|Original (French) Title||La Peau|
|The Ear||Mouth and Teeth|
The episode begins with Peter and Claire riding horses as the narrator explains the purpose of skin. The scene zooms in on Peter's epidermis, where a few Bacteria are desperate to get inside the skin. A sweat gland goes into action, washing the Bacteria away from the sweat pore. The scene switches to the basal layer of epidermis where numerous new cells are formed. The newformed cells push and bump into each other on their climbing to the epidermis, where they eventually become a layer of dead cells. At this moment, a few deceased cells are blown away by the wind as the Bacteria duck to avoid the debris.
In a nearby blood vessel, Globus decides to take the young Red Corpuscles on a tour of the skin. On their way through epidermis, they meet some Melanocytes and the young Corpuscles instantly assume that they are lying around the skin doing nothing, but Lieutenant Jumbo denies their accusations. An offended female Melanocyte joins the conversation, explaining their purpose of lying around to absorb the ultra-violet radiation and generate tan for the skin cells, silencing the Corpuscles as they move along.
The tour advances deeper in dermis, where Globus introduces the Corpuscles to a concept known as "Gardens of Italy", considering that most of the sense receptors in human skin and microscopic corpuscles in human body got discovered by and/or named after the Italian scientists. They walk down the blood vessel and meet an Arrector Pili Muscle at work. He is very tired and feels down considering the purpose of himself. As the Corpuscles walk further down, they meet a common example of cold receptor, Krause Corpuscle, where most of them feel cold and shiver as the tired receptor himself sneezes. After advancing deeper, they meet the Ruffini Corpuscle, heat sensor, the exact opposite of Krause, sweating intensely. Globus presents the gentle pressure sensor, the Meissner's Corpuscle. Globin exclaims that all of the receptors look beautiful.
The Corpuscles reach the hypodermis, the deepest layer of the skin. Globus introduces the adipose tissue, or body fat, as the Lipids in bloodstream escape through the walls of the artery to build it up. Then, this part of the adipose tissue moves away to reveal the Pacinian Corpuscle, the hard pressure receptor. They walk further down the artery to see a sweat gland ejecting a drop of sweat. Globus notices a hair shaking rapidly, but declares that it might be something serious.
Lieutenant Claire and Captain Peter observe the dermis and notice several hairs shaking rapidly. Claire claims it's the Arrector Muscles, but when Peter investigates it, he finds out that they are completely relaxed, thus it's not them who are contracting the hair strands. Then, Claire notices the activated Pacinian Corpuscle, registering hard pressure, giving the clear sign that something is happening outside. The scene pans out into the epidermis, where it is revealed that it's a mosquito that had landed on Peter's skin, preparing to bite him. The mosquito penetrates Peter's skin with its stinger and the Bacteria, which were attempting to get in the body at the beginning of the episode, find the chance.
The bloodstream is going smoothly until the stinger ruptures the blood vessel, beginning to suck the blood out of it. As Hemo helps Globus, Lieutenant Jumbo requests help from the Antibodies. As soon as they arrive, the mosquito begins injecting Antigens. Metro informs L. Claire and C. Peter of the alert and they reach the blood vessel which is slowly filling with Antigens. The Antibodies begin fighting the Antigens without much success, so Lymphocytes and Basophils come and aid them. Macrophages arrive to clean the mess and the Platelets begin repairing the ruptured walls.
In the outside world, Peter realizes that the mosquito stung him and begins scratching his skin. This, however, gives the Bacteria an opportunity to finally make their way into the bloodstream. As the body's sentinels still rest, the Bacteria make their way into the bloodstream and start multiplying, identified as Streptococci. However, the Antibody and Lymphocyte forces are not enough. In the meantime, Peter's Mum gives his son a disinfectant, helping his body to destroy the germs. As he and Claire go walking out, the narrator ends the episode:
"So it turns out that the skin is not just a wrapping intended to keep your insides in, far from it. It's a complicated organ, and a large one making up about 7% of your body. The skin grows one third of the blood circulation. It has three layers: hypodermis, dermis, and epidermis. Together, they keep our bodies comfortable, clean, and healthy."
- The first episode to feature Basophils in action.
- This episode features the teenage designs of characters in between two episodes that have the opposite designs.
- Globus incorrectly named the Meissner's Corpuscle "Golgi Corpuscle", which is a cellular organelle for storing nutrients.
- The mosquito in this episode is identified as Anopheles, that counts over 400 species with 1/4 of them being able to cause malaria.
- The skin is the largest organ in the human body which consists of multiple layers. Altogether, they create not only a defensive barrier, but an organ that has the role to keep the body temperature, create vitamin D and expel harmful waste.
- The skin is composed of three main layers:
- Epidermis — thin, outermost and visible layer of the human skin. It is composed of deceased cells that eventually get replaced by new cells dividing very rapidly in the basal layer. The epidermis also contains melanocytes, cephalopod-looking cells that initiate pigmentation using the substance called melanin, that determines our skin color and prevents us from getting burnt by harmful UV radiation.
- Dermis — thicker layer of the human skin located beneath the epidermis. It contains:
- Hair strands — follicles of frequently dividing cells scattered through the skin. Specific spots along the body, like hair, pubis and armpits, have larger concentrations of hair than the other parts of the body. Each hair is held in place by arrector pili muscle.
- Blood vessels
- Cutaneous receptors — nerve endings that have the role to transmit sense of touch. There are main five receptors:
- Krause receptor — cold
- Ruffini receptor — heat
- Meissner's receptor — gentle pressure and light touch
- Pacinian receptor — hard pressure and hard touch
- Free nerve endings — pain
- Sweat glands — tubular structures that have the role to expel sweat through pores, regulating the body temperature and quantity of waste in the body.
- Sebaceous glands — small glands within hair follicles that secrete sebum, an oily substance to help lubricate the skin and hair.
- Hypodermis — the deepest layer of the human skin located beneath the dermis. It contains fat connective tissue (adipose tissue) that helps preserve the heat and lipids that are necessary for many functions.