BLOOD AND BLOOD VESSELS - ENGLSH
Nursing Notesclick here to subscribe My Student Support System
BLOOD AND BLOOD VESSELS-
• The
circulatory system includes the organs which are involved in circulation . It
is also known as cardio-vascular system . In
this system we will study about -
• Blood
and blood vessels.
• Heart
BLOOD-
• Blood
is a connective tissue. It circulates continually in the body, allowing
constant communication between tissues distant from each other. Men have 5–6 L
and women 4–5 L. Blood is thicker, denser and flows much slower than water
Blood has two components:
• (1)
blood plasma, a watery liquid extracellular matrix that contains
dissolved substances, and
• (2)
formed elements, which are cells and cell fragments.
•
PLASMA-
• Blood
plasma is a pale yellow‐coloured fluid and its total volume in an adult is
approximately 2.5–3 L. Plasma constitutes approximately 55% of blood’s
volume. Blood plasma is about 91.5%
water and 8.5% solutes, most of which
are proteins.
• Blood
plasma includes-
• -Plasma
proteins -Electrolytes
• -Nutrients,
principally from digested foods
• -Waste
materials -Hormones
• -Gases.
• Plasma
proteins, which make up about 7% of plasma, are normally retained within the
blood, because they are too big to escape through the capillary pores into the
tissues. They are largely responsible for creating the osmotic pressure of
blood which keeps plasma fluid within
the circulation. Plasma proteins are- Albumin • Globulin • Prothrombin •
Fibrinogen
• Electrolytes
are very important for our body. These have a range of functions, including
muscle contraction , transmission of nerve impulses and maintenance of acid–base balance. These
includes- • Sodium • Potassium • Calcium • Bicarbonate • Phosphate • Chloride
• The
products of digestion, e.g. glucose, amino acids, fatty acids and glycerol,
vitamins and minerals are absorbed from the alimentary tract. Together with
mineral salts and vitamins they are used by body cells for energy, heat, repair
and replacement, and for the synthesis of other blood components and body
secretions.
• Urea,
creatinine, bilirubin , ammonia and uric
acid are the waste products of protein
metabolism. They are formed in the liver and carried in blood to the kidneys
for excretion.
• These
are chemical messengers synthesised by endocrine glands. Hormones pass directly
from the endocrine cells into the blood, which transports them to their target
tissues and organs elsewhere in the body, where they influence cellular
activity.
• Oxygen,
carbon dioxide and nitrogen are transported round the body dissolved in plasma.
Oxygen and carbon dioxide are also transported in combination with haemoglobin
in red blood cells. Most oxygen is carried in combination with haemoglobin and
most carbon dioxide as bicarbonate ions dissolved in plasma
• The
formed elements of the blood include three principal components:
• Red
blood cells (RBCs),
• White
blood cells (WBCs),
• Platelets.
• Red
blood cells (also known as erythrocytes) are the most abundant blood cells.
They are biconcave discs and contain
oxygen‐carrying protein called haemoglobin. The biconcave shape is maintained
by a network of proteins called spectrin. Their characteristic shape is suited
to their purpose; the biconcavity increases their surface area for gas
exchange,
• Haemoglobin
is composed of a protein called globin bound to the iron‐containing pigments
called haem. Erythrocytes are produced in red bone marrow, which is present in
the ends of long bones and in flat and irregular bones. They pass through
several stages of development before entering the blood. Their life span in the
circulation is about 120 days.
• White
blood cells are also known as leucocytes. There are approximately 5000–10,000
white blood cells in every cubic millimetre of blood. There are two main types
of white blood cells:
• Granulocytes
(contain granules in the cytoplasm)
• ⚬
Neutrophils ⚬ Eosinophils ⚬
Basophils;
• Agranulocytes (despite the name contain a few
granules in the cytoplasm)
• ⚬
Monocytes ⚬
Lymphocytes.
• Neutrophils-
These small, fast and active cells protect the body against bacterial invasion,
and remove dead cells and debris from damaged tissues by phagocytosis. They are
attracted in large numbers to any area of infection by chemical substances
called chemotaxins, which are released by damaged cells. Neutrophils are
highly mobile, and squeeze through the capillary walls in the affected area
• Eosinophil-These
form approximately 2–4% of granulocytes and have B‐shaped nucleus . Like
neutrophils, they too migrate from blood vessels and they are 10–12 μm in
diameter. They also have phagocytic activity. They contain lysosomal enzymes
and peroxidase in their granules, which are toxic to parasites, resulting in
the destruction of the organism.
• Basophils,
which are closely associated with allergic reactions, contain cytoplasmic
granules packed with heparin ,histamine and other substances that
promote inflammatory reactions. Basophils play an important role in providing
immunity against parasites and also in the allergic response, as they have
immunoglobulin E (IgE) on their surface.
• Monocyte-
These are the largest of the white blood cells. Some circulate in the blood and
are actively motile and phagocytic while others migrate into the tissues where
they develop into macrophages. Macrophages play a vital role in immunity
and inflammation by destroying specific antigens.
• Lymphocytes
are smaller than monocytes and have large nucleus. They circulate in the blood
and are present in great numbers in lymphatic tissue such as lymph nodes and
the spleen. Although all lymphocytes originate from one type of stem cell, when
they are activated in lymphatic tissue, two distinct types of lymphocyte are
produced – T-lymphocytes and B-lymphocytes
•
FUNCTIONS OF BLOOD
• Transportation:
The blood is the means whereby all nourishment (protein, carbohydrate,
fats, minerals, vitamins) hormones and respiratory gases (oxygen and carbon-dioxide
are transported into and out of the cells.
• Maintaining
body temperature: Blood helps to maintain the body temperature by
distributing the heat produced by the chemical activity of the cells evenly,
throughout the body.
• Maintaining
the acid–base balance: Blood pH is maintained by the excretion or
reabsorption of hydrogen ions and bicarbonate ions.
•
Regulation of fluid balance: When the blood reaches the kidneys, excess
fluid is excreted or reabsorbed to maintain fluid balance.
•
Removal of waste products: The blood removes all waste products from the
tissues and cells. These waste products are transported to the appropriate
organs for excretion – lungs, kidneys, intestine, skin and so on.
• Blood
clotting: By the mechanism of clotting, loss of blood cells and body fluids
is prevented.
• Defence
action: The blood aids in the defence of the body against the invasion of
microorganisms and their toxins due to the phagocyte action of neutrophils and
monocytes.
BLOOD GROUPING
• Individuals
have different types of antigen on the surfaces of their red blood cells. These
antigens, which are inherited, determine the individual’s blood group.
In addition, individuals make antibodies to these antigens, but not to their
own type of antigen. These antibodies circulate in the bloodstream and the
ability to make them, like the antigens, is genetically determined and not
associated with acquired immunity.
• ABO
system- In this system blood group is decided based on presence of antigen agglutinogens
on the RBC. People whose RBCs display only antigen A have type A blood.
Those who have only antigen B are type B. Individuals who have both
A and B antigens are type AB; those who have neither antigen A
nor B are type O.
• Blood
plasma usually contains antibodies called agglutinins that react
with the A or B antigens if the two are mixed. These are the anti-A
antibody, which reacts with antigen A, and the anti-B antibody, which
reacts with antigen B. Blood group A individuals make anti-B antibody , blood
group B individuals, make anti-A
antibody. Blood group AB make neither anti-A antibody nor anti-B
antibody, and blood group O make both anti-A and anti-B antibodies.
• RH
system- The Rh blood group is so named because the antigen was
discovered in the blood of the Rhesus monkey. People whose RBCs have Rh
antigens are designated positive); those
who do not have Rh antigens are designated Rh
negative.
BLOOD VESSELS-
• Blood
vessels are part of the circulatory system that transports blood throughout the
body. Blood vessels vary in structure, size and function, and there are several
types:
• arteries,
arterioles, capillaries, venules and veins.
• The
arteries & arterioles carry the oxygenated blood away from the heart, the
capillaries, which enable the actual exchange of water, nutrients and chemicals
between the blood and the tissues; and the veins, which carry blood from the
capillaries back
•
ARTERIES AND ARTERIOLE-
These are the blood vessels that carry oxygenated blood
away from the heart. They vary considerably in size and their walls consist of
three layers of tissue
Ø
Tunica externa -It is the outermost layer of the arteries
and veins. It consists of collagen fibres and varies in thickness between the
vessels. The collagen serves to anchor the blood vessel to nearby organs,
giving it support and stability. The tunica externa contains numerous nerves
and, especially in larger vessels, tiny blood vessels that supply the tissue of
the vessel wall. These small vessels that supply blood to the tissues of the
vessel are called vasa vasorum
Ø Tunica
media - The tunica media (media
middle) is a muscular and connective
tissue layer that displays the greatest variation among the different vessel
types. In most vessels, it is a
relatively thick layer comprised mainly of smooth muscle cells and substantial
amounts of elastic fibers. The primary role of the smooth muscle cells is to regulate the diameter of the lumen.
Ø Tunica
intima - The tunica interna
(intima) forms the inner lining of a blood vessel and is in direct contact
with the blood as it flows through the lumen. Its innermost layer is a
simple squamous epithelium, called endothelium, which is continuous with
the endocardial lining of the heart. The endothelium is a thin layer of
flattened cells that lines the inner surface of the entire cardiovascular
system (heart and blood vessels). It is very smooth and
allow easy flow of blood.
CAPILLARIES-
The smallest arterioles break up
into a number of minute vessels called capillaries. Capillary walls
consist of a single layer of squamous cells with a membrane, through which water and other small
molecules can pass. Blood cells and large molecules such as plasma proteins do
not normally pass through capillary walls. The capillaries form a vast network
of tiny vessels that link the smallest arterioles to the smallest venules. In
certain places, including the liver and bone marrow, the capillaries are
significantly wider and permeable than normal. These capillaries are called sinusoids.
VEINS AND VENULES-
Veins are blood vessels that
return blood at low pressure to the heart. The walls of the veins are thinner
than those of arteries but have the same three layers of tissue such as tunica
externa, tunica media and tunica intima. They are thinner because there is less
muscle and elastic tissue in the tunica media, because veins carry blood at a
lower pressure than arteries. Some veins possess valves, which prevent
backflow of blood, ensuring that it flows towards the heart . They are formed
by a fold of tunica intima and strengthened by connective tissue. The valves
are semilunar in shape.
No comments:
Post a Comment