Components,
Characteristics, Functions of Blood
Major
Components of Blood
1. Formed
elements - the actual cellular components of blood (special connective tissue)
a.erythrocytes - red blood cells
b.leukocytes - white blood cells
c.platelets - cell fragments for clotting
2. Blood plasma - complex non-cellular fluid
surrounding formed elements; protein & electrolytes.
Separation
of Components in a Centrifuge
VOLUME LAYER
clear/yellowish PLASMA 55% top
thin/whitish buffy coat <1%
middle
with
LEUKOCYTES & PLATELETS
reddish mass - ERYTHROCYTES 45% bottom
hematocrit - percentage by
VOLUME of erythrocytes when blood is centrifuged (normal = 45%)
Characteristics
of Blood
1. bright
red (oxygenated)
2. dark
red/purplish (unoxygenated)
3. much
more dense than pure water
4. pH range
from 7.35 to 7.45 (slightly alkaline)
5. slightly
warmer than body temperature 100.4 F
6. typical
volume in adult male 5-6 liters
7. typical
volume in adult female 4-5 liters
8. typically
8% of body weight
Major
Functions of Blood
1. Distribution
& Transport
a. oxygen
from lungs to body cells
b. carbon
dioxide from body cells to lungs
c. nutrients
from GI tract to body cells
d. nitrogenous
wastes from body cells to kidneys
e. hormones
from glands to body cells
2. Regulation (maintenance of homeostasis)
a. maintenance
of normal body pH by blood proteins (albumin) & bicarbonate
b. maintenance
of circulatory/interstitial fluid by electrolytes that aid blood proteins (albumin)
c. maintenance
of temperature (blushed skin)
3. Protection
a. platelets
and proteins "seal" vessel damage
b.
protection from foreign material & infections byleukocytes,
antibodies& complement proteins
Plasma (the liquid part of
blood)
A. General Characteristics
1. plasma
makes up 55% of normal blood by volume
2. water is
90% of the plasma by volume
3. many
different SOLUTES in the plasma
a. albumin
- pH buffer & osmotic pressure
b. globulins
- binding proteins & antibodies
c. clotting
proteins - prothrombin & fibrinogen
d. other
proteins - enzymes, hormones, others
e. nutrients
- glucose, fatty acids, amino acids, cholesterol, vitamins
f. electrolytes - Na+, K+, Ca++,
Mg++, Cl-, phosphate, sulfate, bicarbonate, others
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. In children, blood cells are actively produced in the marrow cavities of all the bones. By age 20, the marrow in the cavities of the long bones, except for the upper humerus and femur, has become inactive . Active cellular marrow is called red marrow; inactive marrow that is infiltrated with fat is called yellow marrow.
ERYTHROCYTE life span:
hemocytoblast ->
reticulocyte 3-5
DAYS
reticulocyte ->
ERYTHROCYTE 2
DAYS (in blood)
ERYTHROCYTE lifespan 100-120
DAYS
(primarily destroyed by
macrophages in the spleen)
The
red, oxygen-carrying pigment in the red blood cells of vertebrates is
hemoglobin, a protein with a molecular weight of 64,450. Hemoglobin is a
globular molecule made up of 4 subunits .Each subunit contains a heme moiety
conjugated to a polypeptide. Heme is an iron-containing porphyrin derivative .
The polypeptides are referred to collectively as the globin portion of the hemoglobin
molecule.
There
are two pairs of polypeptides in each hemoglobin molecule.
1.
(hemoglobin A is α2 β2
) the normal adult human hemoglobin ; the two types of polypeptide are called the α
chains, each of which contains 141 amino acid residues, and the β
chains, each of which contains 146 amino acid residues. Thus, hemoglobin A
is designated α2β2.
2. hemoglobin A2
(α2δ2). this forms about 2.5% of the hemoglobin, in
which β chains are replaced by δ chains (α2δ2). The δ
chains also contain 146 amino acid residues, but 10 individual residues differ
from those in the β chains.
3.There are small amounts of hemoglobin A derivatives closely associated with hemoglobin A that represent glycated hemoglobins. One of these, hemoglobin A1c (HbA1c), has a glucose attached to the terminal valine in each β chain and is of special interest because the quantity in the blood increases in poorly controlled diabetes mellitus .
3.There are small amounts of hemoglobin A derivatives closely associated with hemoglobin A that represent glycated hemoglobins. One of these, hemoglobin A1c (HbA1c), has a glucose attached to the terminal valine in each β chain and is of special interest because the quantity in the blood increases in poorly controlled diabetes mellitus .
4.Hemoglobin
in the Fetus
1.The blood of the human fetus normally contains fetal hemoglobin (hemoglobin F hemoglobin F is( α2 γ2). The γ chains also contain 146 amino acid residues but have 37 that differ from those in the β chain. Fetal hemoglobin is normally replaced by adult hemoglobin soon after birth. In certain individuals, it fails to disappear and persists throughout life. In the body, its O2 content at a given PO2 is greater than that of adult hemoglobin because it binds 2,3-DPG less avidly. This facilitates movement of O2 from the maternal to the fetal circulation
1.The blood of the human fetus normally contains fetal hemoglobin (hemoglobin F hemoglobin F is( α2 γ2). The γ chains also contain 146 amino acid residues but have 37 that differ from those in the β chain. Fetal hemoglobin is normally replaced by adult hemoglobin soon after birth. In certain individuals, it fails to disappear and persists throughout life. In the body, its O2 content at a given PO2 is greater than that of adult hemoglobin because it binds 2,3-DPG less avidly. This facilitates movement of O2 from the maternal to the fetal circulation
2. In
young embryos there are, in addition, ζ and ε chains, forming Gower 1
hemoglobin (ζ2ε2) and Gower 2 hemoglobin (α2ε2).
Reactions
of Hemoglobin
1.oxygenation:Hemoglobin binds O2 to form oxyhemoglobin, O2 attaching to the Fe2+ in the heme. The affinity of hemoglobin for O2 is affected by pH, temperature, and the concentration in the red cells of 2,3-diphosphoglycerate (2,3-DPG). 2,3-DPG and H+ compete with O2 for binding to deoxygenated hemoglobin, decreasing the affinity of hemoglobin for O2 by shifting the positions of the four peptide chains (quaternary structure).
2.oxidation: When blood is exposed to various drugs and other oxidizing agents in vitro or in vivo, the ferrous iron (Fe2+) that is normally in the molecule is converted to ferric iron (Fe3+), forming methemoglobin. Methemoglobin is dark-colored, and when it is present in large quantities in the circulation, it causes a dusky discoloration of the skin resembling cyanosis . Some oxidation of hemoglobin to methemoglobin occurs normally, but an enzyme system in the red cells, the NADH-methemoglobin reductase system, converts methemoglobin back to hemoglobin. Congenital absence of this system is one cause of hereditary methemoglobinemia.
3. Carbon monoxide reacts with hemoglobin to form carbon monoxyhemoglobin (carboxyhemoglobin). The affinity of hemoglobin for O2 is much lower than its affinity for carbon monoxide, which consequently displaces O2 on hemoglobin, reducing the oxygen- carrying capacity of blood .
4. Heme is also part of the structure of myoglobin, an oxygen-binding pigment found in red (slow) muscles
1.oxygenation:Hemoglobin binds O2 to form oxyhemoglobin, O2 attaching to the Fe2+ in the heme. The affinity of hemoglobin for O2 is affected by pH, temperature, and the concentration in the red cells of 2,3-diphosphoglycerate (2,3-DPG). 2,3-DPG and H+ compete with O2 for binding to deoxygenated hemoglobin, decreasing the affinity of hemoglobin for O2 by shifting the positions of the four peptide chains (quaternary structure).
2.oxidation: When blood is exposed to various drugs and other oxidizing agents in vitro or in vivo, the ferrous iron (Fe2+) that is normally in the molecule is converted to ferric iron (Fe3+), forming methemoglobin. Methemoglobin is dark-colored, and when it is present in large quantities in the circulation, it causes a dusky discoloration of the skin resembling cyanosis . Some oxidation of hemoglobin to methemoglobin occurs normally, but an enzyme system in the red cells, the NADH-methemoglobin reductase system, converts methemoglobin back to hemoglobin. Congenital absence of this system is one cause of hereditary methemoglobinemia.
3. Carbon monoxide reacts with hemoglobin to form carbon monoxyhemoglobin (carboxyhemoglobin). The affinity of hemoglobin for O2 is much lower than its affinity for carbon monoxide, which consequently displaces O2 on hemoglobin, reducing the oxygen- carrying capacity of blood .
4. Heme is also part of the structure of myoglobin, an oxygen-binding pigment found in red (slow) muscles
5.In
addition, neuroglobin, an oxygen-binding globin, is found in the brain. It
appears to help supply O2 to neurons. There is heme in the
respiratory chain enzyme cytochrome c .
The average normal hemoglobin content of blood is 16 g/dL in men and 14 g/dL in women, all of it in red cells. In the body of a 70-kg man, there are about 900 g of hemoglobin, and 0.3 g of hemoglobin is destroyed and 0.3 g synthesized every hour . The heme portion of the hemoglobin molecule is synthesized from glycine and succinyl-CoA.
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