1. Fish Internal Anatomy and Physiology
Objectives:
Describe the function of major organ systems in bony fish and list the specific organs in each system.

2. Digestive System food enters mouth through esophagus
into the stomach for digestion
Typically J-curvied, elongated, modified to grind, or lost
Intestine
Pyloric caecae – slender blind tubes that secrete digestive enzymes
liver secretes bile that breaks down fat

3. Digestive Continued Carnivorous fishes Herbivorous fishes Sharks
Short, straight intestines
Herbivorous fishes
Coiled intestine
Sharks
Spiral valve – increase surface area for digestion and absorbing nutrients

4. Circulatory System two-chambered heart beneath the gills
gas exchange takes place in gills
oxygenated blood is carried through the arteries
Capillaries allow oxygen and nutrients to reach the cells
veins carry deoxygenated blood and carbon dioxide back to the heart

6. Respiratory System

7. Irrigation of gills “irrigate” – water flows over the gills
Cartilaginous fish
Open and close the mouth
Every gill is in its own chamber
1st pair of gill slits is modified into spiracles
Allow bottom fish to breathe

8. Bony fish Gills on each side share a gill chamber
When mouth opens, opercula close, pharynx expands, sucking in water
Lamellae
Thin plates in rows on gill filament
# of lamellae increase with active swimmers

9. Respiratory System (Gills)

11. Nervous System central nervous system
brain and spinal cord
nerves connect the central nervous system with all of the organs
sensory organs
Eyes – focus moving closer and farther
Nictitating membrane – reduce brightness, protect during feeding
lateral lines – sense pressure changes, vibrations
nostrils and olfactory sacs – smell
taste buds – mouth, fins, skins, barbels
inner ears – hearing and balance

13. Special Organ Swim bladder Controls buoyancy
Inflates as the fish moves up
Deflates as it move deeper
Absorbs or releases gas into the bloodstream