BLOOD

The Cardiovascular System:blood in context

Function of C.V.S. is transport/distribution/circulation

Transport requires:

1. Medium of transport: a substance in which material are transported

• BLOOD

2. Pressure to propel/deliver blood• HEART

• heart both generates and can regulate blood pressure

3. VESSELS for blood to move through• vessels both distribute blood and regulate blood pressure

Functions of Blood• Transport

– nutrients

– O2, CO2 (gasses)

– wastes– hormones/regulatory substances– heat

• Immune response• pH regulation• Hemostasis: clot formation/patching of vessel

leaks

Composition of Blood

Plasma:components and function

Plasma: “liquid” portion of blood• ~55% of blood by volume (on average)Components• ~91% of plasma is water

– the most abundant substance in blood– important contributor to blood volume

• Related to state of hydration/water balance• (which relates to ability to maintain blood pressure)

• ~7% Plasma Proteins– Albumin (58% of p.p.): helps maintain water within vessels/plasma

• Also transports substances through blood

– Globulins (38% of p.p.): • Transport (often of non-water soluble substances)• immune function/response--antibodies

– Fibrinogen (4% of p.p.): blood clotting• Other solutes— ~2% of plasma

Formed Elements

Composition

• ~ 95% RBC’s/Erythrocytes

• 4%+ Platelets

• <1% WBC’s/Leukocytes

Erythrocyte Functions

• Transport (carry) oxygen – 98.5% of all oxygen

• Transport carbon dioxide– ~20%

• Picks up oxygen in lungs; unloads it in tissues of systemic circuit

• Picks up carbon dioxide in tissues of systemic circuit; unloads it in the lungs

Erythrocyte Functions:Gas Transport

• Oxygen and Carbon Dioxide are carried on (bound to) hemoglobin– makes up about 1/3rd of cells internal volume

• Hemoglobin is a large protein with 4 basic subunits each with an iron containing heme group

– O2 in carried on/bound to the heme portion of Hb

– CO2 is carried on/bound to the globin portion of Hb

Erythrocyte Structure/Specializations

1. Biconcave shape– increases surface area– Center of cell close to PM (diffusion distance is short)

– faster/more efficient movement of O2 & CO2 across the

PM of cell

– Together with a flexible cytoskeleton creates flexibility (RBC’s have a particularly flexible cytoskeleton) to pass through very small capillaries

– facilitates rouleaux (stacking) under some conditions

Erythrocyte Structure/Specializations

1. Biconcave shape

2. No nucleus– more room for Hb more gas carrying

capacity– BUT, limits cell’s life span

• ~ 120 days• body must balance the creation of new and removal

of old RBC’s.– (basis for some disorders such as jaundice, possible mechanism for anemia, etc….)

Erythrocyte Structure/Specializations

1. Biconcave shape

2. No nucleus

3. No mitochondria (or most organelles)– more room for Hb more transport

capacity– does not use the oxygen it transports

Erythrocyte Formation and removal

• Produced in red bone marrow• Production is stimulated primarily by

erythropoitin (EPO), released by kidney (& liver)

• Old RBC’s are removed from blood by spleen and liver

• Macrophages destroy RBC’s

RBC Factoids

• ~2.4 million new erythrocytes are produced per second in human adults.

• Each circulation around body takes about 20 seconds.

• 25% of all cells in the human body are red blood cells.

LEUKOCYTE FUNCTION: SEE TALBE 21.3

Leukocytes Functions

Relative Leukocyte Abundance

• Neutrophils• Lymphocytes• Monocytes• Eosinophils• Basophils

• Never• let• monkeys• eat• bananas

Differential WBC countBecause:• there is a typical amount of each WBC• Each WBC has a different function• WBC respond to their specific challenges

by increasing in number

• Counting the relative abundance of each WBC (differential WBC count) can help assess what a condition/problem is