11.4.13 kin 272 class notes- Alveolio Alveoli sacso Simple squamos epitheliumo Type I- basic cellso Type II – surfactant Changes surface tension Alveoli stay openo Structure: Capillary network bed Turns in veinule network Surrounding each sack are its own capillaries Millions of alveoli sacs Capillaries Adhere around alveolar sacs elastic fibers – mesh network of elastic (rubberbands)- tightly hold capillaries on alveolar sacs all of the pieces make up the perichyma- all of the connective, elastic tissue, capillaries, outside ofalveoli holding a lung - take a good size sponge the size of watermelon and fill with water- fairly heavy- capillaries are heavy- surfactant, watery medium=heavyo Compliance Idea that when you fill up a balloon, you need to work to fill it up. When you remove your mouth, it deflates Lungs work the same way as a balloon Need to work to inflate, no work to exhale Exhaling is passive Lung tissues comply well Deteriorate elastic fibers/no surfactant, lose compliance Fill up lungs- stay full. To move out, you need to work to exhale. Somebody with COPD/emphysema- Difficult to breathe- It is good to have capillaries snug onto sacs for better diffusion yayo Decrease diffusible distanceo Increase diffusible rate- Ventilationo Definition: exhale & inhale- Respirationo Definition: gas exchangeo Internal & externalo Internal – o External – alveoli and capillaries- O2 consumptiono Definition: how much oxygen is being used in ETC and mitochondriao No oxygen to consume if you didn’t respirateo No respiration without ventilation- Ventilation:o Inhale/inspire:o Exhale/expire:o Boyle’s Law Pressure = 1/volume Pressure and volume are inversely relatedo In order to breathe we need changes in pressure (we can only change volume) We change volume in order to change pressure- Thoracic cavity & abdominal cavity are divided by diaphragm- Diaphragmo Decides what the volume in thoracic cavity iso We can’t change pressureo Trick to inflating lungs: Pressure is greater on one side than the other High pressure low pressure Air moveso Nerve tells diaphragm to contract Pulls down on membrane surrounding the lungs- Pleura- Acts like a vacuum seal- When diaphragm contracts & flattens out, pulls down pleura, increases volume in thoracic cavity- Pressure decreases!- Air goes into the lungs- Not changing pressure directly… This is the process of inhaling! active process- Contract diaphragm- Exhaling passive processo Healthy resting expend no energyo To exhale you need to relax the diaphragmo Decreases the volume, increases the pressure, air moves outo Compliance Elastic fibers retract slightly and force air out Relaxation of diaphragm also forces air out Very passive- 75% of work done from diaphragmo unless sick…- if you need to forcefully inhaleo you use other muscleso accessory inhaliation muscleso external intercostals help to elevate the ribs change volume of thoracic cavityo sternocleidomastoido serratus anterioro pectoralis minoro scalenes- exhalingo accessory: abdominal muscles (internal & external obliques), rectus abdominus, transverse abdominus, internal intercostals, THAT’S ITo forcable exhaling- compress abdominal contents to force diaphragm
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