Capillaries and Veins

Question 1

How big are capillaries?

Answer 1

Microscopic

Question 2

What do capillaries connect?

Answer 2

Arterioles to venules, endothelium, and basement membrane

Question 3

Where aren’t there capillaries?

Answer 3

cornea, lens, epidermis, cartilage

Question 4

Where are there few capillaries?

Answer 4

Tendons and ligaments

Question 5

Where are there lots of capillaries?

Answer 5

brain/nervous tissue; endocrines system; kidneys

Question 6

What are the three kinds of capillaries?

Answer 6

Continuous capillaries
Fenestrated capillaries
Sinusoid capillaires

Question 7

Where are continuous capillaries found?

Answer 7

Found in most tissue, eg skeletal muscle

Question 8

Describe the basement membrane of a continuous capillary. How are the endothelial cells held together?

Answer 8

Basement membrane forms a continuous ring around capillary

Endothelial cells are held together by tight junctions

Question 9

What special structure is found in the endothelial cells of continuous capillaries?

Answer 9

intercellular clefts

Question 10

How big is the intercellular cleft in a continuous capillary? What can pass through it? Where aren’t they?

Answer 10

~4 nm wide
Glucose and other small solutes can get through the clefts
The capillaries in the brain do not have these clefts- because of blood brain barrier

Question 11

What is a fenestrated capillary and why is it named as such?

Answer 11

These endothelial cells have filtration pores (windows),

Question 12

How big are the windows in a fenestrated capillary, and what covers them?

Answer 12

~20-100 nm, often spanned by a glycoprotein membrane

Question 13

Where are fenestrated capillaries found?

Answer 13

Found in kidneys, endocrine glands, small intestine

Question 14

Describe the basement membrane of a fenestrated capillary

Answer 14

surrounds the fenestrated capillaries

Question 15

Where are sinusoid capillaries found?

Answer 15

Found in liver, bone marrow, spleen

Question 16

What does a sinusoid capillary look like?

Answer 16

There are spaces in between the endothelial cells

Basement membrane in incomplete or absent

Question 17

Why do sinusoid capillaries have space between the endothelial cells?

Answer 17

These spaces allow things like albumin, clotting factors, etc to get into the blood (from the liver/marrow/spleen where they are produced)

Question 18

What are the three specialized structures in the capillary bed?

Answer 18

Metarteriole
Thoroughfare channel
Precapillary sphincter

Question 19

Where is the metarteriole?

Answer 19

Short, 1st section of the thoroughfare channel to venule, when an arteriole gives off a branch to a capillary bed area

Question 20

What surrounds the met metarteriole?

Answer 20

Has isolated smooth muscle fibers around this short section

Question 21

Where is the thoroughfare channel?

Answer 21

Longer section, from metarteriole to venule

Is the continuation of the metarteriole, capillaries come off this part

Question 22

Where does the thoroughfare channel go? What can it act as?

Answer 22

Will empty to a venule- Sometimes acts as a shunt, if precapillary sphincters are closed

Question 23

How many capillary beds come off the thoroughfare channel?

Answer 23

Usually 10-100 capillary beds are supplied off this channel

Question 24

What is the pre capillary sphincter?

Answer 24

Smooth muscle wrapped around the beginning of a capillary bed

Question 25

What does the pre capillary sphincter do?

Answer 25

Autoregulation: if theres plenty to O2, will slow blood flow for a short time

Question 26

__of the body’s capillaries are shut down at any given time, because there's not enough ______ to fill everything.

Answer 26

¾ | Blood

Question 27

Several _____ unite to form a venule

Answer 27

capillaries

Question 28

Will a vein ever be as thick as an artery?

Answer 28

No

Question 29

How many layers does a vein have? Which is the thickest?

Answer 29

3 | Tunica adventitia

Question 30

How to veins prevent back flow? Where are these structures located?

Answer 30

Have valves to prevent the backflow of blood, only on tunica intima

Question 31

What two "pumps" allow for veinous return?

Answer 31

Skeletal Pump | Respiratory Pump

Question 32

What is the skeletal pump?

Answer 32

In the legs when the skeletal muscle contracts, blood is pushed up towards the heart

Question 33

What is the respiratory pump?

Answer 33

During respiration, the diaphragm flattens and moves downwards, this decreases pressure in the thoracic cavity, increases pressure in abdominal cavity, and blood will flow to an area of lower pressure- returning to the thoracic cavity

Question 34

What is hemostasis?

Answer 34

Cessation of bleeding

Question 35

What is a thrombus?

Answer 35

A blood clot that develops in the luminal wall of a blood vessel

Question 36

What is a thrombosis?

Answer 36

Clotting in an unbroken blood vessel

Question 37

What is hemophilia?

Answer 37

A genetic disorder, clotting is diminished or absent

Question 38

What is an embolus?

Answer 38

“A mass” A substance that is carried in the blood and obstructs a blood vessel eg an air bubble, a blood clot, a fat globule

Question 39

What is an aneurysm?

Answer 39

A sac formed by the dilation of a wall of an artery or vein

Question 40

What are the "layers" of blood flow called?

Answer 40

Laminar flow

Question 41

Describe laminar flow

Answer 41

Blood in the middle of an artery flows faster than blood near the walls, due to friction The diameter of a vessel has a powerful influence on blood flow velocity

Question 42

In addition to laminar flow, what also impacts blood flow?

Answer 42

Viscosity and peripheral pressure

Question 43

What does MAP stand for?

Answer 43

Mean arterial pressure

Question 44

What is MAP?

Answer 44

Pressure that propels blood to tissues A measure of stress on blood vessels Since diastole lasts longer than systole, it’s not just an average of the two

Question 45

How is MAP determined?

Answer 45

``` MAP = Diastolic pressure + ⅓( Pulse Pressure) Pulse pressure: Systolic-Diastolic MAP = Diastolic pressure + ⅓(Systolic-Diastolic) ```

Question 46

What is hypertension?

Answer 46

Abnormally high BP | Chronic resting BP higher than 140/90 mmHg

Question 47

What is atherosclerosis?

Answer 47

Tearing of endothelium due to pressure, causes lesions that lead to lipid deposits along the walls of vessels

Question 48

What is hypotension?

Answer 48

Chronic systolic pressure below 100mmHg

Question 49

What is net filtration/reabsorption pressure?

Answer 49

The difference between fluids entering/exiting capillaries

Question 50

What is hydrostatic pressure?

Answer 50

Fluid filters out of the arterial end of a capillary | The physical force exerted by blood against the capillary wall

Question 51

What is colloidal osmotic pressure?

Answer 51

Fluid osmotically reenters at the venous end of capillary | Albumins primarily responsible for re entry of fluid back into capillary

Question 52

How, where, and in what percents is fluid reabsorbed?

Answer 52

Capillaries reabsorb 85% of fluid they filter, remaining 15% absorbed/returned by lymphatic system