Fish Anatomy

1. Fish Anatomy

2. Anatomy/Physiology
Definition of terms:
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Anterior (cranial)
Posterior (caudal)
Cranial
Caudal
Dorsal
Ventral
Medial
Distal
Proximal
toward the head
toward the tail
head region
pertaining to the tail region
toward the back (top) of the animal
toward the belly of the animal
toward the median line
away from the center or origin
toward the center or origin

8. Anatomy/physiology
• External Anatomy of fish
– The body: divided into head, trunk, and tail.
– The scales: primary protection, but still a place
pathogens could infiltrate.
• Even the head is covered by epidermis and
some scales.

10. Anatomy/physiology
• External Anatomy of fish
– Lateral line: is present along middle side of
body.
– Head:
• Nares: located on dorsal side of the anterior
end of head.
– Each naris is divided into two portions
which permits water to circulate through the
olfactory sac.

12. Anatomy/physiology
• External Anatomy of fish
– Head:
• Eyes: located in lateral position at anterior end
of head.
• Ears??
• Operculum: Located at the posterior and
lateral positions of the head.
• Gill arch: Beneath the operculum are located
four pair of gill arches.

14. Anatomy/physiology
• External Anatomy of fish
– Head:
• Gill arch:
– Each arch bears a gill on its outer surface.
– Each gill consists of two rows of filaments.
– Each filament consists of numerous
lamellae.
– Inner margin of arch bears a single row of
tooth-like projections the gill rakers.

16. Anatomy/physiology
• Sensory perception of the fish:
– Sight:
• Sight is the predominant sense of salmon.
– Hearing:
• Lateral line perceives sounds of low wave
length.
• Ear perceived sounds of higher wave length.
– Equilibrium:
• Organs of equilibrium are the lateral line and
the ear.

17. Anatomy/physiology
• Sensory perception of the fish:
– Touch:
– Smell:
• Long range perception of chemicals
• Preceptors of smell through olfactory sac
– Taste:
• Taste is the perception of chemicals upon
contact.
• Taste buds:
• Taste buds located on tongue and head.

21. Anatomy/physiology
• Sensory perception of the fish:
– Kinesthetic perception?
– Temperature:
• Function of lateral line

22. Anatomy/physiology
• Functions of various sense organs:
– Eye:
• Sight
– Ear: Inner ear
• Equilibrium and hearing
– Nares:
• Smell
– Lateral line:
• Hearing, equilibrium, touch, perception, and
temperature

23. Anatomy/physiology
• Internal Anatomy
– Skeletal system:
• The function of the skeletal system is one of support.
– Skeletal tissues:
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– Axial skeleton:
• Head, trunk, and tail regions.
– Head:
– Trunk skeleton: modified portion of the
vertebral column.
– Tail skeleton: remainder of the vertebral column

26. Anatomy/physiology
• Supporting tissues:
– Connective tissue: ligaments, tendons, septa, fascia,
and mesenteries.
• Ligaments: tough bands of tissue between bones.
• Tendons: thick narrow bands by which muscles are
attached to the skeleton.
• Septa: are heavy tissues which separate various
portions of the body.
• Fascia: are the thin sheets of connective tissue
which surround muscles.
• Mesenteries: are delicate tissues which support the
organs of the body cavity.

27. Anatomy/physiology
• Muscular system:
– Three types of muscle tissue: smooth, striated, and
cardiac.
– Smooth and cardiac: muscles are involuntary.
– Striated muscle is voluntary.
– Smooth or involuntary muscles:
• Found in various organs
–
–
– Cardiac muscle: is striated but involuntary.
– Primary function of muscles is motion and locomotion.

28. Anatomy/physiology
• Digestive system:
– Mouth, pharynx, esophagus, stomach, small
intestine, pyloric cecae, liver and pancreas.
– Mouth: grasping organ; teeth function to
retain prey.
– Pharynx: leads to the esophagus:
– Esophagus: muscular tube leading from the
pharynx to the stomach.

31. Anatomy/physiology
• Digestive system:
– Stomach: consists of two parts:
• Cardiac:
• Pyloric:
– At end of pyloric section: heavy muscle
» Pyloric sphincter:
»

33. Anatomy/physiology
• Digestive system:
– Intestine: duodenum, and small and large
intestines.
– Duodenum: short portion of the intestine
» pyloric caeca are attached and which
receives the bile duct and the pancreatic duct
»
– Small intestine: predominant portion of
intestinal tract.
– Large intestine: extremely short and located
just anterior to the anus.

35. Anatomy/physiology
• Digestive glands in the salmon and trout
include the gastric and intestinal glands, the
liver, and the pancreas.
– Gastric glands:
– Intestinal glands:
– Liver: a bilobed organ located in the anterior and
left lateral portion of the body cavity
• Gall bladder: a thin-walled sac embedded in the
liver,
• Bile duct:

38. Anatomy/physiology
• Pancreas: diffuse gland located on the
pyloric caeca
– Pancreatic duct: discharge enzymes into the
intestine
• Pancreatic juices contain 3 enzymes that act on
proteins, carbohydrates, and fats

39. Anatomy/physiology
• Respiratory system:
– Gills: Function to exchange gases
• Oxygen absorbed through gills into blood
•
• Gas exchange:
– Flow from dense to less dense
– Air bladder: doesn’t function as respiratory
organ in salmonids
•
• Fry and fingerling stages: air bladder connected
by duct to the esophagus (surface feeding?)

40. Anatomy/physiology
• Circulatory system: Blood and lymph
systems
– Blood: Fluid tissue – liquid plasma and cellular
components
• Plasma: 80% water
– Proteins and carbohydrates
– Waste materials (urea and uric acid)
– Mineral salts
– Enzyme secretions from glands
– Antibodies

41. Anatomy/physiology
• Blood cells
– Red cells (erythrocytes)
• Flattened, nucleated cells with hemoglobin
– White cells (leukocytes)
•
– Thrombocytes: Present in blood and aid in formation
of blood clots
• Blood vessels: Closed system which blood circulates
– heart, arteries, veins, and capillaries
– Heart: Consists of 2 chambers - auricle(atrium) and
ventricle

43. Anatomy/physiology
• Lymph system: consists of plasma and
leukocytes
– Starts in the intercellular spaces and eventually empty
into veins
–
– Spleen is associated with lymphatic system
– GALT and MALT
• Blood producing organs:
–
• Functions is same as bone marrow in mammals
– Spleen, lymph nodes, and thymus:

44. Anatomy/physiology
• Primary functions of major organs:
• Pancreas:
• Spleen: produces leukocytes, serves as a
storage space for RBCs, and destroys worn
out red blood cells
• Kidney: divided into 2 parts
– Anterior: produces red and white blood cells
– Posterior:
• Swim bladder: hydrostatic organ

46. Anatomy/physiology
• Heart: serves to move blood through circulatory
system – consists of atrium, ventricle, and bulbous
arteriosis (smoothes out pressure to steady flow)
• Liver:
– Detoxification, digestion, excretion, and
hematopoiesis
• Digestion: secretion of bile salts
• Excretion: destruction of worn out RBCs,
conversion of hemoglobin into bile salts and
ammonium salts into urea
• The liver also serves for storage of glycogen
(animal starch)

47. Anatomy/physiology
• Gastro-intestinal tract:
– Cardiac and pyloric stomach:
•
– Pyloric caeca:
– Small intestine: digestion and absorption of food
• Enzymes secreted by glands – break down proteins
and carbohydrates
• Carbs. and proteins absorbed directly in to
bloodstream
– Large intestine: serves as storage space for
accumulation of waste before excretion