Counted as tunnels that pass all the way through you, the human body has seven holes.1Live Science. How many holes does the human body have? The number depends on what you call a hole, so a dentist, a dermatologist, and a mathematician would each give a very different count.
Why a Hole Is Not the Same as an Opening
Mathematicians count holes using topology, the study of shape. It treats every object as if it were made of stretchy clay, so bending and squashing change nothing. Seen this way, a closed outer surface can be reshaped into a ball with some number of handles, and that number is its count of holes.2Applied Mathematics. Topology in Biology: Singularities and Surgery Transformations in Metazoan Development and Evolution A ball has none, a doughnut has one, and a pretzel-like double doughnut has two.3Applied Mathematics. Topology in Biology: Singularities and Surgery Transformations in Metazoan Development and Evolution
In living things, those handles usually show up as channels, such as the digestive tube running from mouth to anus.4Applied Mathematics. Topology in Biology: Singularities and Surgery Transformations in Metazoan Development and Evolution An adult animal body is, in shape terms, a ball with a set of handles.5Applied Mathematics. Topology in Biology: Singularities and Surgery Transformations in Metazoan Development and Evolution Picture yourself as a thick doughnut with the gut as its central tunnel. The food inside your gut is technically still outside your body. Other tunnels branch off and join the main one, which is why counting gets tricky.
The classic puzzle is the coffee mug and the doughnut. They count as the same shape because each has exactly one tunnel, the mug’s running through its handle. The cup part is just a dent, so it adds no hole. That gives you a test for the body: could the feature be smoothed away without cutting anything? If so, it’s a dent, not a hole. A dimple or a pocket that dead-ends fails the test.
A straw has one hole, not two, because both ends belong to a single tunnel. By the same logic, your mouth and anus are two ends of one hole.
The rules are simple: you may bend, stretch, and squash a shape as much as you like, but you may not tear it or join two separate spots together. That’s why a wide hole and a pin-sized hole count the same, since stretching one into the other never needs a cut.
Where the Seven Holes Are
The face hides tunnels that join the gut. Your nostrils lead back into the throat, where they meet the passage from the mouth. Each eyelid corner also has a tiny opening that funnels tears into small channels.6PubMed Central. Anatomical and Functional Alterations in Nasolacrimal Duct Obstruction: A Comprehensive Review Each eye has two such openings, one on the upper lid and one on the lower, for four in total. Those channels drain into a tear sac and then down the tear duct into the nose.7PubMed Central. Anatomical and Functional Alterations in Nasolacrimal Duct Obstruction: A Comprehensive Review That drainage is why your nose runs when you cry and why you can sometimes taste eye drops.8Wikipedia. Nasolacrimal duct
You can find yours in a mirror. Look at the inner corner of each eye, where a small pink dot sits on the edge of both the upper and lower lids. Those dots are the start of the tear drainage tunnel.
The nose counts as two holes, not one. Each nostril opens separately and reaches the throat, and a wall inside the nose keeps the two passages apart until the back.
That makes the mouth, anus, two nostrils, and four tear openings: eight openings that all connect.9Live Science. How many holes does the human body have? Yet topology says these eight interconnected openings form seven holes.10Live Science. How many holes does the human body have? When tunnels join inside, one opening is always used up as the shared exit, so holes equal openings minus one.
A pair of pants shows the rule. It has three openings, the waist and two legs, but only two holes. Stretch the waist wide and the legs become two loops on a flat sheet.
Openings That Don’t Count
Ears end at the eardrum, a thin membrane that covers the end of the ear canal.11ENT Jacksonville. Anatomy of the Ear So the ear canal is a dent, not a tunnel.
The belly button is a common wrong guess. The navel is a scar where the umbilical cord attached before birth, and it is closed underneath. It is a dimple, so it adds nothing.
The urethra leads to the bladder, which is closed off from the rest of the body’s tunnels. The female reproductive tract looks more promising. The fallopian tubes connect the uterus to the abdominal cavity.12Instituto Bernabeu – ClÃnicas de reproducción asistida. The importance of the Fallopian tubes in fertility But the tube’s far end opens into the abdominal cavity, not to the outside.13Wikipedia. Fallopian tube There is no direct link to the ovary, so an egg enters that cavity before entering the tube.14SEER Training Modules. Genital Tract Since the abdominal cavity is sealed, this route doesn’t make a through-tunnel. So male and female bodies share the same seven holes.
Counting Tiny Openings Like Pores
If you count pores, the total reaches the millions. An average adult has about 2 million working sweat glands.15PubMed Central. Regional variations in transepidermal water loss, eccrine sweat gland density, sweat secretion rates and electrolyte composition in resting and exercising humans Palms and soles are densest, at roughly 250 to 550 glands per square centimetre.16PubMed Central. Physiology of sweat gland function: The roles of sweating and sweat composition in human health Hands and feet cover about 5% of your skin yet hold about a quarter of your sweat glands.17PubMed Central. Regional variations in transepidermal water loss, eccrine sweat gland density, sweat secretion rates and electrolyte composition in resting and exercising humans
None of these are holes in the topological sense. A sweat gland is a coiled tube closed at its deep end, and a hair follicle is a pocket in the skin. Both are dents, so they add nothing to the seven.
Holes Inside the Body
Bones are full of openings. The skull has many that let nerves and blood vessels pass through.18Kenhub. Foramina and fissures of the skull19TeachMeAnatomy. Cranial Foramina – Anatomical Features and Key Structures
The heart can have one too. Before birth, a flap-like opening between the heart’s upper chambers lets blood bypass the lungs.20PubMed. Patent foramen ovale: A variant of normal or a true congenital heart disease? In about 75% of people it closes within a few months of birth.21PubMed Central. Patent Foramen Ovale—A Not So Innocuous Septal Atrial Defect in Adults In about 1 in 4 adults it stays open, letting a small amount of blood cross over.22PubMed Central. Patent Foramen Ovale—A Not So Innocuous Septal Atrial Defect in Adults
None of this changes the answer. The seven-hole count is about tunnels through the body’s outer surface, and a hole in a bone or a heart wall sits entirely inside.
When Surgery or Injury Adds a Hole
A person can gain or lose holes. A tracheostomy opens the windpipe through the neck, creating a new tunnel. After the tube comes out, the opening typically closes in about 5 days.23PubMed. Tracheal Stoma Closure and Healing Time in a Post-Acute Setting
Piercings work the same way. An earlobe piercing passes right through, so it adds one true hole, and a healed piercing that closes removes that hole again. Someone with two pierced ears has, strictly, nine holes.