Chapter 17: Blood Flashcards
Functions of Blood
- distribution
- regulation
- protection
Functions of Blood: Distribution
Distribution of:
- O2 and nutrients to body cells
- metabolic wastes to the lungs and kidneys for elimination (spleen too)
- hormones from endocrine organs to target organs
Functions of Blood: Regulation
Regulation of:
- body temperature by absorbing and distributing heat
- maintain normal pH (7.35-7.45) using buffers*
- adequate fluid volume in the circulatory system- we need fluid volume for blood pressure
- homeostasis- blood uses positive feedback
Functions of Blood: Protection
Protection against:
- blood loss- plasma proteins and platelets initiate clot formation
- infection:
- antibodies
- complement proteins
- WBCs defend against foreign invaders
Blood Composition
- blood is a fluid connective tissue composed of:
1. plasma (55%)
2. formed elements (45%)- erythrocytes (RBCs)- most abundant formed element
- leukocytes (WBCs)
- platelets
- pH 7.35-7.45 (slightly basic)
Erythrocytes
- RBCs
- hematocrit
- percent of blood volume that is RBCs
- 47% +- 5 for males
- 42% +- 5% for females
Hematocrit (Hct)
= RBC / total blood volume
Centrifuging Blood
- plasma layer on top- 55% of whole blood, least dense component
- buffy coat- leukocytes and platelets, 1% of whole blood
- erythrocytes- 45% of whole blood, most dense component
- separates plasma from formed elements
Hemopoiesis
- blood cell formation
- occurs in red bone marrow of axial skeleton, gridles and proximal epiphyses of humerus and femur
- most commonly in upper form of lower limbs
hemocytoblasts (hematopoietic stem cells)
- give rise TO ALL FORMED ELEMENTS
- hormones and growth factors push the cell towards a specific pathway of blood cell development
How long does it take for blood to circulate to the body and back to the heart
-20-60 seconds
Erythropoiesis
- red blood cell production
- goes from hemocytoblast -> erythrocyte
- takes 15 days
- color changes from blue of ribosomes to pink of hemoglobin
CBC
- complete blood cell count
- measure RBCs, leukocytes, platelets, hematocrit
reticulocyte
- immature RBC
- sometimes bones push out reticulocytes to increase blood volume to aid mature RBCs in oxygen delivery
regulation of erythropoiesis
- too few RBCs leads to tissue hypoxia
- too many RBCs increases blood viscosity- blood moves slower and RBCs may be less effective
- balance between RBC production and destruction depends on hormonal controls and adequate supplies of iron, amino acids, and B vitamins
erythropoietin (EPO)
- hormone that stimulates erythropoiesis
- released by the kidneys in response to hypoxia
- many of the hematopoietic hormones (EPO) are used with cancer or AIDS patients to stimulate bone marrow
effects of EPO
- increases production of RBCs
- testosterone also enhances EPO production, resulting in higher RBC counts in males (Lance Armstrong)
- Dietary Requirements:
- nutrients
- iron
- vitamin B12
- folic acid
Negative Feedback Cycle
- stimulus- hypoxia due to decreased RBC count, decreased amount of hemoglobin, decreased availability of O2
- kidney (and liver to a smaller extent) releases erythropoietin
- erythropoietin stimulates red bone marrow
- enhanced erythropoiesis increases RBC count
- O2 carrying ability of blood increases
- stimulus- hypoxia due to decreased RBC count, decreased amount of hemoglobin, decreased availability of O2
- homeostasis- normal blood oxygen levels
Erythropoietin (EPO) in the blood would rise due to all the following except
- during anemia
- at high altitudes
- as a consequence of hemorrhage
- due to infection
- when blood flow to the kidney is disrupted
Leukopoiesis
- production of WBCs
- stimulated by chemical messengers from bone marrow and mature WBCs
- all leukocytes originate from hemocytoblasts
- there are 5 main types of WBCs
5 types of leukocytes
- all come from a hemocytoblast
- immature WBC- bands ** (in the marrow) -> if someone has bands in their blood it is called left shift
- eosinophils- granular
- basophils- granular
- neutrophils- granular
- monocytes- agranular
- lymphocytes- agranular
Blood Plasma
- 55% of blood
- 90-92% water
- plasma proteins- contribute to osmotic pressure, most column is albumin
- nitrogenous byproducts of metabolism- lactic acid, urea, creatinine
- nutrients- glucose, lipids, amino acids, vitamins
- electrolytes- Na, K, Ca, Mg, Cl, HCO3- most abundant
- respiratory gases- O2, CO2
- hormones
Formed Elements
- RBC, WBC, platelets
- RBC majority of formed elements (99%)
- RBCs have no nuclei or organelles
- only WBCs are complete cells
- platelets are cell fragments
- most blood cells originate in bone marrow and do not divide
Erythrocyte structure and function
- RBCs are dedicated to respiratory gas transport
- biconcave
- no nucleus
- no organelles
- hemoglobin binds reversibly with oxygen
- iron atom in each heme can bind to one O2 molecule
- each Hb molecule can transport four O2
- one RBC contains about 250 million hemoglobin molecules so each RBC can transport about 1 billion molecules of O2
Life of RBC
- birth in red bone marrow
- 15 days to grow in the bone marrow
- lives for about 120 days
- dies in the spleen, macrophages destroy old and damaged RBCs
- hemoglobin is broken down and parts are either recycled or excreted
Erythrocyte disorders
- anemia
- polycythemia
anemia
- low oxygen carrying capacity
- causes- blood loss, low RBCs produced, abnormal RBC
polycythemia
- excess of RBC (increases viscosity)
- bone marrow cancer
- secondary polycythemia- when less O2 is available (high altitude) or when EPO production increases
- blood doping- can increase risk of MI, stroke, or blood clots
causes of anemia (dont study crazy)
- blood loss- hemorrhagic anemia
- not enough RBC produced:
- pernicious anemia- vitamin B12 intrinsic factor
- aplastic anemia- destruction of bone marrow by drugs
- RBC destroyed or abnormal hemoglobin:
- hemolytic anemia- mismatched blood
- thalassemia’s- genetic disease of Mediterranean ancestry
- sick cell anemia- abnormal hemoglobin
sick-cell disease
- normal erythrocyte has normal hemoglobin amino acid sequence in the beta chain
- sickled erythrocyte results from a single amino acid change in the beta chain of hemoglobin
RBCs are efficient oxygen transport cells. Of the following characteristics, which is the major contributor to the significant oxygen-carrying capacity of a RBC
- RBC lack mitochondria
- RBC dont divide
- RBC are biconcave discs***
- RBC contain myoglobin
oxygen binds to the _________ portion of hemoglobin
- globin
- oxyhemoglobin
- iron atom**
- amino acid
leukocytes
- make up <1% of total blood volume
- can leave capillaries via diapedesis*
- move through tissue spaces by ameboid motion and positive chemotaxis* (follow trail released by damaged cells)
- leukocytosis- WBC count over 11,000/mm3- normal response to bacterial or viral invasion