Chapter 42 Respiratory Systems

Qualifying Respiration Gas Exchange Cellular Respiration Organismal level O 2 in CO 2 out via diffusion Cellular level Use O 2 and produce CO 2 and ATP

Respiratory Medium Water Membranes always moist Air High concentration of oxygen Less dense O 2 and CO 2 diffuse faster in air than water

Respiratory Surface Requirements Thin Diffusion distance Moist PM stability Large SA to volume ratio Fick’s Law R = D x A ( p/d)

Altitudes and Oxygen Air is a fixed ratio of gases Each contributes a partial pressure to the atmosphere P N 2, P O 2, P CO 2, and other gases Air thins with increasing altitude Gas in same ratio, but less of

‘Skin Breathers’ Earthworms and some amphibians Skin is respiratory surface Moist environments

Gill Systems Extensions of body surface (pink) Ventilation adaptations varies organization Movement of water across gills Inefficient of land Desiccation Tissue mass

Countercurrent Exchange Exchange between two opposite flowing fluids Maximum efficiency Concentration gradient favors O 2 diffusion from H 2 O Always slightly more in blood Compare with concurrent

Tracheal System Most terrestrial animals (insects) Internal branched tubes Connect all cells to environment Close to retain moisture Open circulatory system role? Body movements in larger and more active species

Lungs Internal sacs with moist epithelium Extensive inner branching Closed circulatory system role? Book lungs in spiders (open) Most terrestrial vertebrates Variations between phyla

Terrestrial Vertebrates Amphibians Obtain O 2 via positive pressure Skin for exchange Birds 1 way flow 2 cycles to complete Mammals Negative pressure Incomplete removal each cycle Myoglobin varies with environment

Mammalian Respiratory System

Respiratory Cycle Boyle’s Law: increased volume, decreases thoracic pressure

Control of Human Breathing Medulla establishes rhythm Pons sets rate Most is involuntary Holding breath Sensors in carotid arteries and aorta pH of CSF reflects [CO 2 ] in blood Must correlate with circulation Exercise or baby’s first breath

Gas Exchange P O 2 and P CO 2 vary within the circulatory system Pressure gradient facilitates gas exchange in tissue capillaries Lungs: O 2 into blood, CO 2 into alveoli Body tissues: O 2 out of blood, CO 2 in

Respiratory Pigments Protein bound to a metal Hemoglobin increases O 2 carrying capacity Increase P O 2 increase Increase P CO 2 increase dissociation = H + binding to buffer blood pH increase Temperature decrease

Respiratory Problems Alveoli of ciliated epithelium Traps contaminants Swept out in mucus Alveoli highly susceptible to contaminants Macrophages patrol COPD, pnemonia, Black lung Surfactants keep alveoli open Fetal development at 33 weeks