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 moistureEx: 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 sinusEx: Insects (grasshopper)

4. Gills thin filamentous structures composed of capillaries and flat squamous epithelial cellsEx: 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

1. Earthworm moist skin2. Starfish skin gills3. Clams gills (squid)4. Grasshopper tracheae5. Crayfish gills6. Perch gills7. Human lungs

Human Respiratory System1. Nasal Cavity ciliated columnar epithelium- secrete mucus2. Pharynx back of throat3. Epiglottis flap of tissue over glottis4. Glottis opening to trachea5. Larynx voice box6. Trachea windpipe7. Left and right bronchus(i) bronchial tubes that leads to

bronchioles8. Bronchiole smaller branches w/in lungs9. Alveolus (i) microscopic air sac10. Capillary bed around alveoli site of gas exchange

(oxyhemoglobin H6 + 4O2 = H6O)11. Venules small veins12. Pulmonary veins to left atrium- part of the pulmonary circuit of

the circ system13. Pulmonary artery to lungs (fr right ventricle)

Breathing Muscles1. 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 MechanismA. Inhalation- intake of air due to

contraction of:1. Diaphragm- when diaphragm contracts it straightens2. External intercostal- when contracted these muscles lift rib cage up and out3. Thoracic cavity enlarges & air rushes into inflate lungs (Intrathoracic pressure low- low pressure on lungs)- Result: Inhalation occurs

B. Exhalation1. 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 nerveRESULT: Exhalation

3. BLOOD pH = 7.4- CO2 conc of blood is the factor which regulates breathing rate (blood pH)

CO2 + H2O ← ↕ → H2CO3 ↔ H+ + HCO3-

RBC (lungs) carbonic anhydrase carbonic acid (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, light-headed, & weak (vasoconstriction)

• CO2 Transfer from Body Tissues to Blood and Lungs

1. CO2 leaves cells and enters tissue spaces

2. CO2 enter capillaries3. CO2 reacts with H2O (RBC) H2CO34. H2CO3 dissociates into H+ and

HCO3- (bicarbonate ion)5. HCO3- leave RBC and enter plasma6. Blood travels to lungs and enters lung

capillaries7. HCO3- reenters RBC8. HCO3- + H+ H2CO39. H2CO3 + carbonic anhydrase

(enzyme) H2O +CO210. W/in RBC, CO2 enters plasma11. CO2 leaves lung capillary and enters

alveolar space (result:CO2 exits out of mouth)

O2 Transfer from Blood to Body Tissues

1. RBC enters lung capillary2. O2 from alveolar space enters lung

capillary plasma3. O2 enters RBC from plasma;

combines with hemoglobin (Hb) = oxyhemoglobin

4. RBC carry oxyhemoglobin out of lung to body tissues

5. O2 laden RBC enter tissue capillary6. Oxyhemoglobin breaks down,

releasing O2 into plasma7. O2 leaves plasma and enters tissue

space8. O2 enters tissue cells from tissue

space9. 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