Chapter 18: Blood Vessels and Circulation Flashcards
What do arteries do?
Carry blood away from the heart
In what conditioons do arteries carry blood away?
Usually oxygenated blood and under pressure
What do veins do?
Carry blood back into the heart
Under what conditions do veins carry blood back into the heart?
Usually deoxygenated and more sluggish
What do capillaries do?
Connect smallest arteries to veins
Mineral and gas exchange takes place in the ________
Capillaries
What are the 3 layers of the walls of the arteries and veins?
- Tunica interna (intima)
- Tunica media
- Tunica externa (adventitia)
____ is the inner layer of the vessel wall, and continous with the endocardium of the heart
Tunica interna
What is the shape of the endothelium?
Simple squamous
What are some features of the tunica interna?
Selectively permeable barrier
Secretes chemicals that stimulate dilation and constriction
Produces cell-adhesion molecules for leukocytes for nearby inflammation
____ the middle layer that is usually the thickest, comprised of smooth muscle, collagen and some elastic
Tunica media
Why does the tunica media have smooth muscle?
For vasomotion (vasoconstriction and vasodilation of blood vessels)
What are 2 features of the tunica media?
Strengthens vessels, preventing blood pressure from rupturing them
Regulates diameter of blood vessel
____ is the outermost layer of the vessel wall, made of loose connective tissue
Tunica externa
What are the smaller vessels of tunica externa called?
vaso vasorum
What is something that makes veins and arteries different?
Arteries have a heightened musculature that allows them to retain their round shape even when empty
What is the largest group of arteries?
Conducting (elastic) arteries
What are some examples of conducting arteries?
Pulmonary, aorta and common carotid, subclavian
____ and ____ sandwhich the tunica media
Internal and external elastic laminas
Conducting arteries ____ during systole and ____ during diastole
Expand
recoil
What is it called when arteries stiffen with age?
Arteriosclerosis
What is the medium sized arteries called?
Distributing (muscular or medium) arteries
What are some examples of distributing arteries?
Femoral, splenic, brachial arteries, renal
What are the smallest group of arteries called?
Resistance (small) arteries
What is the smallest kind of resistance arteries?
Arterioles
____ are short vessls that link arteriols to capillaries
Metarterioles
____ is the major point of control to how much blood organ and tissue receives
Resistance arteries
What is an aneurysm?
A weak point in artery or heart wall
What happens in a dissecting aneurysm?
This is when blood accumulates between theb tunics or artery and seperates them, usually because of degeneration of the tunica media
What are the most common sites of an aneurysm?
Abdominal aorta, renal arteries and arterial circle at the base of the brain
What can a rupture from an aneurysm cause?
Hemorrrhage
What are the main causes of aneurysms?
Atherosclerosis and hypertension
________ are sensory structures in walls of major vessels that monitor blood pressure and chemistry.
Arterial sense organs
What is regulated by the transmission of information to brainstem?
Heart rate, blood vessel diameter and respiration
What do baroreceptors do?
Monitor blood pressure
What are the kinds of baroreceptors?
Aortic arch baroreceptors and cariotid sinuses
____can be found in the walls of the internal carotid artery
Carotid sinuses
What do chemoreceptors do?
Monitor blood chemistry
Carotid/aortic bodies are ________.
Chemoreceptors
What do the signals sent to the brain from the carotid/aortic bodies help with?
The stabilization of pH, O2 and CO2 levels
Where are capillaries usually scarce?
In tendons, ligaments, cartilage and epithelia
What are capillaries composed of?
Endothelium and basal lamina
What are the capillary types determined by?
The ease with which substances pass through their walls (permeability)
What are the 3 capillary types? m
Continous
Fenestrated
Sinusoid
What is the most common type of capillary?
Continous
What holds continous capillaries together?
Tight junctions with intercellular clefts
____ are cells that lie exterior to the endothelium and wrap around the capillary
Pericytes
____ capillaries are small membrane-lined holes in the endothelium
Fenestrated
Where are fenestrated capillaries needed?
In organs that require rapid absorption or filtration like kidneys or small intestines
What are the holes that endothelial cells are riddled with called?
Fenestrations that only allow the passage of small molecules
____ are irregular blood-filled spaces with large fenstrations, no basal lamina and endothelial cells that are sperated by wide gaps
Sinusoids
What do sinusiods allow to enter?
Proteins and blood cells
Where can sinusoids be found?
In the liver, bone marrow and spleen
Capillary beds have networks of ____ capillaries
10 -100
____ control which beds are well perfused (capillary flow)
Precapillary sphincters
What do single smooth muscle cells do?
Wrap around like a cuff around the opening to each capillary
When prcapillary sphincters are closed, ________. when they are open, ____________
Closed - Blood bypasses capillaries and goes through venules
Open - blood goes through
How much of a capilllary is open at a given time?
1/4
What are some differences between veins and arteries?
Veins have greater capacity for blood containment than arteries
Veins have lower blood pressure with little fluctuation
Veins collapse when empty and look almost flattened on histology slide
Where is most of the blood in the body?
In the veins
The blood flow in the veins is ____ rather than ______.
steady
pulsating
What venules are more porous than capillaries, only a tunica interna with a few supporting fibroblasts and no muscle?
Postcapillary venules
What venule receives blood from postcapillary venules, has tunica media, smooth muscle and tunica externa?
Muscular venules
What are the kinds of veins?
Medium and large veins
What does the skeletal muscle pump do?
Propels venous blood back into the heart
What causes varicose veins?
Failure of the venous valves
____ are varicose veins of the anal canal
Hemorrhoids
What are some examples of large veins?
venae cavae, pulmonary veins, internal jugular veins and renal veins
What is the most commmon circulatory route?
Heart to arteries to aeterioles to capillaries to venules to veins
In the ____, blood flows through 2 consecutive capillary networks before returning to the heart and can be found where?
portal system
kidneys
What does the portal system connect? (2)
The intestines to the liver and
the hypothalamus and anterior pituitary
____ is the convergence point between 2 vessels not mediated by capillaries
Anastomosis
What are the main kinds of anastomosis?
Ateriovenous (shunt)
venous
arterial
What happens in arteriovenous anastomosis?
Artery flows directly into vein, bypassing capillaries
What is the most common type of anastomosis, where one vein empties directly into another and is the reason vein blockage is less serious than arterial blockage?
Venous
____ anastomosis is where 2 arteries merge, providing alternative routes of blood supply to a tissue
Arterial
Where is arterial anastomosis common?
In coronary circulation and around joints
What is perfusion?
The flow rate of blood per given volume or mass of tissue in a given time (mL/min/g)
____ can occur with little or no change in total flow
Great variations in regional flow
Where is blood pressure measured?
At the brachial artery of the arm (point close to the hear) using a shygmomanometer
What is systolic pressure?
The blood pressure during ventricular systole (contraction)
What is diasstolic pressure?
BP during ventricular diastole (relaxation)
What is hypertension?
High blood pressure
What are the consequences of hypertension?
Can weaken arteries, can cause aneuryssms, and can promote atherosclerosis
What is hypotension?
Chronic low resting BP
____ causes hyptension
Blood loss, dehydration, anemia
What is arterioscelerosis?
Hardening of arteries
Arterioscelerosis is exacerbated by _______
Artherosclerosis
What is atherosclerosis?
Growth of lipid deposits on artery walls, may calcify and become complicated plaques
