Lymphatic System and Immunity: Key Concepts and Components

Edema

Occurs when excess interstitial fluid is not returned to bloodstream due to lymphatic failure

Lymphatic system definition

A network of tissues, vessels, and organs

3 functions of lymphatic system

Maintain fluid balance; absorb dietary fats; defend against infection

Lymph

Fluid in lymphatic system formed from interstitial fluid

Amount of lymph in tissues

About 3 liters

Major lymphatic components

Lymph; vessels; tissues; organs

Lymph composition

Water, proteins, electrolytes, WBCs, fats (sometimes)

Lymph vs plasma

Similar but less protein

Origin of lymph

Extracellular fluid entering lymphatic capillaries

Route of lymph flow

Capillaries → vessels → trunks → ducts → subclavian veins

Lymphatic vessels structure

3 layers like veins

Lymph movement

Skeletal muscle pump; breathing; valves; vessel contraction

Cisterna chyli

Beginning of thoracic duct; collects lymph

Right lymphatic duct

Drains right head, arm, thorax → right subclavian vein

Thoracic duct

Drains rest of body → left subclavian vein

Lumbar trunk

Drains lower limbs and pelvis

Intestinal trunk

Carries fat-rich lymph (chyle)

Bronchomediastinal trunk

Drains thoracic organs

Subclavian trunk

Drains arms

Jugular trunk

Drains head and neck

Primary lymphatic organs

Bone marrow and thymus

Secondary lymphatic organs

Lymph nodes, spleen, tonsils

Thymus function

T cell maturation

Lymph node function

Filters lymph and activates B and T cells

Afferent vessels

Carry lymph into node

Efferent vessels

Carry lymph out of node

Tonsils function

Trap pathogens entering mouth and nose

Spleen function

Filters blood; removes old RBCs; stores blood

Innate immunity

Fast, nonspecific, no memory

Adaptive immunity

Slow, specific, has memory

Humoral immunity

B cells produce antibodies

Cell-mediated immunity

T cells attack infected cells

Antigen

Molecule that triggers immune response

Antibody

Protein that binds to antigen

Epitope

Specific binding site on antigen

Hapten

Small molecule that must bind host protein to trigger response

Neutrophil function

Phagocytosis and respiratory burst

Respiratory burst

Release of toxic chemicals to kill pathogens

Basophil function

Release histamine, heparin, leukotrienes

Eosinophil function

Fight parasites and worms

NK cells

Natural killer cells that kill cancer/infected cells

Monocytes

Largest WBC; become macrophages

Macrophages

Phagocytosis and activate T cells

Interferons

Protect neighboring cells from viral infection

Complement system

Group of proteins that destroy pathogens

Inflammation signs

Redness, swelling, heat, pain

Cytokines

Proteins that regulate immune response

Opsonization

Coating pathogens for easier phagocytosis

Cytolysis

Cell bursting

MAC attack

Pore formation leading to cell death

Pyrexia

Fever

Normal body temperature

98.6°F (37°C)

Reye syndrome

Serious disorder in children after viral infection + aspirin

Proteinuria

Protein in urine

Hematuria

Blood in urine

Dysuria

Painful urination

Natural active immunity

Immunity from infection

Natural passive immunity

Maternal antibodies (e.g. breast milk)

Artificial active immunity

Vaccines

Artificial passive immunity

Injected antibodies

Cytotoxic T cells

Kill infected cells using perforins and granzymes

Helper T cells

Activate immune response

Regulatory T cells

Prevent autoimmunity

Memory T cells

Long-term immunity

Hypersensitivity Type I

Immediate allergic reaction (IgE, histamine)

Hypersensitivity Type II

Cytotoxic reaction (IgG/IgM)

Hypersensitivity Type III

Immune complex deposition

Hypersensitivity Type IV

Delayed T-cell response

Autoimmune disease

Immune system attacks self

Respiratory system function

Gas exchange; protection; voice; smell; pH balance

Conducting zone

Air passage only

Respiratory zone

Gas exchange occurs

Nasal cavity function

Warms, humidifies, filters air

Nasal conchae

Increase surface area and turbulence

Goblet cells

Produce mucus

Cilia

Move mucus and debris

Pharynx

Passage for air and food

Epiglottis

Prevents food entering airway

Trachea

C-shaped cartilage keeps airway open

Right lung lobes

3

Left lung lobes

2

Hilum

Entry point of lungs

Primary bronchi

Enter lungs

Secondary bronchi

Supply lung lobes

Tertiary bronchi

Supply lung segments

Terminal bronchioles

End of conducting zone

Respiratory bronchioles

Start of respiratory zone

Alveoli

Site of gas exchange

Type I alveolar cells

Gas exchange; most surface area

Type II alveolar cells

Produce surfactant

Pneumothorax

Air in pleural space causing lung collapse

Boyle's law

↑ volume = ↓ pressure

Charles' law

↑ temperature = ↑ volume

Oxygen transport

Bound to hemoglobin

CO2 transport

Bicarbonate (main), carbaminohemoglobin, dissolved

Pulmonary compliance

Ease of lung expansion

COPD

Chronic obstructive pulmonary disease

Chronic bronchitis

Inflammation with mucus buildup

Emphysema

Alveoli destruction

Kidney functions

Filter blood; regulate BP, electrolytes, pH