Blood and Lymph

• Components of Blood– Plasma– Cells—RBC’s, WBC’s,

Platelets• Production and

elimination of blood cells

• WBC’s move in and out of blood

• Role of lymph vessels• Lymph organs

Components of blood—plasma• Plasma is water with dissolved

solutes• 46-63% of blood volume is plasma• Plasma is 92% water• Dissolved proteins make 7%

– Albumins—for osmotic pressure, transport

– Globulins—immune function, transport

– Fibrinogen—clotting– Regulatory proteins/hormones

• Other solutes make 1% including – salts/electrolytes—why important?– organic nutrients (what is included

here?)– Organic wastes (from cellular

respiration and cell breakdown)

Components of blood—cells• Red Blood Cells (RBC’s, erythrocytes): Full of

Hemoglobin (Hb) for oxygen transport• Platelets: Cell pieces important in clotting• White Blood Cells (WBC’s, leukocytes):

Immune function– Neutrophils– Eosinophils– Basophils– Monocytes– Lymphocytes

Red Blood Cells (RBC) Fun Facts• One drop of blood has 250 million RBC’s• Adult human has total of 25 trillion RBC’s—1/3 of all cells in the body• Each RBC lives about 120 days and travels 700 miles. Membrane rupture

or other damage is noticed by phagocytes which then engulf the cell• One percent of RBC’s are replaced each day at a rate of about 3 million per

second• Each RBC contains about 250 million Hb molecules• So, number of Hb molecules in body is about equal to stars in the universe

How old and damaged RBC’s are processed

Blood Cell Production

• RBC production/ only in red bone marrow

• WBC’s begin development in bone marrow

– Monocytes enter bloodstream and complete development into macrophage in peripheral tissues

– Many Lymphoid Stem Cells complete development in lymph tissues (thymus, spleen, lymph nodes)

– Some Band Cells complete development in bloodstream.

Blood Cell Production—focus on lymphocytes (T-cells and B-cells)

– Many Lymphoid Stem Cells complete development in lymph tissues (thymus, spleen, lymph nodes)

Where is immune response needed?

• WBC’s move out of blood to fight infections—immune response

• Some stay in the peripheral tissues as macrophages

• Others move back into blood via lymph vessels (lymphocytes)

• Fluid also leaks from capillaries and can be taken back into bloodstream through lymph vessels

More on immunity coming up…but how do these immune cells (WBC’s) move around the body?

Lymphatic vessels• Open-ended lymph capillaries pick up

interstitial fluid and also WBC’s• Gradual movement through flimsy lymph

vessels takes cells to lymphoid organs• Eventually fluid returns to circulation through

major lymph vessels

• Return of lymph to circulatory system is at subclavian veins• Lymph travels through lymphoid organs: lymph nodes/nodules, thymus, spleen

Lymph nodes• At lymph nodes, lymph is “filtered” by

presence of lymphocytes (B-cells). • Most foreign antigens are removed

from lymph• Incoming (afferent lymph) is from lymph

capillaries—picked up in tissues where infections/foreign invaders might be present

• Outgoing (efferent) lymph is returned to ever larger lymph vessels and then back into blood circulation at subclavian veins

• Presentation of antigens to initiate immune response can also happen in lymph nodes

• Lymph nodes are clustered at sites where blood is returning from major regions of body, like axilla and groin

Lymphoid nodules

• Work much like lymph nodes, but closer to site of potential entry of foreign invaders

• Tonsils, Wall of intestines

Thymus• Site of development of

development and clonal selection of T-cells (more on this later)

• Draped over mediastinum and great vessels

• Much larger early in life through adolescence

• In elder individuals, can be tiny, impossible to see

• Produces hormones that stimulate lymphocyte maturation

Spleen• Left upper

quadrant of abdominal cavity

• Tears/ruptures easily on impact

• Hard to repair, but can be removed with little affect—higher risk of bacterial infection, especially pneumococcal bacteria

• Spleen is site of large concentration of lymphocytes that “filter” blood, much like lymph nodes work on lymph

WBC/Leukocyte function in immunity

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