Objective 3-4: Formed Elements & Red Blood Cells

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Chapter 11
The Cardiovascular System: Blood
Anatomy & Physiology
• “The living body is in constant communication
with it’s external environment. Nutrients are
absorbed through the lining of the digestive tract,
gases move across the epithelium of the lungs,
and wastes are excreted in the feces and urine.
Even though these chemical exchanges occur at
specialized sties, they affect every cell, tissue, and
organ in a matter of moments because all parts of
the body are linked by the cardiovascular system,
an internal transport network.” (p. 365)
Chapter 11
The Cardiovascular System: Blood
Objective 3 & 4
3. Describe the origins and production of the
formed elements in blood.
4. Discuss the characteristics and functions of red
blood cells.
Production of Formed Elements
• Hemopoiesis – process by which formed
elements are produced
• In adults the main site of hemopoiesis is in red
bone marrow
• erythopoiesis – RBC formation
• leukopoiesis – WBC formation
• thrombopoiesis – platelet formation
Red Blood Cells
• RBC’s contain the pigment hemoglobin
• Oxygen and carbon dioxide bind to
hemoglobin
• RBC’s account for 99% of the formed elements
• How many RBC’s are in…
One drop of
blood
One cc or mL
Male Female
Whole Human
Body
2.6 million
5.4
4.8
million million
75 trillion
Hematocrit
• Hematocrit - the percentage of whole blood
volume occupied by cellular elements
• so this is MAINLY referring to the amount of
RBC’s present
• Hematocrit values increase when:
• You are dehydrated
• Less plasma (water) relative to # of RBC’s
• You make more RBC’s due to low oxygen levels
• More RBC’s are made in response to the hormone
erythropoietin, stimulates production
RBC Structure
• Unusual shape
• Biconcave
• Increases surface area to volume ratio
• Increases diffusion of gases
• Makes them flexible
• Easier to pass through tiny capillaries
RBC Structure continued…
• During formation,
RBC’s lose their
organelles
• Mitochondria
• Ribosomes
• Nuclei
• This prevents them
from dividing
(mitosis)
• Short life span
Hemoglobin Structure & Function
• Hemoglobin – a gas
transporting protein
• makes up 95% of a
mature RBC
• Hemoglobin contains
a pigment called
heme
• Each heme molecule
holds a iron ion
• Oxygen binds to the
iron on each heme
• When CO2 levels rise
around the RBC,
• It releases O2
• And gains CO2
• This process reverses
when O2 levels rise
around the RBC
RBC Life Span & Circulation
• RBC’s have a life span
up to 120 days
• They get beat up
traveling around
• Macrophages in the
liver, spleen, and bone
marrow eat the really
old & beat up looking
RBC’s
• 10% of RBC’s sneak by
macrophages and
hemolyze (explode!)
A round trip of the
circulatory system
takes only one
minute
Approximately 3
million new RBC’s
enter the blood
stream every
second
The Role of EPO in the Control
of Erythropoiesis
• Tissues deprived of
oxygen release EPO
(the hormone
erythropoietin)
• This accelerates
• division of stem cells in
bone marrow
• maturation of RBC’s
• Effect is more RBC’s
entering circulation
• This improves oxygen
delivery to tissues
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