Cardiorespiratory System Flashcards
(21 cards)
Chambers of Heart
4 cavities (2 atria and 2 ventricles)
Atria
- two upper, receiving chambers
- smaller, thinner, less muscular than ventricles
- where blood enters heart
Ventricles
- two lower, discharging chambers
- blood into arteries from here
Location, Size, Position of Heart
- b/w lungs in lower portion of mediastinum
- 2/3 of mass to left, 1/3 to right
- apex lies on the diaphragm, pointing to the left
- in the thoracic cavity b/w sternum in front and thoracic vertebrae behind
Myocardium
- cardiac muscle tissue
- makes up wall of each heart chamber
Endocardium
- thin layers of smooth muscle tissue
- lines each chamber
- endocarditis
- inflammation of endocardium
Pericardium
-covering sac; 2 layers of fibrous tissue
1) Visceral pericardium
- aka epicardium
- inner layer
- covers heart like apple skin
2) Parietal pericardium
- outer layer
- fits around heart like loose-fitting skin
-lubricated space b/w layers prevents frictions
Heart Action
- systole (contraction of heart)
- diastole (relaxation of heart)
- atria contract 1st (atrial systole) forcing blood into ventricles
- then ventricles contract (ventricular systole) and force blood out of heart
- directed and controlled by valves
Heart Valves
Atrioventricular (AV)
- L is bicuspid/mitral valve
- b/w L atrium and ventricle
- R is tricuspid
- b/w R atrium and ventricle
- prevent backflow of blood into atria
- chordae tendinae attach AV to walls
Semilunar (SL)
- between ventricular chambers and large arteries
- open and close at same time as each other
- Pulmonary SL at beginning of pulmonary artery
- aortic SL at beginning of aorta
- prevent backflow
Heart Sounds
-two distinct sounds in every heart beat (lub-dub)
Lub
- 1st sound
- caused by vibration and closure of AV valves during contraction of ventricles
Dub
- 2nd sound
- caused by closure of SL valves during relaxation of ventricles
Blood Flow Through Heart
- 2 separate pumps
- R is pulmonary
- L is systemic
1) Blood enters R atrium through sup. and inf. vena cavae
2) Atrial systole (R atrium) and pumped through R AV
3) Ventricular systole (R vent.) pumped through SL to pulmonary artery
4) Blood to lungs, fills with oxygen, leaves CO2
5) O2 rich blood to L atrium by 4 pulmonary veins
6) atrial systole (L atrium) past L AV into L vent.
7) Ventricular systole (L vent.) past aortic SL into Aorta
8) Aorta distributes blood to body as a whole
Cardiac Cycle
- each complete heartbeat
- includes systole and diastole
- about 0.8 seconds
- stroke volume
- volume of blood ejected from vent. each beat
- cardiac output
- volume of blood pumped by one vent./min.
- about 5L in normal, resting adult
Conduction System
- intercalated disks
- electrical connectors that join all cardiac muscle fibers in a region
- so that all receive impulse and contract together
- Sinoatrial (SA) node
- pacemaker
- causes atrial contractions
- Atrioventricular (AV) node
- triggered by relay impulse (like synapse)
- AV Bundle/Bundle of His and Purkinje Fibers
- receive impulse and stimulate ventricular systole
Electrocardiogram
- graphic record of heart’s electrical activity
- normal ECG has 3 characteristic waves
1) P wave-small, AV node and atrial walls depolarize
2) QRS complex-large, as atria repolarize and vent. walls depolarize
3) T wave-small, as vent. walls repolarize - depolarization-electrical activity triggering contraction
- repolarization-electrical activity triggering relaxation
Arteries
- distribution vessels
- blood from heart to capillaries in all body parts
- subdivide and become smaller and become tiny arterioles
- arterioles help maintain arterial BP
Veins
- blood drained from capillaries into venules
- venules increase in size and become veins
- carry blood towards heart, away from capillaries
- serve as blood reservoirs (can hold large volume)
Capillaries
- microscopic exchange vessels
- exchange of nutrients and resp. gases b/w blood and tissue fluid
- receive blood from arterioles, deliver to venules
- very thin, one layer of epithelial cells
- only 1 layer-tunica intima
- precapillary sphincter
- smooth muscle cells
- guard capillary entrances
- determine amount of blood into each capillary
Artery and Vein Structure
3 layers
1) Tunica Externa
- connective tissue fibers
- outermost layer
- reinforce wall of vessel so doesn’t burst
- thickest layer in veins
2) Tunica Media
- smooth muscle tissue
- middle layer
- thicker in arteries than veins
- in arteries it is the thickest layer, maintains BP and blood distribution
3) Tunica Intima
- inner layer
- lines arteries and veins
- single layer of squamous epithelial cells and becomes endothelium
Circulation
Systemic
- from L vent. through blood vessels to body, back to R atrium
- oxygenated blood through body
Pulmonary
- venous blood to R atrium to R vent. to pul. art. to lungs to pul. veins to L atrium
- exchange of gases between blood and air in lungs
- blood from crimson (blue) to scarlet (red) in colour
Hepatic Portal
- spleen, stomach, pancreas, gallbladder-int.
- funneled to liver, then reenters regular return
Fetal
-fetus gets O2/nutrients from maternal blood not own lungs
Blood Pressure
- pressure or ‘push’ of blood as it flows through system
- exists in all vessels
- highest in arteries
- lowest in veins
- when BP gradient present, blood circulates and vice versa
- hypertension can cause rupture of blood vessels
- if arterial pressure too low, blood doesn’t flow (perfuse)
Factors Influencing BP
blood volume
- increased volume=increased BP
- diameter of arterioles determines how much blood can drain
strength of contractions
-increase strength=increased BP
heart rate
- increased rate=decreased BP (usually)
- not as much time to refill
blood viscosity
-increased viscosity=increased BP (thickness)
resistance to blood flow
- increased tension=increased BP
- peripheral resistance
- vasomotor mechanism
Venous Blood Flow
- central venous pressure
- venous BP within atrium
- influences pressure of large peripheral veins
Mechanisms
- continued beating of heart
- adequate BP in arteries
- SL valves in veins
- contraction of skeletal muscles
- changing pressure in chest during breathing
Pulse
-alternate expansion and recoil of blood vessel wall
Pulse Points
- temporal artery
- facial
- carotid
- brachial
- radial
- femoral
- popliteal
- posterior tibial
- dorsalis pedis
