Dr Chris and Dr Xand reveal the surprising secret behind the speed of your nerves, Dr Xand finds out what happens if you don't wash your hands, and the twins head out onto the street to test out a mind-bending trick that reveals how you can make your favourite cake look bigger than it is. Meanwhile, the ouch-mobile is opening its doors for more medical mysteries, and in accident and emergency one patient has a sweet stuck up their nose and another has an ear that is swelling fast.

In this episode, the doctors reveal where your blood comes from, Dr Chris meets a patient undergoing life-changing brain surgery and there is a mind-bending trick to test the powers of concentration. There are also more medical mysteries in Ouch and About, and in accident and emergency one patient is in with a double sporting injury, while another has taken a nasty tumble with her horse.

With the help of opera singer Lucy O'Byrne, the doctors reveal the hidden muscle that makes you breathe. Dr Xand heads to a DNA laboratory to solve the mystery of who stole his strawberry milk and there is a chance to play along at home with another mind-bending trick. Meanwhile, the ouch-mobile is open for business, and over in accident and emergency one patient has cut their eyebrow and another has stapled his own finger.

The doctors reveal what happens when you get diarrhoea, Dr Xand gets his skates on when he meets Alexia and Kloe from CBBC's Ice Stars to investigate how they spin without getting dizzy, and there's a hidden camera experiment. Meanwhile, the ouch-mobile is open for more medical mysteries, and in accident and emergency one patient needs surgery for a broken arm and another gets help with a painful toe.

The Doctors test a new theory to see if they can find out why skin goes wrinkly in the bath, Dr Chris meets a patient taking part in ground-breaking heart research, and test the power of your eyes in today's mind-bending trick. Meanwhile, there are more medical mysteries in 'Ouch & About', and over in Accident & Emergency one patient has a very sore head and another has dislocated her jaw.

The doctors look at your kidneys and reveal how these amazing cleaning machines work. The ouch-mobile is open for more intriguing medical mysteries, and Dr Xand tries out some vision-shifting spectacles for this episode's mind-benders. Meanwhile, in accident and emergency, one patient has an unusual break in his leg and another has a stone stuck in his ear.

The doctors find out what happens when you eat with the help of a miniature Xand doll, test your ears and eyes in a baffling mind-bending trick, and join Dr Chris at work fighting infectious diseases. Meanwhile there's an unusual 'itis' in the ouch-mobile, and over in accident and emergency one patient has cut their head and another has a very wonky finger.

The doctors reveal the amazing organs that keep you alive before you're born. Dr Xand meets patients undergoing treatment at a burns clinic, and Dr Chris hits the high street to test another mind-bending trick. Meanwhile, there are more medical mysteries in Ouch and About, and over in accident and emergency one patient has broken her ankle and another has been hit on the head with a cricket bat.

The doctors choose some of their favourite moments including an experiment to find out what happens when you cough and a life-changing operation that allows someone to hear for the very first time. There's a brand new mind-bending trick to baffle your brain, and the ouch-mobile opens its doors to help solve more medical mysteries.

In this special episode, Dr Chris and Dr Xand take a look at what happens to your body, and why, when you reach puberty. Spots are in the spotlight, Dr Xand finds out why you sweat more, and Dr Chris discovers the real reason teens don't want to get up in the morning. There are also some animated top tips on how to get through puberty, and the doctors do some house calls... with a difference.