nares. Horses can dilate a LOT, pigs can't. Plays a role in oxygen intake during exercise.
2nd part of respiratory system (after nares)
paired nasal cavity containing turbinates (thin scrolls of bone covered in mucus membranes)
Warm and moisten air, cool blood going to brain, allowing the brain temperature to be 2-3 degrees lower than the body temp.
Anatomy of trachea and principle bronchi
dorsally incomplete rings of cartilage united by annular ligament. Trachealis muscle completes the ring. Lined with pseudostratified ciliated columnar epithelium to prevent particles from getting into lungs. Beat stuff upward where it can be swallowed.
holds tracheal cartilage rings together to form a tube
completes the incomplete "C" of the cartilage ring.
terminal bronchioles that contain alveoli
site of gas exchange in lungs. Contains alveolar duct, alveolus and alveolar sac. Lays against capillary endothelium
Pleura of lung
Parietal pleura lines thoracic cavity.
Pleural cavity contains a little fluid to help pleura move against each other during respiration
Visceral pleura lines outside of lungs.
Pressure inside the pleural space is
midsite where 2 pleura meet. Separates the lungs and contains the heart and major vessels
Blood supplies to the lungs
2 kinds: Pulmonary arteries oxygenate blood then supply it to the rest of the body. (ventilation perfusion coupling)
Bronchial arteries arise from the aorta and deliver to the lungs.
Vasoconstriction upon hypoxia. Different from rest of the body. If there is no oxygen in an area, doesn't allow blood to go there.
the pressure within the lungs
the pressure outside the lungs but within the the thoracic cavity (between the visceral and parietal pleura)
inverse relationship between volume and pressure.
the pressure inside the lung decreases as the volume of the lung increases
volume up, pressure down. Pressure down, air in.
muscular enlargement of the thorax and lungs with accompanying inflow of air.
Usually an active process.
Diaphragm contracts down, external intercostals contract, increases volume of thorax, pressure inside lungs decreases, 25% of air rushes in.
Why can lungs increase in volume?
Intrapleural pressure reduces as intrapulmonic pressure reduces.
Energy causing air to leave the lungs is provided by stored elastic energy in the stretched lung and thorax. Usually a passive process using the pressure gradient
In what animal is expiration an active process?
Horses, even at rest.
Any animal, if something is impeding outflow of air or breathing is accelerated. There is always a voluntary component.
To permit air to flow out of the lungs:
intrapulmonic pressure must be positive. Can be due to recoil tendency of lungs.
Can be produced by elastic fibers within lung or surface tension of fluid that lines alveolar.
Abdominal and internal intercostals
Diaphragm relaxes, abdominal muscles contract, internal intercostals contract, increases abdominal pressure, decreases size of thorax, forces diaphragm forward, reduces size of thorax, thoracic pressure increases, air is forced out.
Reduced total pressure of the intrapleural space is a slight vacuum.
during breathing the intrapleural pressure gets more negative then eases. Never positive.
goes from negative to more negative to positive to less positive (sin wave)
produced by elastic fibers within the lung and the surface tension of the fluid that lines the alveolar.
Factors that prevent recoil
Pleural pressure is lower than alveolar pressure to prevent collapse. Air cannot flow into the pleural space, trying exerts a force against the walls of the alveoli, counteracting the tendency of recoil
Surfactant keeps alveolar from contracting and collapsing, increasing compliancy of lung.
water lines surface of alveoli and tries to h-bond with other water. This makes alveoli recoil and collapse. Surfactant is produced by typeII alveolar cells, stops H-bonds in water, lowers surface tension, prevents collapse.
Increases compliancy making ventilation more efficient.
Premature birth and ventilation
surfactant is one of the last things to develop. Premature infants often don't have it. Can't inflate lungs. Treated with synthetic surfactant.
entry of air into the pleural cavity in sufficient quantity to cause collapse of the lung and consequent respiratory embarrasment.