Anatomy of frog Questions in English

(D) During hibernation,the metabolic rate of a frog is at its minimum,and the oxygen $({O_2})$ requirement is significantly reduced.
In this state,the frog performs cutaneous respiration,which means it absorbs oxygen directly through its moist skin.

(D) Frogs are amphibians,meaning they live both on land and in water. One of the primary reasons they stay in or near water is that they respire through their skin (cutaneous respiration). For this process to be efficient,the skin must remain moist at all times. Water provides the necessary environment to prevent the skin from drying out,allowing for continuous gas exchange.

(B) In frogs,the ear is represented by a tympanum,which is an external membrane that receives sound vibrations. Unlike mammals,frogs do not possess an external ear structure known as a pinna (or auricle). Therefore,the correct statement is that a frog has ears but no pinnae.

(A) Frogs belong to the phylum $Chordata$.
In the animal kingdom,the coelom is classified based on its embryonic origin.
$Enterocoel$ is a type of coelom that develops from the pouches of the embryonic gut $(archenteron)$.
This type of coelom is characteristic of $Deuterostomes$,which include $Echinodermata$,$Hemichordata$,and $Chordata$ (including frogs).
Therefore,the correct answer is $Enterocoel$.

(A) Frogs are poikilothermic or cold-blooded animals,meaning their body temperature fluctuates with the ambient temperature.
To survive extreme environmental conditions,they undergo two types of dormancy:
$1$. Hibernation: Also known as 'winter sleep',it occurs during the winter season to protect the animal from extreme cold.
$2$. Aestivation: Also known as 'summer sleep',it occurs during the summer season to protect the animal from extreme heat and desiccation.
Therefore,frogs hibernate during the winter.

(C) The dissection of a frog is performed from the ventral side primarily because the vertebral column,which is the main skeletal support,is located on the dorsal side. By cutting through the ventral side,the internal organs can be accessed without damaging the spinal cord or the vertebral column. Additionally,the ventral skin is relatively soft and easier to incise compared to the dorsal side.

(A) Croaking is a characteristic sound produced by frogs,primarily during the breeding season to attract mates.
Male frogs can croak much louder than females because they possess a pair of vocal sacs located on the floor of the mouth (throat region).
These vocal sacs act as resonators,which amplify the sound produced by the vocal cords,allowing the male to produce a louder call.

(B) The correct answer is $B$.
In frogs,the rectum opens into a common chamber known as the $Cloaca$.
The $Cloaca$ serves as a common opening for the digestive tract (rectum),the urinary system (ureters and urinary bladder),and the reproductive system (oviducts in females).
This chamber eventually opens to the exterior of the body through a single opening called the $cloacal$ $aperture$.

(B) The hindlimb of a frog consists of a thigh,shank,and foot. The foot of the hindlimb is composed of tarsals,metatarsals,and phalanges. There are $5$ digits (fingers/toes) present in the hindlimb of a frog,which are webbed to assist in swimming.

(B) In the buccal cavity of a frog,a pair of internal nares is present.
These are in the form of two small openings located on the roof of the buccal cavity,lying outer to the vomerine teeth.

(C) The coloration in frogs and other amphibians is primarily due to the presence of specialized pigment-containing cells in the dermis known as $Chromatophores$.
These cells are categorized into three main types:
$1$. $Lipophores$ (containing yellow or red pigments),
$2$. $Melanophores$ (containing black or brown melanin pigment),and
$3$. $Iridocytes$ (containing reflective crystals that produce iridescent colors).
Therefore,the correct option is $(C)$.

(D) The skin of a frog consists of two main layers: the epidermis and the dermis.
In the dermis,there are two distinct layers: the outer stratum spongiosum and the inner stratum compactum.
The stratum spongiosum is a loose connective tissue layer located just beneath the epidermis (stratum germinativum).
This layer contains numerous scattered pigment cells known as chromatophores,which are responsible for the skin color of the frog.
Therefore,the correct option is $D$.

(A) The skin of a frog is moist,slimy,and highly vascular,which provides an extensive surface area for the exchange of respiratory gases. This process is known as cutaneous respiration. Frogs respire through their skin both in water and on land,making it a primary respiratory organ.

(C) The correct answer is $C$. The tongue of a frog is large,muscular,and sticky. It is bilobed at the tip and attached at the front,while being free from behind. This specialized structure allows the frog to rapidly flick its tongue out to capture prey.

(D) In a frog,the tongue is bifid and muscular.
It is attached to the floor of the buccal cavity anteriorly.
The posterior end of the tongue is free and can be protruded to catch prey.
The base of the tongue is attached to the $Hyoid$ $apparatus$,which provides support and allows for the rapid flicking movement of the tongue.

(D) The teeth of a frog are $Acrodont$,$Homodont$,and $Polyphyodont$.
$1$. $Acrodont$: Teeth are attached to the surface of the jaw bone without a socket.
$2$. $Homodont$: All teeth are similar in shape and size.
$3$. $Polyphyodont$: Teeth are replaced multiple times throughout the life of the organism.
These teeth are small,sharp,and backwardly directed,which are not meant for mastication but for preventing the escape of prey.

(D) The stomach of a frog is divided into a larger anterior cardiac part and a smaller posterior pyloric part.
The pyloric part of the stomach is separated from the duodenum by a muscular constriction known as the pyloric sphincter.
This sphincter regulates the passage of partially digested food (chyme) from the stomach into the duodenum.

(C) In frogs,the digestion of fats primarily takes place in the $Duodenum$. The $Duodenum$ receives bile from the gallbladder and pancreatic juice from the pancreas. Bile salts emulsify fats,breaking them down into smaller droplets,while the pancreatic lipase enzyme acts on these emulsified fats to digest them into fatty acids and glycerol.

(C) The frog is a positive pressure breather.
It fills its lungs by forcing air into them using its buccal cavity. For this mechanism to function,the mouth must be kept closed to create the necessary pressure. If the mouth is held open,the frog cannot force air into its lungs,leading to suffocation and death.

(B) In frogs,cutaneous respiration (respiration through the skin) occurs in water,during hibernation,and during aestivation. The skin is kept moist by mucus,which allows for the diffusion of gases.

(D) In a frog,the glottis is a slit-like opening that leads to the lungs.
It is situated on the floor of the pharynx.
The opening and closing of the glottis are regulated by the muscles attached to the arytenoid cartilages.
These cartilages provide structural support and facilitate the movement required for respiration and vocalization.

(B) The lungs of a frog are two delicate,elastic,pinkish,ovoid,thin-walled,hollow sacs situated on either side of the oesophagus in the upper part of the trunk region (thorax). These structures are adapted for pulmonary respiration.

(D) Frogs exhibit cutaneous,pulmonary,and buccopharyngeal respiration.
$1$. Cutaneous respiration: Respiration through the moist skin,which occurs both in water and on land.
$2$. Pulmonary respiration: Respiration through lungs,which occurs primarily on land.
$3$. Buccopharyngeal respiration: Respiration through the lining of the buccopharyngeal cavity.
Therefore,all these methods are used by frogs for respiration.

(B) The correct answer is $B$. In frogs,the skin serves as an accessory organ of respiration,a process known as cutaneous respiration.
The skin of a frog is thin,moist,and richly supplied with blood capillaries,which allows for the efficient exchange of gases between the environment and the blood.
This mechanism is particularly important when the frog is underwater or hibernating,as it supplements the primary respiratory function of the lungs.

(A) In frogs,cutaneous respiration occurs through the skin and takes place at all times,both on land and in water.
During hibernation (winter sleep) and aestivation (summer sleep),cutaneous respiration is the only method of respiration used by the frog.

(B) In vertebrates,including frogs,the respiratory system develops from the embryonic endoderm. The epithelial lining of the lungs and the entire respiratory tract is derived from the endodermal germ layer during embryonic development. Therefore,the correct option is $B$.

(C) The heart of a frog is $3$-chambered, consisting of two atria and one ventricle.
In contrast, the human heart is $4$-chambered, consisting of two atria and two ventricles.
$A$ key anatomical difference is that the frog's heart possesses a $Sinus venosus$, a large triangular chamber that receives blood from the major veins before it enters the right atrium.
Humans do not have a $Sinus venosus$ in their adult heart; instead, the veins open directly into the right atrium.

(A) The sinus venosus is a large,thin-walled,triangular chamber.
It is attached to the dorsal surface of the heart.
It receives deoxygenated blood from the body through the major veins (vena cava) and opens into the right atrium.

(A) Chordae tendinae are strong,fibrous,and elastic cords that connect the atrioventricular valves to the papillary muscles located on the inner wall of the ventricle. These structures prevent the valves from prolapsing into the auricles during ventricular contraction.

(A) The heart of a frog is a muscular organ situated in the upper part of the body cavity. It consists of three chambers: two auricles (atria) and one ventricle. Additionally,it is covered by a membrane called the pericardium. $A$ triangular structure called the sinus venosus joins the right auricle and receives blood from the major veins. Therefore,the primary chambers of the heart are two auricles and one ventricle.

(A) The heart of a frog is myogenic,meaning the heartbeat originates from the specialized muscle tissue within the heart itself. Under normal physiological conditions,the heart of a frog beats at an average rate of approximately $64$ times per minute.

(A) In the circulatory system of a frog,the vein that collects deoxygenated blood from the tongue is known as the $Lingual$ vein.
This vein eventually drains into the external jugular vein,which contributes to the formation of the precaval vein.

(B) In frogs,the venous system includes the renal portal system. The sciatic vein,which drains blood from the hind limbs,enters the kidney to form the renal portal system. Therefore,the sciatic vein opens into the kidney.

(C) The correct answer is $C$. The dorsolumbar vein is responsible for collecting venous blood from the skin and muscles of the lumbar (back) region in a frog and transporting it towards the heart or the systemic circulation.

(C) In frogs,there are two pairs of lymph hearts that help in the circulation of lymph.
The first pair of lymph hearts is situated anteriorly,just below the scapulae,and these open into the subscapular veins.
The second pair of lymph hearts is located posteriorly,on either side of the tip of the urostyle,and these open into the femoral veins.
Therefore,the first pair pumps lymph into the subscapular veins.

(C) The main excretory organs in a frog are a pair of mesonephric kidneys. These are compact,dark red,and bean-shaped structures situated posteriorly in the body cavity on both sides of the vertebral column.

(D) The kidneys in adult frogs are of the $Mesonephros$ type.
These kidneys develop from the middle part of the nephrotome,known as the mesonephros.
They are compact,dark red,and bean-shaped structures situated posteriorly in the body cavity on both sides of the vertebral column.
In contrast,$Pronephros$ are found in larval stages,and $Metanephros$ are characteristic of higher vertebrates like reptiles,birds,and mammals.

(B) In frogs,the kidneys are compact,dark red,and bean-shaped structures situated a little posteriorly in the body cavity on both sides of the vertebral column. On the ventral surface of each kidney,there are ciliated funnels known as $Nephrostomes$. These structures are associated with the excretion of waste products from the coelomic fluid.

(C) The urinary bladder of a frog is a thin-walled,transparent,and highly distensible bilobed sac. It is located ventral to the rectum and opens into the cloaca.

(D) In frogs,the urinary bladder is a thin-walled,bilobed sac located ventral to the rectum.
It stores urine temporarily.
The urinary bladder opens into the cloaca,which is a common chamber for the digestive,reproductive,and urinary tracts.
Therefore,the correct option is $D$.

(A) The thin roof of the cerebrum (telencephalon) in a frog is known as the pallium.
In the frog's brain,the cerebral hemispheres contain lateral ventricles called paracoels. The dorsal wall or roof of these paracoels is thin and is referred to as the pallium.

(D) The brain cavities (ventricles) of a frog include the $Diocoel$ (in the diencephalon),$Iter$ (in the midbrain),and $Metacoel$ (in the medulla oblongata),all of which are median (midline) structures.
$Optocoels$ are paired cavities located within the optic lobes of the midbrain. Since they exist as a pair (one in each optic lobe),they are not considered median parts.

(A) The second cranial nerve of the frog is the $Optic$ nerve.
It is a sensory nerve that transmits visual impulses from the eye to the brain.
Therefore,the correct option is $A$.

(A) The second cranial nerve is the optic nerve.
In frogs,as in other vertebrates,the optic nerve arises from the retina of the eye and carries visual information to the brain.
Therefore,it is specifically associated with the retina.

(D) The ninth cranial nerve of a frog is the Glossopharyngeal nerve $(IX)$.
It supplies the taste buds of the tongue and the muscles of the pharynx.
Some fibers carry sensory impulses from the tongue,while other fibers are responsible for pharyngeal movement,as they are involved in the swallowing reflex.

(B) The number of spinal nerves is specific to each group of animals. In frogs,the spinal cord gives rise to $10$ pairs of spinal nerves that emerge from the vertebral column.

(C) In frogs,the nervous system utilizes both acetylcholine and noradrenaline as neurotransmitters to facilitate signal transmission across synapses.
Acetylcholine is primarily associated with the parasympathetic nervous system and neuromuscular junctions.
Noradrenaline is primarily associated with the sympathetic nervous system.
Therefore,both substances play a crucial role in the chemical signaling of the frog's nervous system.

(B) The sclerotic (or sclera) is the outermost,tough,opaque,and protective layer of the eyeball. In frogs,as in most vertebrates,it is fibrous in nature,composed primarily of dense connective tissue.

(A) In frogs,the external ear or pinna is absent.
Instead,they possess a tympanum which represents the ear externally.
The presence of an external ear or pinna is a characteristic feature of mammals.

(D) Frogs possess eyes with eyelids to protect them from the environment.
They have teeth on their upper jaw (maxillary teeth) and vomerine teeth.
Frogs have digits (fingers) on their forelimbs.
Frogs do not have external ears or pinnae; instead,they have a tympanum that acts as an eardrum to receive sound vibrations.