Anatomy and Function of a Fish

1. Anatomy and Function of a Fish Part 2

2. Muscular System • The general function of the muscular system is to move parts of the body. • Muscles are tissues that can contract to shorten, or relax to lengthen. • Fish move by contracting and relaxing their muscles.

3. Fish have 3 types of muscles: • Skeletal muscles • Smooth muscles • Heart muscles

4. Skeletal Muscles • Skeletal muscles: Move the skeleton. • Are composed of bundles of cells. • When the cells are stimulated by nerves, the muscles contract. • When just a few cells are stimulated, the muscles shortens lightly.

5. When more cells are stimulated, the muscle shortens more. • Under a microscope, skeletal muscles appear as small cross-bands or striations.

6. Muscles are attached to bones by strong connective tissues called tendons. • When muscles shorten, the pull on tendons moves bones.

7. Skeletal muscles are also called striated muscles. • Their nerve control is voluntary. • Voluntary movement is when the thinking part of the brain signals movement. • To swim, animals must learn to contract and relax their skeletal muscles.

8. Most of the body of the fish from the head to the tail is composed of layers of skeletal muscle. • Layers are arranged in W-shaped bands attached to the skeleton and the skin. • This interlocking network of muscles allows the fish to move the body back and forth in a smooth, undulating motion. • If muscles ran along the length of the body rather than W-shaped, movement would not be possible.

9. How does a fish swim? • A fish swims by alternately contracting muscles on either side of its body. • Swimming begins when the muscles on one side of the body contract, pulling the caudal fin toward the side. • Sideways movement of the caudal fin pushes the fish forward. • Then the muscles on the opposite side of the body contract and the caudal fin moves toward the other side of the body.

10. Fish, including sharks, swim with a side-to-side motion. • Humans wearing fins, and porpoises swim with an up-and-down motion. • Like fish, porpoises move their tail when the muscles of the body contract. • As the tail moves, it pushes on the water and moves the animal forward.

11. Skeletal muscles are also attached to bones that move the other fins. • Many fish swim both forward and backward by flapping their pectoral fins. • Some fish may use their pectoral fins for steering. • Fish with wide pectoral fins use them for propulsion.

12. Skeletal muscles also move dorsal fins. • Faster-swimming reef fish reduce water drag by tucking in their dorsal fins. • Slower-swimming fish have larger dorsal fins, which they sometimes flare to protect themselves from other fish.

13. Fins Summary • Fins allow fish to move in many directions. • Fins allow the fish to steer and to move backward, up, and down. • In a few species, modified fins are used as suction cups for walking on the bottom. • In other species, modified fins facilitate flying(gliding).

14. Smooth Muscles • Smooth muscles: Move internal organs of the body and line tubes such as the intestinal tract and blood vessels. • Under a microscope, smooth muscles are non-striated. • Their nerve control is involuntary; they move without signals from the “thinking” part of the brain. • Example: Smooth muscles automatically contract and relax in waves to push food through the digestive tract.

15. Heart Muscles • Heart muscles: Move blood. • Their nerve control is involuntary. • By rhythmically contracting and relaxing, they pump blood through the blood vessels. • Under a microscope, cross-striations in heart muscles are visible, therefore they are not included in the category of smooth muscles.

16. Digestive System • The function of the digestive system is to break food particles into molecules that can pass into the bloodstream, which carries them to the cells of the body. • The digestive organs include: • Mouth • Teeth • Tongue • Stomach • Intestine • Anus • Digestive glands

17. The digestive system is a long tube beginning at the mouth and ending at the anus. • Specialized regions in the tube perform different functions. • Glands attached to this tube produce chemicals that break food into nutrient molecules. • Nutrient molecules are the building blocks and food source used in making and maintaining cells. • The most common nutrients are fats, amino acids, sugars, minerals, water, and vitamins.

18. Food is pushed through the digestive tube by smooth muscles wrapped in rings around the entire tube. • When the ring of smooth muscles contracts, the tube narrows, pushing food farther along the tube. • Peristalsis is the contracting and relaxing of smooth muscles, which creates a wavelike motion that pushes undigested food along the tube to the anus.

19. Three main groups of organs make up the digestive system: (The seven digestive organs listed above are placed in one of these three main groups) • Mouth • Digestive tube • Digestive glands

20. Organ Functions in the Digestive System • Mouth: Takes food and water into the body. • Teeth: Breaks up food into smaller pieces. • Tongue: Pushes food through the pharynx into the esophagus. • The esophagus is a short, narrow tube between the mouth and stomach. • Gill rakers prevent food from escaping through the gill covers. • The digestive tube is the passageway from the esophagus to the anus. • Food passes from the esophagus into the stomach.

21. Stomach: Digestive chemicals and acids begin the process of digestion. Food then moves into the intestine. • Intestine: Chemicals break down the partially digested food into smaller molecules, which pass into the blood stream through the walls of the intestine. • Only molecules can pass into the bloodstream.

22. Anus: Allows undigested food to pass out of the intestine. • Undigested material collects in the posterior part of the intestine and passes out of the body through the anus in a process called defecation. • Solid material collected is called the feces.

23. Digestive glands: Produce digestive chemicals that aid in breaking food into smaller molecules. • Examples of digestive glands are the pancreas and the liver. • Liver: Produces bile, a substance that breaks fats and oils into smaller particles.

24. Gall bladder: Connected to the liver. Stores the bile produced between meals. • The pancreas lies next to the stomach. • The pancreas and other small digestive glands lining the intestines produce chemicals called enzymes, which travel from the glands into the intestine through small tubes called ducts. Respiratory System is Next!!