Blood physiology

Dr.baybeen Alselevany /PhD)

Dept. Of Medical Physiology
College of Medicine
University of Mosul
2017-2018

References

1. 4.Text Book of Medical Physiology. Guyton and Hall. 11ed.
2.Review of Medical Physiology.Willam F.Ganong.
3.Essentials of Phsiology.Nicholas sperelakis ,Robert
O.Banks.
4.Human Physiology .Vander ,Sherman,Luciano.
5.internet

BLOOD PHYSIOLOGY

Lec. 1 9 October 2017
Prof .Dr baybeen Alselevany


Objectives
1.definitions
2.compostion of blood
3.functions of blood
4.plasma
5.serum
6.lymph

Hematology: defined as the scientific study of the structure and functions of blood in health & disease. i.e. study the normal and abnormal morphology and physiology of blood.



Blood: - has been defined as a highly specialized tissue, which along with the circulatory system is adapted to meet the needs of the body tissues and organ systems. Such as exchange of gases, provision of nutrients, and removal of waste products.
Cells required constant nutrition and waste removal because they are metabolically active. Most cells are located some distance from nutrient sources such as the digestive tract & sites of waste disposal such as kidneys. The cardiovascular system(which consists of the heart, blood vessels and blood) connects the various tissues. The heart pumps blood through blood vessels, which extend throughout the body, and the blood delivers nutrient and picks up waste products.


General Functions of blood
1.Transportation: blood is the primary transport medium of the body.
a. O2 enters the blood from the lungs and is carried to cells, and
CO2 produced by cells is carried from the blood to the lungs
from which it is expelled.
b.The blood from the gastrointestinal tract to cells transports
ingested nutrients, electrolytes & water, and waste products are
transported from cells to kidneys for elimination in urine. 2.Maintenance: blood plays a crucial role in maintaining
homeostasis(constancy of internal environment).
a.. many of the hormones and enzymes that regulate
body processes , are found in blood which act as buffers
which help keep the blood’s PH within its normal limits
of 7.35 – 7.45.
b.The osmotic composition of blood is also critical for
maintaining the normal fluid & electrolyte balance.
c.Temeprature regulation :because blood can hold heat, it
is involved with temperature regulation transporting heat
from the interior to the surface of the body, where the
heat is released.
3) Protection: cells and chemicals of the blood constitute an important in immune system, protecting against foreign substances such as microorganisms and toxins. Blood clotting also provides protection against excessive fluid & cell loss when blood vessels are damaged.


Composition of Blood
The normal total circulating blood volume is 8% of the body weight of a 70kg man (i.e. 5600ml). Blood is a type of connective tissue, consisting of:
Plasma: the fluid portion of blood.
Blood cells: the solid portion of blood.
Specialized cells (erythrocytes and Leukocytes).
Cell fragments (platelets or thrombocytes).

PLASMA

The normal plasma volume is 55% of total blood volume(TBV) i.e 3080. Plasma remaining fluid only if an anticoagulant is added to the blood.
Composition of Plasma
Plasma: is a pale yellow fluid that consists of:
91% water: which acts as a solvent and suspending medium for
blood component
2.2% other solutes such as ions (involved in osmosis, membrane potential and acid-base balance), nutrients (as a source of energy), vitamins (promote enzyme activity), gases (such as O2 necessary for aerobic respiration, and CO2 waste product of aerobic respiration), regulatory substances (such as hormones), and waste products (such as urea, uric acid, etc which are excreted by the kidneys.
3. (7%) plasma proteins: Plasma is a colloidal solution, which is a liquid containing suspended substance that does not settle out of solution. Most of the suspended substances are plasma proteins, which include albumin, globulins, and fibrinogen.

Separation of proteins in a plasma sample is performed by a technique called electrophoresis.
Origin of plasma proteins:
Most of the plasma proteins are synthesized in the liver except circulating antibodies or immunoglobulin's (Ig's) which are manufactured in the plasma cells (from B-lymphocytes).


Functions of plasma proteins
Five major functions of plasma proteins.
Coagulation: fibrinogen is responsible for blood clots. If there is congenital absence of fibrinogen (afibrogenemia) the result will be defect in clotting mechanism. There are plasma proteins known as fibrinolytic factors such as plasminogen, which prevent formation of spontaneous clots in the blood vessels.
2. Transport: many plasma proteins acts as carriers for many simple and complex compounds involved in nutrition & hormonal integration. Albumin & globulins acts as carrier proteins.
3. Inflammation: Plasma also contains a number of proteins that play a major role in the production of inflammatory responses resulting from infection, allergy, or autoimmune disease. e.g. β- globulins. Many of these proteins are present in an inactive form that can be activated by chemical stimuli.
2. Immunity:Immunoglobulin's (Ig's) or antibodies: Formed by β – lymphocytes & play a major role in the body’s defense against invading pathogens. Ig's are found mainly in the γ - globulin fraction of plasma. Ig's are:, IgA, IgD, IgE, IgG , and IgM.
5-Transvascular exchange of water: This is mainly the function of albumins. The osmotic (oncotic) pressure of albumins maintains the delicate balance between the two fluid compartments. About 60% of capillary oncotic pressure is due to plasma protein albumin, which is about 25 mmHg at arterial and venous ends of capillary and tends to cause osmosis of fluid inward through the capillary. Filtration is occurred at arterial end of capillary because capillary hydrostatic pressure, which is about 40 mmHg, exceeds the oncotic pressure, while at the venous end, reabsorption of water occurs because oncotic pressure exceeds capillary hydrostatic pressure, which is about 12 mmHg.



If there is abnormal imbalance of forces at capillary wall, odema result. Odema (Dropsy) : Is the failure of reabsorption of tissue fluids ( i.e. the filtration rate is exceed the reabsorption rate). Causes of odema:
Hypoproteinemia: plasma protein levels are low such as in liver disease, nephritis (kidney disease), particularly the nephrotic syndrome there is a large loss of protein in the urine (albuminuria).
a.high venous pressure: e.g. congestive heart failure.
b.a venous thrombosis: e.g. a very high bandage, or a plaster cast which is obstructing the veins, pregnant women may have swollen legs as a result of pressure by the baby in utero on the veins returning blood from the legs.
c.Increased capillary permeability: e.g. insect bit.

Serum

If whole blood is allowed to clot and the clot is removed, the remaining fluid is called serum. Serum has essentially the same composition as plasma except that 1- its clotting factors: fibrinogen (factor I), prothrombin (factor II), labile factor (factor V), and antihemophilic factor VIII have been removed and 2- it has a higher serotonin content because of the breakdown of platelets during clotting mechanism. So serum may be defined as plasma minus clotting factors (I, II, V, and VIII)
LYMPH
Lymph is tissue fluid that enters the venous blood through lymphatic circulation.
Composition:
It contains clotting factors and clot on standing in vitro.
It contains proteins that traverse capillary walls and return to blood via the lymph. The concentration of protein in the lymph is lower than that of plasma. Lymph protein content varies with the region from which the lymph drains as shown in the table:


Table : protein content of lymph in humans.
Source of lymph
Protein content (g / dL)
Liver
6.2
Heart
4.4
Gastrointestinal Tract
4.1
Lung
4
Skeletal muscle
2
Skin
2
Ciliary body
0
Choroid plexus
0