The Systematic Circulation, Blood Vessels, and Capillary Networks Flashcards
Open systems are systems in which…
the heart pumps blood to the tissues in closed arteries, without a venous return.
Closed systems are systems in which…
blood never leaves the vessels.
What are the five fluid systems in the body?
- Blood Vascular System;
- Lymphatic System;
- Cerebrospinal Fluid;
- Coelomic / Peritoneal Fluid
- Interstitial Fluid.
The two main functions of the blood system is to:
- Transport to the cells the materials necessary for their metabolism and synthesis
- The transportation away of the waste products of cell activity
____________ and _____________ must be supplied to the cells and _____________ and _______________ removed.
Oxygen and nutrients; carbon dioxide and nitrogenous wastes
Blood vessels are the structures that ____________; in mammals these are divided into _________________ (Hint: 3 things)
carry out transport; arteries, capillaries, and veins
How would you list the direction of transport in the blood vascular system?
Aorta –> arteries –> arterioles –> metarterioles –> arterial capillaries –> venous capillaries –> venules –> veins –> Vena Cava
The walls of arteries and veins have three layer, what are they?
Tunica Intima; Tunica Media; Tunica Adventitia/ Externa
In large arteries such as the aorta there is little…
muscle in the media and it mostly consists of sheets of elastic tissue.
Medium sized arteries have lots of…
smooth muscle in the media.
Nerve supply from the sympathetic nervous system enabling…
the control of blood flow.
Veins are similar to arteries in structure, but the walls are…
thinner and have less smooth muscle and elastic tissue.
Medium sized veins have ______ in the ________.
Valves, lumen
Both large arteries and veins have their own blood supply called the…
Vasa vasorum
Capillaries, the smallest vessels, are formed of…
a single layer of endothelial cells, 8-10m thick, without any smooth muscle.
It is rare for any cell to be more than _________ from a capillary.
20-30 micrometers
Capillaries tend to be arranged in…
capillary beds
Only about ____ of blood volume is in the capillaries at a time.
5%
The arteriole divides into a number of…
met-arterioles which do not have a continuous smooth muscle coat.
Blood passes through the met-arterioles and enterers the capillary bed via the
precapillary sphincters
What can precapillary sphincters do?
These can close off the circulation to the capillary bed.
Blood does not flow continuously through the capillary beds because…
in most organs only a small number of capillaries are filled.
Besides the capillary beds, direct connections called _____________________ shunt blood rapidly from the arterial to venous side.
preferential channels or arteriovenous anastomoses
Most cells obtain their nutrient and oxygen requirements via the…
Interstitial fluid
The blood volume is about 8% body weight: typically…
5-6 L male and 4-5 L female
Vasomotion is a __________________ of contraction and relaxation of the precapillary sphincters.
rhythmic myogenic activity
True or False: The met-arterioles and precapillary sphincters are not innervated.
True
The oxygen levels in local tissues are autoregulated. How would this be explained in regards to the level of O2?
Decreased O2 → smooth muscle relaxation, increased O2 → smooth muscle contraction.
Blood consists of two main fractions –
fluid plasma and blood cells
Plasma is a watery fluid containing about…
8% solids (protein is 7%) and 92% water
Major blood vessels (e.g. arteries) are water-tight and therefore…
fluid cannot leak out them.
However, considerable quantities of the liquid portion of the plasma leave the arterial capillaries due to…
the pressure of the fluid in the capillary (‘capillary hydrostatic pressure’ = blood pressure).
This liquid enters the interstitial space and is then called…
interstitial fluid
The capillaries behave as if they are ‘porous’; and they do have…
pores/fenestrae
_________________ substances leave the capillary.
Water and also small molecular sized
Most proteins cannot escape due to size of the pores, but some do leave probably by ______________.
pinocytosis
Instead, most of the filtered fluid is absorbed back into the capillaries due to the…
osmotic pressure of proteins in the plasma.
The filtration and absorption of fluid across the capillary wall is known as…
fluid exchange.
Four pressures are involved in the fluid exchange with the capillary bed. Inside the capillary there are 2 opposing pressures which are ____________________________________. Outside the capillary (within the tissue) there are 2 additive pressures which are ______________________________.
Inside capillary:
- Capillary hydrostatic pressure, 25 mmHg -tends to force fluid out.
Is different in arterial or venous capillaries - Plasma colloid osmotic pressure, 28 mmHg - pulls fluid back in.
Outside capillary:
- Interstitial fluid pressure, 6.3 mmHg - [negative] sucks fluid out.
- Interstitial fluid colloid osmotic pressure, 5 mmHg - fluid out.
Net body filtration rate =
1.7 - 3.5 ml/min or 2.5 - 5.0 litres/day.
Diffusion occurs in both directions and is estimated for the entire body capillary network at…
240 litres/minute
Net loss 10% total volume, passes into…
lymphatic system.
Net filtration pressure is the…
tendency for plasma to leave the blood at the arterial end of a capillary = 8.3 mmHg
Diffusion is the most important process for trans-capillary exchange of…
solutes and solvents.
