###     The largest artery is the aorta[21] and the largest vein is the inferior vena cava.[22]
The largest internal organ is the liver.[23] It is also the heaviest organ, with an average of 1.6 kilograms (3.5 pounds).[24]
The largest external organ, which is also the largest organ in general, is the skin.[25]
The longest muscle is the sartorius muscle in the thigh.[26]
The longest single nerve is the sciatic nerve in the thigh, counting its branches and axons.
N Animals
Blue whale Edit
As the largest animal alive, the blue whale has the largest instance of several body parts.

Its tongue weighs around 2.7 tonnes (3 short tons)[1]
Its mouth is large enough to hold up to 90 tonnes (100 short tons) of food and water.[2]
Its heart typically weighs 600 kg (1,300 lb)[1] and can reach 900 kg (2,000 lb) in exceptional cases[3]
Its aorta is about 23 centimetres (9.1 in) in diameter.[4]
The blue whale's penis typically measures 8–10 ft. (2.4 – 3 meters)[5]
Other animals Edit
The giant and colossal squids have the largest recorded eyes of any living animal, with a maximum diameter of at least 27 cm (11 in).[6] Only the extinct ichthyosaurs are known to have had larger eyes.[6]
The giraffe has the longest neck of any land mammal.[7]
The walrus has the largest baculum of any mammal.[8]
The wandering albatross has the largest wingspan at 3.63 metres (11 feet 11 inches).[9]
The longest horns ever recorded belonged to a wild water buffalo and measured 4.24 metres (13 feet 11 inches) from tip to tip.[10]
The largest and heaviest brain belongs to the sperm whale, weighing around 9 kilograms.[11]
The Arctic lion's mane jellyfish may be the longest animal; the biggest had a bell (body) with a diameter of 2.28 meters (7 feet 6 inches) and the tentacles reached 36.6 m (120 ft). It was found washed up on the shore of Massachusetts Bay in 1870.[12]
Bootlace worms can reach great lengths. A specimen was measured at 55 m (180 ft) but this may be unreliable as the body is somewhat elastic.[13]
In proportion to body size Edit
The Morgan's sphinx hawk moth has the longest proboscis in relation to its body size. Its 25–30 cm proboscis is over 3 times longer than its body. It is also known as Darwin's moth because Charles Darwin predicted its existence some 40 years before it was discovered from experiments he did on an orchid with a "foot long" nectary.[14]
The tube-lipped nectar bat has the longest tongue of any mammal in relation to its body size. Its 85 mm (3.3 in) tongue is 1.5 times longer than its body, and must be kept inside its rib cage.[15]
The barnacle is the creature with the largest penis as a proportion of its body size.[16]
Among vertebrates, the Argentine blue-bill duck has the longest penis in relation to its body size.[17]
The vampire squid has the largest eyes of any animal relative to its size.[18]
The kiwi lays the largest egg of any bird relative to its size - up to a quarter of the mass of the female.
Shrews have the largest brain-to-body mass ratio of any animal, with brains that are 10% of body weight. Humans however have the largest encephalization quotient of any animal.[19]