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Chapter 13
Blood, Heart, and Circulation
Composition of Blood -
-The human body makes about 2.5 million new blood cells per second. Which means that is how many are dying off in that amount of time.
So we make about five hundred million cells daily. CRAZY!!
-There are 60,000 miles of vessels throughout the human body (Australia and back four times) Your heart pumps this distance every minute.
-These blood vessels are flexible and will repair themselves when they leak.
-They carry gases, nutrients, hormones, wastes, etc, all together
-Capillaries are about one cell thick (the thickness allows for good diffusion for each cell across the membrane).
Blood is divided into two layers.
1) Formed Element
- Red Blood Cells
- White blood Cells (Mostly neutrophils and white blood cells are not as common as red blood cells)
- Platelets
- Which is about 92 percent water, while the remaining 8 percent consists of various organic molecules and salts (sodium most common salt).
- Albumins (most common and is made by the liver. It is also the same protein that is in egg whites)
- Albumins play an important role in maintaining the bloods osmotic pressure needed to draw water from the surrounding tissue fluid into the capillaries. This action is needed to maintain blood volume and pressure.
- Fibrinogen (the clotting protein)
- During the process of clot formation fibrinogen is converted into threads of fibrin.
- Globulins (the antibodies) which is involved with immunity
-* serum is plasma only without the clotting proteins (no fibrinogen is present)
Formed Elements of Blood, The formed elements of blood include two types of blood cells: erythrocytes, or red blood cells, and leukocytes, or white blood cells.
Red blood cell (erythrocyte) also known as "RBC's". RBC’s are formed in the myeloid tissue or most commonly known as red bone marrow, although when the body is under severe conditions the yellow bone marrow, which is also in the fatty places of the marrow, in the body will also make RBC’s. The formation of RBC’s is called erythropoiesis ( erythro / red; poiesis / formation). Red blood cells lose nuclei upon maturation, and take on a biconcave, dimpled, shape. They are about 7-8 micrometers in diameter. RBC's live about 120 days and do not self repair. Older erythrocytes are removed from the circulation by phagocytic cells in the liver, spleen, and bone marrow. RBC's contain hemoglobin which transports oxygen from the lungs to the rest of the body, such as to the muscles, where it releases the oxygen load.The hemoglobin gets it's red color from their respiratory pigments.
The main component of the RBC is hemoglobin (hemo / blood; globin / protein) protein which is about 25 million per cell. This is the protein substance of four different proteins: polypeptide globin chains that contain anywhere from 141 to 146 amino acids. Hemoglobin also is responsible for the cell’s ability to transport oxygen and carbon dioxide. In arterial blood, it is bright red because of a high concentration of oxyhemoglobin (the combination of oxygen and hemoglobin) in the red blood cells. In venous blood (the blood returning to the heart) it contains less oxygen, and is therefore a darker red than the oxygen-rich arterial blood. Carbon Monoxide forms with hemoglobin faster than oxygen, and stays formed for several hours making hemoglobin unavailable for oxygen transport right away. Also a red blood cell contains about 200 million hemoglobin molecules. If all this hemoglobin was in the plasma rather than inside the cells, your blood would be so "thick" that the heart would have a difficult time pumping it through. The thickness of blood is called viscosity. The greater the viscosity of blood, the more friction there is and more pressure is needed to force blood through. Iron travels in the blood to the bone marrow attached to a protein carrier called transferring.
The main function is the transportation of oxygen throughout the body and the ability of the blood to carry out carbon dioxide which is called carbamino – hemoglobin. Maintaining the balance of blood is important. The balance can be measured by the acid and base levels in the blood. This is called pH. Normal pH of blood ranges between 7.35-7.45; this normal blood is called Alkaline (less acidic then water). A drop in pH is called Acidic. This condition is also called Acidosis. A jump in pH higher then 7.45 is called "Alkalosis". To maintain the homeostasis (or balance,) the blood has tiny molecules within the RBC that help prevent drops or increases from happening.
A dietary deficiency in iron reduces the ability of the bone marrow to produce hemoglobin, and can result in iron-deficiency anemia. Anemia is an abnormally low hemoglobin concentration and or red blood cell count.
Hematocrit
(HCT)As well as a persons gender there are other factors that may influence hematocrit levels. High altitudes will increase the hematocrit levels because the higher elevation will cause an increase of red blood cells in order to compensate for the higher altitude. Hematocrit levels will also be effected by the amount one drinks, dehydration will cause an increase in the hematocrit levels.
normal hematocrit levels:
men: 42 - 53%
women: 36 - 48%
babies: 50 - 75%
(babies have a low oxygenated environment because their oxygenated blood mixes with their deoxygenated blood before it can reach all the cells)
-low hematocrit (anemia, blood loss, bone marrow failure, leukemia, liver cirrosis, etc.
-high hematocrit most likely due to dehydration
Homeostasis (Coagulation or Clotting)
Anticoagulants
Clotting of blood in test tubes can be prevented by the addition of sodium citrate, which bind to calcium ions. By this means, Ca2 levels in the blood that can participate in the clotting sequence are lowered and clotting is inhibited.
Homeostasis is the natural process of stopping blood flow or loss of blood following an injury. (hemo = blood; stasis = standing). It has three stages: (1) vascular spasm, vasoconstriction, or intense contraction of blood vessels, (2) formation of a platelet plug and (3) blood clotting or coagulation. Once the flow of blood has been stopped, tissue repair can begin.
Blood clots contain platelets and fibrin and usually trapped red blood cells that give the clot a red color. The clots that are formed in arteries, where blood flow is faster lack red blood cells and are usually gray. The platelet mass in the process of clot retraction forms a more compact and effective plug. Serum is fluid squeezed from the clot. Serum is plasma without fibrogen.
- Intrinsic pathway produces clots in damaged blood vessels when collagen is exposed to plasma.
- Extrinsic pathway is when a chemical is produced that creates a shortcut in the formation of fibrin.
Formation of a Platelet Plug: Within 20 seconds of an injury, coagulation is initiated. Contrary to popular belief, clotting of a cut on the skin is not initiated by air or drying out, but by platelets adhering to and activated by collagen in the blood vessels endothelium. The activated platelets then release the contents of their granules, which contain a variety of substances that stimulate further platelet activation and enhance the hemostatic process.
When the lining of a blood vessel breaks and endothelial cells are damaged, revealing collagen proteins in the vessel wall, platelets swell, grow spiky extensions, and start clumping together. They start to stick to each other and the walls of the vessel. This continues as more platelets congregate and undergo these same transformations. This process results in a platelet plug that seals the injured area. If the injury is small, a platelet plug may be able to form and close it within several seconds. If the damage is more serious, the next step of blood clotting will take place. Platelets contain secretory granules. When they stick to the proteins in the vessel walls, they degranulate, thus releasing their products, which include ADP (adenosine diphosphate), serotonin, and thromboxane A2.
A Blood Clot Forms: If the platelet plug is not enough to stop the bleeding, the third stage of homeostasis begins: the formation of a blood clot. First, blood changes from a liquid to a gel. At least 12 substances called clotting factors take part in a series of chemical reactions that eventually create a mesh of protein fibers within the blood. Each of the clotting factors has a very specific function. We will discuss just three of the substances here: prothrombin, thrombin, and fibrinogen. Prothrombin and fibrinogin are proteins that are produced and deposited in the blood by the liver.
- Prothrombin: When blood vessels are damaged, vessels and nearby platelets are stimulated to release a substance called prothrombin activator, which in turn activates the conversion of prothrombin, a plasma protein, into an enzyme called thrombin. This reaction requires calcium ions.
- Thrombin: Thrombin facilitates the conversion of a soluble plasma protein called fibrinogen into long insoluble fibers or threads of the protein fibrin.
- Fibrin: Fibrin threads wind around the platelet plug at the damaged area of the blood vessel, forming an interlocking network of fibers and a framework for the clot. This net of fibers traps and helps hold platelets, blood cells and other molecules tight to the site of injury, functioning as the initial clot. This temporary fibrin clot can form in less than a minute, and usually does a good job of reducing the blood flow. Next, platelets in the clot begin to shrink, tightening the clot and drawing together the vessel walls. Usually, this whole process of clot formation and tightening takes less than a half hour.
Functions of Blood
- Transport Oxygen, Carbon dioxide, Glucose, Ammonia, nutrients and Hormones
- It is protection or defense (Immune system)
- Heat regulation
- Protection against bleeding (clotting)
All of the substances that are essential for cellular metabolism are transported by the circulatory system. Red blood or erythrocytes transport oxygen to the cells. In the lungs oxygen that is inhaled attaches to the blood molecules within the erythrocytes and is transported to the cells for aerobic respiration. Carbon dioxide that is produced by cell respiration is carried by the blood to the lungs to be exhaled.
The circulatory system protects against blood loss from injury and against foreign microbes or toxins that are introduced to the body. The clotting mechanism protects against blood loss when blood vessels are damaged.
The immune function of the blood is performed by the leukocytes (white blood cells) that protect against many disease causing agents (pathogens).
The Circulatory system contributes to both hormonal and temperature regulation. The blood carries hormones from their site of origin to the distant target tissues, where they perform a variety of regulatory functions. Temperature regulation is aided by the diversion of blood from deeper to more superficial cutaneous vessels or vice versa. When the temperature is high, diversion of blood from deep to superficial vessels helps to cool the body, and when the temperature is low, the diversion of blood from superficial to deeper vessels helps to keep the body warm.
The digestive system is responsible for the mechanical and chemical breakdown of food so that it can be absorbed through the intestinal wall into the blood and lymphatic vessels. The blood then carries these absorbed products of digestion through the liver and to the cells of the body.
Metabolic waste (like urea), excess water and ions, and other molecules not needed by the body are carried by the blood to the kidneys and excreted in the urine.
Gas Exchange
-Capillary exchange ( of all the blood vessels only capillaries can make the gas exchange)- Pumping of heart sends blood out via the arteries to the capillaries where exchange takes place through capillary walls. Blood returns via the veins.
-Arterial blood contains more oxygen and nutrients than venous blood
-Venous blood contains more wastes, including carbon dioxide, than arterial blood.
-Blood capillaries
-Processes at work during capillary exchange.
-blood pressure
-diffusion (Oxygen, amino acids, and glucose diffuses out in the capillary and carbon dioxide, water, and wastes diffuse in the capillary)
=there is no active transport in capillaries because the thickness of the capillary makes it easy for molecules to get in and out)
-osmotic pressure
-Arterial end of capillary
-When arterial blood enters tissue capillaries:
-Bright red due to oxygen levels.
-rich in dissolved nutrients
-Blood pressure is higher than osmotic pressure
-Water and nutrients exit capillaries
-Venous end of capillary
-Blood pressure is reduced because capillaries have a greater
cross-section compared to blood vessels that enter and leave the
capillaries
-No reduction of osmotic pressure
-Water tends to enter the capillary
Oxygen (O2) is the most immediate need of every cell and is carried throughout the body by the blood circulation. Oxygen is used at the cellular level as the final electron acceptor in the electron transport chain (the primary method of generating ATP for cellular reactions). Oxygen is carried in the blood bound to hemoglobin molecules within red blood cells. Hemoglobin binds oxygen when passing through the alveoli of the lungs and releases oxygen in the warmer, more acidic environment of bodily tissues, via simple diffusion.
Carbon dioxide (CO2) is removed from tissues by blood and released into the air via the lungs. Carbon dioxide is produced by cells as they undergo the processes of cellular respiration (particularly the Kreb's Cycle). The molecules are produced from carbons that were originally part of glucose. Most of the carbon dioxide combines with water and is carried in the plasma as bicarbonate ions. An excess of carbon dioxide (through exercise, or from holding ones breath) quickly shifts the blood pH to being more acidic (acidosis). Chemoreceptors in the brain and major blood vessels detect this shift and stimulate the breathing center of the brain (the medulla oblongata). Hence, as CO2 levels build up and the blood becomes more acidic, we involuntarily breathe faster, thus lowering CO2 levels and stabilizing blood pH. In contrast, a person who is hyperventilating (such as during a panic attack) will release too much CO2 and the blood will become too alkaline (alkalosis).
3 basic causes of shock
1. Pump failure, due to heart disease
2. Vessel failure
3. Content failure
SEPTIC SHOCK
refers to a dangerously low blood pressure that may result from sepsis, or infection. This can occur through the action of a bacterial lipopolysaccharide called endotoxin. The mortality associated with septic shock is presently very high, estimated at 50% to 70%. According to recent information, endotoxin activates the enzyme nitric oxide in synthase within macrophages--cells that play a important role in the immune response. Nitric oxide synthase produces nitric oxide, which promotes vasodilation and, as a result, a fall in blood pressure. Septic shock has recently been treated effectively with drugs that inhibit the production of nitric oxide. Basically not only can the infection itself kill you, but the treatment could also kill you due to the fact that when you kill the bacteria it will release toxins that could kill you.
Blood Typing
Blood is classified into different types (A, B, AB, or O) according to the absence or presence of certain antigens on the surface of a persons red blood cells.
Type A blood has A antigens
Type B blood has B antigens
Type AB has both A and B antibodies
This makes it so if you have type A blood you can only receive type A blood so your body will not recognize anything foreign and try to fight it. An individual with type B blood does not produce antibodies to B antigen because that antigen is recognized as "self." This person will have antibodies to A antigen even if this person has never been exposed to type A blood.
Type O has neither antigen in it which makes it the universal donor because any anti-A or anti-B antibodies that may be present in the recipient will find no target on the type O donor cell
Review Questions
1. Which processes are at work during capillary exchange?
a. Blood Pressure
b. Diffusion
c. Osmotic Pressure
d. All of the above
2. Arterial blood contains more:
a. wastes
b. oxygen
c. nutrients
d. a and b only
e. b and c only
3.If you were to measure the blood vessels in your body, how many miles would it stretch?
a.100,000 miles
b.2,000,000 miles
c.60,000 miles
d.6,000 miles
e.There is no way to measure blood vessels
4. How thick would you say your blood capillaries are?
a.1 inch thick
b.3 cells thick or bigger
c.1/2 an inch thick
d.1 cell thick or smaller so your blood cells would have to squeeze in
e.As thick as a pencil
5. Where do we get most of our Vitamin K?
a. liver
b. bacteria
c. eating leafy green veggies
d. taking vitamin supplements
e. all of the above
6. As I was mountain climbing my body would produce more red blood cells as I reached higher elevations due to which hormone?
a. thrombopoietin
b. cytokines
c. erythropoietin
d. megakaryocytes
7. Which of the plasma proteins are responsible for the osmotic pressure in the arteries and is produced by the liver?
a. Albumin
b. Globulins
c. Fibrinogens
d. None of the above
8. What is the approximate life span of an erythrocyte?
a. 3 days
b. 4 months
c. not known
d. 1 year
9. How many blood cells do you make per second?
a. 25,000
b. 2.5 billion
c. 2.5 million
d. 2500
e. none of the above
10. Plasma contains:
a. Water
b. Na++
c. Mg++
d. K+
e. All of the above
11. The mineral need for chemical clotting is:
a. sodium
b. calcium
c. iron
d. potassium
12. The function of erythroprotien is to:
a. decrease RBC production
b. Increase RBC production
c. Decrease all blood cell production
d. increase all blood cell production
13.Taking aspirin every day can reduce the risk of heart disease because:
a. it is a powerful vasodilator
b. it blocks pain receptors in heart tissue
c. it loosens plaque on arterial walls
d. it prevents platelet clumping
14. A hematocrit measures percentage of:
a. White blood cells
b. Plasma
c. Platelets
d. Red blood cells
15. Which type of blood is the universal donor?
a. Type A
b. Type B
c. Type C
d. Type AB
e. Type O
16. An individual with type AB blood
a. is considered a universal blood donor.
b. is considered a universal blood recipient.
c. produces antibodies to the B antigen.
d. produces antibodies to the A antigen.
e. is Rh-positive.
17. All of the following are blood cells except:
a. megakaryocyte
b. erythrocytes
c. leukocytes
d. thrombocytes
18. Which of the following about plasma is not true?
a. 91% water
b. carries body heat
c. transports hormones
d. insoluble
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