Zoology 101: Animal Biology Last Lecture Outline Lecture 22 1 Small intestine2 Large Intestine3. Respiration4. Beginning of Tracheal systemCurrent Lecture 1. Lungs/gas exchange in the lungs2. Circulatory system3. Blood Lungs/Gas exchange in the Lungs • Adapted for gas exchange in terrestrial environments • Innerfoldings of the throat • In mammals, birds, reptiles, and amphibians • Respiratory surface= alveoli (air sacs)◦ gas exchanged in alveoli • Cilia lining bronchi and bronchioles = trap and brush up inhalants• Gas exchange in blood◦ inhale oxygen rich air, carbon dioxide diffuses out of blood and into alveoli to be exhaled. ◦ Deoxygenated blood flows under alveoli◦ oxygenated blood flows to body tissues ◦ Film of liquid in lungs contains surfactants • Breathing ventilates our lungs ◦ negative pressure breathing- we PULL air into lungs ◦ Diaphragm moves down to pull air in◦ increases volume in chest cavity, lowers pressure, allows air to flow down pressure gradient ◦ Exhale- diaphragm relaxes ( moves up), pushing the air out • Not entirely efficient: ◦ Tidal air flow: 2 way flow ▪ gas exchange doesn't occur across entire respiratory surface ◦ Mixing of fresh and 'dead' air ▪ residual volume: mixes with air that has already been deoxygenated • Birds ◦ respiratory surface: parabronchi (air tubes)◦ Inhalation: air sacs fill, exhalation: air sacs completely empty → lungs fill ◦ Huge surface area ◦ one way flow of respiratory medium (through lungs)◦ Crosscurrent exchange: gas exchange along entire respiratory surface, perpendicular blood vessels• Most efficient to least efficient: countercurrent (fish), crosscurrent (birds), tidal (humans), tracheal (bugs) Circulatory System • delivers nutrients, gases, removes wastes, connects exchange surfaces with cells in complex animals • Simple animals ◦ no specialized system needed ◦ diffusion meets demand • More complex animals have circulatory system• Both: circulating fluid (blood or hemolymph), set of tubes, muscular pump (heart) • Arthropods and most molluscs ◦ Open circulatory system ▪ vessels open to body cavity ▪ hemolymph bathes organs directly ▪ tubular hearts ▪ heart pushes hemolymph, heart relaxes and hemolymph flows back into the heart • Closed circulatory system ◦ blood is contained in vessels ◦ interstitial fluid bathes organs ◦ heart pushes blood from arteries (away from heart) into tissues which have capillaries ◦ Capillaries → covey blood between arteries and veins within each organ (exchange occurs here), thin walls ◦ large surface area◦ blood goes back to the heart via veins → one way valves ◦ systemic capillaries: surrounds most other tissues Blood• Transports oxygen • in humans, Red blood cells (RBCs) develop from stem cells in bone marrow; they mature, lose their nuclei, mitochondria, and most organelles, becomes filled with hemoglobin (hb: respiratory pigment which allows us to be active) • Hb carries oxygen; it is a quaternary protein, made of 2 betas and 2 alphas, heme binds and iron, carries 4 oxygen • oxygen binds to Hb reversibly, meaning oxygen can bind and unbind • cooperativity in oxygen binding◦ oxygen binds to one subunit → other 3 subunits increase in affinity for oxygen ◦ Oxygen leaves one subunit → other 3 subunits can readily unload the oxygen • Carbon dioxide:◦ some stays dissolved in plasma (least common)◦ some gets picked up by hemoglobin ◦ most common- reacts with water in RBCs and is then carried as bicarbonate in plasma (HCO3-) • Extreme cardiovascular systems:◦ High altitudes ▪ large heart and lungs ▪ many RBCs → more hb for more oxygen transport ▪ RBCs have a higher Hb concentration▪ Hb has a high affinity for oxygen but not too high because it needs to be released into the tissues ◦ Diving ▪ large blood volumes ▪ many RBCs → oxygen storage ▪ RBCs stored in slpeen ▪ Muscles contain myoglobin: oxygen binding protein, intracellular oxygen reservoir ▪ glide in water → uses less
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