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Unit 5 THE BREATH OF LIFE TRANSPORT AND CIRCULATION NUTRIENTS AND DIGESTION TODAY THE BREATH OF LIFE! Cellular Respiration The opposite of photosynthesis. 8.1 – The Task of Respiration • 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 exit the cell. • 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: • 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. • • 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) Hydra, planarian, and ameoba. • PROBLEMS with being multicellular: • Diffusion is only effective over a distance of a few cells. • 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 MAMMALIAN GAS EXCHANGE Be able to distinguish between the following terms: • Breathing • Gas Exchange – External – from air in lungs to capillaries (circulatory system) – Internal – from circulatory system to body cells. • 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: • Large surface area to maximize O2 exchange • Moist surface area for diffusion • 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 Major parts of the respiratory System Upper Respiratory Tract & Lower Respiratory Tract. Upper 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 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) • 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) REVIEW QUESTIONS Respiratory System Handouts Page 255, #1, 2, 3, 4, 5, 6. Page 259, # 1, 2, 3, 4. Read Page 262-263, copy figure 8.20, and briefly define each term in the figure.