Chapter 17- Blood Flashcards
What are the 3 main functions of blood?
- Transport
- Maintenance/regulation
- Protection
What substances does blood transport (3)?
- Oxygen and nutrient delivery to tissues
- Waste removal from tissues (carbon dioxide and nitrogenous cellular waste)
- Hormone transport to target organs
What variables does blood regulate? (3)
- Body temperature
- pH
- Fluid volume
How does blood regulate body temperature?
Blood is mostly water, and water can absorb heat and set the body temperature. Blood can increase or decrease heat also. Blood can be moved closer to or further away from the skin. Blood that is closer to the skin will give off heat.
Why is it important for pH to be regulated?
pH must stay within its specific range or chemical reactions and cellular functions will be disrupted
Why is it important for fluid volume to be regulated?
High fluid volume will make your heart work harder, as will low fluid volume- blood must be transported through the body and blood pressure must be maintained.
What does blood protect against (2)?
- Blood loss- platelets clot blood when blood vessels are damaged
- Infection- leukocytes monitor for pathogens
Characteristics of blood (4)
- Scarlet to dark red in color, depends on how much oxygen is bound in the red blood cells
- Typical metallic taste due to iron
- pH range: 7.35-7.45
- Viscous- thicker than water due to erythrocyte composition
What are the 2 main components of blood?
Plasma and blood cells
Blood plasma function
Transports solutes and suspends the living portion of blood
Blood plasma composition
90% water, contains many kinds of solutes
What types of solutes are present in blood plasma? (6)
- Electrolytes
- Nitrogenous substances (urea, uric acid, etc.)
- Organic nutrients (glucose, amino acids, triglycerides, etc.).
- Respiratory gasses- carbon dioxide mainly
- Hormones- don’t enter any cells
- Plasma proteins
Plasma proteins
This solute makes up most of the mass of blood plasma. They float freely in the plasma, but are not used by cells for energy or nutrients- function varies depending on the protein. One important type of plasma protein is albumin.
Where are plasma proteins mainly produced?
The liver
Albumin
Plasma protein that is the major transport protein of blood, contributes to osmotic pressure in capillaries. If you didn’t have albumin, you would lose osmotic pressure.
What would happen to the bloodstream if you didn’t produce albumin?
A huge amount of water would leave the bloodstream. This is very bad- most of plasma is water, so the heart wouldn’t have much left to pump, it needs water in addition to cells. Water rushes into surrounding body tissues, causing extreme bloating and physically separating cells from each other, disrupting cellular functions because nutrients have a hard time getting to cells
Osmotic pressure
Osmotic pressure is the measure of the tendency for water to move into a concentrated solution (from the tissues to the blood, for example).
Types of blood cells (3)
Erythrocytes, leukocytes, platelets. Leukocytes are the only “true” cells since platelets are cell fragments and erythrocytes don’t have organelles.
All blood cells are
Short lived and non-mitotic- formed by hematopoietic stem cell, so mature cells do not reproduce
What is hematocrit? What are the normal ranges for males and females?
The portion of total blood volume made up by erythrocytes. Males- 47%, females- 42%
Hematopoiesis definition
A general term for production of all 3 blood cell types
Where does hematopoiesis occur?
Red bone marrow tissue.
How does hematopoiesis occur?
All blood cells arise from hematopoietic stem cells in the bone marrow. Stem cells eventually become “committed” to forming a certain type of blood cell- once committed, the cell cannot become any other cell type. In a single day, the marrow creates about 100 billion new cells. The spleen and liver also destroy a large amount of blood cells every day. This is a balancing act, we don’t want blood to be too thick (have too many cells) or too thin.
Where is red bone marrow located?
In adults, the axial skeleton, girdles, and heads of femur and humerus. In children, most bones have red bone marrow until they stop growing (18-21).
Why don’t erythrocytes have a nucleus or other organelles?
This prevents erythrocytes from using the oxygen they are transporting for cellular functions. Therefore, the maximum possible amount of oxygen can be delivered to tissues.
How long do erythrocytes typically live?
120 days
Hemoglobin
Protein responsible for oxygen transport in the blood, found in erythrocytes
Hemoglobin structure
A heme pigment is bound to a globin protein. The heme group has an iron ion at its center- free iron in the body is toxic. Globin has 2 alpha chains and 2 beta chains- each chain binds 1 heme group
How many molecules of oxygen can hemoglobin carry?
Each iron center in a heme group can bind one molecule of oxygen, and each hemoglobin has 4 heme groups. Therefore, each hemoglobin can carry 4 oxygen molecules, but red blood cells can carry about a billion oxygen molecules each since they have many hemoglobin molecules.
What features make erythrocytes ideal for gas exchange? (3)
- Large surface area relative to volume increases diffusion rate of oxygen
- Flattened disc shape increases diffusion rate of oxygen
- Anaerobic mechanism of energy production- gives the maximum possible amount of oxygen to tissues
Erythropoiesis process
Hematopoietic stem cell “commits” to a proerythroblast, which eventually develops into a mature erythrocyte. RBCs retain organelles until the last stage so the nucleus can direct the process.
Why does erythropoiesis need to be tightly regulated?
Balance is needed. Too few erythrocytes result in tissue hypoxia, and too many erythrocytes result in viscous blood- the heart is designed to pump blood at a specific viscosity
Where is erythropoietin produced?
The kidneys
Erythropoietin
A hormone that stimulates erythrocyte production. A small amount is almost always present in the blood to set the basal rate of production.
What stimulates erythropoietin production?
Hypoxic conditions in the kidneys cause increased release of EPO. This is a negative feedback mechanism- excessive oxygen supply suppresses EPO release. You release more EPO until oxygen gets too high, then it drops back down. The kidneys don’t care about number of red blood cells, just oxygen availability to cells
How does testosterone affect EPO production?
Testosterone enhances production of EPO. It does not stimulate bone marrow directly- stimulates the kidneys. This is why males generally have more erythrocytes and hemoglobin than females.
What general substances are necessary for erythropoiesis? (3)
- General nutrients- amino acids, lipids, carbohydrates necessary for cell synthesis
- B complex vitamins- B12 and folic acid. Necessary for normal DNA synthesis
- Iron- necessary for normal hemoglobin synthesis
Iron
A mineral that is necessary for normal hemoglobin synthesis. 65% of the body’s iron supply is in hemoglobin- the remainder is stored in the liver, spleen, etc..
How does iron travel in the blood?
Free iron is toxic, so it binds to protein transferrin- erythrocyte takes up iron as needed. The iron transferrin complex travels in the blood to find a red blood cell, and transferrin detaches so iron can go to the RBC.
What happens to erythrocytes as they age?
Hemoglobin begins to degenerate, and the cell becomes less flexible. The cell needs to be flexible to push past each other as they travel through capillaries
When erythrocytes break down, how are globin and iron recycled?
Globin is broken down into amino acids and released to circulation. Iron is bound to a transport protein and saved for reuse
How are erythrocytes destroyed?
Macrophages engulf and destroy the cell, and the heme group splits free from globin protein. The heme is broken down into bilirubin. It is picked up by the liver, excreted to intestines in bile- leaves body in feces (gives it the brown color). The globin and iron are recycled.
Anemia
When there is insufficient oxygen supply to meet body needs. Anemia is just a symptom of another disease or disorder
Anemia symptoms
Paleness, cold, shortness of breath, fatigue
Causes of anemia (3)
- Blood loss- acute or chronic hemorrhagic
- Inadequate erythrocyte production. Example- iron deficiency anemia (nutritional origins), renal anemia (little or no EPO release)
- Excessive erythrocyte destruction. Example- sickle cell anemia
Acute hemorrhagic anemia
Acute hemorrhagic anemia- severe, swift blood loss. Car crash, shooting, stabbing victims
Chronic hemorrhagic anemia
Slow, persistent blood loss (ulcer bleeding, hemorrhoids). If you lose blood, you’re also losing blood cells
Sickle cell anemia
A genetic condition caused by one amino acid change in the globin chain of erythrocytes. RBCs change their shape to a crescent shape rather than the typical round shape. The hooks of the sickle RBCs hook onto each other and get stuck in blood vessel walls, blocking them, and hemoglobin doesn’t bind and carry oxygen the way they should.
Polycythemia
Increase in blood erythrocytes- blood becomes viscous, flows slowly through blood vessels. Heart is basically pumping “sludge”. There are 3 types.
Types of polycythemia (3)
- Polycythemia vera
- Secondary polycythemia
- Blood doping
Polycythemia vera
A bone marrow cancer- hematocrit levels can get up to 80%. Blood volume doubles, vascular system engorges with blood and impairs circulation. This also puts a lot of stress on blood vessel walls, they become over stretched
Polycythemia Vera treatment
Treatment is therapeutic phlebotomy, but the underlying bone marrow cancer has to be treated as well.
Secondary polycythemia
Increased EPO release due to low oxygen availability. This is a natural physiological response that occurs at high altitudes. People living in Colorado, for example, produce more erythrocytes.
Blood doping
This is used by athletes to increase oxygen carrying capacity during athletic events. This is a temporary type of polycythemia. Too many RBCs make the blood more viscous, which makes the heart work harder. This puts the individual at risk for stroke, heart failure, and many other complications.
Methods of blood doping (2)
- Can take synthetic erythropoietin to stimulate the kidneys like normal
- Can also take a blood transfusion using their own blood- the blood is withdrawn, they make more blood, then put the old blood back in to increase blood volume
Leukocytes general function
Responsible for defending the body
Common characteristics of leukocytes (2)
- Not restricted to the blood vessels- use vessels as transport to certain parts of the body, but can leave if necessary
- Can be produced very quickly- numbers in the body can double within 2-3 hours
Diapedesis
The process by which WBCs can leave vessels via capillary walls