Circulatory and

Respiratory Systems

SECTION 1 – THE CIRCULATORY SYSTEM

Most cells are not in direct contact with external environment

Circulatory system acts as transport serviceTwo fluids move through:

Blood à cardiovascular systemBlood, heart, blood vesselsLymph à lymphatic system

Lymph, lymph nodes, lymph vessels

The heart

■Central organ of cardiovascular system■Beats more than 2.5 BILLION

times in average life span■ In thoracic cavity behind

sternum, between lungs

■ Pericardiumàtough, saclike membrane surrounds the heart

– Secretes fluid to reduce friction as heart beats

■ Septumàvertically divides heart into two sides

■ Right side of heart

■ Pumps blood to lungs to get oxygen

■ Left side of heart

■ Receives blood from lungs, pumps to rest of body

Upper chambers à atria(singular atrium)

Lower chambers à ventricles

■ One-way valve separates each atrium from ventricle àatrioventricular(AV) valves

■ On the right side àtricuspid valve

■ On left side àmitral valve

■ Prevents backflow

■ Semilunar (SL) valves à separates ventricles from vessels

■ Pulmonary valve on right

– Separates right ventricle from pulmonary arteries■ Aortic valve on left– Separates left

ventricle from aorta

Circulation in the heart■ Blood from body

is deoxygenated (high CO2) enters right atrium through superior vena cava (from upper body) and inferior vena cava (from lower body)■ Right atrium

pumps blood into right ventricle

■ Right ventricle contracts to pump blood into pulmonary arteries on way to lungs

■ In lungs, CO2diffuses out, O2diffuses in

■ Oxygenated blood returns to left atrium

■ Left atrium pumps blood into left ventricle

■ Left ventricle pumps blood into aorta(largest vessel in body)

■ Aorta transports blood to all parts except lungs

Control of heartbeat

■ Heart consists of muscle cells that contract in waves■ When first group stimulated, they in turn stimulate neighboring

cells■ Chain reaction continues until all cells contract■ 2 areas of specialized tissue (nodes) control the heartbeat

Sinoatrial (SA) node ■ Sinoatrial node located in right atrium

■ Initiate own electrical impulse and contract

■ “pacemaker” because it sets the pace of the heartbeat

■ Impulse travels to AV node

Atrioventricular (AV) node

■ Located in septum between atria

■ Sends impulse to muscle cells in ventricles

■ Ventricles contract a fraction of a second after atria

■ Average 70 times a minute

Phases of heartbeat

■ Systole à occurs when ventricles contract

■ Closes AV valves

■ Opens SL valves so blood pumps into aorta and pulmonary arteries

■ Diastole à occurs when ventricles relax

■ Closes SL valves

■ Opens AV valves

■ Opening/closing of valves creates the “lubb dubb” sound

Blood vessels■ “Closed” circulatory system because

blood contained at all times (in heart, in vessels)■Open circulatory system à blood

leaves vessels and soaks tissues■Blood vessels help keep blood going

in one direction

Arteries

■ Large and muscular■ Carry blood AWAY from heart■ Walls have 3 layers1. Inner endothelial2. Middle smooth muscle3. Outer connective tissue■ Gives strength and elasticity■ Pulse à feel arteries stretching

Blood pressure■ Blood pressure àforce that blood applies to walls of blood vessels■ always highest in

two main arteries coming out of heart■ Measured in artery

in arm

Measuring blood pressure

■Cuff placed on arm, inflated to temporarily stop flow of blood through artery■Column of mercury attached rises as

pressure in cuff increases■Release air in cuff and listen to artery with

stethoscope and watch column of mercury

Systolic pressure■ First sound of blood

passing through artery means ventricles pumped with enough force to overcome pressure by cuff

■ This is called systolic pressure à pressure of blood when ventricles contract

■ Normal adult = 120mmHg males/110mmHg females

Diastolic pressure

■ Continuing to release air in cuff, listen for sound to disappear

■ Indicates steady flow of blood through artery

■ Pressure of blood sufficient to keep arteries open constantly even with ventricles relaxed

■ This is called diastolic pressure■ Normal adult = 80mmHg

males/70mmHg females

High blood pressure■ Hypertensionà high blood pressure

■ Puts strain on walls of arteries

■ Increases chance it will burst

■ Usually no external symptoms

Capillaries■ From aorta, blood travels through smaller arteries■ Smaller arteries branch into even smaller vessels

called arterioles■ Arterioles branch into smallest vessels, capillaries■ One cell thick■ Network so extensive that all 100 trillion cells in

body are 125 MICROmeters away from a capillary■ Allows for quick exchange of materials

Veins

■ Capillaries merge to form larger vessels called venules

■ Venules merge together to form veins à carries blood TOWARDS the heart

■ Inferior vena cava à from lower body

■ Superior vena cava à from upper body

■ Walls of veins made of same 3 layers as arteries

■ Thinner, less muscular■ Under less pressure from blood than arteries■ With less pressure, blood can flow backward■ To prevent this, valves in veins help blood in

one direction■ Many veins pass through skeletal muscle– When muscle contracts, squeeze blood through

veins– When muscle relaxes, valves shut

PATTERNS OF CIRCULATION

2 primary subsystems:Pulmonary circulationà between heart and lungs

Systemic circulationà between heart and body

Pulmonary circulation

■ Deoxygenated blood from body enters right atrium pumped to right ventricle■ When right ventricle contracts, blood sent through

pulmonary artery to lungs– Only artery to carry deoxygenated blood– Branches to 2 smaller arteries, one going to each lung■ In lungs, CO2 diffuses out of capillaries and O2 diffuses

in

■ Oxygenated blood flows into venules which merge into pulmonary veinsthat lead to left atrium

– Only veins to carry oxygenated blood■ From left atrium to

left ventricle to rest of body

Systemic circulation■Between heart and all other parts

of body■ Into aorta then to subsystems of

systemic circulation

1. Coronary circulation■ Supplies blood to heart itself

■ Heart muscle is thick

■ Oxygen, nutrients must be supplied to each cell

■ If blocked, muscle cells die

■ Atherosclerosis à disease caused by fat deposits

■ Can result in:– Heart attack (blockage in

heart)– Stroke (blockage in brain)

2. Renal■ Supplies blood to

kidneys■ Almost ¼ blood

pumped into aorta flows to kidneys■ Because kidneys

filter waste from blood

3. Hepatic portal■ Supplies blood to liver■ Excess

nutrients in blood stored in liver for future use

Lymphatic system

■ Also included in circulatory system■ One function is to return fluids that have built up in tissues

back to bloodstream■ Fluids = lymph■ Lymph vessels merge to form larger vessels■ Similar in structure to capillaries and veins BUT– No circulation, just one-way back to blood– No pump like the heart

■ Lymph is transparent yellowish fluid

■ Passes lymph nodes– Filters lymph as it

passes– Also store lymphocytes

à white blood cells■ When you get infection

à lymph nodes are swollen, tender from increased number of lymphocytes

BLOOD

Blood is a liquid connective tissue that makes up thetransport medium of the cardiovascular system. Itstwo main functions are to transport nutrients andoxygen to the cells and carry carbon dioxide andother waste materials away from the cells. Blood alsotransfers heat to the body surface and plays a majorrole in defending the body against disease.

Composition of the blood

■ Made of liquid medium and blood solids

■ Liquid makes up 55% (plasma)

■ Solids make up 45% (red blood cells, white blood cells, platelets)

■ Healthy adult contains about 4-5 liters

Plasma

■ Liquid medium of blood■ Sticky, straw-colored fluid■ 90% water■ Cell nourishment is dissolved in plasma– Vitamins– Amino acids– Glucose■ Plasma also carries hormones, waste, and proteins– Albumin à protein important to regulate osmotic pressure– Antibodies à help fight disease

Red blood cells■Erythrocytes à transport oxygen to

cells ■Formed in red marrow■Make large amount of iron-

containing protein called hemoglobin– Molecule that transports oxygen

■During formation, nucleus and organelles disintegrate■Last 120-130 days■30 trillion in body■2 million disintegrate every second■New ones formed at the same rate

White blood cells

■ Leukocytes à help defend body against disease

■ Formed in red marrow, lymph nodes and spleen

■ Larger than erythrocytes

■ Less numbers than erythrocytes

■ 1 mm3 blood = 4 million RBC 7,000 WBC

■ Can squeeze through openings in walls of blood vessels

RBC vs. WBC

RBC

■ Biconcave shape, smooth surface■ Short-lived (a few months)■ Only one type

WBC

■ Irregular shape, rough surface■ Long lasting (many years)■ Several types

Types of white blood cellsPhagocytes à One type of white blood cell■ Engulf invading microorganisms

■ Another type produces antibodiesà proteins that help destroy substances (bacteria/viruses)

■ When you have an infection, your number of white blood cells can DOUBLE!!!

Platelets

■ Essential to the formation of a blood clot■ Blood clot à mass of interwoven fibers and

blood cells that prevents excess blood loss■ Platelets are NOT whole cells■Don’t have nucleus■ Last 7-11 days

Blood clotWhen blood vessel is

damaged:

■ Platelets gather at damaged site, sticking together to form a small plug

■ Vessel constricts, slowing blood flow to area■ Special clotting factors released from

platelets■ Clotting factors start series of chemical

reactions■ End product = fibrin à protein molecules

made of long, sticky chains■ Form a net to trap red blood cells■ Hardens to form scab

Fibrin

Blood types

■ Blood type à determined by type of antigen present on surface of RBC

■ Antigen à protein or carbohydrate that acts as signal, letting body recognize foreign substances

■ Antigens normally present = no response■ Antigens NOT normally present = body produces antibodies

■ Antigen = “antibody-generating substance”

1900s - Karl Landsteiner

■ 4 groups of blood type■ Discovered by mixing types together■ Landsteiner wanted to know why some blood transfusions caused

problems, others not■ Mixed two different blood samples together, saw clotting■ Other times, no clotting

■ Landsteiner’s observations led to modern classification based on 3 antigens – A, B, and Rh

A-B-O systemBlood types Antigen on red

blood cellsAntibodies in

plasmaCan get blood

fromCan give blood

to

A A Anti-B O, A A, AB

B B Anti-A O, B B, AB

AB A and B None A, B, AB, O AB

O None Anti-A, Anti-B O A, B, AB, O

Identifying OffspringTwo babies are believed to have been switched at birth.

Blood samples were taken from each of the parents and babies. The following results were obtained from the blood samples:

Family 1: mother, type B; father, type O; baby, type AFamily 2: mother, type O; father, type A; baby, type O

Rh system

■ Rh factor à antigen sometimes present (85% human population)■Named after rhesus monkey in which it was

first discovered■ If Rh- person receives transfusion from Rh+

person, antibodies will react with antigen and clotting will happen

■ Most serious problem happens during pregnancy■ If mother is Rh- and father is Rh+ the child may inherit Rh+■ During delivery small amount of baby’s blood may reach

mom’s bloodstream■ She will develop antibodies■ If second Rh+ child is conceived later, antibodies attack

fetus – erythroblastosis fetalis■ Fetus can die, or if born, needs immediate transfusion

■To prevent this, Rh- mom can be given antibodies to destroy Rh+ cells that have entered her bloodstream■Mom is “immunized” before her body

develops its own antibodies

RESPIRATORY SYSTEM

Involves external respiration (exchange of gasesbetween atmosphere and blood) and internalrespiration (exchange of gases between blood andcells of body)

The lungs■ Site of gas exchange between atmosphere and blood

■ Right lung has 3 lobes (divisions)■ Left lung has 2 lobes■ Located in thoracic cavity■ Bound by rib cage and diaphragm■ Pleura à membranes that line entire cavity and

encase the lungs– Secrete slippery fluid– Decreases friction from movement of lungs

Passage of air■ External respiration begins at nose and mouth

Air filters through small hairs of nose

Passes into nasal cavity above the roof of the mouth

■ Mucous membranes warm and moisten air

■ Prevents damage to delicate tissues in respiratory system

■ Walls lined with cilia à traps particles inhaled

– Swept into throat and swallowed

Moistened, filtered air move into pharynxàtube at back of nasal cavities and mouth■ Contains passageways

for both food and air■ When food

swallowed, epiglottis(flap of cartilage), presses down and covers opening to air passage

When breathing, epiglottis is upright

Air passes through cartilaginous tube called the trachea■ 10-12 cm■Walls lined with

cilia to trap inhaled particles

Upper end of trachea is the larynx■ Sounds made when

air forced past two ligaments (vocal cords) stretched across larynx ■ Pitch and volume

varies with amount of tension of cords and amount of air being forced past

Trachea branches into two bronchi

■ Each leads to a lung■ Walls of bronchi made

of smooth muscle and cartilage, lined with cilia and mucus

In lungs, bronchi branch into smaller and smaller tubes

■ Smallest are bronchioles also lined with cilia and mucus

■ Bronchioles end in clusters of tiny air sacs called alveoli■ Network of capillaries surrounds each■ Each lung contains about 300 million

alveoli■ Total surface area = 70m2 (twice of skin)

GAS EXCHANGE AND TRANSPORT

In the lungs, gases are exchanged between the alveoliand the blood in the capillaries. Oxygen to betransported throughout the body moves into thebloodstream, and carbon dioxide to be eliminatedfrom the body moves into the alveoli.

Gas exchange in the lungs

■ When air moves into the lungs, oxygen in air moves across the alveolar membranes and then the capillary membranes

■ Carbon dioxide moves in opposite direction■ Air moving in is rich in oxygen■ Blood in capillaries has low levels of O2 and high levels of

CO2■ Difference in concentration causes the diffusion of these two

gases

Hemoglobin and gas exchange

■ 97% of the oxygen moves into the red blood cells, where it combines with hemoglobin

■ Each hemoglobin has 4 iron atoms

■ Each can bond to one oxygen molecule

■ When oxygenated blood reaches cells, concentration of oxygen higher in blood than in surrounding cells

■ Oxygen diffuses into cells

Elimination of CO2

■ Only 8% of CO2 dissolves in plasma■ 25% binds to hemoglobin■ Other 67% reacts with water in plasma to form carbonic acid■ Carbonic acid dissociates into bicarbonate ions and a proton■ When it reaches the lungs, the reactions are reversed■ Bicarbonate ions combine with proton to form carbonic acid,

which in turn forms CO2 and water

Mechanisms of breathing

■ Breathing is the process of moving air into and out of the lungs

■ Inspiration à taking air into lungs

■ When you take a breath your chest expands as muscles contract to move ribs up and out

■ At the same time the diaphragm flattens and pushes down

■ Increases volume of thoracic cavity

■ Increase in volume reduces pressure

– Lower inside lungs than outside body

– Forces air into lungs■ Expirationà releasing air

from lungs■ Diaphragm and ribs relax■ Volume of thoracic cavity

decreases■ Pressure increases■ Forces air out of lungs

Regulation of breathing

■ Rate of breathing depends on activity of cells■ Controlled by brain and brain stem by monitoring concentration of

CO2 in blood■ Higher levels stimulate nerve cells in brain■ Brain stem stimulates diaphragm to increase breathing rate and depth■ All happens subconsciously■ Holding your breath à you will pass out, then brain stem takes over,

normal breathing continues