Chapter 20 Flashcards
functions of heart & blood vessels (3)
transport water, gases (O2, CO2, N2), proteins & hormones throughout body
- regulate temperature & blood pH
facilitate functions of immune system
Location of the heart
in the mediastinum
extends from sternum anteriorly to vertebral column posteriorly & lies medially between lungs & pleural membranes that cover them
2/3 of heart’s mass is slightly left of midline
Base of heart
posterior surface - formed by atria
tipped up medially & posteriorly
Apex of heart
formed by tip of left ventricle
projects inferiorly & laterally to left
Pericardium`
membrane that surrounds & protect heart & retains its position in mediastinum
(2) main parts
composed of a tough outer fibrous layer lined by a delicate serous membrane
(2) main parts of Pericardium
1) fibrous pericardium
2) serous pericardium
1) fibrous pericardium
very dense irregular CT
helps anchor & protect heart
2) serous pericardium
deep to fibrous pericardium
thinner, more delicate membrane that forms double layer around heart
(2) layers of serous pericardium
1) parietal layer
2) visceral layer
1) parietal layer of serous pericardium
adheres to ourmost fibrous layer
2) visceral layer of serous pericardium
epicardium
- inner layer
one of the layers that adheres tightly to surface of heart
Pericardial Cavity
space between parietal & visceral layer of serous pericardium
- contains pericardial fluid that lubricates space (secretion of pericardial cells)
Layers of Heart Wall (3)
1) Epicardium
2) Myocardium
3) Endocardium
1) Epicardium
thin, transparent outer layer (visceral layer of serous pericardium) - composed of mesothelium
- fibroelastic & adipose tissue beneath
contains blood vessels, lymphatics, and vessels that supply the myocardium.
2) Myocardium
thick middle layer - composed of cardiac muscle
responsible for the pumping action of heart
- makes up 95% of heart wall
3) Endocardium
thin layer of endothelium (simple squamous epithelium of circulatory system) overlaying thin CT layer
- smooth lining for chambers & covers valves
Chambers of the Heart
upper → Right & Left Atria
lower → Right & Left Ventricles
Right Heart
right atrium & right ventricle
taking venous blood from body & pumping to lungs for oxygenation
**→ powerspulmonary circuit **
Left Heart
left atrium & left ventricle
taking freshly oxygenated pulmonary blood & pumping it systemically
→ powers **systemic circulation **
Top part of heart
weak pump → right & left atria
- loads ventricles by giving an atrial kick before ventricle contract
Bottom part of heart
a strong pump consisting of right & left ventricles
- main pump for pulmonary & systemic circuits
Atrial kick
force contributed by atrial contraction immediately before ventricular systole that contributes to 20% increase in blood ejected by ventricles
Chronic Atrial fibrillation
no atrial kick
flow of blood is dictated by?
pressure differences not muscle
flows from area of high pressure to area of low pressure.
Heart Valves (2)
1) Atrioventricular
2) Outflow (semilunar)
1) Atrioventricular
open to allow blood to flow from atria into ventricles
located at entrance of ventricles
2) Outflow (semilunar)
open to allow blood to flow from ventricles into outflow vessels
located at entrance to outflow vessels leading into pulmonary & systemic circulation
1) Atrioventricular (2)
1) tricuspid (right AV) valve
2) bicuspid/mitral (left AV) valve
2) Outflow (semilunar) (2)
1) pulmonary (right outflow) valve
2) aortic (left outflow) valve
1) tricuspid (right AV) valve
3 leaflets/cusps → opens into right ventricle
2) bicuspid/mitral (left AV) valve
opens into left ventricle
1) pulmonary (right outflow) valve
opens into pulmonary trunk
2) aortic (left outflow) valve
opens into aortic arch
**Operation of Atrioventricular Valves **
- ventricles relaxed
when ventricles relaxed, papillary muscles relaxed & chordae tendinae are slack
blood moves from higher pressure in atria to lower pressure in ventricles through open AV valves
when open, rounded ends of cusps
Operation of Atrioventricular Valves
- ventricles contracting
when ventricles contract, pressure of blood drives cusps upward until edges meet & close opening
papillary muscles contract at same time, pulls on & tightens chordae tendinae to prevent cusps from opening into atria in response to high ventricular pressure
Operation of Semilunar Valves
made up of 3 crescent moon-shaped cusps
- each attached to arterial wall (each = 1/3 of valve)
- allow ejection of blood from heart into arteries but prevents backflow into ventricles
Operation of Semilunar Valves
- ventricles contract
pressure builds up in chambers
SL valves open when ventricle pressure > artery pressure → ventricular ejection
ejects blood from ventricles into **pulmonary trunk/aorta **
Operation of Semilunar Valves
- ventricles relaxed
SL valves close
- when blood in aorta/pulmonary outflow tract **leaks back into ventricles **
- SL cusps act as sails, fill up & free edges contact & close opening
No valves guarding which (2) junctions
1) between venae cava & right atrium
2) between pulmonary veins & left atrium
Backflow of blood between:
venae cava & right atrium
pulmonary veins & left atrium
as atria contract, small amount of blood flows back into vessels but minimized by the way atria contract
- which compresses & **nearly collapses venous entry points **
Arteries
vessels that always conduct blood away from heart
- contain oygenated blood (few exceptions)
- thick-walled & exposed to high pressure & friction forces
Veins
vessels that always bring blood back to heart
contain de-oxygenated blood (few exceptions)
thin-walled & exposed to low pressures & minimal friction forces
Arteries carry oxygenated blood - Exceptions?
pulmonary arteries (& umbilical)
→carry de-oxygenated blood to lungs (pulmonary capillaries)
Veins carry de-oxygenated blood - Exceptions?
pulmonary veins (& umbilical)
→ carry oxygenated blood to **left atrium **
Major arteries that attach to heart
1) arch of aorta (ascending &descending)
2) pulmonary trunk (left & right pulmonary arteries)
3) **coronary arteries **
Major veins that attach to heart
(4)
1) superior vena cava
2) inferior vena cava
3) pulmonary veins (4)
4) coronary sinus (on back of heart)
(2) circuits of blood flow
1) Systemic
2) Pulmonary
1) Systemic Circulation
ejects blood into aorta, systemic arteries & arterioles
- is powered by left side of heart.
1) Pulmonary Circulation
ejects blood into pulmonary trunk
- powered by **right side of heart **
starting with venous return to heart.. blood flow?
deoxygenated blood →right atrium from (3) sources →right side of heart → lungs
oxygenated blood → left side of heart to be pumped through outflow tract of systemic circulation
Right Atrium recieves blood from? (3)
1) superior vena cava
2) inferior vena cava
3) coronary sinus
left side of heart pumps…
oxygenated blood into systemic circulation to all tissues of body except the air sacs (alveoli) of lungs.
right side of heart pumps…
deoxygenated blood into the pulmonary circulation to air sacs (alveoli) of the lungs
Blood Flow - complete circle
RA → triscuspid valve → RV → pulmonary trunk & arteries → lungs (pulmonary capillaries) - blood loses CO2 & gains O2
Lungs → pulmonary veins → LA → bicuspid valve → LV → aortic valve →aorta & systemic arteries → body systemic capillaries ** **
Coronary Circulation
blood circulation in network of blood vessels in myocardium - supplies nutrients
Coronary Circulation
- HEART CONTRACT/RELAXED
coronary arteries branch from ascending aorta
- encircle heart
when heart contracts, little blood flow in coronary arteries (squeezed shut)
when heart relaxes, high pressure of blood in aorta propels blood through coronary arteries → capillaries → coronary veins
When does blood flow through coronary circulation?
only during relaxation phase of ventricular **diastole **
Blood flow through Coronary circulation
- Coronary **Arteries **
aorta → left & right coronary arteries
LCA → anterior interventricular + circumflex branches
RCA → marginal + posterior atrioventricular branches
Blood flow through Coronary circulation
- Coronary Veins
arteries of coronary circulation → capillaries → deliver nutrients & O2 to heart muscle → coronary **veins **
→ coronary sinus → right atrium (de-oxygenated blood joins with that of the rest of body)
Cardiac Muscle Tissue
striated
shorter fibers than skeletal muscle
- branch
- only 1 central nucleus
Cardiac Muscle Cell Communication
connect to & communicate with neighboring cells through gap junctions in intercalated discs
Which tissues of heart can derive oxygen from blood flowing through chambers?
innermost tissues
Formation → Autorhythmicity of Heart Muscle Cells
During embryonic development, about 1% of all cardiac muscle cells become autorhythmic fibers & form network/ pathway called **cardiac conduction system. **
cardiac conduction system
network of specialized cardiac muscle fibers that produce path for each cycle of cardiac excitation to progress through heart
specialized group of myocytes
have ability to spontaneously depolarize
Autorhythmicity
rhythmical electrical activity produced by autorhythmic fibers