Anatomy of frog Questions in English

(D) The middle ear of a frog contains a single ear ossicle known as the $Columella \text{ } auris$.
Embryologically, the $Columella \text{ } auris$ of a frog is homologous to the $Stapes$ found in the middle ear of mammals.

(D) In frogs,the middle ear consists of the tympanic membrane and the columella auris. The middle ear communicates with the pharynx via the Eustachian tube. The $Fenestra$ $ovalis$ (also known as the oval window) is an opening in the auditory capsule that connects the middle ear to the internal ear. Therefore,option $D$ is the correct description.

(D) The color change in the skin of a frog is primarily mediated by chromatophores,which are pigment-containing cells.
These cells are regulated by both the nervous system (for rapid changes) and hormonal activity (specifically the Melanocyte Stimulating Hormone or $MSH$ from the pituitary gland for slower,long-term changes).
Therefore,the control of chromatophores involves both nervous and hormonal mechanisms.

(A) $Mesorchium$ is a thin fold of the peritoneum that suspends the testis from the ventral anterior part of the kidney in a frog.
It serves as a connective tissue bridge that holds the testes in place within the abdominal cavity.

(D) Bidder's canal is present in the kidney of male frog.
It is a longitudinal canal located in the inner margin of the kidney.
It receives sperms from the $vasa$ $efferentia$ and helps in the transport of sperms to the ureter.

(B) In the kidney of a male frog,the $Bidder's$ canal is a longitudinal duct located in the medial region of the kidney. It receives $vasa$ $efferentia$ from the testes,which carry spermatozoa. These spermatozoa then enter the $Bidder's$ canal and are transported to the $urinogenital$ duct. Therefore,the correct description is that it runs longitudinally in the medial region of the kidney.

(A) In male frogs,the ureters emerge from the kidneys and open into the cloaca.
They carry both urine and sperm,which is why they are referred to as urinogenital ducts.
In female frogs,the ureters and oviducts open separately into the cloaca,meaning the ureter only carries urine.

(B) In a frog,each egg is surrounded by a vitelline membrane (a primary egg membrane).
As the eggs pass through the oviduct,they are coated with layers of albumin and a thick,adhesive jelly.
This jelly is secreted by the glandular walls of the oviduct.
Therefore,the jelly layer is deposited while the eggs are moving through the oviduct.

(C) mature female frog is capable of laying a large number of eggs during the breeding season.
According to biological studies,a single female frog typically lays between $2500$ and $3000$ eggs at a time in a cluster known as spawn.
Therefore,the correct option is $C$.

(A) The pelvic girdle of a frog consists of three parts: ilium,ischium,and pubis.
In the frog,the pubis is not a true bone formed by ossification of cartilage; instead,it remains as a piece of hyaline cartilage that becomes calcified due to the deposition of calcium salts in its matrix.
Therefore,it is referred to as calcified cartilage.

(C) The correct answer is $C$. In frogs,the teeth are found on the premaxilla,maxilla,and the vomer bone. These are known as vomerine teeth,which help in preventing the prey from escaping.

(D) The teeth in a frog are $Acrodont$,meaning they are attached to the surface of the jaw bone without sockets.
They are $Homodont$,meaning all teeth are similar in shape and size.
They are $Polyphyodont$,meaning they are replaced multiple times throughout the life of the organism.
Therefore,all the given characteristics are correct for the teeth of a frog.

(A) The stomach of a rabbit is divided into three parts: cardiac,fundic,and pyloric. Therefore,the fundic part is present in the rabbit.
In contrast,the stomach of a frog is divided into only two parts: a large,broader anterior part called the cardiac stomach and a short,narrower posterior part called the pyloric stomach. The fundic part is absent in the stomach of a frog.

(B) $Sternohyal$ and $petrohyal$ muscles help in the respiration of frogs.
Contraction of the $sternohyal$ muscle during breathing in frogs lowers the floor of the oral cavity.
Contraction of the $petrohyal$ muscle during breathing in frogs raises the floor of the buccal cavity.

(D) Buccopharyngeal respiration in frogs involves the rhythmic movement of the floor of the buccal cavity. During this process,the nostrils are kept open to allow air to enter the buccal cavity,while the glottis remains closed. The mouth must be kept tightly closed to maintain the pressure required for gas exchange across the moist lining of the buccal cavity. If the mouth is opened,the pressure seal is lost,and the process stops. Therefore,option $D$ is the correct answer.

(A) The post-caval vein,also known as the posterior vena cava or inferior vena cava,is formed by the union of the two common iliac veins.
However,in the context of comparative anatomy (such as in the rabbit or frog),the post-caval vein receives blood from several major veins before reaching the heart.
Specifically,it receives blood from the renal veins (from the kidneys),the gonadial veins (from the gonads),and the hepatic veins (from the liver).
Therefore,the post-caval vein is constituted by the drainage of these major systemic veins.

(A) In the circulatory system of vertebrates (such as the frog),the systemic arch gives rise to several branches.
$A$ systemic branch is considered unpaired if it arises as a single vessel from the dorsal aorta to supply specific visceral organs.
The $Coeliaco-mesenteric$ artery is a major unpaired branch of the dorsal aorta that divides to supply the stomach,liver,spleen,and intestines.
In contrast,renal,iliac,and vesiculo-epigastric arteries are paired vessels that supply the kidneys,hind limbs,and bladder/abdominal wall,respectively.

(C) In a frog,the pulmonary veins are responsible for transporting oxygenated blood from the lungs to the left atrium of the heart.
$1$. The pulmonary circulation involves the movement of blood between the heart and the lungs.
$2$. Oxygenated blood collected from the lungs is carried by the pulmonary veins to the heart for systemic distribution.
$3$. Conversely,the pulmonary artery carries deoxygenated blood from the heart to the lungs for oxygenation.
$4$. Therefore,the correct vessel is the pulmonary vein.

(C) The carotid labyrinth is a specialized sensory structure located at the bifurcation of the common carotid artery in frogs.
It acts as a baroreceptor,which is sensitive to changes in blood pressure.
It helps in regulating the blood pressure of the blood flowing to the head region.
Therefore,it is concerned with the control of blood pressure.

(D) The renal portal system is a specialized venous system found in amphibians like the frog.
It is formed by the union of the femoral vein and the sciatic vein.
These veins join to form the renal portal vein,which carries blood from the hind limbs to the kidneys for filtration before it enters the systemic circulation.

(C) In many vertebrates,specifically in amphibians like frogs,the hepatic portal vein receives blood from the digestive tract and is joined by the anterior abdominal vein before entering the liver. This connection is a characteristic feature of the portal circulation in these organisms.

(B) The renal portal system is a circulatory arrangement where blood from the hind limbs is collected and transported to the kidneys before returning to the heart.
This system is well-developed in fishes and amphibians (like the $frog$).
It is significantly reduced in reptiles and birds.
It is completely absent in mammals (like the $rabbit$).

(A) The femoral artery is the primary blood vessel supplying the lower limb.
It originates as a continuation of the external iliac artery.
It supplies blood to the lower abdominal wall,the groin region,the external genitalia,and specifically the muscles of the dorsal and anterior parts of the thigh.

(B) The correct answer is $B$. In frogs,the rectum opens into a common chamber called the $Cloaca$. The $Cloaca$ serves as a common opening for the digestive,excretory,and reproductive systems.

(A) In the skull of a frog,bones are classified as either cartilage bones (replacing cartilage) or membrane bones (formed directly in the dermis).
$1$. The $Fronto-parietal$ is a large,flat bone that covers the dorsal surface of the cranium and is formed by the fusion of the frontal and parietal bones. It is a membrane bone.
$2$. The $Sphenethmoid$,$Pro-otics$,and $Exo-occipital$ are all cartilage bones that develop from the chondrocranium.

(C) The correct answer is $C$. The sphenethmoid is an unpaired bone located in the skull of certain vertebrates,such as frogs. In the tadpole larva,the cranial segment is cartilaginous,but during development,it ossifies into a single,tubular bone known as the sphenethmoid. Other options like premaxilla,pro-otics,and pterygoid are paired bones found in the skull.

(B) The $tympanic$ $bulla$ is a bony, hollow structure that encloses the middle ear cavity.
It is a distinct feature found in the skull of mammals, such as the rabbit ($Oryctolagus$ $cuniculus$).
In contrast, amphibians like frogs do not possess a $tympanic$ $bulla$; instead, they have a $tympanic$ membrane exposed on the surface of the head.
Therefore, the presence of a $tympanic$ $bulla$ is characteristic of the skull of a rabbit.

(D) The $Sphenethmoid$ bone is a cranial bone found in the skull of a frog. It is a single,median bone that forms the anterior part of the cranium,protecting the brain and supporting the nasal capsules.

(D) In the skull of many vertebrates,particularly in amphibians and reptiles,the $Pterygoid$ bone is characteristically $Y$-shaped. It is a paired bone that forms part of the palate of the mouth.

(B) The parasphenoid bone is a flattened and inverted $T$-shaped bone that is situated in the median position along the floor of the cranium in a frog. It provides structural support to the ventral surface of the braincase.

(C) In frogs,the vertebral column consists of $9$ vertebrae and a urostyle.
- The $1^{st}$ vertebra (atlas) is procoelous.
- The $2^{nd}$ to $7^{th}$ vertebrae are also procoelous (concave anteriorly and convex posteriorly).
- The $8^{th}$ vertebra is amphicoelous (concave on both anterior and posterior surfaces).
- The $9^{th}$ vertebra is procoelous with a convex anterior surface and a double convex posterior surface.
Therefore,the $8^{th}$ vertebra is amphicoelous.

(A) The suprascapula is the broader and thinner dorsal part of the scapula.
It is primarily composed of calcified cartilage,which provides structural support while maintaining flexibility in the pectoral girdle of certain vertebrates like frogs.

(A) The primary difference between mammalian (rabbit) and amphibian (frog) bones is the presence of the Haversian system.
In the compact bone of long mammalian bones (like the humerus,femur,and tibia),a network of branching canals known as Haversian canals is present,which contains blood vessels and nerves.
This system is characteristic of mammals and is absent in the bones of amphibians like frogs.

(C) The lower jaw,or the $II$ part of the mandibular arch,is initially cartilaginous and is known as Meckel's cartilage. During development,this cartilage is gradually replaced by bone to form the mandible.

(D) In a frog, the vertebral column consists of $9$ vertebrae. The $8^{th}$ vertebra is procoelous, meaning it has a concave anterior surface and a convex posterior surface. However, the $9^{th}$ vertebra is unique because it has an anterior convex surface (biconvex) to articulate with the $8^{th}$ vertebra, and it also possesses two posterior convex surfaces (condyles) to articulate with the urostyle.

(D) The Glands of $Swammerdam$ are specialized calcareous structures found in amphibians,particularly in frogs.
These glands are located on either side of the vertebral column at the points where the spinal nerves emerge from the intervertebral foramina.
They are involved in calcium metabolism and storage.

(C) The fifth cranial nerve of a frog is the $Trigeminal$ nerve.
It arises from the antero-lateral sides of the $medulla$ $oblongata$.

(A) The $Maxillary$ nerve is a branch of the trigeminal nerve ($V$ cranial nerve) in frogs. It is primarily a sensory nerve that innervates the skin of the upper lip,the upper jaw,the nasal mucosa,and the lower eyelids. Therefore,it is responsible for the sensory innervation of the upper jaw region.

(A) In amphibians like frogs,there are $10$ pairs of cranial nerves.
In humans (mammals),there are $12$ pairs of cranial nerves.
Therefore,the correct sequence for frog and man is $10$ and $12$.

(C) The $Columella$ $auris$ is a bone found in the middle ear of amphibians, reptiles, and birds.
It is a modified $Hyomandibular$ bone, which is derived from the dorsal end of the hyoid arch.
In mammals, this same structure is homologous to the $Stapes$ bone.

(D) The $fenestra$ $ovalis$ (also known as the oval window) is an opening in the auditory capsule of the frog's skull.
It serves as the connection point that separates the middle ear cavity from the internal ear.
In the frog,the tympanic cavity is connected to the internal ear via two openings: the $fenestra$ $ovalis$ and the $fenestra$ $rotunda$.

(C) The acoustic spots (also known as maculae or cristae) are sensory structures found within the internal ear of a frog.
These structures are specifically located in the ampullae of the semicircular ducts,which are part of the membranous labyrinth.
The membranous labyrinth is the system of fluid-filled sacs and ducts within the bony (osseous) labyrinth that contains the receptors for hearing and equilibrium.

(B) The testes are located in the extra-abdominal scrotal sacs,and the ovaries remain attached to the abdominal wall by a ligament called the $mesovarium$. Both the testes and the ovaries are positioned ventral to the kidneys.

(B) The correct answer is $B$.
Bidder's canal is a longitudinal canal present on the medial border of the kidney in male frogs.
The $vasa$ $efferentia$ from the testes enter the kidney and open into this Bidder's canal.
From this canal,the sperms are transported to the urinogenital duct.

(A) In the female rabbit,the reproductive tract consists of a pair of oviducts. The proximal part of the oviduct is expanded and is known as the uterus. The rabbit possesses a duplex uterus,where each oviduct opens into a separate uterus,and both uteri open into the vagina.

(B) The correct answer is $B$.
Each ovary is attached to the dorsal body wall by a fold of peritoneum known as the mesovarium.
This structure provides support and carries blood vessels and nerves to the ovary.

(B) In many lower vertebrates, such as amphibians, the ovaries are not directly connected to the oviducts. When the ova mature, they are released into the body cavity, known as the $Coelom$. From the $Coelom$, the ova are then picked up by the ciliated $Oviducal$ funnel (ostium) to enter the oviduct. Therefore, the correct anatomical space into which they are shed is the $Coelom$.

(A) The proctodaeum is the posterior portion of the embryonic alimentary canal.
It is formed by an invagination of the ectoderm at the posterior end of the embryo.
In mammals like the rabbit,it eventually develops into the anal canal,which is lined by ectoderm.

(C) In frogs,the arterial system consists of two systemic arches (left and right) that arise from the truncus arteriosus. The carotid artery and renal artery are also present as part of the systemic circulation. However,there is no specific vessel named the 'cerebral artery' that arises directly from the systemic arches in the same manner as the carotid or systemic arches. The brain receives blood through the carotid arteries. Therefore,the 'cerebral artery' is not a standard anatomical term for a primary artery in the frog's circulatory system.

(A) The venous system of a frog includes a $Renal$ $portal$ $system$ and a $Hepatic$ $portal$ $system$.
In mammals,the $Renal$ $portal$ $system$ is absent.
Therefore,the presence of the $Renal$ $portal$ $system$ is a characteristic feature that distinguishes the venous system of a frog from that of a mammal.