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Questions and Answers

What is the specific gravity of blood?

1.095

1.075

1.055 (correct)

1.035

What is the pH of blood?

7.2

7.8

7.4 (correct)

7.6

What percentage of blood volume is made up of plasma?

45%

55% (correct)

50%

60%

Where are red blood cells, many white blood cells, and platelets formed in adults?

Bone marrow Signup and view all the answers

What is the term for active cellular marrow?

Red marrow Signup and view all the answers

At what age does the marrow in the cavities of the long bones, except for the upper humerus and femur, become inactive?

20 Signup and view all the answers

What is the viscosity of blood compared to water?

Why does blood appear scarlet red when taken from arteries and purplish from veins?

Due to its O2 content Signup and view all the answers

What do platelets lack?

Nuclei Signup and view all the answers

What is the average lifespan of platelets in the circulation?

4 days Signup and view all the answers

What is the function of red blood cells?

To carry oxygen Signup and view all the answers

What is the average normal red blood cell count in men?

5.4 million/μL Signup and view all the answers

What is the purpose of lymphocytes?

To fight infections Signup and view all the answers

What happens to the number of platelets after a splenectomy?

It increases Signup and view all the answers

What is the shape of red blood cells?

Biconcave disks Signup and view all the answers

Where are red blood cells manufactured?

Bone marrow Signup and view all the answers

What percentage of Rh-negative individuals are sensitized by transfusion of Rh-positive blood?

50% Signup and view all the answers

What is the primary reason the first child of an Rh-negative mother is usually normal?

Sensitization occurs at birth Signup and view all the answers

What is the purpose of administering Rh immune globulin during the postpartum period?

To prevent active antibody formation by the mother Signup and view all the answers

What is the result of routine administration of Rh immune globulin in obstetric clinics?

Reduced incidence of hemolytic disease by more than 90% Signup and view all the answers

What percentage of plasma is composed of water?

92% Signup and view all the answers

What is the primary function of anticoagulants in plasma?

To prevent clotting Signup and view all the answers

What is the term for the fluid that remains after whole blood has clotted and the clot is removed?

Serum Signup and view all the answers

Approximately what percentage of body weight is composed of plasma volume in a normal adult?

5% Signup and view all the answers

What is the approximate size of the bone marrow in the body?

Similar to the size and weight of the liver Signup and view all the answers

What percentage of cells in the bone marrow belong to the white blood cell–producing myeloid series?

75% Signup and view all the answers

What is the primary function of hematopoietic stem cells (HSCs)?

To produce all types of blood cells Signup and view all the answers

What is the average life span of white cells in the body?

Shorter than that of red cells Signup and view all the answers

Which of the following cells are not produced from hematopoietic stem cells?

Muscle cells Signup and view all the answers

What is the normal range of white blood cells per microliter in human blood?

4,000–11,000 Signup and view all the answers

What is the result of injecting hematopoietic stem cells into a patient whose bone marrow has been destroyed?

The patient's bone marrow is completely replaced Signup and view all the answers

Which of the following types of blood cells has a separate pool of progenitor cells?

All types of blood cells except neutrophils and monocytes Signup and view all the answers

What is the main difference in protein content between lymph and plasma?

Plasma has higher protein content Signup and view all the answers

What is the reason for the milky appearance of lymph in the thoracic duct after a meal?

High fat content Signup and view all the answers

What is the main function of endothelial cells in blood vessels?

To respond to flow changes and secret growth regulators Signup and view all the answers

What type of channels are found in the membranes of vascular smooth muscle cells?

K+, Ca2+, and Cl− channels Signup and view all the answers

What is the primary mechanism of contraction in vascular smooth muscle?

Myosin light chain mechanism Signup and view all the answers

What is the role of influx of Ca2+ via voltage-gated Ca2+ channels in vascular smooth muscle?

It initiates contraction Signup and view all the answers

What is the term for the prolonged contractions that determine vascular tone in vascular smooth muscle?

Latch bridge mechanism Signup and view all the answers

Where do lymphocytes enter the circulation?

Through the lymphatics Signup and view all the answers

Study Notes

Overview of Blood

Blood is a specialized type of connective tissue that is red in color, has a specific gravity of 1.055, and a viscosity 2.5 times that of water.
It is alkaline with a pH of 7.4 and appears scarlet red when taken from arteries and purplish from veins due to its oxygen content.

Blood Composition

Blood consists of a protein-rich fluid called plasma, in which are suspended cellular elements: white blood cells, red blood cells, and platelets.
The normal total circulating blood volume is about 8% of the body weight (5600 mL in a 70-kg man).
About 55% of this volume is plasma.

Blood Functions

Blood plays a role in maintaining the cellular environment by serving as a transport medium of the body.
The various functions of blood result from specialization within the cellular elements or the plasma or the interaction between the two.

Bone Marrow

In the adult, red blood cells, many white blood cells, and platelets are formed in the bone marrow.
In the fetus, blood cells are also formed in the liver and spleen, and in adults, such extramedullary hematopoiesis may occur in diseases in which the bone marrow becomes destroyed or fibrosed.
By age 20, the marrow in the cavities of the long bones, except for the upper humerus and femur, has become inactive.

Cellular Elements

Hematopoietic stem cells (HSCs) are bone marrow cells that are capable of producing all types of blood cells.
They differentiate into one or another type of committed stem cells (progenitor cells).
These in turn form the various differentiated types of blood cells.

White Blood Cells

Normally, human blood contains 4000–11,000 white blood cells per microliter.
Most of them contain neutrophilic granules (neutrophils), but a few contain granules that stain with acidic dyes (eosinophils), and some have basophilic granules (basophils).
Lymphocytes, which have large round nuclei and scanty cytoplasm, and monocytes, which have abundant agranular cytoplasm and kidney-shaped nuclei, are also present.

Platelets

Platelets are small, granulated bodies that aggregate at sites of vascular injury.
They lack nuclei and are 2–4 μm in diameter.
There are about 300,000/μL of circulating blood, and they normally have a half-life of about 4 days.

Red Blood Cells

The red blood cells (erythrocytes) carry hemoglobin in the circulation.
They are biconcave disks that are manufactured in the bone marrow.
In mammals, they lose their nuclei before entering the circulation.
The average normal red blood cell count is 5.4 million/μL in men and 4.8 million/μL in women.

Plasma

The fluid portion of the blood contains 92% water and 8% solid.
Plasma is a remarkable solution containing an immense number of ions, inorganic molecules, and organic molecules that are in transit to various parts of the body or aid in the transport of other substances.
Normal plasma volume is about 5% of body weight, or roughly 3500 mL in a 70-kg man.

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