Hint: Lateral hearts are also known as pseudohearts or commissural vessels. These blood vessels present on either side of the alimentary canal of some annelids that pump blood from the dorsal vessel to the ventral vessel.
Complete answer:
-A pair of large, thick, and muscular vertical vessels called hearts are present in segments 7th, 9th 12th, and 13th in the earthworm.
-Lateral hearts are present in segments 7 and 9 that connect dorsal and ventral vessels only.
-Lateral hearts have 4 pairs of thick valves.
-Lateral esophageal hearts are present in the 12th and 13th segments.
-Lateral esophageal hearts have 3 pairs of thin valves.
-The hearts of the earthworm are contractile and encircle the alimentary canal around.
Additional Information: -Earthworms have a neurogenic heart.
-The latero-esophageal hearts have thick muscular walls and consist of a pair of valves at each junction with the dorsal vessels and supra-oesophageal vessel, and another pair of valves at the ventral end.
-Two pairs of loop-like vessels are present in the 10th and 11th segments which connect the supra-oesophageal with the lateral esophageal heart. These vessels are called anterior loops.
-The anterior loop is not muscular or pulsatile.
-The anterior loops are devoid of the valves.
So, the correct answer is ‘Four pairs of valves and are situated in segment 7 and 9’.
Note: -The four pairs of valves in the lateral hearts allow the blood to flow only downwards.
-The latero-esophageal hearts have thick muscular walls and consist of a pair of valves at each junction with the dorsal vessels and supra-oesophageal vessels.
-Another pair of valves is also present at the ventral end. These allow the blood to flow downwards only.
