Endocrine System

The endocrine system affects cells with certain receptors .

The nervous system can affect only nearby cells

Thymus

Inflammation and fever are nonspecific immune system reactions.

The endocrine system sends messages using hormones. It delivers messages from the nervous system to the excretory system. It tells the excretory system when the blood is out of balance.

Adrenalin.

One gland causes calcium ions to be released; another gland causes them to be absorbed

Depends on when you consider it a child. First it's a Zygote, a fertilized egg, and then a blastocyst. Medically it's not a child until it's born. But if we start with embryo you can read all about it in the link below. Someone wrote blood starts pumping and arms starts to develop but that is weeks later.

Blood pumps through the body.

or

Rhythmic breathing movements

the organs grow larger

eyes develop

lips start to form

Vocal cords develop.

Steroid hormones

The pancreas releases insulin into the bloodstream