Organ Systems of Fish A quick overview of fish body systems
What is a System? • A system is a group of organs that work together and provide an organism with an advantage for survival. • It is the most complex organizational level in an organism • Systems work alone and with other systems to allow your body to maintain homeostasis. • Homeostasis is a stable internal environment that allows each body cell to survive.
If Homeostasis is a stable internal environment that allows you (and your cells) to survive. • Then some examples of homeostasis would be… • Maintaining blood pressure • Maintaining electrolyte levels (mineral salts in the blood) • Maintaining the proper oxygen level in the blood • Supplying the body with a consistent supply of energy and nutrition • Removing cellular wastes from the blood ALL these processes and more are accomplished by organs working in systems to keep the organism alive.
Organs Working Together • Organs are a part of every system. • For example: The heart is classified as an organ and it is a part of the circulatory system. • Organs can work within several systems of your body. • Many organs also have specific cells or tissues that have different functions.
Systems Can't Work Alone • Systems rarely work alone. • All of the systems in an organism are interconnected. • A simple example is the connection between the circulatory and respiratory systems. Bodies need O2,;blood circulates and when it reaches the lungs or gills, part of the respiratory system, the blood is re-oxygenated.
Differences among animals • Different animals have different organs and systems that work in different ways to accomplish the same objective. • For example: • Fishhave gills whereas marine & terrestrial animals have lungs
Examples of Systems • Nervous • Muscular • Reproductive • Endocrine • Skeletal • Digestive • Integumentary • Respiratory • Circulatory • Excretory
Digestive system • In fish, food is ingested via the mouth then mechanically broken down in the esophagus. • As it enters the stomach, the food is further chemically digested by enzymes and acids. Then nutrients are released to be absorbed as they passes through the intestine. • Organs such as the liver and pancreas add enzymes and bile as the food moves through the digestive tract. • What is not absorbed from the food passes out as feces..
Respiratory system • Most fish exchange gases by using gills that are located on either side of the pharynx. • Gills are made up of capillary-filled feathery structures called filaments • They have a large surface area for the exchange of oxygen and carbon dioxide from the blood
Some fishes, like sharks and lampreys, possess multiple gill slits (openings). • However, most fishes have a single gill opening on each side of the body. • This opening is hidden beneath a protective bony cover called an operculum.
Notice the bright red colorSee how gossamer-like and feathery they are.
Also part of the respiratory system is the swim bladder… • Since body tissue is denser than water, fish must create buoyancy or sink • Many bony fishes have an internal organ called a swim bladder that adjusts their buoyancy • It is like a small balloon that inflates or deflates as needed
Circulatory system • Fish have a closed circulatory system with a heart that pumps the blood in a single loop throughout the body. • The blood goes from the heart (via arteries) to gills, from the gills to the rest of the body, through capillaries, and then back to the heart via veins.
Excretory system • As with many aquatic animals, most fish release their nitrogenous wastes as ammonia • These wastes are the products of cellular respiration • Some of the wastes diffuse through the gills into the surrounding water, while others are removed by the kidneys • Kidney - excretory organs that filter cellular wastes from the blood. • Kidneys help with osmoregulation, too.,
The Excretory System & Osmoregulation • Saltwater fish tend to lose water from their bodies and gain salt because of osmosis. • In saltwater fish, the kidneys concentrate salty wastes and return as much water as possible back to the body. • Think: the interior of marine fish has a lower concentration of salts than the sea, because the kidneys are regulating salt content, so water will flow out the fish into its environment.
The Excretory System & Osmoregulation • Contrarily, freshwater fish tend to gain water continuously • The kidneys of freshwater fish are specially adapted to pump out large amounts of dilute urine • Some fish have adapted kidneys that allow them to move from freshwater to saltwater. • Think: the interior of the freshwater fish has a higher concentration of salts than the water, because the kidneys are regulating salt content, so water will flow into the fish into its environment.
Central nervous system • The central nervous system controls the movement and actions of the fish. • The major organ in the central nervous system is the brain. • Fish typically have quite small brains relative to body size when compared with other vertebrates • Some fish have relatively large brains, most notably sharks
Forebrain: both the Olfactory Lobes and the TelencephalonMidbrain or Mesecephalon has the Optic LobesHindbrain orMetencephalon is only the CerebellumBrainstem • Anterior (Front) • Posterior (Back)
Fish Forebrain Forebrain • Receive and process signals from the nostrils • The olfactory lobes are very large in species that hunt primarily by smell, such as hagfish, sharks, and catfish. • Behind the olfactory lobes is the two-lobed telencephalon that processes olfaction (smell) • Together these structures form the forebrain.
Fish Midbrain • The midbrain or mesencephalon contains the two optic lobes • These are very large in species that hunt by primarily by sight, such as bass, trout and cichlids Midbrain
Fish Hindbrain Hindbrain • The hindbrain, or metencephalon controls voluntary muscle actions such as swimming & balance • The cerebellum is a single-lobed structure that is usually very large, typically the biggest part of the brain
Fish Brainstem • The brain stem, or myelencephalon, is the most posterior part of the brain • The brain stem controls involuntary basic functions, such as respiration, reproduction and organs Brain Stem
Forebrain: both the Olfactory Lobes and the TelencephalonMidbrain or Mesecephalon has the Optic LobesHindbrain orMetencephalon is only the CerebellumBrainstem • Controls… • Controls…. • Controls… • Controls…
Muscular system • Most fish move by alternating the contraction right-side and left-side skeletal muscles • These contractions form S-shaped curves that pulse down the body of the fish posteriorly • Each muscle contraction draws the caudal fin forward creating forward propulsion • Reverse, poorly accomplished in most fish except the eel, is accomplished by moving the pectoral fins as if they were oars • The fish's fins are used to stabilize the fish, and help them to reverse
Reproductive system • Fish reproductive organs include testes and ovaries • Eggs are masses that may look like these • Another close up?
Freshly-hatched from the egg, the yolk sac is still visible on this salmon fry until it is absorbed into the body
Reproduction in Fishes • Viviparous- give birth to live young – placental mammals do this as do a few egg-producing vertebrates • Oviparous– lay eggs – most fish are these type • Ovoviviparous – have eggs but hold the developing eggs until they hatch – sharks do this