internal anatomy

Question 1

swim bladder

Answer 1

• present in most bony fish
• located below the backbone
• filled with gas controlled by the blood
• provides buoyancy, enabling the fish to remain at a particular depth
• gas is regulated by the nervous system
• serves as an air-breathing lung in lungfish
• sharks, rays + many bottom dwellers lack a swim bladder

Question 2

gills

Answer 2

• diffuse oxygen from the water into the bloodstream
• take in water through the mouth and expel it through the gills where it passes through the gill membrane into the bloodstream
• water passes over the gill filaments, which absorb the oxygen and replace it with carbon dioxide

Question 3

heart

Answer 3

• consists of two chambers; atrium + ventricle
• blood flows through veins and into the atrium, then to the ventricle
• muscles in the ventricle pump blood through arteries to the gills, where it receives oxygen and gives off carbon dioxide

Question 4

liver

Answer 4

• produces bile from the breakdown of old red blood cells
• secretes enzymes that break down fats
• storage area for fats + carbs
• production of blood cells + antibodies
• involved in waste excretion

Question 5

kidneys

Answer 5

• located close to the spine in the abdominal cavity
• anterior part of the kidney forms blood
• posterior kidney is involved in osmoregulation → produces urine + helps regulate salt levels in the body

Question 6

digestive system

Answer 6

• digestive system leads from the mouth to the vent
• food passes through the pharynx on the way to the oesophagus, which can expand easily for fish to swallow their food whole
• food then passes into the stomach, where it is partially digested
• some fish have their oesophagus or stomach enlarged into a gizzard; which grinds food into small pieces prior to entering the intestines
• digestive process is completed in the intestines
• digested food enters the bloodstream, and waste products pass out through the vent

Question 7

pyloric caeca

Answer 7

• located near the junction of the stomach and intestines
• has fringe-like projections
  secretes enzymes that aid digestion, and absorb digested food

Question 8

gallbladder

Answer 8

• stores + releases bile, which is secreted into the intestine to neutralise acid from the stomach
• helps digest fats in food
• usually a bright yellow or green depending on the colour of bile it stores

Question 9

spinal cord

Answer 9

• connects the skull and tail
• made up of numerous vertebrae to house and protect the spinal cord
• connects the brain to the rest of the body
• relays sensory information from the body to the brain and instructions from the brain to the body

Question 10

brain

Answer 10

• the control centre of the fish where automatic functions and higher behaviours occur
• all sensory information processed here

Question 11

vent

Answer 11

• located in front go the anal fin
• acts as a urinary, digestive and reproductive opening