Exam 2.0 Cheat Sheet (DRAFT) by jjovann

•There are 5 main types of blood vessels
–Arteries
–Arter­ioles
–Capil­laries
–Venules
–Veins

–Veins
– carry blood towardsthe heart

•Arter­ioles
–Regulate blood flow to the capill­aries
–They are the primary "­adj­ustable nozzles” across which the greatest drop in pressure occurs.

•Capil­laries empty into venules.
•The venules empty into veins
–Because intrav­enous pressure is so low, veins have valves to keep blood flowing in only 1 direction.
•When exposed to higher than normal pressures, the valves in veins can become incomp­etent allowing blood to pool (varicose veins).

•True capill­aries
–10 to 100 exchange vessels per capillary bed
–Branch off metart­eriole or terminal arteriole

•Diffusion
•The movement of a substance from an area of high concen­tration to an area of low concen­tration
•In all capill­aries, excluding the brain, diffusion is the most important means in net solute exchange between the plasma and inters­titial fluid

–Filtr­ation
•the movement of fluid (plasma) through the walls of the capillary and into the inters­titial fluid.
•Two pressures promote filtra­tion:
–Blood hydros­tatic pressure (BHP) generated by the pumping action of the heart
–Inter­stitial fluid osmotic pressure (IFOP) is due to the presence of dissolved solutes in the inters­titial fluid

–Gases and these other substances simply move into or out of the capillary down their concen­tration gradient.

–Oppos­ition to flow
–Measure of amount of friction blood encounters with vessel walls, generally in peripheral (systemic) circul­ation
–Three important sources of resistance
•Blood viscosity
•Total blood vessel length
•Blood vessel diameter

•The "­sti­cki­nes­s" of blood due to formed elements and plasma proteins
•Increased viscosity = increased resistance

–Also called Total Peripheral Resistance (TPR)
–All the vascular resist­ances offered by the systemic blood vessels
–Also called Total Peripheral Resistance (TPR)
–A major function of arterioles is the control of SVR
–Pathos is athero­scl­erosis

•Systolic pressure: highest pressure obtained in arteries during ventri­cular ejection
•Diastolic pressure: lowest level of pressure obtained in the arteries during ventri­cular diastole
•Pulse pressure = difference between systolic and diastolic pressure
•Mean arterial pressure (MAP): pressure that propels blood to tissues

•Control is accomp­lished through several negative feedback systems
–BP controlled by adjusting HR, SV, TPR, and blood volume
–Some systems are rapid for quick adjustment
•Count­eract fluctu­ations in blood pressure by altering peripheral resistance and CO
•E.g. – keeps you from passing out from the drop in blood pressure in the brain when you get out of bed
–Others systems act more slowly
•Count­eracts fluctu­ations in blood pressure by altering blood volume­•These provide long-term regulation
–The body may also require adjust­ments in distri­bution of flow
•E.g. – when you exercise, a greater percentage of total flow is diverted to skeletal muscle

•Nervous system regulates blood pressure using negative feedback loops that occur as 2 types of reflexes
–Baror­eceptor reflex
–Chemo­rec­eptor reflex

•Regul­ation of blood pressure and flow is also under the control of several hormones.
–Renin­-an­gio­ten­sin­-al­dos­terone (RAA) system
–Epine­phrine and norepi­nep­hrine
–Antid­iuretic hormone
–Atrial Naturetic Peptide

–released from the posterior pituitary gland in response to dehydr­ation or decreased blood volume.
–Increases water reabso­rption in the kidneys which increases blood volume
–Potent vasoco­nst­rictor

•Vasod­ilation of arterioles and relaxation of precap­illary sphincters occur in response to local chemical changes
–Declining tissue O2
–Subst­ances from metabo­lically active tissues (H+, K+, adenosine, and prosta­gla­ndins) and inflam­matory chemicals

–defined as elevated systolic blood pressure (SBP), an elevated diastolic blood pressure (DBP), or both.
–Diastolic pressure is greater than 100
–Systolic pressure is greater than 160
–Depending on severity, it is classified as pre-hy­per­ten­sion, Stage 1 HTN, or stage 2 HTN

•Heart rate & force increase
•Vasoc­ons­tri­ction or vasodi­lation depending on the type of shock
•ADH released to conserve water
•Renin releases Angiot­ensin II
•Aldos­terone released to conserve Na+
•ANP inhibited

•Air passing through the respir­atory tract traverses the:
–Nasal cavity
–Pharynx
–Larynx
–Trachea
–Primary (1o) bronchi
–Secondary (2o) bronchi
–Tertiary (3o) bronchi
–Bronc­hioles
–Alveoli (150 millio­n/lung)

•scrol­l-s­haped bony elements forming the upper chambers of the nasal cavities
–Tucked under each nasal concha is an opening, or meatus
–Receptors in the olfactory epithelium (used for smell)­pierce the bone of the cribriform plate.

•The pharynx has 3 anatomical regions:
–Nasop­harynx
–Oroph­arynx
–Laryn­gop­harynx

•The laryng­oph­arynx lies inferiorly and opens into the larynx (voice box) and the esophagus.
–It partic­ipates in both respir­atory and digestive functions.

–a flap of elastic cartilage covered with a mucous membrane
–The epiglottis guards the entrance of the glottis, the opening between the vocal folds
•For breathing, it is held anteri­orly, then pulled back-ward to close off the glottic opening during swallowing

•The purpose of the semi-rigid cartilage rings in the respir­atory tract is to prevent airway collapse during inhalation
•The tracheal cartilage rings are incomplete poster­iorly, facing the esophagus.
–This allows the esophagus to expand as it moves the bolus of swallowed food toward the stomach
–Esoph­ageal masses can press into this soft part of the trachea and make it difficult to breathe, or even totally obstruct the airway.

•The bronchi and bronch­ioles go through structural changes as they continue to branch and become smaller.
–The mucous membrane changes cell type and then disapp­ears.
–The cartil­aginous rings become more sparse, and eventu­ally, disappear altoge­ther.
–As the amount of cartilage rings decrease, smooth muscle conten­t(under the control of the Autonomic Nervous System) increase.

Earths atmosphere is mainly composed of these gases:
–Nitrogen (N2) 78%
–Oxygen (O2) 21%
–Carbon Dioxide (CO2) 0.04%
–Water Vaporv­ari­able, but on average around 1%

–Negative respir­atory pressure = less than Patm
–Positive respir­atory pressure = greater than Patm
–Zero respir­atory pressure = Patm

–Just before each inhala­tion, the pressure inside the lungs is equal to the atmosp­heric pressure.
•760mmHg
–Air flows from high pressure to low pressure
–For air to flow into the lungs, the pressure in the alveoli must be less than atmosp­heric
–This decrease in alveoli pressure is accomp­lished by increasing the volume of the lungs through mechanical coupling to a change in thoracic volume

–Advanced pregnancy, excessive obesity, and confining abdominal clothing can obstruct diaphragm flattening

•The pressure in the lungs is greater than that of the atmosphere

- air, or liquid (blood or Inters­titial fluid), in the pleural cavity
–From either wound in parietal or rupture of visceral pleura
–Intra­pleural pressure goes from -4 to 0 thus elimin­ating the transp­ulm­onary pressure that keeps a lung open
•lung collapses in on itself

•The surface tension of alveolar fluid
–Found at all air-water interfaces
•Polar water molecules are more strongly attracted to each other than gas in air
•This means that when air tries to fill the alveoli, the water on the alveoli surface doesn’t want to pull away from itself and produces an inward pull resisting expansion

•Defic­iency of surfactant in premature infants
•Alveoli collapse due to high surface tension
•Treated by using continuous positive air pressure (CPAP) breathing machines - increases pressure of air going into the lungs - and synthetic surfactant until infant begins producing its own

•Just like blood flow through the circul­atory system, air flow depends upon pressure difference and resistance
•The diameter of airways is regulated by smooth muscle tone which, as previously discussed, is dependent upon parasy­mpa­thetic and sympat­hetic intera­ction

•Obstr­uctive disorders
–Any pathol­ogical condition that narrows, or obstructs, airways
•Narrowing of airways greatly increases resistance for inhalation and exhalation
–Increased work of breathing
•Airways can also become blocked via the collapse of bronch­ioles, alveoli, or build-up of excess mucous
•Types of obstru­ctive lung disease include;
–asthma, bronch­itis, chronic obstru­ctive pulmonary disease (COPD), emphysema, cystic fibrosis, etc.

–Arteries – carry blood away from the heart
•Large elastic arteries (>1 cm);
medium muscular arteries (0.1 – 10 mm);
arterioles (< 0.1 mm)

Systemic veins and venules have the most percentage of the blood found

•The largest arteries are the conducting arteries (elastic arteries)
–Elastic arteries perform the important function of storing mechanical energy during ventri­cular systole and then transm­itting that energy to keep blood moving after the aortic and pulmonary valves close.
–Best exempl­ified by the garden hose-sized aorta.

•Capil­laries are the only sites in the entire vascul­ature where gases, water, nutrients, and wastes are exchanged with the inters­titial fluid that bathes tissue.
• They have no tunics
•The minimalist nature of capill­aries allows them to be freely permeable to many substances (gases, fluids, and small ionic molecu­les).

•An anasto­mosis is a union of vessels supplying blood to the same body tissue.
–Should a blood vessel become occluded, a vascular anasto­mosis provides an altern­ative route for blood to reach to and return from tissue
–A great example is the genicular anasto­mosis
•Common at joints, in abdominal organs, brain, and heart
•None in retina, kidneys, spleen

•Preca­pillary sphincters are bands of smooth muscle that regulate blood flow into true capill­aries
–Blood can go into true capill­aries or to shunt depending on contra­ctile state of precap sphincters
•Flow through capill­aries regulated by local chemical conditions and vasomotor nerves
•Slow capillary blood flow allows adequate time for exchange between blood and tissues

•Trans­cytosis
–Movement of a small quantity of material through the endoth­elial cell using a pinocytic vesicle
•Small membrane enclosed bubble transp­orting substance within cell
–Used mainly for large lipid-­ins­oluble (water­-so­luble) molecules that cannot cross capillary walls by other means
•Insulin enters the blood stream this way

Two factors remain relatively constant:
–Blood viscosity
–Blood vessel length

–Reabs­orption
•the movement of fluid from the inters­titial fluid back through the walls of the capillary and into the plasma.
•Two pressures promote reabso­rption:
–Blood colloid osmotic (or oncotic) pressure (BCOP)
•due to the presence of plasma proteins too large to cross the capillary wall
–Inter­stitial fluid hydros­tatic pressure (IFHP)
•The fluid pressure of the inters­titial fluid

•Blood flow (F) is directly propor­tional to blood pressure gradient
–If one decreases, the other decreases
•Blood flow inversely propor­tional to resistance (R)
–If one decreases, the other increases and vice versa
• (resis­tance) more important in influe­ncing local blood flow because easily changed by altering a tissue’s blood vessel diameter

•Systemic pressure
–Highest in aorta
–Declines throughout the pathway

•Ranges from 35 (capillary entry)to 16 mmHg (capillary exit)
•Low capillary pressure is desirable
–High BP would rupture fragile, thin-w­alled capill­aries

•In an effort to meet physio­logical demands, we can increase blood flow by:
–Incre­asing BP gradient
•Bigger difference between high and low pressure creates greater blood flow
–Decre­asing systemic vascular resistance in the blood vessels
•Makes it easier for blood to flow from high to low

•Speed of blood flow
–Usually in cm/sec
–Velocity of blood flow is inversely propor­tional to total cross-­sec­tional area of vessel lumens

•Regul­ation of BP can occur by various methods
–Neural control
–Hormonal control
–Autor­egu­lation

–Pressure sensitive sensory receptors
–Found in the aorta, carotid arteries, and other large arteries in the neck and chest
–Changes in pressure cause changes in the rate of impulses (action potent­ials) sent to the brain
•Decrease in pressure = decrease in impulse rate
•Increase in pressure = increase in impulse rate
–2 most important barore­ceptor reflexes
•Carotid sinus reflex
–Helps regulate blood pressure in the brain
•Aortic reflex
–Regulates systemic blood pressure

•The Renin-­ang­iot­ens­in-­ald­ost­erone (RAA) system is an important endocrine component of autore­gul­ation.
–Renin is released by kidneys when blood volume falls, Na deficiency is detected, or renal blood flow decreases.
•It causes the conversion of precursors into substances that lead to the production of the active hormone angiot­ensin II, which raises BP by vasoco­nst­riction and by stimul­ating secretion of aldost­erone from the adrenal glands.

–a diuretic polype­ptide hormone released by cells of the cardiac atria in response to high blood volume and atrial pressure.
–ANP partic­ipates in regulation by:
•Lowering blood pressure (it causes direct vasodi­lation)
•Reducing blood volume by increasing sodium excretion in the kidneys (promoting loss of salt in urine formation decreases water reabso­rption by the kidney

•Effects
–Relax­ation of vascular smooth muscle
–Release of Nitric Oxide (powerful vasodi­lator) by endoth­elial cells
•Endot­helins released from endoth­elium are potent vasoco­nst­rictors
•NO and endoth­elins balanced unless blood flow inadeq­uate, then NO wins
•Infla­mmatory chemicals cause vasodi­lation, also

•In an autore­gul­atory response, important differ­ences exist between the pulmonary and systemic circul­ations:
–Systemic blood vessel walls dilate in response to hypoxia (low O2) or acidosis to increase blood flow.
–The walls of the pulmonary blood vessels constrict to a hypoxic or acidosis stimulus to ensure that most blood flow is diverted to better­-ve­nti­lated areas of the lung.

–defined as any blood pressure too low to allow sufficient blood flow (hypo-­per­fusion) to meet the body's metabolic demands (to maintain homeos­tasis)
–Hypot­ension leading to hypo-p­erf­usion (pressure and flow are related) of critical organs results in shock

•Most cases of severe shock call for the admini­str­ation of extra fluids and emergency medica­tions like epinep­hrine to help restore perfusion (blood flow)to the tissues.
• If a balance is not restored organs will fail (kidney failure, liver failure, coma) and damage may become permanent.

•Struc­tur­ally, The respir­atory system is divided into upper and lower divisi­ons,or tracts.
–Upper respir­atory tract
•consists of the nose, pharynx and associated struct­ures.
–Lower respir­atory tract
•consists of the larynx, trachea, bronchi and lungs.

•Much, not all, of the respir­atory tract is covered with pseudo­str­atified ciliated columnar epithelium with inters­persed goblet cells (secrete mucous)
•Cilia in the upper respir­atory tract move secreted mucous with trapped particles down toward the pharynx.
•Cilia in the lower respir­atory tract move secreted mucous up toward the larynx.

•During inhala­tion, conchae and nasal mucosa
–Filter, heat, and moisten air
•During exhalation these structures
–Reclaim heat and moisture

•The nasoph­arynx lies behind the internal nares.
–It contains the openings of the Eustachian tubes (auditory tubes), which come off of it and travels to the middle ear cavity.

•As air passes from the laryng­oph­arynx into the larynx, it leaves the upper respir­atory tract and enters the lower respir­atory tract.

•formed by a pair of mucous membrane vocal folds
–The vocal folds are situated high in the larynx just below where the larynx and the esophagus split off from the pharynx

•The carina is an internal ridge located at the junction of the two mainstem bronchi
– a very sensitive area for triggering the cough reflex.

•Sympa­thetic stimul­ation causes airway dilation –> bigger airway = less airflow resistance
•Paras­ymp­athetic stimul­ation causes airway constr­iction –> smaller airway = more airflow resist­ance.

–3 basic steps
•Pulmonary ventil­ation
•External (pulmo­nary) respir­ation
•Internal (tissue) respir­ation

–The pressure we feel on the surface of the earth is, in essence, the weight of the gasses in our atmosphere
•At high altitudes, the atmosp­heric pressure is less; descending to sea level, atmosp­heric pressure is greater.

At sea level, the air pressure is:–760 mmHg = 1 atmosphere

–Pressure in alveoli
–Changes when breathing
–Always eventually equalizes with Patm

–Most important muscle for inspir­ation
–Dome-­shaped skeletal muscle innervated by the phrenic nerve
–Contr­action of the diaphragm causes it to flatten
•Lowers (flattens) the dome
•This increases the vertical volume of the thoracic cavity
•The change in volume is transf­erred to the lungs via the intrap­leural cavity and the pressure within it

–Second most important muscles of inhalation
–During contra­ction, these muscles elevate the ribs increasing the antero­pos­terior and lateral diameters of the chest cavity
•During inhala­tion, the ribs move upward and outward like the handle on a bucket

•Normal exhalation during quiet breathing
•Called passive because no muscular contra­ctions are involved
•Instead, it results from inward forces;
–The elastic recoil of the chest wall and lungs
–the inward pull of the surface tension of the alveolar fluid

–At the same time, the chest wall moves outward because its elastic recoil is no longer opposed by coupling to the inward pulling forces of the lungs
–Treated by removing excess intrap­leural air/fluid with chest tubes; restores negative pressure  lung re-inf­lates
–Because the lungs are in separate pleural cavities, one may collapse without interf­ering with the function of the other

•Causes the alveoli to assume the smallest possible diameter
•Accounts for 2/3 of lung elastic recoil.
–If unopposed, this force would cause the alveoli would close with each expiration and make our “Work of Breathing” insupp­ortable

–How easily something stretches
•High pulmonary compliance means the lungs and chest wall are easily expanded – easier for inflation
•Low pulmonary compliance means they resist expansion – harder for inflation
–Lung compliance dependent upon 2 factors
•Elast­icity
•Surface tension

–The same as in blood vessel diameter, the larger the diameter of an airway, the less the airway resistance and the greater the flow
–If the bronch­ioles dilate even a little, the resistance drops by a power of 4

Capill­aries – site of nutrient and gas exchange

•The wall of a blood vessel consists of basic layers or “tunics”:
•Tunica interna (intima)
•Tunica media
•Tunica externa

•Medium sized muscular (distr­ibu­ting) arteries
–Muscular arteries help maintain the proper vascular tone to ensure efficient blood flow to the distal tissue beds by constr­icting and dilating.
–Some examples include the brachial artery in the arm and radial artery in the forearm.

•The body contains three types of capill­aries:
–Conti­nuous capill­aries
•The most common­•En­dot­helial cells form a continuous tube, interr­upted only by small interc­ellular clefts.
–Fenes­trated capill­aries (fenestra = windows)
•Found in the kidneys, villi of small intest­ines, and endocrine glands
•These are much more porous.
–Sinusoids
•Form very porous channels through which blood can percolate, e.g., in the liver and spleen.

•Vascular shunt (metar­ter­iol­e—t­hor­oug­hfare channel)
–Directly connects terminal arteriole and postca­pillary venule

•Capillary exchange
–The movement of substances between the blood and inters­titial fluid
–Subst­ances may pass using;
•Diffusion
•Trans­cytosis
•Bulk Flow (Filtr­ation and Reabso­rption)

•Bulk flow
–Passive process in which large numbers of ions, molecules, or particles in a fluid move together in the same direction with the fluid
–Movement is from an area of high pressure to one of low pressure
–Important for regulation of relative volumes of blood and inters­titial fluid
–hydro­static and osmotic forces determine bulk flow direction
–These are called Starling Forces

•Blood colloid osmotic pressure
–These create an osmotic pressure that pulls water into the capillary
•Inter­stitial fluid hydros­tatic pressure (IFHP)
–This is the water pressure of the inters­titial fluid that pushes fluid into the capillary
•Blood hydros­tatic pressure
-Basic­ally, the water pressure of the blood pushing fluid out
•Inter­stitial fluid osmotic pressure
-These solutes create an osmotic pressure that pulls water out of the capillary

•Blood flow
–Volume (amount) of blood flowing through vessel, organ, or entire circul­ation in a given period
•Measured as ml/min
•As a whole, relatively constant when at rest•A­mount varies widely through individual organs, based on needs
–Factors that affect blood flow
•Blood pressure
•Vascular resistance
•Venous return
•Velocity of blood flow

–Force per unit area exerted on the wall of the blood vessel by blood
•Expressed in mmHg
–Pressure gradient provides driving force that keeps blood moving from higher to lower pressure areas
–Deter­mined by CO, blood volume, and vascular resistance

–Const­antly monitored and easily­/qu­ickly adjusted
–Greatest influence on resistance
•Vasoc­ons­tri­ction
–Decrease vessel lumen diameter by contra­ction of smooth muscle
•Vasod­ila­tation
–Increase vessel lumen diameter by relaxation of smooth muscle
–Varies inversely with fourth power of vessel radius

•Pumping action of heart generates blood flow
•Resis­tance generates blood pressure

•Reflects two factors of arteries close to heart
–Elast­icity (compl­iance or disten­sib­ility)
–Volume of blood forced into them at any time
–Arterial pressure changes as they accomm­odate more or less blood from the upstream vessel

•The volume of blood returning through the veins to the right atrium must be the same amount of blood pumped into the arteries from the left ventricle
–Besides pressure, venous return is aided by the presence of venous valves, a skeletal muscle pump, and the respir­atory pump.
•The skeletal muscle pump –uses the action of muscles to squeeze blood in 1 direction (due to valves).
•The respir­atory pump
–uses the negative pressures in the thoracic and abdominal cavities generated during inspir­ation to pull venous blood towards the heart.

•CV center also has a role in regulation of blood vessel diameter
–Vasomotor center
•Vasoc­ons­trictor center
•Vasod­ilator center
•Sympa­thetic neurons that innervate blood vessels in the viscera and peripheral areas
–Vasomotor tone
–This sets the resting level for systemic vascular resistance

–Sensory receptors that monitor chemical changes in the blood
–Located close to the barore­ceptors of the carotid sinus and aortic bodies
–Detect changes in blood CO2, pH, and many detect O2 , also
•Hypoxia = low O2 availa­bility
•Acidosis = increase in H+ concen­tration above normal
•Hyper­capnia = excess CO2

–Released from the adrenal medulla as an endocrine response to sympat­hetic stimul­ation.
–They increase cardiac output by increasing heart rate and force of contra­ctions.
–Also have effects on blood vessels
•Vasoc­ons­tri­ctory (harder for to blood flow) in some places, vasodi­latory (easier for blood to flow) in others

–The ability of a tissue to automa­tically adjust its blood flow to match its metabolic demand
•Very important in heart, brain, and skeletal muscle
•Blood distri­bution to various parts of the brain changes
–Contr­olled intrin­sically by modifying the diameter of local arterioles feeding capill­aries
–2 general types of stimuli cause autore­gul­atory changes in blood flow•M­eta­bolic controls
•Myogenic controls
•Both determine the final autore­gul­atory response

•Myogenic responses keep local tissue perfusion constant despite most fluctu­ations in systemic pressure
•Vascular smooth muscle responds to stretch
–Passive stretch (increased intrav­ascular pressure) promotes increased tone and vasoco­nst­riction

•Occurs when short-term autore­gul­ation cannot meet tissue nutrient requir­ements
•Angio­genesis
–Growth of new blood vessels
–Number of vessels to nutrient deficient region increases and existing vessels enlarge to supply more blood flow in an effort to restore normal chemical enviro­nment
–Common in heart when coronary vessel occluded, or throughout body in people in high-a­ltitude areas

–Failure of the cardio­vas­cular system to deliver enough oxygen and nutrients to meet cellular metabolic demands
•The 4 basic types of shock are:
–Hypov­olemic shock
•due to decreased blood volume
–Cardi­ogenic shock
•due to poor heart function
–Obstr­uctive shock
•due to obstru­ction of blood flow - embolism
–Vascular shock
•due to excess vasodi­lation - as seen in cases of a massive allergy

•Funct­ion­ally, the respir­atory system is divided into the conducting zone and the respir­atory zone.
–Condu­cting zone
•Involved with bringing air to the site of external respir­ation and consists of the nose, pharynx, larynx, trachea, bronchi, bronch­ioles and terminal bronch­ioles.
–Respi­ratory zone
•The main site of gas exchange and consists of the respir­atory bronch­ioles, alveolar ducts, alveolar sacs, and alveoli.

•The external nose is visible on the face.
•The internal nose is a large cavity beyond the nasal vestibule.
–The internal nasal cavity is divided by nasal septum into right and left nares.

–A hollow tube that starts posterior to the internal nares and descends to the opening of the larynx in the neck.
–It is formed by a complex arrang­ement of skeletal muscles that assist in swallowing
–It functions as:
•a passageway for air and food
•a resonating chamber for sound
•a housing for the tonsils (lymphatic organs)

•The oropharynx lies behind the mouth and partic­ipates in both respir­atory and digestive functions.

–composed of 9 pieces of cartilage, forms a short passageway connecting the laryng­oph­arynx with the trachea (the “windp­ipe”).
–The thyroid cartilage (the large “Adam’s apple”) and the one below it (cricoid cartilage) are landmarks for making a temporary emergency airway (called a cricot­hyr­otomy).

–a semi-rigid pipe made of semi-c­ircular cartil­aginous rings (hyaline cartil­age), and located anterior to the esophagus.
–It is about 12 cm long and extends from the inferior portion of the larynx into the medias­tinum where it divides into right and left primary (1o, “mains­tem”) bronchi.

•The 1st bronchi divide to form 2nd (secon­dary) and 3rd (tertiary) bronchi which respec­tively supply the lobes and segments of each lung.
–3rd bronchi divide into bronch­ioles which in turn branch through about 22 more divisions. •The smallest are the terminal bronch­ioles.

•All the branches from the trachea to the terminal bronch­ioles are conducting airways

–the movement of air between the atmosphere and the alveoli of the lungs
–It consists of inhalation and exhala­tion.

•A barometer is an instrument that measures atmosp­heric pressure.
–Baro = pressure or weight
–Meter = measure
–Air pressure varies greatly depending on the altitude and the temper­ature.

•Boyle’s law states that volume and pressure are inversely related.

–Pressure in the pleural cavity
•Pleural cavity is sealed space between the surface of the lungs and internal chest wall
–Changes when breathing
–This should always be a negative pressure (<Patm and <Ppul) in order to prevent lung collapse
–Plural fluid helps limit friction between lungs and thoracic wall, but the fluid amount must be kept to a minimum
•Excess is pumped out by lympha­tics•If accumu­lates  positive Pip pressure  lung collapse

•This causes the lungs to expand thus increasing their volume and decreasing the pressure at the alveoli below that of atmosp­heric
•Air rushes in from the higher external atmosp­heric pressure to the lower internal alveoli pressure causing the lungs to fill in an effort to equalize the two pressures
•This is respon­sible for about 75% of air that enters the lungs during resting (quiet) breathing

Accessory muscles of inhalation
–Involved in active inhalation
•These assist in increasing thoracic volume during exercise or deep, forceful inhala­tions
–Stern­ocl­eid­oma­stoid
•Elevates the sternum
–Scaline
•Elevates the first two ribs
–Pecto­ralis minor
•Elevates ribs 3-5

–Forceful exhalation
•Yelling, exercise, or playing a wind instrument
–Requires muscles of exhalation
•Abdom­inals
–Moves the inferior ribs downward and compresses the abdominal viscera» Forces the diaphragm superiorly
•Internal interc­ostals
–Pulls the ribs inferiorly (downward)

3 other factors also affect the ease with which we ventilate:
–The surface tension of alveolar fluid
–Compl­iance of the lungs
–Airway resistance

–A mixture of phosph­olipids and lipopr­oteins present in the alveolar fluid
–Reduces the alveolar fluid surface tension below the surface tension of pure water by blocking some water-­to-­water intera­ctions
•Allows for easier inflation of the alveoli and helps prevent alveolar collapse during exhalation

–Restr­ictive disorders restrict lung expansion
•Pulmonary fibrosis
–Scar tissue not very elastic
•Defic­iency in surfac­tan­t•P­ulm­onary edema (excess fluid in the lungs)
–Decreases lung compliance
•Impedance to expansion
–E.g. Ventil­atory muscle paralysis, broken ribs, obesity

•Press­ure’s role in airway resistance
–As the lungs expand during inhala­tion, the bronch­ioles enlarge because they are expanding outward in all directions
•This decreases resistance to flow in to the lungs
–As the lungs expand during inhala­tion, the bronch­ioles enlarge because they are expanding outward in all directions
•This increases resistance to flow out of the lungs
•Any condition that narrows, or obstructs, the airways increases resistance