Physio 16

Question 1

Where does the transport of nutrients tissues and removal of cell excreta occur?

Answer 1

Microcirculation

Question 2

These are the tiny blood vessels that control the blood flow to each tissue.

Answer 2

Small arterioles

Question 3

What is identified as the most purposeful function of circulation?

Answer 3

Transporting nutrients to tissues and removing cell excreta

Question 4

Which blood vessels primarily control blood flow to individual tissues?

Answer 4

Arterioles

Question 5

What anatomical feature of capillaries allows for quick and easy interchange of substances between tissues and blood?

Answer 5

Single-layer, highly permeable endothelial cells

Question 6

Approximately how many capillaries are estimated to be in the peripheral circulation of the whole body?

Answer 6

10 billion

Question 7

What is the estimated total surface area of all capillaries in the body?

Answer 7

500 to 700 square meters

Question 8

How far away is it rare for any single functional cell of the body to be from a capillary?

Answer 8

More than 20 to 30 micrometers

Question 9

What is the typical internal diameter of arterioles?

Answer 9

10 to 15 micrometers

Question 10

What is a key difference between arterioles and metarterioles regarding their muscular coats?

Answer 10

Arterioles have a continuous muscular coat, while metarterioles have smooth muscle fibers at intermittent points.

Question 11

How do local conditions in tissues influence blood flow?

Answer 11

By controlling the diameters of the arterioles.

Question 12

How many times does a nutrient artery typically branch before becoming small enough to be called arterioles?

Answer 12

Six to eight times

Question 13

What is the cellular structure of capillary walls described as?

Answer 13

Single-layered and highly permeable.

Question 14

What is the purpose of the high permeability of capillary walls?

Answer 14

To allow quick and easy interchange of water, nutrients, and excreta.

Question 15

In the organization of the microcirculation, how does each organ’s system differ?

Answer 15

It is organized specifically to serve that organ’s needs.

Question 16

What is the name of the smooth muscle fiber that usually encircles a capillary at its origin from a metarteriole?

Answer 16

Precapillary sphincter

Question 17

What is the primary function of the precapillary sphincter?

Answer 17

To open and close the entrance to the capillary.

Question 18

How do venules compare to arterioles in terms of size and muscular coat?

Answer 18

Venules are larger and have a weaker muscular coat.

Question 19

Despite having a weaker muscular coat, why can venules still contract considerably?

Answer 19

Because the pressure in the venules is much less than that in the arterioles.

Question 20

This structure is in close contact with precapillary sphincters, allowing for direct control of local blood flow with the tissues they serve.

Answer 20

Metarterioles

Question 21

Give at least three local tissue conditions that can cause direct effects on the vessels to control local blood flow in each small tissue area.

Answer 21

1. Concentrations of nutrients
2. end products of metabolism
3. hydrogen ions

Question 22

What is the ultramicroscopic structure of typical endothelial cells in the capillary wall composed of?

Answer 22

A unicellular layer

Question 23

What surrounds the unicellular layer of endothelial cells on the outside of the capillary wall?

Answer 23

A thin basement membrane

Question 24

What is the internal diameter of a capillary, and what does this imply about the passage of blood cells?

Answer 24

4-9 micrometers; barely large enough for red blood cells and other blood cells to squeeze through

Question 25

A thin-slit, curving channel that lies between adjacent endothelial cells.

Answer 25

Intercellular cleft

Question 26

What are the two types of "passageways" connecting the interior and exterior of a capillary?

Answer 26

Intercellular clefts and plasmalemmal vesicles (caveolae)

Question 27

Where are intercellular clefts located within the capillary wall?

Answer 27

Between adjacent endothelial cells.

Question 28

What are the minute plasmalemmal vesicles found in endothelial cells also called?

Answer 28

Caveolae

Question 29

What proteins are associated with caveolae formation?

Answer 29

Caveolins

Question 30

Besides caveolins, what other molecules are associated with caveolae?

Answer 30

Cholesterol Sphingolipids

Question 31

What are the proposed roles of caveolae?

Answer 31

Endocytosis and transcytosis of macromolecules

Question 32

How are some plasmalemmal vesicles believed to transport substances across the endothelial cell?

Answer 32

By coalescing to form vesicular channels through the cell.

Question 33

What interrupts the intercellular clefts periodically?

Answer 33

Short ridges of protein attachments.

Question 34

Why are water molecules, water-soluble ions, and small solutes able to diffuse with ease through the intercellular clefts despite their small total surface area?

Answer 34

Because of the rapid rate of thermal motion of these molecules

Question 35

What are caveolae believed to imbibe from the plasma or extracellular fluid?

Answer 35

Small packets containing plasma proteins

Question 36

What does the term "transcytosis" refer to in the context of caveolae?

Answer 36

The transport of macromolecules across endothelial cells

Question 37

What is the general term for the process by which a cell engulfs material from outside the cell, a process caveolae are believed to play a role in?

Answer 37

Endocytosis

Question 38

What is a notable characteristic of the junctions between capillary endothelial cells in the brain?

Answer 38

They are mainly "tight" junctions.

Question 39

What types of molecules are allowed to pass into or out of brain tissues due to the special characteristics of its capillaries?

Answer 39

Only extremely small molecules such as water, oxygen, and carbon dioxide

Question 40

How do the clefts between capillary endothelial cells in the liver differ from those in the brain?

Answer 40

In the liver, they are wide open.

Question 41

How do the pores of the gastrointestinal capillary membranes compare to those of the muscles and the liver?

Answer 41

They are midway between those of the muscles and those of the liver.

Question 42

What are the small oval windows that penetrate through the middle of the endothelial cells in the glomerular capillaries of the kidney called?

Answer 42

Fenestrae

Question 43

This structure allows tremendous amounts of very small molecular and ionic substances to filter through the glomerular capillaries of the kidney.

Answer 43

Fenestrae

Question 44

What important substances are explicitly stated not to filter through the glomeruli via fenestrae?

Answer 44

Large molecules of the plasma proteins (such as albumin)

Question 45

Which organ's capillaries are characterized by "tight" junctions, restricting the passage of most molecules?

Answer 45

Brain

Question 46

Which organ's capillaries are described as having "wide open" clefts between endothelial cells?

Answer 46

Liver

Question 47

True or False. Blood usually flow continuously through the capillaries.

Answer 47

False. Blood flows intermittently through the capillaries, turning on and off every few seconds or minutes.

Question 48

How does blood usually flow through the capillaries? a. Continuously b. Intermittently c. Only during rest d. Only during activity

Answer 48

Intermittently

Question 49

What is the phenomenon called that causes the intermittent flow of blood through capillaries?

Answer 49

Vasomotion

Question 50

What anatomical structures are involved in vasomotion?

Answer 50

Metarterioles and precapillary sphincters (and sometimes very small arterioles)

Question 51

What is identified as the most important factor affecting the opening and closing of metarterioles and precapillary sphincters?

Answer 51

The concentration of oxygen in the tissues

Question 52

When does the intermittent period of capillary blood flow occur more often and last longer?

Answer 52

When tissue oxygen concentration decreases below normal

Question 53

It is the most important means by which substances are transferred between plasma and interstitial fluid

Answer 53

Diffusion

Question 54

What process provides continual mixing between the interstitial fluid and the plasma as blood flows through the capillary?

Answer 54

Diffusion

Question 55

What is the underlying cause of diffusion?

Answer 55

Thermal motion of water molecules and dissolved substances.

Question 56

How do lipid-soluble substances, such as oxygen and carbon dioxide, diffuse through the capillary membrane?

Answer 56

Directly through the cell membranes of the capillary endothelium.

Question 57

Why are the rates of transport for lipid-soluble substances much faster than for lipid-insoluble substances?

Answer 57

Because they can permeate all areas of the capillary membrane.

Question 58

Which of the following substances is explicitly mentioned as being lipid-insoluble and diffusing only through "pores"? a) Oxygen b) Carbon dioxide c) Glucose d) Fats

Answer 58

Glucose

Question 59

What passageways do water-soluble, non-lipid-soluble substances use to diffuse through the capillary membrane?

Answer 59

Through intercellular "pores" (clefts)

Question 60

What is the approximate ratio of the rate at which water molecules diffuse through the capillary membrane compared to the rate at which plasma flows linearly along the capillary?

Answer 60

About 80 times as great.

Question 61

About one sixth of the total volume of the body consists of spaces between cells collectively called as?

Answer 61

Interstitium

Question 62

What do you call the fluid present in the spaces between cells?

Answer 62

Interstitial fluid

Question 63

Give the two major types of solid structures found in the interstitium.

Answer 63

Collagen fiber bundles Proteoglycan filaments

Question 64

Which of the two solid structures found in the interstitium provides most of the tensional strength of the tissues?

Answer 64

Collagen fiber bundles

Question 65

What are proteoglycan filaments found in the interstitium primarily composed of?

Answer 65

About 98 percent hyaluronic acid and 2 percent protein

Question 66

They produce a mat of very fine reticular filaments aptly described as a "brush pile."

Answer 66

Proteoglycan filaments

Question 67

From where is the fluid in the interstitium derived?

Answer 67

By filtration and diffusion from the capillaries

Question 68

What is the "tissue gel" in the interstitium composed of?

Answer 68

Proteoglycan filaments and fluid entrapped within them

Question 69

How does fluid primarily move through the tissue gel? a) By flowing easily in large numbers of molecules. b) By active transport mechanisms. c) By diffusion, moving molecule by molecule by kinetic, thermal motion. d) By osmosis only.

Answer 69

By diffusion, moving molecule by molecule by kinetic, thermal motion.

Question 70

What is the approximate speed of diffusion through the tissue gel compared to free fluid?

Answer 70

About 95 to 99 percent as rapidly

Question 71

What percentage of "free" fluid is normally present in the interstitium?

Answer 71

Less than 1 percent

Question 72

What happens to the "free" fluid in the interstitium when tissues develop edema?

Answer 72

Expand tremendously

Question 73

Give the three main factors determine fluid filtration across capillaries

Answer 73

Hydrostatic pressure Colloid osmotic pressure Capillary filtration coefficient

Question 74

What is colloid osmotic pressure caused by?

Answer 74

Plasma proteins

Question 75

What is the role of the lymphatic system in relation to fluid and protein leakage from capillaries? a) It delivers proteins to the interstitial spaces. b) It filters blood to remove waste products. c) It returns small amounts of excess protein and fluid to the circulation. d) It produces plasma proteins.

Answer 75

It returns small amounts of excess protein and fluid to the circulation.

Question 76

What are the four primary forces that determine fluid movement through the capillary membrane collectively called?

Answer 76

Starling forces

Question 77

Which Starling force tends to force fluid outward through the capillary membrane?

Answer 77

Capillary pressure (Pc)

Question 78

Which Starling force tends to cause osmosis of fluid inward through the capillary membrane?

Answer 78

Capillary plasma colloid osmotic pressure (Πp)

Question 79

Which Starling force tends to cause osmosis of fluid outward through the capillary membrane?

Answer 79

Interstitial fluid colloid osmotic pressure (Πif).

Question 80

What is the average cerebrospinal fluid pressure around the brain of an animal lying on its side?

Answer 80

Approximately +10 mm Hg

Question 81

Known as the “scavenger” system that removes excess fluid, excess protein molecules, debris, and other matter from the tissue spaces

Answer 81

Lymphatic system

Question 82

What do you call the osmotic pressure from that which occurs at the cell membrane?

Answer 82

Colloid osmotic pressure or Oncotic pressure

Question 83

Which tissues is an exception to having special lymph channels for draining excess fluid?

Answer 83

Central nervous system

Question 84

Where do lymph vessels from the lower part of the body eventually empty?

Answer 84

Thoracic duct

Question 85

Approximately what fraction of the fluid filtering from the arterial ends of blood capillaries eventually enters the lymphatic capillaries instead of being reabsorbed into venous ends?

Answer 85

About one tenth

Question 86

What is the normal total quantity of lymph flow per day?

Answer 86

2 to 3 liters

Question 87

Why does fluid that has entered a lymphatic capillary have difficulty leaving it?

Answer 87

Because any backflow closes the flap valve

Question 88

Which two organs contribute about two thirds of all lymph normally, resulting in a higher protein concentration in thoracic duct lymph?

Answer 88

Liver and intestines

Question 89

What is one of the major routes for the absorption of virtually all fats from food?

Answer 89

Lymphatic system from the gastrointestinal tract

Question 90

What happens to bacteria that enter the lymph as it passes through lymph nodes?

Answer 90

They are almost entirely removed and destroyed.

Question 91

What structures exist in all lymph channels that ensure one-way flow?

Answer 91

Valves

Question 92

What happens when a collecting lymphatic or larger lymph vessel becomes stretched with fluid? a) It immediately empties into the blood. b) The smooth muscle in its wall automatically contracts. c) It becomes impermeable to fluid. d) It causes backflow into the capillaries.

Answer 92

The smooth muscle in its wall automatically contracts.

Question 93

What are some external factors that can cause pumping of lymph by intermittently compressing the lymphatics?

Answer 93

Contraction of surrounding skeletal muscles, body movement, and arterial pulsations.

Question 94

How much can lymph flow increase during exercise?

Answer 94

10- to 30-fold

Question 95

What two primary factors determine lymph flow?

Answer 95

Interstitial fluid pressure Activity of the lymphatic pump

Question 96

How does the lymphatic system function as an "overflow mechanism"? a) It stores excess blood volume. b) It produces excess proteins. c) It returns excess proteins and fluid volume from the tissue spaces to the circulation. d) It removes waste products from the blood directly.

Answer 96

It returns excess proteins and fluid volume from the tissue spaces to the circulation.

Question 97

What happens to the colloid osmotic pressure of interstitial fluids when proteins continuously leak out of blood capillaries into the interstitium?

Answer 97

It increases.

Question 98

Lymphatic system plays a central role in controlling ____ (3)

Answer 98

(1) the concentration of proteins in the interstitial fluids (2) the volume of interstitial fluid (3) the interstitial fluid pressure