27/10/2021, 01:01 OneNote
Circulatory System (Module)
Monday, 23 April 2018 15:39
• Anatomy of vasculature
• Forms a closed delivery system that begins and ends at heart
• Total length of blood vessels = 160,000 km
• Controlled by sympathetic nervous system (not parasympathetic)
• Type of blood vessels
• Arteries (carry blood away from the heart)
• Elastic arteries → conducting vessel
• Muscular arteries → distributing vessel
• Arterioles → resistance vessel
Elastic artery Muscular artery** Arteriole
Diameter 1 - 2.4 cm 0.3 - 1 cm 10 μm - 0.3 cm
Location Near the heart Distal to elastic Distal to muscular
artery artery
Diagram
•
Structural High elastic Thick tunica media Thin walls
characteristic content* (mainly tunica media)
Function Use elastic recoil to Change diameter to Change diameter to
conduct blood change blood flow change resistance
• *Windkessel effect (windkessel - "air chamber")
• **The majority of arteries in human body are muscular arteries
• Capillaries (connect tissue cells) → exchange vessel
• Length = 1 mm
• Diameter = 8 - 10 μm
Continuous capillary Fenestrated capillary Sinusoidal capillary
Location Skin Active filtration (kidney) Liver
Muscles Absorption (small intestine) Bone marrow
Lungs Endocrine gland Spleen
Central nervous system Adrenal medulla
The The most common Moderate The most limited
number
Diagram
•
Blood flow Rapid (smooth linings) Moderate Slow (rough linings)
Permeability Low Moderate High
Structural Endothelial cells joined by Endothelial cells with Large fenestrations (pores)
characteristi tight junctions fenestrations** (pores) Large sinusoids*** (spaces)
c
Function Allow fluids and small solutes Allow large volume of fluids Allow cells and large proteins
to enter or exit* and large solutes to enter or to enter or exit
exit
• *Via either intercellular clefts or vesicles
• Intercellular clefts exist in all types of capillaries except capillaries in the brain
• Vesicles exchange substances through endocytosis or exocytosis
• **Fenestration - "window"
• ***Sinusoid - "cavity"
• Capillary bed
• Terminal arteriole → vascular shunt → postcapillary venule
• Vascular shunt branches to form true capillaries
• Precapillary sphincters controls the blood flow into the true capillaries
• If open, blood enter the true capillaries
• If closed, blood only go through the vascular shunt
•
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• Veins (carry blood toward the heart)
• Small/large vein → capacitance vessel
• Venules
Venule Vein
Diameter 8 mm - 1cm 1 - 1.5 cm
Diagram
•
Structural Thin wall Tunic intima forms valves
characteristi Little smooth muscle Relatively thick tunic externa
c Large lumen
Function Drain capillary beds Return blood to heart
Act as a blood reservoir
(60%)
• Blood vessel wall
• Central space surrounded by blood vessel walls is lumen
•
• Most blood vessels (except capillaries) have three layers (tunics)
Tunics Sub-layers Composition Function
Tunica intima Inner endothelium* Epithelial cell Reduce friction (smooth
Outer basement membrane Connective cell linings)
• Facilitate blood flow
Tunica media Smooth muscle Smooth muscle cell Alter blood vessel diameter
Elastic membrane** Control blood flow
Tunica externa Collagen fibres Connective cell Protect blood vessel
Anchor to surrounding tissues
• *Endothelium is the simple squamous epithelium that lines the lumen of all vessels
• **Allows the blood vessel to stretch and recoil (elastin present in all three tunics)
• Blood vessel Thickness of the wall Size of the lumen Valves
Artery Thick* Small Absent
Vein Thin** Large Present
• *Arteries have thicker media and thinner externa
• **Veins have thinner media and thicker externa
• The blood vessel wall of capillaries is one-layer (tunica intima) (media and externa are absent)
• Major blood vessels
• Features
• The location of arteries are usually deep, while veins are either deep or superficial
• Deep veins tend to run parallel with arteries (and nerves) and share the same names, while superficial veins tend to have distinct names
• Venous pathways are more interconnected than arterial pathways
• Most blood vessels in the head and limbs are bilaterally symmetrical while some of the large, deep vessels of the trunk are asymmetrical or unpaired
• Two major subdivisions of circulatory system
• Pulmonary circuit
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, 27/10/2021, 01:01 OneNote
•
• Systemic circuit
•
•
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Circulatory System (Module)
Monday, 23 April 2018 15:39
• Anatomy of vasculature
• Forms a closed delivery system that begins and ends at heart
• Total length of blood vessels = 160,000 km
• Controlled by sympathetic nervous system (not parasympathetic)
• Type of blood vessels
• Arteries (carry blood away from the heart)
• Elastic arteries → conducting vessel
• Muscular arteries → distributing vessel
• Arterioles → resistance vessel
Elastic artery Muscular artery** Arteriole
Diameter 1 - 2.4 cm 0.3 - 1 cm 10 μm - 0.3 cm
Location Near the heart Distal to elastic Distal to muscular
artery artery
Diagram
•
Structural High elastic Thick tunica media Thin walls
characteristic content* (mainly tunica media)
Function Use elastic recoil to Change diameter to Change diameter to
conduct blood change blood flow change resistance
• *Windkessel effect (windkessel - "air chamber")
• **The majority of arteries in human body are muscular arteries
• Capillaries (connect tissue cells) → exchange vessel
• Length = 1 mm
• Diameter = 8 - 10 μm
Continuous capillary Fenestrated capillary Sinusoidal capillary
Location Skin Active filtration (kidney) Liver
Muscles Absorption (small intestine) Bone marrow
Lungs Endocrine gland Spleen
Central nervous system Adrenal medulla
The The most common Moderate The most limited
number
Diagram
•
Blood flow Rapid (smooth linings) Moderate Slow (rough linings)
Permeability Low Moderate High
Structural Endothelial cells joined by Endothelial cells with Large fenestrations (pores)
characteristi tight junctions fenestrations** (pores) Large sinusoids*** (spaces)
c
Function Allow fluids and small solutes Allow large volume of fluids Allow cells and large proteins
to enter or exit* and large solutes to enter or to enter or exit
exit
• *Via either intercellular clefts or vesicles
• Intercellular clefts exist in all types of capillaries except capillaries in the brain
• Vesicles exchange substances through endocytosis or exocytosis
• **Fenestration - "window"
• ***Sinusoid - "cavity"
• Capillary bed
• Terminal arteriole → vascular shunt → postcapillary venule
• Vascular shunt branches to form true capillaries
• Precapillary sphincters controls the blood flow into the true capillaries
• If open, blood enter the true capillaries
• If closed, blood only go through the vascular shunt
•
https://onedrive.live.com/redir?resid=BA9B41DF6B1FBB85%21162&page=View&wd=target%28NUR1112.one%7Cb192a1a0-d83b-fc4d-b0dd-ea20c8885abe… 1/4
,27/10/2021, 01:01 OneNote
• Veins (carry blood toward the heart)
• Small/large vein → capacitance vessel
• Venules
Venule Vein
Diameter 8 mm - 1cm 1 - 1.5 cm
Diagram
•
Structural Thin wall Tunic intima forms valves
characteristi Little smooth muscle Relatively thick tunic externa
c Large lumen
Function Drain capillary beds Return blood to heart
Act as a blood reservoir
(60%)
• Blood vessel wall
• Central space surrounded by blood vessel walls is lumen
•
• Most blood vessels (except capillaries) have three layers (tunics)
Tunics Sub-layers Composition Function
Tunica intima Inner endothelium* Epithelial cell Reduce friction (smooth
Outer basement membrane Connective cell linings)
• Facilitate blood flow
Tunica media Smooth muscle Smooth muscle cell Alter blood vessel diameter
Elastic membrane** Control blood flow
Tunica externa Collagen fibres Connective cell Protect blood vessel
Anchor to surrounding tissues
• *Endothelium is the simple squamous epithelium that lines the lumen of all vessels
• **Allows the blood vessel to stretch and recoil (elastin present in all three tunics)
• Blood vessel Thickness of the wall Size of the lumen Valves
Artery Thick* Small Absent
Vein Thin** Large Present
• *Arteries have thicker media and thinner externa
• **Veins have thinner media and thicker externa
• The blood vessel wall of capillaries is one-layer (tunica intima) (media and externa are absent)
• Major blood vessels
• Features
• The location of arteries are usually deep, while veins are either deep or superficial
• Deep veins tend to run parallel with arteries (and nerves) and share the same names, while superficial veins tend to have distinct names
• Venous pathways are more interconnected than arterial pathways
• Most blood vessels in the head and limbs are bilaterally symmetrical while some of the large, deep vessels of the trunk are asymmetrical or unpaired
• Two major subdivisions of circulatory system
• Pulmonary circuit
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, 27/10/2021, 01:01 OneNote
•
• Systemic circuit
•
•
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