Blood Vessels Flashcards
Arteries carry oxygenated blood away from heart - red
Veins bring blood back to the heart and carry deoxygenated blood - blue
The heart - Pulmonary arteries carry deoxygenated blood away from the heart into the lungs and pulmonary veins bring oxygenated blood back to the heart.
coming out of the heart - Aorta branching out of aorta are large arteries and branching small aterioroles and then capillaries (gas exchange occurs oxygen that is contain on red blood cells diffuses from the red blood cells into the tissue and where the carbon diocide that’s a by product of cellular metabolism diffuses from the tissue back into the capillary and then head to venules and then ultimately veins, which feed backinto the vena cavae (that bring blood back to the atrium)
Artery - Inner most layer Tunica intima endoepithlium on a loose connective tissue. Resists friction purpose is to smooth the flow of blood, it is gonna be continous with the endocardium (inner most layer of the heart)
Tunica media - smooth muscle and elastic fibers
Tunica externa (outermost layer) - fiberous connective tissue, typically a dense regular connective tissue and has fibers run along the blood vessel in the same direction as the blood vessel and smooth muscle tissues runs circumferentially around the blood vessel, sometimes called the adventitia layer.
Vasa vasaorum tiny blood vessels that supply blood to the tunica media.
Arteriole
Capillary
Venule
Vein
What is the purpose of smooth muscle within the tunica media?
Why is the collagen and elastin present in blood vessels so important?
Purpose is direct blood flow to the body
able to vasocontrict - narrow our pipes
vasodilate - widen our pipes
which allows for the directing of blood flow to different organs and controlled by the sypathetic nervous system.
If we are running in flight, we want to vasodilate open up - the blood vessels that lead to our muscles to make sure that they’re giving a good oxygen supply and then we’re gonna vasoconstrict the blood vessels that will lead to some of our digestive organs because we won’t use it. It also helps increase blood pressure - pressure has to be high in small pipe in order to make it move and bc volume of that pipe is much smaller. Vasocontriction causes an increase in blood pressure in our body where as vasodilation causes a decrease in blood pressure .
Having the collagen and elastin will help the blood vessels expand to accommodate all the blood therefore the heart doesn’t have to work twice as hard.
The elastic in our ateries allows them to expand during a heartbeat diastole when the heart is relaxing the elastic allows the arteries to recoil and releases energy and continues to allow blood to move through the arteries
Types of Arteries
Types of Arteries
- Elastic Arteries (Conducting Arteries)
- Located near the heart
- Lots of elastin
Muscular Arteries
- Supply organs
- Thickest tunica media
- Internal and external elastic membranes
Arterioles (most distal)
- 1-2 layers of smooth muscle cells
- Lumen size dependent on SNS or local factors
Why do these arteries have the most elastin?
-Pressure is highest close to the heart that’s why we need the most expansion ability
Why do these arteries have the thickest tunica media?
-Heading towards our organs and to our muscles during vasoconstrict or vasodiliate
Capillaries
- most capillaries are continous capillaries - most simple squamous epithelium and basement membrane like connective tissue surroung it
- all connected with tight junctions that prevent fluid from moving into the cell
- See intracellular clefts that are spaced out to allow nutrients to move through
- 8-10 microns in diameters
Why are capillaries only 1 cell thick
-help with diffusion and easily move to the other side to get to tissues aids with movement of molecules in/out to the capillaries
Pericyte surround the capillaries and help form new capillaries
Capillary Beds
Precapillary sphincters line the thoroughfare channel
-Sphincters (drawstring bags) - like anal sphincters, muscles that seal off capillaries in the body. when we are cold and want to conserve body heat, what we do is close the pre-capillary sphincters so blood moves right from the thoroughfare channel into to the venule and keeps the blood deeper within us. On a hot day and we want to dissapate heat then the precapillary sphincters will open up and help regulate heat outwards. important for thermoregulation
• Capillary bed density varies from tissue to tissue
cornea, lens, cartilage don’t have any capillaries at all bc they’re avacular. they’re getting nutrients from other fluids. Ligament
Special Capillaries: Fenestrated Capillaries
- Have pores that span the endothelium
- Found at areas with exceptionally high nutrient exchange, digestive system, kidneys,
- holes are relatively small and allow ions, molecules to move through but not whole cells
- Found in synovial fluid, choroid plexus in the brain
Special Capillaries: Sinusoid Capillaries
- wide, twisting capillaries
- especially leaky
- found in the liver and spleen bc those are sites where we’re able to filter out old red blood cells and make them for destruction and also where white blood cells able to move into the blood vessels after they mature
- Bc wide and twisty slows the blood flow as they move down
Where else might you find these?
- bone marrow, spongybone to move in large intercelluar capillaries
Blood-Brain Barrier
- Endothelial cells in capillaries of the brain are all connected with tight junctions
- Intercellular clefts are absent
- Astrocytes they dictate what moves into and out the neural tissue - glucose and other molecules can’t move through the blood brain barrier
- Tight junctions
Vascular Anastomoses
- Connection of neighboring arteries/arterioles within each other
- why would this be really important?
- areas can still receive blood flow even if there’s a blockage/clot.
- What areas of the body might be beneficial to have an anastomosis?
- organs, heart, brain,
Arteries vs Veins
- Returns blood back to the heart
- What do you notice as the main difference betwn the structure of arteries and veins based on the pictures below?
- Veins have valves
- tunica media in veins are smaller than arteries
- the lumine are bigger in veins than arteries
- arteries have thick tunica media and narrow lumine
- Narrow pipe, high pressure in arteries
Venous System Structure
- Venules = smallest veins
- Larger venules have 1-2 layers of smooth muscle cells
- Vein lumens are larger than arteries of a comparable size
- Tunica externa typically larger than tunica media
- Less elastin.. Why?
- pressure is low and by the time we get to the capillary and we so many capillaries and the flow of blood slows down no reason for expansion ability
- Veins have valves which assist with return of blood flow to the heart
Mechanisms of Venous Return
- The valves are made of tumina intima
- they are one way valves
- Can’t go backwards bc of the one way valves
- As our muscles are contracting are squeezing blood to the next valve
- we don’t want blood to be spagnant
- Skeletal muscle pump to help ppl return blood to the heart even though the blood’s not active
- If they become stagnat we can have major problems the fluid can build up and compress capillaries and prevent the movement of oxygen in tissues and those tissues can die
- Respiration helps so when we inhale and creating a negative pressure in our chest and helps suck blood to vanea cavae into the heart and when we breath out and make our chest cavity smaller that increases the pressure to force air out and force blood pass the next valve
- Most of our valves are only in the veins that are in the extremities. most of the veins that within our abdominal region or chest region don’t have valves
Varicose Veins
- Due to valve failure
- Veins swell and venous drainage slows
- Risk factors: femal, sex, gentics, obesity, pegnancy, prolonged standing
to treat to surgery or use a chemical compound that’s injected to the vein and closes the valve. the blood will find another pathway and make it back to the heart
