circ./gas ex. gas exchange chapter 44

Transcription

1 circ./gas ex. chapter 44 gas exchange Gas exchange (respiration?) provides O removes CO respiratory medium atmosphere is ~1% O (by volume). Pi of O = ~160mmHg Pi of CO = ~0.3 mmhg Dalton s Law higher altitudes - hypoxia, hypoxemia respiratory rate goes up heart rate goes up AMS? respiratory surface CO and O move by diffusion. moist, thin, large surface area complexity of respiratory surface size of the organism aquatic or terrestrial metabolic demands endotherm vs. ectotherm rate of diffusion = k x A x (P - P1) D

2 skin? simpler organisms Gas exchange occurs over the entire surface area sponges, cnidarians, and flatworms cutaneous breathing (amphibians, earthworms) moist skin highly vascularized high SAV ratio gills aquatic respiratory organs surface area of gills > rest of the body Water as a respiratory medium: moisture? O concentrations low in HO gills must be very efficient Ventilation necessary in water Crayfish and lobsters energy associated with ventilation? RAM ventilation countercurrent exchange. maximizes diffusion gradient Lamella Gill arch Blood vessels Water flow between lamellae Countercurrent exchange Gill filaments Net diffusion of O from water to blood P (mm Hg) in water O P (mm Hg) in blood O

3 terrestrial animals air has many advantages over water. more O ventilation? less energy to ventilate problems: water loss. tracheae tracheal system of arthropods ventilation flight muscles air s Air s Tracheae spiracle Tracheoles Body cell Tracheole Air Air lungs lungs interfaces with circulatory system closed circulatory capillaries line respiratory surface. open circulatory spiders, terrestrial snails, and vertebrates. Trachea Body wall amphibians some lack lungs altogether frog (plethodontidae) skin breathing very important positive pressure breathing salamander

4 pulling air human lungs negative pressure breathing (e.g. mammals and reptiles) visceral pump? Air inhaled Rib cage expands as rib muscles contract Rib cage gets smaller as rib muscles relax Air exhaled system of branching ducts nasal, sinus passages warmed and humidified olfaction. trachea bronchi bronchioles alveoli pleural cavity thin space filled with Lung Diaphragm INHALATION Diaphragm contracts (moves down) tidal volume (~500 ml) EXHALATION Diaphragm relaxes (moves up) fluid surface tension, adhesion and cohesion of water diaphragm Birds -- continuous breathing eight or nine air s; parabronchi vital capacity (3.4 L and 4.8 L) residual volume air anterior air anterior air lung posterior air Inhalation: air s fill air lung posterior air Exhalation: Air s empty, lungs fill parabronchi

5 rate and depth of breathing autonomic regulation negative-feedback via stretch receptors breathing control centers medulla oblongata and the pons ph hypercapnia? CSF breathing control centers O sensors O levels? O sensors in aorta and carotids CO and O - negatively correlated. hyperventilation removing CO? respiratory pigments hemocyanin hemoglobin four subunits (heme groups) O loading bohr shift CO amino groups simpler organisms gastrovascular cavity e.g. cnidarians, flatworms basic circulatory setup circulatory fluid a set of tubes muscular pump Exchange Exchange

6 open vs. closed Heart vessels open circulatory systems hemolymph hemocytes exchange -> hemolymph and cells e.g. arthropods, mollusks (some) closed circulatory systems separate blood, lymph exchange -> capillaries and interstitial fluid e.g. vertebrates, cephalopods (squid and octopus), annelids (segmented worms) Interstitial fluid Dorsal vessel (main heart) Hemolymph in sinuses surrounding organs Pores Heart Tubular heart Blood Small branch vessels In each organ cardiovascular system heart 1- atria 1- ventricles three main kinds of blood vessels. Arteries capillaries networks of capillaries infiltrate each tissue. Veins Artery Artery SEM Red blood cell Endothelium Smooth muscle Connective tissue Arteriole Vein 100 µm Capillary Basal lamina Endothelium Smooth muscle Connective tissue Venule 15 µm Vein Valve Capillary LM Auxiliary hearts Ventral vessels capillaries shunting: smooth muscle layer constricts pre-capillary sphincters exchange endocytosis on one side, exocytosis on the other diffusion Precapillary sphincters Thoroughfare channel Capillaries Arteriole Venule Sphincters relaxed Physical laws governing the movement of fluids law of continuity same laws govern traffic flow Arteriole Venule Sphincters contracted

7 gill capillaries systemic capillaries 3V Right Lung capillaries pulmocutaneous circuit Systemic capillaries fish heart ( chambered heart) A two capillary beds - the gill and systemic capillaries. 3-chambered (amphibians, most reptiles) two atria double circulation 4-chambered heart (crocodilians, birds, and mammals) complete double circulation important adaptation for endotherms (need 10X O) A V Left aorta 4 A V Right Lung capillaries Pulmonary circuit Systemic circuit Systemic capillaries A V Left heart heart anatomy two atria -- (auricles) two ventricles -- Four in the heart two atrioventricular (AV) (left=mitral; right=tricuspid) Two sets of semilunar Semilunar valve Right atrium Tricuspid valve Pulmonary artery Right ventricle Left ventricle Aorta Pulmonary artery Left atrium Semilunar valve Mitral valve AV open Atrial and ventricular diastole 1 Semilunar closed 0.4 sec 0.1 sec 0.3 sec AV closed Atrial systole; ventricular diastole Semilunar open Ventricular systole; atrial diastole 3 cardiac cycle contraction phase = systole relaxation = diastole normal resting pulse = 75 bpm Cardiac output depends on factors: heart rate pulse (indirect measure) stroke volume resting cardiac output blood components plasma (about 90% water) water nutrients, waste products respiratory gases hormones electrolytes plasma proteins cellular elements Basophil Neutrophil cell type erythrocytes leukocytes Eosinophil platelets Lymphocyte Monocyte number (per mm 3 of blood) functions 5-6 million transport O and CO defense and immunity 50, ,000 blood clotting

8 cellular elements are replaced constantly erythrocyte production erythrocytes -- (3 to 4 months) pluripotent stem cells in bone marrow mainly flat bones also blood stream negative-feedback mechanism kidneys - erythropoietin cycle takes about 3 weeks Pluripotent stem cells Lymphoid stem cells Myeloid stem cells basophils erythrocytes B cells T cells eosinophils platelets Lymphocytes Cardiovascular diseases >50% the deaths in the U.S. heart attack stroke ischemic embolus hemorrhagic stroke neutrophils monocytes