module 4 - lecture 11 Flashcards
Blood flow
- Blood flows away from the heart
within arteries, and returns to the
heart in veins
capillaries
the junction between arteries and
veins
“Exchange vessels”, due to thin walls
* Transfers nutrients, gases to organs,
tissues & cells
* Picks up and transfers waste products
from organs, tissues & cells
Three types: continuous,
fenestrated, sinusoidal
blood vessels
- The walls of arteries and veins have three
layers: - Tunica intima
- Tunica media
- Tunica externa
- All vessels lined by endothelial cells
Tunica intima
- Innermost layer
- Endothelial cells (simple squamous cells)
- Internal elastic membrane is present in arteries
Tunica media
Contains smooth muscle (vasoconstriction & vasodilation)
* Amount of muscle (thickness) is proportional to size (diameter) of
vessel and blood pressure
- Tunica externa
Outermost layer
* Contains collagen (thicker in veins)
* Blends/adheres with adjacent tissues – stabilizes and anchors the vessels
Arterioles
Tunica externa absent or minimal
* Smooth muscle cells to alter diameter
Venules
- Collect blood draining
from capillary beds - Lack tunica media layer
Elastic vs muscular artery
Elastic – stretches & recoils due to
pressure change (i.e. heart beats)
* Muscular – distribute blood; thicker layer
of smooth muscle; can alter luminal size
Venous vs arterial
Arterial system is high pressure,
compared to the venous system
Therefore, veins contain valves
* Unidirectional blood flow (like the
heart valves)
* Weakened valves can result in
varicose veins
Lymphatic System
Lymphatic vessels carry lymph (tissue fluid)
from peripheral tissues to the venous system.
Lymphatic capillaries are ‘closed vessels’,
unlike blood vessels connected in a circuit.
Lymphatic vessels drain into two large collecting vessels
* Right lymphatic duct - Right side of the body, above the diaphragm
* Thoracic duct - Rest of body; and inferior
to the diaphragm on right-hand side.
