Ventilation - moves air to and from alveoli. Functions of Respiratory System Surface area for gas exchange between air and circulating blood. Helps regulate pH of body fluids. Permits vocal sounds.

External nares

Upper Respiratory System Lower Respiratory System Functions to conduct air to site of gas exchange. Nose Nasal cavity Pharynx (throat) Larynx Conditions inspired air: Trachea Bronchi Bronchioles Alveoli – gas exchange! Filter Warm Humidify

Vocal Folds

Respiratory Epithelium

Air Moves Down its Pressure Gradient Inspiration – Air moves from outside into lungs as pressure in the thoracic cavity decreases (thus, volume increases). Expiration – Air moves from lungs to outside as pressure in the thoracic cavity increases (thus, volume decreases).

Muscles of Ventilation Eupnea – Quiet breathing at rest. Inspiration: Diaphragm and External intercostals. Expiration: No Muscle Contraction! increases volume elastic recoil * Metabolic cost of breathing normally ~ 3% BMR

Muscles of Ventilation Forceful Breathing – e.g., during exercise. Inspiration: Diaphragm, External intercostals, Expiration: Internal intercostals and Abdominal muscles.

3 Important Pressures 2. Alveolar Pressure 1. Atmospheric Pressure 3. Intrapleural Pressure

Alveolus

Alveoli consist of 3 types of cells 1) Alveolar Type I cells – thin (epithelium) that makes the ‘walls’ of alveoli for gas exchange. 2) Alveolar Type II cells – release surfactant which make lungs more Compliant. 3) Alveolar Macrophages – protects the alveolar surface. Release trypsin.

Alveoli also have elastic fibers Elastic recoil - pushes air out (assists ventilation). Capillaries cover 90% of alveolar surface.

Pulmonary Elasticity and Compliance

Partial Pressure Gradients Air is mixture of Gases –N2–N2 –O2–O2 –CO 2 Q: Calculate the P O2 if P ATM is 380 mmHg? Q: What is the P O2 if P ATM is 760 mmHg? P CO2 ? Partial Pressure - pressure of a single gas in a mixture of gases. = 79% = 21% = 0.03%

Partial Pressure gradient: Factors influencing how a gas dissolves in liquid Temperature: Solubility:

O 2 Movement: –Air to blood –Blood to cells CO 2 Movement: –Cells to blood –Blood to air An individual gas in a mixture moves down its Partial Pressure Gradient

How is O 2 Transported ? 2% is dissolved in plasma. 98% in carried on Heme portion of hemoglobin (Hb).

How is CO 2 Transported ? ~ 10% dissolved in plasma. ~ 30% bound to globin portion of Hb. ~ 60% as HCO 3 -, (bicarbonate buffer)

O 2 -Hb Saturation Curve

* P CO2 : * 2,3-DPG: * Temperature: * pH of surroundings: Factors that Shift the Hb-O 2 Saturation Curve

Airway Resistance Diameter Blockage (e.g., mucous) Bronchoconstriction Bronchodilation Air Flow =  P/R ∆P is? R is?

For best gas exchange need: - Wet surface - Thin epithelia - Little ECF Some Diseases: Emphysema Asthma Fibrotic Lung Pulmonary edema - Large surface area Bronchitis

Vital capacity Inspiratory capacity Functional residual capacity Tidal volume Inspiratory reserve volume Expiratory reserve volume Residual volume Volumes Capacities