Page 1

• Breathing Control during Childbirth

  • Concentration on controlling breathing can distract from pain.

  • Holding breath increases CO2 and hydrogen ions, decreases oxygen.

  • Chemoreceptors stimulated by increased CO2, leading to the need to inhale.

  • Hyperventilation can increase breath-holding time by lowering CO2 concentration.

  • Factors affecting breathing discussed in Table 19.6.

• Effects of Hyperventilation

  • Hyperventilation can lead to lowered CO2 concentration, dizziness, and loss of consciousness.

  • Lowered CO2 concentration causes respiratory alkalosis and vasoconstriction of cerebral arterioles.

  • Hyperventilating while swimming can lead to loss of consciousness and drowning.

Page 2

• Exercise and Breathing

  • Moderate to heavy exercise increases oxygen use by skeletal muscles.

  • Exercise stimulates proprioceptors and triggers joint reflex, increasing respiratory rate.

  • Blood oxygen and CO2 levels do not change significantly during exercise, but breathing rate does.

  • Alveoli contain alveolar macrophages that phagocytize airborne agents.

• Alveoli and Respiratory System

  • Alveoli are microscopic air sacs at the distal ends of respiratory tubes.

  • Alveolar pores allow air to pass between alveoli.

  • Alveolar walls consist of type II cells that secrete pulmonary surfactant.

  • Alveolar macrophages clean alveoli by phagocytizing airborne agents.

Page 3

• Respiratory Membrane Structure

  • Alveoli are associated with a network of capillaries with walls of simple squamous epithelial cells.

  • Thin basement membranes separate alveoli and capillaries.

  • Elastic and collagen fibers support alveolar walls.

  • Respiratory membrane consists of two thicknesses of epithelial cells and basement membranes.

• Gas Exchange

  • Gas exchange occurs between alveolar air and blood through the respiratory membrane.

  • Oxygen is added to the blood in the capillaries as long as breathing continues.

  • Alveolar Po2 stays relatively constant at 104 mm Hg.

  • Blood leaves alveolar capillaries with a PO2 of 104 mm Hg.

• Diffusion Through the Respiratory Membrane

  • Solutes diffuse from higher to lower concentration regions.

  • Gas diffusion depends on partial pressure gradients.

  • Gases diffuse from higher to lower partial pressure areas until equilibrium is reached.

Page 4

• Effects of High Altitude

  • Altitude sickness affects mountain climbers due to decreased oxygen levels at high elevations.

  • High-altitude pulmonary edema (HAPE) can lead to severe symptoms like headache, rapid heart rate, and cyanosis.

  • Hypoxia at high altitudes can vasoconstrict pulmonary blood vessels.

  • Regular exercise at moderate altitudes can strengthen the respiratory system.

• Impaired Gas Exchange

  • Illnesses resulting from impaired gas exchange may require treatment.

  • Breath analysis can reveal substances like alcohol, acetone, and markers of kidney, digestive, and liver diseases.

  • Frequency combs can detect various compounds in exhaled breath, providing health clues.

• Practice Questions

  • Describe the structure of the respiratory membrane.

  • Explain the factors causing oxygen and carbon dioxide movement across the respiratory membrane.

  • Diseases like pneumonia can harm the respiratory membrane, affecting gas exchange.

Disorders That Impair Gas Exchange

• Pneumonia:

  • Symptoms: rapid and shallow breathing, chest pain, high fever.

  • Caused by bacteria infecting lower respiratory structures.

  • Treated with antibiotics.

• Atelectasis:

  • Definition: collapse of a lung or part of it, leading to collapse of blood vessels.

  • Causes: obstruction of respiratory tube, inhaled foreign object, excess mucus secretion.

• Acute Respiratory Distress Syndrome (ARDS):

  • Special form of atelectasis where alveoli collapse.

  • Causes: pneumonia, near drowning, shock, sepsis, aspiration of stomach acid.

• Tuberculosis:

  • Caused by Mycobacterium tuberculosis.

  • Formation of fibrous tissue around infected areas.

  • Treatment with various drugs.

Gas Transport

• Oxygen Transport:

  • Hemoglobin carries over 98% of oxygen in blood.

  • Oxygen binds to iron in hemoglobin, forming oxyhemoglobin.

  • Factors affecting oxygen release: PO2 levels, acidity, temperature.

• Carbon Monoxide (CO):

  • Toxic gas that binds to hemoglobin, preventing oxygen delivery.

  • Treatment involves administering high partial pressure oxygen.

• Carbon Dioxide Transport:

  • Generated during cellular metabolism.

  • Carried in blood as dissolved CO2, bound to hemoglobin, or as bicarbonate ions.

• Influences on Oxygen Release:

  • Increased Pco2, acidity, and temperature enhance oxygen release to tissues during exercise.

Page 7

• Carbon Dioxide Transport

  • Carbon dioxide bonds with amino groups of hemoglobin molecules.

  • Oxygen and carbon dioxide do not directly compete for binding sites.

  • Carbon dioxide binding hemoglobin forms carbaminohemoglobin.

  • Bicarbonate ions form the most important CO2 transport mechanism.

  • Blood carries oxygen through oxyhemoglobin.

Page 8

• Carbon Dioxide Transport Mechanisms

  • Deoxyhemoglobin is generated in systemic capillaries.

  • Bicarbonate ions diffuse out of red blood cells into the blood plasma.

  • Chloride shift maintains ionic balance between red blood cells and plasma.

  • Carbonic anhydrase catalyzes the formation of carbonic acid from hydrogen and bicarbonate ions.

Page 9

• Carbon Dioxide Transport Process

  • Carbon dioxide is carried in blood plasma in dissolved state, bound to hemoglobin, or as bicarbonate ions.

  • Chloride shift maintains electrical balance between ions in red blood cells.

  • In the lungs, carbon dioxide diffuses from blood into alveoli.

Page 10

• Respiratory System Changes with Age

  • Muscle Weakness and Diaphragm Dependency

    • Fibrous connective tissue replaces smooth muscle in bronchioles.

    • Breathing relies more on the diaphragm as muscles weaken.

  • Decrease in Vital Capacity

    • Vital capacity peaks at age forty and may drop by a third at seventy.

  • Challenges in Lung Function

    • Difficulty in keeping fresh air in lungs due to thinning bronchiole walls.

    • Residual air trapped in lower lung portions.

  • Effects of Aging on Breathing

    • Widening of bronchioles and alveolar ducts increases dead space.

    • Maximum minute ventilation decreases around age thirty.

Life-Span Changes

• Microscopic Changes in Aging

  • Alveoli and Gas Exchange

    • Alveoli decrease in number and surface area with age.

    • Collagen increase and elastin decrease affect gas exchange efficiency.

  • Impact of Environmental Factors

    • Pollution and smoking lead to respiratory issues like bronchitis and emphysema.

    • Long-term exposure to workplace particulates raises respiratory illness risk.

  • Changes in Lung Protection

    • Ciliated epithelial cells decrease, mucus thickens, and macrophages lose efficiency.

    • Slowing of air flow and increased susceptibility to infections.

Page 19.7

• Influence of Environment and Aging

  • Effort Required for Breathing

    • Calcification of cartilage and skeletal shifts increase breathing effort.

  • Risk of Respiratory Infections

    • Changes in alveoli decrease efficiency in gas exchange