Welcome to lab classes in basic histology Introducing lab class (in spanish) .
The aim of these lab classes is to provide students with educational resources necessary to acquire basic practical skills of each subject, ie recognize, locate and describe the types of cells, tissues and structures of each organ.
Each of these practical sessions are structured around three main elements:
- Definition of learning objectives.
- Description of structures, tissues and cell types of the system.
- Exercises location of structures / cell types in virtual slide (which is in other link).

LEARNING OBJECTIVES
- Differentiate the various components of blood.
- Identify the erythrocytes.
- Identify the different types of leukocytes, granulocytes as well agranulocytes.
- Differentiate neutrophils, eosinophils and basophils.
- Differentiate between lymphocytes and monocytes.

HANDBOOK
Blood is a highly specialized connective tissue where the cells are suspended in a characteristic extracellular fluid called plasma. A healthy adult individual found approximately five liters of blood circulating through the rhythmic contractions of the heart. The cells or cellular components circulating in plasma are the erythrocytes or red blood cells, the white blood cells and platelets.
When blood leaves the circulatory system, for whatever reason, plasma proteins react with each other to produce a clot, which includes the formed elements and a yellowish fluid called serum, which contains growth factors released by platelets during clot formation, and biological properties that confer very different from the plasma.
By centrifuging a blood sample treated with heparin to prevent clotting process, we see that the blood can be separated into different layers that reflect the heterogeneity of components that comprise it. The fraction of the centrifuge hematocrit are called erythrocytes, which warehouses at the bottom of the tube and represent approximately 45% of the total volume of blood from a healthy adult. Hematocrit above found a weak layer of leukocytes and platelets called the buffy coat, and represent 1% of total blood volume. Finally, the top of the tube containing the liquid portion of blood, plasma, representing 54% of total blood volume.

PLASMA
Plasma is an aqueous solution of pH 7.4 with 8-10% of its volume constitute by molecules of different molecular weight. Plasma proteins represent 7% of total dissolved in the blood components, which include nutrients, nitrogenous waste products, hormones and electrolytes.
The low molecular weight components of blood are in equilibrium with the interstitial fluid of tissues through the walls of blood capillaries, making the analysis of the composition of blood plasma is a good indicator of the main components of the extracellular fluids .
The main protein in blood plasma include:
- Albumin. The most abundant plasma protein. It is synthesized in the liver and its main function is to maintain the osmotic pressure of the blood.
- Alpha and beta globin. Released by the liver and other cells, including transferrin, fibronectin, prothrombin and other clotting factors, lipoproteins and other proteins from different tissues.
- Gamma-globulins. Immunoglobulins are secreted by plasma cells.
- Complement proteins. Complement is a set of factors related to inflammation and destruction of microorganism.
- Fibrinogen. It is the largest plasma protein and is also synthesized by the liver. During coagulation polymerizes and becomes insoluble, creating a network of fibers that block the passage of blood through the circulatory vessel walls.

BLOOD CELLS
ERYTHROCYTE Eritrocytes
The red blood cells are anucleated biconcave cells of 8 mm in diameter and are in a blood concentration of 3.9 to 5.5 million per microliter in woman and 4.1 to 6 million in man . One of the main features of this cell type is that they have lost theyr organelles and only are composed of a plasma membrane containing a cytoskeleton, hemoglobin, the protein responsible for transporting oxygen and glycolytic enzymes. Cells are relatively flexible to adapt to the different diameters of the capillaries.
Red cells are relatively short-lived cells, and that after about 120 days, senescent erythrocytes are removed by phagocytosis in the spleen, liver, bone medulla, or they can be destroyed by hemolysis in the spleen, being replaced by reticulocytes, which completed the synthesis of hemoglobin and complete their development 1 or 2 days after entering the bloodstream. Reticulocytes represent between 1 and 2% of total red blood cells.
The main function of erythrocytes is the transport of oxygen and carbon dioxide between you different tissues and lungs. When hemoglobin combines with oxygen to form oxyhemoglobin whereas when combined with carbon dioxide form carboxyhemoglobin.

LEUKOCYTES
Leukocytes are classified into granulocytes when they have granules in the cytoplasm, and agranulocytes when not have granules in the citoplamsa. In response to appropriate stimuli, we can find leukocytes in the bloodstream or the residents can be found as the connective tissue.

Granulocytes
These multilobulated nucleus cells have phagocytic capacity. There are three types of granulocytes classifieds as the cytoplasmic granules.
1 - Neutrophils Neutrophils . These lobuled nucleus cells contain primary and secondary specific granules. In a blood smear stained appear faintly pink. They constitute 60-70% of circulating leukocytes, and have an average life of 6-7 hours in the bloodstream and about 4 days in the connective tissue. Neutrophils leave the bloodstream at the level of postcapillary venules and enter the connective tissue where they acquire the ability to kill opsonized bacteria and limit the extent of the inflammatory reaction. The primary granules contain elastase and myeloperoxidase, while secondary granules contain lysozyme and other proteases.
2 - Eosinophils Eosinophils . Like neutrophils, eosinophils have a bilobed nucleus. Their cytoplasm is filled with large granules that take a red stain. They are between 2% and 4% of circulating leukocytes and also have the ability to penetrate into the connective tissue. They are the first line of defense against parasites and are involved in the development of bronchial asthma.
3 .- Basophils. Basophils contain large metachromatic granules, which masks the lobulated nucleus. Represent 1% of circulating leukocytes. When they leave the bloodstream and enter the connective tissue look similar to mast cells Mast cell . Basophils are a very important role in immediately (bronchial asthma) and delayed (allergic skin reactions) hypersensibility.

Agranulocytes
The agranulocytes include lymphocytes and monocytes.
4 .- Lymphocytes Lymphocytes . The cells have a rounded nucleus and a basophilic cytoplasm, which only appears as a thin layer around the core. They fall into two categories, the B lymphocytes (B cells) produced and matured in the bone medulla, and T lymphocytes (T cells) produced in the bone medulla but mature in the thymus. Activated B lymphocytes differentiate into antibody-producing plasma cells. T cells are involved in cell immunity.
5 .- Monocytes Monocytes . Monocytes have an oval-shaped kidney with a small cytoplasmic granules that are not seen with the light microscope. Monocytes circulate in the bloodstream between 12 and 100 hours and then penetrate the connective tissue, where they differentiate into macrophages, acquiring the capacity to phagocytose bacteria, present antigens, and clearing debris. In bone, monocytes differentiate into osteoclasts Osteoclasts under the influence of osteoblasts.

PLATELETS
Platelets are cell fragments of megakaryocytes. Megakaryocytes develop cytoplasmic processes that lead to platelet fragmentation.

EXERCICES
- Identify erythrocytes in the virtual slide Blood smear .
- Differentiate the various types of leukocytes from the erythrocytes in the virtual preparation Blood smear .
- Observe the different morphologies of leukocytes in the virtual slide Blood smear .
- Identify neutrophils in the virtual slide Blood smear .
- Identify eosinophils in the virtual slide Blood smear .
- Identify lymphocytes in the virtual slide Blood smear .
- Identify monocytes in the virtual slide Blood smear .