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Summary Course BBS1002 Homeostasis and organ systems
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HOMEOSTATIS AND ORGANSYSTEMS
BBS1002
Arjen Kalisvaart
, Case 01 Course BBS1002
What is blood?
1. Blood is a sticky fluid with a characteristic metallic taste. Depending on the amount of oxygen
it is carrying, the color of blood varies from scarlet (oxygen rich) to dark red (oxygen poor).
2. Blood is the only fluid tissue in the body. It is a specialized connective tissue.
3. Blood lacks the collagen and elastic fibers typical of other connective tissues, but dissolved
fibrous proteins become visible as fibrin strands during blood clotting.
4. Blood is slightly alkaline, with a pH between 7.35 and 7.45. Blood accounts for approximately
8% of body weight. Its average volume in healthy adult males is 5–6 and 4-5 L in healthy
adult females.
What are the functions of blood?
1. Distribution:
a. Delivering oxygen from the lungs and nutrients from the digestive tract to all body
cells.
b. Transporting metabolic waste products from cells to elimination sites (to the lungs to
eliminate carbon dioxide, and to the kidneys to dispose of nitrogenous wastes in
urine).
c. Transporting hormones from the endocrine organs to their target organs.
2. Regulation:
a. Maintaining appropriate body temperature by absorbing and distributing heat
throughout the body and to the skin surface to encourage heat loss.
b. Maintaining normal pH in body tissues. Many blood proteins and other bloodborne
solutes act as buffers to prevent excessive or abrupt changes in blood pH that could
jeopardize normal cell activities. Also blood acts as the reservoir for the body’s
alkaline reserve of bicarbonate ions.
c. Maintaining adequate fluid volume in the circulatory system. Blood proteins prevent
excessive fluid loss from the bloodstream into the tissue spaces. As a result, the fluid
volume in the blood vessels remains ample to support efficient blood circulation to
all parts of the body.
3. Protection:
a. Preventing blood loss. When a blood vessel is damaged, platelets and plasma
proteins initiate clot formation, halting blood loss.
b. Preventing infection. Drifting along in blood are antibodies, complement proteins,
and white blood cells, all of which help defend the body against foreign invaders
such as bacteria and viruses.
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,What are the components in the blood ?
Blood components:
1. Most of the reddish mass at the bottom of the tube is erythrocytes, the red blood cells that
transport oxygen.
a. Erythrocytes normally constitute about 45% of the total volume of a blood sample, a
percentage known as the hematocrit which is the “blood fraction”.
b. In healthy males the norm is 47% and in females it is 42%.
2. A thin, whitish layer called the buffy coat is present at the erythrocyteplasma junction.This
layer contains:
a. Leukocytes= The white blood cells that act in various ways to protect the body.
b. Platelets= Cell fragments that help stop bleeding.
c. Leukocytes and platelets contribute less than 1% of blood volume.
3. Plasma makes up most of the remaining 55% of whole blood:
a. Mostly water (about 90%)
i. Dissolving and suspending medium for solutes of blood and absorbs heat.
b. Nutrients:
i. Materials absorbed from digestive tract and transported for use throughout
body; include glucose and other simple carbohydrates, amino acids (protein
digestion products), fatty acids, glycerol and triglycerides (fat digestion
products), cholesterol, and vitamins.
c. Respiratory gases:
i. Oxygen and carbon dioxide; oxygen mostly bound to haemoglobin.
d. Hormones:
i. Steroid and thyroid hormones carried by plasma proteins.
ii. Not produced in the liver!
e. Wastes
f. Nonprotein nitrogenous substances:
i. By-products of cellular metabolism, such as urea, uric acid, creatinine, and
ammonium salts.
g. Proteins:
i. 8% (by weight) of plasma.
ii. All contribute to osmotic pressure and maintain water balance in blood and
tissues.
iii. All have other functions (transport, enzymatic, etc.)
iv. Albumin:
1. 60% of plasma proteins and produced by liver.
2. Acts as a carrier to shuttle certain molecules through the circulation.
3. An important blood buffer.
4. Major blood protein contributing to the plasma osmotic pressure:
the pressure that helps to keep water in the bloodstream.
v. Globulins: 36% of plasma proteins.
1. Alpha and beta are produced by liver; most are transport proteins
that bind to lipids, metal ions, and fat-soluble vitamins.
2. Gamma are antibodies which are released by plasma cells during
immune response. Not produced in the liver !
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, vi. Fibrinogen: 4% of plasma proteins and also produced by the liver. It forms
fibrin threads of blood clot.
h. Inorganic ions (electrolytes):
1. Sodium, potassium, calcium, magnesium, chloride, phosphate,
sulphate, and bicarbonate; helps to maintain plasma osmotic
pressure and normal blood ph.
What are the types of blood cells?
Erythrocytes
Structure:
1. Erythrocytes or red blood cells (RBCs)are small cells, about 7.5 μm in diameter.
2. Shaped like biconcave discs—flattened discs with depressed centres.
3. They appear lighter in colour at their thin centres than at their edges.
4. Mature erythrocytes are bound by a plasma membrane, but lack a nucleus and have
essentially no organelles.
5. Structural proteins allow the red blood cells to deform yet spring back into shape.
a. A network of proteins called spectrin is attached to the cytoplasmic face of the red
blood cells and maintains the biconcave shape of an erythrocyte. The spectrin net is
deformable, allowing erythrocytes to change shape as necessary to twist, turn, and
become cup shaped as they are carried passively through capillaries with diameters
smaller than themselves and then to resume their biconcave shape.
6. Its small size and biconcave shape provide a huge surface area relative to volume. The
biconcave disc shape is ideally suited for gas exchange because no point within the
cytoplasm is far from the surface.
7. Discounting water content, an erythrocyte is over 97% haemoglobin, the molecule that binds
to and transports respiratory gases.
8. Erythrocytes lack mitochondria and generate ATP by anaerobic mechanisms, they do not
consume any of the oxygen they carry, making them very efficient oxygen transporters
indeed.
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