Lecture 8/9 - Cardio Flashcards
circulation overview - low pressure, high pressure, capillary beds, lymphatic circulation, heart as a pump
high pressure
* arterial side
* well oxygenated blood
* rich in nutrients
low pressure
* venous side
* poorly oxygenated blood
* poor in nutrients
* waste products
- heart acts as a pump arteries away from heart veins back to heart
- capillary beds act as site of exchange between tissues & blood
lymphatic circulation tends to parallel blood vasculature
blood vessels overview - hollow tubes of what, what is the cavity lined with, what does the wall contain, what size vessels have more elaborate wall contents
- blood vessels are hollow tubes of tissue, with blood flowing in the interior (lumen)
- cavity lined with simple squamous epithelium: endothelium
- wall contains varying amounts of smooth muscle, dense and loose connective tissue, including elastin sheets, organized into 3 layers
- larger vessels have more elaborate wall contents than
smaller vessels
components of blood vessel walls - names of three layers, there its predominant, major components, function, variability if thickness of each component
-Tunica Intima or Intima; predominates in microcirculation
- major components = endothelium, basal lamina, loose CT
- function = non thrombogenic
surface; interface with underlying tissue; signaling
-Tunica Media or Media; predominates in arteries
- major components = circumferential vascular smooth
muscle, CT with collagen & elastin
- function = smooths & regulates flow
-Tunica Adventitia or Adventitia;
predominates in veins
- major components = CT with collagen & elastin; sometimes
longitudinal smooth muscle; vasa vasorum
- function = resistance to maintain blood pressure; anchors
vessel in place
thickness of each component varies in characteristic fashion with blood vessel type
components of blood vessel walls - more details of each layer
Tunica Intima (Intima)
* inner layer of endothelium in contact with flowing blood
* supported by basement membrane and variable amount of loose CT
Tunica Media (Media)
* middle layer of primarily smooth muscle
* variable amount of collagen &
elastin
Tunica Adventitia (Adventitia)
* outer layer of dense irregular CT
* merges with surrounding CT to
anchor vessel in place
specializations - what is the name for vessels of the vessels, where is it found, what does it ensure
where are valves found and its function
vasa vasorum:
* ‘vessels of the vessels”
* found in media/adventitia of large arteries & veins
* ensures tissue of vessel wall
receives nutrients, etc.
valves:
* found in small-medium veins
* protrusions of intima that
prevent blood backflow
artery vs vein - more what in each, pressure
- high pressure with pulsations
- more muscle & elastin
- valves, sometimes cardiac muscle, thoracic pressure
- more fibrous CT
features of blood vessel walls - what happens when you go from larger to smaller vessels (arteries and veins), general differences
larger to smaller vessels (both
arteries and veins):
* lumen diameter decreases
* wall thickness decreases
* fewer layers of smooth muscle
* less elastic tissue & less connective tissue
in general:
* arteries have thicker walls for their diameter than veins
* smallest vessels lack complete coat of smooth muscle
elastic artery - specifics of the three layers, example of where its found
- Intima: variable CT; endothelium; rare smooth muscle cells
- Media: extensive smooth muscle, multiple elastin laminae; “internal elastic membrane” not obvious
- Adventitia: mostly dense irregular CT; collagen rich
e.g. thoracic aorta and major initial branches
large muscular veins - specifics
- Intima: endothelium; some smooth muscle
- Media: some smooth muscle; cardiac muscle near heart; collagen & elastin
- Adventitia: dense irregular CT, some elastin; longitudinal smooth muscle
muscular artery specifics and example
- Intima: endothelium; prominent internal elastic membrane
- Media: extensive smooth muscle, sparse elastin fibres; internal elastic membrane very obvious; external elastic membrane not obvious
- Adventitia: dense irregular CT; collagen rich but more elastin
e.g. femoral artery
medium vein specifics and example
- Intima: endothelium; some smooth muscle
- Media: some smooth muscle; collagen
- Adventitia: dense irregular CT; some elastin; some longitudinal
smooth muscle
e.g. saphenous vein
small artery and vein
- muscular arteries maintain
similar appearance as they get
smaller and smaller - small veins get thinner walled
as they get smaller
microcirculation - 4 kinds we talk about and what they look like
arterioles:
* 100 - 10 μm in diameter
* 1-3 layers of smooth muscle
* sparse adventitia
capillaries:
* 4 - 10 μm in diameter
* no smooth muscle; occasional pericytes
* no real media or adventitia
postcapillary venules:
* 10 - 50 μm in diameter
* no smooth muscle (some pericytes)
* no real media or adventitia
muscular (large) venules:
* 50 - 100 μm in diameter
* 2+ layers smooth muscle
* some obvious adventitia
pericytes - what do they subsitute, function
- substitute for smooth muscle
in capillaries/ small venules - wrap around vessel tube;
share basal lamina with endothelial cell - vessel stability, signaling
capillary wall structure - what layers are present, direction and function, what determines amount and exchange, three routes of exchange
- basically only intima: endothelium & varying amounts of basal lamina; may be pericytes
- sites of exchange between blood and tissue; bidirectional!
- amount and type of exchange depends on type of vessel
Routes of exchange:
-‘between’ cells (cell-cell junctions)
-‘across’ cells (pinocytosis/transcytosis)
-‘through’ cells (fenestrations and gaps)
continuous vs fenestrated vs discontinuous/sinosoid capillaries - examples and function of each
-Continuous CNS
- examples = Muscle, Skin, Lung
- function = blood-brain barrier, metabolic exchange, gas exchange
-Fenestrated Endocrine glands
- examples = Gl tract, Kidney, glomerulus
- function = hormone secretion, nutrient absorption, blood filtration
-Discontinuous/Sinusoid Liver
- examples = Bone marrow, Spleen
- functions = particle exchange, hematopoiesis, red cell filtration
continuous capillaries - what does the endothelium form, what do endocytic vescicles provide, holes, common capillary type in what
endothelium forms junctional
complexes with adjacent cells
* endocytotic vesicles provide
transcellular route for bulk transport
* no gaps or holes in the
endothelial layer
* common capillary type e.g. muscle, skin, lung
blood brain barrier capillaries - involves in what, junctions, reduced what, what are features induced by, consequences
- active transport & receptor-mediated endocytosis
- very occlusive “tight” junctions; limited intercellular transport
- reduced pinocytosis/transcytosis; no fenestrations
features induced by astrocyte/endothelial interactions?
consequences: highly regulated environment; challenge for
drug entry
fenestrated capillaries - where are they normally found, what do they look like
- disc-like pores in endothelial cells, often in patches
- enhanced permeability to small to medium sized molecules (albumin)
- kidney, endocrine glands, GI tract
sinusoids - what kind of capillary are they, what is discontinuous, permeability, found where
Sinusoids
* sinusoidal capillaries; discontinuous capillaries
* very large fenestrations, gaps in cell-cell adhesion, discontinuous basal lamina: very permeable, even to cells
* liver, spleen, bone marrow
heart wall - layer names
epicardium ~ tunica adventitia
(visceral pericardium)
myocardium ~ tunica media
endocardium ~ tunica intima
heart wall layers - what is present in each, type of epithelium
1) Endocardium
* endothelium (simple squamous epithelium w/ basal lamina)
* connective tissue
* small blood vessels & nerve endings
* Purkinje fibres - modified cardiac muscle cells; conduct
signals to control contraction
2) Myocardium
* cardiac muscle cells and connective tissue
3) Epicardium
* simple squamous epithelium (= mesothelium = visceral
pericardium)
* connective tissue
* muscular arteries, arterioles and associated veins
* nerves & adipose tissue
heart contraction - contractile regulation, what is it modulated by, how does action potential spread, how is it propagated, what does it ensure
- heart has intrinsic contractile
regulation: Sino Atrial (S-A)
node (pacemaker) & Atrio-
Ventricular (A-V) node - modulated by autonomic
nervous system - action potential spreads rapidly
through heart tissue via Purkinje
fibre bundles - action potential propagated cell
to cell via gap junctions in
intercalated discs - ensures coordinated
contraction
purkinje fibers - what are they, function, location, what is stored and how does it stain, what is it predominant in
- Purkinje fibres are bundles of
modified cardiac myocytes - non-contractile; specialized for
conduction - larger, fewer myofilaments,
located at periphery of cell - large glycogen stores- pale
staining in H & E - predominant in endocardium
lymphatic capillaries - what do they have, gaps where, what is discontinuous, what are they efficient at, functions,
- have endothelium, but molecular differences
- large gaps between cells
& poorly occlusive junctions - discontinuous basement
membrane - particularly efficient at
picking up tissue fluid, cells,
macromolecular complexes - drainage of fluid through
lymphatic organs - lymph eventually returned
to blood circulation
small lymphatic vessels - appearance, what are lacteals
- irregular, thin walled
- often collapsed and poorly visible unless edema
- blind ended lymphatics in intestinal villi frequently prominent: lacteals
large lymphatic vessels - wall thickness, where are valves present, function of largest lymphatics
-even sizable lymph vessels are
very thin walled
* valves are present in all but the
smallest lymphatic vessels to prevent backflow
* largest lymphatics have some
muscle/pumping?
