Blood
Function
• The function of blood is to transport
substances, to distribute body heat, and to
maintain homeostasis in the body.
• Some materials transported include O2, CO2,
hormones, food nutrients.
• It distributes heat and maintains blood
pressure.
Capillaries
• Allows diffusion of nutrients (in) and waste
(out) between cells and blood.
• Walls: one cell thick
– Blood cells travel in single file.
– Blood travels slowly here to allow time for
diffusion of nutrients and waste.
Physical Characteristics of Blood
• Color range
– Oxygen-rich blood is scarlet red
– Oxygen-poor blood is dull red
• pH must remain between 7.35–7.45
• Blood temperature is slightly higher than body
temperature.
• Blood makes up about 8% of our body weight,
or 6 quarts (5-6 L)
Composition of Blood
• Blood is made up of plasma and blood cells.
• Blood is made up of plasma, red blood cells,
white blood cells, and platelets.
• Living blood cells are
suspended in a nonliving
matrix (plasma).
• Hemacrit:
Plasma
• Plasma is the liquid part of blood; it is 90%
water. This is a clear yellow (straw colored)
liquid with various substances dissolved in it.
• Includes many dissolved substances
– Clotting factors
– Nutrients
– Salts (metal ions)
– Respiratory gases
– Hormones
– Proteins
– Waste products
– Antibodies
Red blood cells
• The plasma carries millions of red blood cells.
They contain a protein called hemoglobin which
transports oxygen from the lungs to all parts of
the body.
• The amount of hemoglobin in the rbc determines
how much oxygen can be carried.
• Red blood cells are made in the bone marrow.
• They are recycled in the liver and spleen.
• No nucleus; lifespan of 80-120 days.
• Also called erythrocytes.
Red Blood Cells, Hemoglobin, Iron
to carry oxygen
• Hemoglobin is made of the protein globin and
bound to the red pigment, heme.
• Ever hmoglobin molecule contains 4 ring-like
heme groups; each bearing an atom of iron.
• Oxyhemoglobin; 4 oxygens bind to Hb; bright red.
• 20 % of carbon dioxide combines with Hb but
binds to amino acids in globin.
• https://www.youtube.com/watch?v=oC6dEoOIkw0
White blood cells
• The white blood cells help fight infection. They
are part of the immune system defense
component of pus.
• Their lifespan is 3-4 days.
• New white blood cells are also made in the
bone marrow.
• Also called leukocytes.
• While rbc are confined to the bloodstream,
wbc can slip in and out of blood vessels
(diapedesis).
Types of white blood cells
•
•
•
•
•
1. lymphocytes
2. monocytes
3. basophils
4. eosinaphils
5. neutrophils
In order of abundance
Never Let Monkeys
Eat Bananas
https://www.youtube.com/watch?v=ubqxJho6gdk
White blood cells
• Neutrophil—most abundant, Phagocytes at
site of infection, especially bacteria and fungi.
• Lymphocyte—T-cells (fight tumors and
viruses—direct cell attack) and B-cells (make
antibodies)—both are memory cells.
• Monocytes—turn into macrophages and
engulf pathogens, important in fighting
chronic infections (tuberculosis)
• Eosinophils—Allergies and infections by
parasitic worms by
• Basophil—contain histamine; attract other
wbc to infection sites.
https://www.youtube.com/watch?v=Tdx-U8S6ZMk
Platelets
• Platelets are small fragments of cell
membranes who come from bone marrow;
megakaryocytes.
• Their role is to help form clots to seal wounds,
stop bleeding, and prevent entry of
pathogens.
• Lifespan of 8-11 days.
• Also called thrombocytes.
Figure 10.1
Hematopoiesis (blood cell formation)
• Blood cell formation
• Occurs in red bone marrow
• All blood cells are derived from a common
stem cell (hemocytoblast)
• Hemocytoblast differentiation
– Lymphoid stem cell produces lymphocytes
– Myeloid stem cell produces other formed
elements
Fate of Erythrocytes
• Unable to divide, grow, or synthesize proteins
• Wear out in 100 to 120 days
• When worn out, are eliminated by phagocytes
in the spleen or liver; destroyed by
macrophages.
• Degraded to bilirubin (yellow pigment secreted
in bile by the liver)
• Requires Fe and B-complex vitamins.
• Lost cells are replaced by division of
hemocytoblasts
Control of Erythrocyte Production
• Rate is controlled by a hormone
(erythropoietin)
• Kidneys produce most erythropoietin as a
response to reduced oxygen levels in the
blood
• Homeostasis is maintained by negative
feedback from blood oxygen levels
Control of Erythrocyte Production
Figure 10.5
Blood Clotting (Hemostasis)
• Almost immediately after you suffer a cut, your
body reacts by initiating a series of events that
happen one after another until the bleeding
stops.
• This series of events depends on specific proteins
called clotting factors. Clotting factors are
substances in your blood that act in sequence to
stop bleeding by forming a clot.
• Clotting factors are dependent on Vitamin K to
function properly.
Hemostasis
• Stoppage of blood flow
• Result of a break in a blood vessel
• Hemostasis involves three phases
– 1. Vascular spasms
• Constriction of damaged blood vessel
• Serotonin enhances
– 2. Platelet plug formation
• Stick to damaged endothelium and collagen fibers
• Prostacyclin; inhibitor
– 3. Coagulation
• Prothrombin activator formed
• Prothrombin activator converts prothrombin into
thrombin.
• Thrombin catalzyes the joining of fibrogen molecules;
fibrin mesh.
Platelets are the first responders
• When a blood vessel wall is damaged, collagen
fibers from within the wall are exposed. These
exposed fibers become a place for platelets to
cling to. Platelets are irregular-shaped bodies
that help the clotting process by sticking to the
lining of the blood vessels. These odd-shaped
fragments of cells are normally found floating
around your blood along with your red blood
cells, kind of minding their own business. But
when the cells that line the blood vessels get
injured, they release chemicals that cause the
platelets to kick into action and become sticky
Some clotting factors
• Fibrinogen, is an inactive clotting factor that
helps bind the platelets to form a clot. These
inactive clotting factors act as little cross-links,
attaching the adjacent platelets to each other.
• Thromboxane A2 recruits more platelets to
the wound and acts as a vasoconstrictor,
slowing the rate of the flow of blood.
Vascular Spasms
• Anchored platelets release serotonin
• Serotonin causes blood vessel muscles to
spasm
• Spasms narrow the blood vessel, decreasing
blood loss
Platelet Plug Formation
• Collagen fibers are exposed by a break in a
blood vessel
• Platelets become “sticky” and cling to fibers
• Anchored platelets release chemicals to
attract more platelets
• Platelets pile up to form a platelet plug
Coagulation
• Injured tissues release thromboplastin
• PF3 (a phospholipid) interacts with
thromboplastin, blood protein clotting factors,
and calcium ions to trigger a clotting cascade
• Prothrombin activator converts prothrombin to
thrombin (an enzyme)
• Thrombin joins fibrinogen proteins into hair-like
fibrin
• Fibrin forms a meshwork (the basis for a clot)
Fibrin Clot
Figure 10.7
Undesirable Clotting
• Thrombus
– A clot in an unbroken blood vessel
– Can be deadly in areas like the heart
• Embolus
– A thrombus that breaks away and floats freely in
the bloodstream
– Can later clog vessels in critical areas such as the
brain
Blood Types
• Red blood cells can also be classified by blood
type. The 2 most important classifications are the
ABO and Rhesus blood types.
• ABO blood type is determined by the presence of
antigens A and B. Blood type A has only antigen
A, blood type B has only antigen B, blood type AB
has both, and blood type O has neither.
• Rhesus blood type is determined by one antigen.
Blood type Rh+ has the antigen and blood type
Rh- does not.
• Whenever a person receives blood, the received
blood must be the same type or a compatible
one. Receiving incompatible blood can be lifethreatening!
• AB is the universal receiver.
• O is the universal donor.
Blood Typing
Figure 10.8
Rh Dangers During Pregnancy
• The mismatch of an Rh– mother carrying an Rh+
baby can cause problems for the unborn child
– The first pregnancy usually proceeds without
problems
– The immune system is sensitized after the first
pregnancy
– In a second pregnancy, the mother’s immune
system produces antibodies to attack the Rh+
blood (hemolytic disease of the newborn)