1- Specialized connective tissue bLood. Veterinary histology sciences

Veterinary histology

1. Blood

2. BLOOD Blood is a type of connective tissues. The blood consist of : Solid part → blood cells. Liquid part → plasma The blood cells are: Red blood cells (RBCs) or erythrocytes. White blood cells (WBCs) or leukocytes. Platelets or thrombocytes .

3. Functions of Blood 1) Transport of : Gases e.g. oxygen & carbon dioxide. Nutrients e.g. glucose, amino acids & free fatty acids Waste products e.g. urea & uric acid. Hormones (e.g. catecholamines , insulin & cortisol) 2) Defense by WBCs.. 3) Homeostasis: maintains constant internal environment.( e.g body temperature) 4) Hemostasis: prevention of blood loss & maintenance of blood in fluid state. 5) Regulation of acid base balance 6) Storage function .

4. The volume is 5 liters(7% of body weight). Erythrocytes(45%), leukocytes+ platelets(1%) blood plasma(54%).

5. Erythrocytes Are nonnucleated cells and are the most numerous blood cells. Are the corpuscles that impart the red color to the blood. Developed as true cells but before entering the circulation extrude their nucleus. Losing the capacity for DNA directed protein synthesis. Their mitochondria & other membrane –limited organs are also lost.

6. RBC’S (Erythrocytes) Shape - a biconcave disc with large surface area Can change shape No Nucleus / organelles Contains hemoglobin Primary Function = Transport oxygen from the lungs to the cells of the body & assist with CO 2 removal

7. Mature erythrocytes are specialized to transport oxygen and carbon dioxide. The life span of erythrocytes is approximately 120 days, after which the worn-out cells are removed from the blood and phagocytosed by macrophages in the spleen, liver, and bone marrow. About 1% of circulatory red blood cells are immature and they are known as reticulocyte. Hemoglobin the respiratory pigment(33%) Alpha, beta, gamma & delta.

8. leukocytes White blood corpuscles are true cells. They are categorized according to granules (granular & a granular). According to the shape of their nucleus (mononuclear or polymorphonuclear). The granular leukocyte classified according to the staining affinities of their granules (neutrophil, eosinophil, basophil). A granular leukocyte 2 types ( monocytes and lymphocytes).

9. Granulocytes. A granulocytes .

10. Function of WBCs Defense against : Bacterial infections Parasitic infections Viral infections. Tumors .

11. Neutrophils Neutrophils are the commonest type of white blood cell found in a blood smear. They make up 60 - 70% of the total amount of white blood cells. They are 12-14 um diameter (so look bigger than the surrounding red blood cells). The nucleus is segmented or lobulated (3-5 lobules) connected by narrow strands. The neutrophil cytoplasm contains fine violet or pink granules.

12. Neutrophils have a short life span. They circulate in blood for about 10 hours and then enter the connective tissue, where they survive for another 2 or 3 days.Neutrophils are active phagocytes.

13. Eosinophils Eosinophils constitute approximately 2 to 4% of the blood leukocytes. Eosinophils are characterized by their cytoplasm, which is filled with distinct, large, eosinophilic (bright pink) granules. The nucleus in eosinophils is bilobed. Eosinophils also have a short life span. They remain in blood for up to 10 hours and then migrate into the connective tissue, where they remain for up to 10 days. Eosinophils are also phagocytic cells, they increase in number during parasitic infestation and allergic conditions.

14. Basophils The basophils constitute less than 1% of the blood leukocytes and are therefore the most difficult to find and identify in a blood smear. They are more variable in size, less densely packed, and stain dark blue or brown. The nucleus in basophils is bilobed. Their granules contain histamine and heparin. Their function is similar to that of mast cells ( involved in immune responses to parasites).

15. Lymphocytes A granular leukocytes have few or no cytoplasmic granules and exhibit round to horseshoe shaped nuclei. Lymphocytes vary in size from cells smaller than erythrocytes to cells almost twice as large. Lymphocytes are classified according to size into 3 types: 1-small lymphocyte 2- medium size lymphocyte 3- large lymphocyte Lymphocytes are classified according to function into 2 types : 1- T. lymphocyte (matured in the thymus) 2- B. lymphocyte ( develop in the bone marrow). Lymphocytes have a variable life span, from days to months. Lymphocytes are essential for immunologic defence of the organism.

16. Monocytes Monocytes are the largest a granular leukocytes. Monocytes constitute approximately 3 to 8% of the blood leukocytes. The nucleus varies from round or oval to irregular or kidney-shaped and stains lighter than the lymphocyte nucleus. Monocytes can live in the blood for 2 to 3 days, after which they move into the connective tissue. After entering the connective tissue, monocytes become powerful phagocytes. At the site of infection, monocytes differentiate into tissue macrophages and then destroy bacteria, foreign matter, and cellular debris

17. Platelets Platelets or thrombocytes are not blood cells. They are the smallest, nonnucleated formed elements in the blood and appear in the blood of all mammals. Platelets are cytoplasmic fragments of megakaryocytes, the largest cells in the bone marrow. Exhibit two concentric zones, a thin pale-blue hyalomere , & a thicker central region, the chromoere or granulmere . Their main function is to promote blood clotting.