Respiratory System

Front 1

respiratory system primary function is:

Back 1

to obtain Oxygen for use by cells and eliminate carbon dioxide produced by cells

Front 2

Respirtation is two separate processes:

Back 2

Internal and External respiration

Front 3

Internal (cellular) respiration:

Back 3

mitochondria metabolize foodstuffs; usually involves use of oxygen;results in production of carbon dioxide and water

Front 4

External respiration:

Back 4

exchange of gases between environment and cells

Front 5

Steps of external respiration: (4)

Back 5

1. ventilation or gas exchange between atmosphere and air sacs (alveoli) in lungs
2. exchange of oxygen and carbon dioxide between air in alveoli and blood
3. transport of oxygen and carbon dioxide between lungs and tissue ( in circulatory systemnot respiratory system)
4. exchange of oxygen and carbon dioxide between blood and tissues ( internal respiration)

Front 6

Nonrespiratory functions:

Back 6

route for water loss and heat elimination;enhances venous return (respiratory pump);contributes to maintenance of normal acid-base balance;enables vocalizations;defends against inhaled foreign matter (cilia, mucus);modifies, activates, and inactivates materials passing thru circulatory system;nose = organ for smell

Front 7

respiratory system components:

Back 7

lungs (2) left and right, each with several lobes; nasal passage/ oral cavity (1), pharynx, larynx, trachea, bronchi (2), bronchioles (32), terminal bronchioles (60,000), respiratory bronchioles (500,000), alveolar ducts (500,000), alveolar sacs (8 million), alveoli (~300 million) , and associated muscles for movement

Front 8

alveoli =

Back 8

sites of gas exchange

Front 9

alveolar sacs surrounded by pulmonary capilaries =

Back 9

very important for gas exchange. proximity ro capillaries and tremendous surface area = great rte of exchange by diffusion

Front 10

smooth muscle around bronchioles - autonomic nervous system stimulation of smooth muscle

Back 10

alveoli - thin walled, inlatable sacs

Front 11

fick's law of passive diffusion

Back 11

thickness, surface area, molecular weight, concentration gradient, permeability

Front 12

alveoli walls :

Back 12

single layer of flattened Type I alveolar cells. alveolar epithelium also contains type II alveolar cells which secrete pulmonary surfactant (facilitates lung expansion). alveolar macrophages also present (immune defense)

Front 13

lung tissue: series of highly branched airways, alveoli, pulmonary blood vessels, amd lots of elastic connective tissue

Back 13

occupies most of the volume of the thoracic cavity

Front 14

outer chest wall: 12 pairs of curved ribs , which join sternum and thoracic vertebrae (protection)

Back 14

diaphram: skelaetal muscle for breathing. it separates the thoracic cavity from the abdominal cavity

Front 15

pleural sac: separates each lung from the thoracic wall (chest wall)....it prevents pain from friction from breathing

Back 15

pleural cavity: the inside of the pleural sac

pleural surfaces secrete fluid into this cavity

Front 16

atmospheric pressure:

Back 16

pressure produced by weight of the air on objects on surface of earth. it is 760 mmHG at sea level. it decreases with increasing altitude above sea level

Front 17

intra-alveolar pressure (intrapulmonary pressure):

Back 17

pressure in alveoli

Front 18

intrapleural (intrathoracic pressure):

Back 18

pressure in pleural sac. it averages 756 mmHG at rest. it is also written as -4 ( 4 units below 760 mmHG atmospheric pressure). it is lost during pneumothorax (air in pleural cavity)

Front 19

transmural pressure: the lungs are normally stretched filling the thorax

Back 19

this is due in part to intrapleural fluid's cohesiveness (sticking to itself). this stickiness pulls the lungs outward.

Front 20

transmural pressure gradient across lung wall:

Back 20

net outward pressure differential between intra-alveolar pressure and intrapleural pressure

Front 21

the transmural pressure gradient pushes lungs outward when intra-alveolar pressure is greater than pressure outside alveoli

Back 21

(that is, the intrapleural pressure - this helps keep the lungs open)

Front 22

transmural pressure gradient across thoracic wall:

Back 22

net inward pressure differential between atmospheric pressure and intrapleural pressure

Front 23

transmural pressure gradient across lung wall=

Back 23

intraalveolar pressure - intrapleural pressure

Front 24

transmural pressure gradient across thoracic wall =

Back 24

atmospheric pressure minus intraplerual pressure

Front 25

changes in intra-alveolar pressure produce air flow in and out of lungs

Back 25

when intra-alveolar pressure < atmospheric pressure, air enters lungs.
when intra-alveolar pressure > atmospheric pressure, air exits lungs

Front 26

intra-alveolar pressure changed according to

Back 26

boyle's law (P1V1 = P2V2)

there is an inverse relationship between the pressure exerted by a puantity of gas and its volume. (increased gas volume, decreased gas pressure)

changes in volumes are accomplished by muscles

Front 27

inspiration:

Back 27

contraction of inspiratory muscles and expansion of thoracic cavity decreases intrapleural pressure (754 mmHG)

Front 28

contraction of inspiratory muscles:

Back 28

diaphram: innervated by phrenic nerve.
external intercostal muscles: innervated by intercostal nerves.
75% enlargement of thoracic cavity during quiet respiration due to contraction and flattening of diaphragm

Front 29

expansion of thoracic cavity decreases intrapleural pressure (754 mmHG):

Back 29

lung drawn into area of lower pressure; they expand.
increase in lung volume lowers intra-alveolar pressure below atmospheric pressure.
pressure gradient : air enters lungs

Front 30

expiration:
relaxation of inspiratory muscles ( diaphragm and muscles of chest wall, plus elastic recoil of the alveoli: decrease size of chest cavity)

Back 30

Expiration cont: intrapleural pressure increases: lungs compressed.
there is decreased lung volume and an increased intra-alveolar pressure ( increased to level above atmospheric pressure, air is forced out = expiration)

Front 31

forced expiration:

Back 31

contraction of expiratory muscles further increases pressure gradient between alveoli and atmosphere

Front 32

airway resistance influences rate of airflow

Back 32

F = chnage in Pressure gradient / resistance

Front 33

increased difference between atmospheric and intra-alveolar pressures:

Back 33

increased air flow ( F and P are directly proportional)

Front 34

increased resistance decreases airflow

Back 34

F and R are inversely proportional

Front 35

major determinant of resistance:

Back 35

radius of conducting airways

Front 36

autonomic nervous system controls contraction of smooth muscle in walls of bronchioles

Back 36

ANS can change conducting airway radii. sympathetic stimulation and epinephrine: bronchodilation. parasympathetic stimulation (at rest): bronchoconstriction (demand for airflow is low)

Front 37

increased airway resistance with chronic obstructive pulmonary disease COPD:

Back 37

group of 3 chronic diseases: chronic bronhitis, ashtma, and emphysema

Front 38

two properties allow lungs to behave as balloons, stretchng and recioling:

Back 38

elastic recoil and compliance

Front 39

elastic recoil- how readily lungs rebound if stretched:

Back 39

allows lungs to return to preinspiratory volume when inspiratory muscles relax at end of inspiration

Front 40

compliance- effort required to stretch (distend) lungs:

Back 40

analogous to effort required to blow up a balloon. thin balloon more compliant than a thick balloon. a highly compliant lung stretched farther for a given increase in pressure than a less compliant lung. decreased lung compliance in fibrotic lungs.

Front 41

pulmonary elasticity depends on:

Back 41

1. pulmonary elastic connective tissue ( lots of elastin fibers arranged to ehnance elasticity)
2. alveolar surface tension (tension determined by thin liquid film lining each alveolus. this film allows alveolus to resist expansion. this film also squeezes alveolus, producing recoil. the coating of the pulmonary surfactant prevents alveolus from collapsing from this surface tension.)

Front 42

pulmonary surfactant:

Back 42

mixture of proteins and lipids secreted by type II alveolar cells. it is found between water molecules in fluid lining alveolus.

Front 43

pulmonary surfactant:

Back 43

by reducing alveolar surface tension, it increases pulmonary compliance, reducing work required to inflate lung. it also reduces lungs tendency to recoil, so they do not readily collapse.

Front 44

the work of breathing normally requires 3% of total energy expenditure

Back 44

4 situations increase amount of work necessary:
decreased pulmonary compliance, increased airway resistance, decreased elastic recoil, and need for increased ventillation :exercise

Front 45

~500 ml of air is inspired and expired during each quiet breathing cycle

Back 45

the lungs do not completely empty after each expiration

Front 46

lung volume and capacities are measured using a spirometer

Back 46

tidal volume (TV): air entering or leaving lungs in a single breath. it equals the difference between end-expiratory and end-inspiratory volume

Front 47

pulmonary ventilation ( or minute ventilation):

Back 47

volume of air breathed in in an out in 1 minute

Front 48

respirtory rate:

Back 48

number of breaths/minute

Front 49

pulmonary ventilation =

Back 49

tidal volume ( ml/breath)X respiratory rate (breaths/min)

Front 50

average pulmonary ventilation =

Back 50

500ml/breath X 12 breaths/min = 600 ml or 6L

Front 51

anatomic dead space:

Back 51

not all inspired air reaches alveoli, where gas exchange can occur, some in conducting airways. alveolar ventilation less than pulmoary ventilation because of anatomic dead space

Front 52

alveolar ventilation =

Back 52

(tidal volume - dead space) / breath

X

respiratory rate

Front 53

average alveolar ventilation=

Back 53

(500ml - 150ml)/breath X 12 breaths per minute = 4200ml/min

Front 54

breathing patterns (deep or slow) can affect alveolar ventilation

Back 54

rest, quiet: alveolar ventilation = 4200ml/min

deep, slow breaths (increased TV, decreased rate): 5250ml/min

Front 55

alveolar dead space also exists but:

Back 55

it is usually small

Front 56

resistance of individual alveoli can be adjusted independently by local controls which act on

Back 56

smooth muscle of the airways

Front 57

accumulation of carbon dioxide in the alveoli:

Back 57

decreases airway resistance by causing airway supplying alveoli to relax

Front 58

decreased carbon dioxide has opposite effects:

Back 58

increased contraction of airways supplying alveoli, reduced airflow

Front 59

ventilation and perfusion should:

Back 59

match

Front 60

diffusion of oxygen and carbon dioxide across respiratory epithelium:

Back 60

alveoli

Front 61

transport of gases:

Back 61

blood

Front 62

breathing movements:

Back 62

supply air to respiratory surface

Front 63

key to gas eschange:

Back 63

partial pressures

Front 64

oxygen and carbon dioxide exchange at pulmonary and tissue capillaries via:

Back 64

simple exchange

Front 65

air;

Back 65

mixture of gases

Front 66

partial pressure of each gas depends onits percentage in total atmospheric pressure (760 mmHG)

Back 66

EX) oxygen is 21% of air

0.21 X 760 = 160 mmHG

Front 67

79% nitrogen in air

Back 67

partial pressure = 0.79 X 760 mm HG = 600.4 mmHG

Front 68

partial pressure gradient:

Back 68

two partial pressures for a gas in different regions of the body

Front 69

the parital pressure of oxygen:

Back 69

is greater in alveoli (100mmHG) vs. in blood of pulmonary capillaries (40mmHG)

Front 70

oxygen diffuses from alveoli into:

Back 70

capillaries

Front 71

partial pressure of carbon dioxde:

Back 71

is greater in the blood of pulmonary capillaries (46 mmHG) vs. alveoli (40mmHG)

Front 72

carbon dioxide diffuses into alveoli from:

Back 72

capillaries

Front 73

parital pressure of oxygen

Back 73

is greater in the blood (100mmHG) vs. in tissue cells (40 mmHG)

Front 74

oxygen diffuses from blood into :

Back 74

tissue cells

Front 75

partial pressure of carbon dioxide:

Back 75

is greater in tissue cells (46 mmHG) vs. in blood (40 mmHG)

Front 76

carbon dioxide diffuses into blood from:

Back 76

tissues cells

Front 77

oxygen partial pressure gradient from alveoli to blood =

Back 77

100-40= 60mmHG

Front 78

carbon dioxide partial pressure gradient from blood to alveoli =

Back 78

46-40 = 6 mmHG

Front 79

oxygen partial pressure gradient from blood to tissue cells=

Back 79

100-40 = 60 mmHG

Front 80

carbon dioxide partial pressure gradient from tissue cells to blood =

Back 80

46-40= 6 mmHG

Front 81

other factors that affect rate of gas transfer:

Back 81

srface area, distance, gas diffusion coefficient

Front 82

surface area:

Back 82

increase SA, increased reate of exhcange.
alveoli collectively: tremendous surface area
increased pulmonary blood pressure from an increased cardiac output increases surface area.

Front 83

distance:

Back 83

thin walls = rapid gas exchange

alveolar and capillary walls = thin
pulmonary edema, pulmonary fibrosis, pneumoni thicken areas for gas exchange

Front 84

gas diffusion coefficient:

Back 84

exchange directly proportional to diffusion coefficient for a gas. the coefficient for carbon dioxide is 20 times that of oxygen (CO2 is more soluble)

Front 85

98.5% of oxygen is bound to hemoglobin

1.5% is physically dissolved

Back 85

10% of CO2 is physically bound
30% of CO2 is bound to hemoglobin
60% of CO2 as bicarbonate (HCO3)