Unit J: Circulation & Blood
BASIC FUNCTIONS OF THE CIRCULATORY SYSTEM
1.
2.
3.
4.
Transports oxygen from lungs to tissue
Transports carbon dioxide from tissue to lungs
Absorbs and transports nutrients from small intestine to tissues
Absorbs and transports water from stomach, small and large intestine
to tissues and lungs
5. Carries waste products (urea, ammonia…) to kidneys for removal
6. Transports hormones from glands to target organs
7. Distributes body heat from internal source to peripheral skin for
dissipation
8. Maintains pH in tissues (acts as a buffer with HHb)
9. Regulates fluid levels in tissues (along with the Lymphatic system)
10. Seals punctures in the skin or elsewhere by forming a blood clot; thus,
preventing loss of blood and body fluids
11. Fights infection; involved in body defense
A.
The Five Types of Blood Vessels
Basis of
Comparison
Arteries
Arterioles
Capillaries
Venules
Veins
1.
2.
3.
4.
5.
Function
Transport blood
AWAY from the
heart
Control blood flow
to capillaries
Interconnect
arterioles to
venules
Drain blood from
capillaries and join
to form a vein
Transport blood
TOWARDS the
heart
ARTERIES: (see page 226)
ARTERIOLES: (see page 227)
CAPILLARIES: (see page 241)
VENULES: (see page 227)
VEINS: (see page 226)
Structure
Location
Thick, elastic walls
Usually deep,
along bones
Thick, elastic walls,
precapillary
sphincters, thinner
walls
Very thin (1 cell thick)
walls
Leading towards
all capillaries
Thinner walls than
veins
Thin walls; contain
valves
Everywhere;
within a few cells
of each other
Often on the
surface
Often on the
surface
surrounded by
skeletal muscle
Circulatory Pathways:
Systemic Circulation: the system of blood vessels that delivers oxygenated
blood to the body systems.
Pulmonary Circulation: the system of blood vessels that delivers
deoxygenated blood to the lungs to be replenished with oxygen.
*What’s the big deal? The systemic arteries carry oxygenated blood. The
pulmonary arteries carry deoxygenated blood.
B.
The MAJOR BLOOD VESSELS OF THE BODY
Aortic Arch
1. AORTA:
This major blood vessel carries oxygenated blood from the left
ventricle to the body systems.
When the aorta leaves the left ventricle, it loops over the top of
the heart, creating the AORTIC ARCH, and descends along the
inside of the backbone, creating the DORSAL AORTA.
Other arteries branch off this main artery to ‘feed’ the
body cells.
Dorsal Aorta
Superior Vena Cava
2. VENA CAVAS
The superior and inferior vena cavas are the largest
veins in the body. They are the location where all other
veins converge to. All veins from above the heart drain
into the superior vena cava while blood from below the
heart is collects in the inferior vena cava
Inferior Vena Cava
3. CORONARY ARTERIES/VEINS:
The very first branches of the aorta are the coronary
arteries (relatively small blood vessels that FEED the
heart muscle).
WHY CAN’T THE HEART JUST GET ITS OXYGEN AND
NUTRIENTS FROM THE BLOOD THAT PASSES THROUGH IT?
The muscle tissue is too dense and thick, and the
blood travels though it too quickly for diffusion to
occur.
4.
CAROTID ARTERIES:
These arteries branch off the aortic arch to take the
blood to the head; including the brain. They are
highly specialized with CHEMORECEPTORS that
detect oxygen content and PRESSURE RECEPTORS
that detect changes in blood pressure. The carotid
arteries run reasonably close to the surface, so the
pulse can be found along both side of the neck.
5.
JUGULAR VEINS:
These veins correspond to the carotid arteries and take blood out of
the head region and to the anterior vena cava. These veins DO NOT
contain any valves! Therefore, the blood flow through them is
under the influence of gravity (try standing on your head for a
while).
6. SUBCLAVIAN ARTERIES/VEINS:
These arteries branch off of the aorta and travel under the clavicle
(collar bone). They branch to feed the arms (via the BRACHIAL
ARTERIES) and the chest wall region.
It is interesting to note that the lymphatic ducts join the circulatory
system right before the subclavian veins meet up with the anterior
vena cava.
7. MESENTERIC ARTERIES:
These arteries branch off from the
dorsal aorta. They go to the
intestines, where they branch into
the capillaries that can be seen in the
villi. They pick up the newly
digested nutrients and carry them to
the liver.
8. HEPATIC PORTAL VEIN:
Mesentery
Hepatic = Liver; Portal = capillary bed on either end. This vein
transports blood rich in nutrients directly from the intestines to
the liver. You have already studied all of the functions of the
liver. Significant functions for the circulatory system are:
regulation of blood glucose concentration, destruction of aged
RBC’s, and detoxification of blood.
9. HEPATIC VEIN:
Carries the blood from the hepatic
portal vein to the inferior vena cava.
RENAL ARTERIES/VEINS:
The renal arteries branch off the
dorsal aorta and bring blood to the
kidneys. The renal veins take
blood from the kidneys to the
posterior vena cava. We will
discuss this in depth in Unit O
(Urinary System).
10
ILIAC ARTERIES/VEINS:
When the dorsal aorta gets to the pelvic
area, it branches into two iliac arteries.
One goes down each leg. The femoral
artery is a major branch of the iliac
artery that serves the large quadricep
muscle of the leg. The iliac veins bring
the blood back to the posterior vena
cava.
11
PULMONARY VEINS/ARTERIES:
The deoxygenated blood has been collected from the
rest of the body moves into the right atrium and then
ventricle, and is pumped into the pulmonary artery
and taken to the lungs to be replenished. The
pulmonary vein takes the newly oxygenated blood
back to the heart and into the left atrium and then
ventricle (where it is pumped into the aorta and to the
rest of the body).
C. The BLOOD
Blood is more than just a red liquid that leaks onto your best white shirt when
you cut yourself.
What is Blood?
55% Plasma (liquid)

91% Water

7% Proteins

Salts, gases (oxygen, carbon dioxide), nutrients
(fats, glucose,amino acids), urea, hormones, vitamins…
45% Solid
(formed
elements)
Red Blood
Cells
White
Blood Cells
Platelets
*An interesting note about RED BLOOD CELLS: the liver and kidneys are
sensitive to the amount of oxygen that is being delivered to them. They both
respond by releasing chemicals if the level of oxygen delivered to them
drops. The kidneys release REF (RENAL ERTHROPIOETIC FACTOR) and the
liver releases specialized GLOBULINS. The combination of these 2
substances stimulates the red bone marrow to increase the rate of production
of erythrocytes (RBC’s). It takes several weeks to build up the rate of
erythrocyte production and this is why it takes a while to become
ACCLIMATIZED when you visit or move to a higher elevation.
SOLID PORTION OF THE BLOOD (see page 236):
FORMED ELEMENTS
Red Blood Cells
(Eyrthrocytes)
Function & Description
Transports oxygen and helps
to transport CO2

4-6 million/mm3 blood
White Blood Cells
(Leukocytes)
Bioconcave disks without
nuclei that are bright red
to dark purple in colour
 Pass through several
developmental stages
during which they lose a
nucleus and gain a
hemoglobin & carbonic
anhydrase molecule and
an antigen (the basis for
blood type).
 Live for ~120 days (4
months)
Fights Infection
a. Granular
leukocytes
1) Basophils
(0.5 – 1%)
Spherical cells with lobed
nuclei. Release HISTAMINE
when damaged. Leads to
swelling as it increases the
permeability of capillary walls;
allowing water to leak into
tissues.
2) Eosinophils
(1 – 4%)
Spherical cells with bilobed
nuclei. Are PHAGOCYTIC &
engulf and destroy foreign
things in blood.
3) Neutrophils
(55-75%)
Spherical cells with multilobed
nuclei. Are also PHAGOCYTIC
and make up ~ ¾ of all blood
cells!
b. Agranular
leukocytes
Are further specialized into TCELLS and B-CELLS. T-cells
mature in thymus and are the
TRIGGERS of the immune
Source
Red bone
marrow
(p. 238 – the
formation of
RBC, WBC, &
platelets)
Red bone
marrow
1) Lymphocytes
(20-30%)
2) Monocytes
( 2 – 8 %)
Platelets
(Thrombocytes)
150,000 to 300,000 / mm3
blood
system.
One type of T-cell signals the
production and release of
ANTIBODIES from B-cells.
Lymphocytes are the 2nd most
abundant type of WBC.
PHAGOCYTIC
Enlarge greatly in size at the
site of an infection.
Aid in clotting the blood
Disk-shaped cell fragments with
no nuclei. We produce ~
200,000,000,000 per day
Red bone
marrow
There is a series of reactions
that lead to the formation of a
blood clot.
PLASMA PORTION OF THE BLOOD (see page 236):
PLASMA ELEMENTS
Water (90-92% of plasma)
Function
Maintains blood volume;
transports molecules
Source
Absorbed from
large intestine
Plasma Proteins (7-8% of
plasma)
Maintain blood osmotic
pressure & pH, blood
clotting, fight infection
Osmotic balance (maintain
blood volume & pressure), pH
buffering
Blood clotting
Liver
a) ALBUMIN
b) FIBRINOGEN
c) IMMUNOGLOBULINS
Salts (>1% of plasma)
Na+, K+, Cl-, NaCO3… etc
Transport; fight infection with
antibodies (lymphocytes)
Maintains blood osmotic
Pressure and pH; aid
metabolism
Absorbed from
intestinal villi
Gases
a) OXYGEN
Cellular Respiration
Lungs
b) CARBON DIOXIDE
Nutrients
a) FATS
End product of Metabolism
Tissues
Protection, Insulation, Energy
b) GLUCOSE
Energy for Cellular Respiration
Absorbed from
intestinal villi
c) AMINO ACIDS
Used to make functional and
structural proteins we need
d) NUCLEOTIDES
Used to make nucleic acids
(DNA, RNA)
Nitrogenous Waste
Wastes: urea, ammonia
Hormones, Vitamins,
etc…
(Thyroxin, adrenalin, Vit.
K)
Aid the process of
metabolism
Liver
Varied
THE FORMATION OF A BLOOD CLOT (positive feedback):
1. The first step is that the PLATELETS must become DAMAGED in some
way. This could be as simple as impact, or platelets rubbing against
the rough edge of a blood vessel that has been damaged.
2. Platelets respond by releasing a protein called THROMBOPLASTIN.
3. The thromboplastin initiated the CONVERSION of PROTHROMBIN (a
blood protein produced by the liver) into THROMBIN. This reaction
requires the presence of CALCIUM.
4. Thrombin then catalyzes a second reaction which results in the
CONVERSION of FIBRINOGEN into FIBRIN. Fibrin (unlike all of the
other proteins just mentioned) is INSOLUBLE and therefore forms a
BLOOD CLOT in the area that has been damaged.
PLATELETS are DAMAGED
Thromboplastin
Ca++
Prothrombin
>>>Thrombin
Fibrinogen
>>>>FIBRIN
BLOOD
CLOT
Capillary Fluid Exchange
Arteriole: Blood Pressure > Osmotic Pressure
 The blood reaches a capillary bed through an arteriole. At this
point blood pressure has decreased to about 35 mmHg.
 This pressure is significant enough to force the water out of the
blood plasma, through the capillary walls, and into the tissue
spaces.
 This water carries with it the HbO2 (oxygen) and nutrients
(products of digestion).
 Because the [oxygen] in the tissues if greater than the
[oxygen] in the cells, the oxygen will diffuse into the body
cells.
 Nutrients will move into the tissue spaces and into the cells at
the same time.
 The larger things stay in the blood as they are too big to get
out (ie: fibrinogen, albumin, prothrombin, platelets, RBC,
WB
 Now, the blood is really concentrated (has very little water)
and on the venule side of the capillary, the water from the
tissue fluids is drawn back into the capillaries due to osmotic
pressure.
 When the fluid returns, it brings with it CO2 (a product of
cellular respiration that is more concentrated in the tissue
spaces than in the plasma) and other metabolic wastes like
ammonia.
 Venule: Osmotic Pressure > Blood Pressure
 The blood pressure on the venule side of the capillary bed is
now only ~15 mmHg.
 The end result of the change is that there is no change in the
blood volume. (*unless there is histamine involved – we will
discuss this later).
Comparison of Velocity, Blood Pressure &
Cross-sectional Area of Vessels
BLOOD TRACINGS
 Start in the Left Ventricle and go through the digestive
system and back to the left ventricle
Fetal Circulation:
A fetus does not use its pulmonary circuit. Therefore, the main difference
between fetal circulation and adult circulation is the fact that the fetus receives
its O2 blood from the placenta, and does not use its lungs. To do this, there
are four features in the fetus not present in the adult.
Oval opening or foramen ovale
This is an opening between the Left and Right atria which is covered by a flap
that acts as a valve. It allows the blood to bypass the lungs and reroutes most
of the blood that enters the right atrium directly into the left atrium.
Arterial duct or ductus arteriosus
This is a small arterial connection, like a shunt, between the pulmonary artery
and the aorta. It further allows blood to bypass the lungs.
Umbilical Cord
The Umbilical Cord has three blood vessels traveling through it. The largest
one is the umbilical vein, which transports blood with oxygen and nutrients
into the fetus. The other two are the umbilical arteries, which branch off of
the iliac arteries in the fetus, and take “spent” (wastes and CO2) blood back
into the mother via the placenta.
Venous duct or ductos venosus
This blood vessel is the extension of the umbilical vein to the vena cava. The
umbilical vein carries oxygenated blood, which mixes with unoxygenated
blood in the vena cava. Blood is delivered to the fetal liver for treatment
through the hepatic portal vein, but this comes after the blood goes through
the heart and is distributed to the body. This is why the fetus is so susceptible
to toxins in blood, as the liver functions are initially bypassed.
CHANGES AT BIRTH
The First Breath: the lungs are filled with air instead of fluid and
1.
this allows for vascular resistance to decrease. Higher oxygen levels in the
blood and alveoli results in an increase in pulmonary blood flow.
2.
Anatomical Changes:
 The placenta is removed from circulation.

The foramen ovale, ductus venosus, and ductus arteriosus close.
Why? Higher pressure in the left atrium due to increased pulmonary
blood flow causes the foramen ovale to close. Higher concentrations of
oxygen in the blood, decreased prostaglandin levels and decreased
pulmonary vascular resistance closes the ductus arteriosus. When the
umbilical cord is clamped, the umbilical vein closes, systemic vascular
resistance is increased, and this causes the ductus venosus to close.
E. ANTIGENS, ANTIBODIES, & BLOOD TYPING
These are two different types of proteins that have very different,
but related functions.
 An ANTIGEN: a protein identification on the surface of a
RBC. Made up of a protein and glycoprotein on a RBC’s outer
membrane.
 There are two kinds of antigens that can be on human RBC's,
A & B. . .Therefore, there are 4 possibilities of
blood types:
Antigens for each blood type
1. Antigen A:
2. Antigen B:
Type A Blood
Type B Blood
3. Antigens A&B: Type AB Blood
4. No Antigens:
Type O Blood
An ANTIBODY: (made by the B cells in the body) a protein
designed to combat a foreign protein. When they come in contact
with foreign antigens on cells that are not supposed to be in the
blood, they will bind to them. This causes the agglutination of the
foreign cells. Other WBC will then destroy the agglutinated cells.
Within the plasma (blood fluid), are the antibodies of the antigens
that are not present in the blood.
Antibodies for each blood type
Type A has B antibodies
Type B has A antibodies
Type O has A and B
antibodies
Type AB has no
antibodies
Antigen + Antibody
(foreign)
(body)
Inactive complex
(agglutination)
 This explains why blood transfusions have to be carefully
worked out before they are administered. Obviously, the
introduction of foreign RBC with antigens different from the
recipients RBC will cause agglutination. On a large scale,
this leads to death.
DONOR
R
E
C
I
P
I
E
N
T
BLOOD
TYPE
A
B
AB
O
A
B
YES
X
X
YES
X
YES
X
YES
AB
YES
YES
YES
YES
O
X
X
X
YES
X=AGGLUTINATION
*all agglutinated RBC will be destroyed by
phagocytosis
F. ERYTHROBLASTOSIS & THE Rh SYSTEM
 The Rh factor is another antigen that may be present on the
RBC. The presence of this antigen plays a role in childbirth.
If you are Rh+ you have the antigen and don’t have the ‘D’
antibodies.
(85% of Caucasions are Rh+)
If you are Rh – you don’t have the antigen. You don’t
normally have the ‘D’ antibodies, but can make them if you
are exposed to Rh antigens.
If Rh antigens are mixed with Rh antibodies, clumping
occurs.
 This becomes important in pregnacies because a Rhmother can have and Rh+ baby. Normally, the mother / fetal
blood does not mix or cross the placenta. At birth, there is
usually some mixing, so the mother begins to produce Rh
antibodies in response to the Rh antigens on the baby's
RBC's introduced during birth. There is no danger for either
the mother or the first baby. If the mother becomes pregnant
with another Rh + baby, Rh (‘D’) antibodies now in the
mother's plasma are small, and may cross the placenta
and agglutinate the baby's blood. This causes the baby to
die / be still born (Erythroblastosis).
How can this be prevented? Doctors can destroy the 1st baby's Rh
+ blood cells in the mother's plasma just after the 1st baby's birth
before the mother has time to make the Rh antibodies in her
plasma. An injection of Rh immune globulin injection
(RhoGAM) does this.
D. The LYMPHATIC SYSTEM
(Chapter 14)
The lymphatic system is a system of thin-walled
vessels with valves (like veins) that start in the
tissue spaces throughout the body.
FUNCTIONS?
1. Take up excessive tissue
fluids
2. Transport fatty acids and
glycerol (from intestines)
3. Fight infection
(lymphocytes)
4. Trap and remove cellular
debris form tissue fluid
Lymphatic Structures:
1. Lymph Vessels: The
lymph capillaries drain
excess fluids and plasma
proteins, and transport this
fluid through a CLEANSING
PROCESS controlled by the
Lymph Nodes. The
smooth muscle around the
vessels and the skeletal
muscle surrounding the
vessels both contract to
move the lymph towards
the nodes and elsewhere.
The cleansed ‘lymph’
travels through lymph
ducts back to the
circulatory system where
they meet up with the subclavian veins just as they are
dumping their contents into the anterior vena cava.
2. Lacteals: blind ends found in the villi of the small intestines
which absorb and transport fats.
3. Lymph Nodes: small ovoid/round structures packed with
phagocytic macrophages. These macrophages produce
lymphocytes which produce T and B cells. These cells
produce antibodies that combine with and deactivate foreign
proteins found on bacteria, cancerous cells, and
incompatible blood types, etc….
4. Other lymphoid organs: Tonsils, Appendix, Spleen, and
Thymus Gland. All fight infection and make WBC’s.

How do antibodies do their job?