It is dark red in its deoxygenated form (i.e., returning to the lungs), when hemoglobin is bound to carbon dioxide to form carboxyhemoglobin i.e. inside the veins.

Veins are vessels that bring blood to the heart. Pulmonary veins carry oxygenated blood from the lungs, to the left atrium. There are four pulmonary veins, which extend from the left atrium to the lungs. They are the right superior, right inferior, left superior and left inferior pulmonary veins.

The pulmonary arteries carry deoxygenated blood, from the heart to the lungs. They are the only arteries (other than umbilical arteries in the fetus) that carry deoxygenated blood.

The soluble protein, fibrinogen,in blood plasma is converted into insoluble fibrin, thus preventing blood loss through cuts, etc. Calcium is required for the clotting. 

All of the above mentioned blood vessels carry deoxygenated blood.

Human blood has two parts, fluid and cellular. The fluid part is known as blood plasma, that makes 55% of total blood volume, and the rest are the cellular components. When a sample of blood is centrifuged, results show separation of blood into different layers, based on their density. Three layers are visible after centrifugation is complete. The bottom layer is red colored that is composed of Red Blood Cells (RBCs), above it there's a white band, made up of White Blood Cells (WBCs) and platelets. The third or the topmost layer is a straw colored liquid, that is made up of blood plasma. The cells present in the blood, are also known as formed elements.

Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries. The pulmonary arteries carry deoxygenated blood from the heart to the lungs. They are the only arteries (other than umbilical arteries in the fetus) that carry deoxygenated blood.

The human palatine tonsils and the nasopharyngeal tonsil are lymphoepithelial tissues, located in strategic areas of the oropharynx and nasopharynx, although most commonly the term tonsils refers to the palatine tonsils.

Fibrin (also called Factor Ia) is a fibrous protein, involved in the clotting of blood, and is non-globular. It is a fibrillar protein, that is polymerised to form a mesh, that forms a hemostatic plug or clot (in conjunction with platelets) over a wound site. Fibrin is involved in the following biological processes: signal transduction, blood coagulation, platelet activation and protein polymerization.

An artery is an elastic blood vessel that transports blood away from the heart. There are two main types of arteries: pulmonary arteries and systemic arteries. It has got a thick wall which has three layers.

An artery is an elastic blood vessel that transports blood away from the heart. There are two main types of arteries: pulmonary arteries and systemic arteries. Pulse beat is measured in artery.

The pericardium is the fluid filled sac that surrounds the heart and the proximal ends of the aorta, vena cava and the pulmonary artery. The pericardium has several functions. It keeps the heart contained in the chest cavity. The pericardium also prevents the heart from overexpanding when blood volume increases. Within the pericardium lies the pericardial cavity. This cavity is filled with pericardial fluid, which reduces friction between the pericardial membranes.

Part of the swelling, due to injury or infection, is caused by diapedesis. The white cells are intensely active because apart from destroying bacteria they also work to form a barrier around an infection that can help prevent the rest of the body from becoming infected. In small localized infections, this effect provided by diapedesis can be quite effective. In larger infections, the migrating infection may overpower the migrating white cells.

WBC or leukocytes are the white blood cells. The WBC cells are divided into granulocytes, consisting of eosinophil, basophil and neutrophil and agranulocytes, consisting of lymphocytes and monocytes. The normal WBC count is about 4000-11000/cmm of blood ,with 65% of neutrophil ,4% eosinophil ,0.5% basophil ,23% lymphocyte and 5% monocyte.

Blood is bright red in its oxygenated form (i.e., leaving the lungs), when hemoglobin is bound to oxygen to form oxyhemoglobin i.e. inside arteries.

Blood plasma is the yellow liquid component of blood, in which the blood cells in whole blood, are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid (all body fluid outside of cells). It is mostly water (93% by volume) and contains dissolved proteins, glucose, clotting factors, mineral ions, hormones and carbon dioxide.

The erythrocytes or RBC are the red cells of blood which constitute most of the cellular component of blood. A matured red blood cell cannot divide and the biconcave shape makes gas exchange quicker, due to less distance between center and periphery and and more surface area.The RBC contain hemoglobin, and most of the functions of RBC, like, gas transport, acid-base balance and formation of bilirubin, are due to presence of hemoglobin. RBC's are responsible for the major portion of the viscosity of blood. 

Monocytes are largest agranulocytes with kidney-shaped nucleus and plenty of cytoplasm. They are phagocytic in nature. They represent 3-8% of WBC

Lymphocytes are agranulocytes with round or kidney shaped nucleus and scanty cytoplasm. They are of three types, B-Lymphocytes, T-Lymphocytes and Natural killer cells. B-lymphocytes are stimulated by an antigen and form plasma cells. These plasma cells produce antibodies, which react with antigen, and inactivate them. Lymph mainly consists lymphocytes.

Basophils are granular leukocytes, containing basophilic granules, in the cytoplasm. The cell nucleus is S-shaped. Basophil releases heparin, which prevents clotting of blood and histamine, which causes tissue damage and allergy. They represent 0.5% of WBC

Eosinophils are granular leukocytes, containing acidophilic granules, in the cytoplasm. The nucleus is usually bi-lobed. The cells show amoeboid movement and phagocytic power. The histamine released by this cell helps in combating infection. They represent 2-4% of WBC

Neutrophil are granular leukocytes, containing neutral granules, in the cytoplasm. They represent 60-70%of WBC cells. The cell nucleus is 2-7 lobed. In the neutrophil of human female adjacent to the nucleus, a drumstick like hetero chromatin body is present, called Barr Body. It represents one of the two X chromosomes of female. The primary functions of neutrophil are phagocytosis, ingestion and digestion of invading microorganism.

Eosinophils are granular leukocytes, containing acidophilic granules, in the cytoplasm. The nucleus is usually bi-lobed. The cells show amoeboid movement and phagocytic power. The histamine released by this cell helps in combating infection. They represent 2-4% of WBC

Neutrophils are granular leukocytes, containing neutral granules, in the cytoplasm. They represent 60-70%of WBC cells. The cell nucleus is 2-7 lobed. The primary functions of neutrophil are phagocytosis, ingestion and digestion of invading microorganism.

Neutrophil are granular leukocytes, containing neutral granules in the cytoplasm. They represent 60-70%of WBC cells. The cell nucleus is 2-7 lobed. In the neutrophil of human female adjacent to the nucleus, a drumstick-like hetero chromatin body is present, called Barr Body. It represents one of the two X chromosomes of female. The primary functions of neutrophil are phagocytosis, ingestion and digestion of invading microorganism.