This MCQ module is based on: Blood Groups Coagulation Lymph
TOPIC 67 OF 90
Blood Groups Coagulation Lymph
🎓 Class 11
Biology
CBSE
Theory
Ch 15 – Body Fluids and Circulation
⏱ ~14 min
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Blood Groups, Coagulation of Blood and Lymph
Blood of human beings differs in certain aspects, though it appears to be similar. Various types of grouping of blood have been done, and two such groupings — the ABO and Rh — are widely used all over the world. This part covers both, then the mechanism that stops a wound bleeding, and finally the second body fluid of the chapter's title.
15.1.3 Blood Groups
15.1.3.1 ABO grouping
ABO grouping is based on the presence or absence of two surface antigens — chemicals that can induce immune response — on the RBCs, namely A and B. Similarly, the plasma of different individuals contains two natural antibodies, which are proteins produced in response to antigens.
| Blood group | Antigens on RBCs | Antibodies in plasma | Donor's group |
|---|---|---|---|
| A | A | anti-B | A, O |
| B | B | anti-A | B, O |
| AB | A, B | nil | AB, A, B, O |
| O | nil | anti-A, B | O |
During blood transfusion, any blood cannot be used; the blood of a donor has to be carefully matched with the blood of a recipient before any blood transfusion, to avoid severe problems of clumping (destruction of RBC).
The two special cases. Group ‘O’ blood can be donated to persons with any other blood group, and hence ‘O’ group individuals are called ‘universal donors’. 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’.
The rule behind the whole table — learn this, not the rows. Read every row as answering one question: does the recipient's plasma contain an antibody against any antigen on the donor's red cells? If yes, clumping follows; if no, the transfusion is safe.
Now the two special cases become obvious rather than memorised. Group O red cells carry no antigen at all — there is nothing for any recipient's antibody to attack, so O can go to everyone. But group O plasma carries both anti-A and anti-B, so an O recipient will attack A, B and AB cells and can receive only O. Group AB is the exact mirror: its plasma carries no antibodies, so it can receive from all; but its red cells carry both antigens, so it can donate only to AB. Notice that the antigen and antibody in any one person are always complementary — nobody carries an antibody against his own antigen, or his blood would destroy itself.
Now the two special cases become obvious rather than memorised. Group O red cells carry no antigen at all — there is nothing for any recipient's antibody to attack, so O can go to everyone. But group O plasma carries both anti-A and anti-B, so an O recipient will attack A, B and AB cells and can receive only O. Group AB is the exact mirror: its plasma carries no antibodies, so it can receive from all; but its red cells carry both antigens, so it can donate only to AB. Notice that the antigen and antibody in any one person are always complementary — nobody carries an antibody against his own antigen, or his blood would destroy itself.
15.1.3.2 Rh grouping
Another antigen, the Rh antigen, similar to one present in Rhesus monkeys (hence Rh), is also observed on the surface of RBCs of the 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).
An Rh⁻ᵛᵉ person, if exposed to Rh⁺ᵛᵉ blood, will form specific antibodies against the Rh antigens. Therefore, Rh group should also be matched before transfusions.
Erythroblastosis foetalis
A special case of Rh incompatibility (mismatching) has been observed between the Rh⁻ᵛᵉ blood of a pregnant mother with Rh⁺ᵛᵉ blood of the foetus. The sequence matters, so follow it in order:
- Rh antigens of the foetus do not get exposed to the Rh⁻ᵛᵉ blood of the mother in the first pregnancy, as the two bloods are well separated by the placenta.
- However, during the delivery of the first child, there is a possibility of exposure of the maternal blood to small amounts of the Rh⁺ᵛᵉ blood from the foetus.
- In such cases, the mother starts preparing antibodies against Rh antigen in her blood.
- In case of her subsequent pregnancies, the Rh antibodies from the mother (Rh⁻ᵛᵉ) can leak into the blood of the foetus (Rh⁺ᵛᵉ) and destroy the foetal RBCs.
- This could be fatal to the foetus, or could cause severe anaemia and jaundice to the baby. This condition is called erythroblastosis foetalis.
The prevention. This can be avoided by administering anti-Rh antibodies to the mother immediately after the delivery of the first child.
Why the first child escapes but the second does not. The whole condition turns on timing. In the first pregnancy the placenta keeps the two bloods well separated, so the mother's immune system never meets the Rh antigen and makes no antibody. Exposure happens only at delivery — by which time the first child is already born and safe. The antibodies the mother then makes persist, so the next Rh⁺ᵛᵉ foetus faces a mother already armed against it. The treatment works by exploiting the same timing: giving anti-Rh antibodies immediately after the first delivery destroys the foetal cells that leaked across before the mother's own immune system can respond to them, so no lasting antibody is ever produced.
15.1.4 Coagulation of Blood
When you cut your finger, the wound does not continue to bleed for long. Blood exhibits coagulation or clotting in response to an injury or trauma. This is a mechanism to prevent excessive loss of blood from the body.
The clot. The dark reddish brown scum formed at the site of a cut is a clot or coagulum, formed mainly of a network of threads called fibrins, in which dead and damaged formed elements of blood are trapped.
The cascade, read backwards
The chapter describes the sequence from the end towards the beginning, which is actually the clearest way to see it:
- Fibrins are formed by the conversion of inactive fibrinogens in the plasma by the enzyme thrombin.
- Thrombins, in turn, are formed from another inactive substance present in the plasma called prothrombin.
- An enzyme complex, thrombokinase, is required for the above reaction.
- This complex is formed by a series of linked enzymic reactions (cascade process) involving a number of factors present in the plasma in an inactive state.
What starts it, and what it needs. An injury or a trauma stimulates the platelets in the blood to release certain factors which activate the mechanism of coagulation. Certain factors released by the tissues at the site of injury also can initiate coagulation. And one ion is indispensable: calcium ions play a very important role in clotting.
Why a cascade rather than a single reaction? Two reasons, both worth stating in an answer. First, amplification: at each step one activated molecule switches on many molecules of the next, so a minute injury signal produces enough fibrin to seal a wound within seconds. Second, control: because every factor waits in an inactive state and several separate steps must each be triggered, blood cannot clot by accident inside an intact vessel. A single-step system would be either too slow or far too dangerous.
15.2 Lymph (Tissue Fluid)
As the blood passes through the capillaries in tissues, some water along with many small water soluble substances move out into the spaces between the cells of tissues, leaving the larger proteins and most of the formed elements in the blood vessels.
Interstitial fluid. This fluid released out is called the interstitial fluid or tissue fluid. It has the same mineral distribution as that in plasma. Exchange of nutrients, gases, etc., between the blood and the cells always occurs through this fluid.
Lymph. An elaborate network of vessels called the lymphatic system collects this fluid and drains it back to the major veins. The fluid present in the lymphatic system is called the lymph. Lymph is a colourless fluid containing specialised lymphocytes, which are responsible for the immune responses of the body. Lymph is also an important carrier for nutrients, hormones, etc. Fats are absorbed through lymph in the lacteals present in the intestinal villi.
| Feature | Blood | Lymph |
|---|---|---|
| Colour | Red, from haemoglobin in RBCs | Colourless |
| RBCs | Present — 5–5.5 million mm⁻³ | Absent |
| WBCs | All five types present | Mainly specialised lymphocytes |
| Platelets | Present | Absent |
| Proteins | Rich — 6–8 per cent, including the larger proteins | Less — the larger proteins stay behind in the vessels |
| Minerals | Na⁺, Ca⁺⁺, Mg⁺⁺, HCO₃⁻, Cl⁻ etc. | Same mineral distribution as in plasma |
| Direction of flow | Circulates in a closed circuit through the heart | Flows one way — tissues → lymphatic system → major veins |
| Main functions | Transport of respiratory gases, nutrients, wastes, hormones; clotting | Immune responses; carrier for nutrients and hormones; absorption of fats in the lacteals of the intestinal villi |
The insight hidden in Section 15.2. Blood never touches a tissue cell. Exchange between blood and cells always occurs through the tissue fluid — blood stays inside the capillary, a filtrate leaves it, and that filtrate is the medium in which cells actually live. Lymph is therefore not a separate invention but the same fluid on its return journey, collected and drained back to the veins. That also explains its composition at a glance: it lacks RBCs, platelets and the larger proteins precisely because those were too big to leave the capillary in the first place. You do not have to memorise the differences; they follow from how lymph is made.
📐 Activity 15.2 — Work out transfusion compatibility for yourself
What to do. Draw a 4×4 grid with donor groups A, B, AB and O across the top and the same four recipient groups down the side. For every one of the sixteen cells, decide whether the transfusion is safe or will cause clumping, applying only one rule: is there an antibody in the recipient's plasma directed against an antigen on the donor's red cells? Do not use Table 15.1 while you work; use it afterwards to check.
Predict: how many of the sixteen combinations will be safe? And which single group appears most often as a safe donor?
| Recipient ↓ | Donor A | Donor B | Donor AB | Donor O |
|---|---|---|---|---|
| A (anti-B) | Safe | Clumps | Clumps | Safe |
| B (anti-A) | Clumps | Safe | Clumps | Safe |
| AB (nil) | Safe | Safe | Safe | Safe |
| O (anti-A, anti-B) | Clumps | Clumps | Clumps | Safe |
Ten of the sixteen are safe, and the grid reproduces Table 15.1's “Donor's Group” column exactly: A can receive A, O; B can receive B, O; AB can receive AB, A, B, O; O can receive O only.
The group that appears most often as a safe donor is O — in all four rows. That is the whole meaning of universal donor: group O blood can be donated to persons with any other blood group, because O red cells carry no antigen for any recipient's antibody to attack. And the row with all four cells safe is AB, the universal recipient, whose plasma contains nil antibodies.
One caution to add. Compatibility is not symmetrical. O can give to A but A cannot give to O. Students who try to memorise pairs rather than apply the rule invariably get this backwards. And in practice the Rh group should also be matched before transfusions, since an Rh⁻ᵛᵉ person exposed to Rh⁺ᵛᵉ blood will form specific antibodies against the Rh antigens — so the real number of compatible combinations is smaller than this grid suggests.
🎯 Interactive: Transfusion checker
Can safely receive from: A, O
Group A has antigen A on its RBCs and anti-B antibody in its plasma. It therefore attacks any red cell carrying antigen B, which rules out B and AB donors, but accepts A and O.
🎯 Competency-Based Questions
Scenario: In a hospital, an accident victim of blood group B, Rh negative, urgently needs blood. The blood bank has units of A positive, B positive, O negative and AB negative. Separately, a woman who is Rh negative and whose husband is Rh positive has just delivered her first child, who is Rh positive. A third patient is on a drug that lowers blood calcium.
Q1. Which unit or units can be given to the accident victim, and why? L3 Apply
Only the O negative unit. Two tests must both be passed. For ABO: the recipient is group B, whose plasma carries anti-A, so A and AB donors are ruled out; the safe donors for group B are B and O. For Rh: the recipient is Rh negative, and an Rh⁻ᵛᵉ person, if exposed to Rh⁺ᵛᵉ blood, will form specific antibodies against the Rh antigens, so the B positive unit is unsafe. That leaves O negative, which passes both tests — and which is why O negative is the blood of choice in emergencies.
Q2. What must be done for the woman who has just delivered, and why now rather than later? L3 Apply
She should be given anti-Rh antibodies immediately after the delivery of the first child. Timing is everything: during the delivery of the first child there is a possibility of exposure of the maternal blood to small amounts of the Rh⁺ᵛᵉ blood from the foetus, and if that happens, the mother starts preparing antibodies against the Rh antigen in her blood. The injected anti-Rh antibodies destroy those leaked foetal cells before her own immune system can respond and commit to making antibodies permanently. Delay it, and she will be sensitised for life, putting every later Rh⁺ᵛᵉ pregnancy at risk of erythroblastosis foetalis.
Q3. Fill in the blanks: Fibrins are formed from inactive ______ by the enzyme ______, which is itself formed from ______ by the enzyme complex ______. ______ ions play a very important role in clotting. L1 Remember
fibrinogens; thrombin; prothrombin; thrombokinase; Calcium (Ca²⁺).
Q4. Predict the effect on the third patient, whose blood calcium has been lowered, and explain why blood donated into a tube containing a calcium-binding chemical does not clot. L4 Analyse
The patient will show impaired clotting and bleed for longer from any injury, because calcium ions play a very important role in clotting — they are required at several steps of the cascade process that builds thrombokinase and hence thrombin. Remove or bind the calcium and the cascade stalls partway, so no fibrin network forms and no clot appears. This is exactly the principle behind collection tubes and blood-bank bags: a chemical that binds calcium keeps donated blood liquid for storage. Note what the example proves — the clotting factors themselves are all present and intact; the system fails for want of a single ion, which is a good illustration of how a multi-step cascade can be blocked at any link.
Q5. “Lymph is just blood that has leaked out, so it is not really a separate body fluid.” Evaluate. L5 Evaluate
The claim is right about the origin and wrong about the conclusion.
What is right. Lymph really does come from blood. As the blood passes through the capillaries in tissues, some water along with many small water soluble substances move out into the spaces between the cells, and the lymphatic system collects this fluid and drains it back to the major veins. Its composition follows directly from that origin: it has the same mineral distribution as plasma, and it lacks RBCs, platelets and the larger proteins simply because those were left behind in the blood vessels, being too large to filter out. So its differences from blood need no separate explanation.
Why it is nevertheless a distinct fluid with distinct functions. (i) It is the only medium through which blood and cells actually communicate — exchange of nutrients, gases, etc., between the blood and the cells always occurs through this fluid. Blood never touches a tissue cell. (ii) It carries out an immune function that blood's own route cannot: lymph contains specialised lymphocytes responsible for the immune responses of the body, circulating through a network built for surveillance. (iii) It performs a digestive function blood cannot: fats are absorbed through lymph in the lacteals present in the intestinal villi, bypassing the blood capillaries entirely. (iv) Its flow is one-way, tissues to veins, not a circuit.
The fair verdict: lymph is derived from blood but is not blood. NCERT's own chapter title settles the point — Body Fluids and Circulation, plural, with lymph named as another fluid used for the transport of certain substances. Shared origin does not make two things identical, any more than a river and the rain that fed it are the same thing.
What is right. Lymph really does come from blood. As the blood passes through the capillaries in tissues, some water along with many small water soluble substances move out into the spaces between the cells, and the lymphatic system collects this fluid and drains it back to the major veins. Its composition follows directly from that origin: it has the same mineral distribution as plasma, and it lacks RBCs, platelets and the larger proteins simply because those were left behind in the blood vessels, being too large to filter out. So its differences from blood need no separate explanation.
Why it is nevertheless a distinct fluid with distinct functions. (i) It is the only medium through which blood and cells actually communicate — exchange of nutrients, gases, etc., between the blood and the cells always occurs through this fluid. Blood never touches a tissue cell. (ii) It carries out an immune function that blood's own route cannot: lymph contains specialised lymphocytes responsible for the immune responses of the body, circulating through a network built for surveillance. (iii) It performs a digestive function blood cannot: fats are absorbed through lymph in the lacteals present in the intestinal villi, bypassing the blood capillaries entirely. (iv) Its flow is one-way, tissues to veins, not a circuit.
The fair verdict: lymph is derived from blood but is not blood. NCERT's own chapter title settles the point — Body Fluids and Circulation, plural, with lymph named as another fluid used for the transport of certain substances. Shared origin does not make two things identical, any more than a river and the rain that fed it are the same thing.
🧠 Assertion–Reason Questions
For each pair choose: (A) Both A and R are true and R is the correct explanation of A. (B) Both A and R are true but R is not the correct explanation of A. (C) A is true but R is false. (D) A is false but R is true.
Assertion (A): Group O individuals are called universal donors.
Reason (R): Group O RBCs carry neither the A nor the B antigen, so no recipient's natural antibody can attack them.
Answer: A. Both are true and the reason is the correct explanation. Note the asymmetry: O plasma carries both antibodies, so an O recipient can still receive only O blood.
Assertion (A): Erythroblastosis foetalis usually affects the second or a later Rh positive child rather than the first.
Reason (R): In the first pregnancy the two bloods are well separated by the placenta, and exposure of maternal blood to foetal Rh positive blood occurs only during delivery.
Answer: A. Both are true and the reason explains the assertion. The mother is sensitised at the first delivery, so her antibodies threaten only subsequent Rh positive foetuses.
Assertion (A): Lymph contains RBCs and platelets in the same proportion as blood.
Reason (R): Lymph is formed when water and small water soluble substances move out of the capillaries, leaving the larger proteins and most of the formed elements behind.
Answer: D. The assertion is false — lymph is colourless and lacks RBCs and platelets. The reason is true and is precisely why: the formed elements are too large to leave the blood vessels.
Coming next. Part 3 takes up Section 15.3 and 15.3.1 — open and closed circulatory patterns, the evolutionary progression of the vertebrate heart from two chambers to four, and the full anatomy of the human heart including its valves and nodal tissue.
Frequently Asked Questions - Blood Groups, Coagulation and Lymph
What is ABO blood grouping based on?
On the presence or absence of two surface antigens, A and B, on the RBCs. Antigens are chemicals that can induce an immune response, and the plasma of different individuals contains two natural antibodies, anti-A and anti-B, which are proteins produced in response to antigens.
Which blood group is the universal donor and which the universal recipient?
Group O is the universal donor, because its RBCs carry no antigen, so O blood can be donated to persons with any other blood group. Group AB is the universal recipient, because its plasma contains no antibodies, so such persons can accept blood from AB as well as all other groups.
What is the Rh factor?
An antigen similar to one present in Rhesus monkeys, hence Rh, found on the RBCs of nearly 80 per cent of humans, who are called Rh positive. Those lacking it are Rh negative. An Rh negative person exposed to Rh positive blood forms specific antibodies against the Rh antigens, so Rh must be matched before transfusions.
What is erythroblastosis foetalis and how is it prevented?
It occurs when an Rh negative mother, sensitised during the delivery of her first Rh positive child, produces Rh antibodies that in a subsequent pregnancy leak into the blood of an Rh positive foetus and destroy its RBCs. This can be fatal to the foetus or cause severe anaemia and jaundice. It is prevented by administering anti-Rh antibodies to the mother immediately after the delivery of the first child.
Why is the first Rh positive child usually unaffected?
Because the Rh antigens of the foetus do not get exposed to the mother's Rh negative blood during the first pregnancy, as the two bloods are well separated by the placenta. Exposure happens only during delivery, by which time the first child is already born.
How does blood clot?
Fibrins are formed by conversion of inactive fibrinogens in the plasma by the enzyme thrombin. Thrombin is formed from the inactive plasma substance prothrombin, a reaction requiring the enzyme complex thrombokinase, which is itself built by a cascade of linked enzymic reactions involving factors present in plasma in an inactive state.
What initiates blood coagulation and what role does calcium play?
An injury or trauma stimulates the platelets to release certain factors that activate the coagulation mechanism, and certain factors released by the tissues at the site of injury can also initiate it. Calcium ions play a very important role in clotting, which is why binding calcium keeps donated blood liquid.
What is tissue fluid, and what is lymph?
Tissue or interstitial fluid is the fluid that moves out of the capillaries into the spaces between tissue cells, carrying water and small water soluble substances but leaving larger proteins and most formed elements behind. It has the same mineral distribution as plasma, and all exchange between blood and cells occurs through it. The lymphatic system collects this fluid and drains it back to the major veins, and the fluid within that system is called lymph.
What are the functions of lymph?
Lymph is a colourless fluid containing specialised lymphocytes responsible for the immune responses of the body. It is also an important carrier for nutrients and hormones, and fats are absorbed through lymph in the lacteals present in the intestinal villi.
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