Veterinary Anatomy of Internal Organs of the Fishes

Veterinary Anatomy, Anatomy of internal organs of the fishes

1. Fishes Anatomy -2
The internal Anatomy of the Fishes
By
Prof. Dr. Abdelmohaimen Mostafa Saleh
Professor of Anatomy & Embryology
Assiut University

3. Digestive system

4. Mouth:
Position of mouth:
1-superior mouth:
--present in fishes which live in the surface and
take the food from the surface.
--or those wait in the bottom to catch prey
passing over.
2-terminal mouth:
-the typical fish has its mouth at or very near the front
end of the head.
3-sub terminal:
-It is present in bottom feeders fishes
4-inferior mouth:

6. Size of mouth:
1 -Small mouth:
In fishes which absorpthe fluid from the prey.
2 -Large mouth and big sharp teeth:
In fishes which swallowed the large prey as a whole.
3 -Large mouth and weak teeth or none at all:
In fishes that can hold prey or strain plankton out of
the water.
Protrusion of mouth:
1 -Protrusiblemouth:
-presents in most fishes.
2 -Non protrusiblemouth:

7. The teeth
-The teeth present on the several of head and face
bones.
-They are found in upper or lower jaws.
1-Teeth in the upper jaw include
, maxillary, vomer
and palatines.
2-Teeth in the lower jaw may be present on
the tongue.
-Teeth have different shapes:
dagger like teeth. 2-
beak like teeth.
3-teeth are weak or may be absent .

9. Esophagus
Anatomical features:
-It is a short tube this due to the thoracic cavity is
reduced to triangular area which encloses the heart
and absence of the lungs.
-It is distensible so that relatively large victim can be
swallowed.
-Very musclar tube.
Connection with gas bladder:
1-in some fishes the esophagus communicates with
gas bladder via the pneumatic duct, these fishes are
called physostomous fishes.

10. 2-other fishes that don’t maintain this
communication are called physoclistousfishes.
3-In butter fishes the esophagus has blind
muscular sac known as esophageal sac. It acts
as storage of food.

11. Stomach:
Anatomical features:
-It is present in most fishes.
-It is absent in some fishes.
-It is highly distensible sac.
-It is highly musclarsac.
Shapes of stomach:
1-Bent muscular tube likes u or v shape.
2-Bag-shaped stomach with the opening of the
esophagus and intestine on the anterior aspect in
common arrangement.
3-Gizzard like stomach ( heavy-walled).

14. intestine:
Length of intestine:
1-Is isvery long , it is coiled or folded. It presents in
herbivorous fishes.
2-Is short, it presents in carnivorousfishes.
3-Has intermediate length , it presents in
omnivorous fishes.
Function of intestine: 1-Storage of food
2-Digestion of food

16. Thickness of intestine:
According to the type of the food, the wall of intestine
is thin or thick as fellow:
1-Thin intestiine:
in jawless fisheswhich feed on the blood or juices of
the prey.
2-Thick intestine :
in hagfisheswhich feed on flesh of the prey.

17. Cloaca:
-The true cloacais found in illdeveloped fishes as sharks,
rays and lung fishes.
-But in the remainder fishes the cloaca is absent.
-Most fishes have a separate anus.
-The anus lies in caudal part of the ventral surface of the
fish.

18. Pyloric ceca
Definition:
-They are finger like blind projections of the cranial
of the intestine.
Position:They are located just orat pyloric end of
the stomach.
Occurrence:
-They are found on of most fishes. But absent in few
fishes.
-The ceca of different species vary in size, state of
branching and the connection with the gut.

19. Number:
They are from 1 to many blind sacs
1-in sturgeons,many cecafrom a large mass, but
only a single duct leads to the intestine.
2-in salmon,there are numerous ceca,eachcecum
communicates directly with the intestine (numerous
ducts).
3-in catfishes,the cecaare absent.
Function of pyloric ceca:
Digestion and absorption

21. -There are some structures associated
with the alimentary tract which are:
Liver.
Pancreas.
Spleen.
Gas bladder.

22. Size:
-It is large in most species.
--Extremely large in few species
forming 20% of body weight.
Position:
-It lies over or partially surrounds the
stomach.
Lobation:
1-It is typically bilobed.
2-It may has one lobe as in salmon.
3-It may has three lobes as in
mackerel.
Liver:

23. Function of liver:
1-Bile secretion.
2-Glycogen storage.
3-In addition to other biochemical processes.
Gall bladder:
-It presents in most fishes and function to store liver
secretions.
-Some fishes have no gall bladder.
Drainage system:
One hepatic duct originates from each lobe of the
liver and joins the cystic duct from the gall bladder to
form the bile duct.

24. Pancreas:
Forms of the pancreas:
-Compact :usually consisting of 2 lobes (sharks).
-Incorporated :The pancreatic tissue is diffuse in or around
the liver → hepatopancreas(bony fishes).
-Function :
-Exocrine function: secretes enzymes that help in digestion.
-Endocrine function: the pancreatic islets produce insulin.

25. Spleen :
Position: It lies on or behind the stomach.
Colour:dark red in colour.
Shape:pyramidal in shape.
Function:blood cell formation.
Forms:
1-Compact spleen.
2-Diffuse spleen (spleen like tissue)
3-spleen is absent.

26. Gas bladder
-It is termed also air bladderor swim bladder.
Definition:
It is thin wallelongated sac.
Colour:
silvery white in colour.
Position:
It lies in the roofof the body cavity directly below the
kidney.
Occurence:
-It is present in most fishes.
-It is absent in some fishes as cartilagenousand some
bottomfishes.

28. Shape ofgas bladder: 1-
Single chamber:
-As salmon.
2-Two chambers:cranial and
caudal chambers connected
isthmus.
-As carp group.
3-Two chambers:two lateral
chambers which communicate
anteriorly.
4-Three chambers:
-As codfishes.
5-Multichampered:
-As some fishes.

30. Connection of gas bladder:
1-It connects with esophagus via pneumatic ductin
physostomousfishes.
2-Other fishes maintain the connection into larval or
juvenile stage, then losing it only after they
air into the gas bladder. These fishes are called
physoclistous.
Swim bladder
intestine
pneumatic duct

31. 1-Maintenanceof hydrostatic balance.
2-Help infloatingof fish.
3-Sound production: special muscles are attached near the gas
bladder.
4-Sound reception: by acting as resonator
connected with ear.
5-Respiration: they lined by highly vascular
epithelium that help in exchange of gases as in lungfishes.
Function of gas bladder:

32. Respiratory system

33. The main features of respiratory system:
1-Absence of the lung.
2-Presence of the gills.
3-The pharynx of most fishes can be divided into three cavities, the
buccaland two opercularcavities.

34. Gills:
Position:
-They lie on each side of the head just behind the oral
cavity.
-They present in one chamber called gill chamber,
open to the exterior by a single gill opening.
Number:
-They are commonly 4gills.
-But some fishes have 5-7gills.
Colour:
-The gills are bright redin colour in fresh state.

35. Formation of gill:
1-Gill arch:
It has curved apperance,
with cocavecranial aspect
and convex caudal aspect.
2-Gill rackers:
Two rawsof processes projecting from the cranial aspect of
each gill arch
3-Gill filaments:
-Two rawsof filaments extend from the caudal aspect of each
gill arch.
Function of gills:
1-Gillsreplace the lung.
2-Gillsrackersprevent food and debris from reaching the gill
filament, therefore they protect these filaments.

36. Urogenital system:
Kidneys
Colour:
-They are dark red.
Position:
-They lie retroperitoneal just ventral to vertebral column,
occupying roof of body cavity
along its entire length.
Descripition:
1-They are slender,elongatedthin organs.
2-The two kidneys are mostly fused along their length.

38. Drainage:
1-Each kidney has caudally a short
(nephric) duct which unites with its
follow forming a common median
ductwhich opens to the outside on a
urogenital papillae.
2-The common median duct dilates
forming a small urinary bladder.

39. Genital System:

40. Male Genital
System:
It consists of two testesand vas deference.
The testes:
-They are whitish, elongated, lobulated organs.
-They lie in the body cavity along the gas bladder.
-The testes lead to short vas deference.
Vas deference:
They are united together and carries the sperm into
genital opening.

43. -The testis has a thick white capsule of connective
tissue, it consists of elongate blind, branching
semineferoustubules that produce spermatozoa that
are discharged into a short vas deferens.
Genital opening:
-In most fishes there is no connection between the
genital and urinary system, there are separate
opening to the exterior for each system, with the
urinary openingposterior to the genital opening.
-In some fishes the genital and urinary systems has
a urogenital opening.

45. Female Genital System:
-It consists of two ovaries and oviduct.
Ovaries:
-The ovaries are usually of relatively larger size.
-The ovaries differ in the various species as fellow:
1-in bony fishes the ovaries are typically saccular
organs and continuous with oviduct which opens in
genital opening.
2-in most fishes the two ovaries are well separated.

46. 3-in some fishes the ovaries are so completely fused as to give the
appearance of a single organ.
4-This ovary is fused with the body wall just posterior to the anus,and the
eggs are extruded when this area ruptures, therefore the oviducts are not
functional. the rupture of the body wall heals soon after oviposition.

47. -during breeding (spawning) season the ovaries enlarge and the outer wall
becomes granulated due to the presence of numerous mature oocytes.

48. Oviduct
The oviduct differ in the various species as fellow:
1-The oviduct is continuous with the saccular
ovary. It opens in the genital pore between the
anus and urinary pore. As in bony fishes
2-The oviducts have a funnel opening anterior to
the ovaries, the eggs are release into the body
cavity, enter the funnel, they travel down in the
oviduct till the shell gland region where
fertilization occurs and horny shell or
is secreted.
-In the oviparous species the shell is tough and
protects the developing embryo.

49. -In viviparous species the shell is slight or vestigial
and the youngs develop in the posterior uterine
portion of the oviduct
3-In some fishes where the ovaries are fused
forming a single ovary the oviduct are not
functional.
4-In hagfishes, the oviduct and sperm ducts are
absent. Both the eggs and sperms reach to the
exterior through an abdominal pore just behind
the anus (external fertilization).