Lecture 7

Question 1

Why do we have a circulatory system?

Answer 1

An evolutionary consequence of an increase in size and complexity of a multicellular organism
Provides a steep concentration gradient from the blood to cells for nutrients, and from cells to blood for waste products

Question 2

What is the primary function of the circulatory system?

Answer 2

Distribution of gases and molecules for nutrition, growth and repair

Question 3

What are the secondary functions of the circulatory system?

Answer 3

Enables hormonal signalling
Dissipates heat
Mediates inflammatory and host defence responses

Question 4

What are the three basic functional parts?

Answer 4

a pump = the heart
a fluid = the blood
a set of containers = the blood vessels (and lymphatic system)

Question 5

What nervous system mediates the circulatory system?

Answer 5

ANS

Question 6

What can affect the ANS and be affected by the ANS?

Answer 6

Sleep/wake
Body position
Rest/exercise
Digestion
Emotional stress

Question 7

How is the systemic circuit aligned?

Answer 7

Parallel pathways are from left to right
Usually flows through a single capillary bed
Can have two capillary beds in series
Can have capillary beds in parallel and series

Question 8

What are the two capillary beds in series?

Answer 8

kidneys, hepatic systems

Question 9

What are parallel series of capillary beds?

Answer 9

spleen, intestines, and liver

Question 10

How is the pulmonary circuit aligned?

Answer 10

Single pathway from right to left side of heart

Question 11

What structure does the microcirculation have?

Answer 11

Can include capillaries and smaller venules and arterioles

Question 12

What are the number of vessels in the aorta, capillaries and vena cava?

Answer 12

Aorta: 1
Capillaries: 40 billion
Vena cava: 1

Question 13

What is the cross sectional area in the aorta, capillaries and vena cava?

Answer 13

Aorta: 4cm2
Capillaries: 2.8 * 10(-7) cm2
Vena cava: 6cm2

Question 14

What is the aggregate cross sectional area in the aorta, capillaries and vena cava?

Answer 14

Aorta: 4
Capillaries: 2827
Vena cava: 6

Question 15

What are the velocities in the aorta, capillaries and vena cava?

Answer 15

Aorta: 21 cm/s
Capillaries: 0.03 cm/s
Vena cava: 14 cm/s

Question 16

What are the three layers of the blood vessel?

Answer 16

Tunica intima
Tunica media 
Tunica externa (adventita)

Question 17

What is the structure of the tunica intima?

Answer 17

Endothelial cells resting on a basement membrane
Have junctions of 10-15nm
BM: keeps capillaries more structured
Has valves to prevent backflow of blood (located over heart)

Question 18

What is the structure of the tunica media?

Answer 18

Smooth muscle cells
Elastic fibers: elastin core covered by microfibrils
Varies composition based on vessel
Allow vessels to stretch and recoil (elastin)

Question 19

What is the structure of the tunica externa?

Answer 19

Collagen fibers
Elastic fibers
Vasa varosum = blood supply for vessels
Nerves = sympathetic nerves

Question 20

What are elastic fibers useful for in large arteries?

Answer 20

High compliance: walls stretch easily without tearing in response to an increase in pressure
Enables vessels: aorta to cope with peak ejection pressures
Recoil of elastic fibers forces blood to keep moving even when the ventricles are relaxed

Question 21

What are smooth muscle useful for in medium-sized arteries?

Answer 21

Smooth muscle cells are arranged circumferentially
Capable of greater vasoconstriction and vasodilation to adjust the rate of blood flow
Vascular tone - state of partial contraction maintains vessel pressure and efficient flow

Question 22

What are terminal regions of arterioles known as?

Answer 22

Metarterioles

Question 23

What do precapillary sphincters do?

Answer 23

Monitor blood flow into the capillary

Question 24

How do precapillary sphincters conduct their function?

Answer 24

Locals regulations by metabolites; low oxygen, high CO2, low pH=vasodilation

Question 25

What are extrinsic regulations by the ANS?

Answer 25

Vasoconstriction: nonadrenaline activates alpha-1 adrenoceptors Vasodilation: reduced release of noradrenaline, increase of calcium activates smooth muscle

Question 26

What are the capillaries composed of?

Answer 26

Endothelial cells and basement membrane

Question 27

Continuous capillaries have interendothelial junctions 10-15nm wide. What are their functions?

Answer 27

Keeps many substances in the blood; | Amino acids that act as neurotransmitters from causing adverse neuronal effects

Question 28

Where is fenestra found in?

Answer 28

Where extensive molecular exchange occurs

Question 29

What are places where extensive molecular exchange occurs?

Answer 29

Small intestine Kidneys endocrine glands

Question 30

What is the function of fenestra?

Answer 30

Allows larger molecules to pass

Question 31

Where are sinusoidal found in?

Answer 31

Liver and bone marrow

Question 32

What is the structure of postcapillary venules?

Answer 32

porous

Question 33

What do postcapillary venules do?

Answer 33

Participate in exchange sites for nutrients and waste

Question 34

Are muscular venules more muscular than arterioles?

Answer 34

no

Question 35

What do the thin walls in venules allow?

Answer 35

Expansion ; | excellent reservoirs for blood

Question 36

What do large veins have to prevent back flow?

Answer 36

valves

Question 37

What to defective, leaky valves lead to?

Answer 37

Varicose veins

Question 38

Where are varicose veins prominent in?

Answer 38

Legs

Question 39

What can varicose veins lead to?

Answer 39

Big bulges Can cause pain, especially after standing Deep vein thrombosis

Question 40

Why do we need a lymphatic system?

Answer 40

More filtration than absorption occurs, leaving 3L of fluid and 150g of protein per day in the interstitial fluid

Question 41

What is the amount of flow of fluid in protein in the lymphs?

Answer 41

Fluid: 2-4 L/day Protein: 95-195 g/day

Question 42

What is the amount of fluid and protein that enters the capillary from the lymphs?

Answer 42

Fluid: 16-18 L/day Protein: 5g/day

Question 43

What is the amount of fluid and protein that leaves the capillary into the lymphs?

Answer 43

Fluid: 20 L/day Protein: 100-200 g/day

Question 44

What are the three primary functions of the lymphatic system?

Answer 44

1. Drains excess interstitial fluid, maintaining the circulating volume of blood 2. Transports dietary lipids 3. Carries out immune responses

Question 45

Where are lymphocytes produced?

Answer 45

lymphatic valves

Question 46

What are the three basic functional parts of the lymphatic system?

Answer 46

1. lymph 2. lymphatic vessels 3. lymphatic tissue containing lymphocytes, found in a number of structures and organs

Question 47

What is the main organ of the lymphatic system?

Answer 47

spleen

Question 48

What is the structure of the lymphatic capillaries (initial lymphatics)?

Answer 48

More leaky than blood capillaries | Possess interendothelial junctions called Primary Lymph Valves

Question 49

What is the structure of lymphatic vessels (collecting lymphatics)?

Answer 49

Endothelium plus sparse smooth muscle Similar to small veins Possess secondary lymph valves that restrict backflow Uses hydrostatic pressure which is lower than interstitial fluid: opened interendothelial junctions Vessels compressed by muscles for higher pressure and junctions are shut

Question 50

Is there communication between the blood vessels and the lymphatic vessels?

Answer 50

yes

Question 51

Where does lymph drain?

Answer 51

subclavian

Question 52

What is a disorder in the lymphatic system?

Answer 52

Lymphoedema

Question 53

What can lymphoedema lead to?

Answer 53

Ineffective drainage and excessive fluid buildup

Question 54

What can ineffective drainage and excessive fluid buildup caused by lymphoedema present as?

Answer 54

Balloon like limbs compression tissue loses elasticity