Frog 2 Flashcards
explain the endocrine system
The system for control and coordination is highly evolved in the frog. It
includes both neural system and endocrine glands. The chemical
coordination of various organs of the body is
achieved by hormones which are secreted by the
endocrine glands. The prominent endocrine
glands found in frog are pituitary, thyroid,
parathyroid, thymus, pineal body, pancreatic
islets, adrenals and gonads.
explain nervous system
The nervous system
is organised into a central nervous system (brain
and spinal cord), a peripheral nervous system
(cranial and spinal nerves) and an autonomic
nervous system (sympathetic and
parasympathetic). There are ten pairs of cranial
nerves arising from the brain. Brain is enclosed
in a bony structure called brain box (cranium).
The brain is divided into fore-brain, mid-brain
and hind-brain. Forebrain includes olfactory
lobes, paired cerebral hemispheres and unpaired
diencephalon. The midbrain is characterised by
a pair of optic lobes. Hind-brain consists of
cerebellum and medulla oblongata. The medulla
oblongata passes out through the foramen
magnum and continues into spinal cord, which
is enclosed in the vertebral column.
explain frog sense organs
Frog has different types of sense organs, namely
organs of touch (sensory papillae), taste (taste
buds), smell (nasal epithelium), vision (eyes) and
hearing (tympanum with internal ears). Out of
these, eyes and internal ears are well-organised
structures and the rest are cellular aggregations
around nerve endings. Eyes in a frog are a pair of
spherical structures situated in the orbit in skull.
These are simple eyes (possessing only one unit).
External ear is absent in frogs and only tympanum
can be seen externally. The ear is an organ of
hearing as well as balancing (equilibrium).
explain male reproductive system
Male reproductive organs
consist of a pair of yellowish ovoid testes (Figure
7.3), which are found adhered to the upper part
of kidneys by a double fold of peritoneum called
mesorchium. Vasa efferentia are 10-12 in
number that arise from testes. They enter the
kidneys on their side and open into Bidder’s canal. Finally it communicates with the urinogenital duct that comes out
of the kidneys and opens into the cloaca.
what is cloaca
. The cloaca is a small, median
chamber that is used to pass faecal matter, urine and sperms to the exterior
explain female reproductive system
The female reproductive organs include a pair of ovaries (Figure 7.4).
The ovaries are situated near kidneys and there is no functional connection
with kidneys. A pair of oviduct arising from the ovaries opens into the
cloaca separately. A mature female can lay 2500 to 3000 ova at a time.
Fertilisation is external and takes place in water. Development involves a
larval stage called tadpole. Tadpole undergoes metamorphosis to form
the adult.
economic importance of frog
Frogs are beneficial for mankind because they eat insects and protect
the crop. Frogs maintain ecological balance because these serve as an
important link of food chain and food web in the ecosystem. In some
countries the muscular legs of frog are used as food by man.
