Which Of The Following Is An Essential Feature For An Animal Gas Exchange Surface?

THE RESPIRATORY System

Tabular array of Contents

The Respiratory System and Gas Exchange | Bodies and Respiration

Respiratory Surfaces | Methods of Respiration | Respiratory Arrangement Principles

The Human Respiratory System | Diseases of the Respiratory System

The Alveoli and Gas Exchange | Control of Respiration | Links

The Respiratory System and Gas Exchange | Back to Top

Cellular respiration involves the breakdown of organic molecules to produce ATP . A sufficient supply of oxygen is required for the aerobic respiratory machinery of Kreb's Bicycle and the Electron Ship System to efficiently convert stored organic free energy into free energy trapped in ATP. Carbon dioxide is also generated past cellular metabolism and must be removed from the cell. In that location must be an commutation of gases: carbon dioxide leaving the cell, oxygen entering. Animals have organ systems involved in facilitating this exchange as well as the transport of gases to and from commutation areas.

Bodies and Respiration | Back to Top

Single-celled organisms exchange gases directly beyond their jail cell membrane. Yet, the tedious improvidence rate of oxygen relative to carbon dioxide limits the size of single-celled organisms. Simple animals that lack specialized commutation surfaces take flattened, tubular, or thin shaped body plans, which are the well-nigh efficient for gas exchange. However, these simple animals are rather pocket-sized in size.

Respiratory Surfaces | Back to Top

Large animals cannot maintain gas exchange past diffusion across their outer surface. They adult a multifariousness of respiratory surfaces that all increase the surface area for exchange, thus allowing for larger bodies. A respiratory surface is covered with thin, moist epithelial cells that allow oxygen and carbon dioxide to exchange. Those gases can only cross cell membranes when they are dissolved in h2o or an aqueous solution, thus respiratory surfaces must exist moist.

Methods of Respiration | Back to Top

Sponges and jellyfish lack specialized organs for gas exchange and have in gases directly from the surrounding water. Flatworms and annelids use their outer surfaces every bit gas substitution surfaces. Arthropods, annelids, and fish apply gills; terrestrial vertebrates utilize internal lungs.

Gas exchange systems in several animals. Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Assembly (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.

The Body Surface

Flatworms and annelids utilize their outer surfaces as gas exchange surfaces. Earthworms have a series of sparse-walled blood vessels known every bit capillaries. Gas exchange occurs at capillaries located throughout the body besides as those in the respiratory surface.

Amphibians use their peel as a respiratory surface. Frogs eliminate carbon dioxide 2.5 times as fast through their skin every bit they do through their lungs. Eels (a fish) obtain threescore% of their oxygen through their skin. Humans exchange just 1% of their carbon dioxide through their skin. Constraints of water loss dictate that terrestrial animals must develop more efficient lungs.

Gills

Gills greatly increase the surface area for gas exchange. They occur in a variety of brute groups including arthropods (including some terrestrial crustaceans), annelids, fish, and amphibians. Gills typically are convoluted outgrowths containing blood vessels covered by a sparse epithelial layer. Typically gills are organized into a series of plates and may be internal (as in crabs and fish) or external to the body (as in some amphibians).

Gills are very efficient at removing oxygen from water: in that location is but ane/20 the amount of oxygen present in water every bit in the same volume of air. H2o flows over gills in one management while blood flows in the contrary direction through gill capillaries. This countercurrent flow maximizes oxygen transfer.

Countercurrent menstruation in a fish. Images from Purves et al., Life: The Science of Biology, fourth Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.

Tracheal Systems

Many terrestrial animals have their respiratory surfaces inside the trunk and continued to the exterior by a series of tubes. Tracheae are these tubes that deport air straight to cells for gas substitution. Spiracles are openings at the body surface that lead to tracheae that branch into smaller tubes known as tracheoles. Body movements or contractions speed up the rate of improvidence of gases from tracheae into body cells. All the same, tracheae volition not role well in animals whose trunk is longer than 5 cm.

Respiratory arrangement in an insect. Paradigm from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Assembly (www.sinauer.com) and WH Freeman (world wide web.whfreeman.com), used with permission.

Lungs

Lungs are ingrowths of the torso wall and connect to the outside past every bit series of tubes and small-scale openings. Lung breathing probably evolved about 400 million years ago. Lungs are not entirely the sole property of vertebrates, some terrestrial snails accept a gas commutation structures similar to those in frogs.

Lungs in a bird (top) and amphibian (bottom). Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.

Respiratory System Principles | Back to Top

Movement of an oxygen-containing medium and then it contacts a moist membrane overlying claret vessels.
Diffusion of oxygen from the medium into the blood.
Ship of oxygen to the tissues and cells of the body.
Diffusion of oxygen from the blood into cells.
Carbon dioxide follows a opposite path.

Functional unit of a mammalian lung. Prototype from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (world wide web.whfreeman.com), used with permission.

The Human Respiratory System | Back to Elevation

This system includes the lungs, pathways connecting them to the outside surround, and structures in the chest involved with moving air in and out of the lungs.

The human respiratory organization. Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.

Air enters the body through the nose, is warmed, filtered, and passed through the nasal cavity. Air passes the pharynx (which has the epiglottis that prevents nutrient from entering the trachea).The upper role of the trachea contains the larynx . The song cords are 2 bands of tissue that extend across the opening of the larynx. After passing the larynx, the air moves into the bronchi that behave air in and out of the lungs.

The lungs and alveoli and their relationship to the diaphragm and capillaries. Images from Purves et al., Life: The Science of Biological science, 4th Edition, past Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.

Bronchi are reinforced to forestall their collapse and are lined with ciliated epithelium and mucus-producing cells. Bronchi branch into smaller and smaller tubes known as bronchioles . Bronchioles terminate in grape-like sac clusters known every bit alveoli . Alveoli are surrounded by a network of thin-walled capillaries . Only almost 0.2 µm split the alveoli from the capillaries due to the extremely thin walls of both structures.

Gas exchange across capillary and alveolus walls. Image from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.

The lungs are large, lobed, paired organs in the chest (also known as the thoracic crenel ). Thin sheets of epithelium ( pleura ) split up the inside of the chest cavity from the outer surface of the lungs. The bottom of the thoracic cavity is formed by the diaphragm .

Ventilation is the mechanics of breathing in and out. When you inhale, muscles in the breast wall contract, lifting the ribs and pulling them, outward. The diaphragm at this time moves downward enlarging the chest cavity. Reduced air pressure level in the lungs causes air to enter the lungs. Exhaling reverses theses steps.

Inhalation and exhalation. Prototype from Purves et al., Life: The Science of Biological science, 4th Edition, by Sinauer Assembly (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.

Diseases of the Respiratory System | Dorsum to Peak

The condition of the airways and the pressure level divergence between the lungs and atmosphere are important factors in the period of air in and out of lungs. Many diseases affect the status of the airways.

Asthma narrows the airways past causing an allergy-induced spasms of surrounding muscles or past clogging the airways with mucus .
Bronchitis is an inflammatory response that reduces airflow and is caused by long-term exposure to irritants such as cigarette smoke, air pollutants, or allergens .
Cystic fibrosis is a genetic defect that causes excessive mucus production that clogs the airways.

The Alveoli and Gas Exchange | Back to Top

Improvidence is the motion of materials from a college to a lower concentration. The differences betwixt oxygen and carbon dioxide concentrations are measured past partial pressures. The greater the divergence in partial force per unit area the greater the rate of diffusion.

Respiratory pigments increase the oxygen-carrying chapters of the claret. Humans accept the reddish-colored pigment hemoglobin as their respiratory pigment. Hemoglobin increases the oxygen-carrying capacity of the blood betwixt 65 and lxx times. Each red blood cell has well-nigh 250 1000000 hemoglobin molecules, and each milliliter of blood contains 1.25 X x¹⁵ hemoglobin molecules. Oxygen concentration in cells is low (when leaving the lungs blood is 97% saturated with oxygen), so oxygen diffuses from the claret to the cells when it reaches the capillaries.

Effectiveness of diverse oxygen carrying molecules. Image from Purves et al., Life: The Science of Biological science, quaternary Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.

Carbon dioxide concentration in metabolically active cells is much greater than in capillaries, so carbon dioxide diffuses from the cells into the capillaries. H2o in the blood combines with carbon dioxide to grade bicarbonate . This removes the carbon dioxide from the blood so diffusion of even more carbon dioxide from the cells into the capillaries continues even so still manages to "package" the carbon dioxide for eventual passage out of the torso.

Details of gas exchange. Images from Purves et al., Life: The Scientific discipline of Biology, 4th Edition, past Sinauer Assembly (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.

In the alveoli capillaries, bicarbonate combines with a hydrogen ion (proton) to form carbonic acid, which breaks downward into carbon dioxide and h2o. The carbon dioxide and then diffuses into the alveoli and out of the trunk with the side by side exhalation.

Control of Respiration | Back to Top

Muscular contraction and relaxation controls the rate of expansion and constriction of the lungs. These muscles are stimulated past nerves that carry messages from the part of the encephalon that controls breathing, the medulla . Two systems control breathing: an automatic response and a voluntary response. Both are involved in holding your breath.

Although the automatic breathing regulation system allows yous to exhale while you sleep, it sometimes malfunctions. Apnea involves stoppage of breathing for as long every bit 10 seconds, in some individuals as oft equally 300 times per night. This failure to respond to elevated claret levels of carbon dioxide may outcome from viral infections of the brain, tumors, or it may develop spontaneously. A malfunction of the animate centers in newborns may result in SIDS (sudden infant death syndrome) .

As altitude increases, atmospheric force per unit area decreases. Above 10,000 anxiety decreased oxygen pressures causes loading of oxygen into hemoglobin to drop off, leading to lowered oxygen levels in the blood. The result can exist mountain sickness (nausea and loss of appetite). Mount sickness does not result from oxygen starvation but rather from the loss of carbon dioxide due to increased breathing in social club to obtain more oxygen.

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