Anatomy of Blood PDF

# ANATOMY AND PHYSIOLOGY ## BLOOD The blood is a fluid connective tissue, a special fluid responsible for connecting one part of the body to the other through the help of blood vessels. They carry lots of substances to all parts of the body. The blood is reddish to pinkish in colour. When the bloo...

# ANATOMY AND PHYSIOLOGY ## BLOOD The blood is a fluid connective tissue, a special fluid responsible for connecting one part of the body to the other through the help of blood vessels. They carry lots of substances to all parts of the body. The blood is reddish to pinkish in colour. When the blood is only oxygenated, it appears bright or pinkish, but it is low in oxygen, it appears dull. The blood has a metallic taste, slightly alkalinic with ph of 7.4 and contributes about 7% of the total weight, the volume is between 5-6 liters, slightly lower in the female. ## GENERAL FUNCTION OF BLOOD The blood has a wide range of function which include ### Transportation Function - The blood transports oxygen from the lungs to all parts of the body. - It transports nutrients from the GIT and all storage site to all parts of the body for metabolic processes - It transports metabolic waste to areas or site where it is excreted and removed from the body - It transports hormones from where it is produced to target cells, tissues, organs system which might be close or distant. ### Protective function - The blood primarily involve in providing defense against invasion of microorganism. - Preventing blood loss. When a blood vessel is damaged, blood platelets and plasma proteins initiate clot formation, halting blood loss. ### Regulatory function - They help maintain and regulate body temperature by transporting heat from site of production to less heated regions: - They is involved in the regulation and maintenance of our body PH value (acid-base balance) - The contribute in the regulation of body fluid in the blood ## COMPONENT OF THE BLOOD When the sample of the blood and centrifuged, it is observed that the blood is made up of two components, namely: - The blood plasma - The blood cells ### 1. Blood Plasma The blood plasma is a strawed colour fluid contributing about 55% of the total volume of blood. The blood plasma is lighter in weight and found on the upper aspect of the centrifuged sample. The contents of the blood plasma are: - **Water:** Water is the major content of blood plasma, contributing about 90-92% of the total plasma volume, and it forms the solvent of the blood plasma in which other contents are dissolved in. - **Plasma Protein**: The plasma protein is one of the major content of the blood plasma as it serves varieties of functions. It contribute about 7% of the total blood volume, and normally retained within the blood due to their large size to pass through the pores of the blood capillaries. They help in maintaining osmotic pressure of the blood. There are three broad classification of plasma protein - **Albumins**. They are the most abundant of all plasma protein and contribute about 60% of the total plasma protein with primary function of maintaining normal osmotic pressure. They are also involved in transportation of free fatty acids, some drugs and steroid hormones like the glucocorticoids. - **Globulins**. They contribute about 30-36% of the total plasma protein. The globulins contribute in the formation of antibodies that help prevent activities of microorganisms. The globulins are used as antibodies. Examples of the globulins are those that give rise to the alpha, beta and gamma globulins. - **Blood clotting factor**. The clotting factors are the ones responsible for coagulation when there is damage to blood vessels or hemorrhage. They prevent loss of blood. Clotting factor contribute about 4-10% of the total plasma protein and chief example is fibrinogen. - **Nutrients**: Nutrients such as glucose, amino acids and fatty acids gotten from carbohydrate, protein and fat metabolism respectively are found in circulation inside the blood plasma. These nutrients are needed for cellular and tissue survival and building up. - **Waste metabolic product**: Waste products gotten from metabolic activities are gotten also seen in the blood plasma. Example of such products are drugs, urea, uric acid, creatinin, ammonium salts etc. - **Gases**: Gases such as oxygen ($O_2$) and carbondioxide ($CO_2$) necessary for celluar respiration are seen in the blood plasma. The oxygen are transported from the lungs to tissues while the carbondioxide are transported from tissues back to the lung to be removed from our body - **Electrolytes**: These are ions needed to keep our body in ph balance, also they combine and recombine to give rise to important compound in our body. Examples of electrolytes are hydrogen ion, sodium ions, potassium ions, chloride ions, bicarbonate ions, calcium ions, hydroxyl ions, etc. - **Hormones**: Hormones such as oxytocin, growth hormone, adrenalin and noradrenaline, progesterone, insulin and many more are all found in the blood plasma. Enzymes also can still be found in the blood plasma ### 2. Blood Cells The blood cells are made materials contributing about 45% of the total blood volume. They are made of various cells originating from the same parent cells. The blood cells are broadly grouped into three - **Erythrocytes** - **Leucocytes** - **Thrombocytes** The following should be noted: - All blood cells originate from the same parent cells known as pleuripotent stem cells (PSC) or haemocytoblast. - The formation of all blood cells from the pleuripotent stem cell is known as haemopoiesis. - The formation of blood cells takes place in the red bone marrow or cancellous bone. - The hormone responsible for the formation of all blood cell types is generally known as hemopoietin, secreted by the kidney. __Assignment:__ Draw a schematic demonstrating haemopoiesis ## ERYTHROCYTE The erythrocyte also known as the red blood cell is a biconcave disc cell that is thick in the peripheral area but thin in the central area and having a diameter of 7µm. The rbc is the most numerous of all blood cell types saddled with the responsibility of transporting oxygen from the lungs to cells and tissue and transport some percentage of carbondioxide from tisues and cells back to the lungs. The rbc is very flexible, passing through the blood capillaries due to the present of spectrin. __A cross section of the red blood cell and approximate dimensions__ <start_of_image> scale: 1.7 µm, 7.8 µm, 11 µm ## FORMATION OF THE RED BLOOD CELL Erytheopoiesis is the formation of the red blood cells which takesplace in the red bone marror, lasting a period of seven days. The hormone stimulating the formation of the rbc is the erythropoietin. This hormone stimulates the pleuripotent stem cells to differentiate to form highly mitotic proerythroblast which give rise to erythroblast. The erythroblast is converted to normoblast before becoming reticullocyte, also known as the immature rbc. The reticulocytes are released into the blood where they circullate for 1-2 days where they lose their nucleus and become mature rbc/erythrocytes. As the cell is undergoing these modificationall changes, they gradually begin to lose their organelles and create way for the formation of haemoglobin, also, the size of the cells reduce. The raw materials needed for the complete formation of the rbc and haemoglobin are iron, Vit B12, folic acid and also proteins which are gotten from our normal daily and diary food. Haemoglobin formed is a complex protein compound having high affinity for oxygen and can easily lose it at the tissue and capillary level. One haemoglobin can transport four oxygen atom. It has been observed that one rbc contains approximately about 280 haemoglobins and this implies that a singular red blood cell can transport about 1.12billion oxygen atom. __Assingment:__ - What are the factors that stimulate erythropoiesis - What are the effects of iron, folic acid, Vit B12 or intrinsic factor missing in the formation of the rbc? - Explain how oxygen and carbondioxide are transported in the blood ## DESTRUCTION OF THE RED BLOOD CELL The destruction of rbc is known as haemolysis/hemolysis. The life span of the rbc is said to be about 120 days or 4 months, hence they lose their flexibility. Organs such as bones, spleen and liver help in monitoring age, once they capture the old rbc, the phagocytic recticuloendothelial cells target the haemoglobin breaking it to haem and globin component. The globin joins protein pool and used for other protein purposes while the haem part is broken into two further parts of iron and biliverdin. Iron is recycled to form new rbcs or sent to the liver for storage. The biliverdin is broken down to bilirubin and sent to the liver where they are undergo metabolic reaction and broken to give rise to stercobilin, and component in bile that gives our characteristic faecal waste colour and urinobilinogen, transported to the kidney to give our urine the amber characteristic colour. ## BLOOD GROUPING This is simply classifying people's according to the type of antigen found on the surface of plasma membrane of the rbc. There are various method of blood classification but the most used and easily understood is the ABO system of blood grouping. This system classifies people blood into four groups which are: - **Blood group A** also known as **Antigen A**. this type antibody B (anti-B) - **Blood group B/Antigen B** produces antibody A (Anti-A) - **Blood group AB/Antigen AB** does not produce any antibody of A or B - **Blood group O**, does not have any of antigen A or B on the surface of the plasma membrane but will produce Antibodies A and B (Anti-A and B). In respect to blood donation, it is important that donors blood match with receipients. When they do not, the blood reacts and clumps or agglutinate. From statistics, it has been observed that people of blood group A, B and AB constitute about 55% of the entire human population while people of blood group O constitute the remaining 45%. Below is the table of compatibility of blood using just the ABO system of blood grouping | DONORS | RECIPIENTS | |:---:|:---:| | A | A ✓ | | A | B X | | A | AB ✓ | | A | O ✓| | B | A X | | B | B ✓ | | B | AB ✓ | | B | O X | | AB | A X | | AB | B X | | AB | AB ✓ | | AB | O ✓| | O | A ✓ | | O | B ✓ | | O | AB ✓ | | O | O ✓ | The above table shows that blood group O is the universal donor but a unitary recipient because it receives blood form no other group type except its' type while blood group AB is refered to as the universal recipient as it receives blood from all blood group but a unitary donor because it donates blood to only it type. The term universal can be misleading when you consider other factors or antigen. But if you are referring to only the ABO system of blood, then the above is valid for universal donor and recipient. ## RHESUS FACTOR Rhesus (Rh) is an extra antigen/protein found on the surface of the red blood cell, sometimes Antigen D, first discovered in monkeys known as Rhesus. This extra factor is observed to be seen in about 85% of human population while the remaining 15% are said to be rhesus negative or are said to not have rhesus factor. Rhesus positive (Rh*) persons can receive blood from both rhesus positive or negative persons while a rhesus negative (Rh) person cannot collect blood from a rhesus positive individual because they will produce anti-rhesus antibody which can lead to agglutination or clumping. The table below demonstrates the compatibility of blood groups in transfusion putting rhesus factor into consideration. | DONORS | RECIPIENTS | |:---:|:---:| | A+ | A+ ✓ | | A+ | A- ✓ | | A+ | B+ ✓ | | A+ | B- ✓ | | A+ | AB+ ✓ | | A+ | AB- ✓ | | A+ | O+ ✓ | | A+ | O- ✓| | A- | A+ X | | A- | A- ✓ | | A- | B+ X | | A- | B- X | | A- | AB+ X | | A- | AB- X | | A- | O+ X | | A- | O- X | | B+ | A+ X | | B+ | A- X | | B+ | B+ ✓ | | B+ | B- ✓ | | B+ | AB+ ✓ | | B+ | AB- ✓ | | B+ | O+ ✓ | | B+ | O- ✓ | | B- | A+ X | | B- | A- X | | B- | B+ X | | B- | B- ✓ | | B- | AB+ X | | B- | AB- X | | B- | O+ X | | B- | O- X | | AB+ | A+ ✓ | | AB+ | A- ✓ | | AB+ | B+ ✓ | | AB+ | B- ✓ | | AB+ | AB+ ✓ | | AB+ | AB- ✓ | | AB+ | O+ ✓ | | AB+ | O- ✓ | | AB- | A+ X | | AB- | A- X | | AB- | B+ X | | AB- | B- X | | AB- | AB+ X | | AB- | AB- ✓ | | AB- | O+ X | | AB- | O- X | | O+ | A+ ✓ | | O+ | A- ✓ | | O+ | B+ ✓ | | O+ | B- ✓ | | O+ | AB+ ✓ | | O+ | AB- ✓ | | O+ | O+ ✓ | | O+ | O- ✓ | | O- | A+ X | | O- | A- X | | O- | B+ X | | O- | B- X | | O- | AB+ X | | O- | AB- X | | O- | O+ X | | O- | O- ✓ | From the above table, O- assumes the universal donor and unitary recipient while blood group AB+ assumes the universal recipient and unitary donor. ## ERYTHROBLASTOSIS FETALIS It is a condition in which the mother's defensive cells produces antibodies that severely destroys the red blood cells of the fetus due to incompatibility of the mother and child's blood. The destruction of the fetal RBC can be mild, severe or fatal depending on the extent of destruction. Most often times, children suffering from erythtoblastosis fetalis are very anemic, weak and if medical interventions are not given to the born child, it could lead to the eventuall death of the child. This only comes into manifestation when the mother's blood is rh- and the fetus is rh+. It is only possible if the defense system of the mother has been stimulated by previous pregnancy of a rh+ child. On certain circumstances, at any point the mother becomes pregnant with a rhesus negative child, the child does not suffer from the disease of the new born but vice versa for a rhesus positive fetus. To prevent the attack, rhesus negative mothers are given an injection generally referred to as Rhogam. This injection is given once to the Rh- mother at 28 weeks of pregnancy to prevent complication and given 72 hours after birth should be child Rh+. Should the woman be Rh+, irrespective of the fathers' blood type, no harm is done to the child as Rh+ mothers do not produce antirhesus antibody, rather they can be receptive to embryo/fetus of any blood group (Rh-/Rh+). __Assignment:__ Read and write on the prevention of erythroblastosis fetalis. __Assignment:__ Draw a table of Reb blood cell count in the blood (hematocrit) ## LEUCOCYTES The leucocytes are known as the white blood cells (WBC) and responsible for providing defence and immunity. WBCs all originate from hemocytoblast under the influencing hormone of leucopoietin produced by the kidney. The process of formation of the wbc is known as leucopoiesis. The white blood cells are the largest sized cells of the blood but contribute only 1% of the total volume of the blood volume. There basically to types of leucocytes: - **Granular leucocytes** - **Agranular leucocytes** ### **Granular Leucocytes** Granular leucocytes also known as polymorphonuclear leucocytes are cells that have multilobed nucleus, granules in their cytoplasm and are relatively small in size and very active in fighting against micro-organisms. The process of formation is known as granulopoiesis where they undergo series developmental changes from myeloblast to meylocytes then to specific individual granulocytes. There are three types of granular leucocytes that are classified according to the colour of dye they picked while staining them. They are - **Neutrophils** - **Eosinophils** - **Basophils** #### **Neutrophils** The neutrophils has the following characteristics features: - They are the most numerous of the white blood cells accounting for about 40-75% of the total wbc volume - They are the smallest in size of the leucocytes - They have upto six lobed nucleus - Their granules are lysosomes, giving the neutrophils the ability to digest and destroy anything they engulf - They are very fast and very active - They are phagocytic and help in scavenging or remove dead cells, damaged tissues and mirco-organisms - They are always the first to arrive at injury sites - When there is injury, the neutrophils squeezes out of the blood capillary, a process known as diapedases. - They invite other neutrophils to injury sites or site of infection by chemical method known as chemotaxis. - they form inflammatory exudates also known as pus - they have a life span ranging from 6-9 hours. #### **Eosinophils** This group of white blood cell is less active when compared to the neutrophils and less numerous, accounting for 1-6% of the total white blood cells. They have the ability to phagocytize their prey but are specialized in elimination of parasitic worms such as flat worms (tape and fluke worms), round worms (pin and hook worms). When their prey are too large for them to engulf, they attach themselves to the prey and release their potent granules containing digestive enzymes. They have bilobed nucleus, they are commonly found also residing in loose areolar connective tissue and adipose tissue. They are also found in allergic sites or allergic inflammation such as asthmatic airway and skin allergies. They generally promote tissue inflammation where they release series of toxic chemicals. #### **Basophils** The basophils are the rarest and contribute just less than 1% of the total wbc volume. Their cytoplasm contains granules packed with histamine and heparin. The histamine is a vasodilator which promotes blood flow to injury sites and attracts other white blood cells to injury and infected sites while the heparin is an anticoagulant which delays blood clotting promoting blood flow and supply of nutrients and all necessary factors need healing and repair of damaged tissues. The basophils are stimulated to release their contents by allergens, which binds to antibody receptors on the basophil cell membrane ### **AGRANULOCYTES** These type of white blood cells are said not to have granules in their cytoplasm having singular but large nucleus. The agranulocytes is made up of monocytes and lymphocytes, the both account for about 25-50% of total volume of wbc. #### **Monocytes** The monocytes are the largest cells of the leucocytes with an average diameter of 18µm with the nucleus U-shaped or kidney shaped. They accounting for about 2-10% of the whole leucocytes. Some monocytes circulate in the blood and are actively motile and phagocytic while others migrate into tissues where they develop into macrophages. The monocytes and macrophages have the ability to secrete interleukin 1 which; - acts on the hypothalamus, causng a rise in body temperature, especially when there is an infection - stimulate the liver to produce globulin, an important component needed for immunity - enhances the activation of T-lymphocytes to fight against infections #### **Monocyte-Macrophage System** This is simply made up of monocytes that are trapped in specific organs to keep them immuned and protected against the activities of micro-organism. These monocytes are active, hence becoming macrophages and sometimes referred to as the recticuloendothelial cells. The monocyte-macrophages trapped in various organs are referred by different names but of the same origin as the monocytes. They are: - **Kupffer cells** or hepatic macrophages are in the liver - **Masangial cell** are in the kidney - **Alveolar macrophages** are in the lungs - **Osteoclast** are in the bone - **Langerhans cells** are in the skin - **Synovial cells** are in the joints - **Microglia/microglial cells** are in the brain and spinal cord - **Reticular cells/sinus lining cells** are found in the spleen, lymph nopdes and thymus gland #### **Lymphocytes** The lymphocytes are smaller in size but do have larger nuclei that occupies most of the cytoplasm and has diameter of 5-17µm. The lymphocytes account for about 20-50% of the total leucocyte volume. They are found circulating the blood in small quantity but are found densely populated In lymphatic/lymphoid tissues/organs such as lymph nodes, spleen, where they play important role immunity. There are two types of lymphocytes but they originate from the same pleuripotent stem cell. - **B-lymphocyte** also known as **Bone lymphocyte** because it gets it immune-competence and maturity in the bone. - **T-lymphoctes** also known as **Thymus lymphocytes** because they get their immune-competence and maturity in the thymus. The immunocompetence of both lymphocytes enable them to react and respond to antigen such as bacteria, fungi, pollen from flowers, large molecules of some drugs like aspirin and penicillin, abnormal cells or infected cells, etc. __Assignment:__ Draw a table of white blood cell count ## **Thrombocytes** The thrombocytes are also known as blood platelets, derived from the fragmentation of megakaryocytes in the red bone marrow. They are non nucleated disc having a diameter of 2-4µm. The thrombocytes are responsible for maintaining hemostasis (ceasation of blood/blood clotting)) due to varieties of chemicals they can release to stop loss of blood from an individual should there be hemorrhage. The formation of blood platelets is known as thrombopoiesis, triggered by a fall of platelets, which stimulates the release of thrombopoietin by the kidney. This hormone is transported to the red bone marrow where it comes in contact with the hemocytoblast/pluripotent stem cell for the formation of blood platelets. The normal blood platelets count is 200-350 × 10º/I (200000-300000/mm³) while the lif span of blood platelet is around 8-11days It should be noted that the site for the storage of blood platelets is the spleen with about 1/3rd stored in it for emergency situation and to arrest excessive bleeding. Also, the spleen is the sight for destruction of blood platelets. ## Hemostasis This is involves overlapping series of activities that lead to the healing of blood vessels and prevention of excessive loss of blood. This process, depending on the extent of damage is very fast, as fast as 15 seconds after injury. The process of hemostasis are: - **Vasoconstriction/ Vascular Spasm**. This is when the blood vessels constrict so as to reduce the diameter of the cut or injured blood vessels. This is due to the blood platelets releasing serotonin (5-hydroxytryptamin) which constrict the blood vessels, hence reducing blood flow through it. The cells of the damaged blood vessel release its complementary chemical such as thrombaxane, contributing in the constriction of the blood vessel. - **Platelet Plug Formation**. The platelets at the injured sight of the blood vessel releases some chemotaxins such as adenosine diphosphate (etc) which attract other blood platelets until they become so much aggregated to form a blockade or plug which trap blood and prevent the loss of blood. This plug is not strong and any increased pressure can push out the formed plugs by the platelets, hence the need to speed up the healing process to permanently heal the vessel. It should noted that the process of releasing ADP is known as chemotasis. - **Coagulation**. This is characterized by cascade or complex chemical reaction that leads to the formation of fibers that permanently heals the blood vessels. These reactions make use of several clotting factors as listed below. - **Fibrinogen** - **Prothrombin** - **Tissue factor** - **Calcium** - **Labile factor** or **proaccelerin** or **Ac-globulin** - This factor is not in use as it was found to be part of another factor i.e factor V. It was initially called accelerin - **Stable factor** also known as **proconvertin** - **Antihaemophilic globulin** (AHG) or **antihaemophilic factor** - **Christmas factor** also known as **plasma thromboplastin component** (antihaemophilic factor B) - **Stuart Prower factor** - **Plasma thromboplastin antecedent** also known as **antihaemophlic factor C** - **Hageman factor** - **Fabrin stabilizing factor** - Just note that there is no factor VI. Vitamin K is very essential for the synthesis of factors II, VII, IX and X - The above mentioned factor does not necessarily act in the order of arrangements, rather there are named according to their discoveries. The activities and chemical reaction of the clothing factors eventually leads to formation of prothrombin activator which is the first step in the common pathway. There are two pathways in blood clotting - **Intrinsic pathway** which is formed by contribution from the blood platelets. This is the major contributor coagulation - **Extrinsic pathway** which is the contribution from the damaged tissue of the blood vessels - **Fibrinolysis**. This is the process of breaking fibrin thread so as to smoothen the healed blood vessels and prevent excess blood clotting. This mechanism is the checker for the positive feedback mechanism of coagulation. As the blood vessel becomes healed, the plasminogen activator is stimulated to act on plasminogen converting it to plasmin. It is the plasmin that breaks down excess thread of fibrin into soluble substances that are seen as waste product, hence removed by the leucocytes through phagocytosis. ## **Control of Coagulation** It should be noted that coagulation utilizes positive feedback mechanism, by implication, it is one way process until the stimulus is remove and in this case the rough blood vessels. Therefore, the following are the control of coagulation: - The smoothened blood vessels help in stopping blood clotting because the thrombocytes are no more adherent to the blood vessel - Binding of thrombin to a special thrombin receptor on the cells of lining the blood vessels. This binding help in deactivating the further action of thrombin - The presence of natural anticoagulants inactivate blood clotting. Example of anticoagulant are heparin, tissue pathway inhibitor, protein Cprotein S, e.t.c. __Assignment:__ What are the factors that can influence or delay haemostasis?