Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 22 Organismal Respiration – The Exchange of Gases 1) Intro a) gas exchange or respiration i) interchange of O2 and the waste product CO2 between an animal and its environmen 2) Overview: Gas exchange involves breathing, the transport of gases, and the servicing of tissue a) organismal respiration makes it possible for animals to put the food molecules of digestion to work b) Figure 22.1 i) breathing (1) respiratory surface – thin, moist (2) diffusion of O2 across cells into blood (3) diffusion of CO2 across cell into lungs ii) transport of gases by circulatory system (1) O2 binds to hemoglobin within RBCs (2) carries O2 to body tissues (3) CO2 carried in blood from body tissues to lungs iii) tissue cells take up O2 from blood and release CO2 (1) O2 is final electron acceptor in ETC (2) CO2 is breakdown product of oxidized food molecules 3) Respiratory Surface a) site where O2 diffuses in and CO2 out of animal b) living cells, usually single layer (simple epithelium) c) wet (moist) plasma membranes i) O2 must dissolve in water before diffusing into cell d) large surface area to interact with a lot of O2 and get rid of a lot of CO2 e) Figure 22.2 – four types of respiratory surfaces i) yellow is resp. surface ii) green area has nothing do to with respiration iii) Earthworm resp. surface (a)entire outer skin (“skin-breathers”) (b) skin-breathers must live in damp places or water (c)most skin-breathers are small and long/flat – why? (d) most animals don’t have enough skin surface or surface is covered in dead cells like humans or some other impermeable material. iv) aquatic animals – gills (1) extensions of body surface that interact with water v) terrestrial animals (1) respiratory surfaces folded into body (2) Insects (a)tracheae (plural) – extensive branching networks (3) vertebrates (a)lungs – extensive branching with many internal sacs for gas exchange 4) Gills are adapted for gas exchange in aquatic environments a) gill surface greater than whole body surface b) tiny blood vessels covered with one or a few layers of cells i) blood cells must travel single file through vessels c) Advantage: always wet (they live in water) d) Problem: not as much O2 in water as in air (3-5% that of air) i) warmer and saltier, the less O2 ii) bottom line: gills must be efficient e) Figure 22.3 i) 4 gill arches on each side of body ii) 2 rows of gill filaments from each arch iii) each filament has platelike structures called lamellae iv) lamellae are the respiratory surfaces v) blue arrows represent flow of water vi) ventilation – mechanism by which water or air with O2 are brought to respiratory surface (1) fish inhales and gill covers (opercula) close (2) exhales by closing mouth, pumping water over gills, and opening opercula to let water escape (3) a lot of energy is spent ventilating gills (dense water, low O2 content) vii) countercurrent flow - water flow is opposite blood flow (22.4) (1) enhances O2 transfer (2) countercurrent exchange – transfer of something in fluid moving in opposite directions (3) opposite flows maintain a diffusion gradient (4) allows fish to remove >80% of dissolved O2 in water 5) Tracheal system of insects provides direct exchange between the air and body cells a) advantages to breathing air i) air has higher O2 content than water ii) air is lighter and easier to move than water (1) costs less energy to ventilate lungs than aquatic b) Main problem i) loss of water to the air by evaporation c) tracheal system of insects (Figure 22.5B) i) air tubes that branch throughout body ii) tracheae – largest tubes (1) open to outside and reinforced by chitin iii) tracheoles – narrowest tubes (1) extend to nearly every cell in body (2) tips contain fluid (3) gases dissolve in fluid and diffuse across tips (4) RESULT: circulatory system NOT involved iv) air sacs (1) enlargements near large organs that require a large O2 supply (2) muscles contract around air sacs and air is pumped into and out of body 6) Terrestrial vertebrates have lungs a) Reptiles, birds, mammals and many amphibians b) restricted to one part of body i) circulatory system must be used to transport gases c) amphibians i) small lungs ii) some lack altogether iii) rely on diffuse across body surfaces (1) supplements gas exchange in lungs d) most reptiles, birds, mammals rely on lungs e) turtles are acception (1) shells prevent breathing movements (2) gas exchange occurs in mouth and anus f) size and complexity correlated with metabolic rate i) endotherms (warm-blooded) have greater surface areas than ectotherms (cold-blooded) g) humans (Figure 22.6A) i) surface area = 100m2 (racquet ball court) ii) lungs in chest cavity iii) diaphragm – sheet of muscle at bottom of cavity iv) Respiratory Path (1) Air enter nostrils (2) Nasal Cavity (a)filtered by hairs (b) warmed (c)humidified (d) sampled for odors (3) Mouth breathing skips nasal processing (4) pharynx (5) larynx – voice box cords – voluntary tense muscles and stretch cords to make them vibrate = sound (i) high pitch – high tension (ii) low pitch – low tension (6) trachea (windpipe) (a) shape maintained by rings of cartilage (keeps from collapsing) (i) like vacuum cleaner hose rings (b) goblet cells – secrete mucous (c)ciliated columnar cells – cilia push mucous up into pharynx to be swallowed (i) mucous traps fine particles/ dirt/ mircoorganisms in air (7) forks into bronchi (plural) (8) bronchus branches and branches to bronchioles (fine tubes) (a)upside down tree (9) bronchioles dead end in alveoli (plural) – grapes on tree (a)each lung contain millions (b) each alveolus lined by simple cuboidal epithelium = respiratory surface (c)O2 dissolves in film of moisture and then diffuses across epithelium and into capillary. CO2 goes opposite way. (Fig. 22.6C) (a)vocal 7) Smoking is one of the deadliest assaults on our respiratory system a) Tobacco smoke i) 4,000 chemicals in a single drag ii) 43 known carcinogens iii) smoke destroys cilia and macrophages that fight microorganisms (1) more toxins now reach alveoli (2) coughing then becomes the systems method of cleansing itself iv) 430,000 people a year die from smoking (1) lung cancer (Figure 22.7AB) v) increased risk of other cancers vi) emphysema – alveoli become brittle and many rupture (1) lungs can’t exchange gas as well (2) RESULT: breathless and consistent fatigue (3) more energy diverted for breathing (4) heart has to work harder to pump more blood (a)leads to heart disease vii) every cigarette estimated at 5 minutes of life lost viii) second hand smokers also at risk 8) Breathing ventilates lungs a) breathing – alteration of inhaling and exhaling (Fig. 22.8A) i) diaphragm contracts, moving down ii) muscles b/w ribs contract expanding rib cage iii) negative pressure breathing (1) increasing volume of chest cavity lowers air pressure in lungs below atmospheric pressure (2) higher pressure air rushes in iv) exhale is opposite of inhale (Fig. 22.8A) v) typical breathe is 500ml of air vi) 4 million to 10 million breathes/year b) vital capacity – max volume of air one can inhale i) 3400ml females (college age) ii) 4800ml males (college age) c) residual volume i) you can’t have zero air in your lungs ii) air left over after exhaling as much as possible d) Total air volume = vital + residual volume e) Birds (Fig. 22.8B) i) one-way flow of air ii) several air sacs in addition to lungs iii) air sacs don’t do gas exchange (1) both air sacs fill during inhalation (2) posterior sac gets fresh air (3) anterior sac gets air from lungs (4) during exhale both sacs deflate (a)posterior sac enters lungs (b) anterior sac leaves mouth (5) no alveoli in lungs, but parallel tubes (.5mm across) (a)blood flow in opposite direction (countercurrent) (6) one way means no residual volume (7) birds get 5% more air than humans 9) Breathing is automatically controlled a) some conscious control b) involuntary most of the time i) automatic control centers in brain (1) ensures coordination b/w resp and circ. system and body metabolic needs (2) breathing control centers (a)found in pons and medulla oblongata (medulla) (i) nerves from here trigger contraction of respiratory muscles (ii) 10-14 inhalations per minute (iii)pons smoothes out signal from medulla (iv) medulla 1. monitors CO2 levels in blood by watching blood pH a. CO2 + H20 H2CO3 (carbonic acid) b. CO2 is high then there is more H2CO3 and pH goes down c. medulla speeds up breathing ii) hyperventilating (1) excessively taking rapid, deep breathes (2) hard on your body (3) purges blood of CO2, pH rises, control center stops sending signals to breathe – breathing stops until more CO2 produced and pH decreases c) O2 used when CO2 is formed (cellular resp) i) indirectly measure O2 when you measure CO2 ii) Some large arteries have O2 sensors that signal medulla d) Breathing centers are only effective if coordinated with circulatory system i) breathing faster will not get O2 to your cells faster 10) Blood transports the respiratory gases, with hemoglobin carrying the oxygen a) need to understand circulatory system (Fig. 22.10A) i) heart (1) right side handles oxygen poor blood from body and sends to lungs (2) left side handles oxygen rich blood from lungs and sends to body ii) gases diffuse along pressure gradients (1) pressure of a gas increases with (a)more molecules per unit volume (b) higher temperature (2) total pressure of a gas equals the sum of the pressure of each gas in the mixture (3) gases diffuse down their partial pressure gradients iii) oxygen is transported bound to hemoglobin in RBCs (1) very little dissolves directly in blood (2) 4 hemes, each with an iron that binds one oxygen (total of 4 per hemoglobin) (3) carries O2 from alveoli to tissue iv) hemoglobin also helps (Fig. 22.11AB) (1) transport CO2 (a)CO2 diffuses out of tissue, into blood plasma and into RBC (b) Some binds to hemoglobin (c)rest forms H2CO3 with the help of enzyme carbonic anhydrase (d) very small amount dissolves in blood plasma (2) buffer blood (prevent drastic pH changes) (a)picks up H+ when H2CO3 is formed (b) H2CO3 becomes HCO3- (bicarbonate), which diffuses out of RBC into blood (i) HCO3- buffers the blood (c)At alveoli, HCO3- turns back to CO2 and is removed The human fetus exchanges gases with the mother’s bloodstream a) amniotic fluid – fluid surrounding fetus b) lungs full of amniotic fluid – not functioning c) placenta i) composite organ – made of tissues from both fetus and mother (1) fetal blood vessels from umbilical cords interact with maternal blood vessels (2) fetal hemoglobin (a)special hemoglobin with higher O2 affinity than adult hemoglobin d) When baby is born i) CO2 stops diffusing into placenta ii) CO2 levels rise and pH drops in fetal blood iii) stimulates control center in brain iv) signals sent to diaphragm and rib cage muscles to start breathing 11)