Blood Vessel Flashcards
Blood Vessel layers
Tunica Interna: innermost layer
Tunica Media: Middle layer, smooth muscle and elastic fibers
Tunica Externa: outtermost layer
Blood Vessel vs. Artery
Artery has large tunica media, smooth muscle,
Artery has more elastic layers
Veins tend to have a larger lumen and main structural feature is the valve, prevents backward flow of blood
Cappilaries
One cell thick, endothelium
Surrounded by basement membrane.
Tight and continuous or have holes in them, all depends on where they’re on the body
Arteries
Carry blood away from the heart to the tissues
walls are elastic, allowing them to absorb pressure
Because of smooth muscle, they can regulate in diameter( vasoconstriction)
Types of ateries
Elastic Arteries
Muscular arteries
Anastomoses
Where branches of arteries fuse and move out in different directions
supply the same body region
Capillaries
Smallest blood vessels connect arterial outflow and venous return
One cell thick & composed of basement membrane
permit the exchange of nutrients
Found everywhere
Microscopic vessels that connect arterioles and venues
Tunica media and tunica externa
Types of capillaries
Three types
Continuous: tight junctions but you can move fluids in between cells, endothelial cells
Fenestrated: Found in kidney and parts of DT, allows some proteins and larger molecules to move out of the blood vessels. have fenestrations or pores
Sinusoid:Wider and more winding, Allow for large plasma proteins to move in and out and some cells too, found in liver and spleen primarily
Veins
Veins have little smooth muscle, very thin walls
Have valves
same 3 layers: but
Tunica internal thinner than arteries and with little smooth muscle
and the tunica externa is the thickest layer
Valves fold on tunica international forming cusps
Blood distribution
Largest portion of the blood is in the veins and venues,aka blood resiviors. 64%
Heart 7%
Pulmonary 9%
Capillaries 7%
arteries and arterioles 13%
Venoconstruction reduces volume of blood in reservoirs and allows greater blood volume to flow where needed
Capillary exchange
The movement of substances between blood and interstitial fluid
Substances cross capillary walls by :
Diffusion
Transcytosis
Bulk flow: movement of fluid under pressure
Bulk flow
Passive process in which large number of ions molecules or particles in a fluid move together in the same direction
Based on pressure gradient
More important for regulation of relative volumes of blood and interstitial fluid
Filtration
Pressure driven movement of fluid and solutes from blood capillaries into interstitial fluid
Reabsorbtion
Pressure driven movement of fluid and solutes from interstitial fluid into capillaries
blood flow
Volume of blood flowing through any tissue at a given time
What are the five main types of blood vessels
Arteries arterioles capillaries venules veins
Tunica interna
Inner lining in direct contact of blood
Active role in vessel related activities
Tunica media
Muscular and connective tissue layer
Smooth muscle regulates diameter of lumen
Tunica externa
Elastic and collagen fibers
Helps anchor vessel to surrounding tissue
Elastic arteries
Largest artery’s
largest diameter but walls relatively thin
function as pressure reservoir
help propel blood forward while ventricles relaxing
also known as conducting arteries a.k.a. conduct blood to medium size arteries
Muscular arteries
Tunica media contains more smooth muscle and fewer elastic fibers than elastic arteries
walls relatively thick
Capable of great vasoconstriction to adjust rate of blood flow
Also called disturbing arteries
Portal vein
Blood passes through second capillary bed
Hepatic or hypophyseal
Venules
Thinner walls then arterial counterparts
post capillary venue- smallest manual
Muscular venules have thicker walls with one or more layers of smooth muscle
Diffusion
Most important method Substances move down their concentration gradient Substances can cross capillary wall through intracellular clefts fenestrations or through endothelial cells
Post plasma proteins cannot cross except sinusoids, because of blood brain barrier which limits diffusion
Transcytosis
Small quantity of material Substances in blood plasma become enclosed
Important mainly for large lipid insoluble molecules that cannot cross capillary walls any other way
Net filtration pressure
The balance of two pressures
Blood hydrostatic pressure and interstitial fluid osmotic pressure
Subtracted by
Blood call Lloyd osmotic pressure and interstitial fluid hydrostatic pressure
Starlings law
Nearly as much reabsorbed as filtered
What are the factors that affect blood flow
A flow is the volume of blood that flows through any tissue in a given period of time
Total blood flow is cardiac output
Cardiac output depends on pressure differences and resistance to blood flow in specific blood vessels
What is blood pressure
Contraction of ventricles generates blood pressure
Systolic BP is the highest pressure attained in arteries during systole
Diastolic BP is the lowest arterial pressure during distole
Pressure falls progressively with distance from left ventricle also depends on total volume of blood
Vascular resistance
Opposition to blood flow due to friction between blood and walls of blood vessels
Depends on: size of lumen blood viscosity and total blood vessel length
Venous return
Volume of blood flowing back to the heart through systemic veins
occurs due to pressure generated by construction of left ventricle
small pressure difference from venue to right ventricle
Skeletal muscle pump
Milks blood in One Direction due to valves
Respiratory pump
Occurs due to pressure changes in thoracic and abdominal cavities
Velocity of blood flow
Is the speed in cm/sec in inversely related to cross-sectional area
it’s at its lowest when total cross sectional area is greatest
But the flow become slower for their from the heart it’s the slowest in the capillaries
Aids in exchange
Circulation time
The time required for a drop of blood to pass from right atrium through pulmonary and systemic circulation and back to right atrium
Control of blood pressure and blood flow
Interconnected negative feedback systems control blood pressure by adjusting heart rate stroke volume systemic vascular resistance and blood volume
Some act faster than others
Some shorter or longer term
The role of cardiovascular center
Occurs in the medulla oblongata
Helps regulate heart rate and stroke volume also controls neural. hormona,l and local negative feedback systems that regulate blood pressure and blood flow to specific tissues
Happens when groups of neurons regulate heart rate contraction of ventricles and blood vessel diameter
Receives input from both higher brain regions and sensory receptors
The three main types of sensory receptors
Proprioceptors: another movement of joints and muscles to provide input during physical activity
Baroreceptors: that are pressure changes and stretch in blood vessel walls
Chemoreceptors: Monitor concentration of various chemicals in the blood
Neural regulation of blood pressure
Negative feedback loops from two types of reflexes
Baroreceptor reflexes and
Chemoreceptor reflexes
Baroreceptor reflexes in neural regulation
Pressure sensitive receptors in internal carotid arteries and other large arteries in neck and chest
Occurs when blood pressure falls and baroreceptors are stretched less slower rate of impulses to CV
CV decreases parasympathetic stimulation and increases sympathetic stimulation
Chemo receptor reflexes in neural regulation
Receptors located close to baroreceptors of carotid sinus and aortic arch
They detect hypoxia, hyper Capnia, acidosis and send signals to CV
CV then increases sympathetic stimulation to arteries and veins producing vasoconstriction and an increase in blood pressure Receptors also provide input to respiratory center to adjust breathing rate
The hormonal regulation of blood pressure: Renin angiotensin aldosterone system
In an in angiotensin converting enzyme acts on substrates to produce active hormone angiotensin two
This raises BP by vasoconstriction and secretion of aldosterone
The hormonal regulation of blood pressure: epinephrine and norepinephrine
Renal medulla releases in response to sympathetic stimulation increase cardiac output by increasing rate in force of heart contractions
The hormonal regulation of blood pressure: antidiuretic hormone or vasopressin
Produced by hypothalamus released by posterior pituitary response to dehydration or increased blood volume causes vasoconstriction which releases blood pressure
Atrial natriuretic peptide
Released by the cells of atria Lowers blood pressure by causing vasodilation and promoting loss of salt and water in urine
reduces blood volume
Auto regulation of blood pressure
Ability of tissue to automatically adjust its blood flow to match metabolic demand
Also controls regional blood flow in the brain during different mental and physical activities
two types of stimuli: physical a.k.a. temperature changes, myogenic responds
and
vasodilating/vasoconstricting chemicals alter blood vessel diameter
Circulation
Important difference between pulmonary and systemic circulation in autoregulatory response
- systemic blood vessel walls dilate in response to low O2 to increase O2 delivery
- walls of pulmonary blood vessels constrict under low O2 to ensure most blood flows to better ventilated areas of the lungs
