Blood is a connective tissue that carries nutrients, waste, and heat through blood vessels. It is composed of plasma and formed elements. Plasma is 90% water and contains dissolved substances like nutrients, salts, gases, hormones, and waste. Formed elements include red blood cells that carry oxygen, white blood cells that fight infection, and platelets that help clotting. Blood has key functions like distribution of oxygen and nutrients, regulation of substances, and protection from infection and blood loss.

2. Blood-the “River of Life”
Blood is the only fluid tissue in the human body. Blood
is classified as a connective tissue. Blood carries
nutrients, waste, and body heat through blood
vessels.
• Components of blood
– Living cells
• Formed elements
– Non-living matrix
• Plasma

3. Blood Composition
If blood is centrifuged
– Erythrocytes sink to the bottom (45%
of blood, a percentage known as the
hematocrit)
– Buffy coat contains leukocytes and
platelets (less than 1% of blood)
• Buffy coat is a thin, whitish layer
between the erythrocytes and
plasma
– Plasma rises to the top (55% of blood)
The formed elements (blood cells) make blood
heavier and 5 times thicker (more viscous)
than water.

4. Figure 10.1 (2 of 2)
Blood

5. Physical Characteristics of Blood
• Color range
– Oxygen-rich blood is scarlet
red
– Oxygen-poor blood is dull
red
• pH must remain between 7.35–
7.45
Acidosis (pH7. 2) Death (pH 7)

6. Physical Characteristics of Blood
• Blood temperature is slightly higher than body
temperature at 100.4°F
• In a healthy man, blood volume is about 5–6
liters or about 6 quarts
• Blood makes up 8% of body weight

7. Functions of Blood
• Functions include (More details on next 3
slides)
– Distributing substances
– Regulating blood levels of substances
– Protection

8. Distribution Functions
• Delivering O2 and nutrients to body cells
• Transporting metabolic wastes to lungs
and kidneys for elimination
• Transporting hormones from endocrine
organs to target organs

9. Regulation Functions
• Maintaining body temperature by
absorbing and distributing heat
• Maintaining normal pH using buffers;
alkaline reserve of bicarbonate ions
• Maintaining adequate fluid volume in
circulatory system

10. Protection Functions
• Preventing blood loss
– Plasma proteins and platelets initiate clot
formation
• Preventing infection
– Antibodies
– Complement proteins
– WBCs

11. Blood Plasma
Composition
• Composed of
approximately 90%
water
• Includes many
dissolved substances
– Nutrients
– Salts (electrolytes)
– Respiratory gases
– Hormones
– Plasma proteins
– Waste products

12. Blood Plasma
• Plasma proteins
– Most abundant solutes in
plasma
– Most plasma proteins are
made by liver
– Various plasma proteins
include
• Albumin—regulates
osmotic pressure
• Fibrinogen: Clotting
proteins—help to stem
blood loss when a blood
vessel is injured
• Globulins: Antibodies—
help protect the body
from pathogens

13. Blood Plasma:
Homeostatic imbalances
• Acidosis
– Blood becomes too
acidic
• Alkalosis
– Blood becomes too
basic
• In each scenario,
the respiratory
system and kidneys
help restore blood
pH to normal

14. Formed Elements
• Erythrocytes
– Red blood cells (RBCs)
• Leukocytes
– White blood cells (WBCs)
• Platelets
• Cell fragments