Lymph Nodes (Lymphatic Glands)
Small, bean-shaped immune filtration organs positioned along lymphatic vessels throughout the body.
💬 In Plain English
Lymph nodes are tiny, bean-shaped filters scattered throughout your pet’s body that act as military checkpoints for the immune system. They filter lymphatic fluid, trapping bacteria, viruses, and cancer cells so specialized white blood cells (lymphocytes) can destroy them. In a healthy dog or cat, most lymph nodes are tiny, soft, and difficult to feel. But when an infection or lymphoma occurs, the lymph nodes swell up into firm, enlarged lumps. Veterinarians routinely palpate five external pairs: submandibular (under the jaw), prescapular (in front of the shoulders), axillary (armpits), inguinal (groin), and popliteal (behind the knees).
🔬 Clinical & Technical Depth
For Vets & TechniciansFormal Clinical Definition
Encapsulated secondary lymphoid organs situated along lymphatic channels, comprising cortex (B-cell follicles), paracortex (T-cells), and medulla (plasma cells and histiocytes) responsible for immune surveillance and antigen filtration.
Why Veterinarians Use It
Veterinarians palpate peripheral lymph nodes during every routine physical exam and perform fine needle aspirates (FNA) on enlarged nodes.
Clinical Context Encountered
Discussed during wellness exams, skin allergy flare-ups, cancer staging, or lymphoma investigations.
Clinical Reference Guide (Anatomical Structure)
Anatomical Location
Distributed peripherally (submandibular, prescapular, axillary, inguinal, popliteal) and internally (tracheobronchial, mesenteric, sublumbar).
Normal Physiological Function
Filters afferent lymphatic fluid, captures microbial pathogens, and presents antigens to initiate adaptive humoral and cell-mediated immune responses.
🐕 vs 🐈 Species Differences
Cats have smaller, softer, and more mobile peripheral lymph nodes that are harder to palpate in normal health compared to dogs.
- •Rapid, painless, bilateral enlargement of multiple lymph nodes (especially behind the knees and under the jaw) is the classic hallmark of multicentric lymphoma, requiring prompt cytology staging.
❓ Questions to Ask Your Veterinarian
Take these actionable questions with you to your next clinic visit or appointment:
- 1Which specific lymph nodes are enlarged (generalized vs. localized lymphadenopathy)?
- 2Can we perform a quick in-house Fine Needle Aspirate (FNA) cytology to check for lymphoma or reactive infection?
- 3Are internal chest or abdominal lymph nodes enlarged on X-rays or ultrasound?
Academic & Clinical References
- Lymphatic System Anatomy and Lymphadenopathy in Small AnimalsOrganization: Merck Veterinary Manual • Accessed: 2026-01-10https://www.merckvetmanual.com