Updated: 10/2/2018

Secondary Lymphoid Tissue

Review Topic
  • Secondary lymphoid tissue has many important roles in immunity including
    • filtration and sampling of bodily fluids in order to detect infection
    • sequestration of pathogens and ingestion by innate immune cells
    • activation of adaptive immunity by antigen presenting cells
    • maintainance of immunological memory by storage of long lived cells
  • There are several types of secondary lymphoid tissue including the
    • spleen
      • a solid organ in the left upper quadrant of the abdomen
    • lymph nodes
      • a diffuse network of small nodes throughout the body
    • mucosal lymphoid tissue
      • patches of immunological tissue such as
        • Waldeyer's ring consisting of
          • tubular tonsils in the pharyngeal recess
          • palatine tonsils
          • lingual tonsils at the base of the tongue
        • Peyer patches in the lower jejunum and ileum

  • The spleen is located in the left upper quadrant of the abdomen where
    • it is protected by the 9th to 11th ribs
    • it sits anterior to the left kidney
  • There are several components of the spleen, which are divided into
    • white pulp, which is the
      • the immunologically active part of the spleen containing
        • germinal centers containing
          • activated B-cells (part of a larger B-cell follicle)
        • periarteriolar lymphatic sheaths (PALS) containing
          • T-cells
        • marginal zones containing
          • macrophages and other antigen-presenting cells
    • red pulp, which is
      • the hematologically active part of the spleen characterized by
        • arterioles to allow for
          • delivery of red blood cells (RBCs)
        • resident macrophages to ingest both 
          • dying/abnormal RBCs and encapsulated bacteria
        • sinusoids with a fenestrated basement membrane to
          • allow for red RBC exit
  • There are many clinical manifestations of asplenia including
    • increased susceptibility to infections by encapsulated bacteria
    • appearance of abnormal RBC forms on peripheral blood smear
    • others described more fully in the asplenia topic
Lymph Nodes

  • Lymph nodes are a diffuse network of encapsulated lymphoid tissue that
    • have many regional afferent lymphatic vessels
    • have at least one efferent lymphatic
  • There are several components of a lymph node, which are divided intothe
    • cortex
      • an outermost layer of the lymph node that is composed of
        • follicles composed of proliferating B cells that can be
          • dormant and cell dense primary follicles
          • active and pale secondary follicles
        • subcapsular macrophages that monitor incoming lymph
        • dendritic cells that serve as antigen presenting cells
    • paracortex
      • an intermediate layer of the lymph node that is composed of
        • high endothelial vessels (HEVs) where 
          • lymphocytes enter lymph nodes
        • T-cells that await activation, meaning that this region is
          • hypertrophied in infections triggering cellular immunity
          • underdeveloped in patients with DiGeorge syndrome
    • medulla
      • an innermost layer of the lymph node that is composed of
        • cords with closely packed lymphocyte and plasma cell "cords"
        • sinuses that drain into the efferent lymph vessels and house
          • reticular cells
          • macrophages
Lymph Node Drainage Pattern
Lymph Node Drainage Pattern
Lymph Node Cluster
Drainage Area


  • Head
  • Neck


  • Lungs
  • Trachea
  • Esophagus
  • Upper limb
  • Breast
  • Skin above the umbilicus
  • Liver
  • Stomach
  • Spleen
  • Pancreas
  • Upper duodenum
Superior mesenteric
  • Lower duodenum
  • Jejunum
  • Ileum
  • Colon proximal to splenic flexure
Inferior mesenteric
  • Colon between splenic flexure and upper rectum
Internal iliac
  • Lower rectum
  • Anal canal proximal to pectinate line
  • Bladder
  • Cervix
  • Prostate
  • Testes
  • Ovary
  • Kidney
  • Uterus
Superficial inguinal
  • Anal canal distal to pectinate line
  • Skin below the umbilicus
  • Scrotum
  • Vulva
  • Dorsolateral foot
  • Posterior calf



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Questions (2)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2

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Topic COMMENTS (11)
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