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BMS 460 > Microcirculation > Flashcards

Microcirculation Flashcards

1
Q

describe the normal circulatory pattern

A
  • start in the heart
  • high pressure to large arteries, need elastic arteries to accommodate for this
  • as arteries get smaller, need resistance, so need muscular arteries
  • then reach capillaries, gas exchange
  • into venules and veins, where pressure is low
  • back to the heart (pre-load) - I think this relates to how venous filling of the heart affects the pressure with which blood is pumped into the arteries
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2
Q

what is the pathway of blood vessels that a red blood cell would travel through?

A

left ventricle –> elastic artery –> muscular artery –> arteriole –> capillary –> small venule –> large venule –> vein –> right atrium
- this is a continuous circuit!!

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3
Q

what happens to elastic and muscle tissue as you go from large to small arteries?

A

going from large to small arteries, amount of elastic tissue decreases and amount of smooth muscle increases

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4
Q

what happens to the intima, media, and adventitia as you go from arteries to veins?

A

intima: stays the same
media: decreases (so veins can have thinner walls and therefore better compliance, and arteries can have thicker/more muscular walls for resistance)
- adventitia: increases (sort of a “wall” so veins don’t collapse due to low pressure)

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5
Q

where do all functions of the circulatory system occur?

A

capillary beds! (the rest of the system consists of two pumps (the heart) and associated plumbing)

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6
Q

define microcirculation

A

network of small blood vessels, the smallest of which are capillaries

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7
Q

what are the three routes that blood can take when traveling from arterioles to venules?

A
  1. true capillaries: normal capillaries where gas exchange occurs (can be continuous, fenestrated, or discontinuous)
  2. metarterioles: direct blood to thoroughfare channels and play a role in thermoregulation
  3. thoroughfare vessels: shunts that allow blood to bypass the capillary system, so no gas exchange will occur
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8
Q

where are thoroughfare channels commonly found?

A
  • skin of nose, lips, and external ear
  • submucosa of nose and alimentary canal
  • erectile tissue of sexual organs
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9
Q

describe the role of precapillary sphincters

A
  • precapillary sphincters are bands of smooth muscle before capillaries
  • when they are dilated, blood will flow into true capillaries. heat can be lost during this process
  • when they are constricted, blood will instead flow into metarterioles and then through thoroughfare channels. heat can be conserved during this process
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10
Q

are all capillary beds supplied at all times?

A

blood is supplied to all parts of the body at all times, but all capillary beds do not contain blood at all times!

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11
Q

describe continuous capillaries

A
  • endothelial cells have a continuous cytoplasm and basal lamina
  • calveolae (invaginations in membranes) and vesicles transport substances across the cytoplasm in a bidirectional pathway
  • this means we have transcytosis and pinocytosis (there are no gaps between cells that molecules can be transported through, so have to go through endothelial cells themselves).
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12
Q

define transcytosis

A

things to through cells: endocytosis, transport across cell, exocytosis on the other side

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13
Q

define pinocytosis

A

cell takes in fluid that has nutrients in it via vesicles

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14
Q

describe fenestrated capillaries

A
  • have pores (fenestrae) in the cytoplasm with or without diaphragms
  • this basically means there are gaps between the endothelial cells and there is not a continuous cytoplasm
  • this allows for substantial fluid transport
  • the basal lamina however is continuous
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15
Q

what are diaphragms in fenestrated capillaries?

A
  • membranes between the endothelial cells that basically open and close for the transport of certain substances
  • fenestrated capillaries without a diaphragm are characteristic of the renal glomerulus, so the continuous basal lamina constitutes an important permeability layer in this case
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16
Q

describe discontinuous capillaries

A
  • like fenestrated capillaries, but contain larger cytoplasmic gaps and a discontinuous basal lamina
  • an example of discontinuous capillaries is the venous sinusoids of the liver, spleen, and bone marrow
17
Q

what are sinusoids?

A
  • larger capillaries (discontinuous) found in the liver, spleen, and bone marrow
  • in these structures, blood goes from arterioles to sinusoids to venules
18
Q

describe two special capillary arrangements

A
  1. in the kidney: afferent arteriole drains into capillary network called the glomerulus (essential for blood filtration) then into an efferent arteriole, and then into another capillary network called the vasa recta (essential for reabsorption of substances into blood/urine formation), which surrounds the loop of Henle
  2. hypothalamo-anterior pituitary portal system: capillary bed in the hypothalamus pools into another capillary bed (through veins) in the anterior pituitary first before going to the heart
19
Q

where are continuous capillaries found?

A
  • brain
  • bone
  • lung
  • muscle
20
Q

where are fenestrated capillaries found?

A
  • renal tubules
  • small intestinal mucosal villi
  • endocrine glands
21
Q

where are discontinuous capillaries found?

A

venous sinusoids of liver, spleen, and bone marrow

22
Q

describe the overall function of the lymphatic system

A

fluid goes from vascular compartment to tissue and from tissue to vascular compartment, but not all fluid gets reabsorbed into the blood. the rest goes into lymphatic capillaries and is then transported back to the bloodstream via the subclavian veins

23
Q

how much lymph is transported over a 24 hour period as compared to total blood volume?

A

roughly the same amount

24
Q

what drives movement of fluid from interstitial fluid to lymphatic system?

A
  • hydrostatic pressure!
  • there is no osmotic pressure because protein and other solutes can flow freely through the lymphatic vessel wall since it is fenestrated with no basal lamina at all
25
Q

how is the lymphatic system a one-way street?

A
  • lymphatic capillaries are blind, meaning the endothelial cells are overlapping. hydrostatic pressure pushes the flaps open so fluid can go from interstitium into lymphatic capillaries. when pressure build up in the capillaries, it pushes the flaps shut so there is no backflow back into the inserstitial space
  • there are also semilunar valves throughout the lymphatic vessels that prevent backflow
26
Q

describe lymph fluid

A
  • similar to plasma, but contains more lymphocytes
27
Q

overall functions of the lymphatic system

A
  • return excess proteins and interstitial fluid to the blood
  • filter and destroy unwanted material from body fluids
  • initiate an immune response
28
Q

outline the steps of lymphatic circulation

A
  1. excess interstitial fluid flows into blind-ending capillaries with one-way mini-valves as pressure build up in tissues
  2. lymphatic capillaries join to form larger vessels with valves to ensure unidirectional flow of lymphatic fluid
  3. lymphatic vessels periodically interrupted by lymph nodes, which filter lymph and allow lymphocytes to enter lymph to get into general circulation
  4. lymph vessels get back to the general circulation via the subclavian veins
    - note: lymphatic capillaries in the intestinal villi absorb and transport most lipids as chylomicrons, and the cleansed lymph is collected in the cysterna chyli at the distal end of the thoracic duct
29
Q

which lymph vessels drain where?

A
  • vessels of the upper right quadrant drain into the right lymphatic duct, which goes into the right subclavian vein
  • the rest of the lymphatic vessels drain into the thoracic duct in the upper abdomen and thoracic cavity, which drains into the left subclavian vein
30
Q

describe histology of lymphatic capillaries

A
  • irregular outline
  • spaced endothelial cell lining lacking tight junctions
  • no red blood cells in the lumen
31
Q

describe lymph nodes

A
  • found primarily in the neck, axilla (armpit), thorax, abdomen, and groin
  • contain lots of B and T lymphocytes and macrophages
  • lymph fluid flows through the nodes in a way that allows the immune cells to filter, detect, and react to foreign material
32
Q

what happens to lymph nodes when responding to foreign invaders?

A
  • they become tender and palpable
  • painless nodes, on the other hand, are usually malignant
33
Q

how to examine potentially malignant histology of lymph nodes?

A

destruction of normal architectural pattern of lymph nodes is indicative of metastasis (most lymphomas and metastatic foci destroy lymph node architecture as they grow)

34
Q

what do inflammatory/infectious conditions do to lymph nodes?

A

can modify and distort the architecture, but do not efface/destroy it like metastasis does

35
Q

list the primary lymphoid organs

A

-bone marrow
-thymus

36
Q

list the secondary lymphoid organs

A
  • lymph nodes
  • spleen
  • tonsils
  • mucosa-associated lymphoid tissue (MALT)
    –> bronchus-ALT
    –> gut-ALT (peyer’s patches)
37
Q

types of lymphocytes

A
  • B cells
  • T cells
  • NK cells (wbc’s - natural killer cells)
38
Q

accessory cells in the lymphatic system

A
  • monocyte-derived: macrophages and dendritic cells
  • cells of mesenchymal origin: follicular dendritic cells
39
Q

mononuclear phagocyte system: list the macrophages in the brain, neck, lung, liver, spleen, kidney, joint, blood, lymph node, and skin

A
  • brain: microglial cells
  • neck: cervical lymph nodes
  • lung: alveolar macrophages
  • liver: kupffer cells
  • spleen: macrophages
  • kidney: mesangial phagocytes
  • blood: monocytes
  • lymph node: resident and circulating macrophages
  • skin: langerhans cells

BMS 460 (35 decks)

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