III. Gas Exchange

• GAS EXCHANGE - process of getting oxygen from air (or water) and releasing carbon dioxide wastes
• Plant Tissues - Three main types of tissue

  1. Dermal - On external surfaces that serves a protective function.
  2. Ground - Forms several different internal tissue types and can participate in photosynthesis, serve a storage function, or provide structural support.
  3. Vascular - Conducts water and nutrients.
• Plant tissues (Dermal Tissue)

  A) Root hairs

  B) Trichomes

  C) Stoma of leaf

  D) cork of older stem

  
• PLANT TISSUES (Dermal Tissue: Guard Cells)

  • Paired sausage-shaped cells
  • Flank a stoma (pl. stomata) - epidermal opening
  • Passageway for oxygen, carbon dioxide, and water vapor.
• Guard cell is the only living part of the stoma
• Abscisic acid (ABA) - is a plant hormone that plays a central role in regulating stomatal movement, particularly in response to environmental stress and water availability.

  • Abscisic acid (ABA) initiates a signaling pathway to close stomata in drought.
  • Opens K+ and Cl-and malate channels.
  • Water loss follows, making guard cells flaccid.
• Also Affecting Stomatal Opening

  • Close when CO2 concentrations are high
  • Open when blue wavelengths of light promote uptake of K+ by the guard cells
  • Close when temperature exceeds 34°C and water relations unfavorable
  • Crassulacean acid metabolism (CAM) plants conserve water in dry environments by opening stomata and taking in CO2 at night
• Specialized Structure for Gas Exchange LENTICEL

  • small, corky pores or openings in the bark of woody stems and roots of plants.
  • facilitate gas exchange between the internal tissues of the plant and the external environment.
• Respiration is the sequence of events that results in gas

  exchange between the body’s cells and the environment

  A) Ventilation

  B) External Respiration

  C) Internal Respiration

  
• External Respiration - gas exchange between the air and the blood within the lungs
• Internal Respiration - gas exchange between the blood and the tissue fluid (interstitial).
• • Gas exchange takes place by diffusion.
  • For external respiration to be effective, gas-exchange regions must be:

  1. Moist.
  2. Thin.
  3. Large in relation to body size.

  • Effectiveness of diffusion is enhanced by vascularization (presence of many capillaries).
  • Delivery to cells is promoted by respiratory pigments (for example, hemoglobin).
• GAS-EXCHANGE Hydra

  • Simple Diffusion - lacks specialized respiratory structures like gills or lungs
• GAS-EXCHANGE Hydra

  Oxygen Uptake

  • Oxygen from the water diffuses through the moist epidermis of Hydra and enters the cells of the ectoderm.
  • As Hydra is a simple organism with relatively few cell layers, oxygen can readily reach its cells through diffusion
• GAS-EXCHANGE Hydra

  Carbon Dioxide Release:

  • Carbon dioxide, produced as a byproduct of cellular respiration, diffuses out of the cells and across the epidermis into the surrounding water.
• GAS-EXCHANGE Earthworm

  • Cutaneous Respiration - exchange of gases through the skin.
  • Moisture is crucial - Oxygen from the air dissolves in the thin layer of moisture on the skin and diffuses into the bloodstream.
  • Highly vascularized skin - extensive network of blood vessels.
• GAS-EXCHANGE Vertebrates

  GILLS

  • Finely divided, vascularized outgrowths of the body surface or the pharynx.
  • Gills of bony fishes.
  • Outward extensions of pharynx. •Ventilation is brought about by combined action of the mouth and gill covers (opercula).
• GAS-EXCHANGE in Vertebrates GILLS

  A) Concurrent flow

  B) Countercurrent flow

  
• Concurrent flow - is when oxygenrich water passing over gills would

  flow in the same direction as oxygen-poor blood in vessels and results in 50% oxygen extraction.
• Countercurrent flow means the two liquids flow in opposite directions and results in 8 to 90% oxygen extraction.
• GAS-EXCHANGE in Vertebrates TRACHEA

  TRACHEAL SYSTEM OF INSECTS
• GAS-EXCHANGE in Vertebrates TRACHEA

  TRACHEAL SYSTEM OF INSECTS

  • Spiracles - openings on the insect’s body that allow air to enter and exit
  • Trachea - main respiratory tubes
  • Tracheoles - smallest branches of the tracheal system
  • Air sacs - store and regulate the movement of air within the tracheal system
• GAS-EXCHANGE Vertebrates

  Lungs

  • Air moving through the upper respiratory system. = Is filtered to free it of debris by hairs and cilia. Warmed. Humidified.
  • Air reaching lungs. = Is at body temperature, and. Is saturated with water.