Chapter 17: Blood Flashcards
Spun tube of blood yields three layers
- Plasma on top (55%)
- WBCs and platelets in Buffy Coat in the middle (1%)
- Erythrocytes on bottom (45%)
Hematocrit
- Percent of blood volume that is RBCs
- 47% for males and 42% for females
Plasma
Non-living fluid matrix
Formed Elements
Erythrocytes
Leukocytes
Platelets
Physical Characteristics and Volume of Blood
-Sticky, opaque fluid, with metallic taste
-Color varies with oxygen content
.High Oxygen = Scarlet
.Low Oxygen = Dark Red
-pH= 7.35-7.45
-8% body weight
-Volume = 5 L
Functions of Blood
- Distributing substances
- Regulating blood levels of substances
- Protection
Distribution Function
- Delivering oxygen and nutrients to body cells
- Transporting metabolic wastes to lungs and kidneys for elimination
- Transporting hormones from endocrine organs to target organs
Regulation Function
- Maintaining body temperature by absorbing and distributing heat
- Maintaining normal pH using buffers; alkaline reserve of bicarbonate ions
- Maintaining adequate fluid volume in circulatory system
Protection Function
-Preventing blood loss .Plasma proteins and platelets initiate clot formation -Preventing infection .Antibodies .Complement proteins .WBCs
Blood Plasma
90% water
Over 100 dissolved solutes
-Nutrients, gases, hormones, wastes, proteins, inorganic ions
-Plasma proteins most abundant solutes
.Remain in blood; not taken up by cells
.Proteins produced mostly by liver
.60% albumin; 36% globulins; 4% fibrinogen
Albumin
60% of plasma protein
Substance carrier, Blood buffer, Major contributor of plasma osmotic pressure
Formed Elements
Only WBCs are complete cells
RBCs have no nuclei or other organelles
Platelets are cell fragments
Most formed elements survive in bloodstream only few days
Most blood cells originate in bone marrow and do not divide
Erythrocytes
Biconcave discs, anucleate, essentially no organelles
Diameters larger than some capillaries
Filled with HB for gas transport
Contain plasma membrane protein spectrin and other proteins
-Spectrin provides flexibility to change shape
Major factor contributing to blood viscosity
Structural Characteristics of Erythrocytes for Gas Transport
Biconcave shape- huge surface area relative to volume
>97% hemoglobin (not counting water)
No mitochondria; ATP production anaerobic; do not consume oxygen they transport
Erythrocyte Function
RBCs dedicated to respiratory gas transport Hb binds reversibly with oxygen Normal values - Male 13-18g/100ml - Females 12-16g/100ml
Globin
Composed of 4 polypeptide chains
Two alpha and two beta chains
Heme
Pigment bonded to each globin chain
Gives blood red color
Hb Structure
Heme’s central iron atom binds to one oxygen
Each Hb molecule can transport four oxygens
Each RBC contains 250 million Hb molecules
Oxyhemoglobin
Oxygen loading in lungs
Ruby red
Deoxyhemoglobin
Oxygen unloading in tissues
Dark red
Carbaminohemoglobin
Carbon Dioxide loading in tissues
20% of CO2 in blood binds to Hb
Hematopoiesis
Blood cell formation in red BM
- Composed of reticular connective tissue and blood sinusoids
In adult, found in axial skeleton, girdles, and proximal epiphyses of humerus and femur
New blood cells enter blood sinusoids
Hematopoietic Stem Cells
Hemocytoblasts
Give rise to all formed elements
Hormones and growth factors push cell toward specific pathway of blood cell development
Committed cells cannot change
Erythropoiesis
As myeloid stem cell transforms
-Ribosomes synthesized
-Hb synthesized; iron accumulates
-Ejection of nucleus; formation of reticulocyte (young RBC)
Reticulocyte ribosomes degraded; then become mature erythrocytes
Reticulocyte count indicates rate of RBC formation
Regulation of Erythropoiesis
Too few RBCs lead to tissue hypoxia
Too many RBCs increases blood viscosity
>2 million RBCs made per second
Balance between RBC production and destruction depends on
- Hormonal controls
- Adequate supplies of iron, amino acids, and B vitamins
Erythropoietin
Direct stimulus for erythropoiesis
Always small amount in blood to maintain basal rate
- High RBC or oxygen levels depress production
Released by kidneys (some from liver) in response to hypoxia
- Dialysis patients have low RBC counts
Causes of Hypoxia
Decreased RBC numbers due to hemorrhage or increased destruction
Insufficient Hb per RBC (iron deficiency)
Reduced availability of oxygen (high altitude)
Effects of Erythropoietin
Rapid maturation of committed marrow cells
Increased circulating reticulocyte count in 1-2 days
Testosterone and EPO Production
Testosterone enhances EPO production
Resulting in higher RBC counts in males
Dietary Requirements for Erythropoiesis
Nutrients- AA, lipids, and carbohydrates
Iron
-Available from diet
- 65% in Hb; rest in liver, spleen and BM
- Free iron ions toxic
. Stored in cells as ferritin and hemosiderin, transported in blood bound to protein transferrin
Vitamin B12 and folic acid necessary for DNA synthesis for rapidly dividing cells (developing RBCs)
Life Span of Erythrocytes
100-120 Days
No protein synthesis, growth, or division
Destruction of Erythrocytes
Old RBCs become fragile Hb begins to degenerate Get trapped in smaller circulatory channels especially in spleen Macrophages engulf dying RBCs in spleen Heme and globin are separated
Fate of Erythrocytes
Iron salvaged for reuse
Heme degraded to yellow pigment bilirubin
Liver secretes bilirubin (bile) into intestines
-degraded to pigment urobilinogen
-pigment leaves body in feces as stercobilin
Globin metabolized into AA
-released into circulation
