Biology: Integumentary Respiration

Respiration

• Integumentary respiration: occurs in organisms living in moist environments, where oxygen diffuses through the skin, which must be moist
• Examples: ¼ of oxygen in frogs is acquired via cutaneous respiration, and lungless salamanders rely solely on cutaneous respiration in the buccal-pharyngeal region

Tracheal Systems

• Present in some terrestrial environments
• Composition:
  • Trachea: contains openings with spiracles
  • Spiracle: coverings that can open and close to prevent water from entering the tracheal system
  • Tracheole: connected to the trachea

Gills (Brachia)

• Formed by evaginations/external outgrowths from the body surface
• Types:
  • External gills: found on the external side
  • Internal gills: covered by the epidermis
• Composed of gill arches: fish possess 4 gill arches, each with two layers of gill filaments
• Countercurrent gas exchange:
  • Flow of blood is opposite the direction of the flow of water
  • Allows for easier capture of oxygen: oxygen-poor blood will capture oxygen quickly with the oxygen-rich waters

Lungs

• For air respiration in terrestrial environments
• Alveoli:
  • Where the exchange of gas occurs
  • Rich in capillaries that release CO2 and capture O2
  • Composed of simple squamous epithelium to allow easy passage of gases
  • Thinner membrane increases the rate of diffusion of gases
• From the trachea → bronchi → bronchioles → alveoli
• Lung ventilation:
  • Positive pressure pumping mechanism
  • Example: how frogs respire/inspire

Hematopoeisis (Hemopoiesis)

• Formation of cells in the blood
• All cells are from multipotent stem cells
• Differentiation into:
  • Lymphoid stem cells: give rise to lymphocytes (B and T-lymphocytes)
  • Myeloid stem cells: give rise to erythrocytes (red blood cells), leucocytes (white blood cells), and platelets

Erythrocytes (Red Blood Cells)

• 3 cellular features:
  • Biconcavity increases surface area for gas exchange
  • Contain heme consisting of hemoglobin for binding oxygen
  • Anucleate (no nucleus) to increase space for oxygen
• Short lifespan: 120 days
• Recycled by the liver and spleen to be broken down into components (hemoglobin)
• Comprise 90% of cells in the blood

Life Cycle of RBC

• Macrophages break down RBC to its major components: globin and heme
• Globin broken down to amino acid components, reused for protein synthesis
• Iron in the heme has two pathways:
  • Transported to the liver via transferrin, stored in ferritin
  • Converted into biliverdin, then bilirubin, transferred to the liver, and excreted into bile

Control of Erythrocyte Level

• Anemia: low concentration of RBC, causing hypoxia (low oxygen levels)
• Imbalance of RBC detected by kidneys, triggered by low oxygen levels in the blood
• Kidneys (and sometimes liver) release erythropoietin to stimulate bone marrow to enhance erythropoiesis

Leukocytes (White Blood Cells)

• Types:
  • Granular: have granules in the cytoplasm (basophils, neutrophils, eosinophils)
  • Agranular: no granules in the cytoplasm (lymphocytes, monocytes)
• Functions: fight foreign materials/objects detected in the body (except NK cells)

Thrombocytes (Platelets)

• Function: blood clotting
• After some time, a bleeding wound will stop bleeding because of platelets

Blood Circulation

• Blood flow:
  • From the upper body, passes through the anterior vena cava, and also through the posterior vena cava for the lower body
  • Enters the right atrium, then the right ventricle, monitored by the atrioventricular valve (tricuspid valve)
  • Enters the pulmonary artery to be oxygenated in the lungs, monitored by the semilunar valve
• Oxygenated blood:
  • From the lungs, passes through the pulmonary veins
  • Enters the left atrium, then the left ventricle, monitored by the atrioventricular valve (bicuspid valve)
  • Glomerular filtration: where most of the filtration occurs

Learn about the process of respiration through the integument of an organism, commonly found in amphibians living in moist environments. Discover how oxygen is acquired through the skin in frogs and lungless salamanders.