Human Respiratory System

• The human respiratory system facilitates effective gas exchange, which supplies oxygen to the body and removes carbon dioxide.

Components of the Respiratory System:

• Nose/Nasal Cavity: Filters, warms, and moistens inhaled air and traps particles via mucus and cilia.
• Pharynx (Throat): Passageway for air from nose to larynx, directing food to the esophagus and air to the trachea; involved in swallowing.
• Larynx (Voice Box): Contains vocal cords, produces sound, and prevents food/liquids from entering the trachea.
• Trachea (Windpipe): Provides a clear path for air to the lungs and filters particles/pathogens with cilia and mucus.
• Bronchi: Direct air from the trachea into the left and right lungs.
• Bronchioles: Smaller branches of the bronchi which distribute air to the alveoli.
• Alveoli: Tiny sacs facilitating oxygen absorption into the blood and carbon dioxide removal from the blood.
• Lungs: House the alveoli to support gas exchange between blood, oxygen, and carbon dioxide.
• Diaphragm: Muscle that contracts/relaxes to change lung volume during breathing.
• Intercostal Muscles: Muscles between the ribs which expand/contract the ribcage to aid in breathing.

Gas Exchange and Diffusion:

• Diffusion involves the movement of particles from an area of higher concentration to lower concentration.
• Oxygen moves from the alveoli (high concentration) into the blood (low concentration).
• Carbon dioxide moves from the blood (high concentration) into the alveoli (low concentration) for exhalation.
• Concentration gradients drive diffusion across the thin walls of alveoli and capillaries.

Factors Increasing Breath Rate:

• Physical exercise increases breath rate to supply more oxygen and remove excess carbon dioxide due to higher oxygen consumption and carbon dioxide production by muscles.
• Fear activates the sympathetic nervous system and the release of adrenaline, increasing both heart rate and breathing rate to supply more oxygen to muscles for rapid response (fight or flight).

Inspired vs. Expired Air:

• Inspired air is inhaled from the atmosphere, and expired air is exhaled after gas exchange.
• Inspired air has roughly 21% oxygen, 0.04% carbon dioxide, and 78% nitrogen.
• Expired air has roughly 16-17% oxygen, 4-5% carbon dioxide, and the same amount of nitrogen as was inspired.
• Expired air typically has a higher water vapor content than inspired air.

Characteristics of Animals Respiring Through Skin:

• Thin skin facilitates efficient gas diffusion over a short distance.
• Large surface area maximizes the area for gas exchange.
• Moist skin allows gases to dissolve and diffuse easily.
• A rich blood supply provides a network of capillaries for gas transport.
• Permeable skin allows gases to pass through, facilitating respiration.

Red Blood Cells (Erythrocytes):

• Biconcave disc shape maximizes surface area for gas exchange.
• Mammalian RBCs lack a nucleus, and allow more room for hemoglobin.
• Flexible to squeeze through capillaries.
• Transports oxygen from the lungs to the tissues via hemoglobin.
• Transports carbon dioxide from tissues to the lungs.
• Helps regulate blood pH by buffering blood.
• Life span is approximately 120 days; broken down in the spleen and liver.

White Blood Cells (Leukocytes):

• Protect the body against infections, foreign invaders, and diseases.
• Lifespan ranges from hours to years, depending on the type.

Types of White Blood Cells:

• Neutrophils (50-70% of WBCs):
  • First line of defense against bacteria and fungi.
  • Use phagocytosis to engulf and kill microbes.
  • Have a short lifespan (a few hours to days).
• Eosinophils (1-4% of WBCs):
  • Involved in allergic reactions and parasitic infections.
  • Release enzymes to break down allergens.
  • Accumulate in inflamed tissues.
• Basophils
  • Less than 1% if WBCs
  • Involved in allergic reactions and inflammation
  • Release histamine and other chemicals
  • Promote increased blood flow to the site of infection

The human respiratory system is responsible for gas exchange, providing oxygen and removing carbon dioxide. Key components include the nose, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli. These work together to filter air, facilitate gas exchange, and protect the body.