Ch. 23 - External Respiration

Front 1

external respiration

Back 1

- breathing
- transport of O2 and CO2 to and from the gas exchange membrane
- require really thin exchange surface
- no bigger than 2mm
- if larger uses convection

Front 2

3 types of specialized breathing structures

Back 2

- lungs
- external gills
- internal gills

Front 3

lungs

Back 3

- invaginated into body
- contain environmental medium

Front 4

external gills

Back 4

- evaginated from the body
- project directly into the environmental medium

Front 5

internal gills

Back 5

- evaginated from the body
- project into a superficial body cavity, through which environmental medium is pumped
- protected by opercula
- water goes into mouth, across gills, and out operculum
- unidirectional
- linear not tidal flow

Front 6

tidal flow

Back 6

- fresh medium mixes with stale medium in the lung
- O2 partial pressure of medium at exchange surface with blood is below that in environmental medium
- O2 diffuses into blood flowing along exchange surface
- O2 partial pressure in blood rises toward that in the lung
- O2 partial pressure in blood leaving the lung remains lower than that in exhaled medium
- humans and mammals

Front 7

3 types of gas exchange

Back 7

- cocurrent
- countercurrent
- cross-current

Front 8

cocurrent

Back 8

- blood and medium flow in same direction
- gradually they approach equilibrium
- least efficient

Front 9

countercurrent

Back 9

- blood and medium flow in opposite directions
- blood picks up O2 from medium and steadily encounters medium of higher O2 partial pressure
- partial pressure gradient favoring O2 diffusion into blood is maintained
- most efficient

Front 10

cross-current

Back 10

- blood and medium cross over each other
- more efficient than cocurrent

Front 11

body size and gas-exchange area

Back 11

- thicker the animal, thinner the membrane

Front 12

gas exchange through skin

Back 12

- respiratory surface
- amphibians very efficient
- humas have enough to change pH of blood

Front 13

modes of breathing

Back 13

- integument
- trachae
- external gills
- internal gills
- lungs

Front 14

integument

Back 14

- Porifera = diffusion easy
- Cniderians = diffusion easy
- Platyhelminthes = diffusion easy
- Annelids = no lungs, use skin
- thin membranes

Front 15

trachea

Back 15

- abdominal spiracles open and close for gas exchange
- system of tubes
- small animal size
- praying mantis one of largest animals to use

Front 16

gills

Back 16

- external = starfish, marine worm, vertebrates
- internal = scallop, crayfish

Front 17

diversification of breathing system in mollusks

Back 17

- aquatic snail: gill leaflets hanging in mantle cavity are ventilated by water currents from ciliary action
- clams: water for gill ventilation is drawn into and expelled from mantle cavity through siphon
- clam: cilia on sheet like gills drive water through pores into internal water channels and then exhalent siphon
- squid: gills ventilated by muscle power because they are positioned in muscle driven-water stream for jet propulsion motion
- pulmonate land snail: lacks gills but has a lung derived from mantle cavity

Front 18

arachnids

Back 18

- book lungs
- invaginations of ventral abdomen

Front 19

breathing of teleost fish

Back 19

- internal gills
- positive and negative pressure
- fresh supply of air across respiratory system
- bucal cavity = positive pressure
- opercular cavity = negative pressure
- water flows from bucal cavity to opercular cavity and out the operculum
- water flows through spaces between secondary lamellae from buccal side to opercular side
- blood flows through secondary lamellae in opposite direction

Front 20

buccal pressure pump

Back 20

- develops positive pressure in buccal cavity
- depress floor of cavity while holding its mouth open
- volume of buccal cavity increases
- water flows in
- closes its mouth and raises floor of cavity creating positive pressure
- forces water from buccal cavity across gill array into opercular cavity

Front 21

opercular suction pump

Back 21

- develops negative pressure in opercular cavity
- suck water form buccal cavity across gill array in opercular cavity
- opercular cavity expands when operculum opens
- water from environment is prevented from entering operculum because of rim valve

Front 22

breathing cycle of teleost fish

Back 22

- buccal pressure pump
- opercular suction pump
- integration of two pumps produce nearly continuous unidirectional flow of water across respiratory surface

Front 23

ram ventilation

Back 23

- many fish use on occasion and some use all the time
- speed of 50-80 cm/s or greater allow a fish to ventilate the gills without buccal-opercular pumps
- hold mouth open
- many fast swimming teleost fish cease pumping when they reach such speed
- may lower metabolic rate
- tunas, mackerel, dolphin-fish, bonitos, lamina sharks swim continuously and use ram ventilation all the time

Front 24

stimulus for ventilation

Back 24

- increased exercise potent stimulus to increase rate
- CO2 relatively weak stimulus = easy to excrete
- decrease in partial pressure of O2 in environment or in blood is potent stimulus to increase rate
- chemoreceptor cells in gills

Front 25

amphibians

Back 25

- actively ventilate
- lungs similar to ours
- not very efficient

Front 26

development of external respiration in bullfrog

Back 26

- in tadpole skin and gills account for about half O2 exchange
- in adult mostly the lungs
- skin eliminates most of the CO2 in both

Front 27

reptiles

Back 27

- sac like structures with central chamber
- well pro fused with blood only at the anterior end
- balloon like posterior end
- air flows in and out the central cavity
- gas exchange occurs in the honeycomb
- very vascularized
- single sac = unicameral lung
- multiple sacs = multicameral lung
- bronchus allow air to flow to multiple chambers of mutlicameral lungs

Front 28

birds

Back 28

- parabronchial lungs
- lungs always filled with air
- trachea = primary bronchus = mesobronchus = air sacs
- air sacs in back
- unidirectional, continuous flow
- no alveoli
- cross current gas exchange

Front 29

inhalation air flow in lung and air sacs of birds

Back 29

- posterior air sacs expand and fill with fresh air coming directly from the environment
- air flows through parabronchi from posterior to anterior
- anterior air sacs expand and fill with gas that has passed across respiratory exchange surface

Front 30

exhalation air flow in lung and air sacs of birds

Back 30

- posterior air sacs are compressed
- fresh air in the directed primarily into posterior secondary bronchi
- air flows through parabronchi from posterior to anterior
- outflow of environment along length of mesobronchus is minimal
- anterior air sacs are compressed and discharge stale air stored in them
- gas that's exhaled has passed across respiratory exchange surfaces

Front 31

parabronchi and air capillaries

Back 31

- gas exchange sites in avian lungs

Front 32

respiratory system in mammals

Back 32

- air conduction
- air filtration
- gas exchange
- air passing through larynx gives rise to speech
- air passing over olfactory mucosa leads to our sense of smell

Front 33

conditioning

Back 33

- air conditioned before it reaches the respiratory portions
- consist of warming, moistening, and removal of particulate material
- mucous and serous secretions are very important in process and also help stop dehydration of underlying epithelium

Front 34

respiratory airways of mammalian lung

Back 34

- terminal bronchioles are final branches of conducting airway system
- alveoli first appear along respiratory bronchioles
- form continuous lining along alveolar ducts and sacs
- walls of alveoli are richly invested with blood capillaries

Front 35

trachea

Back 35

- extends from larynx to middle of thorax
- divides into two primary bronchi
- lumen of trachea is pseudo stratified columnar
- trachealis muscle allows the trachea to open and close
- C ring prevents the trachea from collapsing by making sure trachea stays open
- C ring composed of hyaline cartilage
- most of surface covered with cilia and goblet cells

Front 36

goblet cells

Back 36

- produce mucous fluid
- forms layer that permits ciliary movement
- propel foreign particles out of respiratory system
- respiratory epithelium

Front 37

4 layers of wall of trachea

Back 37

- mucosa
- submucosa
- cartilaginous layer
- adventitia

Front 38

mucosa

Back 38

- ciliated, pseudo stratified epithelium
- elastic fiber rich lamina propria

Front 39

submucosa

Back 39

- denser connective tissue
- diffuse lymphatic tissue
- nodular lymphatics are present
- serous glands

Front 40

cartilaginous layer

Back 40

- C-shaped cartilages
- trachealis muscle bridges gas in cartilage

Front 41

adventitia

Back 41

- binds trachea to other structures

Front 42

perichondrium

Back 42

- connective tissue layer
- surrond hyaline cartilage

Front 43

bronchi

Back 43

- trachea divides into left and right primary bronchi
- right is wider and shorter than left
- primary bronchi enter lung and branch to give lobar/secondary bronchi
- left lung has 2 lobes
- right lung has 3 lobes
- each lobe receives lobar/secondary bronchus
- C rings turn into C plates of irregular shape
- smooth muscle appears upon entering lung and increases as cartilage decreases
- same structure as trachea

Front 44

division of lungs

Back 44

- left lung divided into 8 broncho-pulmonary segments
- right lung divided into 10 broncho-pulmonary segments
- each segment gets a segmental/tertiary bronchus

Front 45

cartilage (C) plate

Back 45

- arranged to give circular shape of bronchi
- as branching occurs plates become smaller and less

Front 46

bronchus

Back 46

- smooth muscle present in entire bronchiolar tree, including respiratory bronchiole
- elastic fibers in bronchus continue into bronchiole

Front 47

bronchioles

Back 47

- lobes of lung are further subdivided into pulmonary lobules
- each lobules supplied by bronchiole
- at 1mm diameter, C plates disappear and become bronchiole
- epithelium changes from ciliated, pseudo stratified columnar to simple cuboidal as size decreases

Front 48

clara cells

Back 48

- increase as ciliated cells decrease in number
- produce lipoprotein that prevents luminal adhesion should airway fold on itself
- not in respiratory pathway but before that in the bronchioles
- produce surfactant that hydrogen bonds in order to prevent collapsing
- non-mucous and non-ciliated secretory cells found in bronchioles of lungs
- protect bronchiolar epithelium by secreting a small variety of products
- secrete protein CCSP
- responsible for detoxifying harmful substances inhaled into lungs
- cytochrome P450 enzymes found in smooth endoplasmic reticulum help detoxify
multiply and differentiate into ciliated cells
- regenerate bronchiolar epithelium

Front 49

pulmonary acini

Back 49

- compose lobules
- terminal bronchiole
- respiratory bronchioles
- alveolar duct
- alveoli

Front 50

alveoli

Back 50

- separated from one another by thin connective tissue layer
- alveolar septum = connective tissue
- many capillaries

Front 51

respiratory bronchiolar unit

Back 51

- single respiratory bronchiole
- alveolar duct
- alveoli
- allow for respiration

Front 52

air flow through

Back 52

- terminal bronchiole
- respiratory bronchioles
- alveolar duct and alveoi

Front 53

mechanism of gas transport

Back 53

Front 54

sympathetic nervous system

Back 54

- causes bronchodilation
- relaxation of muscle
- increased diameter and airflow

Front 55

parasympathetic nervous system

Back 55

- causes bronchoconstriction
- contraction of muscle
- decreased diameter and airflow

Front 56

alveolar epithelium

Back 56

- type 1 pneumocytes
- type 2 pneumocytes
- brush cell

Front 57

type 1 pneumocytes

Back 57

- simple squamous membrane
- 95% of surface area
- shares basement membrane with capillary
- very thin

Front 58

type 2 pneumocytes

Back 58

- secretory
- cuboidal cells
- 5% of surface area
- bulge into lumen and are filled with granules called lamellar bodies
- contain surfactant that's secreted onto surface of alveoli to reduce surface tension

Front 59

brush cell

Back 59

- receptor cell
- columnar cells that bear microvilli
- basal surface is in synaptic contact with afferent nerve ending
- part of nervous system

Front 60

alveolar macrophages

Back 60

- remove inhaled particulate matter from air spaces
- remove red blood cells from septum

Front 61

surfactant

Back 61

- secreted by type 2 cell
- protein-lipid complex synthesized in rough endoplasmic reticulum and Golgi complex
- stored in lamellar bodies
- continuously secreted by means of exocytosis
- forms and overlying monomolecular film of lipid
- occuluding junctions around margins of epithelial cells prevent leakage of tissue fluid into alveolar lumen

Front 62

elastic behavior of lungs

Back 62

- elastic connective tissue fibers
- elastic recoil = rebound after stretch
- compliance = how much effort required to stretch or distend lungs
- alveolar surface tension
- attractive forces between water in liquid film that lines alveolus are responsible for surface tension
- causes recoil
- reduced as surface area or alveolar size increases
- reduced by lung surfactant

Front 63

LaPlace's law

Back 63

- magnitude of inward directed pressure in an alveolus is equal to two time the surface tension divided by radius of alveolus
- 2 alveoli of unequal size have same surface tension are connected to same respiratory bronchiole, smaller will have tendency to collapse

Front 64

emphysema

Back 64

- loss of elastic tissue
- lungs are large and hyperinflated
- blebs and paucity of vascular markings

Front 65

interstitial lung disease

Back 65

- presence of to much connective tissue
- unable to inflate the lungs

Front 66

inter-alveolar septum

Back 66

- blood-air barrier
- inter-alveolar barrier is about 0.5 um
- simple squamous epithelium of alveolus shares single basement membrane with simple squamous capillary

Front 67

gases move down partial pressure gradient

Back 67

Front 68

pleural sac

Back 68

- separates each lung from thoracic wall

Front 69

pressures important in ventilation

Back 69

- how you move air into and out of the lungs
- atmospheric
- intra-alveolar
- intrapleural

Front 70

diaphragm

Back 70

- creates thoracic and abdominal cavity
- goes from dome to flattened when breathing
- increases thoracic cavity

Front 71

intercostals

Back 71

- move the rib cage
- increase width and decrease width of ribcage and thoracic cavity
- internal intercostal
- external intercostal

Front 72

prior to inspiration

Back 72

- intrapulmonary pressure 760 mmHg
- intrapleural pressure 757.5 mmHg
- diaphragm relaxed = domed
- external intercostals relaxed
- internal intercostals relaxed

Front 73

during inspiration

Back 73

- intrapulmonary pressure 758 mmHg
- intrapleural pressure 754 mmHg
- diaphragm is contracted = flat
- external intercostals contracted
- internal intercostals relaxed

Front 74

during expiration

Back 74

- intrapulmonary pressure 763 mmHg
- intrapleura pressure 757.5 mmHg
- diaphragm is relaxed = domed
- external intercostals relaxed
- internal intercostals contracted

Front 75

lung capacity

Back 75

- contain about 2 to 2.5 L of air during a respiratory cycle
- total lung capacity = VC + RV

Front 76

tidal volume

Back 76

- air entering or leaving lungs during normal breathing

Front 77

inspiratory reserve volume

Back 77

- extra volume of air that can maximally be inspired of TV

Front 78

inspiratory capacity

Back 78

- maximal volume of air that can be inspired at end of a quiet expiration

Front 79

expiratory reserve volume

Back 79

- extra volume of air that van be actively expired by maximal contraction

Front 80

residual volume

Back 80

- minimum volume air remaining in the lungs after maximal expiration

Front 81

functional residual capacity

Back 81

- volume of air at end of normal passive expiration

Front 82

vital capacity

Back 82

- maximal volume of air that can be moved out after a maximal inspiration

Front 83

respiratory control centers

Back 83

- housed in brainstem
- responsible for generating rhythmic pattern of breathing
- medulla is main
- pons modifies

Front 84

medulla respiratory center

Back 84

- output to respiratory muscles
- inspiratory neurons synapse in spinal cord with motor neurons
- innervate diaphragm and external intercostals
- ventral respiratory group
- dorsal respiratory group

Front 85

ventral respiratory group

Back 85

- automatically stimulates spontaneous ventilation, resting, or tidal breathing

Front 86

dorsal respiratory group

Back 86

- responds to situations beyond those of resting or tidal breathing
- alter pattern for ventilation in response to physiological needs of body for O2 and CO2 exchange
- blood acid-base balance

Front 87

pontine respiratory center

Back 87

- limit inspiratory duration
- send inhibitory signals to medullary rhythmicity area
- reduce duration of inspiratory impulses causing shorter cycles which increases ventilation rate
- receive input from higher brain centers and peripheral receptors
- output fine tunes breathing rhythm during activities such as speaking, sleeping, or exercising

Front 88

ventilation modulation

Back 88

- chemosensaton of CO2, H+, and O2
- most potent stimulus isrise in CO2 partial pressure and/or H+ concentration
- sensed by medulla
- blood O2 partial pressure less important
- sensed in carotid bodies in carotid
- conscious control
- lung mechaosensors that sense stretch
- direct effect of exercise

Front 89

effect of exercise

Back 89

- not well understood
- involves stimuli generated in association with limb movement
- chemosensory controls

Front 90

low oxygen detection and response

Back 90

- whole body low O2 is monitored and ventillation is increased
- intracellular = hypoxia inducible factor 1

Front 91

hypoxia inducible factor 1 (HIF-1)

Back 91

- low intracellular O2 inhibits breakdown of alpha subunits
- promote dimerization of beta subunits with alpha subunits to form HIF-1
- HIF-1 enters nucleus and combine with hypoxia-response elements in DNA