Glossary: Body Fluids & Circulation | Biology for Grade 11 PDF Download

Blood

• Blood: Blood is a special connective tissue consisting of a fluid matrix, plasma, and formed elements. 

Lymph (Tissue Fluid)

• Plasma: (Blood – All blood cells = Plasma) The liquid part of blood which is straw coloured, viscous fluid and contains about 90-92% of water and 6-8% proteins.
• Lymph: A clear yellowish, slightly alkaline, coagulable tissue fluid, containing white blood cells (Only lymphocytes), a liquid resembling blood plasma.
• Serum: Blood plasma from which fibrinogen and other clotting factors have been removed. (Plasma– (fibrinogen & other clotting factor) = blood serum.
• Formed elements: Erythrocytes, leucocytes and platelets are collectively called formed elements and they constitute nearly 45 per cent of the blood.
• RBC: Erythrocytes or red blood cells (RBC) are the most abundant of all the cells in blood. RBCs are formed in the red bone marrow in the adults. RBCs are devoid of nucleus in most of the mammals and are biconcave in shape. 
• Haemoglobin: RBC have a red coloured, iron containing complex protein called haemoglobin.
• Leucocytes: Leucocytes are also known as white blood cells (WBC) as they are colourless due to the lack of haemoglobin. They are nucleated and are relatively lesser in number which averages 6000-8000 mm–3 of blood. Leucocytes are generally short lived. We have two main categories of WBCs – granulocytes and agranulocytes.
• Platelets: Platelets also called thrombocytes, are cell fragments produced from megakaryocytes (special cells in the bone marrow). Blood normally contains 1,500,00-3,500,00 platelets mm–3.
• Universal donors: Group ‘O’ blood can be donated to persons with any other blood group and hence ‘O’ group individuals are called ‘universal donors’.
• Universal recipients: Persons with ‘AB’ group can accept blood from persons with AB as well as the other groups of blood. Therefore, such persons are called ‘universal recipients’.
• Rh negative & Rh positive: The Rh antigen similar to one present in Rhesus monkeys (hence Rh), is also observed on the surface of RBCs of majority (nearly 80 per cent) of humans. Such individuals are called Rh positive (Rh+ve) and those in whom this antigen is absent are called Rh negative (Rh-ve).

Circulatory Pathways

• Open circulatory system: Open circulatory system is present in arthropods and molluscs in which blood pumped by the heart passes through large vessels into open spaces or body cavities called sinuses.
• Closed circulatory system: Annelids and chordates have a closed circulatory system in which the blood pumped by the heart is always circulated through a closed network of blood vessels.
• Cardiac Cycle: This sequential event in the heart which is cyclically repeated is called the cardiac cycle and it consists of systole and diastole of both the atria and ventricles.

Double Circulation

• Systemic circulation: Systemic circulation provides nutrients, O₂ and other essential substances to the tissues and takes CO₂ and other harmful substances away for elimination.
• Hepatic portal system: A unique vascular connection exists between the digestive tract and liver called hepatic portal system. The hepatic portal vein carries blood from intestine to the liver before it is delivered to the systemic circulation. 

Regulation of Cardiac Activity

• Myogenic: Normal activities of the heart are regulated intrinsically, i.e., auto regulated by specialised muscles (nodal tissue), hence the heart is called myogenic.

Disorders of Circulatory System

• High Blood Pressure (Hypertension): Hypertension is the term for blood pressure that is higher than normal (120/80).
• Angina: It is also called ‘angina pectoris’. A symptom of acute chest pain appears when no enough oxygen is reaching the heart muscle.