Chapter 7: Structural Organisation in Animals (Structural Organisation)

Draw the diagram shown in the concept notes and label: mouth, buccal cavity, oesophagus, stomach, duodenum, intestine (ileum), rectum, cloaca and cloacal aperture, with the digestive glands liver, gall bladder and pancreas (and the common bile duct). Points to show: the alimentary canal is short (carnivore); bile from the gall bladder and pancreatic juice from the pancreas enter the duodenum through a common bile duct; the rectum opens into the cloaca.

The ureters carry urine from the kidneys to the cloaca (and the urinary bladder). In the male frog the ureter also carries sperms (which come from the testes through the vasa efferentia and Bidder's canal into the kidney), so it acts as a urinogenital duct. In the female the ureter carries only urine; the oviducts open separately into the cloaca.

Frogs are carnivores: animal food is easier to digest than plant food (no cellulose), so a long intestine is not needed and the length of the intestine is reduced.

In water: through the moist skin (cutaneous respiration), by diffusion of dissolved oxygen. On land: through the buccal cavity, skin and lungs (pulmonary respiration), air entering through the nostrils. During aestivation and hibernation: only through the skin.

Special venous connections: the hepatic portal system carries blood from the intestine to the liver before it returns to the heart; the renal portal system carries blood from the lower parts of the body to the kidneys.

Externally, the male has vocal sacs (sound-producing) and a copulatory pad on the first digit of the forelimbs, which the female lacks. Internally, the male has testes and urinogenital ducts; the female has ovaries and separate oviducts.