Week 21 Flashcards
(41 cards)
What are the constituents of human blood?
Red blood cells (Erythrocytes and Reticulocytes)
White blood cells (Granulocytes and Agranulocytes)
Platelets (Thrombocytes)
Plasma
Describe Red Blood Cells (Erythrocytes).
Also known as erythrocytes and reticulocytes.
Produced in bone marrow; immature red blood cells contain a nucleus which they lose as they mature — why? (To maximize space for hemoglobin.)
People with blood loss or iron therapy have an increased reticulocyte count.
Describe the structure and content of mature erythrocytes.
Bi-concave discs: largest surface area and flexible shape.
Contain cytoplasm and haemoglobin.
Living cells — respire but can’t repair — why? (No nucleus or organelles.)
Membrane contains phospholipid bilayer and cholesterol — why? (Structural integrity and fluidity.)
Haemoglobin structure: four protein chains (two alpha, two beta), each with a heme group.
Heme contains a tetrapyrrole (four pyrrole rings — four carbon and one nitrogen atoms arranged in a pentagon).
Because the tetrapyrrole contains a metal ion, it is known as a porphyrin.
Describe Reticulocytes and their maturation.
Released into circulation from the bone marrow and mature within 1–2 days.
Erythroblast (precursor) undergoes chromatin and nuclear condensation, allowing macrophages to carry out enucleation.
Organelles like endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria, and ribosomes are broken down and expelled.
RNA breakdown facilitated by ribonucleases, but some rRNA remains.
Compared to mature RBCs, reticulocytes have greater volume, higher haemoglobin content, lower haemoglobin concentration, and lack the bi-concave shape.
Explain ABO blood groups and inheritance.
Inheritance is co-dominant:
A and B are co-dominant.
O is recessive to both.
RBCs have agglutinogens (antigens) on their surface and agglutinins (antibodies) in plasma.
Combination of matching agglutinogen and agglutinin causes clumping of RBCs.
What antigens and antibodies are present in each ABO blood group?
Blood group A: Antigen A on RBCs, Anti-B antibodies in plasma.
Blood group B: Antigen B on RBCs, Anti-A antibodies in plasma.
Blood group AB: Both A and B antigens on RBCs, no anti-A or anti-B in plasma.
Blood group O: No antigens on RBCs, both anti-A and anti-B antibodies in plasma.
Who can receive or donate blood to whom in ABO groups?
Group O is the universal donor.
Group AB is the universal recipient.
Why? Because of presence or absence of antigens and antibodies.
Explain the D antigen and Rhesus blood groups.
D antigen is the main Rh antigen.
Presence of D antigen = Rhesus positive (Rh+).
Absence of D antigen = Rhesus negative (Rh-).
Rhesus inheritance involves genes C, D, and E (no “d” allele; only D, C, c, E, e — focus only on D here
What happens when Rhesus-negative individuals are exposed to Rhesus-positive blood?
A Rhesus-negative person exposed to Rhesus-positive blood will produce anti-D antibodies.
Subsequent exposure to Rh+ blood causes blood clotting.
How does Rhesus incompatibility affect pregnancy?
If father is Rh+ and baby is Rh+, Rh- mother can form antibodies during pregnancy.
Antibodies can cross the placenta in subsequent pregnancies, causing issues.
Explain Rhesus and blood transfusions.
Rh+ individuals can receive both Rh+ and Rh- blood.
Rh- individuals can only receive Rh- blood.
Multiple Rh+ transfusions to Rh- person can be fatal.
However, ABO incompatibility is usually a more major issue.
What are platelets and what is their role?
Also called thrombocytes.
Made from megakaryocytes.
Cell fragments that aggregate at injury sites.
Initiate the clotting cascade and form a clot.
Contract to pull the clot tighter.
What is the clotting cascade and how is clotting stopped?
Thrombin triggers a positive feedback loop.
Clotting is stopped by:
Protein C (activated by thrombin binding to endothelium) activates Protein S to break down Factors Va and VIIIa (negative feedback).
Liver produces Antithrombin to destroy Factors XIa, Xa, and thrombin.
Tissue Factor Pathway Inhibitor binds and inactivates Factors VIIa and Xa.
What are granulocytes and their types?
Neutrophils: 12-15 µm diameter, multi-lobed nuclei, move via diapedesis, live a few days, secrete chemicals to destroy pathogens and phagocytose.
Eosinophils: 15 µm, two-lobed nucleus, large granules; involved in chronic inflammation, allergies, parasitic infections.
Basophils: 12-15 µm, double-lobed or S-shaped nucleus; similar to mast cells.
Mast cells: Oval/round, immature in blood, mature in tissues; store cytokines, histamine, heparin.
Natural killer (NK) cells: Large granular lymphocytes; detect absence of self-antigens and destroy via cytotoxic granules.
What are agranulocytes?
White blood cells without granular cytoplasm.
Categorized into lymphocytes and monocytes.
What is plasma and what does it contain?
Makes up 55% of blood volume.
91–92% water, 8–9% solids.
Contains:
Coagulants (e.g., fibrinogen)
Plasma proteins (albumin, globulin — maintain colloidal osmotic pressure at ~25 mmHg)
Electrolytes (Na⁺, K⁺, bicarbonate, Cl⁻, Ca²⁺)
Immunoglobulins (for infection defense)
Enzymes, hormones, vitamins.
What are the roles of plasma? (Part 1)
Coagulation: Fibrinogen, thrombin, Factor X involved.
Defense: Immunoglobulins and antibodies fight infections.
Osmotic Pressure Maintenance: Albumin maintains ~25 mmHg pressure.
Nutrition: Transports glucose, amino acids, lipids, vitamins.
Respiration: Transport of oxygen and carbon dioxide.
Excretion: Transports nitrogenous wastes to kidneys, lungs, skin.
Hormones: Carries hormones to target organs.
Acid-Base Balance: Plasma proteins act as buffers.
Temperature Regulation: High specific heat capacity.
Why are circulatory systems necessary in organisms?
Organisms become too big and too thick to rely on diffusion.
Fick’s Law:
Rate of diffusion ∝ (Surface area × Concentration gradient) / Diffusion distance
Describe an open circulatory system.
Blood (haemolymph) leaves vessels and enters tissue spaces.
Blood and interstitial (tissue) fluid are mixed.
Blood is pumped by the ‘heart’ into an open space or haemocoel and returns through ostia (spaces).
In some animals, the heart is a blood vessel that pulses haemolymph through the body by muscular contractions.
Fluid in the haemocoel bathes internal organs and delivers nutrients.
What are the characteristics of an open circulatory system?
No arteries to maintain high pressure of the haemolymph → blood pressure is very low.
Organisms with an open circulatory system typically have:
A relatively high volume of haemolymph
Low blood pressure
Examples include arthropods (e.g., insects, spiders, crabs).
What are the advantages and disadvantages of an open circulatory system?
Advantages:
Requires less energy for distribution than a closed circulatory system.
Disadvantages:
No arteries → blood pressure remains low.
Oxygen takes longer to reach body cells.
Organisms have a lower metabolism and tend to be less active.
There are limits to the size that an organism can reach.
Describe a closed circulatory system.
Blood and interstitial (tissue) fluid are separate; blood remains in vessels.
Blood is pumped by the heart into high-pressure vessels and small thin vessels.
Small thin vessels provide a large surface area and short diffusion distance, allowing exchange of fluid.
The volume of blood remains relatively consistent.
Tissue fluid bathes all cells.
Main functions: gas exchange, hormone and nutrient distribution, and waste elimination.
Found in all vertebrates.
What are the advantages of a closed circulatory system?
Operates with much higher blood pressure, allowing tall organisms to stand up.
More efficient: uses less blood for higher and faster levels of distribution.
Allows a higher metabolic rate.
Efficient distribution of antibodies → stronger immune responses to fight infections.
Describe single circulation.
Blood flows once around the heart for once around the body.
No separation between oxygenated and deoxygenated blood.
No difference in pressure.
Example: fish.
