Chapter 17 Blood Flashcards
What are the functions of the blood include?
Transport
Regulation
Protection
Transport functions include
- Delivering O2 and nutrients to body cells
- Transporting metabolic wastes to lungs and kidneys for elimination
- Transporting hormones form endocrine organs to target organs
Regulation functions include
- 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 functions include
-Preventing blood loss
Plasma proteins and platelets in blood initiate clot formation
-Preventing infection
Agents of immunity are carried in blood
+Antibodies
+Complement proteins
+White blood cells
What are elements?
which are cells that are living blood cells
- Cells are suspended in plasma
- Formed elements
Erythrocytes (red blood cells, or RBCs)
Leukocytes (white blood cells, or WBCs)
Platelets
Spun tube of blood yields three layers:
-Erythrocytes on bottom (~45% of whole blood)
Hematocrit: percent of blood volume that is RBCs
Normal values:
Males: 47% ± 5%
Females: 42% ± 5%
-WBCs and platelets in Buffy coat (< 1%)
Thin, whitish layer between RBCs and plasma layers
-Plasma on top (~55%)
Physical Characteristics and Volume
-Blood is a sticky, opaque fluid with metallic taste
-Color varies with O2 content
High O2 levels show a scarlet red
Low O2 levels show a dark red
pH 7.35–7.45
-Makes up ~8% of body weight
-Average volume:
Males: 5–6 L
Females: 4–5 L
Blood Plasma
Blood plasma is straw-colored sticky fluid
-About 90% water
Over 100 dissolved solutes
-Nutrients, gases, hormones, wastes, proteins, inorganic ions
-Plasma proteins are most abundant solutes
Remain in blood; not taken up by cells
Proteins produced mostly by liver
Albumin: makes up 60% of plasma proteins
Functions as carrier of other molecules, as blood buffer, and contributes to plasma osmotic pressure
Hematopoiesis
-formation of all blood cells
-Occurs in red bone marrow; composed of reticular connective tissue and blood sinusoids
In adult, found in axial skeleton, girdles, and proximal epiphyses of humerus and femur
Hematopoietic stem cells (hemocytoblasts)
- Stem cell that gives rise to all formed elements
- Hormones and growth factors push cell toward specific pathway of blood cell development
- Committed cells cannot change
Erythropoiesis
process of formation of RBCs that takes about 15 days
Stages of erythropoiesis
- Hematopoietic stem cell: transforms into myeloid stem cell
- Myeloid stem cell: transforms into proerythroblast
- Proerythroblast: divides many times, transforming into basophilic erythroblasts
- Basophilic erythroblasts: synthesize many ribosomes, which stain blue
- Polychromatic erythroblasts: synthesize large amounts of red-hued hemoglobin; cell now shows both pink and blue areas
- Orthochromatic erythroblasts: contain mostly hemoglobin, so appear just pink; eject most organelles; nucleus degrades, causing concave shape
- Reticulocytes: still contain small amount of ribosomes
- Mature erythrocyte: in 2 days, ribosomes degrade, transforming into mature RBC
Too few RBCs lead to..
tissue hypoxia
Too many RBCs increase….
blood viscosity
Erythropoietin
hormone that stimulates formation of RBCs
Hypoxia
is a condition where not enough oxygen makes it to the cells and tissues in the body. This can happen even though blood flow is normal
Causes of hypoxia
-Decreased RBC numbers due to hemorrhage or increased destruction
-Insufficient hemoglobin per RBC (example: iron deficiency)
-Reduced availability of O2 (example: high altitudes or lung problems such as pneumonia)
-Too many erythrocytes or high oxygen levels in blood inhibit EPO production
-EPO causes erythrocytes to mature faster
Testosterone enhances EPO production, resulting in higher RBC counts in males
RBC breakdown
heme, iron, and globin are separated
Anemia
-Blood has abnormally low O2-carrying capacity that is too low to support normal metabolism
-Three groups based on cause
Blood loss
Not enough RBCs produced
Too many RBCs being destroyed
Anemia (Blood loss)
-Hemorrhagic anemia
Rapid blood loss (example: severe wound)
Treated by blood replacement
-Chronic hemorrhagic anemia
Slight but persistent blood loss
Example: hemorrhoids, bleeding ulcer
Primary problem must be treated to stop blood loss
Anemia (Not enough RBCs being produced)
IRON-DEFICIENCY ANEMIA
-Can be caused by hemorrhagic anemia, but also by low iron intake or impaired absorption
-RBCs produced are called microcytes
Small, pale in color
Cannot synthesize hemoglobin because there is a lack of iron
-Treatment: iron supplements
PERNICIOUS ANEMIA
-Autoimmune disease that destroys stomach mucosa that produces intrinsic factor
-Intrinsic factor needed to absorb B12
-B12 is needed to help RBCs divide
-Without B12 RBCs enlarge but cannot divide, resultingin large macrocytes
-Treatment: B12 injections or nasal gel
- Can also be caused by low dietary intake of B12
Can be a problem for vegetarians
RENAL ANEMIA
- Caused by lack of EPO
- Often accompanies renal disease
Kidneys cannot produce enough EPO
- Treatment: synthetic EPO
APLASTIC ANEMIA
-Destruction or inhibition of red bone marrow
-Can be caused by drugs, chemicals, radiation,or viruses
Usually cause is unknown
-All formed element cell lines are affected
Results in anemia as well as clotting and immunity defects
-Treatment: short-term with transfusions, long-term with transplanted stem cells
Anemia (Too many RBCs destroyed)
-Premature lysis of RBCs
Referred to as hemolytic anemias
-Can be caused by:
Incompatible transfusions or infections
Hemoglobin abnormalities: usually genetic disorder resulting in abnormal globin
+Thalassemias
+Sickle-cell anemia
Anemia (Too many RBCs destroyed)
THALASSEMIAS
-Typically found in people of Mediterranean ancestry
-One globin chain is absent or faulty
-RBCs are thin, delicate, and deficient in hemoglobin
-Many subtypes that range in severity from mild to extremely severe
Very severe cases may require monthly blood transfusions
Anemia (Too many RBCs destroyed)
SICKLE-CELL ANEMIA
-Hemoglobin S: mutated hemoglobin
Only 1 amino acid is wrong in a globin beta chain of 146 amino acids
-RBCs become crescent shaped when O2 levels are low
Example: during exercise
-Misshaped RBCs rupture easily and block small vessels
Results in poor O2 delivery and pain
-Prevalent in black people of the African malarial belt and their descendants
-Possible benefit: people with sickle cell do not contract malaria
Kills 1 million each year
Individuals with two copies of Hb-S can develop sickle-cell anemia
Individuals with only one copy have milder disease and better chance of surviving malaria
-Treatment: acute crisis treated with transfusions; inhaled nitric oxide
-Prevention of sickling:
Hydroxyurea induces formation of fetal hemoglobin (which does not sickle)
Stem cell transplants
Gene therapy
Nitric oxide for vasodilation
