LAB 4.5 Reproductive system - hen
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1. Ovary (only one, derived from left side). The ova at
varying stages of
development to egg
yolks are seen in the image below.
2. Ostium (catches egg yolk)
The ova in the most advanced state of development appear as almost
full-sized
egg yolks. Each ovum is present in the hen chick when she hatches, but
development from a very small ovum to a complete hen's egg takes two
weeks. Growth of the yolk accelerates ten days before ovulation when
the yolk is released into the oviduct. A large infundibulum
(ostium) leads to a thick
glandular
region of the oviduct where egg albumen is formed, then to a narrower isthmus
where
shell membranes are added, and finally to a wide uterus where a
calcareous shell is formed. In the image below is the glandular region,
with the oviduct
slit open and laid out flat. The vagina opens into
the cloaca and forms mucus to facilitate egg-laying.
4. Isthmus (deposits shell membranes)
5. Uterus (deposits calcareous shell)
6. Urodaeum of cloaca
Study hint: There is more
information on eggs and their formation coming up in LAB 11.
