Animal Anatomy and Physiology - Respiration

Animal Anatomy and Physiology - Respiration

• Learning Outcomes
  • Describe the respiratory tract of humans and the air pathway to the lungs.
  • Describe the structure and characteristics of hemoglobin.
  • Explain the oxyhemoglobin dissociation curve.
  • Explain oxygen and carbon dioxide transport.
  • Compare inhalation and exhalation.

Respiratory Tract of Humans

• A transport system connects respiratory organs for gas exchange with the atmosphere.
• Air enters the environment through the nose.
• The nasal cavity filters dust particles using cilia lining the mucous membrane, removing them as mucus.
• Airway structures include the nasal cavity, nostrils, oral cavity, pharynx, larynx, trachea, right and left main bronchus, right and left lung, and diaphragm.

Pharynx (Throat)

• Receives air from the nasal cavity and air, food, and water from the oral cavity.

Larynx (Voice Box)

• Protects the lower respiratory tract by preventing food from entering the trachea.

Trachea (Windpipe)

• Surrounded by protective cartilaginous rings.
• Lined with mucosa tissue containing goblet cells that produce mucus.

Lungs

• Contain three right lobes and two left lobes.
  • right superior lobe
  • right middle lobe
  • right inferior lobe
  • left superior lobe
  • left inferior lobe

Bronchus and Bronchioles

• Contain epithelial cells secreting mucus to trap bacteria and airborne particles.
• Cilia sweep mucus upwards for removal.

Alveoli

• Have a large surface area for efficient gas diffusion simultaneously.
• Lined with thin and moist squamous epithelium cells.
• Surrounded by blood capillaries. Oxygen in alveoli and carbon dioxide in capillaries create a concentration gradient for gaseous exchange.
• Contain surfactant to prevent lung collapse or over-inflation.
• Phagocytes are present to kill bacteria.

Pulmonary Surfactant

• A complex mixture of phospholipids and proteins.
• Reduces surface tension at the alveolar air interface, preventing atelectasis (lung collapse).

Boyle's Law

• Pressure and volume of a gas are inversely proportional, assuming constant temperature and mass.
  • Higher pressure results in lower volume.
  • Lower pressure results in higher volume.

Law of Laplace

• Pressure is directly proportional to surface tension and inversely proportional to the radius of an alveolus.
  • Smaller alveoli are at greater risk of collapse without surfactant.

Functions of Surfactants

• Reduce surface tension preventing atelectasis.

Hemoglobin (Hb)

• The respiratory pigment in red blood cells.
• Carries oxygen and carbon dioxide.
• Made up of four subunits of a conjugated protein.
  • heme (iron) group
  • globin

Oxygen Transport

• 95% is transported as oxyhemoglobin.
• 5% is dissolved in blood plasma.
• Affected by carbon dioxide concentration, pH, and temperature.

Carbon Dioxide Transport

• 70% is transported as bicarbonate ions (HCO₃⁻).
• 23% is bound to hemoglobin (carbaminohemoglobin).
• 7% is dissolved in blood plasma.
  • through the carbonic anhydrase process.

Controlling Breath

• Inhalation and exhalation are controlled by the respiratory centre and diaphragm and intercostal muscles, influenced by stretch receptors.

Oxyhemoglobin dissociation curve

• A sigmoid curve representing oxygen saturation in hemoglobin.
• Oxygen partial pressure affects oxygen binding (loading/unloading).
  • High Po2 indicates high saturation (more oxygen bound).
  • Low Po2 indicates low saturation (less oxygen bound).

Myoglobin

• Myoglobin binds oxygen tighter than hemoglobin at low po2. Myoglobin is primarily found in muscle tissues.