Circulation and Vessels Flashcards
Purpose of circulation
Delivery and exchange of nutrients and waste.
Most important single activity
Oxygen delivery.
The aorta has lots of ____ tissue and is very _______.
The aorta has lots of elastic tissue, and it is very distensible.
The aorta ____ energy during systole, and ____ energy during diastole.
It stores energy during systole, and returns it during diastole.
Stopcocks of the vascular system
Arterioles
Arterioles are made of _____ muscle, and are controlled by __________.
Arterioles are made up of smooth muscle, and are controlled by sympathetic activity.
What do the arterioles control?
They control vascular resistance, blood pressure, and localized flow and delivery according to activity and need.
These vessels are complex networks in charge of gas diffusion and fluid osmosis.
Capillaries
Transit time in capillaries?
1-3 seconds
Surface area of capillaries
500 m2
Capillaries are made up of _____ cells.
endothelial.
Diameter of a capillary?
8 microns (roughly the size of one RBC)
3 mechanisms of venous return
- muscle pump
- soleal sinuses
- one-way valves
Venous return is a ___ pressure system, __-__ mmHg.
It is a low pressure system, 0-15 mmHg.
Collecting tubes from capillaries
Venules
Venules have __ layers: _______ & _______
They have 2 layers: the intima (made up of endothelial cells) and the adventitia. They have no media.
These vessels are compliant and their walls are thinner than those of arteries.
Veins
Veins hold ____ of all blood, this is called the _________.
The hold 2/3 of the blood in the circulatory system, this is known as the venous reservoir.
Veins can expand how many times more than arteries?
4-5x more
3 types of veins in LE?
- Deep
- Superficial
- Perforators
These types of veins always accompany arteries
Deep veins
These veins run along the surface of the skin
Superficial veins
These veins are the communication between superficial and deep veins
Perforators
Why does the body need the venous reservoir?
It is needed during exercise and hemorrhage. It holds the potential volume you can supply to the body when in need.
Venous valves have __ cusps and are made of ____ cells.
They have 2 cusps and are made of endothelial cells.
Pro and con of sinuses?
Pro: can help close the valves
Cons: can be an area of potential stasis
Flow in perforator veins always flows from ____ to ____.
Superficial to deep
Primary mechanism for venous return?
Muscle pump (especially in the leg/calf muscles)
The muscle pump overcomes _____ ______.
Hydrostatic pressure.
What type of veins lie with in the muscle?
Deep veins
Venous valves create _____ ____ to ensure flow goes up. They ____ ____the column of fluid.
They create pressure gradients and break up the column of fluid.
The muscle pump is also known as the ____ ____.
Peripheral heart
Mechanism of the peripheral heart
Contraction: pushes blood upward
Relaxation: blood goes superficial to deep
