549
CHAPTER FOURTEEN
Blood
(1) Glucose is stored in the liver as glycogen
and is released whenever the blood glucose
concentration falls.
(2) Amino acids are used to synthesize proteins
and are deaminated for use as energy sources.
(3) Lipoproteins function in the transport of lipids.
3. Nonprotein nitrogenous substances
a. Nonprotein nitrogenous substances are composed
of molecules that contain nitrogen atoms but are
not proteins.
b. They include amino acids, urea, uric acid, creatine,
and creatinine.
(1) Urea and uric acid are products of catabolism.
(2) Creatinine results from the metabolism of
creatine.
c. Levels of these substances usually remain stable;
an increase may indicate a kidney disorder.
4. Plasma electrolytes
a. Plasma electrolytes are absorbed from the
intestines and are released as by-products of
cellular metabolism.
b. They include ions of sodium, potassium, calcium,
magnesium, chloride, bicarbonate, phosphate, and
sulfate.
c. They are important in the maintenance of osmotic
pressure and pH.
14.4
HEMOSTASIS (PAGE 538)
Hemostasis refers to the stoppage of bleeding. Hemostatic
mechanisms are most effective in controlling blood loss
from small vessels.
1. Blood vessel spasm (vasospasm)
a. Smooth muscles in the walls of smaller blood
vessels refl
exly contract following injury.
b. Platelets release serotonin that stimulates
vasoconstriction and helps maintain blood vessel
spasm.
2. Platelet plug formation
a. Platelets adhere to rough surfaces and exposed
collagen.
b. Platelets adhere together at the sites of injuries and
form platelet plugs in broken vessels.
3. Blood coagulation
a. Blood clotting, the most effective means of
hemostasis, is a series of reactions wherein each
reaction stimulates the next (cascade), which may
be initiated by extrinsic or intrinsic mechanisms.
b. The extrinsic clotting mechanism is triggered when
blood contacts damaged tissue.
c. The intrinsic clotting mechanism is triggered when
blood contacts a foreign surface.
d. Clot formation refl
ects balance between clotting
factors that promote or inhibit clotting.
e. The major event of coagulation is the conversion
of soluble F
brinogen into insoluble F
brin.
f. A formed clot retracts and pulls the edges of a
broken blood vessel closer together.
g. A thrombus is an abnormal blood clot in a blood
vessel; an embolus is a clot or fragment of a clot
that moves in a blood vessel.
5. Dietary factors affecting red blood cell production
a. The availability of vitamin B
12
, iron, and folic acid
affects red blood cell production.
b. The rate of iron absorption varies with the amount
of iron in the body.
6. Destruction of red blood cells
a. Red blood cells are fragile and are damaged while
moving through capillaries.
b. Macrophages in the spleen and liver phagocytize
damaged red blood cells.
c. Hemoglobin molecules are decomposed, and the
iron from the heme portion is recycled.
d. Biliverdin and bilirubin are pigments, released
from the heme portion, excreted in bile.
e. The globin portion is broken down into amino
acids metabolized by macrophages or released into
the blood.
7. Types of white blood cells
a. Granulocytes include neutrophils, eosinophils, and
basophils.
b. Agranulocytes include monocytes and
lymphocytes.
8. ±unctions of white blood cells
a. Neutrophils and monocytes phagocytize foreign
particles.
b. Chemicals released by damaged cells attract and
stimulate leukocytes.
9. White blood cell counts
a. Normal total white blood cell counts vary from
4,500 to 10,000 cells per microliter of blood.
b. The number of white blood cells may change in
abnormal conditions such as infections, emotional
disturbances, or excessive loss of body fl
uids.
c. A differential white blood cell count indicates the
percentages of various types of leukocytes.
10. Blood platelets
a. Blood platelets are fragments of megakaryocytes
that enter the circulation.
b. The normal count varies from 130,000 to 360,000
platelets per microliter.
c. Platelets help close breaks in blood vessels.
14.3
BLOOD PLASMA (PAGE 535)
Plasma is the liquid part of the blood that is composed of
water and a mixture of organic and inorganic substances.
It transports nutrients and gases, helps regulate fl
uid and
electrolyte balance, and helps maintain stable pH.
1. Plasma proteins
a. Plasma proteins remain in the blood and interstitial
uids and are not normally used as energy sources.
b. Three major types exist.
(1) Albumins help maintain the osmotic pressure
of plasma.
(2) Globulins provide immunity (antibodies) and
transport lipids and fat-soluble vitamins.
(3) ±ibrinogen functions in blood clotting.
2. Gases and nutrients
a. Gases in plasma include oxygen, carbon dioxide,
and nitrogen.
b. Plasma nutrients include simple sugars, amino
acids, and lipids.
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