Gas Exchange

• • Gas exchange in plants refers to the process by which plants take in carbon dioxide and release oxygen through tiny pores called stomata.
• Gas exchange is essential for plants as it helps them carry out photosynthesis, which is the process of producing food and energy from light, water, and carbon dioxide.
• The outermost layer of the leaf is the epidermis. It consists of the upper and lower epidermis, which are present on either side of the leaf. Botanists call the upper side the adaxial surface (or adaxis) and the lower side the abaxial surface (or abaxis).
• Parts of Leaf

  • Waxy Cuticle

  A waxy layer known as the cuticle covers the leaves of all plant species.

  • Upper Epidermis
  • Palisade layer
  • Spongy Layer
  • Lower Epidermis
  • Guard Cell
  • Stomata
• Waxy Cuticle

  • a waxy layer known as the cuticle covers the leaves of all plant species.
  • The cuticle reduces the rate of water loss from the leaf surface.
  • Other leaves may have small hairs (trichomes) on the leaf surface. Trichomes help to avert herbivory by restricting insect movements or by storing toxic or bad-tasting compounds.
• This is called trichomes

  
• Upper Epidermis

  This is a single layer of cells containing few or no chloroplasts. The cells are quite transparent and permit most of the light that strikes them to pass through to the underlying cells.
• Palisade Layer

  -This consists of one or more layers of cylindrical cells oriented with their long axis perpendicular to the plane of the leaf. The cells are filled with chloroplasts (usually several dozen of them) and carry on most of the photosynthesis in the leaf.
• Spongy layer

  • Lying beneath the palisade layer, its cells are irregular in shape and loosely packed.
  • Their main function seems to be the temporary storage of sugars and amino acids synthesized in the palisade layer.
  • They also aid in the exchange of gases between the leaf and the environment. During the day, these cells give off oxygen and water vapor to the air spaces that surround them.
• Spongy Layer

  • They also pick up carbon dioxide from the air spaces. The air spaces are interconnected and eventually open to the outside through pores called stomata
  • Collectively, the palisade and spongy layers make up the mesophyll.
• Lower Epidermis

  most of the stomata (thousands per square centimeter) are located in the lower epidermis.
• Guard Cell

  regulate the opening and closing of the stomata. Thus they control the exchange of gases between the leaf and the surrounding atmosphere.
• Stomata

  That control transpiration and gas exchange with the air. During the day when photosynthesis occurs, the oxygen released from the process is utilized for respiration.
• Epidermis aids in the regulation of gas exchange. It contains stomata, which are openings through which the exchange of gases takes place. Two guard cells surround each stoma, regulating its opening and closing. Guard cells are the only epidermal cells to contain chloroplasts.
• Lenticel

  Loosely arranged cells that acting as a pore to allow the gas exchange.
• Anthracnose

  a group of fungal diseases that affect a variety of plants in warm, humid areas. Shade trees such as sycamore, ash, oak, and maple are especially susceptible, though the disease is found in a number of plants, including grasses and annuals.
• Powdery mildew

  plant disease of worldwide occurrence that causes a powdery growth on the surface of leaves, buds, young shoots, fruits, and flowers. Powdery mildew is caused by many specialized races of fungal species in the genera Erysiphe, Microsphaera, Phyllactinia, Podosphaera, Sphaerotheca, and Uncinula. Hundreds of species of trees, shrubs, vines, flowers, vegetables, fruits, grasses, field crops, and weeds can be affected by powdery mildew.
• Gas exchange is a life-sustaining process that allows animals to acquire oxygen for energy production and dispose of carbon dioxide, a waste product of metabolism. This vital process is essential for the survival and functioning of all animals.
• 1. Intake of Oxygen and Carbon Dioxide Expulsion (Respiration) - involves the uptake of oxygen from the environment and the expulsion of carbon dioxide, which is a waste product of cellular respiration.
• 2. Direct Diffusion - for small multicellular organisms, gas exchange by direct diffusion across surface membranes is sufficient. In simple organisms, every cell in the body is close to the external environment.

  Take note: diffusion should occur across moist membrane
• 3. Specialized Respiratory Structures:

  Skin: Some animals respire through their skin.

  Gills: Aquatic animals often use gills.

  Tracheae: Insects have a network of air-filled tubes called tracheae.

  Lungs: Many terrestrial animals, including mammals, use lungs for gas exchange.
• 4. Gas Exchange in Lungs - Air in mammals is warmed and moistened in the nose, then travels through the throat and windpipe into the lungs. There, it moves through bronchi and bronchioles, where gas exchange begins.
• 5. Alveoli and Capillaries - exchange occurs in the alveoli, which are comprised of one-cell-layer-thick membranes. Oxygen moves into the capillary and carbon dioxide moves into the alveoli from the blood in the capillary.
• • This process ensures that oxygen is delivered to the cells of the body's tissues for cellular respiration, and carbon dioxide, a cell waste product, is removed.

  Cellular respiration transforms food into ATP, the cell's energy source. Aerobic respiration, needing oxygen, produces lots of ATP but also carbon dioxide. Efficient gas exchange keeps oxygen levels up and removes carbon dioxide, maintaining energy levels in cells.
• Fish (Gill)

  Gills are thin layers of tissue richly supplied with blood vessels.

  • most fish exchange gases like oxygen and carbon dioxide using gills that are protected under gill covers (operculum) on both sides of the pharynx (throat). Gills are tissues that are like short threads, protein structures called filaments.
• Fish (Gill)

  Opercular Flap - the operculum is a hard, plate-like, bony flap that covers the gills of a bony fish (superclass: Osteichthyes). It protects the gills and also serves a role respiration. Fish can acquire dissolved oxygen through pumping water over their gills by opening and closing their jaws and opercula.
• Mammals

  Trachea - also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all animals with lungs.

  • Bronchi represent the passageways leading into the lungs.
• Mammals

  Bronchioles - carry oxygen rich air into the lungs and carry carbon dioxide rich air out of the lungs, thereby aiding in the processes of breathing and respiration.

  Pulmonary artery - carries blood that is low in oxygen and high in carbon dioxide waste to the pulmonary capillaries of the lungs, where the exchange takes place.
• Mammals

  Pulmonary Vein - The pulmonary vein (s) are vessels carrying oxygen - rich blood from the lungs to the left atrium of the heart, which is critical for proper respiration.

  • Alveoli are tiny, balloon-shaped air sacs found in the lungs of mammals.
• The lungs of mammals are divided into millions of microscopic air sacs called alveoli (the singular is alveolus). Each alveolus is surrounded by a rich network of blood vessels for transporting gases.

  In addition, mammals have a dome-shaped diaphragm that separates the thorax from the abdomen, providing a separate chest cavity for breathing and pumping blood. During inhalation, the diaphragm contracts and flattens to create a partial vacuum in the lungs. The lungs fill with air, and gas exchange follows.
• A system of tubes (held open by rings of cartilage) allows air to flow in and out of the lungs

  • Air enters via trachea (windpipe)

  • Trachea branches into two bronchi (one bronchus to each lung)

  • Bronchi branch into bronchioles
• Birds

  Birds have large air spaces called AIR SACS in their lungs. When a bird inhales, its rib cage spreads apart and a partial vacuum is created in the lungs. Air rushes into the lungs and then into the air sacs, where most of the gas exchange occurs. This system is birds’ adaptation to the rigors of flight and their extensive metabolic demands.
• Earthworms

  -exchange oxygen and carbon dioxide directly through their SKIN. The oxygen diffuses into tiny blood vessels in the skin surface, where it combines with the red pigment hemoglobin. Hemoglobin binds loosely to oxygen and carries it through the animal’s bloodstream. Carbon dioxide is transported back to the skin by the hemoglobin.
• Terrestrial Arthropods

  have a series of openings called SPIRACLES at the body surface. Spiracles open into tiny air tubes called tracheae, which expand into fine branches that extend into all parts of the arthropod body.
• Terrestrial Vertebrates

  such as amphibians, reptiles, birds, and mammals have well-developed respiratory systems with lungs. Amphibians can also exchange gases through their skin. Reptiles have folded lungs to provide increased surface area for gas exchange. Rib muscles assist lung expansion and protect the lungs from injury.
• Ammonia Toxicity occurs when there's an excess of ammonia in their environment or bloodstream. Fish produce ammonia as a waste product of protein metabolism, and normally, their gills help them eliminate it into the surrounding water.

  • Pulmonary Hypertension this similarly affects gas exchange but with some species-specific considerations. Pulmonary hypertension in animals, like in humans, involves elevated blood pressure in the arteries of the lungs. This condition can occur in various animals, including mammals, birds, and reptiles.
• • Asthma a chronic respiratory condition characterized by inflammation and narrowing of the airways, which can affect gas exchange in humans.

  Pneumonia - is an infection that inflames the air sacs in one or both lungs. The air sacs may fill with fluid or pus (purulent material), causing cough with phlegm or pus, fever, chills, and difficulty breathing. A variety of organisms, including bacteria, viruses and fungi, can cause pneumonia.
• Mechanism of gas exchange in Animal

  1. Intake of Oxygen and carbon dioxide expulsion (Respiration)
  2. Direct diffusion
  3. Specialized respiratory structure
  4. Gas Exchange in Lungs
  5. Alveoli and Capillaries