Blood, Blood Groups, Coagulation and Lymph: Quick Revision

A brief note on Blood, Blood Groups, Coagulation and Lymph. Read it before a test. Try each question at the end before you open its answer.

Blood

• Blood: a fluid connective tissue. Plasma is about 55 per cent, and the formed elements are about 45 per cent.
• Plasma: 90 to 92 per cent water and 6 to 8 per cent proteins. Fibrinogen is for clotting, globulins for defence and albumins for the osmotic balance.
• Serum: plasma without the clotting factors.
• Red cells: 4.5 to 5.5 million per mm³, no nucleus in most mammals. Haemoglobin: 12 to 16 g per 100 mL in a woman, 13 to 17 g in a man. They live 120 days and are destroyed in the spleen.
• White cells: 4000 to 11000 per mm³. From most to least: neutrophils, lymphocytes, monocytes, eosinophils, basophils.
• Platelets: 150,000 to 450,000 per mm³, fragments of megakaryocytes, needed for clotting.

Blood groups

• A: antigen A, anti-B. B: antigen B, anti-A. AB: both antigens, no antibodies. O: no antigen, both antibodies.
• Universal donor: O. Universal recipient: AB.
• NCERT gives about 80 per cent of people as Rh positive. The share differs between peoples.
• Rh negative mother, Rh positive foetus: anti-Rh antibodies form at the first delivery and harm a later foetus. This is erythroblastosis foetalis.
• Prevention: anti-Rh antibodies to the mother at once after the first delivery.

Clotting and lymph

• Platelets and damaged tissue release factors. A cascade makes thrombokinase.
• Thrombokinase changes prothrombin to thrombin, with Ca$^{2+}$. Thrombin changes fibrinogen to fibrin. Fibrin traps cells in a clot.
• Tissue fluid is collected by the lymph vessels. Lymph is colourless, has lymphocytes, and returns to the large veins.
• Fats are absorbed into the lacteals of the villi.

A worked example

A sample of 50 mL of blood has 45 per cent formed elements. What is the volume of the plasma?

1. The plasma is $100 - 45 = 55$ per cent of the sample.
2. The volume is $0.55 \times 50 = 27.5$ mL.

Practice with new numbers

A program to try

The program splits a sample of blood into plasma and formed elements.

Mistakes to avoid

• Saying that plasma and serum are the same. Serum has no clotting factors.
• Counting eosinophils or basophils as agranulocytes. Only the lymphocytes and the monocytes are agranulocytes.
• Looking at the antibodies of the donor. Compare the antigens of the donor with the antibodies of the recipient.
• Giving the anti-Rh antibodies to the baby. They are given to the mother.

Check yourself

1. Which antibody is in the plasma of a person of group A?

2. What does thrombin change?

3. Which cells are the second most numerous white cells?

4. What carries the absorbed fat from a villus?

Sources

• Betts J. G. et al. (2022). Anatomy and Physiology 2e, OpenStax, chapter 18.
• World Health Organization (2024). Guideline on haemoglobin cutoffs to define anaemia in individuals and populations.
• NCERT (2023). Biology, Textbook for Class XI, chapter 15.