Respiratory Systems

Respiration Definition
Respiration: The process of uptake of oxygen and release of carbon dioxide.
Oxygen: Final electron acceptor in aerobic cellular respiration.
Carbon Dioxide (CO₂): Waste product of aerobic cellular respiration.

Ventilation (Breathing)
Inspiration (Inhalation): Entry of air into the lungs.
Expiration (Exhalation): Exit of air from the lungs.

Types of Respiration
External Respiration: Oxygen is taken up from the lungs by the blood; carbon dioxide is released into the lungs.
Internal Respiration: Oxygen is delivered from the blood to body tissues; carbon dioxide is taken up from body tissues into the blood.

Types of Respiratory Systems
Aquatic Animals: Use direct diffusion from water or gills (thin sheets of tissue).
Terrestrial Animals: Utilize diffusion across body surface, tracheae (network of air ducts), or lungs.

Aquatic Vertebrate Respiration
Fish:

• Structure: Two rows of gill filaments stacked to maximize oxygen uptake.

• Function: Implements countercurrent exchange, resulting in 85% oxygen extraction efficiency.

Terrestrial Vertebrate Respiration
Amphibians:

• Respiration occurs through moist skin and mainly through lungs which are not as efficient as gills.
  Reptiles:

• Use lungs with small air chambers to increase surface area.
  Mammals:

• Possess lungs with even larger surface area; gas exchange occurs in alveoli.

  • Alveoli are tiny sacs improving oxygen diffusion from air to blood.
    Birds:

• Have the most efficient lungs without needing extra surface area.

• Utilize air sacs for countercurrent flow of air.

The Mammalian Respiratory System Structure
Nostrils: Filter air with hairs.
Nasal Cavity: Moistens and warms air.
Pharynx: Common passageway for food and air (throat).
Glottis: Opening to the larynx, protected by the epiglottis during swallowing.
Larynx: Voice box.
Trachea: Tube with cartilage rings to prevent collapse; contains cilia to move mucus up.
Bronchi: Tubes branching off from the trachea entering the lungs.
Bronchioles: Smaller tubes in the lungs leading to alveoli.
Alveoli: Site for gas exchange between air and blood.

Mechanics of Breathing
Breathing Process: Active pumping of air into and out of lungs.
Diaphragm: Muscle separating thoracic and abdominal cavities.
Inspiration: Diaphragm contracts, chest cavity expands, leading to decreased lung pressure (air rushes in).
Expiration: Diaphragm relaxes, decreases chest cavity volume, increasing lung pressure (air is pushed out).

Gas Exchange During Respiration
Diffusion: Main driver of oxygen and carbon dioxide exchange.
Hemoglobin:

• Oxygen transport: Carries a high amount of oxygen (O₂).

• Carbon Dioxide transport: Transports less CO₂ directly; majority is carried as bicarbonate ions (HCO₃⁻).

Health Impact: Lung Cancer
Carcinogens: Substances that cause cancer (often also mutagens).
Smoking: Responsible for 90% of lung cancer cases.

Statistics on Lung Cancer and Cigarette Consumption

• Charted correlation between cigarette consumption trends and lung cancer death rates for males and females from 1900-2010 indicating a stark increase in lung cancer related to smoking habits.

• Notable trends of increased lung cancer deaths correlating with rising cigarette consumption over the decades.

Hemoglobin is a protein found in red blood cells that is responsible for transporting oxygen from the lungs to the rest of the body and returning carbon dioxide from the tissues back to the lungs. It carries a high amount of oxygen (O₂) and transports a smaller proportion of carbon dioxide directly; the majority of carbon dioxide is carried as bicarbonate ions (HCO₃⁻).