Smallest facial bone explained: lacrimal bones are smaller than nasal bones

The lacrimal bone: anatomy and location

Each of the two lacrimal bones is roughly the size and shape of a postage stamp: thin, fragile, and scale-like. They sit in the orbit on the medial wall, just behind the nasal bone and below the lacrimal fossa of the frontal bone. Together with other orbital bones, the lacrimal bones form the medial wall of the eye socket.

Anatomically, the lacrimal bone is the smallest of the 14 facial bones by total area and thickness. This is a measurable fact: compare the dimensions of a lacrimal bone to a nasal bone, a zygomatic bone, or a maxilla in any standard anatomy text, and the lacrimal comes out smallest.

The lacrimal bone has a single major groove running along its medial surface: the nasolacrimal groove. This groove is the roof of the nasolacrimal duct, which drains tears from the lacrimal sac down into the nasal cavity. During eye exams, ophthalmologists can probe this duct and radiographers may see contrast in the nasal cavity during a dacryocystography study.

Because the lacrimal bone is so thin and sits deep in the orbit, it is rarely fractured in isolation. But when orbital trauma occurs, the lacrimal bone can be shattered, and fractures here can impair tear drainage and lead to infection of the lacrimal sac (dacryocystitis).

The common wrong answer (and why it sticks)

The wrong answer many students encounter is “nasal bones are the smallest.” This is in some older textbooks, some online prep platforms, and even some study guides labeled “ARRT-approved.” It’s wrong.

Why does it stick? Three reasons:

1. External visibility. The nasal bones are externally visible on the nose. You can feel them when you touch your nose. They seem prominent and “real” in a way the lacrimal bones do not, because the lacrimal bones are hidden deep in the orbit, behind the nasal bone.

2. Intuitive naming. Students see “nasal” and think “nose,” then think “the nose is small,” so “nasal bones must be small.” But the actual nasal bones are not the smallest; they are just small and visible.

3. Outdated references. Some older anatomy and radiography texts incorrectly list the nasal bones as the smallest. Once a wrong answer gets into a few textbooks, it gets copied into prep materials, and it persists even after more authoritative sources correct it.

The ARRT follows the current standard anatomy definition used in Bontrager’s Textbook and supported by Radiopaedia: the lacrimal bones are the smallest facial bones.

All 14 facial bones, ranked by size

Here are all 14 facial bones, roughly ranked from largest to smallest:

1. Mandible (unpaired), The largest facial bone. Horseshoe-shaped lower jaw.
2. Maxillae (2), Upper jaw. Form the anterior and lateral walls of the nasal cavity.
3. Zygomatic bones (2), Cheekbones. Form the lateral orbital wall.
4. Palatine bones (2), Form the posterior hard palate.
5. Vomer (unpaired), Thin, forms the posterior nasal septum.
6. Nasal bones (2), Form the bridge of the nose, externally visible.
7. Inferior nasal conchae (2), Scroll-like bones inside the nasal cavity, increase surface area for air conditioning.
8. Lacrimal bones (2), Smallest. Thin, scale-like, medial orbital wall.

This ranking is approximate because the actual size depends on how you measure (length, width, thickness, or total area). But by any reasonable anatomic measure, the lacrimal bones come in at smallest.

Why the ARRT tests this distinction

The ARRT Radiography Boards test facial bone anatomy for a practical reason: radiographers and radiologic technologists must identify orbital and facial structures in radiographs, CT scans, and other imaging. Accuracy matters in clinical reporting.

The lacrimal bone question specifically is a teaching point because it separates true anatomic knowledge from surface-level memorization. It tests whether you have actually studied the anatomy, not just skimmed a list. A student who can say “the lacrimal bone is the smallest and it forms part of the medial orbital wall” demonstrates understanding. A student who guesses “nasal bones” does not.

On the ARRT, the question usually appears in one of three formats:

1. Direct recall: “Which bone is the smallest of the 14 facial bones?”
2. Image labeling: You are shown an axial CT of the orbits and asked to identify the lacrimal bone.
3. Multi-part anatomy: A question about orbital anatomy that lists the lacrimal bone and asks you to confirm or deny a fact about it.

If you have been studying from a source that taught “nasal bones are smallest,” make the correction now. The ARRT treats the lacrimal bone as smallest.

Clinical relevance: orbital trauma and dacryocystitis

From a clinical standpoint, the lacrimal bone matters because of two conditions:

Orbital fractures

The lacrimal bone is the thinnest orbital bone and the easiest to fracture from blunt trauma. A punch to the eye, a fall, or a car accident can fracture the lacrimal bone and the thin medial orbital wall (sometimes called an “orbital blowout fracture”). When the lacrimal bone breaks, fragments can disrupt the nasolacrimal duct and cause tearing (excessive tears), tearing of the globe, or secondary infection.

Dacryocystitis

The lacrimal sac (where tears are stored) empties into the nasolacrimal duct, which runs through the groove in the lacrimal bone and down through the inferior nasal meatus. If the duct is blocked (by tumor, scar tissue from a fracture, or infection), tears back up and the sac becomes infected. This is dacryocystitis. A radiographer may see swelling of the lacrimal sac on CT or MRI.

In both cases, understanding the anatomy of the lacrimal bone and its role in tear drainage is clinically essential. Radiographers who can accurately identify the lacrimal bone and report abnormalities there are providing important diagnostic information.

Quick reference table

Bone	Count	Size rank	Location	Clinical note
Lacrimal	2	1 (smallest)	Medial orbital wall	Smallest, fragile, tear drainage groove
Inferior nasal conchae	2	2	Nasal cavity, scroll-shaped	Air conditioning, surface area
Nasal	2	3	Nose bridge, externally visible	Often wrongly cited as smallest
Vomer	1	4	Posterior nasal septum	Unpaired, thin
Palatine	2	5	Hard palate, posterior	Forms hard palate with maxillae
Zygomatic	2	6	Cheekbones, lateral orbit	Lateral orbital wall, cheekbone prominence
Maxillae	2	7	Upper jaw	Largest pair, anterior nasal cavity wall
Mandible	1	8 (largest)	Lower jaw	Largest facial bone, unpaired

ARRT exam tip

If you only memorize one thing from this page: the lacrimal bones are the smallest of the 14 facial bones, not the nasal bones. The lacrimal bones are thin, scale-like, and located on the medial orbital wall. The nasal bones are externally visible, which is why many people and many outdated study materials wrongly cite them as the smallest.

Memorize the lacrimal bone by location and function, not just by name. Know that it sits in the medial orbit, that it has the nasolacrimal groove for tear drainage, and that it is the smallest facial bone. When you see that on the ARRT, you will have the right answer.

For a deeper dive into skull and facial anatomy, orbital imaging, and cranial positioning, see our chapter on skull, face, and TMJ. For a complete overview of radiographic procedures and how facial anatomy relates to different x-ray positions, the guide on ARRT procedures walks through positioning for every major facial projection.