Download The Circulatory System

The Circulatory System
What does our heart do?
Monitoring your pulse
• Find pulse in your wrist (the pulse you feel is blood rushing
through the brachial artery in your arm)
– Count the number of heartbeats in 30 seconds. Multiply this
number by 2 to calculate your heart rate for 1 min.
• Find pulse on side of your neck (the pulse you feel is blood
rushing through the carotid artery – the one that carries
blood to your head)
– Calculate heart rate for 1 min.
Compare the strength of the pulse in your carotid artery with your
brachial artery. What do you notice? Why?
Pulse: change in the diameter of the arteries following heart
contractions
• Run on the spot for 2 minutes.
• Take your pulse immediately for 30 seconds after
exercise using either the carotid or brachial
artery. Calculate your heart rate for 1 min.
• Compare your heart rate before and after
exercise. What do you notice?
• Do you think the difference between resting
heart rate and the heart rate after exercise would
be greater for athletes? Why or why not?
The Circulatory System
• Consists of the heart, blood vessels, and blood
• Fundamental purpose is to transport
substances from place to place in the body via
the blood
• Blood vessels ensure the proper routing of
blood to its destinations
• Heart is the pump that keeps the blood
flowing
Functions of the Circulatory System
• 3 main functions
– Transport
– Protection
– Regulation
Transport
• Blood carries oxygen from the lungs to all of the
body’s tissues, while it picks up carbon dioxide
from those tissues and carries it to the lungs to
be removed from the body
• It picks up nutrients from the digestive tract and
delivers them to all of the body’s tissues
• Carries metabolic wastes to the kidneys for
removal
• Carries hormones from endocrine cells to their
target organs
Protection
• The blood plays several roles in inflammation, a
mechanism for limiting the spread of infection
• White blood cells destroy microorganisms and
cancer cells
• Antibodies and other blood proteins neutralize
toxins and help to destroy pathogens
• Platelets secrete factors that initiate blood
clotting and other processes for minimizing blood
loss
Regulation
• Controls body temperature – homeostasis
• By absorbing or giving off fluid under different
conditions, the blood capillaries help to stabilize
fluid distribution in the body
• By buffering acids and bases, blood proteins
neutralize toxins and help to destroy pathogens
• Platelets secrete factors that initiate blood
clotting and other processes for minimizing blood
loss
So.. Why is an excessive loss of blood
quickly fatal?
• We need our blood to efficiently transport
nutrients, wastes, hormones and especially
oxygen from place to place
Components and Properties of Blood
• Adults generally have about 4 to 6 litres of
blood
• It is a liquid connective tissue composed of
cells and an extracellular matrix – the matrix is
the blood plasma which is a clear, light yellow
fluid making up a little over half of our blood
volume
• Suspended in the plasma are the formed
elements (RBCs, WBCs, and platelets)
Components of Blood
Hematocrit: Ratio of red blood cell volume to the total blood
volume
Formed Elements
• Erythrocytes (red blood cells, RBCs)
– Densest of the elements, constitute about 37% to
53% of total blood volume
– Contain hemoglobin, which increases the capacity
of oxygen that can be carried in the blood
– Two principal functions: 1) to pick up oxygen from
the lungs and deliver it to tissues elsewhere, and
2) to pick up carbon dioxide from the tissues and
unload it in the lungs
Formed Elements
• Leukocytes (white blood cells, WBCs)
– 5 types of leukocytes
• Granulocytes- Neutrophils, Eosinophils, Basophils
• Agranulocytes- Lymphocytes, Monocytes
– Total 1% or less of total blood volume (ratio of 700
RBCs to 1 WBC)
– Form special proteins, called antibodies, which
interfere with invading microbes and toxins
– Important part of the immune system
Formed Elements
• Platelets
– Included with WBCs in the total 1% or less of
blood volume
– Component of blood responsible for initiating
blood clotting
• Blood will not clot unless blood vessel is broken
• Substances released by the broken blood vessel will
attract platelets
Anemia
• A condition in which an individual does not
have enough healthy red blood cells to carry
adequate oxygen to the tissues
• Causes weakness and fatigue
• Can be temporary or long-term, and can range
from moderate to severe
• Prevention: eating a healthy, varied diet
• Treatment: supplements
Blood Groups
• Blood types A, B, AB and O are determined by
the hereditary presence or absence of
antigens A and B on the RBCs
• Universal Donor  Type O blood
• Universal Acceptor  Type AB blood
Table 1: Antigens and Antibodies Found in Blood
Groups p. 247 in textbook
Rhesus Factor
• During the 1940s , scientists discovered
another antigen on the red blood cell: the Rh
group (named after the rhesus monkey)
• Rh group is also inherited – Individuals who
have this special antigen (approx. 85% of
Canadians) are said to be Rh-positive
• Individuals who are Rh-negative may donate
blood to Rh-positive individuals, but should
not receive their blood
Blood Vessels
• Arteries
– Carry oxygenated blood away from heart
• Capillaries
– Connect the smallest arteries to the smallest veins
• Veins
– Carry deoxygenated blood to heart
Blood Vessels
• Arteries
– Every time the heart contracts, blood surges from
the heart and enters the arteries
– The arteries stretch to accommodate the inrush of
blood
– Blood from the arteries passes into smaller
arteries, called arterioles
Blood Vessels
• Walls of the arteries become narrow when fat
deposits along the artery wall
• Arterial size can also change during warm and
cold temperatures  winter weather constricts
the arterial size while hot weather causes dilation
of artery wall
• Blood flow through arteries is affected by
changes in arterial wall diameter
• Decreasing arterial size causes elevation of blood
pressure levels and strains the heart to do more
work, thus increasing the risk for a heart attack
Blood Vessels
• Capillaries
– Materials such as nutrients, wastes, hormones
and leukocytes pass between the blood and the
tissue fluids, through the walls of capillaries
– Capillaries are sometimes called exchange vessels
Blood Vessels
• Veins
– Unidirectional blood flow back to heart
• Valves- open in one direction, steering blood toward
the heart – they do not allow blood back in the other
direction
– Diameter of veins increases as blood returns to
the heart
– As much as 50% of total blood volume can be
found in the veins
Atherosclerosis
• Growth of lipid deposits in the arterial walls
• Deposits can become calcified plaques, giving
the arteries a hard, bonelike consistency
• As a result of these degenerative changes,
blood pressure rises with age
Predict-Observe-Explain
How does the size of blood vessels affect blood
pressure?
Blood Pressure
• The force that the blood exerts against a vessel wall
• Fluctuations can be created due to increased demands
on the body – how readily the body reverts back to a
normal level is indicative on one’s overall fitness
• Systolic pressure is the peak arterial BP attained during
ventricular contraction
• Diastolic pressure is the minimum arterial BP occurring
during the ventricular relaxation between heartbeats
• Arterial BP is written as a ratio of systolic over diastolic
pressure: 120/75 mm Hg is normal average – measured
using a sphygmomanometer
Hypertension
• Chronic high blood pressure
– Causes:
• Physical inactivity
• A salt-rich diet through processed and fatty foods
• Alcohol and tobacco use
• Plaque build up in arteries can cause damage to platelets and can
start to lead to a blood clot (embolism)
• Treatment:
– Exercise, better diet and medications (Asprin: helps prevent platelets
from sticking to one another)
– Surgery: Angioplasty- fine plastic tube inserted into artery and when a
constricted region is identified a balloon is blown up to force the
vessel open. Coronary bypass - involves removing a segment of
healthy blood vessel from one part of your body and using it to go
around a blockage near the heart. (The term double or triple refers to
the number of blood vessels containing blockages that must be
bypassed. (p.258, fig. 3)
Discoveries
• Ancient Greeks
– Heart was seat of intelligence
• Galen (Greek physician)
– In second century theorized that blood and veins were
separate and blood flowed out of each to the body
• William Harvey
– In seventeenth century theorized that we have a cyclic
circulatory system. He was never able to find the point
where blood stopped travelling away from the heart
and travelled back
• Marcello Malpighi
– In 1657 identified capillaries to back Harvey’s findings
The Mammalian Heart
• The Pulmonary and Systemic Circuits
– The two major divisions of the cardiovascular
system
Pulmonary Circuit- carries blood to the lungs for gas
exchange and returns it to the heart
Systemic Circuit- supplies blood to every organ of
the body, including other parts of the lungs and
the wall of the heart itself
heart  arteries  capillaries  veins  heart
The Mammalian Heart
• Right side
– Supplies the pulmonary circuit
– Receives blood that has circulated through the body, unloaded its oxygen and
nutrients, and picked up a load of carbon dioxide and other wastes
– Pumps oxygen-poor blood into a large artery, the pulmonary trunk, which
immediately divides into right and left pulmonary arteries
– These transport blood to the air sacs (alveoli) of the lungs, where carbon
dioxide is unloaded and oxygen is picked up
– The oxygen –rich blood then flows by way of the pulmonary veins to the left
side of the heart
• Left side
–
–
–
–
Supplies the systemic circuit
Blood leaves it by way of another large artery, the aorta
The aortic arch gives off arteries that supply the head, neck and upper limbs
After circulating through the body, the now deoxygenated systemic blood
returns to the right side of the heart, mainly by way of two large veins: the
superior vena cava (draining the upper body) and inferior vena cava (draining
everything below the diaphragm)
Heart Chambers
• 4 chambers
– The two superior chambers are the right and left
atria: they are thin-walled receiving chambers for
blood returning to the heart by way of the great
veins
– The two inferior chambers are the right and left
ventricles: they are the pumps that eject blood
into the arteries and keep it flowing around the
body
Heart Valves
• To pump blood effectively, the heart needs valves that
ensure a one-way flow
• There is a valve between each atrium and its ventricle and
another at the exit from each ventricle into its great artery
• The atrioventricular (AV) valves regulate the openings
between the atria and ventricles
• The semilunar valves (pulmonary and aortic valves)
regulate the flow of blood from the ventricles into the great
arteries
• The Lub-Dub sound your heart makes is due to these valves
opening and closing in the heart
– Lub  AV valves
– Dub Semilunar valves
The Mammalian Heart
Control of the Heart
– The impulse that causes the heart to beat is
actually in the heart itself
• A bundle of special muscle tissue, located in the right
atrium, stimulates muscle fibers to contract and relax
rhythmically.
• This tissue is called the sinoatrial (SA) node  AKA the
pacemaker
• SA node gives electrical impulse to both atria and
causes them to contract simultaneously
• The pulse will then reach the atrioventricular (AV) node
located between the two ventricles to start their
contraction
Recording a Heart Rate
– Electrocardiograph (ECG)  shows the duration of a single
beat
– Small voltage increase as the electrical depolarization that
accompanies contraction of the atria (P)
– Large spike accompanies the contraction of the ventricles
• Ventricular depolarization (QRS)
– As the ventricles recover another small spike shows the
electrical repolarization that precedes the next firing of the
SA node (T)
– Ventricular fibrillation – ventricles contract randomly
• Can be sometimes stopped. A strong electrical current to the
heart and SA node can take over again.
Electrocardiogram- ECG
Heart Rate & Fitness
•
•
Maximum heart rate is the fastest your heart can possibly beat
during activity, which decreases as you get older
Fitness relation is not in how many beats but in the length of
time it takes your heart to go from maximum to resting level
after activity
Stroke Volume & Fitness
1. How easily the heart fills with blood
• Depends on volume of blood returning in veins and the
distensibility or “stretchiness” of the ventricles
2. How readily the heart empties
• Depends on strength of ventricular contraction and pressure
exerted by artery walls
• Cardiovascular exercise enlarges the ventricular chambers,
increases distensibility of ventricles and strengthens ventricular
walls
• Strength training may simply increase thickness of ventricular
walls and limit stroke volume by reducing elasticity
Heart Defects
• Septal defect- hole in the septum (separates
right and left ventricles)
– Oxygenated and deoxygenated blood are able to
mix
Heart Defects
• Murmurs- one or more of heart valves not
closing properly
• Arrhythmias- irregular heartbeat
– When a coronary artery is blocked, it delivers less
blood and causes the heart to beat in an irregular
pattern
• Too slow heart rate (bradycardia)
• Too fast heart rate (tachycardia)
Lymphatic System
• Consists of a network of vessels that penetrate
nearly every tissue of the body, and a
collection of tissues and organs that produce
immune cells
• 3 main functions;
– Fluid recovery
– Immunity
– Lipid absorption
Lymphatic System
• Fluid Recovery
– Fluid continually filters from blood capillaries into
the tissue spaces
– Lymphatic system reabsorbs excess water that
blood capillaries do not absorb and returns it to
the blood
– Even partial interference with lymphatic drainage
can lead to severe edema
Lymphatic System
• Immunity
– As the lymphatic system recovers tissue fluid, it
also picks up foreign cells and chemicals from the
tissues
– On its way back to the blood stream, the fluid
passes through lymph nodes, where immune cells
stand guard against foreign matter
– When they detect anything potentially harmful,
they activate a protective immune response
Lymphatic System
• Lipid absorption
– In the small intestine, special lymphatic vessels
called lacteals absorb dietary lipids that are not
absorbed by the blood capillaries
Lymphatic System
Components of the Lymphatic System
• 1) Lymph, the recovered fluid
• 2) Lymphatic vessels, which transport the lymph
• 3) Lymphatic tissue (lymph nodes are round masses of
tissue that supplies lymphocytes to the bloodstream
and remove bacteria and foreign particles from the
lymph)
• 4) Lymphatic organs
– Spleen: acts as a reservoir for blood and a filtering site for
lymph
– Thymus gland: where lymphocytes mature, multiply and
differentiate (lymphocytes are WBCs that produce
antibodies)
Elephantiasis
A disease caused by lymphatic obstruction