Fish anatomy and physilogy

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

Anatomy/physiologyAnatomy/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.

– 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.

– 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.

– 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.

• 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.

– 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.

– Kinesthetic perception?
– Temperature:
• Function of lateral line

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

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

• 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.

• 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.

• 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.

– Stomach: consists of two parts:
• Cardiac:
• Pyloric:
–At end of pyloric section: heavy muscle
»Pyloric sphincter:
»

– 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.

• 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:

• 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

• 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?)

• 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

• 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

• 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:

• 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

• 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)

• 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

Fish anatomy and physilogy

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