At high altitudes, hemoglobin's affinity for O₂  is increased because BPG concentrations increase.

Decreases in arterial P_O2  cause the peripheral chemoreceptors to become less responsive to increases in P_CO2 .

When blood O₂ levels decline, the kidneys produce more erythropoietin, which stimulates breakdown of red blood cells in the spleen.

High-altitude conditions always result in lower-than-normal hemoglobin saturation levels because less O₂  is available to be loaded.

Surface barrier → Adaptive → Innate

Innate → Surface barrier → Adaptive

Innate only

Adaptive → Innate → Surface barrier

Surface barrier → Innate → Adaptive

IgE

IgA

IgD

IgM

IgG

Intrapulmonary pressure drops

Diaphragm descends, thoracic volume begins to increase, and rib cage rise

Thoracic cavity volume decreases

Air (gases) flows into lungs

Removal of aged erythrocytes

Antibody production

Complement synthesis

Antigen presentation only

T cell education

mucosa-associated lymphoid tissue (MALT)

spleen

thymus

lymph nodes

The splenic artery and vein enter and exit the spleen at the hilum.

Site for production of the fetal erythrocytes. 

Red pulp is where immune functions take place.

Clusters of white pulp look like islands in a sea of red pulp.

The spleen is the largest lymphoid organ.

Activation of both humoral and cellular immunity

Complement-mediated lysis

Direct killing of infected cells

Phagocytosis

Antigen neutralization

T cell differentiation     

Antigen presentation

Collecting circulating antigen   

B cell division