i want 30 mutiple choice questions with their model answer below them tat covers different aspects of all of the following : Large arteries (Elastic arteries)
➢Ex: the aorta & pulmonary arteries. ➢Outer diameter: >10 mm.
The tunica media of elastic arteries is broad and extremely elastic (have multiple sheets of elastic lamellae)Large Elastic Artery (Aorta)
Tunica intima: Well developed ▪ Endothelium with its basal lamina. ▪ Subendothelial C.T. with smooth muscle cells. ▪ Internal elastic lamina (present but not conspicuous (not obvious) and identified by being the innermost elastic layer).
Tunica media: Thickest layer ▪ Concentric layers of fenestrated elastic lamellae alternating with layers of smooth muscle cells. ▪ Reticular fibers and ground substance.
Tunica adventitia: Thinner than the media. ▪ Collagen and elastic fibers. ▪ Fibroblasts. ▪ Vasa vasorum & nervi vasorum.AortaAorta
Intima
Fenestrated Elastic lamellae
Media
➢ In adults, the aorta has
40-70 elastic lamellae
Adventitia
➢ The number and thickness
of the elastic lamellae are
increased in individuals
with hypertension.Aorta
Nervi vasorum
Vasa vasorum
AdventitiaMedium-sized arteries (Muscular aMuscular arteries
Tunica intima: Thin • Very thin subendothelial layer. • Prominent internal elastic lamina.
Tunica media: ▪ More smooth muscle cells (concentricallyMuscular arteriesMedium sized muscular artery
Large muscular artery
IEL
N.B. In arteries, as the vessels become smaller:
the amount of elastic tissue decreases, and the smooth muscle component
predominates.Specialized types of medium sized muscular arteries
1. Cerebral arteries (Basilar artery)
Will be discussed in practical lab
2. Coronary arteries
Cerebral arteryCoronary arteries
IEL
▪ Medium-sized muscular arteries.
▪ Their walls are thicker than those of comparable
arteries of lower and upper limbs.
▪ Their walls have high collagen-to-elastic fiber ratio
which reflects high tensile strength.
➢ Tunica intima:
✓Thin in younger people (the subendothelial layer is
ill-defined with normal, periodic thickenings at
branching sites).
✓ It progressively thickens with aging by increasing
amounts of smooth muscle cell and fibroelastic tissue.
✓Prominent internal elastic lamina.
Collagen fibers
Adipose tissue
EEL
Smooth muscle cells
Adventitia
MediaCoronary arteries
IEL
➢ Tunica media:
✓ Thicker (due increased number of circular smooth muscle
layers).
✓ Bundles of longitudinally arranged smooth muscle.
✓ Prominent external elastic lamina.
➢ Tunica adventitia:
✓ Thicker relative to that of other medium arteries.
✓ It consists of longitudinal bundles of collagen fibers,
some elastic fibers, and adipose tissue.
✓ Bundles of longitudinally arranged smooth muscle.
➢ Because coronary arteries bend repeatedly during systole
and diastole, both media and adventitia contain bundles
of longitudinally arranged smooth muscle.
Collagen fibers
Adipose tissue
EEL
Smooth muscle cells
Adventitia
MediaCoronary arteriesSmall arteries
➢ Diameter: 0.1-1 mm
➢ Tunica Intima: has an internal elastic lamina.
➢ Tunica Media: 3-10 layers of concentrically
arranged smooth muscle cells and contains
almost no elastic fibers.
➢ Tunica adventitia: thinner than media.
Small arteries are muscular arteries that
distribute blood to arterioles.Arterioles
➢ Diameter:< 0.1 mm (10-100 µm)
➢ Tunica Intima: Endothelium, very thin subendothelial layer.
NO internal elastic lamina.
➢ Tunica Media : 1-3 layers of smooth muscle cells.
➢ Tunica adventitia: very thin.
No External Elastic Lamina in both small arteries and arterioles
Transition from small arteries to arterioles is gradual and involves:
✓ loss of the internal elastic lamina.
✓ progressive reduction of the number of muscle layers in the media.Functions of arterioles
➢The major determinants of systemic blood pressure:
▪ As arterioles are partially closed due to their muscle tone
peripheral resistance to blood flow.
▪ Blood pressure depends on cardiac output & peripheral
resistance to blood flow.
Increase arteriolar constriction
➢Control blood flow to capillaries
Essential hypertensionArterioles
Metarterioles
Are the terminal branches of arterioles in which
the smooth muscle cells are thickened at origin of
capillaries & act as precapillary sphincters.
The distal portion of the metarteriole, called a
thoroughfare channel, lacks smooth muscle cells
and merges with the postcapillary venule.
Capillaries branch from the metarterioles.
Metarterioles
CapillariesPrecapillary
sphincter:
is the thickened smooth muscle fibers at the origin of a capillary
bed from metarteriole.
▪ They control entry of blood through capillaries in a pulsatile manner through cyclic contraction and
relaxation.
▪ For efficient exchange of nutrients, wastes, O2, and CO2 across the endothelium.
Relaxed sphincter:
blood flows from the metarterioles into capillary bed.
Contracted sphincter:
blood flows directly from the metarterioles and
thoroughfare channels into postcapillary venules.VeinsPostcapillary venules
Collecting venules
Muscular venules
✓ Similar to structure of capillaries (endothelium +
pericyte) but larger.
✓ No smooth muscle layer.
✓ Sites of leukocyte migration.
larger, with more pericytes.
✓ Wider lumen
✓ Tunica intima: thin
✓ Tunica media: one or two
layers of smooth muscle
cells
Small veins
✓ Tunica adventitia: thin
0.1-1 mm
❖All venules have
wide lumen & thin
wall.
Diameter: 10-100 µm
Medium-sized
veins
Large veins
1-10 mm
> 10 mm
C: capillary
PCV: postcapillary venule
CV: collecting venule
MV: muscular venuleSmall veins
➢Accompanied by corresponding small
arteries.
➢The intima: endothelium with its
basal lamina & a thin subendothelial
layer.
➢The media: consists of two or three
layers of smooth muscle cells + reticular
and few elastic fibers.
➢The adventitia: is thicker than media.
IEL
Small artery
Small veinMedium-sized veins
Accompanied by corresponding muscular
arteries.
e.g., radial vein, tibial vein, popliteal vein.
Intima: endothelium with its basal lamina &
subendothelial C.T., with valves.
Media: 3-5 layers of circular smooth muscle
cells + reticular and few elastic fibers.
Adventitia: thicker than media.
No IEL/EELMedium-sized vein
Tunica media
Tunica adventitiaVenous Valves
Valves:
✓Paired semilunar folds of the intima projecting into
the lumen.
✓Consists of C.T. core rich in elastic fibers covered by
endothelium on both sides.
✓ In medium and large sized veins .
✓More numerous in the veins of lower limbs.
✓ Prevent retrograde movement (backflow) of blood.Remember
veins
Wide lumen
Thin wall
No IEL
No EEL
Thick
adventitia
Valves in
medium and
large sized
veins .Medium sized artery
Medium-sized artery and vein
Medium sized vein
Wall thickness
lumen
Valves
T. intima
T. media
Thick
Narrow
Absent
Prominent internal elastic
lamina
Thick, made of MORE
smooth muscles rather than
elastic fibers
T. adventitia
Moderate in thickness
(nearly the same thickness of
media)
Thin
wide
Present
No internal elastic
lamina
Thin, made of
smooth muscles,
poor in elastic fibers
Very thick (the
thickest layer)Large veins
EX. Superior vena cava, inferior vena cava and portal vein.
Intima: well-developed ,has valves Media:
is relatively thin, with layers of circularly arranged smooth muscle cells, some collagen & elastic fibers.
Adventitia: It is the thickest layer It contains longitudinal bundles of smooth muscle fibers