Health Science 2211-Lecture 3
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what are the 3 layers that blood vessel consists of?
- tunica interna
- tunica media
- tunica externa
what are the 3 layers in the tunica interna? Briefly describe each.
- endothelium: continuous with endocardium of heart
- Basement membrane: provides physical support for endothelial layer
- Internal elastic lamina: thin layer of elastic tissue
what are the 2 layers in the tunica media? Briefly describe them.
- smooth muscle cells and elastic tissue: give blood vessel structure
- external elastic lamina: another layer of elastic tissue
what is the function of the tunica media and how does in differ between blood vessels?
- controls the diameter of the vessel
- thinner in veins than in arteries
what does the tunica externa consist of, what is it supplied with and what is it's function?
- consists of elastic and collagen fibers
- supplied with nerves and blood vessels (vasa vasorum)
- function is to anchor vessels to surrounding tissue
what are 4 functions of endothelial cells?
- block passage of large molecules out of lumen, into tissues
- prevent coagulation
- control vascular smooth muscle cells
- various roles in inflammation, repair
what do the endothelial cells interact with? (3)
- basement membrane
- other endothelial cells
what are the 4 function of smooth muscle?
- give blood vessel structure
- helps regulate blood flow/pressure
- maintains extracellular matrix by building and secreting elastin, collagen
- can proliferate to repair damaged blood vessel
what are the 2 main circulations?
- pulmonary circulation: short loop runs from right side of heart to the lungs and back to the heart
- Systematic circulation: long loop from left side of the heart to all parts of the body and back to heart
what are the 3 ways that blood return back to the heart?
- superior venae caveae
- inferior venae caveae
- coronary sinus
Why do pulmonary arteries have a larger diameter, thinner walls and less elastic tissue than systematic tissue?
less pressure is needed to move blood through the lungs (less distance less resistance)
Arterioles, capillaries and venules are collectively referred to as?
what is one thing different regarding structure in arteries compared to veins? what are the 2 types of arteries?
- arteries have a thick tunica mediaelastic arteries (conducting arteries)
- muscular arteries (distributing arteries)
contraction of smooth muscle, squeezing the vessel wall and narrowing the lumen of the blood vessel
smooth muscle fibers relax and lumen diameter increases
Describe the structure of elastic arteries and what is its function?
- has more elastic fibers and less smooth muscle
- able to receive blood under pressure and propel it onward
- function as a pressure reservoir
why are elastic arteries also called conducting arteries?
because they conduct blood from the heart to medium sized muscular arteries
Describe the structure of muscle arteries and what is it's function?
- medium-sized arteries with more smooth muscle than elastic fibers in tunica media
- function is modifying the diameter to adjust rate of flow through vasoconstriction and vasodilation
why are muscular arteries also called distributing arteries?
because they direct blood flow and distribute blood to specific parts of the body
what are arterioles and what are its 2 functions?
very small arteries (microscopic) that regulate blood flow into capillaries and in altering arterial blood pressure
what is the structure for arterioles closer to the capillaries? (3)
contain endothelium, smooth muscle cells, and a thin layer of connective tissue
what are capillaries and what is it's function?
- microscopic vessels that connect arterioles to venules
- function in exchange of nutrients and wastes between blood and tissue fluid
what is the structure of capillaries? (2)
endothelium and basement membrane
describe the structure of venules and what cannot it withstand?
- have thin walls that do not readily maintain their shape
- not designed to withstand high pressure
Blood flow through body tissues, also called tissue perfusion is involved in (5)?
- delivery of O2 nutrients & water throughout body and removal of wastes from tissue cells
- gas exchange in lungs
- absorption of nutrients in digestive tract
- urine formation in kidneys
- maintaining body temperature in skin
what is blood flow?
volume of blood moving past a point in a given amount of time
Blood flows from a region of______ pressure to _____ pressure
High to low
The greater the _____________the greater the blood flow.
the more _________ the less blood flow.
What are 4 factors that affect blood flow?
- blood pressure
- vascular resistance to flow
- venous return
- velocity of blood flow
What is blood pressure and what is caused by?
- pressure exerted by blood walls of a vessel
- caused by contraction of ventricles (ventricular systole)
what is a regular blood pressure?
Increasing what 2 factors increases your arterial blood pressure?
Increasing cardiac output and increasing resistance
What is vascular resistance?
the force opposing the flow of blood due to friction of blood and the vessel walls
what two mechanisms can be powerful regulators of blood pressure??
vasoconstriction and vasodilation
What does blood viscosity depend on and how does it increase blood pressure?
- depends mostly on ratio of red blood cells to plasma (fluid) volume
- high viscosity=high resistance=high blood pressure
How does being obsess increase your chance of blood pressure?
being over weight increases the total blood vessel length, which creates more resistance which leads to increased blood pressure
Most of the pressure driving the return of blood to the heart comes from _________________.
left ventricular contraction
when standing, ________ opposes flow up to heart, almost overcoming upward pressure.
What are 2 supplementary pumps that help out with venous return?
- skeletal muscle pump
- respiratory pump
how does the respiratory pump help with venous return? (in regards of breathing and the diaphragm)
- breathing helps bring blood back to the heart
- the movement of the diaphragm downward creates an area of lower pressure around the heart, and an area of higher pressure in the abdomen, which pushes blood up to the heart
what is the function of valves in large veins on the legs?
prevents the backflow of blood
how does the skeletal muscle help with venous return?
as skeletal muscles contract, they compress the veins allowing the valves above the contracting muscle in the skeletal muscle pump to open and allow blood to move to the heart
what is the function of valves above the contracting muscle in the skeletal muscle pump?
the open allowing blood to move toward the heart
what is the function of valves below the contracting muscle in the skeletal muscle pump?
are forced closed, preventing backflow of blood to the capillaries
what is the velocity of blood in arteries,veins and capillaries?
- fastest in arteries/aorta
- slowest in capillaries
- increases speed again in veins
what are the 2 systemic regulation of blood pressure?
what are the 2 auto-regulation of blood pressure?
what are the 4 inputs to the cardiovascular center in the brain?
- from diff parts of the brain: anticipation of competition, increase in body temperature
- proprioceptors: input during physical activity
- Baroreceptors: changes in pressure withing blood vessels
- Chemoreceptors: monitor concentration of chemicals in the blood
what is the output from the cardiovascular center? (3)
- Heart rate increases or decreases
- contractility of the heart can increase or decrease
- Blood vessels can go through vasoconstriction or vasodilation
how are hormones used for regulation of blood pressure?
increase secretion of urine ---> decreases blood volume ---> which decreases blood pressure
how do metabolic controls, control regulation of blood pressure? (2)
- local factors can cause change in each capillary bed (increases in activity of an organ will increase blood flow to that organ)
- vasoactive substances released from cells alter vessel diameter
In myogenic controls of regulation of blood pressure, myogenic responses of arteriolar vascular smooth muscle keep tissue perfusion ________________?
constant despite most fluctuations in systemic blood pressure
what is passive stretch?
- increased intravascular pressure
- promotes increased tone and vasoconstriction acting to resist the initial passive stretch
what is reduced stretch?
promotes vasodilation and increases blood flow to tissue
An example of long term auto-regulation of blood pressure is angiogenesis? when does is occur?
- occurs when short-term auto-regulation cannot meet tissue nutrient requirement
- number of vessels to a region increases and existing vessels enlarge
what is a pulse?
pressure waves caused by the expansion and recoil of arteries
what is systolic pressure?
peak arterial pressure during heart contraction
what is diastolic pressure?
minimum arterial pressure between contractions, when the heart expands and refills
One way to measure blood pressure is through the auscultatory method. what is it?
using a sphygmomanometer and stethoscope
Blood pressure cycles over a ______________.
24 hour period
when does blood pressure peak and what are some things that can increase blood pressure?
- blood pressure peaks in the morning due to levels of hormones
- age, sex, weight, race, mood, and physical condition may vary BP
Blood pressure increases with ___________ resistance and _________ cardiac output.
what is hypotension? what is it often associated with?
- low blood pressure
- associated with long life and lack of cardio vascular illness
what is hypertension? where is it more persistent?
- high blood pressure
- often persistent in obese people
what are the 3 types of hypotension?
- orthostatic hypotension
- chronic hypotension
- acute hypotension
what is orthostatic hypotension?
temporary low BP and dizziness when suddenly rising from sitting position
what is chronic hypotension?
- hint of poor nutrition and warning sign Addison's disease
- low protein decreases viscosity of the blood
what is acute hypotension?
important sign of circulatory shock
what is shock? what does it result in?
- failure of the cardiovascular system to deliver adequate amounts of oxygen and nutrients to body tissues
- results in cells and tissue becoming damaged or dying
what are the 4 types of shock? Briefly describe each.
- Hypovolemic shock: due to decreased blood volume ex. hemorrhage
- cardiogenic shock: due to poor heart function
- vascular shock: due to excessive vasodilation (causes drop in BP, ex. allergies)
- Obstructive shock: due to obstruction of blood flow (ex. embolism)
what number is defined as hypertension?
what is primary hypertension?
- 90-95% of all cases
- elevated BP that cannot be attributed to any particular organic cause
what is secondary hypertension?
- 5-10% of all cases
- identifiable underlying cause such as obstruction of renal flow
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