Structural Organisation in Animals

Given: We need to draw and label the digestive system of a frog (*Rana tigrina*).

Concept: The digestive system of a frog consists of the alimentary canal and the associated digestive glands.

Diagram Description (to be drawn in the exam):

Draw a neat, well-labelled diagram showing the following parts in order:

Alimentary Canal (in sequence):
1. Mouth / Buccal cavity — wide opening at the anterior end of the head
2. Pharynx — short region behind the buccal cavity
3. Oesophagus — short, wide tube connecting pharynx to stomach
4. Stomach — J-shaped, muscular sac; divided into cardiac (anterior) and pyloric (posterior) parts
5. Small Intestine (Duodenum + Ileum) — duodenum is the first part (U-shaped loop); ileum is the long, coiled part
6. Large Intestine (Rectum) — short, wide tube
7. Cloaca — common chamber opening to the exterior via the cloacal aperture

Associated Digestive Glands (to be shown with ducts opening into the alimentary canal):
1. Liver — large, bilobed gland; secretes bile stored in the gall bladder; bile duct opens into the duodenum
2. Pancreas — lies in the loop of the duodenum; secretes pancreatic juice; pancreatic duct opens into the duodenum

Labels to include in the diagram:
- Oesophagus
- Stomach
- Liver
- Gall bladder
- Bile duct
- Pancreas
- Pancreatic duct
- Duodenum
- Ileum
- Large intestine / Rectum
- Cloaca
- Cloacal aperture

Note for students: The diagram should be drawn in pencil, with all parts clearly labelled using straight label lines. The liver is the largest gland and should be shown on the right side of the stomach.

Given: We need to state the function of ureters (urinogenital ducts) in a frog.

Concept: In frogs, the ureters are also called urinogenital ducts because they serve a dual function — both excretory and reproductive — especially in males.

Functions of Ureters (Urinogenital Ducts) in Frog:

(i) In Males:
- The ureters carry urine from the kidneys to the cloaca for excretion.
- They also serve as the vas deferens (sperm duct): the vasa efferentia from the testes open into the kidneys, and sperms are carried along with urine through the urinogenital duct into the cloaca and then to the exterior.
- Thus, in males, the ureter performs both excretory and reproductive functions (hence called urinogenital duct).

(ii) In Females:
- The ureters carry only urine from the kidneys to the cloaca.
- They have no reproductive function in females, as the oviducts are separate and open independently into the cloaca.

Conclusion: The primary function of the ureters in frogs is the conduction of urine from the kidneys to the cloaca. In males, they additionally serve as the pathway for sperms, making them true urinogenital ducts.