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M01.02.047 Lacrimal Gland
The lacrimal glands are serous exocrine glands responsible for producing lacrimal fluid, which cleans, nourishes, and lubricates the eye. Excess production forms tears.
This guide explores the anatomical location, structure, vascular and nervous supply, and clinical relevance of the lacrimal glands, with detailed insights for USMLE Step 1 preparation.
Anatomical Location
The lacrimal gland is situated anteriorly in the superolateral orbit, within the lacrimal fossa of the frontal bone.
Anatomical Relations
| Relation | Description |
|---|---|
| Superior | Zygomatic process of the frontal bone |
| Anterior | Orbital septum |
| Posterior | Orbital fat |
| Inferolateral | Lateral rectus muscle |
Anatomical Structure
Size and Division
- Length: ~2 cm
- Parts:
- Orbital: Larger, located near the lateral levator palpebrae superioris muscle.
- Palpebral: Smaller, along the inner eyelid surface.
Microscopic Features
- Type: Compound tubuloacinar gland.
- Structure: Contains lobules formed by multiple acini, which produce watery serous secretions.
Secretion Pathway
- Acini produce lacrimal fluid.
- Fluid enters excretory ducts.
- Ducts empty into the superior conjunctival fornix.
- Blinking spreads fluid across the cornea.
Lacrimal Apparatus
The lacrimal apparatus facilitates the drainage of lacrimal fluid.
| Step | Details |
|---|---|
| Secretion | Fluid spreads across the eye. |
| Accumulation | Collects in the lacrimal lake (medial canthus). |
| Drainage | Via lacrimal sac into the nasolacrimal duct. |
| Termination | Empties into the inferior meatus of the nasal cavity. |
Neurovascular Supply
Vasculature
| Type | Description |
|---|---|
| Arterial Supply | Lacrimal artery (branch of ophthalmic artery). |
| Venous Drainage | Superior ophthalmic vein, draining into the cavernous sinus. |
| Lymphatic Drainage | Drains to superficial parotid lymph nodes and superior deep cervical nodes. |
Innervation
| Type | Pathway |
|---|---|
| Sensory | Lacrimal nerve (branch of the ophthalmic nerve, derived from CN V). |
| Parasympathetic | Greater petrosal nerve → Pterygopalatine ganglion → Maxillary nerve → Zygomatic nerve. Stimulates secretion. |
| Sympathetic | Superior cervical ganglion → Internal carotid plexus → Deep petrosal nerve. Inhibits secretion. |
Clinical Relevance
Dacryoadenitis
Definition: Inflammation of the lacrimal glands.
Types and Causes
| Type | Cause |
|---|---|
| Acute | Viral (e.g., mumps, Epstein-Barr virus) or bacterial (e.g., Staphylococcus, Gonococcus). |
| Chronic | Non-infectious (e.g., sarcoidosis, thyroid eye disease in Graves’ disease). |
Symptoms
- Swelling, pain, and excessive tearing.
- Potential visual impairment due to pressure on the eye.
Management
- Viral causes: Rest and warm compresses.
- Other causes: Treat underlying condition.
Points to Remember
- Location: Superolateral orbit, within the lacrimal fossa.
- Structure: Compound tubuloacinar gland with orbital and palpebral parts.
- Function: Cleans, nourishes, and lubricates the eye.
- Innervation: Both parasympathetic and sympathetic pathways regulate secretion.
- Dacryoadenitis: Recognize and differentiate acute vs. chronic forms.
Bibliography
- TeachMeSeries Ltd (2024). Anatomy of the Lacrimal Glands.
- Gray’s Anatomy for Students (2023).