HD wallets are all about privacy and security as you generates a new address each time you want to do a transaction , now let's assume I have both these addresses (grabbed them randomly from Blockchain.info) :
161KxR9rfW7XVxiAk7oJ6t7dpryUFXTxvE - 0.30 [btc]
1HCocZuYDhTc7ioCsaeVzPnkJVxi6mAMT1 - 0.80 [btc]
and they are both generated by an HD wallet ... If I want to send 1.10
BTC , will both addresses appears in the blockchain ? If it's the case then how this will keep me anonymous exactly
It doesn't make much sense
Yes, both will appear in the blockchain. HD wallets doesn't make your addresses invisible to others.
As far as I can see, all that thing about HD wallet have large privacy and security advantage are over-exaggerated. The only thing to note about HD wallet is that all the address are derived from a single seed phrase, all other works the same way as most of the well known wallets that creates new addresses whenever they're needed (for sending changes).
Only advantages I can think of is because all addresses comes from one seed, losing a single private key (because of faulty client perhaps) would be pretty much impossible. And that you don't have to create backups if you have the seed (tho I still do it).