Blood vessels Flashcards
What are the different types of blood vessels?
Arteries
Veins
Capillaries
Where do arteries carry blood?
What do they branch into?
Carry blood away from the heart
Branch to form arterioles
Where to veins carry blood?
What are the smallest veins called?
Carry blood towards the heart.
Smallest veins are called venules.
What are capillaries?
Smallest blood vessels.
Site of exchange between blood and tissue fluid
Provide a schematic of blood flow.
SVC/IVC/CS –> RA –> T –> RV – PSLV –> PT –> LPA, RPA –> Lungs –> 4 PV –> LA –> BV/MV –> RV –> ASLV –> Aorta, CA –> Body
What are the three layers of blood vessels>
Tunica intima/interna
Tunica media
Tunica externa
What is the tunica intima?
Simple squamous epithelium
Intimate contact with blood
What is the tunica media?
Sheets of smooth muscle, elastic CT, collagen
What layer allows for vasoconstriction/dilation? How?
Tunica media
Contract - constrict
Relax - dilate
What is the tunica externa composed of?
CT
What is the lumen of the blood vessels?
Central, blood-filled space of a vessel
What are the differences between the arteries and veins?
Arteries are more elastic - external elastic membrane
- arteries have a larger smooth muscle layer
- lumen of artery is circular (Even without blood)
Veins have valves
- veins have a thinner tunica media (less smooth muscle)
- lumen of vein is more floppy (especially without blood)
What are the different types of arteries?
Elastic
Muscular
(Arterioles)
What are elastic arteries?
Conducting arteries
The largest arteries - aorta and its major branches
high elastic content (dampens surge of blood pressure)
Thick tunica media, lots of elastic fibres
What are muscular arteries?
Distributing Lie distal to elastic arteries Thick tunica media Unique structures: - internal and external elastic laminae Can contract or relax to change the amount of blood going to certain organs
Describe arterioles.
Smallest arteries
Larger arterioles have all three tunics
Close to capillary beds
Describe the control of arteriole diameter.
Due to local factors in the tissues and the sympathetic nervous system
What are capillaries?
Smallest blood vessels
Renew and refresh surrounding tissue fluid
RBCs pass in a single file
What are the site-specific functions of capillaries at the: lungs SI endocrine glands kidneys
Lungs - oxygen enters blood, carbon dioxide leaves
SI - receives digestive nutrients
Endocrine glands - picks up hormones
Kidneys - removal of nitrogenous wastes
What are capillary beds?
Network of capillaries running through tissues.
What are metarterioles?
Intermediate between capillary and an arteriole
What is a thoroughfare channel?
Intermediate between capillary and venule
What are precapillary sphincters?
Regulate blood flow through capillaries.
What tissues do not have a rich capillary supply?
Tendons and ligaments - poorly vascularized
Epithelia and cartilage - avascular
Fast-Oxidative fibres
Describe the action of precapillary sphincters when running.
Precapillary sphincter to skeletal muscle opens to increase blood supply.
Closes to digestive organs.
In capillaries, what are endothelial cells held together by?
Tight junctions and desmosomes.
What are intercellular clefts?
What do they allow through?
Gaps of un-joined membrane
Allow small molecules to enter and exit the capillaries
What are the four routes into and out of the capillaries?
What does each allow through?
1 - Direct diffusion - respiratory gases
2 - Through intercellular clefts - small molecules
3 - Through cytoplasmic/pinocytic vesicles - gases, nutrients, wastes
4 - Through fenestrations - water molecules
What are the three kinds of capillaries?
Continuous
Fenestrated
Sinusoid
What are continuous capillaries?
Where are they found?
Most common - lack pores
Brain, skeletal muscle, smooth muscle, lungs
What are fenestrated capillaries?
Where are they found?
Porous
Found in sites with high rate of exchange of small molecules between blood and tissue fluid.
ex: kidneys, SI, synovial membrane
What are sinusoid capillaries?
Where are they found?
Wide, leaky capillaries
Fenestrated with wide open intercellular clefts.
Large diameter and twisted course.
Slow blood flow allowing exchange of large molecules.
Incomplete basement membrane.
Pericytes to control the diameter and provide structural support
Bone marrow and spleen
What are pericytes?
Found in sinusoid capillaries, provide support and control the diameter.
What is a low permeability capillary in the body?
Why is it so?
Blood brain barrier
Capillaries have complete tight junctions, no intercellular clefts
Only allows vital molecules through: such as oxygen, carbon dioxide, some anesthetics.
Want to be as selective as possible to prevent toxins, bacteria and such from entering the brain from the blood.
What can pass through the BBB?
oxygen, carbon dioxide, anesthetics that are fat soluble
nicotine and alcohol.
How can the BBB be opened?
During times of prolonged stress and/or extreme emotional stress, the cells of the BBB open up.
Why would we want to be able to open the BBB?
Analgesic effects
Chemo to enter
More localized treatment
What are the smallest veins called?
Is the blood pressure in veins higher or lower than that of the arteries?
______ join to form veins.
What is the thickest tunic in veins?
The lumen of veins is _____ than that of arteries.
Venules Lower Venules Tunica externa Smaller
Why is the lumen bigger in veins?
Thin tunica media
What are the mechanisms to counteract low venous pressure?
Valves in some veins
skeletal muscle pump
breathing
Where are valves found in veins? (or where would veins with valves be located?)
in the limbs
The cusps of vein valves are made up of which layer?
Tunica intima
How does skeletal muscle pump the blood of the veins?
Muscles press against the thin-walled veins.
Veins are superficial and muscles contracting against them will push blood upwards
How does breathing counteract low venous blood pressure?
Active breathing allows more blood to get up to the heart.
Describe varicose veins.
Which veins/areas are more susceptible.
Who would be more susceptible?
Why does it occur?
Twisted, dilated superficial veins.
Valves in veins weaken and fail
Veins swell with pooled blood and drainage slows.
Left lower limb more susceptible.
Women more susceptible than men.
Occurs in individuals who are pregnant or stand for a prolonged period.
Non-moving legs causes the veins to drain slowly and blood to accumulate, stretching the veins and valves.
Vascular anastomoses:
Vessels interconnect to form vascular _________.
Organs receive blood from more than one ______ source.
Neighbouring ______ form _______ anastomoses.
______ anostomose more frequently than _______
Most commonly found:
- Around _____
- In the ______
- Around the ______
anastomoses arterial arteries arterial veins arteries joints brain heart
What is an anastomoses?
Coming together of blood vessels.
Should one get blocked, there are other routes to use.
What is the vasa vasorum?
The tunica externa of large blood vessels will have tiny arteries, capillaries and veins.
These are vessels of large vessels with nourish it.
Blood distribution:
60-65% of the blood volume at rest is in the _______ ______ and _______.
These function as _____ ________.
These include the veins of the _____ and _______ organs.
Blood is diverted from this storage in times of ______.
_________ causes vasoconstriction to help maintain blood pressure.
systemic veins venules blood reservoirs skin adbominal need hemorrhage
All systemic arteries branch from the _____.
All systemic veins drain into the ____, ____ or ______ ______.
aorta
SVC, IVC, CS
Why can owls turn their heads so much?
Double the cervical vertebrae
larger transverse foramen so don’t impinge carotid arteries
Describe a brain freeze.
Rapid change in temperature at the back of the throat causes constriction of arteries.
Pain receptors surrounding the vessels trigger nerves carrying info from face to brain
Nerves normally sense facial pain, signals brain to interpret swelling coming from forehead
Brain cannot feel pain
Get anastomoses in the circle of willis to constrict
What does the superior mesenteric artery supply?
Pancreas, SI, ascending and part of transverse colon.
What does the inferior mesenteric artery supply?
Second half of transverse and descending and sigmoid colons, and rectum
What are pulse points?
Veins are generally more superficial than arteries but, in certain areas, have superficial arteries where the pulse can be determined.
ex: side of neck - left and right common carotid arteries
What is a portal vein?
A vein that carries blood from one capillary network to another.
(Artery - capillary - portal vein - capillary - vein)
Describe hepatic portal veins.
Receives blood and digested nutrients from capillaries of digestive organs and the spleen, and delivers them to the sinusoids of the liver for processing and storage.
What are the veins of the hepatic portal system?
Superior mesenteric vein
Splenic vein
Inferior mesenteric vein
Hepatic portal vein
Draw the hepatic portal circuit.
Refer to notes.
