1. Pulmonary Circulation- THIS IS A REVIEW!!!! ______________ blood enters the lungs from ______ ventricle of heart through the pulmonary ______. Pulmonary trunk splits into left and right pulmonary arteries that enter the two lungs Pulmonary arterioles enter capillary networks around the alveoli Oxygenated blood returns to the left atrium in the pulmonary veins.

2. Thoracic Cavity Bound by __________ vertebrae dorsally, ______ & _____________ muscles laterally, the __________ ventrally, and the _____________caudally. Mediastinum – area between lungs REVIEW!!! Contains heart, trachea, esophagus, blood vessels, nerves, lymphatic structures, thymus

3. Pleura- REVIEW!!! Serous membrane that lines thoracic cavity and covers organs and structures in thorax __________ layer covers thoracic organs and structures __________ layer lines the cavity Space between the two pleural layers is filled with a small amount of pleural _________ (same in abdomen, pericardium) Helps ensure that surfaces of organs slide smoothly along lining of thorax during breathing (_______________)

4. Diaphragm Thin, dome-shaped sheet of skeletal muscle Forms caudal boundary of thorax Base of lungs lie directly on the cranial surface and the liver lies on the caudal surface Important respiratory muscle Dome-shaped when ___________ Flattens when it __________ Enlarges volume of thorax and aids inspiration

5. Process of Respiration Requires effective movement of air into and out of lungs at an appropriate rate and in sufficient volume to meet the body’s needs at any particular time. Pressure within the thorax is ____________ with respect to atmospheric pressure. Pulls lungs tight against the thoracic wall Flexible nature of lungs allows them to conform with shape of the thoracic wall. Pleural fluid provides __________. Lungs follow movements of thoracic wall Negative intrathoracic pressure helps draw blood through ________ in the mediastinum and into atria

6. Pneumothorax Leakage of air into thorax → Loss of negative pressure in lungs (causes “collapsed lung”) Causes: Penetrating wound of chest Rupture of alveoli Rx Remedy cause Remove air from thorax Needle/syringe (aka ____________________) Chest tube

7. Inspiration Process of drawing air into lungs (inhalation) Results from increasing volume of thoracic cavity by inspiratory muscles Main inspiratory muscles: ___________ and ____________ intercostal muscles External intercostals located in external portion of intercostal spaces (between ribs) Diaphragm enlarges the thoracic cavity by flattening out.

8. Expiration Process of pushing air out of lungs (exhalation) Results from decrease in size of thoracic cavity Main expiratory muscles: ___________ intercostal muscles and ____________ muscles Internal intercostal muscles located between the ribs, deep to the external intercostal muscles Contraction of abdominal muscles pushes abdominal organs against the diaphragm and pushes diaphragm back into its full dome shape.

9. Respiratory Volumes ___________ volume – volume of air inspired and expired during one breath. Varies according to body’s needs. Smaller when animal is at rest and larger when excited and active. __________ volume – volume of air inspired and expired during one minute. Calculated by multiplying the tidal volume by breaths per minute. Measured in mL or Liters __________ volume – volume of air remaining in the lungs after maximum expiration. Residual volume always remains, lungs will never be completely emptied of air.

10. Alveolar Gas Exchange- REVIEW!! Simple _________ of gas molecules from areas of _____ concentration to areas of _____ concentration. _____ diffuses from the alveolar air into the blood of the alveolar capillary _____diffuses from the blood into the alveolus

11. Respiratory Center Even though all of the inspiratory and expiratory muscles are skeletal muscles under voluntary control, breathing does not require a conscious effort. Breathing is controlled by an area in the _________ ___________ of the brain stem known as the Respiratory Center. Directs timing and strength of contraction Can be consciously controlled for brief periods.

12. Mechanical Control System __________ receptors in the lungs set limits on routine resting inspiration and expiration. Respiratory center sends out nerve impulses when lungs inflate to a certain point Stops muscle contractions that produce inspiration and starts contractions to produce expiration Another set of nerve impulses sent when lungs deflate sufficiently Stops expiration and starts the process of inspiration again

13. Chemical Control System Adjusts normal rhythmic breathing pattern produced by mechanical control system Chemical (peripheral) receptors in carotid artery and aorta monitor blood _____, ____, and ____. Central chemical receptors are located in the medulla oblongata.

14. Chemical Control System Blood level of CO 2 and blood pH linked __CO 2 in blood and __blood pH triggers respiratory center to increase rate and depth of respiration __CO 2 in blood and __blood pH triggers respiratory center to decrease rate and depth of respiration

15. Chemical Control System _______ - decrease in blood O 2 level Slight hypoxia triggers respiratory center to increase the rate and depth of breathing Severe hypoxia - neurons of the respiratory center can become so depressed that adequate nerve impulses cannot be sent to the respiratory muscles Can cause breathing to decrease or stop completely