A papilla is a small, nipple-shaped projection of tissue that appears throughout the human body and even in plants. The word comes from the Latin for “nipple” or “bud,” and anatomists use it to describe dozens of different structures that share that same basic shape: a tiny bump or mound that increases surface area, houses specialized cells, or anchors moving parts. Papillae show up on your tongue, inside your skin, in your kidneys, on your heart valves, in your eyes, and on the surface of leaves. Despite sharing a name, each type does something quite different.
Tongue Papillae and Taste
The papillae most people have heard of are the ones on the tongue. If you stick your tongue out in a mirror, the visible bumps covering its surface are lingual papillae. There are four main types, and only three of them carry taste buds. Fungiform papillae are the mushroom-shaped dots scattered across the front two-thirds of your tongue. Circumvallate papillae are the large, dome-like structures arranged in a V-shape near the back. Foliate papillae sit along the sides toward the rear. All three house taste buds in their walls or surfaces, with distinct chemical profiles in their taste pore regions. Lectin histochemistry studies have shown that the sugar-chain signatures on taste buds differ between fungiform papillae and circumvallate or foliate papillae, meaning these structures are not just shaped differently but biochemically distinct as well.1PubMed. Comparative lectin histochemistry on taste buds in foliate, circumvallate and fungiform papillae of the rabbit tongue
The fourth type, filiform papillae, are the most numerous and the only ones that do not contain taste buds. They are the tiny, pointed projections that give the tongue its slightly rough, velvety texture. Their job is mechanical rather than sensory. In animal studies, the curved shape and orientation of filiform papillae help retain food on the tongue’s surface and direct it toward the throat for swallowing. Depending on where they sit on the tongue, they also appear to help grind food against the palate, sort out foreign particles, and spread saliva across the oral cavity to aid grooming and digestion.2PubMed Central. Morphometric Features and Microanatomy of the Lingual Filiform Papillae in the Wistar Rat
Dermal Papillae in Skin
Just beneath the surface of your skin sits a wavy border between the outer layer (epidermis) and the deeper layer (dermis). The upward projections of the dermis into the epidermis are called dermal papillae. They look like tiny fingers poking up from below, and they serve two key purposes: anchoring the epidermis firmly to the dermis so the layers do not slide apart, and supplying blood to the outermost skin cells, which have no blood vessels of their own. Each dermal papilla contains a capillary loop, a small U-shaped blood vessel that delivers oxygen and nutrients to the epidermis above. Electron microscopy studies have divided these capillary loops into two segments, one sitting within the papilla itself and one extending outside it, each with distinct structural features.3Journal of Investigative Dermatology. ULTRASTRUCTURE OF THE HUMAN DERMAL MICROCIRCULATION
Dermal papillae are also the reason your fingerprints exist. The pattern of ridges and whorls on your fingertips mirrors the arrangement of dermal papillae underneath. Where papillae are taller and more densely packed, the surface ridges are more pronounced. These ridges improve grip and, just as importantly, house Meissner’s corpuscles, the touch receptors responsible for detecting light pressure and fine texture. The density of these receptors varies across the hand: fingertips have significantly more Meissner’s corpuscles than the pads of the fingers, which in turn have more than the skin over the knuckle joints.4Annals of Anatomy. Regional variation in the density of Meissner’s corpuscles in human fingers That gradient is why your fingertips are so much better at reading Braille or detecting a hair-thin crack in a surface than the rest of your hand.
The Dermal Papilla in Hair Follicles
Confusingly, “dermal papilla” also refers to a completely different structure when the conversation shifts to hair. At the base of every hair follicle sits a cluster of specialized cells called the dermal papilla (often abbreviated DP). This tiny knob of tissue acts as the command center for hair growth. It receives signals from the surrounding skin and, in turn, instructs the hair matrix cells above it to divide and push upward, forming the hair shaft. Without a functional dermal papilla, a follicle cannot produce hair.
Research into what keeps these cells active has pointed to Wnt signaling, a molecular communication pathway, as a critical driver. When dermal papilla cells receive Wnt signals, they maintain their ability to induce hair growth. In experiments where dermal papilla cells were treated with Wnt3a or Wnt7a and then combined with skin cells on a host animal, hair growth increased dramatically compared to untreated cells.5Genes & Development. Wnt signaling maintains the hair-inducing activity of the dermal papilla More recent work has also found that serotonin can activate dermal papilla cells, switching on genes linked to hair growth. When these cells were treated with serotonin, gene expression analysis showed upregulation of hair-growth-related genes and enrichment of signaling pathways tied to serotonin receptors.6Scientific Reports. Serotonin activates dermal papilla cells and promotes hair growth These findings matter for the broader search for treatments for hair loss, since the dermal papilla is the structure that any future therapy would need to reawaken or sustain.
Renal Papillae and Kidney Stones
Inside each kidney, the tissue is arranged into cone-shaped units called pyramids. The pointed tip of each pyramid, which juts into the collecting area where urine gathers, is called a renal papilla. It is the final stop for urine before it drains into the renal pelvis and eventually down to the bladder. Tiny ducts open at the papilla’s surface, releasing urine into the collecting system. This makes the renal papilla a high-traffic zone for dissolved minerals, and that is exactly why it is ground zero for kidney stone formation.
A key concept in kidney stone research is Randall’s plaque, a deposit of calcium phosphate (hydroxyapatite) that forms within the tissue of the renal papilla itself. These plaques typically start in collagen-rich areas near small blood vessels or the thin loops of the nephron deep within the papilla. When oxidative stress damages collagen fibers in these regions, it produces chemical groups that act as seeds for mineral crystals to nucleate and grow.7PubMed Central. Kidney stones and oxidative stress. Types of papillary renal calculi Over time, the plaque can erode through the papilla’s surface and become the foundation on which a full-blown kidney stone builds.
When researchers have examined renal papillae directly using tiny cameras during surgery, they have found that roughly three-quarters of stone-forming patients show visible tubular calcification on the papillary surface, and more than half show Randall’s plaque.8PubMed Central. Relationship of endoscopic lesions of the renal papilla with type of renal stone and 24 h urine analysis The extent of plaque coverage correlates with urine chemistry: higher calcium excretion and lower urine volume independently predict greater plaque coverage on the papilla. In people who form calcium oxalate stones, mean plaque coverage was roughly fifteen times greater than in non-stone-formers.9PubMed. Urine calcium and volume predict coverage of renal papilla by Randall’s plaque This is one reason urologists emphasize staying well hydrated: diluting the urine reduces the mineral concentration at the papillary surface and may slow plaque formation.
Papillary Muscles in the Heart
The term “papillary” also shows up in cardiology. Papillary muscles are small, cone-shaped columns of muscle inside the heart’s ventricles. They attach to the edges of the mitral and tricuspid valves via thin cords called chordae tendineae, sometimes nicknamed the “heartstrings.” When the ventricles contract to pump blood, the papillary muscles contract at the same time, pulling the valve leaflets taut so they do not flip backward. Without this tethering, blood would leak back into the atria with every heartbeat.10Cardiovascular Pathology. Morphology of the papillary muscles and the chordae tendineae of the ventricles of adult human hearts
One interesting detail about papillary muscles is that they do not attach directly to the solid wall of the heart. Imaging studies have shown that the base of each papillary muscle is embedded in a meshwork of muscular strands (trabeculae) rather than in the compact myocardium.11PubMed. Papillary muscles do not attach directly to the solid heart wall This architecture has practical implications in surgery and in understanding why a heart attack that damages the base of a papillary muscle can cause sudden, severe valve leakage. If blood supply to that trabecular network is cut off, the muscle can rupture, and the valve leaflet it was holding in place flops open.
Dental Papillae and Tooth Development
During embryonic development, every tooth begins as a bud of tissue with two main components: an outer cap of epithelial cells and an inner mass of connective tissue cells called the dental papilla. The dental papilla eventually gives rise to the dentin (the hard tissue that makes up the bulk of a tooth) and the pulp (the soft, nerve-rich center). The cells that produce dentin, called odontoblasts, differentiate from dental papilla cells, but only when they receive the right signals from the overlying epithelium.12PubMed. Differentiation potential of dental papilla, dental pulp, and apical papilla progenitor cells Without that cross-talk, papilla cells on their own do not become odontoblasts.
Recent research has begun to map the specific molecular signals involved. One pathway uses a protein called AKT, which is activated in the dental epithelium and then triggers a cascade that ultimately promotes odontoblast differentiation in the underlying papilla cells. The epithelial cells secrete a collagen molecule that acts as a messenger, boosting AKT signaling in the dental papilla and driving dentin production.13PubMed. AKT from dental epithelium to papilla promotes odontoblast differentiation Nitric oxide also plays a role in this differentiation process.14PubMed. Expression of nitric oxide synthases in rat odontoblasts and the role of nitric oxide in odontoblastic differentiation of rat dental papilla cells This work matters because understanding how dental papilla cells become functional tooth-building cells is a stepping stone toward regenerative dentistry, the still-distant goal of growing replacement teeth from stem cells.
Interdental Papillae in the Gums
If you look at your gums between your teeth, the small triangular points of tissue filling the gaps are called interdental papillae. They are a purely soft-tissue structure, gum tissue that naturally fills the space between adjacent teeth. When these papillae are healthy and full, they create a seamless line of pink tissue along the gum margin. When they recede, the result is a “black triangle,” a visible dark gap at the base of the teeth that many people find cosmetically bothersome.
Beyond appearance, lost interdental papillae create real functional problems. Food gets trapped in the open space, plaque accumulates more easily, and the exposed root surfaces become more vulnerable to decay. Interdental papilla recession tends to increase with age and is common in people with periodontal disease. Rebuilding a lost papilla is notoriously difficult because these tiny projections have limited blood supply, which makes surgical reconstruction unpredictable.15PubMed Central. Interdental papilla recession and reconstruction of the lost triangle: a review of the current literature Dentists sometimes use injectable fillers, grafting techniques, or orthodontic repositioning to try to coax the tissue back, but results vary widely.
Papillae in the Eye
Two unrelated structures near the eye carry the papilla label. The optic disc, where the optic nerve enters the back of the eye, is sometimes called the optic papilla. It is the one spot on the retina with no photoreceptors, creating the natural blind spot in each eye. When pressure inside the skull rises abnormally, the optic disc can swell, a condition called papilledema. Because the optic nerve is surrounded by cerebrospinal fluid, increased intracranial pressure gets transmitted directly to the disc, causing it to bulge forward.16Cureus. Optic Disc Edema and Elevated Intracranial Pressure (ICP): A Comprehensive Review of Papilledema Doctors check for papilledema during routine eye exams because it can be an early visible sign of serious conditions like brain tumors, meningitis, or idiopathic intracranial hypertension.
The second eye-related papilla is the lacrimal papilla, the tiny raised bump on the inner edge of each eyelid where the tear drainage opening (punctum) sits. Tears flow across the eye surface, collect in the inner corner, and drain through the punctum into a small channel (canaliculus) that leads to the nose. Measurements using imaging have defined the lacrimal papilla’s anatomy in terms of external and internal punctal diameter and the depth of the vertical channel beneath.17PubMed Central. Morphological analysis of lacrimal punctum using anterior segment optical coherence tomography in different age groups If the lacrimal papilla shifts out of its normal position, as can happen when the lower eyelid becomes loose with age, the punctum no longer sits where tears collect, and drainage is impaired. Studies of patients with involutional entropion have found that correcting the eyelid’s horizontal laxity can reposition the punctum but may paradoxically increase tearing initially because the mechanics of tear drainage are disrupted during healing.18PubMed Central. Changes in Lacrimal Punctum Position and Tear Meniscus Height after Correction of Horizontal Laxity in Involutional Lower Eyelid Entropion
The Major Duodenal Papilla
In the digestive tract, the major duodenal papilla (also called the papilla of Vater) is a small mound on the inner wall of the duodenum, the first section of the small intestine. It marks the spot where the common bile duct and the main pancreatic duct empty their contents into the gut. Bile from the liver and digestive enzymes from the pancreas both pass through this single opening. Surrounding the papilla is the sphincter of Oddi, a ring of muscle that controls the timing and flow of these secretions. The sphincter maintains a high-pressure zone with rhythmic contractions, relaxing to allow bile and pancreatic juice through when food arrives in the duodenum and tightening between meals to prevent intestinal contents from backing up into the ducts.19JAMA Internal Medicine. The Human Sphincter of Oddi: Physiology and Pathophysiology When this sphincter malfunctions, it can cause pain, pancreatitis, or obstructive jaundice.
Rumen Papillae in Animals
If you have ever wondered how a cow extracts nutrients from grass, papillae are a big part of the answer. The inner lining of the rumen, the largest compartment of a ruminant’s stomach, is covered in thousands of finger-like papillae that dramatically increase the surface area available for absorbing volatile fatty acids produced by microbial fermentation. These rumen papillae are not present at birth in any meaningful size. Their growth is stimulated by the solid feed the animal begins eating, specifically by the short-chain fatty acids that rumen microbes produce when they break down plant material. Butyric acid appears to be a particularly strong driver of papillary growth, working both through hormonal signals and through direct effects on gene expression in the papillary cells.20PubMed Central. Postnatal Growth and Development of the Rumen: Integrating Physiological and Molecular Insights Dairy farmers manage weaning schedules partly around this biology, introducing grain early so that rumen papillae develop enough for the calf to absorb nutrients efficiently on its own.
Papillae on Plant Surfaces
Plants have papillae too, though the structures are quite different from their animal counterparts. On the petals of many flowers, each epidermal cell bulges outward into a cone-shaped papilla. These conical cells do several things at once. Research on snapdragon flowers using mutant lines that lack the conical shape has shown that the papillae enhance color intensity by focusing light into the pigment-containing cells, raise petal temperature slightly, improve the grip for visiting pollinators, and make the petal surface weakly water-repellent.21PLOS ONE. Determining the Contribution of Epidermal Cell Shape to Petal Wettability Using Isogenic Antirrhinum Lines That last property helps petals shed rain, which keeps pollen dry and available for pollinators.
On leaves, papillae play an even more dramatic role in water repellency. Rice leaves are famously superhydrophobic, meaning water beads up and rolls off almost instantly, carrying dirt and pathogens with it. This self-cleaning ability depends on papillae. Studies on rice mutants that produce normal waxy coatings but fail to develop papillae have shown that wax alone is not enough: without papillae, the leaf surface cannot achieve a contact angle above 150 degrees, the threshold for superhydrophobicity.22PubMed Central. Structural, genetic, and adaptive basis of superhydrophobicity in rice leaves The papillae create a rough micro-texture that traps air pockets beneath water droplets, preventing them from spreading and clinging to the surface. Engineers studying self-cleaning coatings and water-harvesting materials have looked to these plant papillae as models for biomimetic design.
Papillae in Disease
Because papillae appear in so many organ systems, they show up in a wide range of clinical conditions. Papilledema, the swelling of the optic disc papilla described earlier, is a red-flag finding that prompts urgent investigation for elevated intracranial pressure. In the kidney, the visible state of renal papillae during endoscopy can help urologists predict stone recurrence and tailor prevention strategies. Tongue papillae can become inflamed or enlarged in conditions ranging from vitamin deficiencies to scarlet fever, where a characteristic “strawberry tongue” results from swollen fungiform papillae poking through a white coating.
Papillomatosis, the overgrowth of papillae-like projections, is a hallmark of several conditions. In the skin, certain strains of human papillomavirus cause common warts, which are characterized by excessive growth of epidermal papillae along with thickened outer layers of skin.23IntechOpen. Clinical Manifestations of the Human Papillomavirus The name “papillomavirus” itself derives from the papilla-like surface projections these viruses produce. In the larynx, recurrent respiratory papillomatosis involves warty growths on the vocal cords that can obstruct the airway and require repeated surgical removal. These are fundamentally different diseases, but they share the same underlying tissue pattern: an abnormal multiplication of papillary projections where they do not belong or in quantities that interfere with function.
Even the gingival papillae between teeth become a focus in periodontal disease. As bone and attachment loss progress, the interdental papillae shrink away, exposing root surfaces and creating spaces that are difficult to clean. This loss is often one of the first visible signs of advancing gum disease that patients notice on their own, well before pain or tooth looseness develops. Monitoring the height and fullness of interdental papillae is a routine part of dental examinations for that reason.