Bio Lung 2

Introduction to Respiration and Gas Exchange

• Respiration includes inhaling oxygen and exhaling carbon dioxide (CO2).

• Importance of oxygen uptake: essential for cellular respiration.

• Water is a major component of the body (70%).

CO2 and its Role

• Carbon dioxide, a waste product of cellular respiration, is not harmful on its own.

• CO2 can result from lactic acid fermentation in muscle cells.

• CO2 reacts with water in the presence of carbonic anhydrase (an enzyme produced by red blood cells) to form carbonic acid.

• This reaction is reversible, essential for maintaining blood pH.

pH Regulation

• Excessive CO2 production causes blood pH to drop, leading to acidosis.

• Lack of CO2 can raise blood pH, causing alkalosis.

• Both conditions can be harmful to proteins, including hemoglobin (Hb).

Hemoglobin Function

• Hemoglobin is a protein made up of four polypeptides (two alpha and two beta subunits), each with a heme group for oxygen binding.

• Hemoglobin also binds CO2 and H+ ions due to the acid-base balance.

• Binding dynamics: the unloading/loading cycle in tissues helps regulate oxygen delivery to cells.

Gas Exchange Mechanics

Processes in Tissue vs. Lungs

• In Tissues: Hemoglobin unloads O2 and loads CO2 based on concentration gradients (high CO2 in tissues, low in blood).

• In Lungs: Hemoglobin loads O2 (high concentration in the alveoli) and unloads CO2 (high concentration in the blood).

• Uses the concept of partial pressure for the diffusion of gases.

Breathing Mechanics

• Air travels through the conducting zone (nose → pharynx → larynx → trachea → bronchi → terminal bronchioles) which does not involve gas exchange.

• Gas exchange occurs in the alveoli, where oxygen enters the bloodstream and carbon dioxide is expelled.

Structure of the Lungs

• Right lung: three lobes; left lung: two lobes plus the cardiac notch.

• The diaphragm separates the thoracic cavity from the abdominal cavity and aids in breathing.

• The trachea is reinforced with C-shaped cartilage, allowing flexibility and preventing choking.

Breathing Pathway

1. Inhale through nose or mouth → pharynx → larynx → trachea → bronchi → bronchioles → alveoli.

2. Alveoli are surrounded by capillaries facilitating gas exchange.

Surfactant and Alveolar Function

• Alveoli have type I and type II cells; type II cells secrete surfactant to reduce surface tension and prevent collapse.

• Surfactant is essential for maintaining the structure of alveoli and optimizing gas exchange.

Regulation of Breathing

Control Mechanism

• Breathing is controlled by the medulla oblongata in response to changes in CO2 and O2 levels in the blood.

• Increased CO2 levels signal the need for increased respiration.

Factors Affecting Respiratory Rate

• Body temperature, physical condition, emotional state, and age can influence respiratory rate.

• Gender and physical fitness also play roles.

Oxygen and Carbon Dioxide Transport

• Oxygen is primarily transported bound to hemoglobin (oxyhemoglobin) and a small amount dissolved in plasma.

• Most CO2 is transported as bicarbonate in the blood.

• The efficiency of these processes is critical for maintaining homeostasis.

Respiratory Pathologies

Emphysema and Bronchitis

• Emphysema: damage to elastic fibers, difficulty exhaling, leads to hypoxia and acidosis.

• Chronic bronchitis: inflammation and mucus hypersecretion cause airway obstruction, increased risk of infections.

Summary of Key Concepts

• Understanding gas exchange, hemoglobin function, and the mechanics of breathing is crucial for grasping respiratory physiology.

• The balance of CO2 and oxygen levels is vital to maintaining blood pH and overall health.