Chapter 17: Blood

Question 0

Spun tube of blood yields three layers

Answer 0

• Plasma on top (55%)
• WBCs and platelets in Buffy Coat in the middle (1%)
• Erythrocytes on bottom (45%)

Question 1

Hematocrit

Answer 1

• Percent of blood volume that is RBCs

- 47% for males and 42% for females

Question 2

Plasma

Answer 2

Non-living fluid matrix

Question 3

Formed Elements

Answer 3

Erythrocytes
Leukocytes
Platelets

Question 4

Physical Characteristics and Volume of Blood

Answer 4

-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

Question 5

Functions of Blood

Answer 5

• Distributing substances
• Regulating blood levels of substances
• Protection

Question 6

Distribution Function

Answer 6

• Delivering oxygen and nutrients to body cells
• Transporting metabolic wastes to lungs and kidneys for elimination
• Transporting hormones from endocrine organs to target organs

Question 7

Regulation Function

Answer 7

• 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

Question 8

Protection Function

Answer 8

-Preventing blood loss
 .Plasma proteins and platelets initiate clot formation
-Preventing infection
 .Antibodies
 .Complement proteins
 .WBCs

Question 9

Blood Plasma

Answer 9

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

Question 10

Albumin

Answer 10

60% of plasma protein

Substance carrier, Blood buffer, Major contributor of plasma osmotic pressure

Question 11

Formed Elements

Answer 11

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

Question 12

Erythrocytes

Answer 12

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

Question 13

Structural Characteristics of Erythrocytes for Gas Transport

Answer 13

Biconcave shape- huge surface area relative to volume
>97% hemoglobin (not counting water)
No mitochondria; ATP production anaerobic; do not consume oxygen they transport

Question 14

Erythrocyte Function

Answer 14

RBCs dedicated to respiratory gas transport
Hb binds reversibly with oxygen
Normal values
 - Male 13-18g/100ml
 - Females 12-16g/100ml

Question 15

Globin

Answer 15

Composed of 4 polypeptide chains

Two alpha and two beta chains

Question 16

Heme

Answer 16

Pigment bonded to each globin chain

Gives blood red color

Question 17

Hb Structure

Answer 17

Heme’s central iron atom binds to one oxygen
Each Hb molecule can transport four oxygens
Each RBC contains 250 million Hb molecules

Question 18

Oxyhemoglobin

Answer 18

Oxygen loading in lungs

Ruby red

Question 19

Deoxyhemoglobin

Answer 19

Oxygen unloading in tissues

Dark red

Question 20

Carbaminohemoglobin

Answer 20

Carbon Dioxide loading in tissues

20% of CO2 in blood binds to Hb

Question 21

Hematopoiesis

Answer 21

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

Question 22

Hematopoietic Stem Cells

Answer 22

Hemocytoblasts
Give rise to all formed elements
Hormones and growth factors push cell toward specific pathway of blood cell development
Committed cells cannot change

Question 23

Erythropoiesis

Answer 23

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

Question 24

Regulation of Erythropoiesis

Answer 24

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

Question 25

Erythropoietin

Answer 25

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

Question 26

Causes of Hypoxia

Answer 26

Decreased RBC numbers due to hemorrhage or increased destruction
Insufficient Hb per RBC (iron deficiency)
Reduced availability of oxygen (high altitude)

Question 27

Effects of Erythropoietin

Answer 27

Rapid maturation of committed marrow cells

Increased circulating reticulocyte count in 1-2 days

Question 28

Testosterone and EPO Production

Answer 28

Testosterone enhances EPO production

Resulting in higher RBC counts in males

Question 29

Dietary Requirements for Erythropoiesis

Answer 29

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)

Question 30

Life Span of Erythrocytes

Answer 30

100-120 Days

No protein synthesis, growth, or division

Question 31

Destruction of Erythrocytes

Answer 31

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

Question 32

Fate of Erythrocytes

Answer 32

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