Respiratory System

Two Zones of the Respiratory System Conductive Zone – All structures that convey air from the outside of the body to the lungs. Includes: mouth and nose, pharynx, Larynx, Trachea, Primary and Secondary Bronchioles, Tertiary and Terminal bronchioles

Two Zones Cont… Role of the Conductive Zone: Transport Air to the lungs Warm and Humidify air before it reaches Respiratory Zone (37 degrees) Filter air taken in with each breath (dust dirt) this is done by mucous lining.

Two Zones Cont… Respiratory Zone – area where gas exchange occurs. (diffusion). Includes the respiratory bronchioles, alveolar ducts, alveolar sacs.

Two zones cont… The average person has about 300 million alveolar sacs. (this is significantly reduced by conditions like Emphysema) Walls of alveoli contain numerous capillaries that absorb oxygen from alveoli and release Carbon dioxide into alveoli through diffusion.

Emphysema

Respiration Terms External Respiration – Process that occurs within the lungs and involve the exchange of CO2 and O2 Internal Respiration – Process that occurs at the tissue level where O2 and Co2 are exchanged Cellular Respiration – Process where cells use O2 to generate energy through different metabolic pathways found in the mitochondria

Mechanism of Breathing Movement of air is dependent on pressure differences (Air moves from high pressure to low pressure) Breathing is controlled by the brain stem (specifically medulla oblongata and Pons) When Diaphragm contracts it moves down and creates a greater space in the chest cavity (lower pressure when compared to the atmosphere) thus air rushes in.

Mechanism of breathing Cont… Inspiration is an active process while expiration is a passive process ( when breathing quietly but may also be active when forced breathing like vigorous exercise or blowing up a balloon)

Ventilatory volumes VE - Volume of air moved by the lungs in 1 minute (Ventilation). Influence by volume of air in each breath and number of breaths per minute VT – Volume of air in each breath (Tidal Volume, at rest 0.5L/breath, exercise 3-4L/breath) F – Number of breaths taken per minute (rest 12breaths/minute)

Cont… VE (L/min) = VT(L/breath) x f (breaths/min) With Exercise VE could be 100-200L/min

More Respiratory Terms Total Lung Capacity (TLC) = max volume of air lungs can hold Vital Capacity (VC) – Max volume of air that can be exhaled after maximal inhalation Residual Volume (RV) – Air the remains in the lungs following a maximal exhalation TLC = VC + RV

Oxygen Carrying Capacity of the Blood Small amounts of oxygen dissolve in plasma Most of oxygen binds with hemoglobin (special protein in RBC’s) In general 21.4 ml of oxygen can be carried per 100ml of blood

Carbon dioxide carrying capacity of blood 5-10% of CO2 dissolves in plasma 20% binds with hemoglobin 70-75% diffuses into RBC’s to form carbonic acid ***Regulation of blood pH (SEE OVERHEAD)

Bicarbonate System As exercise intensity increases the brain stem recognizes the increase in [H+] (created from increased anaerobic metabolism) and stimulates an increase in VE As VE increases CO2 gets blown off, thus reducing the amount of CO2 in the blood, and creating an imbalance in the system. In order to create equilibrium again in the system, H+ binds to HCO3 (in blood or released from Kidneys) to form Carbonic Acid [H2CO3]. This then further dissociates and forms more H2O and CO2. This reduces the [H+] in blood and achieves equilibrium.