Cardiovascular System Flashcards
Slay the TBL session
Arteries
Types: elastic/conduit & muscular
Compliance: raise pressure by distending & recoiling passively
Arterioles
Extrinsic control types: neural input & hormones
Contract – blood diverted away from tissue
Dilate – blood increased into tissue
Pressure regulation – controlling resistance
Capillaries
Types: Continuous (skin/muscle – continuous endothelium & basement membrane allows exchange), fenestrated (intestines - pores), sinusoidal (liver – discontinuous endothelium & incomplete basement)
Permeability – water-filled intercellular clefts
Blood flow – other vessels in microcirculation
Substance exchange – slow forward movement
Veins
Low pressure return blood heart
Maintain peripheral venous pressure, skeletal muscle & respiratory pump
aorta
main and largest artery in the human body. It originates from the left ventricle.
aortic valve
lies at the base of the aorta. It permits blood to leave the left ventricle as it contracts
inferior vena cava and superior vena cava
carry blood to the right atrium
left atrium and right atrium
receive blood returning to the heart from the circulatory system. These upper chambers of the heart have thin walls
left ventricle and right ventricle
receive blood from the atria and contract to pump blood into the arteries
mitral valve or bicuspid valve
has two cusps (flaps). It lies between the left atrium and the left ventricle
myocardium
thick middle layer of the heart wall. It consists of cardiac muscle tissue
pericardium
double-layered sac containing the heart and the roots of the large blood vessels to which it attaches
pulmonary trunk
starts at the right ventricle and divides to form the pulmonary arteries. It carries blood to the lungs
pulmonary valve
valve lies at the base of the pulmonary trunk. It allows blood to leave the right ventricle and prevents backflow
pulmonary veins
transfer oxygenated blood from the lungs to the heart
septum
separates the left and right atria and ventricles
tricuspid valve
has tree cusps (flaps) connected to papillary muscles by chordae tendineae. It allows blood to move from the right atrium into the right ventricle and closes during contraction of the ventricle to prevent backflow
Epicardium
Simple squamous epithelium with a layer of loose connective tissue (collagen and elastin) – this provides support for blood vessels and fat below
Myocardium
Thick muscular layer, composed of cardiomyocytes joined together by intercalated discs. Bundles of cardiomyocytes, with central nuclei are found with connective tissue in between (lighter areas). The myocardium contains an extensive capillary network. The thickness of the myocardium varies between individuals, and also between health and disease
Endocardium
Layer of flattened endothelial cells, supported by fibrous (and some elastic) connective tissue which lines the chambers of the heart
Identifying cardiac muscle cells
cross section - rounded cross-section w/ central nucleus
longitudinal section - joined end-end & often branched
Intercalated discs - specialised junction, appear thin, dark perpendicular to muscle fibre
Lipofuscin pigment - lysosomal digestion residue = yellow brown granules
Right atrium
receives venous blood from systemic circulation
pectinate muscle (bundles protrude from surface) common
heart valves
folds in endocardium anchored to cardiac skeleton(fibrous skeleton)
dense connective tissue
avascular
cardiac skeleton
4 fibrous rings of dense irregular connective tissue
attachment site for heart valve leaflets & myocardium
electrically insulates atria above from ventricles below
Purkinje Fibers
carry cardiac impulses from AV & branch beneath endocardium
stain lighter than surrounding
larger cells, large amounts of glycogen & fewer myofibrils
Tunica Intima
- Endothelium - simple squamous epithelium joined by tight junctions
- Subendothelial connective tissue
- Internal elastic lamina - more prominent in arteries
- Fenestrated sheets of elastic fibers
Tunica media
typically the thickest layer in arteries
* Concentric layers of smooth muscle cells
* Various amounts of elastic and collagen fibers are interspersed between the smooth muscle cells
* These fibers are produced by the smooth muscle cells (not fibroblasts)
* External elastic lamina - only present in large arteries
* Fenestrated sheets of elastic fibers
Tunica adventitia
typically the thickest layer in veins
* Longitudinally arranged dense connective tissue
* In large veins, bundles of smooth muscle cell are present
Arterial size relation to elastic fibres & smooth muscle cells
As arterial size decreases, the relative amount of elastic fibers within their walls decreases and the relative amount of smooth muscle cells increases.
Atherosclerosis
hypertension injury to tunica intima - coordinated regulation of apoptosis, cell recruitment, proliferation, migration, and differentiation required for repair
Types of cardiomyocytes
Pacemaker (Autorhythmic) – 1%: Located in the sinoatrial (SA) node. Generate electrical impulses (action potentials) spontaneously and depolarize adjacent cells through gap junctions (within intercalated discs).
Contractile cells - 99%: Cells next to pacemaker cells become depolarised and contract.
atrial excitation
process by which the sinoatrial (SA) node in the heart generates an electrical signal that causes the atria (top chambers of the heart) to contract
How long does AV delay impulse & why
0.09s
eject all blood intro ventricles
ventricular excitation
impulse from AV->bundle of His -> bundle branches -> Purkinje fibres and near simultaneous contraction
Atrial systole
atrial myocytes contract, blood forced into ventricular chambers
Atrial diastol
atrial myocytes relax
Ventricular systole
ventricular myocytes contract, blood forced into aorta and pulmonary artery
Ventricular diastole
ventricular myocytes relax
How is resting membrane potential maintained
NA+ & Ca2+ ions pumped out and K+ pumped in by ion pumps
action potential
brief reversal of the polarity of the cell membrane
caused by the movement of ions through voltage gated ion channels – these allow certain ions through at certain values or voltages of membrane potential.
When membrane potential increases (less negative) – the cell is said to be depolarised. When the membrane potential decreases – the cell is said to be repolarised.
