okay so we were on this slide lungs the right lung the left lung the right lung has three lobe and the left lung has the two loop then these loops are further subdivided into segment the right lung has 9 to 10 segment and the left lung has about 8 segment if one segment is diseased it can be individually removed for example in case of cancer if one segment is affected it can be removed so here is the lung the pointed tip is the epics this is the base which sits on the diaphragm this part indentation here is hyaluron so through the hilum a pulmonary vein will exit pulmonary artery will enter bronchus will enter so highland is the point of entry for the blood vessels and point of exit for the blood vessel as well as lymphatic capillaries also enter and exit at high level blood supply pulmonary circulation so pulmonary trunk takes deoxygenated or oxygen poor blood from the right ventricle to the lungs pulmonary veins bring oxidated or oxygen rich blood from the lungs back to the left atrium that is pulmonary circulation then bro blood supply to the lungs bronchial arteries they arise from the descending iota and enter the lungs at harlem bronchial arteries supply oxygenated blood to the lung bronchial way joined with pulmonary veins pleura so pura is the double serus membrane parietal pleura lines the inner surface of the thoracic cavity visceral pleura attaches directly on the surface of the lung so visceral pleura on the external surface of the lung it clings to it between the parietal pleura and visceral pleura there is a space like slit like opening space that space is known as plural cavity and plural cavity contains plural flute respiratory physiology pulmonary ventilation inhalation when we breathe in exhalation as we breathe out volume changes in the thoracic cavity lee lead to pressure changes and pressure changes lead to flow of gases so we inhale we exhale and that occurs because of volume and pressure changes in the thoracic cavity air always moves from high pressure towards low pressure so pressure relationship in the thoracic atmospheric pressure atmospheric pressure is pressure exerted by air so air surrounds us and air has a atmospheric pressure of 760 millimeter mercury at the sea level it is also considered one atmospheric pressure so air which is surrounding us respiratory pressure are described in relation to the atmospheric pressure negative respiratory pressure means the pressure which is lower than atmospheric pressure is described as negative respiratory pressure positive respiratory pressure is the pressure which is above atmospheric pressure is described as positive respiratory pressure and zero respiratory pressure when the atmospheric pressure and the intrapulmonary pressure they are equal it is described as zero millimeter mercury so we see here here is the thoracic cavity and here is the parietal pleura here is the visceral pleura between the parietal and visceral pleura this is the pleural cavity which is filled with the plural fluid so intrapulmonary pressure is the pressure in the alveoli in the lungs actually and intrapulmonary pressure fluctuates with breathing and eventually it equalizes with the atmospheric pressure so intra pulmonary pressure is here pressure in the lbo line zero millimeter mercury means it is same 760 millimeter mercury in relation to atmospheric pressure so we say 760 millimeter mercury or we say zero millimeter mercury as they equalize intrapleural pressure intrapleural pressure is here in the pleural cavity the pressure within the pleural cavity also fluctuates with bleeding always negative pressure means it is four millimeter less than the atmospheric pressure so it is 757 56 millimeter mercury or we say negative four millimeter mercury it is four millimeter less than the atmospheric pressure usually always four millimeter less than intra pulmonary pressure also fluid level in the pleural cavity must be minimal because if the fluid will accumulate in the pleural cavity it will like the pressure in the plural cavity will increase it will move towards the positive in trouble like it is negated and but if the fluid will accumulate it will put the pressure on the lungs and the lungs will collapse if intrapleural pressure is equal to intrapulmonary pressure or atmospheric pressure the lungs will collapse and that is the reason intrapleural pressure needs to be negative four millimeter mercury transpulmonary pressure is the intrapulmonary pressure minus intra pleural pressure is transpulmonary pressure and the higher the trans pulmonary pressure the larger the lungs are so see here the transpulmonary pressure intra pulmonary pressure minus intra plural pressure is considered trans pulmonary pressure atlaxis is lung collapse and that can occur due to two reasons if the bronchioles are blood they are blocked for example someone is suffering from pneumonia severe pneumonia that will cause plant blood bronco or lung collapse can also occur due to pneumothorax pneumothorax is a condition when there is air in the pleural cavity how the air enters into the plural cavity it can occur from either the wound in the parietal pleura or the rupturing of the visceral pleura and it is treated by removing air with chest tubes so we see here rupturing either the parietal pleura or rupturing the visceral pleura in that case air enters into the pleural cavity air in plural cavity causes intra pleural pressure to become equal to intrapulmonary pressure that causes the lungs to collapse so this is important to know what happens during pneumothorax we have air in the pleural cavity and it causes intrapleural pressure and the intrapulmonary pressure to be equal and that causes lungs to collapse actually so know that now pulmonary ventilation pulmonary ventilation inspiration means inhalation and exhalation it's a mechanical process and it occurs because of volume changes volume changes and pressure changes in the thoracic cavity boy's law boy is the knee boys like a boil is the name of the scientist and boy's law states the relationship between the pressure and the volume pressure is inversely proportional to the volume what does it mean as volume increases pressure decreases as volume decreases pressure increases think about we have the same amount of air and we place that air into a small box and then we place that air into a larger box larger box has more volume so same amount of air in the larger volume will volume increases pressure decreases volume decreases pressure increases so understand boyle's law now inspiration is an active process so what happens inspiratory muscles contract diaphragm which is dome shape it contracts and it becomes flat the external intercostal muscles contract and they pull the ribcage up actually so the volume of the thoracic cavity increases as the volume of thoracic cavity increases intrapulmonary pressure drops air flows into the lungs because air flows from high pressure to low pressure as the volume of the thoracic cavity increases because diaphragm contracts and the external intercostal muscles contract the pressure inside the lung a drops to 7 59 millimeter mercury one millimeter less than the atmospheric pressure air flows in so forced inspiration using accessory muscles to further increase the size of thoracic cage and it occurs during the vigorous exercise or during coronary obstructive pulmonary disease so here we see inspiratory muscles contract diaphragm goes down the ribcage rises volume of the thoracic cavity increases lungs are stretched intrapulmonary volume increases intrapulmonary pressure drops by one millimeter mercury so air flows into the lung from high pressure to low pressure air flows into the lungs down its pressure gradient until intrapulmonary pressure is equal to atmospheric pressure so go through this slide now expiration is a passive process inspiratory muscles relax and thoracic cavity volume decreases so the pressure increases so see here inspiratory muscles relax means diaphragm becomes dome-shaped ribcage also goes down thoracic cavity volume decreases as the volume decreases pressure increases elastic lungs recoil intrapulmonary volume decreases and intrapulmonary pressure rises by 1 millimeter mercury air flows out of the lungs due to the pressure gradient until intrapulmonary pressure is zero so it's important to go through these slides of inspiration and expired