Unit 3 - Cardiovascular

Question 1

heart function

Answer 1

transport!
- oxyen, nutrients, hormones to cells
- CO2 + other metabolic products from cells -> lungs, liver, kidneys
- heat to extremities

Question 2

cardiovascular made up of

Answer 2

1. circulatory system
   - heart
   - vessels
   - blood
2. arteries (away from heart)
3. veins (to heart)
4. lymphatics (tissue fluid AKA lymph to large veins)

Question 3

heart location

Answer 3

dog: rib 3-6
- 45 degree angle with sternum

cat: ribs 3/4-6/7
- more acute angle (more sternum contact)

horse: ribs 2-5
- apex at elbow.

bovine: os cordis within heart (2 bones separating atria + ventricle)

Question 4

heart layers

Answer 4

1. pericardium
   - thin fibro-serous heart covering
   - fibrous part outer
   - serous part inner
   a) parietal (in contact with fibrous)
   ~pericardial space (fluid) between~
   b) visceral (in contact with heart)
2. myocardium
   - muscle layer
3. endocardium
   - membrane on internal surface of heart

Question 5

heart chambers

Answer 5

each side has an:
1. atrium (receives blood from veins)
+ interatrial septum b/w R/L

~ atrio-ventricular valve in between~
~ leaflets preventing backflow

2. ventricle (pumps blood to arteries)
   + interventricular septum b/w R/L

RIGHT
right atrium:
- thin wall
- gets blood from systemic (everything but lungs) veins
- right auricle = blind portion

~right AV valve (tricuspid) between~
~ anchored to R ventricle through chordae tendinae connecting to RV’s papillary muscles

right ventricle:
- more muscular than atria
- thinner wall than L ventricle
- doesn’t reach apex
- blood goes R atrium -> R AV -> R ventricle

~pulmonary trunk drains RV~
~ blood leaves RV
~ pulmonary semilunar (3 cusp) valve at base of trunk

LEFT
left atrium:
- thin wall
- gets blood from pulmonary veins
- left auricle: blind portion

~left AV valve (mitral) between~
~ anchored to L ventricle through chordae tendinae connecting to LV’s papillary muscles

left ventricle:
- thickest wall
- connects to apex
- blood goes L atrium -> L AV -> LV

~ aortic semilunar valve~
~ separates LV from aorta
->
~ aorta~
~ blood leaves LV

Question 6

heart valves

Answer 6

• anchored by CT separating atria from ventricles
• one-way

AV valves:
- one side of leaflet attached to inner ventricle where it connects to atrium
- free edges loosely attached to V by chordae tendineae (prevent valve from flipping when Vs contract)
- leaflets pushed together from blood in V -> AV valve closes

semilunar:
- stop blood from returning into V when they relax

Question 7

tree branch

Answer 7

• arteries start large where they carry blood from heart -> smaller branches
  a) arterioles: smallest branch -> lead to capillaries

capillaries: one cell thick tubes for nutrient exchange
- selectively permeable
- take in water, O, nutrients
- pushes waste into the blood
- lymphs remove excess fluid from capillaries

venules:
- united capillaries that have passed through tissue
- then venules unite -> larger veins

vena cava:
- largest of veins
- empty into heart

Question 8

veins vs artieries

Answer 8

vein difference:
- larger
- thinner wall
- more superficial
- valves where 2+ veins meet to form a larger vein (prevent backflow)
- TO heart

Question 9

filtration

Answer 9

arterial end:
- blood forced into capillaries through hydrostatic pressure from heart
- but only water + small ions and nutrients get through

venule end:
- fluid reabsorbed, low hydrostatic pressure
- plasma proteins more concentrated, their osmotic pressure draws water in (this part of osmotic pressure = ‘oncotic pressure’)
- oncotic pressure: comes from molecules too large to escape capillaries

Question 10

edema

Answer 10

• excess tissue fluid
  from:
• leaky vessels
• high hydrostatic pressure (heart failure)
• low oncotic pressure (low albumin from GI disease or liver failure)

Question 11

blood flow path

Answer 11

L/R pulmonary veins -> L atrium -> L AV -> L ventricle -> aortic semilunar -> aorta ->

…. -> arteries -> arterioles-> capillaries -> tissue -> venules -> veins -> vena cava -> …..

R atrium -> R AV -> R ventricle -> pulmonary semilunar -> pulmonary trunk -> L/R pulmonary arteries

2 circulations:
1. systemic
- deoxygenated vein
2. pulmonary (lungs only)
- oxygenated vein

venous blood:
- veins -> heart
- unoxygenated

arterial blood:
- heart -> body
- oxygenated

Question 12

pulmonary circulation

Answer 12

• blood moving through lungs
• vast capillary network
• swap air in alveoli for CO2 in blood -> becomes oxygenated
• blood changes from dark red (no oxygen) to bright red
• ONLY place where there is unoxygenated blood in arteries + oxygenated in veins

PATH:
pulmonary trunk -> pulmonary arteries -> capillaries -> pulmonary veins -> L heart

Question 13

systemic AKA somatic circulation

Answer 13

• O blood to all body (- lungs) -> unO blood back to heart

Question 14

aorta

Answer 14

carries blood from LV -> tissues

3 parts:
1) ascending (connects to arch)

2) arch
- 2 branches:
a. brachiocephalic trunk
- supplies head, R thoracic limb
I. common carotid artery: head
ii. R subclavian artery: R thoracic limb
- further branches into R jugular

b. L subclavian artery: L thoracic limb
- further branches into L jugular

(subclavian -> axillary -> brachial -> median)

3) descending
- supplies rest of body (not head and thorax)
a. celiac artery
- just below diaphragm, unpaired
3 branches:
I. hepatic: liver
ii. L gastric: stomach
iii. splenic: spleen

b. cranial mesentric artery
- just below celiac, unpaired
- supplies intestince

c. renal arteries
- paired
- supply kidneys

d. gonadal arteries
- paired
- supply testes/ovaries

e. caudal mesentric artery
- unpaired
- supply colon

f. iliac arteries
- supply pelvis + pelvic limbs
I. external: paired, down each leg to become ‘femoral arteries’ -> popliteal -> cranial tibial
ii. internal: paired just below external, supply glutes

g. median sacral artery AKA caudal
- unpaired, supplies tail

Question 15

systemic blood flow

Answer 15

cranial/caudal vena cava return blood from cranial/caudal parts of body -> R atrium

CRANIAL
jugular + subclavian veins -> brachiocephalic veins -> cranial vena cava

CAUDAL
iliac veins -> gonadal veins -> renal veins -> portal vein (spleen, GIT, liver) -> hepatic veins -> caudal vena cava

• azygous vein helps drain both thorax + abdomen

Question 16

hepatic portal circulation

Answer 16

• carries blood from capillaries of 1 organ to capillaries of another
• blood drains from capillaries of stomach, spleen, intestines, pancreas
  -> connects in hepatic portal vein -> liver sinusoids (large capillaries)
• in liver, nutrients can be modified and stored
• also detoxifies liver from harmful things absorbed from GIT

leave sinusoids -> into hepatic veins (not portal) -> caudal vena cava

Question 17

coronary circulation

Answer 17

ascending aorta -> L/R coronary arteries -> myocardium

‘coronary’ = heart muscle

• can be blocked from fatty deposits, treated by balloon angioplasty or bypass

Question 18

fetal circulation

Answer 18

• blood moves through placenta -> exchanges CO2 + waste for O and nutrients from mother
• umbilical veins = oxygenated
• fetal lungs collapsed, resistant to flow, so blood moves from R to L side of heart through ‘foramen ovale’ and ‘ductus atereriosus’ (artery directly connecting pulmonary trunk + aorta)
• placenta -> fetus through umbilical -> ductus venosus -> drains into caudal vena cava

birth:
- air enters lungs, blood can flow normally.
- foramen ovale and ductus ateriosis close
- ductus venosis on mother closes

Question 19

which vessels are oxygenated/unoxygenated?

Answer 19

O:
- aorta, systemic arteries
- pulmonary veins, umbilical veins

unO:
- vena cava, systemic arteries, pulmonary arteries, umbilical arteries

Question 20

circulatory system pressure

Answer 20

1. systemic: high
   - hyrdostatic forces blood through capillaries
   - needs to pump against gravity
2. pulmonary: low
   - little resistance in lung vessels
   - delicate capillaries easily leak if pressure too high

Question 21

blood volume distribution

Answer 21

lungs: 15%
body: 80%
heart: 5%

Question 22

pressures

Answer 22

systole: contraction of ventricles causing heart to eject blood
- max artery pressure during ventricle contraction

diastole: relaxation of ventricles causing heart to fill
- min artery pressure during ventricular relaxation

• pulse pressure: difference b/w systolic + diastolic
• peripheral/systemic resistance: friction in arteries that limits flow

Question 23

pressure related terms

Answer 23

contractility: ability of heart to contract

afterload: force ventricles need to overcome to pump blood

preload (AKA end diastolic volume): amount of blood in heart before contraction

stroke volume (AKA systolic discharge): amount of blood ejected out of heart w/ventricular contraction

cardiac output: volume of blood heart can pump per minute
- stroke volume x heart rate

starlings principle: stretched muscle fibers have increased contractility
- more blood in -> stronger contraction

isometric contraction: just before V pump, valve stay closed and V starts to contract -> increasing pressure

ventricular ejection: semilunar open, valve empties

Question 24

preload

Answer 24

determined by end diastolic volume (ventricle filling - how much blood you have in your heart at rest [max volume before pumping])

affected by:
- leaky semilunars
- incomplete emptying from poor contractility

starling: if preload increases, contractility increases

Question 25

contractility

Answer 25

determined by: - preload - sympathetic stimulation (increases) - blood and tissue concentrations - drugs (eg. digoxin)

Question 26

afterload

Answer 26

resistance ventricles pump against - arterial 'tone' - measured by BP affected by: - sympathetic (vasoconstriction) - para (vasodilation) - in heart failure we reduce afterload w/vasodilators

Question 27

heart rate

Answer 27

controlled by: - body temp (decreased -> lower) - autonomic NS (cardio-regulatory center in medulla) - hormones (adrenal releasing epinephrine) (thyroid T4 hormone increases HR -> low HR sign of hypothyroidism) - ion levels (hyperkalemia = excess K, decreases HR) medulla: - BP drops -> sympathetic stimulated -> norepinephrine released -> HR increases - symp also makes BP increase through vasoconstriction - BP rises -> parasympathetic stimulated -> vagus nerve releases acetylcholine to SA and AV nodes -> HR slows - atropine used to correct low HRs (block acetylcholine)

Question 28

shock

Answer 28

failure of tissue perfusion - sometimes vessels dilate to a volume that exceeds blood volume -> BP falls - systolic BP <40 = dead - body shuts down peripheral circulation to focus on brain an heart - IV fluid treatment

Question 29

heart sounds

Answer 29

S1: AV close - 'lub' - prevents backflow into atria S2: semilunar close - 'dub' - prevents backflow into ventricles S3: passive filling of ventricle - 80% of blood - normal in horses, not dogs/cats S4: atrial contraction - final 20% of blood, preload established - normal in horses, not dogs/cats

Question 30

cardiac sound cycle

Answer 30

atrial contraction (S4) -> ventricular contraction/AV close (S1) -> ventricles relax/semilunar close (S2) -> passively fill as AV open (S3)

Question 31

cardiac muscle

Answer 31

- striated - involuntary - impulses travels through junctions in 'intercalated disks' (not through nervous stimulation of each cell) - automatic: can contract w/out external stimuli

Question 32

heart conduction system

Answer 32

- network of specialized cardiac muscle cells generate action potential - excitation: APs propagated (coordinated spread) - AP: depolarization of resting membrane potential from change in ions (Na, K, Ca) - repolarization: ions back to original concentration COMPONENTS: - SA node (pacemaker) - AV node - Bundle of His - R/L bundle branches - Purkinje fibers (smaller branches of bundles)

Question 33

SA node

Answer 33

small mass of cells embedded in R atrial wall near vena cava - depolarize spontaneously (100bpm in humans) - input from autonomic NS modifies - discharge is what determines HR pacemaker = depolarizes fastest

Question 34

sequence of activation

Answer 34

SA node spontaneously depolarizes -> signal to R/L atriums -> contract downward -> blood squeezed into ventricles -> impulse gets through via AV node -> L/R bundle branches OR bundle of His -> apex of heart -> purkinje fibers -> upward spread through ventricle muscle -> blood squeezed up + out of pulmonary and aortic valves

Question 35

AV node

Answer 35

slow conduction, allows atria to finish filling ventricles before they contract

Question 36

refractory period

Answer 36

relaxation right after contraction - cannot respond to another stimuli - allows chamber refill

Question 37

ECG (electrocardiogram)

Answer 37

- electrical impulse is predictable in a healthy heart (magnitude and direction) - electrodes put on skin (bc body fluid conducts impulses) - measures magnitude + direction of depolarization TERMS - p-wave: atria depolarization (contraction) - QRS complex: ventricle depolarization (contraction) (large, so hides atria repolarization) - t-wave: ventricular repolarization (relaxation)

Question 38

stroke volume determined by...

Answer 38

preload afterload contractility

Question 39

cardiac rhythm

Answer 39

sinus rhythm: heart depolarizing normally, controlled by SA node sinus arrhythmia: consistent irregeular rhythm that increases w/breath in and decreases w/breath out - normal in dogs tachy/bradycardia: HR faster/slower than normal - bradyarrythmia can be sinus arrest or AV block - tachyarrhythmia may be supraventricular (signal for depolarization above AV) or ventricular (below AV/in ventricles) atrial fibrillation: extremely rapid atria contraction, V contractions slower and irregular bc AV node only sporadically stimulated ventricular fibrillation: extremely rapid contraction of V in various small portions of wall at once - produces no pulse - will die if not CPR/defibrillation - electrocardiography will diagnose

Question 40

heart pathology

Answer 40

murmur: turbulent flow of blood - during systole..... - leak/insufficiency in AV valve (should be closed) - narrowing (stenosis) in semilunar (should be open) - OR insufficient semilunar/stenosis AV in diastole - normal in some large animals - ultrasound to diagnose

Question 41

pulse rate

Answer 41

rate = number of V contractions/minute pressure = difference b/w systolic + diastolic (amplitude) pressure required to occlude vessel = systolic - shock: pulse easy. to occlude, pressure low FEELING cat: femoral dog: femoral, lingual, dorsal pedal horse cow: facial

Question 42

comparative anatomy

Answer 42

pulmonary AKA semilunar: - dog horse cow: 3 intercostal - cat: 4 intercostal aorta: carnivores: L subclavian branches off aorta ungulates: L subclavian off brachiocephalic

Question 43

congenital pathologies

Answer 43

atrial septal defects/patent foramen ovale: - foramen ovale fails to close -> blood passes through L/R atrium AKA shunting ventricular septal defects: - small opening - complete absence of septum - blood passes through ventricle with force - shunt usually L to R - depending on size of opening, no signs or cyanosis, weakness, anorexia - common in horses, cows, large dogs persistent ductus arteriosus: - doesn't close after fetus born - results in 'machinery murmur' - common in mini/toy persistent R aortic arch: - embryonic arch persists -> displaces esophagus + trachea - often traps them in a 'ring' that compresses and results in dyspnea and regurgitation pulmonic stenosis: - narrowing at/just below semilunar - makes a murmur during systole aortic stenosis: - narrowing where L V outflows, difficult emptying tetralogy of fallot: - pulmonic stenosis + septal defect + malpositioned aorita + R V hypertrophy

Question 44

heart failure

Answer 44

- first noticed during auscultation from murmurs or arrhythmias - cause decrease in pumping efficiency - left-sided, right-sided, or generalized left-sided AKA congestive failure: - back pressure increases pressure at venous end of pulmonary capillaries - fluid forced out in lung -> edema - exercise intolerance, dyspnea, lung congestion right-sided failure: - fluid can't get out of organs -> swell and decrease function - jugular veins engorged - fluid builds up in abdomen in dogs (ascites), chest in cats (hydrothorax), under skin in large (SQ edema) generalized: - L + R failure - failure of 1 side usually results in generalized failure eventually

Question 45

acquired cardiovascular diseases

Answer 45

dilated cardiomyopathy: - dobermans, danes, boxers, cocker spaniels - link to grain-free diets + taurine deficiency - coughing, weak, weight loss, murmur + arrhythmia mitral valve degeneration parasites: - horses get aneurysm in cranial mesentric artery by stronglus vulgaris - heartworm usually in dogs, rarely in cats. grow in pulmonary arteries, R A + R V -> R V dilation + hypertrophy -> right-sided failure . weakness, exercise introlerance, coughing, fainting, murmur