Question

Name the different organs of respiration of scoliodon.

Answer 1

There are two types of gills:

(i) Holobranch or complete gill when a branchial arch bears two sets of gill lamellae and

(ii) Demi branch or hemi branch or half gill when single set of gill lamellae is present. The hyoid arch sup­ports only a demi branch and the first four branchial arches support holobranchs. The last branchial arch is gill-less.

Answer 2

hi freind
here is your answer

scolidion breathe in water and it breathes by the use of gills borne in a series of gill pouches on both aspect of the pharynx. Water enters the mouth and after passing via the buccal cavity, pharynx, gill-pouches and goes out via the gill slits after bathing the gills.

Organs for respiration in scolidion

There are total five pairs of lathral gill-pouches centered in the latheral walls of the pharynx and are organized in a sequence on their facet. Every gill-pouch is compressed anteroposteriorly and communicates with the cavity of the pharynx through a huge interior branchial aperture and with the exterior by means of a narrow external branchial aperture.

The endodermal mucous membrane of gill-pouches is raised in to a series of horizontal folds to type lamelliform branchial lamellae. The bbranchial lamellae have a wealthy blood supply, and they have an extraordinarily skinny masking membrance via which blood is uncovered to seawater for an exchange of gases.

Each one gill-pouch has two sets of gill-limellae is a half gill or hemi department, so that gill-pouch has two by using muscular interbranchial septa of connective tissue. The interbranchial septa lengthen well beyond the branchial lamellae, after which each bends posteriorly to defend the lamellae.

The interior part of each interbrachial septum has a assisting visceral arch from which cartilaginous gill rays come up in a single row and task into the interbranchial septum for additional support. Visceral arches additionally supply out rigid comb-like gill rackers, which challenge the internal branchial apertures from food.

Every visceral arch helps the posterior branchial lamellae or hemibranch of one gill-pouch and the anterior branchial lamellae, or hemibranch of the gill cleft at the back of it. These two hemibranches with their interbranchial septum and the visceral arch represent a whole gill or holobranch. The posterior hemibranch of every holobranch is higher than the anterior one.

Between the mandibular hyoid arches of each and every part is a spiracle. In most plasmobranches the spiracle bears branchial lamellae and opens to the exterior by using an external branchial aperture. It is offered with arterial blood and performs no section in respiration. However in scoliodon the spiracles are vestigial pits within the pharynx without a lamellae or outside branchial aperture. The hyoid arch bears only a hemibranch posteriorly. The first 4 branchial arches bear a holobranch each and every, the fifth braanchial arch has no branchial lamellae, and consequently scoliodon has nine hemibranches on each and every facet.

Mechanism of respiratory:

the ground of the buccopharyngeal cavity is despressed by hypobranchial muscle groups and the mouth is opened whilst the viscera arches increase the wall of the pharynx, in order that see-water containing dissolved oxygen rushes in by way of the mouth.

Entry of the water into outside brachial apertures is prevented by an anterior fold is then raised and the mouth is closed, and contractions of the wall of the pharynx force the water into inner branchial apertures, the oesophagus being closed, and then into gill lefts, where it washes the branchial lamellae and goes out of the outside branchial apertures.

In the branchial lamellae, the blood flows from the tip toward the bottom that's in a path reverse to that of the water current, so that the blood just earlier than leaving the jamellae meets the best possible concerntration of oxygen and the bottom of carbon dioxide takes location between the blood and seawater. The respiratory actions are caused by means of pharyngeal muscle tissues.