3 (19) The Cardiovascular System: Blood Vessels Flashcards
What is an artery?
carries blood away from the heart
What is the lumen?
the hole in the middle of the artery
What are the three layers or tunics of an artery?
tunica interna, tunica media, tunica externa
Which tunic is the thickest?
tunica media
What makes up each layer of an artery?
TUNICA INTERNA - simple squamous epithelium called “endothelium”
TUNICA MEDIA - smooth muscle fibers
TUNICA EXTERNA - thin connective tissue
What are the vasa vasorum?
tiny vessels in the tunica externa that form capillaries and provide blood to external cells of the vessel
How do the elastic arteries act as a pressure reservoir?
redistributing the pulsatile input over time by expansion and recoil
How do arterioles differ in structure from arteries?
they have all three layers, but thin as they divide
What are arteriovenous shunts?
abnormal connections between coronary arteries and a compartment of the venous side of the heart
What is the structure of a capillary wall?
only a single layer of endothelium and a basement membrane
What structure is always found at the start of a true capillary?
pre-capillary sphincter
What do capillaries do for the cardiovascular system?
functional part of system for exchange of gases, wastes, and nutrient
What makes up a capillary?
single layer of endothelium and basement membrane
What is the difference in structure between continuous capillaries, fenestrated capillaries, sinusoids, and the capillaries found in the brain?
CONTINUOUS - intercellular clefts, but otherwise uninterrupted; “garden variety” common capillaries
FENESTRATED - have “windows” or pores (act in filtration) (window in French = fenetre)
SINUSOIDS - (discontinuous capillaries) have spaces b/w cells; basement membrane is incomplete or absent
BRAIN - form a barrier (blood-brain barrier)
What are venules?
a small blood vessel in the microcirculation that allows deoxygenated blood to return from capillary beds to larger blood vessels called veins
What is the structure of a vein, and how does it differ from an artery?
OUTER - connective tissue, “tunica adventitia” / “tunica externa”
MIDDLE - smooth muscle, “tunica media” (thinner than artery)
INNER - lined with endothelial cells, “tunica intima”
What internal structures do veins contain that arteries do not?
VALVES that ensure blood flows in only one direction
Why are systemic veins called blood reservoirs? What can happen if you lock your knees, as when standing at attention?
- because it can be mobilized to boost cardiac output and in turn systemic arterial pressure when physiological demands require so (nearly 60% of the total volume of blood in the human body is present within the veins)
- squeezes your veins shut in your legs, that leads to you losing blood supply to the rest of your body causing you to faint
What is blood pressure?
pressure on the walls of a vessel
What is meant by systolic blood pressure and what would you expect the values for this to be?
the amount of pressure in your arteries during the contraction of ventricle (~120 mm Hg)
What is meant by diastolic blood pressure, and what would you expect the values for this to be?
blood pressure generated by ventricular relaxation (~80 mm Hg)
What is the mean arterial pressure?
93 mm Hg
In what vessels does blood travel the fastest?
arteries
In what vessels does blood travel the slowest?
capillaries
What is a normal systolic blood pressure? Diastolic blood pressure?
120
80
What factors influence arterial blood pressure?
cardiac output blood volume peripheral resistance (BP = CO * PR) viscosity blood vessel diameter
What is a pulse, and how can it be used to determine the health of an individual?
PULSE: pressure wave generated by the alternating expansion and recoil of arteries during each cardiac cycle
- can be used to determine extent of injury, effects of activity, postural changes, emotions on heart rate, arrhythmias
What is the normal central venous pressure and where is it measured?
2-6 mm Hg
measured in thoracic vena cava
What part of the nervous system controls blood vessel diameter, and why is this unusual?
sympathetic nervous system
Look over fetal circulation again.
- obtains oxygen/nutrients from maternal circulation
- ductus
What is the hepatic portal system? Why is it important?
- drains spleen, stomach, pancreas, gallbladder, and small/large intestines
- 2nd capillary bed in liver
- glucose is removed and stored as glycogen
- blood is detoxified
- leaves through hepatic vein and goes to inferior vena cava
What is the Circle of Willis or cerebrovascular circle? What does it do for the brain?
- the joining area of several arteries at the bottom (inferior) side of the brain
- the internal carotid arteries branch into smaller arteries that supply oxygenated blood to over 80% of the cerebrum
