Lymphatic and Immune System Anatomy
Complete anatomy of the lymphatic system - lymph vessels, lymph nodes, spleen, thymus, tonsils, and MALT. Immune cell development, circulation, and surveillance.
This content is for informational purposes only. Always consult a healthcare professional.
Components
Component
Structure
Function
Lymph
Interstitial fluid (transported)
Return proteins, remove waste
Lymphatic vessels
Thin-walled, valves
Conduit for lymph
Lymph nodes
Bean-shaped filters (600 total)
Filtration, immune activation
Spleen
Large lymphoid organ
Blood filtration, immune response
Thymus
Mediastinal lymphoid organ
T cell maturation
Tonsils
Pharyngeal lymphoid tissue
Mucosal immunity
MALT
Mucosa-associated lymphoid tissue
Mucosal immunity
Peyer patches
Intestinal lymphoid follicles
Gut immunity
Lymphatic Vessels
Type
Description
Lymph capillaries
Blind-ended, overlapping endothelial cells (flaps)
Collecting vessels
Valves, smooth muscle (lymphangions)
Lymph nodes
Interposed along collecting vessels
Lymphatic trunks
9 major trunks (jugular, subclavian, bronchomediastinal, lumbar, intestinal)
Lymphatic ducts
Thoracic duct (left), right lymphatic duct
Thoracic duct:
Origin: Cisterna chyli (L1-L2)
Course: Through aortic hiatus → right of midline → crosses left at T5 → empties into left jugulosubclavian junction
Drains: Lower body, left upper body, left head/neck
Length: 38-45 cm
Right lymphatic duct:
Drains: Right upper body, right head/neck
Length: 1-2 cm
Lymph Nodes
Feature
Description
Number
500-600 (concentrated in neck, axillae, groin, mediastinum, abdomen)
Size
1-25 mm
Structure
Cortex (B cells, follicles), paracortex (T cells), medulla (plasma cells, sinuses)
Afferent vessels
Multiple (enter at capsule)
Efferent vessel
Single (exit at hilum)
Blood supply
High endothelial venules (HEV) - lymphocyte entry
Major Lymph Node Groups
Region
Groups
Drainage
Head and neck
Submental, submandibular, deep cervical, supraclavicular
Face, oral cavity, scalp, thyroid
Upper limb
Axillary (5 groups: pectoral, subscapular, humeral, central, apical)
Upper limb, breast
Thorax
Mediastinal, hilar, tracheobronchial
Lungs, esophagus, heart
Abdomen
Paraaortic, celiac, mesenteric
GI tract, kidneys, liver
Pelvis
Iliac (common, external, internal), sacral
Pelvic organs
Lower limb
Inguinal (superficial, deep), popliteal
Lower limb, perineum, abdominal wall
Spleen
Feature
Description
Location
Left upper quadrant (RUQ)
Size
12 × 7 × 4 cm
Weight
150-200 g
Hilum
Splenic artery, vein, lymphatics
Relations
Diaphragm (superior), stomach (medial), left kidney (posterior), colon (inferior)
Structure:
Region
Function
Capsule
Fibrous, smooth muscle (contractile)
White pulp
Periarteriolar lymphatic sheaths (PALS - T cells), follicles (B cells)
Marginal zone
Between white and red pulp
Red pulp (sinusoids, cords)
Filtration of aging RBCs, iron recycling
Functions: Filtration, immune response (IgM production), extramedullary hematopoiesis (fetal/in disease), RBC storage (10-15% in dogs, minimal in humans)
Thymus
Feature
Description
Location
Superior mediastinum (behind sternum)
Size
Largest in infancy (30-40 g), involutes (10-15 g in adult)
Structure
Cortex (immature T cells), medulla (mature T cells, Hassall corpuscles)
Function
T cell maturation (positive and negative selection)
Tonsils
Type
Location
Crypts
Palatine (2)
Between palatoglossal and palatopharyngeal arches
Deep crypts
Pharyngeal (adenoid)
Nasopharynx (roof)
No crypts
Lingual
Base of tongue
Crypts
Tubal
Near Eustachian tube opening
Small
Waldeyer ring: Ring of lymphoid tissue around the pharynx (all four tonsil types)
MALT (Mucosa-Associated Lymphoid Tissue)
Type
Location
Function
GALT (gut-associated)
Lamina propria, Peyer patches, appendix
IgA production, oral tolerance
BALT (bronchus-associated)
Airways
Respiratory immunity
NALT (nose-associated)
Nasal mucosa
Upper respiratory immunity
LALT (larynx-associated)
Larynx
Laryngeal immunity
Immune Cells
Cell
Lineage
Function
B lymphocyte
Bone marrow
Antibody production (humoral)
T lymphocyte
Thymus
Cell-mediated immunity
Helper T (CD4+)
Thymus
Cytokine production, B cell help
Cytotoxic T (CD8+)
Thymus
Kill infected cells
NK cell
Bone marrow
Innate killing
Macrophage
Monocyte
Phagocytosis, antigen presentation
Dendritic cell
Bone marrow
Antigen presentation (most efficient)
Neutrophil
Bone marrow
Phagocytosis (first responder)
Lymphatic Drainage Patterns
Region
Primary Drainage
Important Nodes
Breast
Axillary (75%), internal thoracic (25%)
Level I-III axillary
Lung
Hilar, mediastinal
Station 1-14
Stomach
Celiac, perigastric
D1-D2
Colon
Epicolic, paracolic, intermediate, principal
Named by artery
Rectum
Lower 1/3 to inguinal, upper 2/3 to internal iliac
—
Prostate
Obturator, internal iliac
—
Testis
Paraaortic (L1-L2)
—
Ovary
Paraaortic
—
Uterus (cervix)
Internal iliac, obturator
—
Uterus (fundus)
Paraaortic
—
Skin (upper)
Axillary
—
Skin (lower)
Inguinal
—
Scalp
Superficial parotid, occipital, deep cervical
—
Tongue
Submental, submandibular, deep cervical (jugulodigastric)
—