Gas Exchanges in the Body

Internal & External Respiration

Events #2 & 4

Dalton’s Law Used to

determine the individual pressures of each gas in a mixture of gases

Based on % of total of 760 mmHg of total atmospheric pressure

Dalton’s Law

Gas exchanges that occur: Between the blood and the alveoli AND Between the blood and the tissue cells Takes place by simple diffusion Depends on partial pressures of oxygen &

carbon dioxide that exist on opposite sides of the exchange membrane (Dalton’s law of partial pressures)

Always flowing from high to low

Henry’s law

states that the solubility of a gas in a liquid is directly proportional to the pressure of that gas above the surface of the solution (IOW: the higher the pressure of the gas, the more gas will be shoved into the liquid thus increasing solubility)

Henry’s law Solubility (of a gas) and partial

pressure have a direct relationship

Solubility Coefficients

The solubility coefficient of the gas also affects this process – the higher the #, the more the gas “likes” to dissolve into a liquid (based on molecular structure, etc.)

Each gas will dissolve in a liquid in proportion to the ratio between its partial pressure gradient and its solubility coefficient CO2 = .57

O2 = .024

N2 = .012

2nd Law of Thermodynamics

Solubility & temperature have an inverse relationship.

Increase in temperature causes increase in kinetic energy causes more molecular motion which allows molecules to break the intermolecular bonds and escape from solution

And vice versa

2nd Law of Thermodynamics

Factors that Influence:Ratio Relationships

Partial pressure gradients and gas solubilities Oxygen = has low

solubility but steep partial pressure gradient (105 mmHg in alveoli – 40 mmHg in blood = 65 mmHg pressure gradient)

Carbon dioxide = has solubility ~20x greater than oxygen but partial pressure gradient is only 5 mmHg

Factors influencing internal & external respiration

Partial pressure gradients and gas solubilities Due to the ratios of solubility coefficients and

pressure gradients: ~Equal amounts of gases are exchanged

Factors influencing internal & external respiration

Thickness of respiratory membranes 0.5 to 1.0 micrometers edematous (swollen) tissue can be caused by

congestion and pneumonia - hinders diffusion leading to hypoxia oxygen deprivation

Factors influencing internal & external respiration

Surface Area 50-70 square

meters for gas exchange

Emphysema or cancerWalls of alveoli

break downLess surface

area for gas exchange

Control of Respiration

Nerves The phrenic &

intercostal nerves transmit impulses to the respiratory muscles Irritation to phrenic

nerve is responsible for hiccups (spasm of diaphragm muscle)

Neural centers are located in medulla & pons

Respiration Rate Terms

Eupnea = normal respiration rate Approx 12-15 breaths per min

Hyperpnea = higher than normal rate Apnea = No rate Dyspnea = general term for abnormal rate Physical factors, conscious control,

emotional factors, and chemical factors all influence rate & depth of breathing.

Hyperventilation

Deep & rapid respiration, too much CO2 is vented out of the body so:

Not enough acid productionH2O + CO2 = H2CO3 (carbonic acid)

Respiratory alkalosis results Treatment: trap the CO2 and

rebreathe it till breathing returns to normal

Hypoventilation Slow & shallow respiration with not adequate expiration

so CO2 is not vented out of the body

Production of excess acid

H2O + CO2 = H2CO3 (carbonic acid)

Respiratory acidosis results

Usually caused by disease process:

COPD

Asthma

Obesity

Trauma

Pneumonia

Disorders of Respiratory System

Chronic Bronchitis

Symptoms: inflammation of mucosa – chronic mucus production

Normal

Bronchitis

EmphysemaBreathing is very labored due to lack

of alveolar recoilEnd stage: Alveolar walls collapse =

loss of surface area so less gas diffusion

Membranes thicken so decrease in diffusion eventually

4 features in common

Both emphysema and chronic bronchitis have: Smoking history Dyspnea = air hunger due to dysfunctional

breathing Coughing & pulmonary infections Will develop respiratory failure, hypoxia,

acidosis

Lung Cancer

Basic Info 1/3 of all cancer deaths are due to lung

cancers 90% have a smoking history Metastasizes VERY rapidly due to vascularity

of lungs

Metastasis

3 types of lung cancer Read the article in the textbook on page

420 about smoking and lung cancer. Then continue on to the next slides to

learn about: Squamous cell carcinoma Adenocarcinoma Oat cell (small cell) carcinoma

Be sure you learn where these cancers begin and what they look like (test question diagrams!)

Squamous cell carcinomaBegins in larger

bronchi & bronchioles

Forms masses that have bleeding cavities within them

Adenocarcinoma Nodules that

develop in peripheral areas of lung

Develop from alveolar cells & bronchial glands

Small cell carcinoma

Originate in primary bronchi

Grow into small grape like clusters in mediastinum

Very aggressive cancer

Treatments Resection of diseased portion of lung

(thoracotomy) Radiation therapy Chemotherapy

Thoracotomy/lung resection

Cystic Fibrosis• Genetic disorder – recessive• Causes oversecretion of thick mucus that

clogs respiratory passages• Impairs food digestion by clogging ducts

that secrete enzymes• Multiple other organs are affected

Cystic Fibrosis

SIDS - Sudden Infant Death Syndrome

• Sudden, unexplained death of an infant less than 1 year old

• Possibly caused by brain abnormalities that control respiration, heart rate, or consciousness

• Environmental factors to reduce risks – sleep on back not on stomach, firm crib with no blankets or stuffed animals or pillows

• Sudden infant death syndrome (SIDS): Risk factors - MayoClinic.com

Asthma

• Chronically inflamed hypersensitive bronchial passageways

• Bronchoconstriction of passageways in response to allergen, temperature changes, & exercise

• Can be managed with medication

Hyperbaric Conditions

Hyperbaric oxygen chambers – designed to force greater amounts of oxygen into patient’s blood

Treats tissues affected by poor circulation

How Hyperbaric Treatment Works

Patient breathes in regular air while body is under pressure

Increased pressure means increased solubility of gases (incl oxygen)

More oxygen in blood benefits treatment of certain conditions

HBOT used to treat:

Tetanus

Gangrene

Migraines

Slow healing wounds

Burns/skin grafts

Stroke

Autism

Traumatic Brain Injury

Decompression Sickness

Cerebral Palsy

Multiple Sclerosis

Fibromyalgia

Many other conditions

Scuba Diving

The Physics of Diving - Scuba Gas Laws

• As you go down in depth, the water puts pressure on your body

• Increased pressure = increased solubility of inhaled gases into the blood

Scuba Diving

• As you come up at the correct rate, the pressure decreases slowly

• So the solubility decreases slowly

• So the gases come out of the blood

• And you can exhale them

Scuba Diving

• If you come up too rapidly, the pressure decreases rapidly

• So the solubility decreases rapidly

• So the gases come out of the blood too fast to exhale them properly

• The excess gas bubbles can collect in joint spaces, arteries, tissues, etc. causing coronary, pulmonary, or brain embolisms

Nitrogen Narcosis

• As you descend under the water, the pressure on your body increases, so more nitrogen and oxygen dissolve in your blood. Most of the oxygen gets consumed by your tissues, but the nitrogen remains dissolved.

• Excess nitrogen causes a feeling of euphoria similar to laughing gas – impairs judgement

Decompression Sickness

• DCS arises when the pressure gradient for nitrogen leaving the tissues is so great that large bubbles form in venous circulation

• DCS symptoms are wide-ranging: from skin mottling to mild tingling in the hands or feet to shock and death

• Recompression in hyperbaric chamber is only effective treatment

High Altitude Sickness

• The higher the altitude, the less the amount of oxygen present in the air.

• Headache and difficulty breathing are initial symptoms.

• HA pulmonary edema and HA cerebral edema are life threatening symptoms.

• Body responds over time by increasing erythropoiesis to give body greater oxygen carrying capacity.