation

2)       Hemoglobin affinity

3)       Hemoglobin concentration

NO is higher at altitude and may improve oxygenation via vasodilation.