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Chapter 37 Respiratory System. Respiratory System (Breathing). Respiration vs Breathing. Variations in Breathing Structures (represents evolutionary trends). Cell membrane  in unicellular organisms Ex: Cnidaria , Porifera 2. Moist skin  mucus secreting cells maintain moisture

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Chapter 37 Respiratory System

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variations in breathing structures represents evolutionary trends
Variations in Breathing Structures (represents evolutionary trends)
  • Cell membrane in unicellular organisms

Ex: Cnidaria, Porifera

2. Moist skin mucus secreting cells maintain moisture

Ex: Worm phyla

  • 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
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
Breathing Organs Overview
  • Earthworm moist skin
  • Starfish skin gills
  • Clams gills (squid)
  • Grasshopper tracheae
  • Crayfish gills
  • Perch gills
  • Human lungs
human respiratory system
Human Respiratory System
  • 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
  • Bronchiole smaller branches w/in lungs
  • Alveolus (i) microscopic air sac
  • 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
Breathing Muscles
  • Diaphragm sheet of voluntary muscle found between the thoracic and abdominal cavities in mammals
  • Intercostal (rib muscles) muscles b/t rib bones (internal & external layers)
breathing mechanism
Breathing Mechanism
  • Inhalation- intake of air due to contraction of:

1. Diaphragm- when diaphragm contracts itstraightens

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

  • Exhalation

1. Muscles relax, volume decreases, pressure increases and exhalation occurs

nerves controlling breathing medulla
Nerves Controlling Breathing (Medulla)
  • 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+ + 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

  • 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)
O2 Transfer from Blood to Body Tissues
  • 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