M01.02.035 The Lacrimal Gland

The lacrimal glands are serous exocrine glands responsible for secreting lacrimal fluid, which cleans, nourishes, and lubricates the eye. Excess production of this fluid forms tears. Understanding the lacrimal glands’ anatomy, neurovascular supply, and clinical conditions is essential for USMLE Step 1 preparation.

Anatomical Location

Position: Anteriorly in the superolateral aspect of the orbit, within the lacrimal fossa of the frontal bone.
Relations:
- Superior: Zygomatic process of the frontal bone
- Anterior: Orbital septum
- Posterior: Orbital fat
- Inferolateral: Lateral rectus muscle

Structure	Relation
Superior	Zygomatic process
Anterior	Orbital septum
Posterior	Orbital fat
Inferolateral	Lateral rectus muscle

Anatomical Structure

The lacrimal gland is approximately 2 cm long and consists of two parts:

Orbital: Larger, located on the lateral margin of the levator palpebrae superioris muscle.
Palpebral: Smaller, situated along the inner surface of the eyelid.

Part	Description
Orbital	The smaller, inner surface of the eyelid
Palpebral	Smaller, inner surface of the eyelid

Histology: The gland is a compound tubuloacinar gland composed of lobules, each containing acini with serous cells that produce watery lacrimal fluid.
Secretion Pathway: Lacrimal fluid is released into excretory ducts, emptying into the superior conjunctival fornix, and spread over the cornea during blinking.

Lacrimal Apparatus

The lacrimal apparatus facilitates the drainage of lacrimal fluid from the orbit.

Flow of Lacrimal Fluid:
- Secretion: Circulates across the eye surface.
- Accumulation: Collects in the lacrimal lake (medial canthus).
- Drainage: Travels via lacrimal canals to the lacrimal sac.
Nasolacrimal Duct:
- Location: Runs in a groove formed by the lacrimal bone and maxilla.
- Function: Drains fluid into the inferior meatus of the nasal cavity.

Component	Function
Lacrimal Lake	Collects fluid at the medial canthus
Lacrimal Sac	Dilated end of the nasolacrimal duct
Nasolacrimal Duct	Empties into the nasal cavity

Neurovascular Supply

Vasculature

Arterial Supply: Lacrimal artery (branch of the ophthalmic artery).
Venous Drainage: Superior ophthalmic vein → Cavernous sinus.
Lymphatic Drainage: Superficial parotid lymph nodes → Superior deep cervical nodes.

Innervation

Sensory: Lacrimal nerve (branch of ophthalmic nerve).
Autonomic:
- Parasympathetic:
  - Preganglionic fibers: Greater petrosal nerve (facial nerve).
  - Synapse: Pterygopalatine ganglion.
  - Function: Stimulates lacrimal fluid secretion.
- Sympathetic:
  - Fibers: Superior cervical ganglion → Internal carotid plexus.
  - Function: Inhibits fluid secretion.

Nerve Type	Route	Function
Sensory	Lacrimal nerve	Provides sensation
Parasympathetic	Greater petrosal → Pterygopalatine ganglion	Stimulates secretion
Sympathetic	Superior cervical ganglion → Deep petrosal	Inhibits secretion

Clinical Relevance

Dacryoadenitis

Definition: Inflammation of the lacrimal glands.
Types:
- Acute: Caused by viral (e.g., mumps, Epstein-Barr virus) or bacterial (e.g., staphylococcus) infections.
- Chronic: Associated with inflammatory conditions like sarcoidosis or Graves’ disease.

Type	Cause	Features
Acute	Viral/Bacterial infection	Pain, swelling, excess tearing
Chronic	Non-infectious inflammation (e.g., Graves’)	Swelling, potential visual impairment

Treatment:
- Viral: Rest and warm compresses.
- Non-viral: Treat the underlying cause.

Points to Remember

The lacrimal gland secretes lacrimal fluid, essential for ocular lubrication and nourishment.
It has two main parts: orbital (larger) and palpebral (smaller).
Parasympathetic innervation stimulates secretion, while sympathetic innervation inhibits it.
Dacryoadenitis is an important clinical condition to diagnose and manage effectively.

Bibliography

TeachMeAnatomy: Lacrimal Gland Overview (2024).
Gray’s Anatomy for Students, 4th Edition.
Clinical Ophthalmology by Jack J. Kanski.

M01 Human Anatomy

Curriculum