SBI3U UNIT 3 – Internal Systems Gas exchange / Respiratory systems Transport / Circulatory systems Digestive systems Pig Dissection multi-celled organisms require coordinated systems in order to supply the specialized cells with materials they require (and removal of waste materials) SBI3U The Breath of Life Recall: Aerobic organisms require Oxygen (O2) O2 is necessary for cellular respiration releases energy to drive all cellular functions CO2 is the waste product of cellular respiration that must be disposed of Gas Exchange: the process that ensures O2 enters each cell of an organism and CO2 can leave each cell. Gas exchange systems/Respiratory systems vary for different organisms but all must have TWO requirements: 1. Surface Area: Must be large enough for enough O2 to enter and CO2 to leave in order to meet the metabolic needs of the organism. 2. Moist Environment: Allows for gas exchange to take place since O2 and CO2 must be dissolved in order to be transported SIMPLE GAS EXCHANGE (Respiratory) SYSTEM: Unicellular organisms – eg. amoeba, algae Exchange gas through membrane by diffusion Membrane must be moist (live in moist environment) Larger Multicellular organisms Require specialized systems ! greater need for O2 and greater distance O2 must travel to reach all cells PROBLEMS with being multicellular: 1. Diffusion is only effective over a distance of a few cells. 2. As the body surface becomes more specialized, the surface area available for gas exchange is reduced. SOLUTIONS: Specialized Respiratory Systems Skin Respiration eg. earthworms, leeches (see textbook p. 252) Skin must remain moist Skin lined with tiny capillary vessels O2 carried through circulatory vessels to other cells of the organism Gills eg. fish, crayfish (see textbook p. 253) Structural changes increase the surface area of the body parts involved in gas exchange Mechanism has evolved which enables the organism to ventilate this surface oxygen-containing aquatic medium moves over respiratory surface Example: fish gills feathery tissue structures consisting of numerous delicate branches ensures a large surface area in a limited space connected to vascular system to transport O2 and CO2 to and from cells What about Terrestrial Organisms? they have an internal gas exchange system BREATHING: is an important process as it forces O2 across the gas exchange surface. It relies on a basic law of physics air moves from a region of high pressure to a region of low pressure until equilibrium is reached. (see textbook p. 254) Tracheal Respiratory System eg. insects like grasshoppers An internal system allows to maintain a moist environment Consists of external pores called “spiracles” controlled by valves Connected to internal network of tubes called “tracheae” Air is ventilated via contraction and relaxation of the abdomen (Breathing) Note: The circulatory system is separate from the respiratory system branches of tracheal tubes ensure contact with the cells SBI3U HUMAN GAS EXCHANGE Be able to distinguish between the following terms: Breathing Gas Exchange Cellular Respiration The Gas Exchange System: What is its overall function? To supply cells with O2 and to remove CO2 Note: there is a need for a circulatory system to transport the gases to and from the cells Why is our system highly specialized? Since we are warm blooded must maintain constant internal temp. To maintain the temp requires lots of energy lots of O2 is needed for cellular respiration Our Gas Exchange System must have: 1. Large surface area to maximize O2 exchange 2. Moist surface area for diffusion 3. Ventilation Mechanism force O2 across lung surface Therefore: Breathing Gas Exchange Cellular Respiration What is inhalation? Inspiration? breathing in What is exhalation? Expiration? breathing out INHALATION – Journey through Respiratory Tract Upper Respiratory Tract: Why does it usually take place through the nose? Nose hair filters dust from air Capillaries close to surface warm the air Mucus moistens the air Where does air go after the nose? Pharynx opening to digestive system (esophagus) opening (glottis) to gas exchange system (trachea) Note: Why don’t we choke when we eat? epiglottis closes over trachea when swallowing What adaptations does the trachea have? Why? Larynx voice box Mucus/Cilia move dust and foreign particles out of lungs Cartilage Rings to maintain an open airway Lower Respiratory Tract: After the trachea, where does the air go? Bronchi (two branches of the trachea) branches further to “Bronchioles” What is the actual site of Gas Exchange? ALVEOLI grape-like cluster of tiny sacs at the end of each bronchiole kept moist for gas exchange sac wall is a thin membrane (1 cell thick) capillary bed (containing blood) surrounds air sac Structure of Lungs: Where are the lungs located? Why? in the pleural or chest cavity protected by ribs What stops the lungs from collapsing? Pleural membrane surrounds lungs two layers with lubricating fluid between them Elastic connective tissue fills the spaces in between the structure Alveoli lined with a lubricating film How many lobes does each lung have? Right lung 3 lobes Left lung 2 lobes How does enough air get down to the alveoli? By “Breathing Movements” (see text p. 260, coursepack p. 41) GAS EXCHANGE – Some More Details O2 and CO2 are exchanged across the cell membrane. Alveoli and adjacent capillaries are only one cell thick. Inhaled Air contains: ~ 20.94 % O2 ~ 0.04 % CO2 Oxygen diffuses into blood from the alveoli (by simple and facilitated diffusion) Exhaled Air contains: ~ 16.49 % O2 ~ 4.49 % CO2 (CO2 diffuses out of the blood into the alveoli)