Session 1 - Intorudction To + Histology Of The CVS Flashcards
What are the minimum and maximum amount of blood that the heart must pump?
5 - 25 L/min
What blood flow must the heart supply to the brain and at what times?
0.75 L/min at all times
What three organs must have a constant blood supply?
Brain, Heart Muscle and Kidneys
Which tissue has the greatest difference in minimum and maximum blood flow?
Muscle - 1-16 L/min
What are the main functional components of the circulation?
- A Pump
- Distribution Vessels
- Flow Control
- Capacitance
What is the average distribution of blood over the major parts of the circulation?
- 67% in Veins (3.35L)
- 17% in Heart and Lungs (0.85L)
- 11% in Arteries and Arterioles (0.55L)
- 5% in Capillaries (0.25L)
What are the functions of arteries as a whole?
Carry blood away from the heart
What are the two types of arteries?
Elastic (conducting) and Muscular (distributing)
What is the main function of arterioles?
To regulate the amount of blood reaching an organ or tissue and regulate bp
What is the diameter of arteries and arterioles controlled by?
The Autonomic nervous system
What do arterioles flow into?
Metarterioles
What is the main function of capillaries?
Facilitate exchange of substances between blood and surrounding tissues
What do capillaries flow into?
Venules
What two mechanisms do veins have to ensure that blood flows back to the heart?
Valves and muscular pumps
What are the three layers of arteries and veins?
Tunica Intima
Tunica Media
Tunica Adventitia
What is the main feature of the tunica media in elastic arteries?
40-70 fenestrated elastic membranes
What is the vasa vasorum?
“Vessels with vessels” - Lymphatic vessels and nerve fibres in the tunica adventitia
What is the main feature of the tunica media of the muscular arteries?
40 layers of smooth muscle cells (connected with gap junctions)
How is vasoconstriction stimulated in muscular arteries?
- Noradrenaline released by nerve endings
- Diffuses through fenestrations into external tunica media
- Depolarise superficial smooth muscle cells
- Depolarisation propagated by gap junctions
In strenuous exercise what happens to the blood flow through arterioles to the intestine?
It decreases by constriction (after a big meal the opposite will occur)
What are the individual muscle cells called in metarterioles?
Precapillary Sphincters
What is the role of Precapillary Sphincters?
Control blood flow to the capillary bed
Where do the lymphatic vessels return excess ECF to the blood stream?
At the internal jugular and subclavian veins
What are pericytes? And what is their function?
Cells that are present on the outer surface of capillaries.
They are capable of dividing into muscle cells and fibroblasts
How do fenestrated capillaries differ from continuous capillaries?
There are pores in the endothelium
How do sinusoid capillaries differ from fenestrated capillaries?
There are larger pores
How is the pressure in the Post-capillary veins important?
It insures fluid flows into them from capillaries and surrounding tissue
What is the general rule about the diameter of a vein and its accompanying artery?
Larger in the vein
Give a few examples of Large Veins
Vena Cava, Pulmonary, Portal, Renal, Internal jugular, iliact and azygous
What is special about the tunica adventitia in large veins?
It contains longitudinally orientated smooth muscle (as well as the circular muscle in tunica media)
What is diffusion affected by?
- Area available
- Diffusion Resistance (difficulty or movement through barrier)
- Conc Gradient
