Which cells of ‘Crypts of Lieberkuhn’ secrete antibacterial lysozyme?
A. Paneth cells
B. Zymogen cells
C. Kupffer cells
D. Argentaffin cells

Hint: Intestinal villi are tiny, finger-like projections that expand into the lumen of the small intestine. Length of each villus is approximately 0.5–1.6 mm.
The wall of alimentary canal from oesophagus to rectum own four layers known as:
- Serosa
- Muscularies
- Sub-mucosa
- Mucosa

Complete answer:
> Serosa: It is the outermost layer of the alimentary canal.
It is made up of a thin mesothelium with some connective tissue.
> Muscularies: It is formed by smooth muscles usually arranged into an inner circular and outer longitudinal layer.
> Sub-Mucosa: It is formed of loose connective tissues contain nerves, blood and lymph vessels
> Mucoa: It is the innermost layer which lines the lumen of the alimentary canal from oesophagus to rectum.
> Villi: Mucosa layer forms irregular folds known as rugae in the stomach and small finger-like foldings called villi in the small intestine.

- The cells lining the villi produce numerous microscopic projections called microvillus which give a brush border appearance.
- Villi are provided with a network of capillaries and large lymph node vessels named as lacteal.
- Mucosal epithelium poses goblet cells which secrete mucus that help in lubrication.
- Mucosa also forms glands in the stomach and crypts in between the bases of villi in the intestine particularly known as crypts of lieberkuhn.
- Paneth cells are present in the mucosa of Crypts of Lieberkuhn.
- The function of these paneth cells is to secrete antibacterial lysozyme which further kills bacteria.

Hence, the correct answer is option (A).

Note: Antibacterial enzymes are the enzymes which help in degrading structural components of cells of certain bacterias and fungi. Endolysins are antibacterial enzymes that are produced to kill the bacteria by destroying their cell wall. Endolysins mainly destroy the bond of peptidoglycans which is present in cells of bacteria.