Anatomy — Revision Notes

⚡ 30-Second Revision

Heart: — 3-chambered (2 atria, 1 ventricle). Incomplete double circulation.
Respiration: — Cutaneous (skin), Buccopharyngeal (mouth lining), Pulmonary (lungs).
Digestive System: — Mouth $\rightarrow$ Esophagus $\rightarrow$ Stomach $\rightarrow$ Small Intestine $\rightarrow$ Large Intestine $\rightarrow$ Cloaca. Liver (bile), Pancreas (enzymes).
Excretory System: — Mesonephric kidneys, Ureters, Urinary bladder, Cloaca. Ureotelic.
Male Repro: — Testes $\rightarrow$ Vasa efferentia $\rightarrow$ Bidder's canal (in kidney) $\rightarrow$ Ureter (urogenital duct) $\rightarrow$ Cloaca.
Female Repro: — Ovaries $\rightarrow$ Coelom $\rightarrow$ Ostium of Oviduct $\rightarrow$ Oviduct $\rightarrow$ Cloaca. External fertilization.
Tongue: — Anteriorly attached, protrusible, sticky.

2-Minute Revision

Frog anatomy is a study of amphibious adaptations. The digestive system starts with a wide mouth and an anteriorly attached, sticky tongue, leading to a short esophagus, J-shaped stomach, coiled small intestine, and a short rectum, all emptying into the cloaca – a common chamber for digestive, excretory, and reproductive wastes.

The liver produces bile, and the pancreas secretes digestive enzymes. Respiration is highly versatile: through moist skin (cutaneous), mouth lining (buccopharyngeal), and small lungs (pulmonary). The circulatory system features a three-chambered heart (two atria, one ventricle), resulting in incomplete double circulation where oxygenated and deoxygenated blood partially mix.

Renal and hepatic portal systems are present. The excretory system consists of mesonephric kidneys, ureters, and a urinary bladder, all draining into the cloaca. Frogs are ureotelic. In reproduction, males have testes connected to the kidneys via vasa efferentia, which open into Bidder's canal within the kidney, making the ureter a urogenital duct.

Females have ovaries that release eggs into the coelom, collected by oviducts that lead to the cloaca. Fertilization is external.

5-Minute Revision

A comprehensive understanding of frog anatomy is crucial for NEET. Begin with the digestive system: the wide mouth with maxillary and vomerine teeth, and a unique anteriorly attached, sticky tongue for prey capture.

Food passes through a short esophagus to a J-shaped stomach, then to a long, coiled small intestine (duodenum and ileum for digestion and absorption), and finally a short rectum. All undigested waste exits via the cloaca, a multi-functional chamber.

Accessory glands include the large, trilobed liver (bile production, stored in gallbladder) and the pancreas (digestive enzymes, hormones).

Respiration is a key adaptation: cutaneous respiration through the moist, vascularized skin is primary; buccopharyngeal respiration through the mouth lining provides supplementary gas exchange; and pulmonary respiration via small, simple lungs is used on land. Frogs lack a diaphragm.

The circulatory system is characterized by a three-chambered heart (two atria, one ventricle), leading to incomplete double circulation. Oxygenated blood from lungs/skin enters the left atrium, deoxygenated blood from the body enters the right atrium; both mix partially in the single ventricle. Blood is then pumped to the pulmocutaneous and systemic circuits. Notable features include the hepatic portal system and the renal portal system.

Excretion involves a pair of dark red, mesonephric kidneys that filter blood to produce urea (frogs are ureotelic). Ureters carry urine to a urinary bladder, which empties into the cloaca.

In the male reproductive system, a pair of testes produce sperm. Vasa efferentia connect the testes to Bidder's canal within the kidney. From Bidder's canal, sperm enter the ureter, which thus functions as a urogenital duct, carrying both urine and sperm to the cloaca.

The female reproductive system has ovaries that release eggs into the coelom. These eggs are collected by the funnel-shaped ostia of the oviducts, which then transport the eggs to the cloaca. Fertilization is external, occurring in water.

The nervous system includes a brain (forebrain, midbrain, hindbrain), spinal cord, and 10 pairs of cranial nerves.

Prelims Revision Notes

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Digestive System:

* Mouth: Wide, non-chewing maxillary and vomerine teeth. Tongue: Anteriorly attached, sticky, protrusible. * Esophagus: Short. Stomach: J-shaped. Small Intestine: Duodenum (receives bile/pancreatic juice) and ileum (absorption). Large Intestine (Rectum): Water absorption. * Cloaca: Common chamber for digestive, excretory, reproductive wastes. * Liver: Large, trilobed, produces bile (stored in gallbladder). Pancreas: Yellowish, secretes digestive enzymes and hormones.

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Respiratory System:

* Modes: Cutaneous (skin, primary), Buccopharyngeal (mouth lining), Pulmonary (lungs). * Lungs: Small, simple sacs. No diaphragm.

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Circulatory System:

* Heart: 3-chambered (2 atria, 1 ventricle). * Circulation: Incomplete double circulation (mixing of oxygenated and deoxygenated blood in ventricle). * Portal Systems: Hepatic portal system (digestive tract to liver), Renal portal system (posterior body to kidneys). * Blood: Nucleated RBCs.

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Excretory System:

* Kidneys: Pair of dark red, mesonephric, filter blood. * Excretory product: Urea (Ureotelic). * Ureters: Carry urine from kidneys. Urinary Bladder: Stores urine. Cloaca: Common exit.

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Reproductive System:

* Male: Testes (yellowish, ovoid). Vasa efferentia (10-12 tubules) connect testes to Bidder's canal (in kidney). Ureter acts as urogenital duct (carries urine and sperm) to cloaca. * Female: Ovaries (large, irregular). Eggs released into coelom, collected by ostium of oviducts. Oviducts (coiled, glandular) lead to cloaca. * Fertilization: External, in water.

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Nervous System:

* CNS: Brain (Forebrain - olfactory, cerebral hemispheres, diencephalon; Midbrain - optic lobes; Hindbrain - cerebellum, medulla oblongata), Spinal Cord. * PNS: 10 pairs of cranial nerves, 10 pairs of spinal nerves.

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Skeletal System: — Bony skeleton, vertebral column, skull, girdles, limb bones.
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Key Terms: — Cloaca, Bidder's Canal, Incomplete Double Circulation, Cutaneous Respiration, Mesonephric Kidney, Ureotelic.

Vyyuha Quick Recall

To remember the path of sperm in a male frog: Tiny Vessels Bring Urine & Sperm to Cloaca.

Testes
Vasa efferentia
Bidder's canal
Ureter (Urine & Sperm)
Cloaca