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Chapter 23 Circulation
1) Intro
a) circulatory system
i)
system of internal transport
(1) oxygen, carbon dioxide, nutrients, waste products
of metabolism (CO2 to lungs, urea and other
waste to kidneys), hormones, body defense, temp.
regulation
ii) need if body is too big for chemicals to get to all
cells by diffusion alone
(1) diffusion good over only a few cells
iii) circulatory system must be intimate with tissues
(1) capillaries
(a)large blood vessels eventually flow into
capillaries
(b) tiny vessels (Fig. 23.1A) that form networks
among cells so no substance has to diffuse far
(i) every cell has a capillary at most a few cells
away
(2) interstitial fluid (“internal pond”) separates RBC
and tissue cell
(a)RBC to interstitial fluid (watery fluid) to tissue
cell
(b) tissue cell to interstitial fluid to RBC
2) Several types of internal transport systems have evolved
a) Cnidarians (Fig. 23.2A)
i)
ii)
have NO true circulatory system
use gastrovascular cavity as a “circulatory system”
iii) jelly fish
(1) elaborate GV cavity lined with flagellated cells, which
beat to circulate fluid
(2) all cells short distance from GV cavity
b) planaria (phylum platyhelminthes = flatworms)
i)
fresh-water non-parasitic flatworms
ii) flat and thin
iii) also has a GV cavity
iv) GV cavities will not work for thick, multiple layers of
cells
c) True circulatory system
i)
contains specialized circulatory fluid = Blood
d) Two basic circulatory systems have evolved
i)
open circulatory system
(1) many invertebrates
(a)mollusks (phylum containing snails and clams to
squids and octopus) and all arthropods
(2) open ended vessels
(3) blood and interstitial fluid are the same
(a)grasshopper
(i) tubular heart
(ii) contractions of body muscles move fluid toward
tail
(iii)heart relaxes and blood enters heart through pores
(iv) valves close over pores upon contraction
1. prevents backflow
(v) reminder – not used to deliver gases, tracheal
system does this.
ii) Closed circulatory system (vertebrates)
(1) a.k.a cardiovascular system
(a)cardio = heart
(b) vas = vessel
(2) blood confined to vessels
(a)separate from interstitial fluid
(3) 3 kinds of vessels
(a)arteries
carry blood away from heart (both start with “a”)
(b) veins
(i) carry blood toward heart
(c)capillaries
(i) connect arteries and veins within organs
(4) Fish (Fig. 23.2C – red = oxygenated blood, blue =
oxygen-poor blood)
(a) heart
(i) two main chambers
1. atrium
a. receives blood from veins
2. ventricle
a. pumps blood to gills via arteries
(b) ventricle -> artery -> gill capillary -> artery ->
arteriole (small vessels leading to capillaries) ->
capillary beds (network of capillaries in every organ
and tissue called systemic capillaries) -> venules ->
veins -> atrium -> repeat
(5) Evolution
(a)gills to lungs
(b) fish cardiovas compared to mammal cardiovas. (Fig
23.3)
(i) fish
1. single circuit of flow
2. heart always see oxygen poor blood
3. blood slows in capillaries and is helped along
by swimming movements of fish
(ii) mammals
1. more vigorous flow
2. four chamber heart
a. two atria
b. two ventricles
3. hearts are drawn as if in a person facing you
(i)
dual blood circuit
a. pulmonary circuit
i. carries blood b/w heart and lungs
ii. drops off CO2 and picks up O2
b. systemic circuit
i. carries blood from heart to rest of body
ii. delivers oxygen to body tissue and carries
back CO2
5. result: right side handles oxygen poor and left
side oxygen rich blood only
6. right atrium received blood from body tissues
a. RA -> RV -> lungs -> LA -> LV -> body ->
7. heart is two pumps in one
a. right to lungs and left to body at same time
keeping high flow
b. endotherms – need rapid O2 delivery (birds
and mammals)
i. endotherms use 10X energy of same size
ectotherms
ii. circ. system needs to deliver 10X more
fuel and oxygen
(6) The human heart and CV system
(a)heart (Fig. 23.4A) size of clenched fist
(b) enclosed in sac under breast bone
(c) mostly cardiac muscle tissue
(i) atria – thin walled
(ii) ventricles – thick walled
(iii)valves – regulate direction of flow in heart
1. mitral valve – LA to LV
2. aortic valve – LV to aorta
3. tricuspid valve – RA to RV
4. pulmonary valve – RV to pulm. artery
(d) Flow of blood through CV (Fig. 23.4B)
(i) RV to lungs via pulmonary arteries
1. pulmonary = lungs
4.
(ii) O2
and CO2 exchange in lung capillaries
(iii)lungs to LA via pulmonary veins
(iv) LA to LV
1. LV walls thicker that RV walls…explain
(v) LV to aorta
1. aorta = largest blood vessel (2.5cm diameter –
a quarter)
(vi) arteries branch from aorta to head and arms
(vii)
aorta heads south and arteries branch to
abdominal organs and legs
(viii)
arteries to arterioles to capillary beds to
venules to veins
(ix) upper body, veins to superior vena cava
(x) lower body, veins to inferior vena cava
(xi) SVC and IFV empty into RA
(xii)
RA to RV
(e) bottom line: heart to lung capillaries to heart to body
capillaries to heart
(f) be able to follow a blood cell
(7) Structure of the blood vessels fits function
(a) capillaries
(i) thin walls of course for diffusion
(ii) simple (single layer) epithelium wrapped in thin
basement membrane (loose connective tissue)
(iii)smooth surface – don’t want to damage blood cels
as they SQUEEZE through
(b) arteries, arterioles, veins, venules
(i) thicker walls than capillaries
(ii) same epithelium
(iii)smooth muscle layer – thicker in arteries
1. allows for blood flow regulation
a. Ex. Constricts in hands/feet when your
nervous to keep blood near major organs
2. gives strength to arteries near heart to
withstand surge from pump
(iv) outer
layer of connective tissue
1. elastic for stretch and recoil
(c)many veins have valves
(i) prevent backflow in veins
(8) heart contracts ad relaxes rhythmically
(a)cardiac cycle – complete sequence of filling and
pumping (0.8 sec)
(b) two phases of cardiac cycle (Fig. 23.6)
(i) diastole
1. heart relaxed
2. blood flows into all chambers
3. AV valves are open
4. lasts .4 sec, enough for V to fill
(ii) systole
1. begins with .1 sec contraction of atria
a. completely fills ventricles
2. ventricles then contract (0.3 sec)
a. force closes AV valves
b. opens SL valves
c. blood flow into atria
(c)cardiac output
(i) volume of blood per beat by LV times heart rate
(ii) 75 ml for average person x 70bpm = 5.25L/min
(d) heart sounds caused by closing of valves (lub-dup_
(i) lub = AV valves closing
(ii) dub = SL valves closing
(e)heart murmur
(i) sounds like a hiss
1. caused by stream of blood squirting backward
through valve
(ii) can be born with it or infection causes it
(iii)most valve defects do not reduce efficiency
enough to warrant surgery
(9) The Hearts Pacemaker
(a)Sinoatrial (SA) node = pacemaker
maintains pumping rhythm by setting muscle
contraction rate
(ii) Location
1. right atrium
(iii)generates electrical signals
1. spreads through both atria – simultaneous
contraction
2. signal reaches AV node
(b) AV node
(i) location: b/w RA and RV
(ii) signal delayed .1 sec
1. gives atria time to empty to ventricle
(iii) purkinje fibers
1. specialized muscle fibers
2. carry signal to ventricles triggering contraction
(c)electrical signal in heart generate elec. sig. in skin
(i) ECG – electrocardiogram
(d) Failure of the heart’s pacemaker
(i) artificial pacemaker
1. tiny electronic device inserted near AV node
(e)heart natural pacemaker has a default rate of 40-60
bpm
(i) brain talks to SA node and speeds it up
(10) Heart Attack
(a)coronary arteries
(i) branch off aorta to heart
(ii) what happens if one or more get blocked?
1. no oxygen, no ATP, cells become disordered,
die = heart attack
rd
(b) 1/3 die almost immediately
(c)survivors
(i) ability to pump blood is impaired
(ii) cardiac cells don’t do mitosis
1. can’t replace dead cells
2. scar tissue covers damage
(i)
a. cant contract
(d) cardiovascular disease
(i) disease of heart and blood vessels
1. heart attacks
2. strokes – brain tissue dies when arteries in head
are blocked
(ii) heart attack - leading cause of death in US
(iii)stroke – third leading cause
(iv) 40% of deaths in US are cardiovascular
1. 1 million per year or one every 30 seconds
(e)most HA and stroke victims had artherosclerosis
(i) chronic CV disease
(ii) plaques develop on inner walls of arteries
(iii)blood clot more likely to get trapped now
(iv) plaques are a site of clot formation
(f) How to minimize your risk
(i) smoking doubles risk of heart attack
(ii) exercise can cut it in half
(iii)diet low in cholesterol and sat. fat
(g) Treatment for artheriosclerosis
(i) drugs to lower cholesterol
(ii) angioplasty
(iii)stents
(iv) bypass surgery
1. blood vessel from legs put in heart to bypass
clog
(11) Blood pressure
(a)force that blood exerts against walls of vessels
(b) caused by pumping of heart
(c) drives blood through system
(d) ventricles push blood into arteries faster than they
can flow into capillaries
(i) result – elastic walls of arteries stretch
1. feel when you take pulse
a. pulse = rhythmic stretching of arteries
(e)systolic
pressure
(i) pressure caused by ventricles pumping
(f) diastolic pressure
(i) when elastic arteries bounces back b/w heartbeats
1. maintains pressure and flow b/w beats
(g) blood pressure depends on
(i) cardiac output
(ii) narrow opening of arterioles
1. controlled by smooth muscle
a. relaxed – blood flow easier and blood
pressure drops
b. contract – reduce flow, increase pressure
(12) Measuring blood pressure
(a) “blood pressure”
(i) usually refers to pressure on artery walls
(ii) typical BP = 120/80
1. units in mm Hg (120mm Hg/ 80mm Hg)
a. how tall a column of mercury the pressure
could support
2. first number (120 in this case) = systolic
pressure
a. force during contractions (systole)
3. second number(80 in this case)=diastolic
pressure
a. force during heart relaxation
(iii) indicator of CV health
(iv) sphygmomanometer – blood pressure cuff
1. used to measure BP
2. procedure
a. put cuff around brachial artery
b. inflate cuff until you cut off blood flow to
upper arm
i. no flow = no pulse below cuff
c. gradually release pressure from cuff
d. first sound of blood squirting through artery
is the systolic pressure (force of heart is
slightly stronger than pressure of cuff)
e. blood still can’t flow when heart is NOT
pumping so you hear the squirting with
every beat
f. continue to decrease cuff pressure
g. when blood flow squirt sound goes away =
blood always flowing = diastolic pressure
i. pressure of cuff not high enough to stop
flow even when heart is at rest – flow of
arteries rebounding
(b) “normal” blood pressure falls in a range
(i) genetic variation
(ii) optimal for adults in 120/80 or below 120 and
below 80
(iii)low values thought to be better unless they are
caused by a condition like internal bleeding…
(c) hypertension
(i) high blood pressure
(ii) persistent systolic above 140 and/or diastolic
above 90
(iii)affects 1/4th of population
(iv) “silent killer” – no obvious signs of having it for
years – killing you silently
(v) adverse affects
1. heart must work harder
a. heart becomes enlarged and weakened
2. increased risk of HA, heart disease, stroke,
kidney failure
3. cause tiny ruptures on arterial walls
a. promotes plaque formation (arteriosclerosis)
b. reduces elasticity
c. increased blood clot risk
(vi) risk factors
sex, race, age, gender
a. males higher risk to 55
b. females higher risk after 75
c. African Americans more prone than
Caucasians
d. increases with age
e. genetic
2. controlling hypertension
a. diet
b. avoiding excess alcohol
c. exercise
d. maintaining proper weight
e. medication (antihypertensive meds)
(13) Smooth muscle controls blood distribution
(a) regulate distribution of blood to capillaries (Fig
23.11)
(b) only 5-10% of capillaries have blood flowing at any
given time
(i) each tissue has MANY capillaries so everyone is
getting blood
(ii) some organs almost always carry a full load
1. brain, heart, liver, kidneys
(c)Two methods of control
(i) smooth muscles of arterioles constrict to control
flow to entire capillary bed
(ii) within capillary bed
1. thoroughfare channel
a. direct path from arteriole to venule
b. always open
2. precapillary sphincters
a. control flow to capillaries that branch off
thoroughfare channel
(d) Predict what would happen in blood capillary beds
of the digestive tract before and after eating.
1.
(e)What
about during exercise? In which tissue subtype
would precapillary sphincters be open?
(f) controlled by nerves and hormones
(14) capillaries allow the transfer of substances through
their walls
(a) capillaries
(i) only blood vessels with thin enough walls for
substances to cross and enter IF
(b) Fig 23.12 – cross section of skeletal capillary
(i) capillary wall (tan) is two epithelial cells that
form a tube
(ii) lumen – inner space just large enough for a RBC
to pass in single file
(c)exchange b/w blood and IF
(i) diffusion through membranes of epithelial cells
1. oxygen, CO2
(ii) endocytosis/exocytosis
1. from lumen to IF by epithelial cells
2. larger substances
(iii) leaky - narrow clefts b/w epithelial cells
1. diffusion
a. water and small solutes like glucose, salts,
etc…
b. blood cells and proteins stay in blood (too
large)
2. active forces (pressures)
a. blood pressure pushes fluid out through
clefts
b. osmotic pressure – draws fluid in because
blood has a higher concentration of solutes
than IF
c. therefore, directions of movment through
clefts depends on difference b/w blood
pressure and osmotic pressure
i. arteriole side of capillary – BP > OP –
more fluid moves out than in
ii. venule side – OP > BP – more fluid
moves in than out
iii. any net fluid remaining is returned to
blood by lymph system
(15) Blood – cells suspended in plasma
(a) structure and function of heart and vessels should be
apparent at this point
(b) time to look at the blood itself
(c) 4 to 6 liters of blood
(d) Two components (centrifuge to separate them)
(i) plasma component – 55%
1. liquid part
a. water (90%), salts, plasma proteins,
substances transported by blood (Figure
23.13)
b. some proteins and salts maintain osmotic
balance and pH of 7.4
c. some proteins have specific function
i. fibrinogen – blood clotting
2. know the functions
(ii) cellular component – 45%
1. RBCs, WBCs, Platelets
a. know their functions
(16) Red Blood Cells (RBCs) = erythrocytes
(a) most numerous of blood cells
(b) 25 billion in blood (book says 25 trillion – this is a
mistake)
(c) lack nuclei and mitochondria
(i) lost as cell develops in bone marrow
(ii) allows more room for hemoglobin
(d) structure function
(i) small, biconcave disks
1. large surface area for O2 to diffuse
250 million hemoglobins per cell
(e) site of formation
(i) bone marrow
1. large bones (pelvis, sternum, ribs, vertebrae,
ends of upper arm (humerus) and leg (femur))
(ii) controlled by negative feedback
1. not enough O2 at tissues
2. kidneys produce erythropoietin (EPO)
3. EPO stimulates bone marrow to make more
RBC’s
4. too much O2
5. EPO production decreases
a. O2 is the heat and EPO is the thermostat
b. heat gets too high and thermostat shuts off
(iii)patients on kidney dialysis don’t make enough
EPO typically
1. genetically engineered EPO
a. abused by athletes…be able to explain why.
i. dehydration during a race combined with
increased # of RBC’s causes blood to
become a sludge. – clotting, stroke, heart
failure and death have occurred.
(f) life span
(i) 3 to 4 months (~120 days in the blood)
(ii) worn out RBCs are broken down and recycled in
liver
(iii)most of iron returned to bone marrow
(g) anemia
(i) low amount of hemoglobin (iron etc…) or red
blood cells
(ii) feel tired, run down, susceptible to infection
1. body cells not getting enough O2
(iii)can result from
1. excessive blood loss
2. vitamin or mineral deficiencies
2.
bone marrow cancer
(iv) iron deficiency is most common cause
1. more likely in women during blood loss during
menstruation
2. pregnant women – take iron supplements
usually
3.
(17) White blood cells (WBC’s) or leukocyctes
(a)help
defend the body
(i) fight infections
(ii) prevent cancer cells from growing
(b) five kinds (23.15) – can be distinguished by staining
properties (how they stain when looked at under
microscope) and shape of nucleus.
(i) basophil
(ii) neutrophil
(iii)eosinophil
(iv) monocyte
(v) lymphocyte
(c)basophil
(i) releases histamine
1. histamine dilates blood vessels
2. allows other WBCs to leave capillary and enter
site of infection
(d) neutrophils and monocytes
(i) both are phagocytes – “eat” bacteria, foreign
proteins, debris from dead body cells
(e)eosinophils
(i) not a lot known
(ii) kill parasitic worms
(iii)may help reduce allergy attacks
(f) lymphocyts
(i) key cell in immunity
(ii) Two types
1. B-cells
a. produce anitbodies
2. T-cells
a. attack pathogen infected body cells and
cancer cells
(g) Most spend their time outside blood stream in the IF
where the battles are waged
(h) many found in lymphatic system
(i) site of formation
(i) bone marrow
(ii) numbers increase when body is fighting infection
(18) Blood clotting
plugging leaks in the vessels
(b) the sealants (glue)
(i) platelets and fibrinogen
(ii) Always present in blood
(iii)activated when the vessel is injured
(c)stages of clotting (Figure 23.16A)
(i) epithelial lining damaged
(ii) connective tissue exposed
(iii) platelets stick to connective tissue
1. release chemicals to make other platelets sticky
(iv) platelets plug break
1. fast protection against blood loss
2. that might be it for tiny wounds (pinprick)
3. more severe wounds needs a fibrin clot
4. continue to step v for more severe wounds
(v) clotting factors (proteins) released by platelets
and damaged cells – mix with clotting factors in
blood plasma
(vi) prothrombin activated to thrombin
(vii)
thrombin activates fibrinogen to fibrin
(viii)
fibrin – threadlike protein
(ix) threads trap RBC’s
1. fibrin is like spiderman’s web (Fig. 23.16B)
(a)
hemophilia
(i) inherited (genetic) disease
(e)thrombus
(i) blood clot formation in absence of injury
(ii) if thrombus breaks off and lodges in coronary
artery of artery of brain, heart attack or stroke will
occur.
(19) hematopoietic stem cells (type of adult stem cell)
(a) found in red marrow of ribs, vertebrae, breast bone,
pelvis
(b) can differentiate into RBC’s, WBC’s and cells that
produce platelets
(c)leukemia
(i) cancer of the white blood cells
(ii) overabundance displaces normal bone marrow
cells that make blood cells
1. causes anemia and impaired clotting
(iii)fatal if not treated
1. radiation and chemotherapy
2. bone marrow transplant (donor)
a. life long treatment of anti-rejection
medication
3. bone marrow transplant (self)
a. remove marrow, processed to remove cancer
cells, reimplant
4. Stem cells – rare: 1 in several 1000 marrow
cells
a. injecting 30 could repopulate blood and
immune system!!
b. three methods
i. oldest – marrow harvested with a largebore needle from pelvis bone (Fig. 23.17)
- invasive and painful, but many stem
cells
(d)
ii. use drugs to draw out stem cells into
blood
iii. placental and umbilical cord blood – grab
at birth and store for future