Chapter 9: Respiration

Inspiration

- Breathing in - Active process - Involves diaphragm and external intercostal muscles. - Larger volume

Expiration

- Breathing out - At rest, passive process - The inspiratory muscles relax and the elastic tissue of the lungs recoils, returning the thoracic cage to its smaller, normal dimensions.

Pulmonary Diffusion

- Gases diffuse along a pressure gradient, moving from an area of higher pressure to one of lower pressure. -Thus oxygen enters the blood and carbon dioxide leaves it.

Partial P gradient

- Most important factor for determining gas exchange - Drives gas diffusion - Without gradient, gases in equilibrium, no diffusion

Oxygen Exchange

- Oxygen diffusion capacity increases as you move from rest to exercise. - When your body needs more oxygen, oxygen exchange is facilitated.

Fick's Law

- Rate of diffusion proportional to surface area and partial pressure gas gradient - PO2 gradient: 65 mmHg - PCO2 gradient: 6 mmHG

Carbon Dioxide Exchange

- The pressure gradient for CO2 exchange is less than for O2, but carbon dioxide's membrane solubility is 20 times greater than that of oxygen, so carbon dioxide crosses the membrane easily, even without a large pressure gradient.

The Respiratory Zone

- The respiratory zone consists of the respiratory bronchioles, the alveolar ducts, alveolar sacs, and the alveoli. - The alveoli are the actual site of gas exchange between the pulmonary system and the cardiovascular system.

The Conductive Zone

- The structures from the nose or mouth to the terminal bronchioles comprise the conductive zone. - The primary role of the conductive zone is to transport air. - Because no gas exchange takes place here, this zone is also called anatomical dead space. - The second important role is to warm an humidify the air. - The third role is to filter the incoming air.

Expiration

Diaphragm and ribs return to normal positions decreasing volume of thoracic cavity; air moves out of lungs.

Inspiration

Flattening of diaphragm and rib elevation increases volume of thoracic cavity; air moves into lungs.

Ventilation During Exercise

Forced or labored inspiration and expiration are active processes, dependent on muscle actions.

Henry's Law

Gases dissolve in liquids proportion to partial P - Also depends on specific fluid medium, temperature - Solubility in blood constant at given temperature

Hyperpnea

Increased pulmonary ventilation that matches an increased metabolic demand, such as during exercise.

Hyperventilation

Increased pulmonary ventilation, especially ventilation that exceeds metabolic requirements; carbon dioxide is blow off, leading to a decrease in its partial pressure in arterial blood.

Dyspnea

Labored of difficult breathing

Eupnea

Normal respiration rate and rhythm.

Respiratory Cycle

One inspiration and expiration

Dalton's law

Partial pressure = Total pressure (mmHg) x fraction of the gas - Pg = Pb x Fg

Pulmonary Diffusion

Process by which gases are exchanged across the respiratory membrane in the alveoli.

Perfusion of the Lung

Pulmonary circulation, especially capillary blood flow.

Pulmonary Circulation

Serves the external respiratory function

Bronchial Circulation

Supplies the internal respiration needs of the lung tissue itself. Part of the systemic circulation.

Minute Ventilation or Minute Volume

The amount of air inspired or expired each minute, or the pulmonary ventilation rate per minute; calculated as tidal volume times frequency of breathing.

Residual Volume (RV)

The amount of air left in the lungs following a maximal exhalation.

Tidal Volume

The amount of air that is inspired or expired in one breath.

The Respiratory Membrane

The amount of gas exchange that occurs across the membrane primarily depends on the partial pressure of each gas, though gas solubility and temperature are also important.

Arteriovenous Oxygen Difference (a-vO2diff)

The difference between the amount of oxygen originally carried in arterial blood and the amount returned in venous blood.

Internal Respiration

The exchange of gases between the blood and the tissues at the cellular level.

External Respiration

The exchange of gases between the lungs and the blood.

Vital Capacity (VC)

The greatest amount of air that can be exhaled following a maximal inhalation.

Total Lung Capacity (TLC)

The greatest amount of air that the lungs can contain.

Partial Pressure of a Gas

The pressure exerted by an individual gas in a mixture; determined by multiplying the fraction of the gas by the total barometric pressure.

Pulmonary Ventilation

The process by which air is moved into and out of the lungs.

Hemoglobin (Hb)

The protein portion of the red blood cell that binds with oxygen, consisting of four iron-containgin pigments called hemes and a protein called globin.

Percent Saturation of Hemoglobin (Sbo2%)

The ratio of the amount of hemoglobin combined with oxygen to the total hemoglobin capacity for combining with oxygen, expressed as a percentage; indicated generally as Sbo2% or specifically as SaO2% for arterial blood or as Sv02% for venous blood.

Structure of the Pulmonary System

The respiratory system consists of two major portions: 1. The conductive zone, which transports the air to the lungs 2. The respiratory zone, where gas exchange takes place.

Oxygen Dissociation

The separation or release of oxygen from the RBCs to the tissues.

Diffusion

The tendency of gaseous, liquid, or solid molecules to move from an area of higher concentration to an area of lower concentration by constant random action.

Cellular Respiration

The utilization of oxygen by the cells to produce energy.

Alveolar ventilation

The volume of air available for gas exchange; calculated as tidal volume minus dead space volume time frequency.