Ch 21 - Blood Vessels/Circulation Flashcards
(106 cards)
1
Q
what is the overall goal of the cardiovasc. sys.?
A
to transport O2 and nutrients to the tissues of the body
- eg. carbohydrates, lipids, vitamins, and proteins
then remove CO2 and metabolic wastes from the body
- eg. lactate, urea, creatine
2
Q
The Cardiovasc. Sys. consists of
A
- the heart
- blood vessels
- blood
3
Q
What is the heart?
A
a muscular pump that moves the blood through a circuit of vessels throughout the body
4
Q
Purpose of blood?
A
- serves to transport gases, nutrients, electrolytes, and buffers within the vessels
- plays a role in immunity
5
Q
Arteries - direction of flow
A
move primarily oxy blood AWAY from the heart
6
Q
Veins - direction of flow
A
move primarily deoxy blood TOWARD the heart
7
Q
Capillaries
A
allow for transport of gases and nutrients into and out of the blood
8
Q
Systemic Circulation
A
- supplies the tiss of the body with nutrient/oxy rich blood
- beginning in left ventricle, blood is pumped out the aorta to the tiss where gas exchange occurs
- deoxy blood returns to the right atrium via the superior/inferior vena cava
9
Q
Pulmonary Circulation
A
- deoxy blood is pumped by the right ventricle through the pulmonary arteries to the capillaries of the lunges where it is oxy-ed (in alveoli)
- oxy-ed blood returns to the left atrium of the heart through the pulmonary veins
10
Q
Cardiac Perfusion
A
- the delivery of oxy-rich blood to the heart muscle (myocardium) through the coronary arteries, which branch off the aorta
- due to extreme pressure in heart during contraction, the heart only receives blood during relaxation (ventricular diastole)
11
Q
Largest vein
A
superior/inferior vena cava
12
Q
Largest Artery
A
aorta
13
Q
if an artery is carring oxy blood, it is part of ___ circulation
A
systemic
14
Q
if an artery is carrying deoxy blood it is part of _____ circulation
A
pulmonary
15
Q
Layers of Blood vessels
A
- Tunica externa
- Tunica media
- Tunica intima
16
Q
How many layers do BVs have
A
3
17
Q
what is the hallow part of the BV called?
A
lumen
18
Q
Vasoconstriction
A
contraction of circular smoot muscle in walls of BVs, decreases vessel diameter
19
Q
Vasodilation
A
relaxation of smooth muscle, increases vessel diameter
20
Q
BV increased diameter is
A
vasodilation
21
Q
BV decreased diameter
A
vasoconstriction
22
Q
What regulates the degree of constriction
A
- largely controlled by sympathetic ANS (Norepinephrine) input to BVs
- controlled by medulla oblongata autonomic nuclei in brain stem
23
Q
What part of brain regulates vessel constriction
A
medulla oblongata (autonomic nuclei) in brain stem
24
Q
why does the medulla oblongata regulate constiriction of vessels
A
because it is the cardiovascular center of the brain
25
is BV constriction controlled by ANS or SNS
ANS sympathetic
26
is BV constriction controlled by sympathetic or parasymp.
sympathetic ANS
27
Tunica Intima
- one lay of **endothelial cells**
- **reduces friction** b/w vessel walls and blood
28
How does **Tunica Intima** differ in Artery/Vein
A: usually round, w/ relatively thick wall
V: usually flattened/collapsed, w/ relatively thin wall
29
Tunica Media
- made of **smoot muscle and elastic tiss**,
- controls **vasoconstriction/dilation**
30
How does **Tunica Media** differ in Artery/Vein
A: thick, dominated by smoot muscle cells and elastic fibers
V: thin, dominated smooth muscle cells and collagen fibers
31
Tunica Externa
- composed of **collagen**
- protects, reinforces, and **anchors the vessel** to surrounding structures
32
How does **Tunica Externa** differ in Artery/Vein
A: collage and elastic fibers
V: Collagen and elastic fibers and smooth muscle cells
33
Arteries
- contain large amounts of **elastin** which enable the vessels to withstand and smooth out pressure fluctuations due to heart action
34
How does **Endothelium** differ in Artery/Vein?
A: usually rippled, due to vessel constriction
V: often smooth
35
How does **Internal Elastic Membrane** differ in Artery/Vein?
A: Present
V: Absent
36
How does **External Elastic Membrane** differ in Artery/Vein?
A: Present
V: Absent
37
Are veins thin or thick?
Thin - b/c of low BP
38
Why do Vein walls tend to be thinner?
because of they DON'T carry high pressure blood
39
What pressure blood do veins carry?
Low pressure blood
40
Why do veins have thinner walls than arteries?
Veins **do not carry high pressure blood** so their walls are **thinner**, but they still contain **smooth muscle** and are capable of **vasoconstriction**
41
Types of Arteries
1. Elastic Arteries
2. Muscular Arteries
3. Arteriole
4. Continuous Capillary
42
what type of artery has thickest tunica media
Muscular artery
43
Elastic Arteries
- largest arteries
- includes: **aorta and pulmonary trunk**
44
Functions of Elastic Arteries
1. transports large volumes of blood away from the heart
- function as a **pressure reservoir**, momentarily storing mechanical energy; transmit energy to kepp blood moving after semilunar valves close)
2. Provides resilience, recoils & dampens the changing pressure due ventricle systole and diastole
45
Tunica Media in Elastic Arteries
- high density of elastic fibers
- relatively little smooth muscle
46
Muscular Arteries
- typically 4.0-0.5mm
- **thickest tunica media** with **lots of smooth muscle**
47
Function of Muscular Arteries
- carrying blood to skeletal muscles and organs
- are important as *pressure points* = points that can be pressed against a bone to reduce bleeding
48
Arterioles
- branch within organs
- **some tunica externa or absent**
- tunica media: 1 or 2 layers of smooth muscle
49
Tunica Media in Arterioles
- 1 or 2 layers of smooth muscle
50
Functions of Arterioles
- control **local distribution** of blood to capillary beds
51
Arterioles are also called
Resistance Vessels
- constriction of arterioles increase **resistance**
52
What can help regulate BP
systemic (body-wide) constriction/dilation of arterioles
53
Vessel constriction will
increase BP
54
Blood pressure
pressure exerted by blood on BV walls
55
Constriction/dilation of arterioles controlled by:
1. local conditions
2. sympathetic
3. endocrine stimulation
eg. low O2 conditions can stimulation local and/or sympathetic directed dilation
56
Capillaries
- microscopic, barely wider than the diameter of a RBC, (8um)
- form extensive branching entworks through most tissues
57
Capillary Structure
- consists of an endothelial tube inside a delicate basal lamina
- simple squamous epithelial cells are joined loosely due to absence of tight junctions except in blood-brain barrier
58
Function of Capillaries
2 way exchange
(only vessel with **thin enough walls** to allow diffusion)
59
Major Types of Capillaries
1. Continuous
2. Fenestrated
3. Sinusoid
60
Continuous Capillaries
- most common
- endothelial cells are arranged in **single layer = thin wall** OR **multi layer = thick wall**
- spaces b/w cells allow H2O, ions, amino acids & lipid soluble substances to move through
- may also be vesicular transport from one side to another = **pinocytosis**
61
Fenestrated Capillaries
- endothelial cells pores = **fenestra** allows **exchange of H2O, solutes & peptides**
62
Examples of Fenestrated Capillaries
- choroid plexuses of the brain
- small intestine villi
- endocrine glands, renal (kidney) glomeruli
63
Sinusoids
- similar to fenestrated capillaries, plus gaps b/w adjacent endothelial cells
- basal lamina; allows exchange of H2O, ions, WBCs & plasma proteins
64
Basal Lamina in Sinusoids
allows exchange of H2O, ions, WBCs & plasma proteins
65
Examples of Sinusoids
- plasma proteins produced in liver enter bloodstream and phagocytes exit
66
Diapedesis
- Emigration
- when a cell moves in/out of vessel
67
What is most common capillary
Continuous
68
Where can you find fenestrated capillaries
- intestines
- kidney
- hypothal
- pituitary gland
- choroid plexus
69
Where can you find Sinusoid Capillaries
- liver
- spleen
- bone marrow
- endocrine organs
70
Arterial Anastomosis
Artery fused to artery
71
what is vasomotion?
the **cyclic contraction and relaxation** of BV **smooth muscle**, regulating blood flow and pressure through vasoconstriction/dilation
72
Role of **Precapillary Sphincter**
- band of smooth muscle at entrance to capillary
- constriction - **reduces flow/diverts flow** to other branches
OR
- dilation - **increases flow** into capillary
73
What is Precapillary Sphincter controlled by
local chemical factors
ie. concentration of solutes and dissolved gases (eg. O2 lvls)
74
Vasomotion
constriction/dilation of precapillary sphincters several times per minute that changes the blood flow through capillary beds
75
Types of Veins
1. Venules
2. Medium Sized Veins
3. Large Veins
76
Venules
- smallest - 20 um
- most **lack** a **tunica media**
77
Medium Sized Veins
- 2-9mm internal diameter
- tunica media thin, few muscle cells
- **thickest layer is tunica externa** = longitudinal bundles of **elastic and collagen** fibers
78
Large Veins
- includes superior/inferior vena cava
- all tunica layers present
- tunica media: **slender**
- tunica externa: longitudinal bundles of **collagen and elastin**
79
Functions of Veins
1. low resistance vessels to **return blood to heart**
2. blood reservoir
80
Why are veins called **Capacitance Vessels**?
because they act as **blood reservoirs**, holding large amounts of blood due to their thin walls and high distensibility (expandability)
81
Why can veins accommodate large changes in blood volume?
veins have **thin walls and less smooth muscle** than arteries, making them more expandable (distensible)
82
How much more can veins stretch or recoil compared to arteries?
8x more due to flexible walls
83
Which is more able to stretch or recoil, veins or arteries?
Veins, 8x more able
84
Distensible
expandable
85
Veins contain what percent of all blood?
64%
86
Venoconstriction
compression/constriction of veins
87
what part of brain causes **venoconstriction** in the event of hemorrhaging
**vasomotor center** in the **medulla oblongata**
88
Factors influencing flow through veins
1. Low pressure in Right Atria
2. Gravity - helps move blood **from above heart** when upright, gravity overcomes BP in venules/veins
3. Sympathetic Input to smooth musc. in veins **(vasoconstriction)** - controlled by **medulla oblongata**
4. "Muscular Pump"
- veins contain valves every few cm. when surrounding skeletal musc. contracts: squeezes the blood towards the heart. **Valves** prevent backflow when muslces relax
5. Respiratory Pump
89
why do veins require assistance in returning blood to heart?
low BP in veins
90
What is the importance of valves in Veins
prevent backflow when muscles relax
91
Where is pressure greatest?
aorta
92
blood flows from ______ __ ______ pressure
high to low
93
The pressure gradient is generated by ______
ventricular systole (contraction)
94
How does the **respiratory pump** aid blood from through veins?
during inhalation, pressure in the **thoracic cavity drops**, reducing pressure in the thoracic veins and **pulling blood toward the heart**, improving **venous return**
95
Varicose Veins
enlarged, twisted veins that occur when **vein valves weaken** or fail, causing blood to **pool** and veins to become **swollen and visible**.
often seen in the legs
96
Risk Factors of Varicose Veins
1. **Age** - loss of vein elasticity, gets stretched out
2. **Obesity** - increased pressure in veins
3. **Pregnancy** - increased blood volume
4. **Female** - hormones relax veins
5. **Standing/Sitting for long periods of time** - slower blood flow
6. **Family History**
97
what is BP measured in
mmHg (mercury)
98
ave pressure in large arteries
70-100 mmHg
99
Venous pressure
- pressure in veins
- 18 to 2 mmHg just before entrance to heart
100
Change in Pressure
driving force that moves blood through the sys.: 100mmHg
101
Pressure from large arteries to vena cavae
65mmHg
102
Capillary Hydrostatic Pressure (CHP)
same as **capillary BP**
blood pressure in capillaries
- starts at 35mmHg arterial side
- drops to 18mmHg venous side
103
What is Capillary BP at start of arterial side
~35mmHg
104
What is Capillary BP venous side
drops to ~18mmHg
105
Total Peripheral Resistance (TPR)
**resistance to flow** encountered by the **entire cardiovasc. sys.**
106
