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Biological Sciences
Stephen Reid

Lecture 9 Study Notes Lungs are lobular o Left lung: has 2 lobes and greater capacity. The cardiac notch is the space present to accommodate the heart o Right lung: has 3 lobes but lesser capacity due to the position of the liver below it. However, it is wider than the left lung As you move down the respiratory tract, the amount of cartilage decreases, but the amount of smooth muscle increases Conducting zone: anatomical dead space bn larynx and terminal bronchioles that is not involved in gas exchange. o too thick for gas exchange o warms and humidifies air Respiratory zone: thin-walled simple squamous epithelium (alveoli) that allows gas exchange with blood Smallest blood vessels are capillaries There are 4 different muscles involved in respiration 1. Diaphragm: separates thoracic cavity from abdominal cavity. Shaped like a parachute 2. Internal intercostal muscles: lie closer to the sternum 3. External intercostal muscles: on the outside 4. Abdominal muscles Diaphragm innervated by phrenic nerve. o Phrenic nerve omes off 4 cervical vertebrae. o Comes off so high so that if spinal injury occurs, lung is still functional. If came off lower closer to diaphragm, spinal injury would make someone unable to breathe. o Phrenic nerve takes commands from brain stem
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