Blood Composition and Functions Practice Questions
20 free Blood Composition and Functions practice questions for the Physiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
What is the typical percentage of total blood volume occupied by plasma in a healthy adult?
- A 25%
- B 45%
- C 55%
- D 75%
Correct answer: 55%
Plasma typically makes up about 55% of the total blood volume. The remaining 45% consists of formed elements, primarily erythrocytes.
Which plasma protein is the primary contributor to colloid osmotic pressure?
- A Fibrinogen
- B Alpha-globulin
- C Gamma-globulin
- D Serum albumin
Correct answer: Serum albumin
Albumin is the most abundant plasma protein and is too large to pass easily through capillary walls. Its presence creates the osmotic pressure necessary to draw water back into the circulatory system from the interstitial space.
What is the primary site of hematopoiesis in a healthy adult?
- A Liver
- B Spleen
- C Red bone marrow
- D Yellow bone marrow
Correct answer: Red bone marrow
In adults, the production of all blood cells occurs in the red bone marrow, specifically in the axial skeleton and the proximal epiphyses of the humerus and femur. The liver and spleen handle this function primarily during fetal development.
Which of the following is a characteristic feature of a mature human erythrocyte?
- A Presence of a lobed nucleus
- B Large number of mitochondria
- C High rate of aerobic metabolism
- D Distinct biconcave disc shape
Correct answer: Distinct biconcave disc shape
Mature erythrocytes lack a nucleus and mitochondria to maximize space for hemoglobin. The biconcave shape provides a high surface-area-to-volume ratio, facilitating efficient gas exchange.
Which hormone, produced mainly by the kidneys, stimulates the production of red blood cells?
- A Thrombopoietin
- B Erythropoietin
- C Aldosterone
- D Cortisol
Correct answer: Erythropoietin
Erythropoietin (EPO) is released by the kidneys in response to low oxygen levels (hypoxia). It travels to the bone marrow to stimulate the proliferation and differentiation of red blood cell precursors.
Which leukocyte is typically the most numerous in a normal differential white blood cell count?
- A Lymphocytes
- B Monocytes
- C Eosinophils
- D Neutrophils
Correct answer: Neutrophils
Neutrophils generally account for 50% to 70% of the total white blood cell count. They are the 'first responders' to bacterial infections and inflammatory sites.
What is the average lifespan of a circulating red blood cell in the human body?
- A 10 days
- B 30 days
- C 250 days
- D 120 days
Correct answer: 120 days
Erythrocytes circulate for approximately 120 days before they become fragile. They are then trapped and destroyed by macrophages, primarily in the spleen and liver.
Which type of leukocyte is responsible for the production of antibodies?
- A B-lymphocytes
- B T-lymphocytes
- C Basophils
- D Neutrophils
Correct answer: B-lymphocytes
B-lymphocytes, when activated, differentiate into plasma cells. These plasma cells are specialized for secreting soluble antibodies (immunoglobulins) into the blood and lymph.
Which metal ion is found at the center of the heme group in hemoglobin?
- A Magnesium
- B Copper
- C Zinc
- D Iron
Correct answer: Iron
Each heme group contains one ferrous iron (Fe2+) atom. This iron atom is the specific site where one molecule of oxygen binds reversibly.
What is the primary function of platelets (thrombocytes)?
- A Hemostasis and blood clotting
- B Oxygen transport
- C Phagocytosis of bacteria
- D Production of plasma proteins
Correct answer: Hemostasis and blood clotting
Platelets are essential for the formation of the platelet plug during the primary stage of hemostasis. They also release chemicals that promote vascular spasm and trigger the coagulation cascade.
Which condition is characterized by an abnormally high hematocrit, leading to increased blood viscosity?
- A Anemia
- B Leukopenia
- C Thrombocytopenia
- D Polycythemia
Correct answer: Polycythemia
Polycythemia is an excess of red blood cells. This increases the viscosity of the blood, which can slow circulation and increase the workload on the heart.
Serum is essentially identical to plasma EXCEPT for the absence of:
- A Clotting factors
- B Albumin
- C Electrolytes and minerals
- D Globulin proteins
Correct answer: Clotting factors
Serum is the liquid portion of blood remaining after a clot has formed. Because the clotting factors have been consumed to create the fibrin mesh, they are absent from serum.
Which white blood cell releases histamine and heparin to promote inflammation?
- A Basophils
- B Neutrophils
- C Eosinophils
- D Monocytes
Correct answer: Basophils
Basophils contain granules filled with histamine (a vasodilator) and heparin (an anticoagulant). Their release intensifies the inflammatory response and prevents local blood clotting.
Bilirubin is a waste product derived from the breakdown of which component?
- A Heme molecules
- B Globin chains
- C Platelet membranes
- D Plasma globulins
Correct answer: Heme molecules
When red cells are destroyed, the heme is converted into biliverdin and then into bilirubin. Bilirubin is then transported to the liver to be excreted in bile.
Which leukocyte migrates into tissues to become a macrophage?
- A Monocyte
- B Lymphocyte
- C Neutrophil
- D Basophil
Correct answer: Monocyte
Monocytes circulate in the blood for a short time before entering tissues. Once in the tissue, they enlarge and differentiate into highly phagocytic macrophages.
A person with Type AB blood has which of the following on their red blood cell membranes?
- A Both A and B antigens
- B Only A antigens
- C Only B antigens
- D Neither A nor B antigens
Correct answer: Both A and B antigens
The ABO blood group is determined by the presence of antigens on the RBC surface. Type AB individuals possess both A and B antigens and naturally produce no anti-A or anti-B antibodies.
Which of the following is the largest type of white blood cell?
- A Neutrophil
- B Basophil
- C Lymphocyte
- D Monocyte
Correct answer: Monocyte
Monocytes are the largest of all leukocytes, featuring a kidney-shaped nucleus and abundant cytoplasm. They are significantly larger than the granulocytes and lymphocytes.
How many oxygen molecules can a single hemoglobin molecule carry at full saturation?
- A 1
- B 2
- C 4
- D 8
Correct answer: 4
One hemoglobin molecule consists of four polypeptide subunits, each containing a heme group with one iron atom. Therefore, one hemoglobin molecule can bind up to four oxygen molecules.
Which plasma component is responsible for maintaining the pH of blood between 7.35 and 7.45?
- A Bicarbonate buffer system
- B Phosphate buffer system
- C Protein buffer system
- D Hemoglobin buffer system
Correct answer: Bicarbonate buffer system
The bicarbonate buffer system (HCO3-/H2CO3) is the primary chemical buffer in blood plasma, rapidly neutralizing excess acids or bases to keep pH within the narrow 7.35-7.45 range. The phosphate and protein (including hemoglobin) buffer systems also contribute, but bicarbonate is the most abundant and works together with the lungs and kidneys for longer-term regulation.
The process of 'diapedesis' refers to the ability of WBCs to:
- A Squeeze through the walls of capillaries to enter the surrounding tissues
- B Engulf and destroy invading bacteria through the process of phagocytosis
- C Produce and release antibodies that target specific foreign antigens
- D Undergo rapid mitotic division to increase their total cell numbers
Correct answer: Squeeze through the walls of capillaries to enter the surrounding tissues
Diapedesis (or emigration) is the process by which leukocytes become thin and elongated to slip between the endothelial cells of capillary walls, allowing them to migrate into the surrounding tissue at a site of infection or injury.