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Circulation and gas exchange. Evolution. Open circulatory system Insects arthropods No difference between blood and interstitial fluid = hemolymph Gas exchange: rate of transfer proportional to surface area. Evolution. Fish: 1 atria 1 ventricle Heart to gills, gills to body

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Circulation and gas exchange

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Circulation and gas exchange

Circulation and gas exchange



  • Open circulatory system

    • Insects

    • arthropods

  • No difference between blood and interstitial fluid = hemolymph

  • Gas exchange: rate of transfer proportional to surface area.



  • Fish: 1 atria 1 ventricle

    • Heart to gills, gills to body

    • Water is dense with little O2 per volume

  • Gills: countercurrent exchange

    • Gas exchange (blood flows one way while outside water going in opposite direction)

    • Thermo regulation

    • kidney

Circulation and gas exchange

  • Insects: system of tracheal tubes, gas exchange throughout

  • Amphibians: 3 chambered heart

  • Reptiles: double circulation

    • Pulmonary circuit + systemic circulation

    • NO mixing of oxygenated and deox blood

Our system

Our system

  • 4 chambered heart

  • Double circulation:

    • Right side: pulmonary

    • Left side: systemic

Circulation and gas exchange

  • Rate of diffusion proportional to surface area

  • Protists: occurs over entire surface (cnid. Flats)

  • Earthworms and amphibs: across moist skin

  • Gills: warmer, saltier less O2

  • Insects: tracheal tubes: branch out to do exchange with all body parts. Open circ. System NOT involved in transport: O2 CO2



  • Reptiles

  • Birds

  • Mammals

  • Lungs not in contact with all cells of body

    • Gap bridged by circulatory system

Circulation and gas exchange

  • Pharynx: food and air, epiglottis

  • Larynx: vocal cords (air only)

  • Trachea: cartilage rings

  • Bronchi: 2. Right is more horizontal. More stuff

  • Bronchioles

  • Alveoli: air sacs and capillaries. 1 cell thick



  • Diaphragm: negative pressure

  • Tidal volume: air in and out with reg breath

  • Residual volume: air that remains in alveoli and tubes after you breath out.

  • Us: air travels down 1 way street.

  • Birds: better: are travels through… no dead ends

Controls of breathing

Controls of breathing

  • Pons

  • Medulla

  • Sensors in aorta

Circulation and gas exchange

  • Lungs: only site of gas exchange: need circulatory system

  • Breath: negative pressure breathing

  • Partial pressure: gas diffuses from its own high partial press. To low (press. Just this 1 gas contributes to the press. Of air (a mix))

Circulation and gas exchange

  • O2 does NOT dissolve easily in blood

  • Need HEMOGLOBIN to hold the O2

  • Bohr shift: increase affinity for heme to O2 when pH is elevated (by high CO2)

  • Myoglobin: protein that binds and stores O2 in muscles



  • Blood:

    • Connective tissue with liquid matrix

    • plasma and 3 types cells

    • Leukocytes, erythrocytes, platelets

    • 5L

    • Kidney maintains plasma (90% water)

  • All blood cells from pluripotent cells in bone marrow



  • If low O2

    • kidneys: erythropoietin: increase production of erythrocytes



  • Blood pressure: 2 factors:

    • Cardiac output and peripheral resistance

  • Atherosclerosis:

    • Plaques/ hardening of arteries (cholesterol, LDL)

  • Hypertension: over time, elasticity of vessels

  • Heart attack: MI, coronary arteries

  • Stroke: blocked vessel

Circulation and gas exchange

  • Control blood flow to capillaries:

    • Pre-capillary sphincter

    • Smooth muscle: constrict blood flow to that cap.

  • Lymphatic system: lymph drained out of circulating blood. Same

  • Lymph nodes: lots of WBC

Pathway of blood

Pathway of blood

  • Right atria (deox blood)

  • Right ventricle

  • Pulmonary artery

  • Lungs : pulmonary circulation

  • Pulmonary vein

  • Left atria

  • Left ventricle

  • Aorta: systemic circulation

Circulation and gas exchange

  • Atria: thinner walls

  • Ventricles: stronger

  • Valves: heart sounds are the closing of valves

    • 2 AV (atria to ventricle)

    • 2 semilunar. From ventricle out of heart

  • Pulmonary artery and veins : ONLY Time and artery carries deox and a vein carries oxygenated blood



  • Gap junctions: form communication

  • SA NODE: local control of rate. Special tissue in right atria

Circulation and gas exchange

  • Arteries: higher pressure. From heart

  • Veins: pressure from move skeletal muscle.



  • Systole

  • Diastole

  • SA node

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