Comparative anatomy of heart structure

 

Comparative anatomy of heart structure

1.      All chordates have a circulatory or vascular system comprising a system of vessels and channels through which 2 kinds of fluids travel in separate, yet interconnected vessels. The fluids are the blood and the lymph

2.     The blood vascular system is a closed system in vertebrates.  It has a contractile heart and continuous tube called vessels.

3.      Heart is a hollow muscular pumping organ, It is conical in shape.  Heart is always ventral to the gut, lying in a specialized coelomic compartment, the pericardium.

4.      Vertebrates have a pulsating heart  It receives blood from various parts of the body at the posterior end by means of veins and pumps it into arteries at the anterior end, which carry the blood to various organs including the breathing organs.

The heart of (Fish ) Shark

.     The heart of shark has only two chambers, namely an auricle and a ventricle.

2.     On the dorsal side of the auricle there is a sac-like sinous which receives blood from all parts of the body.

3.     This opens into the auricle by an aperture.

4.     Auricle communicate with the ventricle.

5.     Ventricle is continued ventrally and forward by another swollen part called conus arteriosus.

6.     Conus extend forward as ventral aorta

7.     Heart of shark deals with only deoxygenated blood (Venous heart)

8.     The circulation is single circulation

The heart of frog

                                

1.     The heart of frog has 2 auricles and one ventricle.

2.     Auricles are seperted by an interauricular septum.

3.     Sinus venosus on the dorsal side, opens into the right auricle through sinu- auricular aperature.

4.     Left auricle contains - oxygenated blood.

5.     The 2 auricles open into the ventricle by a common aperature which is guarded by the auriculo-ventricular valve.

The heart of reptiles

1.     The heart of reptiles show improvement over the amphibians.

2.     The heart of reptile is of incomplete 4 chambers.

3.     Sinus venosus merged with the right auricle.

4.     Right and left auricles are completely seperated by interauricular septum.

5.     The ventricle is also divided imperfectly into two halves.

6.     Conus split upto the base into 2 vessels namely, pulmnory artery and aorta, that cross each other.

Heart of Bird/ Mammal

1.     The first land vertebrates to have achieved complete separation of pulmnory and systemic circulation.

2.     Heart- large and 4 –chambered,

3.     Sinus venosus and conus are absent.

4.     Right auricle - deoxygenated blood, 2 postcaval and 1 precaval vein

5.     Left auricle contains  oxygenated blood  and opening of  pulmnory vein.

6.     Right auricle opens into Right ventricle  by monocuspid valve.

7.     Left auricle open into Left ventricle  by bicuspid valve.

8.     Heart- 4 chambered, completely divided auricle and ventricle.

9.     Right auricle opens into Right ventricle  by tricuspid valve.

10.                        Left auricle opens into Left ventricle  by bicuspid valve.

11.                        Wall of heart supplied by coronary arteries.

12.                        Thus, the well defined circulatory system helps in complete separation pulmnory and systemic circulation and the complex nature of the heart anatomy,

13.                        The circulation is double.

In bird Right systemic is present 

Inner ear of scoliodon or Membranus labrynth

 Procedure. 

1. The internal ear of the membranous labyrinth lies in the auditor capsule just behind the orbit on either side. The auditory capsules are seen as bulgings on either side. 
2. Remove the skin over the auditory capsule. Careful observation shows ridges of anterior vertical, horizontal, and posterior vertical semicircular canals. 
3. The cartilage capsule can be gently broken by forceps. 
4. Take care not to injure the canals of the membranous labyrinth. 
5. Locate the vertical canals and proceed. 
6. The internal ear consists of the anterior vertical canal, posterior vertical canal, horizontal canal. ampullae of the anterior vertical canal, horizontal canal and posterior vertical canal, lagena cochlea, recesses utriculi, utriculus, and nerve supplies. 

The internal ear

It lies in the auditory capsule of the skull. It is useful for the maintenance of equilibrium. In the fish external and middle ears are absent. Internal eats covered by the cartilaginous labyrinth. Space is present between membranous and labyrinth is filled with perilymph.

 The membranous labyrinth shows laterally compressed sac. It is divided into utriculus and sacculus. At the end of the sacculus, lagena is present.

 The internal ear shows 3 semi circular canals.

1.  Anterior vertical semicircular canal.
2. Posterior vertical semicircular canal.
3. Horizontal semicircular canal.

 These semicircular canals end with ampullae.

 From the dorsal side of the internal ear duct arises. This is called saccus endolymphaticus. 

It opens out on the skin.

 In the ampullae sensory patches are present, they will be acoustic in nature, in the utriculus and sacculus  are present. They are mainly useful for the maintenance of balance. Thus the internal ear is useful for caring and maintenance of balance.

Eye muscles of scoliodon

Procedure. 

Remove the eyelids and nictitating membrane to expose the eye-ball and its muscles. 

The eye muscles are inserted into the eye-ball in two groups. 

Note the following six eye muscles : 

(1) Superior rectu~. Inserted on the dorsal surface of the eye-ball. 

(2) Inferior rectus. Inserted on the ventral surface of the eye-ball. 

(3) Anterior rectus. Inserted on the antt'rior surface of the eye-ball. 

(4) Posterior rectus. Inserted on the posterior surface of the: eye-ball. 

(5) Superior oblique. Inserted on the dorsal surface of the eye-ball. 

(6) Inferior oblique. Inserted on the ventral surface of eye-ball. Optic peduncle. It is a cartilaginous stalk holding eye in the orbit. 

Cranial nerve of scoliodon

Cranial Nerve of Scoliodon

            

There are ten pairs of cranial nerves in all the fishes.

 

Olfactory nerves:

The first pair of cranial nerves is the olfactory nerves which originate from the olfactory lobes and innervate the olfactory sacs. The terminal nerves are situated between the two olfac­tory lobes. These nerves emerge from the telencephalon and bear a ganglion called ganglion terminale near the origin.

These nerves supply the nasal septum and the external nostril.

 

Optic nerves

The second pair of cranial nerves is the optic nerves which, after the origin from the optic thalami, form the optic chiasma and supply the eyes.

 

Oculomotor nerve

The third cra­nial nerve is called oculomotor nerve which originates from the ventral surface of the mesencephalon and supplies the anterior, superior and inferior recti and the inferior oblique muscles of each eye ball.

 

Trochlear or pathetic:  

The fourth cranial nerve is called trochlear or pathetic nerve which arises from the dorsolateral surface of the midbrain and supplies the superior oblique eye muscle.

 

Trigeminal  

The fifth cranial nerve is the trigeminal which has three branches:

 

(1) Ophthalmicus superfi­cial which supplies to the skin of the snout.

 (2) The maxillaris which is divided into maxillaris superior supplying nerves to the skin of the upper jaw and maxillaris inferior inner­vating the posterior part of the upper jaw.

 (3) The mandibularis innervating the muscles of the lower jaw. Another nerve called ophthalmicus pro-fundus becomes secondarily associated with the trigeminal to supply nerves to the eye ball and the dorsal surface of the snout

 

Abducens:

The sixth cranial nerve is the abducens which supplies the posterior rectus muscle of the eye ball. The seventh cra­nial nerve is known as facial which divides into two branches:

 

(1) The ophthalmicus superficialis branch like that of the fifth cra­nial nerve.

 (2) A bundle of mixed nerves which subdivides into three routes:

 (a) A ramus buccalis innervating the infraorbital canal of the snout.

  (b) A ramus hyomandibularis supplying nerves to the lower jaw and throat.

 (c) A ramus palatinus giving nerve supply to the roof of the buccal cavity and the pharynx. The eighth cranial nerve is called auditory which gives the vestibular and saccular branches to the internal ear.

 

Glosso­pharyngeal:

The ninth cranial nerve is the glosso­pharyngeal which, in the region of the first gill cleft, divides into a small pretrematic nerve and a large posttrematic nerve. These nerves supply branches to the pharynx, pha­ryngeal muscles and the mucous membrane surrounding the first gill slit.

 

Vagus

The tenth cranial nerve is the vagus which arises by multiple roots and gives off many branches.

The branches are:

(i) the brachial nerves sup­plying the gills,

(ii) the lateralis supplying the lateral line sense organs and gives nume­rous branches along its course.

 

Spinal nerves:

(a) Ramus dorsalis,

(b) Ramus ventralis, and

(c) Ramus communicans to join with the autonomous nervous system.

 

 

 

Name of the nerve	Origin	Branches	Distribution	Physiological Nature
1. Olfactory	Olfactory lobe.	-	Olfactory epithelium of the nasal cavity.	Sensory
2. Optic	Optic lobe.	-	Retina of eye.	Sensory
3. Oculomotor	Ventrolateral side ofthe midbrain.	-	Anterior rectus, superior rectus, inferior rectus and inferior oblique muscles of the eye. Superior oblique muscle of the eye	Motor Motor
4. Trochlear	Dorsolateral aspect of the midbrain between the optic lobes and cerebrum.	-	Olfactory capsule and dorsal	Mixed
5. Trigeminal	Dorsally from the side of medulla oblongata below the corpora restiformes.	(i) Opthalmic profundus  (ii) Ophthalmicus superfi-cialis V  (iii) Maxillaris V (a) Superior (b) Inferior (iv) Mandibularis	skin of the snout. Skin of the snout. Skin of upper jaw Posterior part of upper lip. Muscles of the lower jaw.	Mixed Motor Mixed
6. Abducens	Midventrally from the floor of medulla oblongata	-	Posterior rectus muscle of the eye.	Mixed
7. Facial	From the side of medulla below the corpora restiformes in the form of a bundle.	(i)                   Opthalmicus super-ficialis VII   Ii Ramus buccalis (iii) Flyomandibularis (a)     Mandibularis externus (b) Mandibularis internus (c) Hyoidean (iv) Ramus palatinus	Sense organs; the lateral line system of snout. Infra-orbital lateral line canal and associated ampullae. Mandibular canal of lateral-line system. Mucous membrane of the floor of buccal cavity. Muscles of the roof of buccal cavity and pharynx. Roof of the pharyngeal and buccal cavity.	Mixed Mixed Mixed Mixed Mixed Sensory
8. Auditory	From the side of medulla close to the V and Vll cranial nerves.	(i) Vestibular (ii) Saccular	Membranous labyrinth of the internal ear	Sensory
9. Glossopharyn geal	From the ventro-lateral side of medulla.	(i) Pre-trematic (ii) Post-trematic	Mucous membrane of the first gill-cleft and the pharynx. The muscles of the pharynx Gills.	Sensory Mixed Mixed
10. Vagus	Side of Medulla.	(a) Branchialis (b) Visceralis (c) Lateralis	Viscera. Lateral-line system of the trunk.	Mixed Mixed Mixed

Study of gills of fishes:

 

Study of gills of fishes:

The presence of the gills is one of the most important characteristics of the fishes.  In fishes, gills are respiratory organs. Through gills intake of dissolved oxygen from water and removal of carbon dioxide through body along with out going water is taking place.  The structure of gill is different in cartilaginous fish and bony fish.

  

Filiform gill: Gills of bony fish : (Ex. Labeo)

1.     In bony fishes there are four pairs of complete gills. They are called as holobranch. 

2.     Gills are located on either side of the pharynx in branchial chamber.

3.     In bony fishes gill is filamentous (Filiform).

4.     The inter-branchial septum is greatly reduced due to that gill filaments hangs freely in the branchial chamber or gill chamber. Hence such types of gills are called as filliform gills or pectinate type of gills.

5.     The branchial chamber opens outside by wide opening lies between pectoral fin and operculum.

6.     Each gill is highly vascular, richly supplied with blood vessel and shows several transverse primary and secondary gill lamellae. 

7.     Exchange of gases is take place through gill.

 

 

Lamelliform gill: Gills of cartilaginous fishes: (Ex. Scoliodon)

1.     In cartilaginous fishes there are five pairs of gills.

2.     Gills are situated in gill pouches on either side of the pharynx.

3.     Gills are separated from each other by well-developed inter-branchial septum.

4.     Inter-branchial septum is supported by cartilaginous gill ray.

5.     In cartilaginous fishes gills are lamelliform.

6.     First pair of gills consist of single gill lamella attached to the posterior side of hyoid arch and called as half gill or hemibranch or demibranch.

7.     Remaining gills consist of two-gill lamellae and called as complete gill or holobranch.

8.     The gill pouches open outside by narrow transverse gill slits.

9.     The mucus membrane of gill pouch is raised upward into leaf-like folds called as gill lamellae.

10.                        In gill lamella diffusion of O2 and Co2 is occurs.