BIOL 118 1st Edition Lecture 24Outline of Last Lecture I. IntroductionII. Form, Function & AdaptationIII. TissueIV. Organ & Organ SystemsV. Surface Area/Volume RelationshipsVI. Homeostasis VII. Heat ExchangeOutline of Current Lecture I. IntroductionII. Respiratory & Circulatory SystemsIII. O2 & CO2 BehaviorIV. GillsV. Insect TrachaeVI. Vertebrate LungsVII. Blood VIII. Circulatory SystemsCurrent LectureIntroduction- Oxygen required for, & carbon dioxide produced by, cellular respiration must be continuously exchanged with the environmento These gases must be transported throughout the bodyo Cells must obtain oxygen & expel carbon dioxide continuously to support ATP production by mitochondria- Gas exchange involves 4 steps:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.o Ventilation: occurs when air or water moves through a specialized gas-exchange organ, such as lungs or gillso Gas exchange: takes place as CO2 & O2 diffuse between air or water and the blood at the ventilator surfaceo Circulation: dissolved O2 & CO2 are transported throughout the bodyo Cellular respiration: gas exchange between blood & cells occurs in tissues, whererespiration occurs, & O2 & CO2 diffuse between blood & cellsRespiratory& Circulatory Systems- Respiratory system: accomplishes ventilation & gas exchange- Circulatory system: responsible for moving O2, CO2 & other materials around the body- In some animals gas-exchange surface is the skin, but in most species it is located in a specialized organO2 & CO2 Behavior- Gas exchange between environment& cells is based on diffusiono Oxygen is high in the environment & low in tissueso Carbon dioxide is high in tissues & low in the environmento Partial pressure: pressure of a particular gas in a mixture of gases To calculate: multiply the fractional composition of that gas by the total pressure exerted by the entire mixture (Dalton’s law) The diffusion of oxygen & carbon dioxide is dependent upon the partial pressure gradient- move from high partial pressure to regions of low partial pressure- Water has less available oxygen than airo Is about a thousand times denser than air & flows less easilyo Water breathers have to expend more energy to ventilate their respiratory surfaces than do air breathers- Amount of gas that dissolves depends on several factorso The solubility of the gas in water o The temperature of the watero Presence of other soluteso Partial pressure of the gas in contact with the water- Partial pressure of oxygen varies in different types of aquatic habitatso Habitats with large numbers of photosynthetic organisms tend to be relatively oxygen richo Habitats where most organisms live off existing organic material tend to be oxygen poor- Many small animals exchange gases by direct diffusion across the body surfaceo Mainly live in wet environments- Large animals, or those that live in dry environments, need a specialized organ for gas exchangeo Respiratory organs provide a greater surface area for gas exchange- Fick’s law o States that rate of diffusion of a gas depends on: Solubility of the gas Temperature Surface available for diffusion Differences in partial pressures of the gas across the gas exchange surface Thickness of the barrier in diffusiono Identifies traits that allow animals to maximize the rate at which oxygen & carbon dioxide diffuse across surfaces Surface area for gas exchange is large Respiratory surface is extremely thin Partial pressure gradient of the gas across the surface is largeGills- Gills: Outgrowths of the body surface or throat, used for gas exchange in aquatic animalso Present an extremely large surface area for oxygen to diffuse across an extremelythin epithelium- Structure can be extremely diverse; can be internal or externalo Fish gills are located on both sides of head is teleosts consisting of four arches Bony fish have internal gills- water must be driven over them by ventilation Most fish ventilate gills by opening & closing their mouths & the operculum (stiff flap over the gills) Particularly fast swimmers force water through their gills by swimming with their mouths open (ram ventilation)- Structureo Movement of water over gills is in one direction- water must flow over gills in order for gases to be exchangedo Gill filaments: long, thin structures the extend from each gill archo Each gill filament is composed of hundreds or thousands of gill lamellae (sheet-like structures) Bed of small blood vessels called capillaries runs through - Countercurrent system o Flow of blood through the capillaries is in the opposite direction to the flow of water over gill surface- countercurrent exchange in each lamellao Creates large partial pressure of oxygen & the carbon dioxide in water over blood= efficient gas exchangeInsect Trachae- Trachea: air-filled tubeso Open to the outside through pores called spiracles- Air moves into trachea & then by diffusion into cellso Sufficient to exchange gases in small insectsVertebrate Lungs- In terrestrial animals, air enters the body through the mouth & noseo Trachea carries inhaled air to narrow tubes called bronchi Bronchi branch off into even narrower tubes called bronchioleso Organ for gas exchange is the lung Encloses the bronchioles & portions of the bronchi Frogs & amphibians: simple sac lined with blood vessels Mammals: divided into tiny sacs called alveoli, greatly increase surface area for gas exchange- Alveoli provide an interface between air & blood that consists ofo Thin aqueous filmo Layer of epithelial cellso Some extracellular matrix materialo Wall of a capillary- Actively ventilate lungs by pumping air via muscular contractionso Positive pressure ventilation Frogso Negative pressure ventilation Humans & other mammals Pumping achieved by diaphragm muscle- Human Lungso When diaphragm moves down, air in chest cavity is lowered & air moves ino As diaphragm relaxes, chest cavity decreases & air is exhaled Passive process driven by elastic recoil of the lungs & chest wall as the diaphragm & rib muscles relaxo 450 mL of air moves in & out of lungs in average breath 150 mL of this occupy dead space- portions of air passages that do not have respiratory surface- Bird lungso Able to extract enough oxygen for extremely long flights & flights at high elevationso 4 General steps
View Full Document
Unlocking...