You live here your whole life, and you just never get around to visiting ... yourself.

But now take a visit deep within, thanks to National Geographic Channel's documentary "Inside the Living Body," which displays goings-on inside your mouth, throat, heart, lungs, digestive tract, blood vessels and reproductive organs. All you have to do is sit back and watch, and keep doing all the things you ordinarily do.

Turns out this is quite a lot. As the film tracks the body's birth-to-death evolution, it demonstrates how you stay pretty busy without even being aware of it. You shed as many as 30,000 dead skin cells every minute. Your adult skeleton is replaced every seven to ten years. You transport the food you eat some 30 feet as you digest it. (Never a dull moment.)

A blend of computer imagery and endoscopic photography (tiny cameras attached to long, thin rubber tubes that can penetrate the body's mysteries) lets you travel to many out-of-the-way spots, and witness the metamorphosis of one "everywoman" over her 70-year life span.

Amazing to behold? Sure, but don't forget to breathe. You might hope to do it 600 million times in your life and this is no time to stop. "Inside the Living Body" airs at 9 p.m. tomorrow.

Other shows to look out for:

• Now turn your eyes skyward for "Seeing in the Dark," a rhapsodic sight-and-sound odyssey into the night sky. Produced, written and narrated by Timothy Ferris (and based on his book of the same name), the film is meant to lure newcomers into stargazing, and to hear from a few of those already in its thrall. Shot in high-def, the film features never-before seen astronomical photography and special effects as well as an original score by Mark Knopfler and Guy Fletcher. It interweaves themes of music, the stars, and the stark contrast between the brief span of human lifetimes and the vastness of the cosmos, where a backyard stargazer equipped with nothing more than binoculars can see light older than the human species. Says Ferris: "Astronomy, with its spectacular visual qualities and its relevance to enduring questions about the origin and evolution of the universe, has long been a gateway to science." His film is a gateway to astronomy. It airs 9 p.m. on Wednesday on PBS.

• To mark Hispanic Heritage month, PBS' "American Masters" is airing back-to-back documentaries about two important Mexican painters.

Premiering at 10 p.m. Wednesday (check local listings), "Orozco: Man of Fire" is a portrait of Jose Clemente Orozco, who, after early hardship and toil as a political cartoonist, became a leading force in the Mexican Mural Renaissance. His murals would adorn Mexico's most revered public spaces, inspire African-American contemporaries and move President Roosevelt to put artists to work during the Great Depression. Born in 1883, Orozco viewed the loss of his left hand — amputated after an accident mixing gunpowder for fireworks — as a gift, liberating him from his family's pressure to pursue a "respectable" career and freeing him to pursue his dream as an artist.

At 11 p.m., there's a repeat of "Rivera in America," the story of painter Diego Rivera, whose bold, visionary images sought to chronicle the history and culture of his native Mexico, as well as celebrate the workers of the world. The film recounts how in 1933 Rivera was commissioned by Nelson Rockefeller to paint "Man at the Crossroads," a mural to cover the lobby wall of the RCA Building in Manhattan's newly built Rockefeller Center. But its content (which included a giant May Day demonstration and an image of Lenin) stirred such an outcry, the Rockefellers paid Rivera his fee and blasted the mural from the wall.

• D.L. invades D.C. for his fourth comedy special for HBO. And "D.L. Hughley: Unapologetic", with all-new material taped in front of a live audience in the nation's capital, raises loads of funny issues with no remorse. Like the 2008 presidential race and whether America is really ready to elect a black man to the White House.

"What are we gonna do?" poses Hughley. "Steal the election, start a war, and give our friends jobs we know they ain't qualified for?"

With nothing to be sorry for, the hourlong special premieres at 11 p.m. today.