Section 11.1 The Function of Respiration
RESPIRATORY SYSTEM – the group of organs that provides living things with oxygen from outside the body and disposes of waste products such as carbon dioxide
-Ensures that oxygen is brought into the body and made available to all cells that need it, and carbon dioxide can leave cells and be removed from the body
RESPIRATION – all the processes involved in bringing oxygen into the body, making it available to each cell, and eliminating carbon dioxide as waste
RESPIRATORY AND GAS EXCHANGE
-Several stages, each stagehas specialized structures to facilitate it
- Breathing
- External respiration
- Internal respiration
- Cellular respiration
-First stage (Breathing): involves two basic processes: inspiration (breathing in, inhaling)and expiration (breathing out, exhaling)
INSPIRATION – action of drawing oxygen rich air into the lungs
EXPIRATION – action of releasing waste air from the lungs
-Inspiration moves air from outside the body into the lungs inside the body
-Expiration moves air from lungs back outside the body
-Second stage (external respiration): exchange of oxygen and carbon dioxide between the inspired air inside the lungs and blood
-Vital function of gas exchange
GAS EXCHANGE – transfer/delivery of oxygen from inhaled air into the blood, elimination of carbon dioxide from blood into lungs, primary function of lungs
-Third stage (internal respiration): exchange of oxygen and carbon dioxide between blood and body’s tissue cells
-Fourth stage (cellular respiration): series of energy releasing chemical reactions that take place within cells, sole means of providing energy for all cellular activities
RESPIRATORY SURFACES
-Two main requirements for respiration
- Respiratory surface must be large enough for the exchange of oxygen and carbon dioxide to occur quickly enough to meet the body’s needs
- Respiration must take place in a moist environment so oxygen and carbon dioxide are dissolved in water
RESPIRATORY SURFACE – area of an animal’s body where gases are exchanged with the environment
-Some animals exchange gases through their outer body surface, gills or trachea
-As with nutrients, gases involved in respiration are transported to and from the cells throughout the body by the circulatory system
-All organisms use ventilation to increase the efficiency of respiration
VENTILATION – the process of drawing, or pumping, an oxygen containing medium (water or air) over a respiratory surface (gills, trachea, lungs)
TYPES OF RESPIRATORY SURFACES IN ANIMALS
Description of Respiratory Surfaces / ExampleOuter Skin
-Animals (Ex. Earthworms) don’t have specialized gas exchange organs
-Use their outer skin as a respiratory surface
-Oxygen diffuses into a network of thin walled capillaries below the skin, carbon dioxide diffuses out
-Animals that breathe though their skin usually have a high ratio of respiratory surface to body volume
-Must live in damp places or in water to keep their respiratory surface (skin surface) moist
-Amphibians /
Gills
-Fish, aquatic invertebrates, clams, mussels, crayfish, crabs exchange gases through gills
-Gills are the extensions or folds in the body surface that increase that increase the surface area through which gases are exchanged
-Oxygen in water diffuses across gill surfaces into capillaries, carbon dioxide diffuses out into the external environment
-Surrounded by water, therefore respiratory surfaces are always moist /
Tracheal System
-Insects exchange gas through a tracheal system, internal system of branching respiratory tubes called tracheae
-Tracheae connects body cells directly to the environment outside of the insect’s body by smaller tubes called spiracles
-Oxygen enters body through the spiracles, then diffuses into the tracheae
-Carbon dioxide diffuses out of the body in the opposite direction
-Insect’s circulatory system not involved in transporting oxygen, gas is exchanged directly with the body cells /
Lungs
-Due to large size and higher activity levels, most land animals need large amounts of oxygen that can’t be delivered by gills or a tracheal system
-Mammals, birds, reptiles, most amphibians exchange gases through an internal respiratory system
-Consists of trachea (windpipe) that branches into lungs
-Lungs are sacs lined with moist epithelium
-Folds in lung lining increase the surface area for diffusion
-Oxygen diffuses across epithelium into capillaries
-Carbon dioxide diffuses in the opposite direction into external environment /
GAS EXCHANGE IN AQUATIC ENVIRONMENTS
-Aquatic environments contain oxygen in the form of dissolved gas
-Fish, lobster, clams, molluscs take in oxygen through gills
GILLS – physical adaptations that enable organisms to carry out gas exchange in aquatic environments
-Fish exchanges gas by taking water into its mouth, then ventilating (pumping) it over the gills
-As water flows across the gills, dissolved oxygen in the water diffuses, from high concentration (water) to low concentration (blood), into the blood circulating through the surrounding capillaries
-Carbon dioxide diffuses from the blood across the gill tissue, intro the water and is carried out of the fish’s body as water passes out of the gill openings
-Fish also have a counter current exchange mechanism: oxygen diffuses along a gradient (diffusion gradient)
DIFFUSION GRADIENT – describes the relationship in which a dissolved substance moves from a region of high concentration to a region of low concentration
-Blood and water flow in opposite directions, thus the diffusion gradient of oxygen is kept high
GAS EXCHANGE ON LAND, MECHANICS OF BREATHING
-Air breathing vertebrates (Ex. Reptiles, birds, mammals) rely on lungs for gas exchange
-These vertebrates have a specialized system in their respiratory system that provides a passage for air to move from outside to inside the body, where gas exchange occurs
-Air doesn’t flow in/out of the lungs on its own
-Brain acts as a respiratory control centre to co-ordinate breathing movements, regulate breathing rate, monitors the volume of air into the lungs, monitors gas levels in blood
-Two sets of structures: muscular diaphragm and rib muscles, control the air pressure inside the lungs
-Changes in air pressure causes air to move in/out of lungs
DIAPHRAGM – dome shaped sheet of muscle that separates the region of lungs (thoracic cavity) from the region of stomach and liver (abdominal cavity)
-Rib muscles (intercostal muscles) found between ribs and along the inside surface of the rib cage
AIR PRESSURE IN THE LUNGS
-Regular signals from the brain triggers the diaphragm and intercostal muscles to work together at the same time, thus causing air to move in/out of the lungs
-Air pressure within lungs is controlled by these 2 structures
-Inhalation begins when external intercostal muscles and diaphragm contract; diaphragm moves down
-This expands rib cage upwards and outwards, floor of chest cavity moves downward
-Chest cavity is airtight, thus its volume increases
-Increase in volume means the same amount of air contained in a larger space
-When molecules of a gas are moved father apart (as they are when volume of the chest cavity increases), gas molecules exert less outward pressure, thus air pressure in thoracic cavity decreases
-Lungs are suspended in the chest cavity, sensitive to changes in the air pressure of the cavity
-As air pressure in the cavity decreases, walls of lungs are drawn outward into the chest cavity and the lungs expand
-Expansion causes air pressure in the lungs to be lower than the air pressure outside of the body
-Since air moves from regions of higher pressure to regions of lower pressure, air rushes into the lungs from the external environment
-Opposite muscle movements expel air from lungs
-Exhalation starts when diaphragm and rib muscles relax, volume of chest cavity and lungs decreases, air pressure inside lungs increases, air moves from lungs to lower pressure environment outside the body
-Change in air pressure causes air to move from an area of high pressure (lugs) to an area of lower pressure (outside the body)
THE SPIROGRAPH
SPIROGRAPH – graph representing the amount (volume) and speed (rate of flow) of air that is inhaled and exhaled, measured by a spirometer
-Represents the amount of air that moves in/out of the lungs with each breath
TIDAL VOLUME – volume of air inhaled and exhaled during normal breathing movement when the body is at rest
INSPIRATORY RESERVE VOLUME – the additional volume of air that can be taken into the lungs beyond a tidal inhalation
EXPIRATORY RESERVE VOLUME – additional volume of air that can be forced out (expelled) from the lungs beyond a tidal exhalation
VITAL CAPACITY – total maximum volume of air that can be moved in/out of the lungs during a single breath (tidal volume + inspiratory reserve volume + expiratory reserve volume)
RESIDUAL VOLUME – volume of air that remains in the lungs/passageway after a complete exhalation
-This gas never leaves the respiratory system, if it did, lungs/respiratory passageways would collapse
-Residual volume has little value for gas exchange because it isn’t exchanged with air from outside the body
SECTION 11.2 – THE HUMAN RESPIRATORY SYSTEM: A CLOSER LOOK
-Humans: lungs are the main organs of respiration
-Respiratory tract is a passage necessary for air to move from outside the body to the respiratory surface inside the body
THE PASSAGE OF AIR THROUGH THE UPPER RESPIRATORY TRACT
-Air enters respiratory system through nostrils, can also enter through mouth especially if breathing is rapid
-Air is warmed and cleansed of dust/small particles inside the nasal passages at the back of the nose
-Thin bones, turbinate bones, project into the nasal passages and increase the surface area of these chambers
-Thin membrane covering the turbinate bones secretes mucus, moistens air and traps particle of dust, bacteria, other foreign matter
-Ciliated cells found in the membrane have waving hair-like projections that move the trapped particles into the nose or throat where they can be expelled by sneezing/coughing
-Dense network of capillaries in lining of turbinates supplies warm blood to the nasal passages, heats air in nasal passages to body temperature, protects delicate structures in the lower respiratory tract from damage by cold air
-Warm, cleaned, moist air passes from the nasal passages through the pharynx (throat)
PHARYNX – passageway just behind the mouth that connects the mouth and nasal cavity to the larynx and esophagus
-Base of pharynx, behind the tongue, is the entrance to the trachea (windpipe)
TRACHEA – tube that carries air from the nasal passages or mouth to the bronchi, and then to the lungs
-Opening of the trachea is called the glottis
GLOTTIS – opening of the trachea through which air enters the larynx
-Glottis can be closed by the epiglottis, which is normally upright to allow air to pass freely into the trachea
-When you swallow food, epiglottis covers the glottis to prevent food from entering the trachea into the lungs
THE LARYNX
-Between the glottis and trachea, air passes through larynx (voice box)
LARYNX – structure between glottis and trachea that contains vocal cords
-Structure is made of cartilage, rough, firm connective tissue
-Larynx used for producing sound in mammals
-Vocal cords consist of 2 folds of membrane stretched across the larynx
-During normal breathing, muscular tissue holds vocal cords apart, air passes freely through larynx
-To make sounds, vocal cords move closer together so the pressure from air expelled from the lungs causes the cords to vibrate
-Pitch of sound varies with length of the vocal cords
-Long cords produces a long sound, Shorter cord produces a higher sound
-At puberty, vocal cords of males grow quickly, often causes “breaking” quality in voice
-Breaking sound disappears once the vocal cords are finished growing
-Air moves down trachea after passing through the larynx
-Flexible tube is strengthened and held open by semicircular loops of cartilage
-Trachea: 10-12cm in length, runs from throat to middle of chest, then splits into 2 branches
LOWER RESPIRATORY TRACT
-2 tubes that branch from the trachea called bronchi (singular bronchus)
BRONCHUS – passageway that branches from the trachea to the lungs
-One bronchus enters each lung
-Humans: lungs divided into regions called lobes
-Right lung has 3 lobes, left lung has 2 to leave space for the heart in the thoracic cavity
-Each lung surrounded by a thin, flexible, double layered sac called pleural membrane
-Outer layer of this membrane attached to the inside of the chest wall, inner layer covers lungs
-Thin space between these 2 layers contains lubricating fluid that allows layers to slide easily against each other during the movements of breathing
-Inside lungs, each bronchus subdivides many times to form bronchioles
BRONCHIOLES – the passageway that branches from each bronchus inside the lung into increasingly smaller thin-walled tubes
ALVEOLI – (alveolus) tiny sac, with a wall that is one cell thick, found at the end of a bronchiole; respiratory gases are exchanged in this sac
-Estimated 500 million alveoli in an average adult human lung
-Network of fine capillaries and walls of alveoli are only one cell thick
-Must have thin membranes so that the respiratory/circulatory system can interact; oxygen from air diffuses into the blood and carbon dioxide from the blood diffuses into the lungs
DETAILED LOOK AT GAS EXCHANGE IN HUMANS
-During external respiration, thin walls of alveoli and capillaries allow gases to diffuse through their cell membranes easily
-Air that enters the alveoli after inhalation has a higher concentration of oxygen than the blood in the capillaries next to the lungs (oxygen in blood in capillaries has diffused out of the tissue cells)
-Oxygen diffuses out of the alveoli into the blood in the capillaries
-Blood in the capillaries has a higher concentration of carbon dioxide than the air in the alveoli as blood that diffuses into the capillaries is returning from the body tissue cells
-Thus carbon dioxide diffuses into the alveoli fro the capillaries
-Carbon dioxide is exhaled into air
-Once oxygen and carbon dioxide exchange has occurred between the capillaries and alveoli, blood in the capillaries goes back to the heart then to the tissue cells
-Oxygen diffuses from the blood into the tissue cells and is exchanged for carbon dioxide once again
HOW BLOOD TRANSPORTS RESPIRATORY GASES
-During respiration, both oxygen and carbon dioxide are transported through the bloodstream
-99% of oxygen that reaches cells is carried by hemoglobin
HEMOGLOBIN – an iron containing protein found in red blood cells, which binds to and transports oxygen from the lungs to the rest of the body
-1% dissolved in the watery blood plasma
-When carbon dioxide leaves tissue cells and diffuses into the capillaries, it enters the red blood cells
-23% of carbon dioxide is carried in the blood by hemoglobin
-77% carried by blood fluids
-When carbon dioxide reaches the lungs, it diffuses into the air in the alveoli and is exhaled
11.3 RESPIRATORY SYSTEM DISORDERS
-Similar to the digestive system the respiratory system links the internal environment of the body with the outside environment
-Quality of both environments plays a key role in the health of the respiratory system
–Changes outside the body can influence how well the respiratory system functions and how well the whole body functions
DISORDERS OF THE UPPER RESPIRATORY TRACT
-Most common throat ailments caused by viruses and bacteria carried in the air
TONSILLITIS – an infection of the tonsils caused by a virus or by bacteria
TONSILS – 2 oval shaped organs located in the pharynx at the back of the throat
-Function of tonsils to help prevent bacteria and other harmful substances from entering the respiratory system
-Symptoms: red, swollen tonsils, sore throat, fever, swollen neck glands
-Tonsils are naturally large in children but shrink with age
-Severe tonsillitis treated surgically by removing all or part of the tonsils
-Removing tonsils can increase the risk of throat infections later in life
LARYNGITIS – inflammation of the larynx that can cause the voice to be raspy or hoarse, caused by infection, allergy or overstraining the voice (prolonged yelling)
-Larynx contains vocal cords
-When larynx is inflamed, vocal cords cannot vibrate as they usually do, thus people may lose their voice or speak in a hoarse whisper
-Not serious, clears up on its own after a few days
DISORDERS OF THE LOWER RESPIRATORY TRACT
-Can damage the bronchi and lungs
-Public Health Agency of Canada estimates that over 3 million Canadians of all ages are affected by chronic respiratory diseases
-Several main causes of respiratory disorders:
- Exposure to air pollutants that block parts of the respiratory tract, obstructing airflow or impeding exchange of gases
- Exposure to infections pathogens (viruses, bacteria, fungi)