Anatomy and Physiology / Unit 8: The Cardiovascular and Lymphatic Systems
8.1 Blood Composition
Notes
Blood is a connective tissue with a liquid matrix. Total volume is about 5 L in an adult. Functions: transport, regulation (pH, temperature, fluid balance) and protection (clotting, immunity).
- Plasma (about 55%): mostly water plus proteins (albumin keeps osmotic pressure, globulins include antibodies, fibrinogen clots), nutrients, hormones, wastes and ions.
- Formed elements (about 45%): erythrocytes (red blood cells), leukocytes (white blood cells) and platelets.
- Hematocrit is the percent of blood volume that is red blood cells (about 42% in women and 47% in men).
- All formed elements arise from stem cells in red bone marrow (hematopoiesis).
- Example: a person with a hematocrit of 30% likely has anemia.
Practice
Which plasma protein is involved in blood clotting?
Fibrinogen is converted to fibrin threads that form the clot.
A blood sample is spun in a centrifuge. The packed cells at the bottom make up 45% of the volume. This value is called the:
Hematocrit is the percent of blood volume occupied by red blood cells.
Where are blood cells produced in an adult?
Hematopoiesis occurs in red marrow.
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