Anal canal development in the embryonic and early foetal period

The aim of study is to investigate the development of the anal canal in human embryos and foetuses. In embryos at stage 19 the boundary between the ectodermal and endodermal linings of the anal canal is located just below the level of the internal anal sphincter muscle. Histological sections showed that the first signs of anal columns are observed in embryos at stage 21 (51 days).

Muscle spindles in the levator palpebrae superioris muscle of human foetuses

Studies were performed on the levator palpebrae superioris muscle, isolated from foetuses aged 17 to 30 weeks. The number of muscle spindles varied from 2 in the 17th week to 7 in the 30th week. The length of the muscle spindles ranged from 20 to 500 microm, and the diameter varied from 10 to 70 microm. These observations show that the number of muscle spindles in levator palpebrae superioris muscles is significantly lesser than that in the extraocular muscles.