Chapter 19) Circulatory System Flashcards
1
Q
Blood Vessel Types
A
- Arteries) Carry Blood away from the heart
- Branch to From Capillaries
- Capilalries) branches of arteris that connect tissue cells
- serve cells
- Veins) Carry blood toward the heart
- Converge into larger vessels
2
Q
Structure of Blood Vessel Wall
A
- Lumen) Central Blood Containing space
- Tunica Intimita (Inner Wall Layer) In contact with blood in lumen
- Consists of endothelium that is a simple squamous epithelium that lines vessels
- Continuous with lining of heart
- Subendothelial layer (Basment Membrane) In vessels larger than 1mm, there is a basment membrane that supports endothelium
- Tuncia Media (Middle Wall layer) Smooth muscle and sheets of elastin
- Smooth muscle Controls Vasoconstriction and Vasodilation. Influences blood pressue/flow
- Tuncia Externa (Adventitia) (Outer Wall Layer)
- Contains Collegen to protect and reinforce/ anchor vessels
- Contains nerve fibers and lymphatic vessels
- Vasa Vasorum (vessels of the vessles) noruishes external layer.
3
Q
Elastic Arteries
A
- Large, Thick-walled Arteries neat the heart
- Aorta and major branches
- Elastin is found in all three tunics (wall layers)
- Large Lumens allow for maximum blood flow
- conducting arteries
- Inctive in Vasoconstriction
- Done to keep smooth pressure downstream
4
Q
Muscular Arteries
A
- Deliver blood to body organs
- Branch from elastic arteries
- also called distrubuiting arteries
- Thickest tunica media of all vessels
- More active in vasocontriction
- Less capabile of streatching (less elastin)
5
Q
Arterioles (Resistance Vessels)
A
- Smallest Arteries
- Contain all three tunics, but Tunica Media is mostly smooth muscle
- Leads to capillary beds
- control flow into capilaries via vasodilation and vasoconstriction
- Arteriolar Diameter
- Controls minute-to-minute blood flow
- Varries in response to nueral, hormonal, and local chemical influences
- Diameter = resistance, arterioles are called resistance vessels because they are narrow which means they are more resistant. Slows down blood speed and lowers pressure so capilaries are not damaged
6
Q
Capillaries
A
- Microscopic blood vessels composed of walls of thin tunica intima
- smallest capilareis are one cell wide
- Pericytes) contractile stem cells that can help regenrate scar tissue and stabilize the capibality
- Found in all tissues exexpt for cartlidge, epithelia, cornea, and the lens
- Functions
- Exchange of things (gas, nutrients, wastes, hormones etc) between blood and interstital fluid.
- What are the three types?
7
Q
Continuuous Capillaries
A
- Abundent in skin and muscles
- held together by tight junctions
- there are gaps in membrane called intercellular clefts that allow limited passage of fluids/ small solutes
- Continuous capillaries of brain are unique
- lack inercular clefts which forms blood-brain barrier
8
Q
Fenestrated Capillaries
A
- Endotheial cells contain pores (fenestrations)
- more permiable than continous capillaries
- Function in absorption or filtration
- (small intestines, endocrine glands, and kidneys)
9
Q
Sinsuoid Capillaries
A
- Found only in the liver, bonw marrow, spleen and the adrenal medulla
- Contain large inercellular clefts and fenestrations
- largest type of capilaries because of lack of tight junctions
- Blood flows slowly
- large molcules and blood cells can pass between blood and surrounding tissues
- macropages can rech into clefts to catch bacteria
10
Q
Capillary Beds
A
- Microcirculation and Capillary beds
- Capillaries form interweaving networks called capillary beds
- Networks of capillaries between arterioles and venules is known as microcirculation
- Terminal arteriole > Metarteriole (vessel in between an artriole and capillary)
- Metarteriole > Throughfare Channel (Between capillary and venule)
- Throughfare Channel > Postcapillary Venule (drains bed)
11
Q
Two types of Vessels in Capillaries
A
- Vascular Shunt (Metaertioles and Thoroughfare channels)
- Short vessel that directly connects terminal aereriole and venules
- On each side of bed
- True Capillaries
- 10 to 100 vessels per bed
- Branch off metarteriole or terminal arteriole
12
Q
Blood Flow Through Capillary Beds
A
- Terminal artiole branches into metarteriole. Metatrole branches from true capallaries which branch and retrun to thorghfare channel
- Precapillary Sphincters lie at root of each true capillary to regulate blood flood into the capillaries
- Can be open or closed depending on how much a specific body part needs nutrient delivery/ waste removal
13
Q
Venules
A
- Capillaries unite to form venules
- smallest are postcapillary venules
- Very Porous
- similar to capillaries
- Allow fluids and WBCs into the tissues
- Consists of Endothelium and and a few Pericytes.
- Larger venules have one or two layers of smooth muscle cells.
14
Q
Veins
A
- Venules Join to form Veins. Have larger lumens compared to their corresponding arteries
- results in lower blood pressue than in arteris
- Tunica media is thin
- can be thin because of lower blood pressure
- Tunica Externa is thick and filled wit collegen and elastic networkds
- Veins are called capacitance vessels (blood reservoirs) because they can hold up to 65% of the body’s blood supply.
- Venous Valves) prevent backflow of blood
- most abundent in limbs
- Venous Sinuses) flattened veins with thin walls composed of only epithelium
- Supported by surrounding tissues.
*
- Supported by surrounding tissues.
15
Q
Vascular Anstomoses
A
- Most Organs receive blood from more than one major arterial branch. This forms arterial anastomeses when the same teritory is covered by more than one artery
- ensures an alternate pathway called Collateral Channels for blood to take.
- Occur at joints, abdominal organs, the brain, and the heart
- None in the retina, kindys or spleen (have poorly developed collateral circulation)
- Arteriinovenous anastomoses) Vascular shunts of capillaries
- Venous Anastomoses) common as vains interconnect freely
16
Q
Blood Flow
A
- Volume of blood flowing through a vessel, organ, or entire circulation in a given period
- Measured as ml/min
- Equilivent to Cardiac Output (volume of blood pumped by each venticle)
- Relitvely constant at rest
*
17
Q
Blood Pressure
A
- The force per unit are exerted on the wall of blood vessels
- expressed in mm Hg
- Measured as systemic arterial BP in large arteris near heart
- Hydrostatic Pressure Gradient) diffrences in blood pressure in vascular system
- keeps blood moving from higher to lower pressure and through the body
18
Q
Resistance
A
- Opposition to Flow
- measure of amount of friction blood encounters with vessel walls
- Important sources of resistance
- Blood Viscosity (thickness)(stickiness due to formed elements and plasma proteins)
- Total blood vessel length (More length= more resistance)
- Blood Vessel Diameter. (smaller diameter/vasoconstriction = more resistance)
- Greatest influence on resistance
19
Q
Relationship Between Blood Flow, Pressure and Resistance
A
- Blood Flow (F) is directly proportinal to the diffrence in blood pressure (ΔP) between two points
- ΔP increses, blood flow speeds up
- Blood flowus inversley propotinal to peripheral resistance (R)
- If R increases, blood flow decreases
- F=ΔP/R
20
Q
Systemic Blood Pressure
A
- Pressure generated when pumping action of heart encounters resistance.
- Highest in the Aorta where it declines through the pathway (0mm Hg in right atrium)
- Steepest drop in pressure occurs in arterioles which offer the greates resistance.
