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Blood
Liquid form is connective tissue and is a red red nutritive fluid that circulates in a closed system of blood vessels. Arises from the mesoderm. The main function is to deliver oxygenated blood to tissues and to return venous blood to the lungs for gaseous exchange. Other Functions include
- O2 and COz exchange - Carry oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs
- Nutrition - Transport food materials and nutrients throughout the body
- Excretion - Carry waste products of metabolism from the different body organs to different excretory organs
- Body protection - Act as a defense mechanism against infection through the activities of certain cells and immune bodies in the blood stream
- Assist in the maintenance of a constant body temperature and alkalinity of tissues
- Transport endocrine secretions from one organ to another
General characteristics
Color
โ Red due to hemoglobin โ Aerial blood > oxygenated > bright red โ Venous blood > unoxygenated > dark red/ purplish red
Volume
โ 5 to 6 liters โ 7% to 8% of body weight โ 75ml to 85ml of bld./ kg of body weight โ Normovolemia โ normal blood volume in the body โ Hypervolemia
โ Excessive fluid intake blood (hemorrhage) โ Intravenous injection of fluid (hemolytic anemia) โ Blood transfusion (treatment) โ hypovolumia โ Loss of whole blood โ Loss of RBC โ Loss of plasma โ Loss of water (sweating, diarrhea, vomiting)
Reaction
โ Slightly alkaline pH 7.35 - 7.45 average is 7.
Viscosity
โ Highly viscous โ 3.5 - 4.5 X thicker than water โ fluid's resistance to flow because of the presence of plasma protein and cells
Specific gravity
โ Ratio of the weight of the volume of blood to the weight of the same volume of water held at a temperature of 4ยฐC โ 1.045 - 1.065 average 1. โ cells present in the blood is responsible for increase of specific gravity โ men have a higher specific gravity of blood due to higher RBC count
Composition of blood:
- Liquid portion of blood (55%) a. plasma Plasma is the liquid vehicle of the blood, the intercellular substance of the blood. Plasma is transparent yellow and transports all nutritive materials. Plasma is essentially an aqueous solution of inorganic salts, which is constantly exchanged with the extracellular fluid of body tissues.
b. serum Composition of plasma and serum: water, protein, carbohydrates, salts, vitamins, minerals, electrolytes, hormones, enzymes, lipids
- Solid portion of blood (45%) a. cellular elements - RBC, WBC,Blood platelets b. non cellular elements - chylomicrons,hemoconia or blood dust
โ Capillaries โ Venules โ Veins
Blood vessels
Intricate network of hollow tubes that transport blood throughout the body
Types of blood vessels
โ Arteries โ red blood vessels that carry blood away from the heart โ Veins โ blood vessels that carry blood towards the heart โ Capillaries โ which links the arteries and veins.
Types of artery
- Conducting or Elastic arteries- largest arteries in the body, (Ex: Aorta).These have more elastic fibers than smooth muscles.
- Muscular Arteries / Medium- sized arteries or the Distribution arteries- have more smooth muscles in their walls , delivers blood to skeletal muscles and internal organs (Ex: Radial artery, splenic artery)
- Arterioles- smallest arteries in the body, transport blood from small arteries to capillaries,only one to two layers of smooth muscles
Types of vein
- Large veins- have the thickest walls, EX: superior and inferior vena cava
- Medium - sized vein- same size with medium arteries (Ex: Femoral artery, brachial artery),thin tunica media, few muscle cells
- Venule- smallest size veins, receive blood from the capillaries, poorly developed muscle layer , thinner walls than arterioles
Types of capillaries
- Continuous - do not have fenestrate/ pores Ex: skeletal muscles, nervous system
- Fenestrated - have pores Ex: intestinal villi, kidney glomeruli
3. Tunica externa - outermost tunic. - Composed largely of fibrous connective tissue - To support and protect the vessels. โ Made up of layers of connective tissues โ Chief component are the collagen fibers โ Collagen fibers anchors the blood vessels to nearby organs
Differentiation of histological characteristics between artery and vein
LEUKOCYTES/WHITE BLOOD CELLS
WBC is spherical in shape and provided with a nucleus that varies in shape. WBC is motile, of varying sizes without hemoglobin content. The cytoplasm may contain granules of different kinds.
Classification: There are two types of WBC according to the presence/absence of specific cytoplasmic granules:
- Granular or Granulocytes
- Non granular or Agranulocytes
BLOOD PLATELETS
Blood platelets are small, non-nucleated, non-motile basophilic cells. It is the lightest element of the blood. Blood platelets are cytoplasmic fragments of giant cells or megakaryocytes in the bone marrow that have been detached and carried into the circulation. These cells appear as a flattened disc consisting of two concentric zones:
1. chromomere/granulomere This is the thicker central area, containing small purple staining granules (alpha granules) 2. hyalomere Thin, non granular, homogenous pale blue peripheral zone
The normal value of blood platelets is 200,000 to 400,000/cumm. The life span is 4 to 9 days. Platelets have a variety of functions essential to the normal process of hemostasis. Blood platelets are involved in hemostasis.
1. Red or Non Fatty bone marrow This is found in bone cavities of embryos and immature individuals and is also known as the active bone marrow. This type of bone marrow is crammed with dividing stem cells and the precursor of mature blood cells. The predominance of maturing erythrocytes conferring a deep red color hence the name red bone marrow. Active bone marrow consists of two main components, a framework of reticulin and specialized reticular cells which supports the developing blood cells and a system of interconnected blood sinusoids which drain towards the central vein. 2. Yellow or Fatty bone marrow This is an inactive bone marrow and yellow in color because it is dominated by fat cells.
- ERYTHROPOIESIS
Erythropoiesis is the process of red blood cell formation, which is directed towards producing cells devoid of organelle but packed with hemoglobin. There are three main features in stages of development:
- decreasing cell size
- progressive loss of organelles; the presence of numerous ribosomes at early stages accounts for the marked cytoplasmic basophilia
- progressive increase in the cytoplasmic hemoglobin content
Erythrocytic series:
1. Rubriblast This is the earliest stage of RBC; larger than hemocytoblast; vesicular round nucleus, more basophilic cytoplasm due to increased RNA content.
2. Prorubricytes This is slightly smaller than rubriblast with round nucleus eccentric with a coarse network of dense heterochromatin, intensely basophilic cytoplasm, increase of free ribosomes. 3. Rubricyte This is a cell that acquire a small amount of hemoglobin, cytoplasm shows variation in color, nucleus with a denser chromatin and smaller. 4. Acidophilic normoblast The amount of hemoglobin increases; cytoplasm is acidophilic, cell is smaller with a small densely basophilic staining nucleus. 5. Reticulocyte This cell is without a nucleus, acidophilic cytoplasm with basophilic staining particles which are remnants of nucleus. 6. Erythrocytes
GRANULOPOIESIS
the process of producing granulocytes, a type of white blood cell, within the bone marrow
Granulocytic series:
1. Myeloblast This is a round cell with a round nucleus and fine polychromatic cytoplasmic granules. 2. Promyelocytes This is a round cell with dense peripheral heterochromatin, basophilic cytoplasm with densely scattered azurophilic granules (sky blue). 3. Myelocyte Smaller cell; decrease basophilia of the cytoplasm, eccentric nucleus, appearance of specific granules. 4. Metamyelocyte The cell becomes smaller, nuclei assume a kidney-shaped appearance with specific granules. 5. Band granulocyte The smaller cell and the nucleus is sausage shaped or stab in form.
Hematopoiesis
Hematopoiesis: production , development, differentiation and maturation of all blood cells
Hemopoiesis is the process by which mature blood cells develop film precursor cells. In the human adult, hemopoiesis takes place in the bone marrow mainly of the skull, ribs, sternum, vertebral column, pelvis and the proximal ends of the femur. Before maturity, however, hemopoiesis occurs in other sites at different stages in development. In early embryos, primitive blood cells arise in the yolk sac and later the liver. From the third to seventh months of intra-uterine life, granulocytes and platelet formation begins in the marrow cavities with erythropoiesis becoming established by the seventh month. By birth, hemopoiesis takes place almost exclusive to the bone marrow although the liver and spleen may resume activity in times of need. From birth to maturity, the number of active sites of hemopoiesis in bone marrow diminishes although all bone marrow retains hemopoiesis potential.
The lineage of each blood cell type has been the subject of numerous but only one has gained substantial experimental support, the monophyletic theory. This theory proposes that all blood cell types are derived from a single primitive cell type called hemocytoblast or multipotential (pluripotential) stem cell. The multipotential cells replicate at slow rate differentiating into five discrete types of unipotential stem cells, each committed to a different developmental lineage: granulocytes, lymphocytes, monocytes and platelets.
Prenatal hematopoiesis
3 phases : A. Mesoblastic B. Hepatic C. Myeloid
Post natal hematopoiesis
โ almost exclusively in the bone marrow โ replace the cells that leave the blood stream, die or destroy โ at age 18 red marrow is found only in the vertebra, ribs, sternum, skull bone, pelvis
CHARACTERISTIC OF RBC
Characteristics
โ Biconcave disc (6-8micra in diameter) โ Formed in the bone marrow โ Non-nucleated โ Ave. life span of 30-120days โ Contains hemoglobin โ Oxygen binding pigment responsible for the transport of โ most O2 in the body โ Compound of iron & protein โ Combined readily with O2 to form oxyhemoglobin
Normal Value
โ Males: 5.5-6.5 million/cu.mm โ Females: 4.5-5.5 million/cu.mm
processed cells return to the bone marrow or peripheral lymphoid organs. These cells mediate in cellular immunity.
- Bursa-dependent lymphocytes (B-lymphocytes). These lymphocytes do not pass through the thymus, move directly to the general lymphoid tissue via the blood stream. These cells mediate in humoral immunity and in production of antibodies when exposed to antigens that are present within the body.
i. 2nd most abundant type of WBC in the blood. ii. Smallest cell in the peripheral blood iii. NV: 25-45% iv. Function: involved in humoral & cellular immune response
2. Granulocytes Granulocytes have prominent cytoplasmic granules. Each of the three different types of granulocytes have type specific granules, the names neutrophil, eosinophil being derived from the staining characteristics of these specific granules. The granulocytes have a single multilobulated nucleus.
a. Neutrophil (55 TO 65%) Neutrophil is spherical with multilobulated nucleus (2 - 5 lobes); cytoplasm is with fine faint lilac granules containing alkaline phosphatase and basic proteins (phagocytins) which has an antibacterial property. Neutrophil is involved in phagocytosis in 8 days. i. Has segmented nucleus. 2-5 lobes connected by thin strands of chromatin ii. Cytoplasm contains purple or lilac granules iii. Has affinity towards acid&basic dyes iv. NV: 50-70% v. Function:
- phagocytosis of bacteria.
- Increased in bacterial infection b. Eosinophil (1 - 3 %) Eosinophil is with coarse, reddish orange granules in the cytoplasm. The nucleus is also involved in some aspects of hypersensitivity reactions as they neutralize histamine and also produce a factor called eosinophil derived inhibitor.
c. Basophil (0 - 1%) Basophil is the least common granulocyte and characterized by large, irregular, intensely basophilic granules. The nucleus is elongated and bent in the form of N or S. The granules contain heparin and histamine (vasodilator). Basophil is closely associated with mast cells; both cells are involved in increasing the vascular permeability during inflammation and both bind a particular immunoglobulin, IgE, that is produced by plasma cell. i. NV: 0-1% ii. Function:
- Release heparin, histamine & peroxidase
- Involved in intermediate & delayed hypersensitivity rxn
d. MONOCYTES (3 - 8%) Monocyte is the largest type of WBC in circulation. The cytoplasm is grayish (frosted glass) and the eccentrically located nucleus is crescent-shaped/kidney shaped/bean shaped. Monocyte is
involve in phagocytosis, production of proteolytic enzymes and is essential in the processing of antigens prior to the development of antibodies. The normal value of WBC in the circulation is 5,000 to 10,000/cumm of blood. The life span of WBC is from a week to several hours.
3. Thrombocytes a. Irregular fragments of cells formed in the bone marrow from a much larger cell (megakaryocyte) b. Non-nucleated c. Lightest element of blood d. 2-4ฮผ in diameter e. Difficult to count i. Adhere easily on surface โฆ Easily disintegrates
Thrombopoiesis
โ NV: 150,000-400,000/cu.mm โ Function: โ Maintain the integrity of BV โ Forms hemostatic plugs to stop blood loss from injury vessels โ Release serotonin โ Terminologies โ Thrombocytosis: โ increase number of platelet โ Thrombocytopenia: โ decrease number of platelet
โ blood clotting
