The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands. The hypothalamus and pituitary gland are neuroendocrine organs.
A newspaper lead (or lede if you prefer) can do its job in one sentence, but with few exceptions, a paragraph will contain more than one sentence. The OWL site, aimed at college students, suggests a length of from three to five or more sentences.
Two letters, but technically, a complete sentence (the subject is the understood you). So, to prevent this kind of silliness, teachers understandably began quantifying their expectations: Write a paragraph of at least five sentences that shows action. Some teachers probably made it a permanent policy: In this class, all paragraphs must have at least five sentences. All that is fine.