Question

please explain

Fish dissection I a. anatomical terms- anterior and posterior; dorsal and ventral; caudal and cranial; transverse plane, frontal plane, sagittal plane b. External features of a bony fish: Mouth (maxilla and mandible), External nares, Eyes, Operculum, and gills, pectoral fin, anterior dorsal fin, posterior dorsal fin, anal fin, pelvic fin, Caudal fin, lateral line, anus. urogenital opening Internal features of a bony fish: air bladder, liver, stomach, esophagus, intestine, spleen, pyloric C. caeca, testes and ovary. kidney. heart

Answer 1

a) Anterior and posterior: Anterior is front and posterior is back of fish body.

Dorsal and ventral: Ventral is  'towards the stomach'. and ventral is 'towards the back'.

Caudal and cranial: Cranial is the head and caudal is the tail.

Transverse plane: It is an imaginary plane which divides the body into superior and inferior parts.

Frontal plane: It is an imaginary plane which divides the body into ventral and dorsal sections.

Sagittal plane: It is a boundary which exists between the left and right parts of the body.

b) External features of a bony fish:

Mouth (Maxilla and mandible): In bony fish, maxilla is a plate like bone that forms upper jaw, and part of the face. Hyomandibular is is a set of bones, found in the hyoid region. This is used to suspend the jaws.

External nares: Nares do not connect to the oral cavity. These are pits of different depth and shape.

Eyes: Eyes are almost similar to to terrestrial vertebrates like mammals and birds. Though their eyes have more spherical lens. Retinas of these fishes have both cone cells and rod cells for photopic vision and scotopic vision. They have colour vision.

Operculum and gills: Gills are located under the operculum. They have five pairs of gills. Gills are a respiratory organ. This functions to extract oxygen form water.

Pectoral fin: Just behind the operculum, paired pectoral fins are found on each side of the body. These are homologous to the tetrapods forelimbs.

Anterior and posterior dorsal fin: These dorsal fins assist fishes in sudden turns and stops and protect the fish against rolling.

Anal fin: Behind the anus, the anal fin is found on the ventral surface. This fin functions to stabilize the fish during swimming.

Pelvic fin: These are found ventrally below the pectoral fins. They assist the fish in going up or down in the water, stopping quickly and turning sharply.

Caudal fin: It is the tail fin. It is found at the end of the caudal peduncle. It functions in propulsion.

Lateral line: This is a sense organ. This functions to detect vibration and movement in the surrounding water.

Body-Anus: Before the end of the body,  body-anus opens to the exterior.

Urogenital opening: Urogenital opening is present behind the anus.

c)  Internal features of a bony fish:  

Air bladder: Bony fish have a swim bladder that functions to maintain a constant depth in the water. This air bladder is open to the esophagus.

Liver: Liver is very important organ in bony fish which has lots of functions that include protein synthesis, detoxification and production of biochemicals needed for digestion.

Stomach: To meet the pyloric sphincter, stomach curves  left before curving back.

Esophagus: It is part of the digestive tract connects fish mouth to the stomach.

Intestine: In bony fish, the intestine is very short, it is around one and a half times the body length of fish.

Spleen: In bony fish, spleen spleen contains red pulp. It is an elongated organ. It lies inside the intestinal serosal lining.

Pyloric caeca: At the beginning of the large intestine, pyloric caecum is a pouch like structure. It receives faecal material from the ileum. It is connected to the ascending colon of the large intestine.

Testes and ovary: Male bony fishes have two testes of equal size. Ovaries in bony fishes have features common to all vertebrates. They have  follicular cells and tunica albuginea.

Kidney: Kidneys of bony fishes are narrow and elongated organs which occupy a significant portion of the trunk. Kidneys have  clusters of nephrons.

Heart: They have a two-chambered heart. Heart contains one atrium for receiving of blood and one ventricle for pumping it.