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Histology > Circulatory System > Flashcards

Circulatory System Flashcards

1
Q

What is the circulatory system?

A

a series of tubes designed to carry

fluids from one part of the body to another

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2
Q

What are the two types of circulatory systems?

A

Cardiovascular

Lymphatic

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3
Q

What is the cardiovascular system?

A

distribute blood throughout the body utilizing the heart as pump

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4
Q

What is the function of the cardiovascular system?

A

major system for transporting gases, nutrients, wastes, hormones and
immune system components throughout body

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5
Q

What is the lymphatic system?

A
  • independent of the pumping action of the heart (uses gravity and muscular contractions)
  • collect surplus tissue fluid (lymph)
  • returns lymph to cardiovascular system after first filtering lymph in nodes
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6
Q

What is the function of the lymphatic system?

A

1) collect surplus tissue fluid (lymph)

2) returns lymph to cardiovascular system after first filtering lymph in nodes

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7
Q

What are the 3 types of cardiovascular circulation?

A

Pulmonary
systemic
Portal

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8
Q

What is pulmonary circulation?

A

Deoxygenated blood is pumped from the right ventricle to the lungs where it
is oxygenated prior to returning to the left atrium

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9
Q

What is systemic circulation?

A

Oxygenated blood is pumped from the left ventricle to the tissues of the body
and subsequently the deoxygenated blood returns to the right atrium

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10
Q

What is portal circulation?

A

1) Situation where a vein or arteriole is positioned between two capillary beds
2) Occurs in the liver, pituitary gland and kidney

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11
Q

What What are the 3 layers that make up the blood vessel walls?

A

Tunica intima
Tunica media
Tunica adventitia

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12
Q

What is the tunica intima?

A

Innermost lining of the blood vessel wall closest to lumen

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13
Q

What is the tunica intima composed of?

A

1) endothelium - simple squamous epithelium
• one layer of flattened cells lining the lumen of each blood vessel
2) basement membrane
3) subendothelial CT (variable in thickness, unsually unseen)
4) fenestrated internal elastic lamina

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14
Q

Where are fenestrated internal elastic lamina found?

A

Tunica intima but only in arterial vessels

Tunica media

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15
Q

What is the function of fenestrated internal elastic lamina?

A
  • fenestrations allow for diffusion from lumen

- elasticity is needed for accommodating increased hydrostatic pressure

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16
Q

What is the tunica media?

A

Middle layer of blood vessel wall

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17
Q

What is the tunica media composed of?

A

circular smooth muscle
• variable in thickness but always thicker in arteries than companion veins
fenestrated laminae of elastic fibers interspersed among smooth muscle cells
fenestrated external elastic lamina (not always obvious)

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18
Q

What is the tunica adventitia?

A

Outermost layer of blood vessel

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19
Q

What is the tunica adventitia composed of?

A

1) loose to dense irregular CT running mostly longitudinally along vessel wall
• blends with CT surrounding the vessel
• often thickest tunic in veins and venules
2) sometimes scattered smooth muscle cells mixed into the CT
3) Vasa vasorum
4) Nervi vascularis

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20
Q

What is vasa vasorum?

A

1)Supplies vascular needs to outer portion of vessel wall and the inner portion of the vessel wall is accomodated by luminal diffusion
2) Most prevalent in larger vessels
(large veins have more extensive vasa vasorum than arteries due to blood quality)

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21
Q

What is Nervi vascularis?

A

1) network of autonomic nerves regulating smooth muscle contraction
* vasoconstriction is active contraction of smooth muscle in tunica media
* vasodilation is generally passive and occurs in the absence of neural input

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22
Q

Where is most smooth muscle found?

A

walls of tubes and in hollow viscera

blood vessel walls, GI tract, urinary bladder, etc.

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23
Q

How is smooth muscle commonly arranged?

A

Arranged in sheets or layers surrounded by connective tissue

(one layer is circumferential and the other is longitudinal

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24
Q

Where is the neurovascular supply found in smooth muscle?

A

Found in surrounding connective tissue

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25
Q

What causes contractions in smooth muscle to occur?

A

Responses to mechanical, neural and chemical stimuli

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26
Q

What is the function of smooth muscle?

A
  • Regulate luminal diameter of most body tubes

- Peristaltic contractions to move luminal contents distally in these tubes

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27
Q

What is the morphology (appearance) of smooth muscle?

A
  • Long tapered cell (spindle-shaped); no striations
  • Single central rod-shaped nucleus (elliptical
  • most organelles located in area around nucleus (devoid of contractile filaments)
  • no T system but sarcoplasmic reticulum is present
  • gap junctions are widespread to facilitate spread of membrane excitation
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28
Q

What is different about smooth muscle contraction in comparison to skeletal muscle contraction?

A
  • thin, thick and intermediate filaments are present but not in sarcomeres
  • smooth muscle specific actin (has tropomyosin but no troponin
  • Smooth muscle specific myosin - binds actin when phosphorylated
  • No Z lines are present in smooth muscle cells
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29
Q

What happens upon excitation of smooth muscle?

A

Calcium is released from sarcoplasmic reticulum

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30
Q

What occurs after the calcium is released in smooth muscle?

A

Calcium binds to calmodulin

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31
Q

What occurs after the calcium binds with calmodulin in smooth muscle?

A

The calcium-calmodulin complex activates a myosin kinase

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32
Q

What occurs after the myosin kinase is activated in smooth muscle?

A

Myosin gets phosporylated and can bind to actin

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33
Q

True or false, Smooth muscle can maintain tonus almost indefinately?

A

True smooth muscle are able to have sustained ontraction

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34
Q

what is the latch state of smooth muscle?

A

ATPase activity of myosin is decreased when dephosphoylated

- comparable to rigor mortis in skeletal muscles

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35
Q

what are dense bodies in smooth muscle?

A
  • Equivalent to Z lines in smooth muscle
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36
Q

Where are dense bodies (focal densities) of smooth muscle found?

A

Scattered throughout cytoplasm and some associated with cell membrane

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37
Q

What is the function of dense bodies in smooth muscle?

A

Thin and intermediate filaments extend between dense bodies

  • strong cable-like system is created between dense bodies
  • harnesses pull generated as as thin filaments slide past thick filaments
  • transmits pull to cell membrane and cell shortens resulting in contraction
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38
Q

How do smooth muscle grow and regenerate?

A
  • smooth muscle can hypertrophy in response to increased demand
  • smooth muscle is mitotic and can increase its numbers (hyperplasia)
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39
Q

What muscle has the greatest regenerative capacity?

A

Smooth muscle

40
Q

What do arteries and arterioles do?

A

Conduct blood away from heart and deliver it to tissues

- creates a relatively high capillary pressure on the arterial side of the capillary beds

41
Q

What do veins and venules do?

A

Collect blood from tissues and return it to heart

- beginning from a relatively low capillary pressure on the venous side of the capillary beds

42
Q

What are elastic arteries?

A

Aorta (and its large branches) and pulmonary arteries

43
Q

What are the 3 layers that make up arteries?

A

Tunica intima
Tunica media
Tunica adventitia

44
Q

What is the tunica intima of elastic arteries?

A
  • Endothelium with associated basement membrane
  • subendothelial CT (relatively thick with elastic fibers)
  • internal elastic lamina
45
Q

What is the tunica media of elastic arteries?

A

Thickest portion of arterial wall

  • up to 50 or more layers of fenestrated elastic laminae
  • similar number of smooth muscle layers arranged circularly
46
Q

What is the tunica adventitia of elastic arteries?

A

Usually less than half the thickness of the tunica media
- ordinary CT with elastic fibers
Vasa vasorum and nervi vascularis

47
Q

What is systolic blood pressure?

A

results from ventricular contraction

48
Q

What is diastolic blood pressure

A

results from elastic recoil of elastic arteries

49
Q

What is an aneurysm?

A

Permanently dilated thin-walled artery which is prone to rupture

  • elastic fibers in Tunica media degenerate and are replaced by collagen fibers
  • these vessels lose their ability to recoil after systole (permanently dilated)
50
Q

What are muscular arteries?

A
  • Elastic arteries merge into muscular arteries by losing most elastic laminae
  • these arteries represent most of the named arteries in gross anatomy
  • muscular arteries are highly contractile under ANS control
  • blood flow can be regulated in response to functional demands
51
Q

What is the tunica intima of muscular arteries?

A

Thinner than tunica intima in elastic arteries but same qualities as tunica intima in elastic arteries

52
Q

What is the tunica media of muscular arteries?

A

Many layers of circular smooth muscle (2-40)

External elastic lamina often indistinct

53
Q

What is the tunica adventitia of muscular arteries?

A

Approximately the same thickness as the tunica media

- ordinary connective tissues (presence of vasa vasorum dictated by vessel size)

54
Q

What are arterioles?

A

Arterial vessels having an overall diameter of 100 micrometers or less (about a dozen RBCs)

55
Q

what arterial vessel is the prime controller of systemic blood pressure?

A

The arterioles via vasoconstriction or vasodilation.

  • precapillary sphincters can completely stop blood flow within a capillary
  • blood flow is regulated by neural (autonomic) and hormonal stimulation
56
Q

What is in the tunica intima of arterioles?

A

Endothelium (essentially no subendothelial connective tissue)
Internal elastic lamina should still be present

57
Q

How many layers of circular smooth muscle are found in the tunica media of arterioles?

A

1-2 layers

58
Q

What does the tunica adventitia of arterioles contain?

A

thin, ill-defined layer of ordinary CT

59
Q

What are capillaries?

A

Site of gaseous and fluid exchange
- small thin walled vessels with luminal diameter of 8-10 micrometers
- consist of an endothelial layer supported by a basement membrane
• sometimes pericytes are present (fibroblast/smooth muscle precursor)
are not found singly but rather are in networks called capillary beds
• humans are estimated to have 50,000 miles of capillaries

60
Q

What make up capillary endothelial cell junctions?

A

Zonula occludens

Fascia occludens

61
Q

What are zonula occludens of Capillary Endothelial Cell Junctions ?

A
  • complete tight junctions
  • eliminates free passage between endothelial cells
  • present in capillaries in brain (blood-brain barrier)
62
Q

What are Fascia occludens Capillary Endothelial Cell Junctions?

A
  • incomplete tight junctions
  • create slit-like openings between endothelial cells allowing for free passage
  • present in capillaries in most areas of body
63
Q

What are the types of capillaries?

A

Fenestrated (type II) capillaries
Continuous (type I) capillaries
Sinusoidal (type III) capillaries

64
Q

What are fenestrated (Type II) capillaries?

A
  • endothelial cell cytoplasm has fenestrations (80 - 100 nm diameter)
  • pinocytotic vesicular transport is used to a lesser degree
  • fenestrations may result from a pinocytotic vesicle(s) spanning the thin endothelial cell cytoplasm and opening simultaneously on both sides of the cell
  • typically seen in the Gl mucosa, renal glomeruli and endocrine glands
  • number of fenestrations is directly correlated with absorptive activity of tissue
65
Q

What are continuous (type I) capillaries?

A

• endothelial cell cytoplasm is unfenestrated
• found with fascia occludens in most body tissues (muscle, skin, CT, lungs)
• found with zonula occludens in the central nervous system
• transport across endothelium is mediated by pinocytic vesicular transport
* presumably bidirectional transport

66
Q

What are sinusoidal (type III) capillaries?

A
  • lumen is much larger than the other capillary types (-30 micrometers)
  • large gaps exist between endothelial cells
  • basement membrane is incomplete or lacking
  • found in liver, spleen and bone marrow
67
Q

What causes tissue fluid buildup?

A

• the capillary pressure in the arterial end of the capillary bed causes a dialysate of blood to pass between capillaryendothelial cells (tissue fluid)
• the remaining protein macromolecules in ‘blood plasma then exert an osmotic pressure drawing interstitial fluid back to vessels at venous side of the capillary
bed

68
Q

What is the problem with tissue fluid?

A

o Rate of production exceeds rate of resorption back into vascular system

69
Q

What is the solution of tissue fluid?

A

o Requires a 2nd set of circulatory vessels (lymphatics) to collect excess tissue
fluid (lymph) and deliver it back to blood vascular system

70
Q

What is the arteriovenous anastomoses or AV shunts?

A
  • not all arteriole blood necessarily flows through a capillary bed
  • shunt blood directly from arteriole to venule
  • characteristically found in skin and function in thermoregulation
71
Q

What happens if the AV shuntsmooth muscle contracts?

A
  • blood flows to the superficial capillary beds

* enhances heat loss

72
Q

What happens when AV shunt smooth muscle relax?

A
  • blood flows through AV shunt (diverting away from the capillary beds)
  • helps to conserve body heat
73
Q

In general, how are veins in comparison ?

A

o Veins have thinner walls than the companion artery

o Veins have a larger, more irregular lumen than the companion artery

74
Q

What are venules?

A
  • slightly wider, thin-walled capillary outflow vessels (up to 200 micrometers)
  • usually no tunica media (at most only a few smooth muscle cells
    a this is the vessel from which diapedesis occurs (circulating cells enter tissue)
  • endothelium here is the principal site of action for hist mine (mast cells)
75
Q

What are mast cells?

A

closely related to basophils (circulating white blood cell)

76
Q

What is the morphology (appearance) of mast cells?

A
  • highly granulated cell typically found near blood vessels throughout body
  • seen most easily in lab on the slides from stomach, jejunum or urinary bladder
77
Q

What do mast cell cytoplasmic granules contain?

A
  • heparin -weak anticoagulant
  • histamine-inflammatory agent (causes BV dilation, endothelial contraction)
  • chemotactic factors for neutrophils and eosinophils
78
Q

What is the function of mast cells?

A
  • degranulation leads to the formation of “leaky” endothelium
  • promotes the infiltration of serum components into the tissue space
79
Q

What are veins?

A
  • thinner walled and larger luminal diameter than companion arteries
  • vary in diameter from 1 mm to 4cm
80
Q

What is found in the tunica intima of veins?

A
  • endothelium

* no internal elastic lamina

81
Q

What is found in the tunica media of veins?

A

• much thinner than the tunica media in a companion artery
• usually a thin layer of circular smooth muscle
- thick in the superficial veins of the lower extremity (e.g., great saphenous)
- helps promote venous return in the absence of surrounding skeletal muscle

82
Q

What is found in the tunica adventitia of veins?

A

• usually the thickest layer in the wall of a vein (thicker than tunica media)
• ordinary CT with vasa vasorum and nervi vascularis
- veins typically have more abundant supply of vasa vasorum than arteries

83
Q

What are flap valves?

A
  • semilunar leaflets covered by endothelium
  • permit blood flow in only one direction
  • venous return is greatly facilitated by skeletal muscle contraction
84
Q

What are varicose veins?

A
  • results from incompetence of the valves

- allows blood to pool in veins of the lower extremities

85
Q

What is the endocardium?

A
  • equivalent to tunica intima
  • endothelium lines chambers and covers valves
  • subendothelial CT with some smooth muscle
  • subendocardial layer-deeper layer of CT
    • contains the impulse conduction system in the heart
86
Q

What is the myocardium?

A
  • equivalent to tunica media
  • thick layer of cardiac muscle
    • thicker in the ventricles than in the atria
87
Q

What is epicardium?

A
  • equivalent to tunica adventitia
  • fibroelastic CT containing the coronary vasculature
    • commonly contains adipose
  • covered on the outer surface with a mesothelium (visceral layer of pericardium)
88
Q

What is the function of the lymphatic system?

A
  • collect excess tissue fluid from the interstitial fluid compartment (lymph)
  • filter lymph through lymph nodes and then return it to the bloodstream
  • immunologically react to potentially harmful antigenic materials
89
Q

What occurs when the lymph flows through the lymphatic system?

A
  • unidirectional
  • lymph collects in lymphatic capillaries
  • lymph passes from these capillaries through vessels of increasing diameter ultimately
    reaching one of two main lymphatic ducts (thoracic duct or right lymphatic duct)
90
Q

What are lymphatic capillaries?

A

Resemble blood capillaries but differ in the following ways:
• often are much wider than the typical blood capillary
• basement membrane is incomplete or lacking
• one end of lymphatic capillary begins blindly
• have anchoring filaments
- collagen fibrils tethering the endothelial cells to the surrounding CT

91
Q

What are lymphatic vessels?

A
  • not easily distinguishable from small or medium sized veins
  • reliable clue is the absence of blood cells except occasional lymphocytes
    • endothelial lining always present
    • usually has an irregular luminal shape
92
Q

What do the medium and large lymphatic vessels contain?

A
  • have the usual three tunics but they are difficult to discern
  • larger vessels have valve leaflets
93
Q

How is lymph propelled through vessels?

A
  • peristaltic contractions of the smooth muscle in the wall
  • external compression due to pulsation in adjacent blood vessels
  • external compression by skeletal muscle contraction (greatest effect)
94
Q

What is lymphedema?

A
  • persisting regional edema

- may indicate certain lymphatic vessels have become chronically obstructed

95
Q

What are possible causes of lymphedema?

A
  • trauma
  • surgical excision of lymphatics
  • blockage by certain parasites
  • lymphatic blockage due to cancer cells spreading from malignant tumor
96
Q

Are lymphatic vessels an easy method for spreading of infectious agents and cancer cells?

A

lymphatic vessels are open channels that almost invite the spread of infectious agents and cancer cells (mechanism for metastatic spread)

Histology (9 decks)

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