Dogfish Shark (External Morphology And Musculoskeletal System)

Front 1

Head

Back 1

extends posteriorly to the end of the pharyngeal slits and includes the laterally placed eyes

Front 2

Spiracle

Back 2

openings on the head, allow water to pass through the gills even when the sharks mouth is closed

Front 3

External gill slit

Back 3

allows water to move through gills for oxygen

there are 5 gill slits

Front 4

Pectoral fin

Back 4

Large paired fins lie anteriorly, slightly behind the gill slits on the ventral side

Front 5

Dorsal fins

Back 5

Lies mid way on the trunk and carries a sharp spine anteriorly

Front 6

Denticles

Back 6

aka Placoid scales these are embedded into the skin of the shark and covered in enamel containing a pulp cavity; no dentine

Front 7

Spines

Back 7

Found on the anterior and posterior dorsal fins

Front 8

Labial fold

Back 8

supported by the labial cartilage

Front 9

Labial pocket (pouch)

Back 9

these lie on either side of the mouth looks like little laugh lines

Front 10

Nares (sing. naris)

Back 10

these lie ventrolaterally on the snout and are divided into two by a flap of skin divides into incurrent and excurrent apertures leads into blind–ended olfcatory sac

Front 11

Olfactory sacs

Back 11

Two large bulbous nerve sensors that detect chemicals in the surrounding water.

Front 12

Abdominal pores

Back 12

one found on each side just past the cloaca on the lateral side these pores extend into the pleuroperitoneal cavity and may allow excess fluids to be removed from the cavity.

Front 13

Claspers

Back 13

found only in males, found dorsally between the pelvic fin and cloaca grooved clasper can elongate; used in copulation

Front 14

Caudal fin

Back 14

carried dorsally by the tail extending from cloaca

Front 15

Pectoral girdle

Back 15

attachment site for fins, a stout, U–shaped cartilage

Front 16

Coracoid bar

Back 16

part of the pectoral girdle found inbetween each fin

Front 17

Pseudobranch

Back 17

a reduced first gill arch reason gill arches are named 2–5

Front 18

Ampullae of Lorenzini

Back 18

electroreceptors found in pores in the underside of the head and snout

Front 19

Lateral line canal

Back 19

a tube containing sensory nerve endings which leads into the opening of pores these sensory cells respond to pressure changes caused by vibrations in the water

Front 20

Ischiopubic bar aka puboischiadic bar

Back 20

makes up the pelvic girdle

Front 21

Chondrocranium

Back 21

the head skeleton of a dogfish shark

Front 22

Rostrum

Back 22

scoop–like part on the anterior side of the chondrocranium

Front 23

Basal plate

Back 23

flattened ventral part of chondrocranium refer to a diagram

Front 24

Olfactory capsules (or bulbs)

Back 24

2 bulgy balls that protrude anteriorly from the brain refer to a diagram

Front 25

Orbit

Back 25

the area which houses the eyeball found in the chondrocranium

Front 26

Postorbital process

Back 26

projects ventrally from the posterior side of the orbit post: after

Front 27

Supraorbital crest

Back 27

found dorsally and posteriorly from the orbit refer to a diagram supra: above

Front 28

Otic capsules

Back 28

houses the inner ears found behind the orbit refer to a diagram ot: ear

Front 29

Vertebral Column

Back 29

extends from the chondrocranium to the tail supports all the dorsal fins and caudal fin

Front 30

Neural canal

Back 30

spinal cord canal found on the dorsal side of the spine (above the centra)

Front 31

Neural arch

Back 31

the arch which surrounds the neural canal above the centra

Front 32

Centrum (sing. centra)

Back 32

hourglass–shaped vertebral body of the vertebral column located in the middle of the neural arch and hemal arch

Front 33

Hemal arch

Back 33

a plate of cartilage that forms the arch around the hemal canal

Front 34

Hemal canal

Back 34

arteries and veins that lead to the caudal side of the shark passes through the hemal arch

Front 35

Visceral arches

Back 35

the sum of seven arches found on the splanchocranium mandibular arch hyoid arch and five brancial arches

Front 36

Gill arch (or branchial arch)

Back 36

each arch supports a gill anterior side should be visible

Front 37

Gill rakers

Back 37

these project from each slit helps food escaping or damaging gills refer to a diagram

Front 38

Gill ray

Back 38

cartilage that extend from the branchial arch and support the interbranchial muscle

Front 39

Gill lamellae

Back 39

not preserved on skeleton as it is not composed of cartilage where gas exchange occurs in the gills

Front 40

Mandibular arch

Back 40

largest of the visceral arches forms the jaws

Front 41

Meckel's cartilage

Back 41

the ventral side of the mandibular arch is made up of a pair of Meckel's cartilages

Front 42

Palatopterygoqudrate (or palatoqudrate) cartilage

Back 42

found inbetween the orbital process on the anterior side and the adductor mandibulae process posterialy

Front 43

Hyoid arch

Back 43

these are modified to support the mandibular arch

Front 44

Hyomandibular cartilage

Back 44

found on the dorsal segment of the hyoid arch on each side