Venous system
* Sinus venosus is formed by the union of two precavals/anterior or superior venacavae and post
* caval/posterior or inferior venacava
* Pre caval is formed by:
i)External jugular vein that collects blood from the muscles of torgue and jaws
ii) Innominate vein that collects blood from orbit, brain and shoulder region.
iii) Subclavian vein which collects blood from the muscles of forelimbs and skin.
* Postcaval vein originates from the capillaries of kidneys and also collects blood from gonads and liver.
* Blood from the lungs is collected by pulmonary veins which open into left atrium as a common pulmonary vein
* Hepatic portal vein collects blood from alimentary canal, pancreas and releases into liver.
* Renal portal vein collects blood from lower parts of body and release them into kidneys.
* Blood of frog consists of plasma, eryth rocytes, leucocytes and thrombocytes.
* RBC are oval, nucleated & relatively larger in size
* Lymphatic system- consists of lymph capillaries, lymph vessels, lymphatic ducts, and hymph nodes.
* Lymph hearts are 2 pairs helping in pumping the lymph into veins.
* Integrating system-consists of nervous and endocrine systems.
* Nervous system includes central ner vous system (brain & spinal cord), peripheral nervous system (cranial nerves & spinal nerves) autonomous nervous system(sympathetic & para sympathetic)
* Brain- consists of forebrain (or prosencephalon), midbrain(or mesencep halon) and hind brain (or rhom bencephalon).
* Fore brain consists of a pair of olfactory lobes, a pair of cerebral hemispheres and diencephalon.
* Rhinocoels are ventricles of olfactory lobes.
* Para coels or lateral ventricles (1st and 2nd) are enclosed by cerebral hemispheres.
* Cerebral hemispheres control voluntary actions
* Dience phalon is concerned with per ception of heat, cold, pain and integ rity of autonomous nervous system.
* Diocoel (3rd ventricle) is enclosed by diencephalon
* Mid brain consists of a pair of hollow optic lobes (corpora bigemina) enclosing optocoels.
* Optic lobes control vision.
* Hind brain consists of cerebellum (maintains equilibrium) and medulla oblongata (controls involun tary actions
* Fourth vertricle is enclosed by medulla
* Spinal cord is continuation of medulla.
* Spinal cord acts as middle man between brain and effectors.
* 10 pairs of cranial nerves and 9 or 10 pairs of spinal nerves are present.
Sense organs:
* Eyes-Retina contains rods for dimlight vision and cones for color vision.
* Organs of hearing : Middle ear & internal ear are present
* Columella auris, the middle earossicle, meets the cartilaginous stapedial plate which fuses with fenestra ovalis of anditory capsule.
* Auditory capsule is formed by single prootic bone
* Internal ear/ membranous labyrinth consists of dorsal utriculus to which the 3 semicircular canals join and ventral sacculus.
* Auditory capsule is filled by perilymph and internal ear is filled by endolymph in which calcium carbonate particles, otoliths, are present
* Internal ears are also called statoacoustic organs
Excretory system:
* Frogs are ureotelic
* Mesonephric kidneys with ciliated nephrostomes on ventral surface are present in adults
* Tadpole larva of frog has pronephric kidneys
* Ureter/mesonephric duct/Wolffian duct arises from the outer margin of kidney and open into cloacal chamber.
* In males, as ureters carry both urine and sperms, they are called urinogenital ducts
* Urinary bladder opens separately into cloaca below the openings of ureters
* Frogs excrete hypotonic urine
Male reprodutive system
* Testes are covered by mesorchium and attached to kidneys
* Vasa efferentia from each testis open into Bidder’s canal present in the kidney.
* Ureter acts vasdeferens
* Seminal vesicle is the swollen part of ureter just behind the kidney.
* Germinal epithelium is the lining of seminiferous tubules.
* Germinal epithelial cells undergo spermatogenesis
Female reproductive system
* Mesovarium is peritoneal covering by which ovaries are attached to kidneys.
* Eggs are mesolecithal and telotecithal
* Ova are released into body cavity
* Oviduct/Mullerian duct opens into the body cavity by ciliated oviducal funnel called ostium.
* Ovisacs are posterior dilated parts of the oviduct that open into cloacal chamber near the ureter.
* Copulation is called amplexus during which both male & female frogs release sperms and ova into the water
* Eggs released in large number called spawn and the spermatozoa released are called milt
* Fertilisation external
* Development includes a gill breathing, herbivorous, ammonotelic tadpole larva which metamor- phoses into lung breathing, carnivorous, ureotelic adult frog.
* Class: Reptilia
* First group of true terrestrial tetrapods
* Labyrinthodont amphibians are the ancestors of reptiles
* Evolved during carboniferous period
* Mesozoic era is the age of reptiles
* Poikilothermic (ectothermic) amnio tes which lay cleidoic eggs on land.
* Study of reptiles is called herpetology.
* Body divided into head, neck, trunk and tail with rough, dry skin covered by epidermal scales, shields etc.
* Two pairs of pentadactyl limbs with clawed digits
* Teeth homodont, acrodont, polyphyodon odont. Thecodont in crocodiles and edentate in chelonians
* Skull monocondylic with temporal fossae
* Each half of lowerjaw is made of six bones.
* Vertebrae procoelous; sacral vertebrae two in number
* Sternum broad plate like; ‘T’ shaped interclavicle present between the two clavicles.
* Inter costal muscles are associated with ribs
* Vascular cloaca helps in respiration in turtles
* Heart with incompletely divided ventricle (incompletely 4-chambered) but crocodiles have 4- chambered heart
* Sinus venosus present but conus arteriosus absent
* Three aortic arches- two systemics and one pulmonary arise directly from ventricle.
* Renal portal system present; RBC nucleated
* Kidneys metanephric; uricotelic vertebrates (terrestrial adaptation)
* 12 pairs of cranial nerves (10 pairs in snakes)
* Jacobson’s organs, olfactory in function, are well developed in lizards & snakes
* Males with copulatory organ (absent in Sphenodon)
* Mesonephric duct/ Wolffian duct acts as vasdeferens
* Cloaca 3 chambered with anterior coprodaeum, middle urodaeum and posterior proctodaeum,
* Fertilisation internal
* Eggs cleidoic, megalecithal & telolecithal
* Cleavage meroblastic and discoidal
}} Mostly oviparous; eggs develop on land as they are amniotes
}} Crocodilians are the largest living reptiles.
}} Extant reptiles are grouped under 4 orders
