BSC 250-Exam IV Notes

8/10/2019 BSC 250-Exam IV Notes

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Immunity

Learning Outcomes:

1. Defne immunity, specifcity, versatility, memory, and tolerance.

2. Defne antigen and hapten. Distinguish between a oreign antigen andsel antigen.!. Defne antigenic determinant.

". List the types o #$% molecules and the types o cells that display each.

&. 'hat is costimulation( 'hat are the types o %D mar)ers and which cellsdisplay each(

*. + plain the unction o the #$% molecules and how they activatelymphocytes(

-. Distinguish between antibody mediated and cell mediated immunity.

/. 'hat types o lymphocytes unction in cell mediated immunity( List theunctions o each.

0. 'hat types o lymphocytes unction in antibody mediated immunity( Listthe unctions o each.

1 . Defne antibody. List and describe the e ects o antibodies.

11. List and describe the di erent ways that adaptive immunity can beac3uired.

4daptive immunity characteristics

increase in speed and strength to each attack " main properties o immunity: Specificity:

WBCs attack certain targets (lymphocytes) the ability of adaptive immunity to recognize a particular substance

Versatility: emory:

once infected the first time! body remembers it to attack stronger the ability of adaptive immunity to "remember# previous encounters $ith a

particular substance% &s a result! the response is faster! stronger! and longer'lasting

olerance: defense cells recognize self'cells and not self cells recognizes healthy self cells vs unhealthy self cells


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failure of the specific immune system to respond to an antigen produced by the deletion of self'reactive cells! by the prevention of lymphocyte

activation! and by the activation of suppressor cellsImmune system protects rom:

% invading pathogens*% our o$n unhealty cells

5igure 22.2: %ells o 4daptive Immunity

B cell: after activation! differentiates to become plasma or memory B cells+lasma cell: produces antibodies that are directly or indirectly responsible fordestroying the antigen

emory B cell: ,uick and effective response to an antigen against $hich the immunesystem has previously reacted- responsible for adaptive immunity

Cytoto.ic cell: responsible for destroying cells by lysis or by producing cytokines/elper cell: activates B cells and effector cellsSuppressor cell: inhibits B cells and effector cells

emory cell: ,uick and effective response to an antigen against $hich the immunesystem has previously reacted- responsible for adaptive immunity 0endritic cell: processes antigen and is involved in the activation of B cells and cells

6ubdivisions o adaptive immunity:

&ntibody'mediated immunity: involves 7 lymphocytes:

give rise to antibodies t kill infected cell responds to e.tracellular antigens in the body fluids'humeral immunity (body

fluids) Cell'mediated immunity:

involves 8 lymphocytes : destroys abnormal or non'self cells

come in contact $ith unhealthy cells and kills them responds to intracellular antigens cells destroying other cells

Origin and development o lymphocytes lymphocytes are derived from lymphoid stem cells


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pre't cells: migrate from the bone marro$ to thymus $here some $ill matureinto cells

B cells mature in the bone marro$

Location o Lymphocytes primary lymphatic organs1 tissues: $here lymphocytes mature into functional

cells- red bone marro$ and thymus secondary lymphatic organs1tissues:lymphocytes interact $ith each other!

antigen'presenting cells! and antigens to produce an immune response- lymphaticnodules! lymph nodes! and spleen

4ntigens 9antibody generators substances that are recognized as foreign and provoke an immune response

(activation of B cells or cells) self antigens: molecules produced by the body that stimulate an immune

response (may be beneficial or harmful) foreign antigens: not produced by the body but are introduced from outside!

inhaled! eaten! etc% complete antigens have t$o functional properties %hemical nature o antigens

a% large! comple.! usually proteins b% antigenic determinants (epitope): region of antigen recognized by lymphocytes

a% specific part of the antigen to $hich the lymphocyte responds b% combines $ith the antigen receptor ( cell receptor or B cell receptor)c% large molecules may have more than one to stimulate more lymphocytes

c% contain certain regions that are recognized by the lymphocytes and cause theimmune response: epitopes or antigenic determinants

d% an antigen usually has many epitopes! each of $hich induces production ofspecific antibodies or activates a type of cell

e% haptens: smaller substances that have reactivity but no immunogenicity- causesimmune response only $hen attached to larger carrier- usually associated $ithallergic reaction

f% antibodies or lymphocytes $ill bind to the epitopes

#a;or $istocompatibility %omple 9#$% 4ntigens #$%s genes, produce proteins $L4 9human leu)ocyte antigen

#$%s


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most cells have "self antigens# at plasma membrane surface- integral membrane glycoproteins found on the plasma membranes of most of the body2s cells 3ach has a region that can bind to foreign and self'antigens because the immune system cannot respond to an antigen inside a cell! these

molecules display antigens produced or processed inside the cell on the cell2ssurface

self antigens on the surface of membranes of most cells'identifiers tells condition of the cell'healthy vs unhealthy

#$% class I molecules : display antigens on the surface of nucleated cells! resulting in the destruction of the

cells

found on &44 nucleated cells display proteins produced inside the cell can bind to cell receptors that signals the activation of cells! $ho then destroy

infected cells "red flags#: promote the immune system to destroy the cell that basically displays a

sign that says "kill me#a% most body cells have 5self antigens5 at plasma membrane surface- integral

membrane b% each individual $ill have uni,ue /C antigens

c% transplant success depends on similarity bet$een the /C antigens of therecipient and donord% $ithin the /C antigen is a peptide binding groove- during breakdo$n of

proteins $ithin a cell! peptides can become associated $ith ne$ly synthesized/C- if peptide is recognized as self! cell ignores it- if peptide is recognized as

foreign! immune responsee% e.ogenous antigens: outside of the cell- engulfed by a special class of cell: antigen

presenting cells- antigen becomes incorporated in the /C of the &+C- &+Cmigrates to lymph nodes and presents to the cells to alert of intruders

4ntigen processing as ne$ /C proteins are made in the cell and transported to the cell membrane!

particles of intercellular proteins are associated $ith the /C this acts as a signal for intracellular "activity# foreign antigens inside the cell $ill trigger an immune response if it is a mutant antigen! there $ill be an immune response


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5igure 22.1& #$% class I molecules :

%*%

6%7%8%9%

#$% class II molecules :

%*%6%

7%&.

#$% class II molecules display antigens on the surface of antigen'presenting cells! resulting in the

activation of immune cells found on antigen presenting cells (&+Cs):

include B cells! macrophages! monocytes! and dendritic cells

stimulate the proliferation of helper cells! $hich stimulate the proliferation of Bcells or effector cells "tattle tale cells# normal'no immune response! damaged'immune response engulf material by endocytosis! process the material and incorporate some of the

molecules into the /C molecule may stimulate the activation of lymphocytes

8ypes o #$% proteins: Class /C: located on all nucleated cells- Class /C: located on membranes of antigen'presenting cells and

lymphocytes

%ostimulation : other signals besides the /Cs are necessary to activate lymphocytes


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an additional stimulations by cytokines or molecules on the cell surface to helpcreate a response by bonding these molecules

costimulation by sur ace molecule : if cells have the appropriate molecules ontheir surface! some cells $ill create a response by bonding these molecules

C0 ("cluster of differentiation#) markers: C06 markers:

on all lymphocytes (general! on all nucleated cells)

C0; markers: on some t cells: interact $ith /C (general) on cytoto.ic cells and suppressor cells- interact $ith Class /C

C07 markers: on helper cells- interact $ith Class /C (specialized)

%ell #ediated Immune =esponse : cell involves cells'similar to


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directly involved in cell immunity recognize and destroy pathogens

helper cells : coordinate both cells and B cells- release lymphokines coordinate both immune cells and non'specific defenses- also activates B cells target of / V

/ V: targets C07 cells suppressor cells: defined by ability to suppress immune responses

depress the activity of cells and B cells after antigen is inactivated ordestroyed

numbers increase! levels of cells and B cells decrease

4ntibody #ediated Immune =esponse involves B cells'involved in e.tracellular fluid and attacking there antibodies

released into fluid cell to cell interaction B cells $ill divide and give rise to cells that produce antibodies

plasma cells: B cells $hen they start producing antibodies B cells become sensitized $hen antigens that are specific to the receptors are

present B cells become activated $hen helper cells bind to them- causes B cells to divide

and differentiate into memory B cells or plasma cells (secrete antibodies)

4ntibodies : proteins produced in response to antigens! immunoglobulins ( g)! or gamma

chains composed of 7 polypeptide chains: * identical heavy chains and * identical light

chains 8wo regions o antibody:

variable region: combines $ith antigenic determinant 9epitope constant region: region responsible for activities of antibody (activates complement

or binds to cells) 5ive classes o antibodies

g>:


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most divers group activates complement and promotes phagocytosis can cross the placenta and provide immune protection to the fetus and ne$born responsible for ?h factor

g&: secreted into saliva! into tears! and onto mucous membranes to provide

protection on body surfaces provides protection on body surfaces found in colostrum and milk to provide protection to ne$borns

g : usually first antibody produced in response to antigen responsible for transfusion reactions in the &B@ blood group system

g3: binds to mast cells and basophils and stimulates the inflammatory response

g0: Aunctions as antigen'binding receptors on B cells

4ctions o antibodies neutralize the antigen precipitation and agglutination

"precipitation# causes antigens to "fall out# of solution or group together

activate complement proteins bind to the antigen and interfere $ith antigen activity or bind antigens together attract phagocytes initiate inflammatory response opsonization:

can act as "opsonins!# substances that make an antigen more susceptible tophagocytosis! by binding to the antigen and macrophage increases speed of phagocytosis "sugar# coated (easier to s$allo$)

4ntibody #ediated Immunity


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B cells "launch a chemical attack on antigens# $hen B cells come in contact $ith appropriate antigen! it becomes sensitized

B cells usually re,uire interaction $ith helper cells before becoming activated &ctivated B cells divide and give rise to:

memory B cells: faster and less steps plasma cells: B cells that produce antibodies

Immune =esponse +rimary response:

action of lymphocytes follo$ing initial encounter $ith appropriate antigen $hen body is first e.posed to antigen! has a lag phase because B cells must be

activated and differentiate Secondary (memory) response :

immune system is e.posed to an antigen against $hich it has already produced aprimary response

response is faster and greater faster! more prolonged and more effective because the system is primed- memory

cells are on alert

4c3uired 4daptive Immunity:

&daptive immunity can be ac,uired naturally or artificially &daptive immunity can be ac,uired actively or passively active immunity:

immunity is provided by the individuals o$n immune system natual active: antigens are introduced through natural e.posure artificial active: antigens are deliberately introduced in a vaccine

passive immunity: immunity is transferred from another person or an animal

natural passive: antibodies from the mother are transferred to her child acrossthe placenta or in milk

artificial passive: antibodies produced by another person or an animal arein ected

ac3uired adaptive immunity


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active immunity passive immunity naturalD artificialD naturalD artificialD

Immunity Disorders mmunodeficiencies: abnormal functions of immune cells &utoimmune 0isease: immune system loses ability to distinguish self cells from

foreign cells

%hapter 2 : 8he $eart

Learning Outcomes:1. List the unctions o the heart.

2. Describe the structure and unction o the pericardium.

!. Describe the histology o the heart wall.

". >ame the chambers o the heart and describe their structure.

&. Describe the blood ?ow through the heart including the vessels thatempty into and drain the heart chambers.

*. Describe the openings o the atria and ventricles.

-. List and describe the unctions o the heart valves.

/. %ompare and contrast cardiac and s)eletal muscle.

0. + plain the role o gap ;unctions and intercalated dis)s in cardiac muscleunction.

1 . List the parts o the conducting system and trace an electrical impulsethrough the conducting system.


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11. Describe ion movement during depolari@ation, plateau, andrepolari@ation phases o the cardiac action potential.

12. + plain why cardiac muscle cells do now show tetany.

1!. Defne systole and diastole.

1". List the phases o the cardiac cycle describing the movement o bloodthrough the heart and the position 9open or closed o the di erent valves.

1&. 'hat is cardiac output( $ow do stro)e volume, end diastolic volume,end systolic volume relate to each other and cardiac output(

1*. Defne preload and a terload.

1-. Describe the neural regulation o the heart.

5unctions o the heart generating blood pressure separating pulmonary and systemic circulation

pulmonary systemic

maintaining one'$ay flo$ of blood regulating blood supply

A8he heart is located within the mediastinum within the pericardial cavity.B

8he pericardium 5unction:

reduces friction of the heart 6tructure:

fibrous pericardium: outer covering! also called the pericardial sac outer covering

anchors heart in place a double $alled sac

parietal pericardium lines the inner surface of the sac epicardium: visceral pericardium- covers the heart- parietal and visceral pericardium are parts of the serous membrane that secretes

pericardial fluid


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pericardial fluid fills the pericardial cavity

8he heart is a our chambered organ : $o atria: superior chambers! receiving chambers $o ventricles: inferior chambers! pumping chambers Internal partitions separate the le t chambers rom the right chambers:

interatrial septum: interventricular septum:

8he walls o the heart are composed o three layers 3picardium: outer layer! serous membrane yocardium: bulk of the heart- mostly cardiac muscle 3ndocardium: inner layer! epithelial cells lining the chambers and heart valves

4tria receiving chambers of the heart $ith minimal contraction! the atria push blood to ventricles relatively small! thin $alled $hen empty! atria have $rinkled flap: auricle : e.pandable portion of the atria pectinate muscles: ridges of muscles on the inner $all of the atria fossa ovalis: depression on the interatrial septum foramen ovale: an opening bet$een the right and left atria in the embryo and

fetus

Centricles pumping chambers of the heart right ventricle pumps blood into pulmonary trunk to the lungs left ventricle pumps blood into aorta to the systems of the body internal $alls of the ventricles have irregular muscle ridges papillary bundles: are stalk'like muscle bundles in the ventricles that are

important for heart valve function-=ight 4trium ?ecieves deo.ygenated blood from inferior and superior vena cava and coronary

sinus


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blood enters through three veins

% superior vena cava*% inferior vena cava6% coronary sinus

Le t 4trium ?eceives o.ygenated blood from four pulmonary veins:

$eart Calves : maintain one'$ay flo$ of blood through the heart (vein'atrium'ventricle'artery) open and close depending on the blood pressure on either side chordae tendinee: anchor cusps of valves to the papillary bundles 8wo pairs o valves :

&trioventricular valves:located bet$een the atrium and ventricleprevent backflo$ of blood during ventricular contraction

right &V: tricuspidleft &V: bicuspid or mitral

Semilunar valves:located bet$een the ventricle and arteryprevent backflo$ of blood from vessel to ventricles

pulmonary semilunar: guards the entrance to the pulmonary trunk aortic semilunar: guards the entrance to the aorta

Eathway o blood through heart $o pumps serving * circuits:

% pulmonary circuit:*% systemic circuit:

@.ygen poor blood enters the right atrium via the vena cavae Blood flo$s from the right atrium to the right ventricle through the tricuspid

(&V) valve ?ight ventricle contracts pushing blood into the pulmonary trunk (artery)

through the pulmonary semilunar valve Blood flo$s to the lungs $here it becomes o.ygenated @.ygen rich blood enters the left atrium via the four pulmonary veins


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Blood flo$s from the left atrium to the left ventricle through the mitral (&V) valve 4eft ventricle contracts pushing blood into the aorta through the aortic semilunar

valve

F%ardiac #uscle 8issueG characteristics o cardiac muscle fbers

striatedelongated! branching cells that have one or t$o nucleicontracts similar to skeletal muscle (sliding filament)short! fat! branched! interconnectedad acent cells interconnected at intercalated disc: contain desmosomes and gap unctions

intercalated disks: specialized cell'to'cell attachment $ith gap unctions bet$een cardiac muscle cellsdesmosomes: specialized plasma membrane structures that hold cellstogethergap unctions : allo$ cytoplasm to flo$ freely bet$een cells! resulting inareas of lo$ electrical resistance bet$een the cells

the myocardium acts as a syncytium (multi'nucleated)

/eartbeat: coordinated contraction of the entire heart- pattern of cell contractioninsures that the blood flo$s in the correct direction

'ithin the myocardium, there are two types o cells, each with a distinctunction

% contractile cells: produce the contraction- form the bulk of the myocardium(EEF)

*% cells of the conducting system: control and coordinate the contractile cell activityand stimulate contractile cells

%onducting 6ystem :smaller cellshave fe$er myofibrilsuni,ue muscle cells that contract on their o$n

autorhythmicity : depolarize $ithout neural stimulation0@


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initiate and distribute the stimulus for contraction by initiating and distributingelectrical impulses through the myocardium

Earts o the %onducting 6ystem : (kno$ orderG)

sinoatrial node (S& node): pacemaker of the heartatrioventricular node (&V node): located at the unction bet$een the atria and ventricles &V bundle:

a conducting bundle of the heartpasses through a small opening in fibrous skeleton to reach theinterventricular septum! $here it divides to form branches

Bundle Branches: e.tend beneath endocardium on each side of theinterventricular septum to the ape. of both the right and the left ventricles

+urkin e fibers: spread through the ventricular systemthe inferior terminal branches of the bundle brancheslarge'diameter cardiac muscle fibersmodified cardiac muscle cells found beneath the endocardium of the ventriclesspecialized to conduct action potentialshave fe$er myofibrils than most cardiac muscle cellsdo not contact as forcefully

Acompare to a tube o toothpaste: start rom the bottom and wor) your wayupB

8he cells o the conducting system : conducting cells : connect the t$o nodes and distribute the contractile stimulus

throughout the myocardium- include the cells of the internodal path$ay! &V bundle! bundle branches and +urkin e fibers

smaller than the contractile cellshave fe$ myofibrilscan not maintain a stable resting potential- gradual depolarize causing actionpotential propogation

5igure 2 .1!: %onducting 6ystems o the $eart

% &ction potentials originate in the S& node and travel across the $all of the atriumfrom the S& node to the &V node%

*% &ction potentials pass through the &V node and along the &V bundle! $hiche.tends from the &V node! through the fibrous skeleton! into the interventricularseptum%


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6% he &V bundle divides into right and left bundle branches! and action potentialsdescend to the ape. of each ventricle along the bundle branches%

7% &ction potentials are carried by the +urkin e fibers from the bundle branches tothe ventricular $alls and papillary muscles%

#embrane Eotentials electrical charge across plasma membrane of cell result of uneven distribution of ions across the membrane changes in membrane potential result in changes in cell activity resting potential:

membrane potential of an undisturbed cell depends o a lo$ permeability of the plasma membrane to


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% &n &+ is initiated $ithin the S& node*% he &+ travels through the atrial $all via the internodal path$ay to the &V node%

Stimulus is also passed to contractile cells of the atria6% &+ reaches the &V node $here the impulse lags before moving along the

conducting system7% &+ travels to &V bundle entering the right and left bundle branches- impulse

travels to the ape. of the heart! turns and fans out to the +urkin e fibers8% +urkin e fibers distribute the impulse to the myocardium: ventricular contraction

occurs

Centricular contraction moves in a wave rom ape to base, pushing bloodtowards the base and into the great vessels

Damage to the conducting system will disrupt normal rhythm o the heartHdamage to the 64 node or internodal pathway will result in the 4C nodeacting as the pacema)er.

%ardiac #uscle %ontraction

Ventricular contractile cell: resting potential is 'EImV- threshold ( + that $ill causean action potential) is 'J8mV 6teps involved in the contraction o a cardiac muscle cell:

Step %D ?apid depolarization: membrane becomes permeable to


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voltage'gated CaH* channels remain open the movement of CaH* and some


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results from ventricular depolarization and signals the onset of ventricularcontraction

$ave: ventricular repolarizationrepresents repolarization of the ventricles and precedes ventricularrela.ation

%ardiac %ycle : period of time bet$een the start of one heartbeat and the beginning ofthe ne.t- period of contraction and rela.ation Systole: contraction- chamber pushes blood 0iastole: rela.ation- chamber fills $ith blood

A7lood ?ows rom an area o high pressure to an area o lower pressureB

8he %ardiac %ycle%4trial 6ystole:

atria contract pushing blood into ventricles through the &V valvesat the end of atrial systole! ventricles contain the ma.imum volume of blood forthat cycle: +nd Diastole Colume 9+DC

3nd 0iastolic Volume (30V):*. Centricular 6ystole

ventricles begin to contract- &V valves close

this step in the cardiac cycle is divided into t$o phase characterized by themovement of the bloodisovolumetric contraction: blood is not moving because all of the valves(&V and semilunar) are closed- eventually the pressure in the ventricles $ill be great enough to push open the semilunar valves ventricular e ection phase: once the semilunar valves open! blood ispushed into the great vessels

near the end of ventricular systole! semilunar valves closestroke volume: volume of blood e ected from the ventricles

3nd Systolic Volume (3SV): blood remaining in ventricles6% Centricular Diastole

ventricles rela.all valves are closed $alls of the ventricles e.pand rapidly decreasing the pressure $ithin the ventricles


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$hen the ventricle pressure is less than the atrial pressure! the &V valves $illopen- blood flo$s into the ventriclesall chambers are rela.ed

5igure 2 .1/: %ardiac %ycle

1. 6ystole: period o isovolumetric contraction2. 6ystole: period o e;ection

!. Diastole: active ventricular flling

". Diastole: period o isovolumetric rela ation

&. Diastole: passive ventricular flling

Cardiodynamics: movement and forces generated during cardiac contraction

%ardiac output : amount of blood pumped by each ventricle in one minute- C@ L SV . /?

SV: stroke volume: amount of blood pumped out of each ventricle during a single beat- SV L 30V'3SV/?: heart rate: number of times the heart beats per minute

Cardiac reserve: the difference bet$een cardiac output $hen a person is at rest and ma.imum

cardiac output resting C@ ' ma. C@

5actors controlling stro)e volume

% 30V filling time: dependent on heart rate venous system: stretching of S& node causes stimulus venous return: the amount of blood returning to the heart from the systemiccirculation- causes 30V increases during e.ercise

*% 3SV preload: degree of $hich the ventricular $alls are stretched

increased preload causes the cardiac muscle cells to contract $ith a greaterforce and produce a greater stroke volume

contractility: amount force produced during a contraction at a given preloadafterload: amount of tension ventricles must produce to force open the semilunar valves


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5actors a ecting heart rate : alter S& nodenervous system activityhormones

drugschanges in ion concentration body temperature

7lood Cessels

Learning Outcomes:

1. >ame, in order, all the types o blood vessels, starting at the heart, goinginto the tissues, and returning to the heart.

2. Describe the structure o a capillary.

!. >ame the three layers o tissue o a blood vessel wall.

5unction o circulatory system

1. carries blood


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2. e changes nutrients, waste products, and gases with tissues

!. transports substances

". helps regulate blood pressure

&. directs blood ?ow to tissues

+ulmonary Vessels: transport blood from the right ventricle! through the lungs! and back to the left atriumSystemic Vessels: transport blood through all parts of the body from the left ventricleand back to the right atrium

8ypes: arteries:

smaller lumen thicker $alls carries blood &W&M from heart

capillaries: smallest vessels $here e.change bet$een blood and tissue occurs

veins: thinner $alls larger lumen

carries blood to heart

7lood vessel wall is composed o three layers or tunics tunica intima:

innermost simple epithelium $ith underlying connective tissue cells packed tightly together lack of space bet$een cells provides the inside of veins $ith a smooth surface $hich

reduces resistance to blood flo$ tunica media:

middle layer smooth muscle

constricts or dialates vessel $hich regulates blood flo$ tunica e.terna:


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outermost collagen fibers (fibrous connective tissue)

anchoring vessels in place gives strength to vessel $all

ALarger vessels have vasa vasorum that provide nourishment to the cells othe vesselH located in the tunica e ternaB vasa vasorum:

4rteries : transport blood a$ay from the heart consist mainly of tunica interna

8hree types o arteries elastic arteries

largest in diameter most elastic pulmonary trunk and aorta ability to stretch and recoil smooth out large pressure fluctuations by e.panding and recoiling

uscular arteries "distributing arteries#: they insert into ma or organs deliver blood to organs have a thick tunica media (their primary layer is the muscle layer)

&rterioles determine flo$ and carry blood to capillary bed "feed capillaries# can constrict and1or dilate depending on the need of the tissues smallest arteries

%apillaries smallest blood vessel thin $alls of ust tunica intima site of e.change bet$een blood and interstitial fluids


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most tissues have rich capillary supply t$o types of capillaries: continuous and enestrated

continuous capillaries: make up a ma ority of the body2s capillaries has no gaps in its $all that separates the blood and surrounding tissue

fenestrated capillaries: modified capillaries "leaky capillaries# have pores (passage$ays through the cells) located in areas $ith a great rate of e.change (kidneys and some glands)

capillary beds: net$ork of capillaries $ithin tissue never a single capillary standing alone- al$ays tied into a net$ork or bed precapillary sphincter:

muscles that regulate blood flo$ through the bed constrict and1or rela. local regulators

thoroughfare channel:

Ceins collect blood from all tissues and organs and return it to heart thinner $alls and larger lumen smaller veins have valves to maintain the flo$ of blood to$ards the heart

8ypes o Ceins venule:

drain capillary bed smallest

medium veins: drain blood from organs

large veins: superior and inferior vena cava


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BSC 250-Exam IV Notes