Transcript Chapter 37 Respiratory System

Chapter 37
Respiratory System
Respiratory System (Breathing)
(Cellular) Respiration
Breathing
1. Chemical Process
Food is oxidized by enzymes &
converted to ATP (most ATP from
mitochondria)
1. Mechanical or Physical
Exchange of O2 & CO2 (inhalation
and exhalation)
2. Cellular Process
Occurs in every cell of the body
2. Usually occurs in Specialized Organs/
body surface
(In simpler organisms thru skin/ cell
membrane)
Respiration vs Breathing
Variations in Breathing Structures
(represents evolutionary trends)
1. Cell membrane in
unicellular organisms
Ex: Cnidaria, Porifera
2. Moist skin mucus secreting
cells maintain moisture
Ex: Worm phyla
3. Tracheae air enters
spiracles (opening along
abdomen) which leads into
tracheal tubes to small air
sacs surrounded by body fluid
w/in sinus
Ex: Insects (grasshopper)
4. Gills thin filamentous structures composed
of capillaries and flat squamous epithelial
cells
Ex: Fishes, immature amphibians, crayfish,
skin gills on starfish, mollusks (clam)
Cont. Variations in Breathing Structures
Oops!!! Forgot this slide!
5. Lungs * mature amphibian,
reptiles, birds, & mammals
(possess diaphragm)
(*) skin
6. Stoma Opening on underside
of leaf- gas exchange
7. Lenticels openings in stem
when leaf drops
(Roots possess root hairs- gases
diffuse across into root)
Breathing Organs Overview
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Earthworm moist skin
Starfish skin gills
Clams gills (squid)
Grasshopper tracheae
Crayfish gills
Perch gills
Human lungs
Human Respiratory System
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Nasal Cavity ciliated columnar epithelium- secrete mucus
Pharynx back of throat
Epiglottis flap of tissue over glottis
Glottis opening to trachea
Larynx voice box
Trachea windpipe
Left and right bronchus(i) bronchial tubes that leads to
bronchioles
8. Bronchiole smaller branches w/in lungs
9. Alveolus (i) microscopic air sac
10. Capillary bed around alveoli site of gas exchange
(oxyhemoglobin H6 + 4O2 = H6O)
11. Venules small veins
12. Pulmonary veins to left atrium- part of the pulmonary circuit of
the circ system
13. Pulmonary artery to lungs (fr right ventricle)
Breathing Muscles
1. Diaphragm sheet of voluntary muscle
found between the thoracic and abdominal
cavities in mammals
2. Intercostal (rib muscles) muscles b/t rib
bones (internal & external layers)
Breathing Mechanism
A. Inhalation- intake of air due to
contraction of:
1. Diaphragm- when diaphragm
contracts it straightens
2. External intercostal- when
contracted these muscles lift
rib cage up and out
3. Thoracic cavity enlarges &
air rushes into inflate lungs
(Intrathoracic pressure low- low
pressure on lungs)
- Result: Inhalation occurs
B. Exhalation
1. Muscles relax, volume
decreases, pressure increases
and exhalation occurs
Negative Pressure Breathing
Nerves Controlling Breathing (Medulla)
1. Phrenic Nerve
• Motor nerve from medulla which causes contraction
of diaphragm and intercostal muscles
[*Motor nerves transmit impulses AWAY from CNS
to effectors]
RESULT: Inhalation
2. Vagus Nerve
• Mixed nerve (both sensory & motor) sensory fibers
transmit impulses to brain indicating that diaphragm
& intercostals muscles are contracted
- Signals inhibits further stimulation by phrenic nerve
RESULT: Exhalation
3. BLOOD pH = 7.4
- CO2 conc of blood is the factor which
regulates breathing rate (blood pH)
CO2 + H2O ← ↕ →
H2CO3 ↔ H+
RBC
carbonic acid
(lungs) carbonic anhydrase
+
HCO3(plasma 90%)
Carbonic Anhydrase enzyme in RBC which converts CO2 &
H2O to H2CO3 & H+ (also reverses this rxn at the lungs)
- Lowers blood pH (below 7.4) stimulates medulla to
increase breathing rate via phrenic nerves
4. Hyperventilation
• Rapid breathing (over
breathing- inhaling too
much O2) reduces the CO2
levels in the blood
• Less CO2 causes dilation of
arteries – blood pressure
lowers (carotid arteries to
the brain) brain receives
less blood dizzy, lightheaded, & weak
(vasoconstriction)
•
CO2 Transfer from Body
Tissues to Blood and Lungs
1.
CO2 leaves cells and enters tissue
spaces
CO2 enter capillaries
CO2 reacts with H2O (RBC)  H2CO3
H2CO3  dissociates into H+ and
HCO3- (bicarbonate ion)
HCO3- leave RBC and enter plasma
Blood travels to lungs and enters lung
capillaries
HCO3- reenters RBC
HCO3- + H+  H2CO3
H2CO3 + carbonic anhydrase
(enzyme) H2O +CO2
W/in RBC, CO2 enters plasma
CO2 leaves lung capillary and enters
alveolar space (result:CO2 exits out of
mouth)
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O2 Transfer from Blood to Body
Tissues
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RBC enters lung capillary
O2 from alveolar space enters lung
capillary plasma
O2 enters RBC from plasma;
combines with hemoglobin (Hb) =
oxyhemoglobin
RBC carry oxyhemoglobin out of
lung to body tissues
O2 laden RBC enter tissue capillary
Oxyhemoglobin breaks down,
releasing O2 into plasma
O2 leaves plasma and enters tissue
space
O2 enters tissue cells from tissue
space
RBC returns to lungs via circulatory
system
• CO2 conc in metabolically active
cells is much greater than in
capillaries, so CO2 diffuses from
the cells into the capillaries
~ 7% of the CO2 directly dissolves
in the plasma
~23% binds to the amino groups
in hemoglobin
~70% is transported in the blood
as bicarbonate ion
- H2O in the blood combines with
CO2 to form bicarbonate ions (via
carbonic anhydrase)
- This removes the CO2 from the
blood so diffusion of even more
CO2 from the cells into the
capillaries continues yet still
manages to "package" the CO2 for
eventual passage out of the body
- In the alveoli
capillaries, bicarbonate
combines with a
hydrogen ion (proton)
to form carbonic acid,
which breaks down
into carbon dioxide
and water (via
carbonic anhydrase)
- CO2 then diffuses into
the alveoli and out of
the body with the next
exhalation