Chapter 19 - Arteries Flashcards
Which direction do arteries carry blood?
Away from the heart, except in the pulmonary circuit
Which direction do veins carry blood?
Towards the heart
What is the main job of capillaries?
Take care of tissue needs, only vessels where gas exchange takes place
What are the 3 layers of arteries and veins?
Tunica Externa, Tunica Media, Tunica Intima
What is the Tunica Externa - Where found? What is it made up of? Purpose?
External layer of arteries/veins, made up of collagen fibers, anchors the vessel to surrounding structures
What is a lumen?
Cavity inside a blood vessel, hollow organ, or inside a tube
What is the Tunica Media - where found? what is it made up of? Purpose?
middle layer, made up of smooth muscle + elastin, regulates blood circulation
What is the tunica intima - where found? what is it made up of? purpose?
Innermost layer, contains the endothelium, allows blood to move smoothly
What is an endothelium?
Inner lining of all blood vessels made up of simple squamous cells
What is the subendothelial layer?
Found in vessels greater than 1mm in diameter, exterior to the endothelium
What are the 3 types of arteries?
Elastic, muscular, arterioles
What is another name for an elastic artery?
conducting arteries
Describe the structure of an elastic artery
Very thick walls, contain elastin in all 3 tunics
Where are elastin arteries found?
aorta and major branches
What is the role of an elastic artery?
Act as pressure reservoir to expand and recoil with blood ejection
What is another name for muscular arteries?
distributing arteries
Where are muscular arteries located?
distal to the elastic arteries
What is the role of a muscular artery?
Delivery system to body organs, very important in vasoconstriction
Describe the structure of a muscular artery
Very thick tunica media and thick layer of smooth muscle
How do muscular arteries control blood flow?
vasoconstriction
What are arterioles?
smallest arteries, last branches before capillary beds
What is the role of arterioles?
Control flow to capillary beds through vasodilation and vasoconstriction
What are capillaries?
smallest of all blood vessels
What is the structure of a capillary and why?
Very thin tunica intima, only one cell thick to allow increased permeabillity
Capillaries are found in all tissues except…
Cartilage, epithelia, cornea, lens of eye
What is the function of capillaries?
Exchange of gases, nutrients, wastes and hormones
3 Structural Types of Capillaries
Continuous, Fenestrated, Sinusoidal
Where are continuous capillaries abundant?
Skin, muscles, and brain
What type of junction is found between the cells of endothelium in continuous capillaries?
tight junctions
What is the most common type of capillary?
continuous
What is the function of continuous capillaries?
Some passage of fluids and only small solutes, no passage of cells or massive movement of fluids
Rank capillaries in order of least permeable to most
continuous, fenestrated, sinusoidal
What is a fenestrated capillary?
Capillary with pores called fenestrations
What is the function of a fenestrated capillary?
Absorption or filtrate formation
Where are fenestrated capillaries found?
Small intestines, endocrine glands, kidneys
Describe the structure of sinusoidal capillaries?
Fewer tight junctions, larger intercellular clefts, large lumens, usually have fenestrations
Where are sinusoidal capillaries found?
Liver, bone marrow, spleen
What is the function of a sinusoidal capillary?
Allow large molecules and blood cells to exit or enter the lumen
What is a capillary bed?
Interwoven network of capillaries
What are two types of vessels found in capillary beds?
Metarteriole and true capillaries
What is a metarteriole?
Gatekeeper/bypass, controls access of blood to the true capillaries
What is another name for a metarteriole?
Vascular Shunt
What is the venous system?
Leads blood from capillaries to the heart
How does the blood pressure in the venous system compare to the artery system?
Blood pressure is lower
What are the two types of vessels found in the venous system?
Venules, Veins
How are venules formed?
Formed when capillary beds unite
What is anastomosis?
Uniting of capillary beds
Describe the structure of a venule?
Very porous, allows fluids and blood cells to exit vessels and move into tissues
What is a post capillary venule?
Smallest venule, only have endothelium and a few pericytes
What do larger venules have?
one or two layers of smooth muscle cells
How are veins formed?
Formed when venules converge
What are veins also known as?
Capacitance vessels/blood reservoirs
Describe the structure of a vein
thin tunica media, thick tunica externa
Special features of veins
large lumens, valves to prevent backflow of blood
What generates blood flow in systemic blood pressure?
Pumping action of the heart
In systemic blood pressure, what causes the pressure in blood vessels?
Pressure results when flow is opposed by resistance/friction
In systemic blood pressure, where is pressure the highest?
Aorta
In Systemic blood pressure, where is pressure the lowest?
Declines throughout the pathway, lowest at vena cavae
What are the 3 components of arterial blood pressure?
Systolic pressure, diastolic pressure, pulse pressure
What is systolic pressure?
Pressure exerted during ventricular construction (systole)
What is diastolic pressure?
Lowest level of arterial pressure (diastole)
What is pulse pressure?
Difference between systolic and diastolic pressure (SP-DP)
What is a mean arterial pressure (MAP) and what is the formula to calculate?
Pressure that propels the blood into the tissues. MAP=diastolic + 1/3 pulse pressure
What is the formula for pulse pressure?
systolic - diastolic (top # - bottom #)
What happens to pulse pressure and MAP as the distance from the heart increases?
They decrease
What is the capillary blood pressure range?
15 to 35 mmHG
What type of pressure is desired in a capillary? Why?
Low pressure, high blood pressure ruptures thin capillary walls, increases permeability
How does venous blood pressure change during the cardiac cycle?
Changes very little, roughly 15 mmHG pressure gradient
What is a pressure gradient?
force that pushes liquid through the vessel
What factors aid venous return to the heart?
Respiratory pump, muscular pump, venous vascoconstriction (under sympathetic nervous system control)
What are the 3 main factors that influence blood pressure?
Cardiac output, peripheral resistance, blood volume
What are the 2 neural controls for blood pressure?
Baroreceptors, chemoreceptors
What are baroreceptors?
Pressure sensors
What are chemoreceptors?
Detect changes in carbon dioxide levels or pH changes
What hormonal controls cause vasoconstriction?
Norepinephrine/epinephrine, angiotensin II, Antidiuretic hormone
What hormonal controls cause vasodilation?
Atrial natiuretic peptide
What is tissue perfusion?
amount of blood that is available to tissues
What 5 Things is Tissue Perfusion Necessary for?
O2 and nutrient delivery, waste removal, gas exchange, absorption of nutrients, urine formation
What is autoregulation?
LOCAL regulation of blood flow, adjustment based on immediate needs; organ level
2 types of autoregulation
Metabolic, Myogenic
What is the metabolic control of blood flow?
chemical control, occurs when there is a lot of cellular metabolism, creating large amount of waste and tissue perfusion is increased to enhance removal and ensure delivery of more nutrients
In metabolic control of blood flow, how is increased tissue perfusion accomplished?
Vasodilation of arterioles and relaxation of precapillary sphincters
In metabolic control of blood flow, what do vascular endothelial cells release?
Nitric Oxide, which is the major factor that causes vasodilation
The opposite of vasoconstriction is caused by…
Low oxygen, decrease in available nutrients
What is myogenic control?
control by physical means
In Myogenic Control, what does smooth muscle enable
Keeps tissue perfusion constant even through systemic pressure changes
In myogenic control, what causes passive stretch? What does it cause?
Due to increased intravascular pressure, causes increased tone and vasoconstriction
In myogenic control, what does reduced stretch promote?
Promotes vasodilation and increase of blood flow
How does capillary exchange of respiratory gases and nutrients?
Diffusion
What is diffusion
Movement of substances from an area of high concentration to an area of low concentration
What substances are moved by diffusion?
O2, nutrients, Co2, metabolic waste
How do lipid soluble molecules diffuse?
Directly through the endothelial membranes
How do water soluble solutes pass?
Through clefts and fenestrations
How are larger molecules like proteins moved?
Actively transported in pinocytotic vesicles or caveole
Name a Vein Disorder and it’s cause
Varicose Veins, due to leaky valves, usually occur in lower limbs, but also in anal veins
What are 3 Blood Pressure Disorders
Hypotension, Hypertension, Circulatory Shock
What is hypotension? What is often associated with?
low blood pressure, systolic bp less than 100 mmHG, often associated with longer life and lack of cardiovascular illness
What is hypertension?
High blood pressure, sustained arterial pressure of 140/90 or higher; often in obese people
What are transient causes of hypertension?
Fever, physical exertion, emotional upset
What are 3 types of circulatory shocks?
Hypovolemic, vascular, cardiogenic
What is hypovolemic shock? What can cause it?
Inadequate blood volume caused by a hemorrhage, severe vomiting/diarrhea or extensive burns
What is vascular shock? What are 2 causes?
Normal blood volume, but poor circulation due to extreme vasodilation; caused by anaphylaxis or septicemia
What is cardiogenic shock? What causes it?
Pump failure, heart is too inefficient to maintain circulation; caused by myocardial infraction
