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
Polycythemia Vera
Bone marrow cancer leading to excess RBCs
Polycythemia
Abnormal excess of RBCs; increases blood viscosity, causing sluggish blood flow
Secondary polycythemia
caused by low O2 levels (example: high altitude) or increasedEPO production
Polycythemia (Blood doping)
athletes remove, store, and reinfuse RBCs before an event to increase O2 levels for stamina
Lymphocytes
-Second most numerous WBC, accounts for 25%
-Large, dark purple, circular nuclei with thin rim of blue cytoplasm
-Mostly found in lymphoid tissue (example: lymph nodes, spleen), but a few circulate in blood
-Crucial to immunity
-Two types of lymphocytes
T lymphocytes (T cells) act against virus-infected cells and tumor cells
B lymphocytes (B cells) give rise to plasma cells, which produce antibodies
