Ch. 15 - Blood Flashcards
Describe the functions of blood
the various components of blood function in distribution, regulation and protection:
distribution:
- delivery of oxygen from the lungs
- delivery of nutrients from the GI tract to all cells in the body
- transport of hormones from endocrine organs to target organs
- transport of metabolic waste products from cells to various elimination sites, including: kidneys - disposal of nitrogenous wastes in the urine, and lungs - elimination of CO2
regulation:
- maintenance of proper fluid volume in the circulatory system; proteins in the blood prevent excessive fluid loss from the bloodstream into tissue spaces, so fluid volume remains in the blood vessels, supporting blood circulation throughout the body
- maintenance of body temp. by absorption and distribution of body heat, as well as to the skin surfaces for heat loss
- maintenance of normal pH in body tissues, with proteins and other blood borne solutes becoming buffers, to prevent serious changes in blood pH
- reservoir for bicarbonate ions, which act as the body’s alkaline reserve
protection:
- prevention of infection, via actions of antibodies, complement proteins, and WBC’s; protecting against bacteria/viruses/foreign agents
- prevention of blood loss through actions of platelets and plasma proteins, beginning clot formation and slowing/stopping blood loss
Describe the important components of blood.
Blood is actually a connective tissue with its cells suspended in a liquid, the extracellular matrix.
Blood is a homogenous liquid meaning it has a similar composition throughout.
The blood is made up of cells, fragments of cells and dissolved biochemicals containing nutrients, oxygen, hormones, and wastes.
Red blood cells(RBC’s) Transport gases.
White blood cells(WBC’s)/leukocytes fight disease.
Platelets aid in clotting.
Only the WBC’s are complete cells, containing nuclei and organelles.
RBC’s, WBC’s and platelets are collectively called formed elements.
The liquid portion of the blood is called plasma.
Describe colloid osmotic pressure.
Plasma proteins are too large to move through capillary walls, so they create an osmotic pressure to hold water in the capillaries.
This helps regulate water movement between blood and tissues, to aid in controlling blood volume and blood pressure.
Specify the composition of plasma.
Plasma suspends the cells and platelets of the blood.
It is a clear, straw-coloured liquid made up of 92% water, with organic and inorganic biochemicals.
The composition of plasma resembles that of interstitial fluid. Concentrations of major plasma ions are similar to those of interstitial fluid, differing greatly from the concentrations inside cells.
Plasma helps to transport gases, hormones, nutrients and vitamins, while helping to regulate fluid and electrolyte balance as well as pH levels.
Electrolytes like sodium and chloride are the most prevalent of the solutes within plasma.
Plasma proteins are heavier than electrolytes, and not typically used as energy sources, remaining in the blood and interstitial fluids.
By weight alone plasma proteins are the most abundant of the plasma solutes, making up approx. 8% of plasma weight.
The liver synthesis and releases more than 90% of the plasma proteins, including all albumins, fibrinogen and most globulins.
Plasma also contains products of cell activity and wastes.
List 3 types of plasma proteins.
Albumins:
The smallest of the plasma proteins.
Makes up around 60% of plasma proteins by weight.
Made in the liver.
Helps maintain the plasma’s colloid osmotic pressure, transporting smaller molecules such as hormones and ions.
Important blood buffers.
Globulins:
alpha and beta globulins transport lipids and fat-soluble vitamins.
gamma globulins constitute a type of antibody.
Make up around 36% of plasma proteins.
Fibrinogen: Made in the liver. Largest in size of the plasma proteins. plays key role in blood coagulation. Makes up around 4% of plasma proteins. Under certain conditions fibrinogen molecules interact to form large, insoluble strands of fibrin, this substance provides the basic framework for a blood clot.
List the characteristics and the functions of red blood cells(Erythrocytes).
Red blood cells make up approx 45% of blood volume, which is known as the ‘hematocrit’.
They have a biconcave shape-basically round, with a centre that is depressed in comparison to its edges-this helps in the transportation of gases by increasing the surface area of the cell, allowing more diffusion.
This shape also ensures the cell membrane is nearer to the haemaglobin which carries oxygen, inside the cell.
When mature, erythrocytes are bound by a plasma membrane.
RBCs are about one-third haemoglobin, the protein gives their red colour.
During RBC formation they shed their nuclei as they mature allowing more room for haemoglobin, however as they then lack a nucleus they are unable to synthesise proteins or divide to form more cells.
RBCs produce adenosine triphosphate(atp) through glycolysis(anaerobic mechanism) because they do not have mitochondria and therefore consume none of the O2 carried in their haemoglobin.
They have almost no organelles and contain mostly antioxidant enzymes and structural proteins, which allow them to change shape, and return to their original shape afterward.
networks of proteins, primarily one called Spectrin, are attached to the cytoplasm of RBC plasma membranes, maintaining the biconcave shape; it forms a net allowing RBC’s to bend, turn, become more concave as needed, to move through tiny capillaries
RBC formation is controlled by negative feedback, via the hormone erthropoietin.
RBC’s supply the body tissues with oxygen, which they pick up from the alveoli of the lungs.
Describe the functions of haemoglobin.
Haemoglobin is responsible for the ability of the RBC’s to transport O2 and CO2, and most O2 carried in the blood is bound to Haemoglobin
Carries oxygen inside RBCs and makes up about 1 third of each RBC.
Gives RBCs their red colour when it easily and reversibly binds with oxygen to form oxyhemoglobin-bright red, 3 dimensional structure
When oxygen is released, deoxyhaemoglobin(reduced haemoglobin) is formed-darker red.
Approx. 20% of CO2 transported by the blood is combined with haemoglobin(carbaminohaemoglobin), however the CO2 binds to the amino acids of the globin portion, of the haemoglobin, instead of to the haem portion. This process occurs more easily when the haemoglobin is dissociated from O2(its ‘reduced state’).
Loading of CO2 occurs in the tissues, with transport occurring from the tissues to the lungs, where it can be eliminated from the body.
An RBC does not use any of the oxygen carried by the haemoglobin carried within it.
Iron is required for haemoglobin synthesis and RBC production.
Anaemia is caused by too little haemoglobin or too few RBCs.
Haemoglobin does not break into fragments, and so does not leak out of the bloodstream through the capillaries, preventing changes in blood viscosity and osmotic pressure.
Haemoglobin breaks down into heme and globin, with the heme then decomposing into iron and biliverdin.
Categorise the various White Blood Cells/Leukocytes on the basis of their structure and functions
The 5 types of WBCs in circulating blood are:
Neutrophils:
- Make up 50-70% of the Leukocytes in adults.
- Approx. twice size of Erythrocytes
- Have small granules.
- Older neutrophils or ‘segs’ have lobed nuclei in 3-6 segments connected by thin chromatin strands.
- Because of structure may be referred to a polymorphonuclear, or simply as a ‘poly’
- Younger neutrophils or ‘bands’ have C-shaped nuclei.
- Phagocytise small particles.
- Highly mobile and usually first type of WBC to arrive at a site of injury.
- Very active cells, attacking and digesting bacteria
- Active phagocytes that are chemically attracted to areas of inflammation and primarily target bacteria and certain fungi by process known as ‘respiratory burst’, the cells metabolise O2, creating strong oxidising substances like hydrogen peroxide/bleach, which kill invaders.
- Short life span - 10 hours, when they actively engulf debris or a pathogen, they may only last 30 minutes.
- Each Neutrophil dies after engulfing between 1 and 2 dozen bacteria.
- As Neutrophils break down, they release chemicals that attract other Neutrophils to the site.
- mixtures of dead neutrophils and cellular debris, form ‘Pus’ - associated with infected wounds
Eosinophils:
- Make up just 2-4% of circulating Leukocytes.
- Coarse, same sized granules, resembling lysosomes, and are filled with a specific type of digestive enzymes.
- Have bilobed(just 2 lobes) nuclei.
- Similar in size to Neutrophils(twice size of Erythrocyte).
- Particularly effective against multicellular parasites, such as:
- parasitic flukes-flatworms, tapeworms
- roundworms-hookworms, pinworms-which are too big to engulf
- Number circulating Eosinophils dramatically increase during parasitic infection, allergic reaction, and asthmatic conditions.
- Help control allergic reactions and inflammation.
Basophils:
- Similar to Neutrophls/Eosinophils but are more irregular.
- Account for less than 1% of circulating Leukocytes.
- They migrate to sites of injury and cross the capillary endothelium to accumulate in damaged tissues, where they release the inflammatory chemical Histamine, which dilates the blood vessels, and attracts other WBC’s to the area of inflammation.
- Also release Heparin, a compound that prevents blood clotting.
- Stimulated Basophils release these chemicals into the interstitial fluids.
- These chemicals enhance the local inflammation initiated by Mast cells.
- Cytoplasm of Basophils hold Histamine filled granules that are large and coarse.
- Nuclei of Basophils are usually S or U shaped and have 1 or 2 visible constrictions.
- Will bind to immunoglobin E, which is the antibody that causes Histamine release.
Monocytes:
- Largest type of blood cells, up to 3 times as large as RBC’s.
- Nuclei may be kidney-shaped, lobed, oval or round.
- Abundant cytoplasm.
- Make up 3-8% of circulating Leukocytes.
- Live for either weeks or months.
- A single monocyte will remain in the circulation for only about 24 hrs before it enters the peripheral tissues, where it becomes a tissue macrophage - aggressive phagocyte important in defence against viruses, chronic infections, and intracellular bacterial parasites.
- Often attempt to engulf items as large as themselves.
- When involved in phagocytosis, they release chemicals that attract and stimulate Neutrophils, Monocytes and other phagocytic cells.
Lymphocytes:
- Only a little larger than RBC’s.
- Large round nuclei, inside thin cytoplasm rim.
- Make up 20-30% of circulating Leukocytes.
- May live for years.
- Continuously migrate from the bloodstream, through the peripheral tissues, and back to the bloodstream.
- At any given moment most of boy’s Lymphocytes are in other connective tissues and organs of the lymphatic system.
- Named because of their close association with the lymph nodes, spleen and other lymphoid tissues.
- Circulating blood contains 2 functional classes of Lymphocytes:
- B-cells/B-Lymphocytes - responsible for humoral immunity, which is a specific defence mechanism involving production of antibodies. Activated B-cells differentiate into plasma cells, specialising in antibody secretion.
- T-cells/T-Lymphocytes - responsible for cell-mediated immunity and activation of B-cells. They act directly against tumour cells and virus-infected cells.
Describe the function and production of platelets.
- Platelets or thrombocytes are incomplete cells arising from megakaryocytes(extremely large red bone marrow cells)that become fragmented
- Plasma membranes from each megakaryocyte fragment seal quickly around their cytoplasm to form the platelets.
- Formation of platelets is known as Thrombocytopoiesis.
- They lack nuclei.
- They are approx. one-fourth the size of a Lymphocyte and less than half the size of an Erythrocyte.
- Live for around 10 days
- Able to circulate freely and are inactivated during this activity by prostacyclin and nitric oxide from endothelial cells of the blood vessels.
- Approx one-third of the body’s platelets are stored in the spleen and other vascular organs instead of in the bloodstream.
- These reserves can be mobilised during a circulatory crisis like severe bleeding.
- Their function is primarily to block injuries to damaged blood vessels and to start forming clots.
- This is accomplished by sticking to the damaged site and forming a temporary plug to seal the broken area.
- Platelet holds granules containing many chemicals used for clotting, including:
- enzymes
- adenosine diphosphate
- platelet-derived growth factor
- calcium ions
- serotonin
Discuss mechanisms that control blood loss after an injury.
The stoppage of bleeding is known as haemostasis.
Haemostasis can be broken down into 3 steps:
Vascular spasm/Vasospasm
Platelet plug formation
Coagulation/Blood clotting
Explain Vasospasm.
When a smaller blood vessel is cut or broken, smooth muscles in its walls contract, and loss of blood slows nearly immediately.
Has the potential to completely close the ends of a severed vessel.
Lasts approx. 30 mins. and is also known as the vascular phase of haemostasis.
The endothelial cells contract to expose the basement membrane/collagen to the bloodstream.
Chemical factors and local hormones are released by endothelial cells, along with endothelins, which are peptide hormones that stimulate smooth muscle contraction, promoting the vascular spasms.
They also stimulate endothelial cell division, smooth muscle cell division, and fibroblast division to accelerate repair of the damaged tissue.
Explain platelet plug formation.
A platelet plug forms because of platelet aggregation, and blood begins coagulating.
Platelets release serotonin to contract smooth muscle in the vessel, reducing blood loss.
In platelet adhesion, the platelets sticks to rough surfaces and connective tissue collagen under the endothelial blood vessel lining.
They also stick to each other to form a platelet plug in the area of the vessel injury.
Larger breaks may require a blood clot to stop bleeding.
Growth of the platelet plug is limited by several important factors:
- the endothelial cells release a prostaglandin known as prostacyclin, which inhibits platelet aggregation.
- WBCs entering the area release inhibitory compounds.
- Adenosine diphosphate near the platelet plug is broken down by circulating plasma enzymes.
- Compounds such as serotonin inhibit platelet plug formation once they are present in high quantities.
- The development of a blood clot strengthens the platelet plug but isolates the platelet plug from the general circulation.
Explain Coagulation.
The formation of a blood clot.
Require biochemicals known as clotting factors or procoagulants.
Some clotting factors promote coagulation, others inhibit it, so a delicate balance between the 2 types is achieved to address the specific injured tissue.
Many present proteins or pro enzymes control vital reactions in the clotting response.
Calcium ions and Vitamin K are important for nearly all the coagulation process. Adequate amounts of Vitamin K must be present in the liver for it to synthesise prothrombin and other clotting factors.
The most important event in coagulation is the conversion of the plasma protein fibrinogen into the insoluble threads of the protein called fibrin.
The first step is the release of tissue thromboplastin, resulting in the production of prothrombin activator.
Prothrombin is an alpha globulin made in the liver, and is always present in blood plasma.
Prothrombinase converts prothrombin into thrombin which causes fibrinogen to be cut into sections of fibrin.
This fibrin then joins to form long threads.
The threads stick to surfaces of damaged blood vessels to create a mesh that traps blood cells and platelets, resulting in a blood clot.
Clear, yellowish liquid called serum remains after formation of the clot, which is plasma minus its clotting factors.
More prothrombinase becomes present if tissue damage is more severe.
Continual clotting occurs to stop greater damage, however can only work for a short time as it interrupts the stability of the body’s internal environment.
Excess thrombin is carried away to avoid the formation of a massive blood clot.
As a result, blood coagulation occurs in blood that is moving slowly or not at all.
Clotting stops where a clot contacts circulating blood flow.
Blood clots in ruptured vessels are invaded by fibroblasts to produce fibrous connective tissue and seal the break.
Clots that form in tissues as a result of blood leakage are known as haematoma’s, which disappear over time.
This process requires the plasma protein plasminogen to be converted to plasmin, an enzyme that digests threads of fibrin and other proteins involved in clotting.
What substances control coagulation?
Certain substances deactivate of remove clotting factors as well as other stimulatory agents from the blood to control coagulation.
Examples of these substances include:
- Plasma anticoagulants such as antithrombin III.
- Heparin which is released by basophils and mast cells.
- Aspirin.
- Thrombomodulin which is released by endothelial cells, binds to thrombin, and converts it to an enzyme that activates protein C, which deactivates clotting factors and helps to form plasmin.
- Prostacyclin which inhibits platelet aggregation and opposes thrombin and adenosine diphosphate.
- Alpha-2-macroglobulin which inhibits thrombin.
- C1 inactivator which inhibits several intrinsic clotting factors.
What is retraction of the clot?
Syneresis/clot retraction is process where by the torn edges of a damaged vessel are pulled closer together.
This reduces bleeding and stabilises the site of injury.
It also reduces the size of the damaged area, so that fibrocytes, endothelial cells, and smooth muscle cells can continue the repair process.
