Pulmonary and Plant Respiration: A Detailed Analysis

Posted on Jan 5, 2025 in Geology

Pulmonary Respiration

In pulmonary respiration, gas exchange takes place in specialized cavities with highly vascularized, thin walls called lungs. These cavities are connected to the outside through:

  • Nostrils: Where air is heated and cleaned of impurities.
  • Pharynx: Connects the nasal passages, mouth, and throat.
  • Larynx: Reinforced by cartilage and contains the vocal cords.
  • Trachea: A tube reinforced with cartilaginous rings, serving as a cleaning area, which bifurcates into the bronchi.
  • Bronchi, Bronchioles, and Alveoli: Where gas exchange occurs.

Adaptations of the Respiratory System

  1. Increased surface area.
  2. Mechanisms for ventilation.
  3. Enhanced pulmonary circulation.

Respiration in Plants

Plants also require O2 and CO2. However, their incorporation does not require a specialized respiratory system because:

  1. The needs of plants are lower than those of animals.
  2. Plant tissues are relatively close to the exterior.
  3. Many cells in plant tissues form intercellular spaces.

Plants have specialized structures like stomata and lenticels for gas exchange.

Photosynthesis and Cellular Respiration

Photosynthesis involves the release or uptake of large quantities of O2 and CO2.

CO2 + H2O + Light Energy → Organic Matter + O2

Cellular respiration in plants consumes O2 and releases CO2.

Organic Matter + O2 → CO2 + H2O + Energy

Animal Excretion

Catabolic activity generates waste products that must be eliminated. This elimination is carried out through excretion and the excretory system. In multicellular organisms, excretion also regulates the volume of body fluids, a function called homeostasis.

Waste Products in Animals

  • Non-nitrogenous: CO2 (eliminated through respiratory surfaces) and H2O (eliminated in liquid form by the excretory system).

  • Nitrogenous: Nitrogen is excreted as ammonia or urea. Animals are classified as:

    • Ammoniotelic: Excrete ammonia directly (very toxic); aquatic animals, fish.
    • Ureotelic: Excrete urea as nitrogenous waste (less toxic); must be diluted for excretion; sharks, amphibians, turtles, and mammals.
    • Uricotelic: Excrete uric acid (slightly toxic); requires little water because it is not very soluble, allowing its accumulation without causing serious harm; insects, reptiles, and birds.

Excretory Systems in Invertebrates

These are organs responsible for eliminating waste products from cellular metabolism.

  • Protonephridia (flatworms): Highly branched tubules ending in cells with cilia or flagella. Movement of cilia or flagella creates a current that moves fluid through the tubule and facilitates the elimination of waste to the exterior.
  • Metanephridia (annelids and mollusks): Consist of a coiled tubule surrounded by a capillary network with two openings: external and internal. Within the metanephridia, useful compounds are reabsorbed, and waste is expelled.
  • Malpighian Tubules (insects): Thin, closed tubules at one end and open at the other to the digestive tract. Solutes and water pass into the tubule, waste is expelled through the anus, and water and solutes are later reabsorbed in the intestine.
  • Green Glands (crustaceans): Consist of a sac that collects waste substances, a long tubule where reabsorbable substances are recovered, and a bladder that eliminates waste to the exterior through an excretory pore.

Excretory Systems in Vertebrates

These systems are formed by kidneys, which contain nephrons that produce urine (composed of water and waste substances).

Kidney and Nephron in Mammals

Mammals have two bean-shaped kidneys, about 10 cm long, highly vascularized. Blood enters through the renal artery and exits through the renal vein. The nephron is the functional unit of the kidney, located in the cortex and medulla; there are more than one million nephrons per kidney. Each nephron receives an arteriole.

Other Excretory Organs

Waste substances are also eliminated through:

  • Sweat Glands: Produce sweat, eliminate waste substances, and regulate body temperature.
  • Liver: Metabolizes bilirubin, and waste is eliminated in the intestine.
  • Salt Glands: Marine turtles and birds have salt glands that eliminate excess salt.

Urine Formation in Vertebrates

Urine formation occurs in the nephrons and consists of three stages:

  1. Glomerular Filtration: Occurs in Bowman’s capsule due to pressure differences between the glomerular capillaries and the interior of the capsule. The caliber of the afferent arterioles (carrying blood in) is greater than that of the efferent arterioles (carrying blood out), creating higher pressure in the glomerular capillaries. A fluid similar to blood plasma, containing waste substances, is filtered into Bowman’s capsule.

  2. Tubular Reabsorption: Glomerular filtration is not selective. In the tubules of the nephron, most of the usable substances are reabsorbed. Each substance is reabsorbed in different sections of the tubules by the numerous surrounding capillaries and returned to the blood.

  3. Secretion: Some substances are secreted by diffusion or active transport. This is important for maintaining the concentration of ions like H+ and K+. The resulting fluid, urine, passes through the collecting tubules, which empty into the renal pelvis. From there, urine travels through the ureters to the bladder, where it is stored and eventually eliminated through the urethra.

Excretion in Plants

Plants differ from animals in the following ways:

  1. They do not have specialized excretory structures.
  2. They produce waste substances, some of which are used in photosynthesis.
  3. Waste products are not always eliminated to the exterior.

Waste Products in Plants

There are three types of waste products:

  1. Gaseous Substances: CO2 (produced during cellular respiration and eliminated through stomata) and ethylene (produced in ripening fruits).

  2. Liquid Substances: Essential oils (expelled or stored in nodal cilia in cells or oil bladders), resins (liquids that accumulate in the resiniferous canals of the parenchyma), and latex (stored in droplets in the laticiferous canals).

  3. Solid Substances: Calcium oxalate (accumulates as crystals inside vacuoles), turpentine (derived from pine resin), and natural rubber (derived from latex).