Download capillaries

Khaleel Alyahya
[email protected]
Saturday November 14, 2009
Heart Anatomy
 Approximately
the size of your fist
 Location
 Superior surface of diaphragm
 Left of the midline
 Anterior to the vertebral column, posterior to the
sternum
Blood Circulation

The left side of the heart pumps blood out the aorta (which is
a large elastic artery) to a system of muscular arteries,
arterioles then to capillaries.

Blood from the arterioles enters the capillary bed where
exchange of substances occurs.
Blood Circulation

The blood enters venules, on to small veins,
medium veins, and finally the large veins that empty
the venous blood back into the right side of the
heart.

Note: At the capillary beds, excess fluid and protein
is picked up by lymphatic vessels, filtered through
lymph nodes, and returned to the large veins.
General organization of vessels

Vessel walls are divided into 3 layers, called tunicae.

1) Tunica intima: includes the endothelium (SSE) and the
underlying loose C.T.

2) Tunica media: the middle layer which contains smooth
muscle and or elastic membranes.

3) Tunica adventitia: the outermost connective tissue layer
composed mainly of dense irregular connective tissue. The
tunica adventitia is broad and contain numerous vasa
vasorum.
General organization of vessels
General organization of vessels

The tunica intima of veins is similar to that of arteries, but the
internal elastic lamina is thin or absent

The tunica media is much thinner than the accompanying
artery.

Tunica adventitia is much thicker than tunica media.
General organization of vessels
Vein
Arteries
Elastic Arteries

These are the largest arteries in the body, and
include the aorta, pulmonary trunk and their
major branches.

This elasticity permits elastic arteries to resist the
force of pressure of the heart beat.
Elastic Artery
Arteries
Muscular (distributing) Arteries
 Muscular (Distributing) Arteries have the same basic
structure as elastic arteries BUT the elastic tissue is
reduced.
 The tunica media is composed of concentric layers of
smooth muscle.
 They show a well-defined Internal elastic lamina (IEL).
They may show External (outer) elastic lamina (EEL).
Muscular Artery
Muscular Artery
Muscular Artery
The tunica intima (I), with its internal elastic lamina
Muscular Artery
Tunica adventitia (A) is distinct in muscular arteries
Capillaries

Capillaries are the smallest blood vessels, and contain only a
single layer of flattened endothelial cells and their basal
laminae.

Muscular and adventitial layers are absent.

Pericytes may be present at the periphery of capillaries.

Capillaries are designed to permit exchange of gas, nutrient and
waste in the tissue.

Connect the two sides.
Capillaries
Questions?