Use this lecture outline to practice developing PowerPoint graphics.  Here's what I came up with.
  1. Gas exchange with water (Ch 8, pp. 212-214)
    • The respiratory organ of fish = gill = highly vascularized evaginated pouch originating off the pharynx
      1. Basic structure (study fig. 8-1 p. 212 -- this applies to sharks, bony fish):
        • gill arch = cartilagenous or bony rod (gill bar) or sheet (gill septum) running perpendicular to long axis of body
        • arch contains two blood vessels
          1. the afferent artery carries deoxygnenated blood from heart (via the ventral aorta) to gills
          2. the efferent artery carries oxygenated blood from gills to rest of body via the dorsal aorta
        • arch supports delicate gill filaments consisting of 
          1. primary lamellae extend from gill arches at right angles; contain branches of afferent and efferent arteries
          2. secondary lamellae run perpendicular to primary lamellae; contain capillary beds where majority of gas exchange actually takes place
          3. capillaries in secondary lamellae are extremely thin-walled -- the blood/water barrier is only ~ 1 micrometer thick!

            4.  
      2. Important functional features of gills (study fig. 8-2 p. 213):
        • arrangement of primary, secondary lamellae provides huge surface area for gas exchange (and huge SA for heat loss from blood . . .)
        • thin-walled capillaries minimize distance gasses must diffuse, increasing diffusion rate
        • unidirectional ventilation of water + unidirectional blood flow permits countercurrent gas exchange:
          1. maintains a favorable diffusion gradient across entire gill surface
          2. maximizes the amount of oxygen that can be "pulled" from the water moving across the gills
        • gill structure (and consequently function) varies among species, depending on oxygen demands and lifestyles (table 8.1)
activity

level

 species O2 consumption

(mL O2/g*h)

 # 2' lamellae per mm2 of 1' lamellae gill area (mm2/g body mass) O2 capacity (mL O2/100 mL blood)
high mackerel 0.73 31 1160 14.8
low toadfish 0.11 11 197 6
      1. Survey of gill types
        • lampreys: pouched gills
          1. gills arranged over both surfaces of gill pouch
          2. ridges of epithelium = gas exchange surface
          3. relatively small openings = pores to pharynx and to water
        • Elasmobranchs: septal gills
          1. large gill pouches with relatively large opening to pharynx
          2. external opening = gill slit; one gill slit per gill arch
          3. gill filaments supported by cartilagenous, plate-like septa
        • Osteichthyes: opercular gills
          1. single large gill pouch contains all gills
          2. single opening exteriorly covered by moveable, bony operculum
          3. septa are reduced to bars supporting filaments

            4.  
(note: find images to practice with at  http://www.odu.edu/~ksk/bio405/image_samples.htm )
[top ] [Seminar]  [ Dr. K home ] [ ODU Biology] [Old Dominion University] 
Kerry S. Kilburn, Ph.D
Department of Biological Sciences
Old Dominion University
Norfolk, VA  23529