Ch. 18 Blood vessels Flashcards
What are the 3 main type of blood vessels?
Arteries - blood away from heart - oxygenated
Capillaries - direct contact with tissue cells
Veins - Carry blood to heart - deoxygenated
What makes up a capillary wall?
Endothelium with sparse basal lamina
What is the tunica intima made of?
Endothelium- simple squamous, continuous with endothelium
What are the characteristics of tunica intima?
- Can secrete chemicals that can dilate or constrict
- Repels blood
- leukocytes can adhere if inflamed
What is the tunica media made of?
Smooth muscle, collagen and sheets of elastin
What are the characteristics of the tunica media?
Responsible for maintaining BP and BF by dilation or constriction
What nerve innervates the tunica media?
Sympathetic vasomotor nerve
What is tunica adventitia made of?
Loose connective tissue
What are the functions of the tunica adventitia?
Anchors blood vessel and provides passage for small nerves and lymphatic vessels
Arteries are divided into 3 groups based on what?
What are 3 groups?
Size and function
Elastic, Muscular, Arterioles
Elastic arteries are also called
Conducting arteries because they conduct blood from heart to medium sized vessels
What are the characteristics of elastic arteries?
- Thick-walled with large, low resistance lumin
- Contain substantial smooth muscle but don’t vasoconstrict
- Act as pressure reservoirs that expand and recoil as blood is ejected - allows for continuous flow & lessens fluctuations in blood flow
What are some common elastic arteries?
Aorta, common carotid, subclavian, pulmonary trunk
What are muscular arteries also called?
Distributing arteries - deliver blood to body organs
What are the characteristics of muscular arteries?
- account for most of the names arteries
- Thickest tunica media - more smooth muscle, less elastic
- Acitve in vasoconstriction
What are some common muscular arteries?
Brachial, femoral, renal, splenic arteries
Arterioles are also called
Resistance arteries bc of changing diameters
What are the characteristics of arterioles?
- Larger contain 3 tunics, smaller have smooth muscle and endothelial cells
- Lead to capillary beds
- Control amount of blood into capillary beds by vasodilation or constriction
Capillaries are made of
endothelium - just a thin tunica intima
What are the functions of capillaries
exchange of gases, nutrients, waste, hormones etc between blood and interstitial fluid
Capillaries supply almost every cell except
cartilage, epithelia, cornea, and lens of the eye
Pericytes
Spider shaped stem cells which help stabilize capillary walls, control permeability and play a role in vessel repair
Capillary endothelial cells are joined by
tight junctions with gaps called intercellular clefts
Intercellular clefts allow for
passage of fluids and small solutes
What are the 3 types of capillaries?
Continous, fenestrated, sinusoidal
Continuous capillaries are found
in skin, muscles, lungs, and CNS
BBB in brain
Fenestrated capillaries are found in areas where
active filtration (kidneys) or filtration (intestines) or endocrine hormone secretion
Fenestrated capillaries look like —– which allows for—-
swiss cheese & increases permeability
Sinusoidal capillaries are found in and contain?
Macrophages - found in liver, bone marrow, spleen and adrenal medulla
What is a capillary bed?
interwoven network of capillaries between arterioles and venules
What is microcirculaton?
Flow of blood through capillary bed
What 2 types of vessels make up the capillary bed?
Vascular shunt - connects arteriole directly with venule
True capillaries - vessels involved with exchange
What are precapillary sphincters?
Regulate flow of blood into capillaries
10-100 exchanged vessels per bed
Regulated by local chemical conditions and vasomotor nerves
What 2 parts make up a vascular shunt?
Metarteriole and thoroughfare channel
Capillaries unite to form
postcapillary venules
Venules consist of
endothelium and a few pericytes; very porous - allow fluid and WBC into tissues
Veins are also called
capacitance vessels (blood reservoirs) bc they contain up to 65% of blood supply
What are the characteristics of veins?
all 3 tunics, but thinner walls with larger lumens
Tunica media is thin, tunica external is thick
contain collagen fibers & elastic
low pressure
have valves
What are the 3 types of veins?
Large - larger than 10mm
medium - up to 10mm
Postcapillary venules - smallest
What are some common large veins?
Venae cavae, pulmonary veins, jugular veins
venous valves prevent
backflow of blood, most abundant in lower limbs
Venous sinuses are
flattened veins with thin walls, composed of only endothelium. Ex. coronary sinus
Varicose veins are caused by
incompetent (leaky) valves
Heredity and external conditions, standing, obesity, pregnancy, elevated pressure (delivering baby)
What are 4 types of anastomoses?
Vascular - interconnections of blood vessels
Arterial - alt. pathways to ensure continuous flow in arteries
Ateriovenous - shunts, ex. metarteriole-thoroughfare
Venous - veins
How is blood flow (F) defined?
Volume of blood flowing through vessel, organ or entire circulation in any given period
measured in ml/min
How is blood pressure (^P) defined?
force per unit area exerted on wall of blood vessel by blood
expressed in mm Hg
Pressure gradient keeps blood moving to areas of lower pressure
How is resistance (R) defined?
Opposition to flow
What are 3 sources of resistance to blood flow?
- Blood viscosity
- Total blood vessel length
- Blood vessel diameter
*if radius increases resistance decreases (if radius is doubled, resistence drops 1/16)
Blood flow is directly porportional to …
Blood pressure
If pressure increases blood flow speeds up
Blood flow is inversely proportional to…
resistance
if resistance increases blood flow decreases
Steepest drop in pressure occurs in
arterioles
Arterial blood pressure is determined by what 2 factors?
Elasticity of arteries close to heart
Volume of blood forced at any time
What does pulsatile mean?
Rises and falls with every heart beat
What is systolic pressure?
Pressure exerted in aorta during ventricular contraction
avg 120 mmHg
What is diastolic pressure?
Lowest level of aortic pressure when heart is at rest
What is pulse pressure?
Difference between systolic and diastolic pressure (SP-DP)
What is MAP?
The pressure that propels blood into tissues
evens out by end of arteriole / pulse and MAP both decline with increasing distance from heart
How do we calculate MAP?
What are vital signs?
Pulse and BP
respiratory rate and temp
Capillary bp ranges from
35 mm Hg at beginning of bed to 17 mm Hg at end
Why is lower capillary pressure more desirable?
Could rupture capillaries if too high
Most capillaries are very permeable so low-pressure forces filtrate into interstitial spaces
Venous blood pressure is about what mm Hg?
15 mm Hg
Energy of BP is lost as —– during each circuit
heat
What are 3 factors that aid in venous return?
- Muscular pump - skeletal muscles; valves prevent backflow
- Respiratory pump - pressure changes during breathing move blood back to the heart
- Sympathetic venoconstriction - smooth muscles constrict, pushing blood back to heart
What 3 main factors regulate blood pressure?
- Cardiac output
- Peripheral resistance
- Blood volume
^P = CO X R
Maintaining blood pressure requires the cooperation of..
heart, blood vessels and kidneys
Anything that increases SV, HR or R will also increase…
MAP
SV can be affected by
HR is maintained by
R is affected mostly by
SV - venous return
HR - medulla oblongata
R - vessel diameter
What are the short term regulation of blood pressure: neural controls?
Vasomotion via:
Baroreceptor reflex- stretch detector
Chemoreceptor - chemical detector
CNS - Medulla oblongata - cardioinhibitory or cardioacceleratory
Where are the baroreceptors located
Walls of large arteries, carotid sinuses, aortic arch
Sends to the brain via the glossopharyngeal nerve
** ineffective if altered BP is maintained. They adapt
Where are the chemoreceptors located?
what is chemoreceptors primary role?
Aortic bodies, arch and large arteries of neck
detect increase in Co2, or drop in PH or 02
Primary - Adjust respiration to changes in blood chemistry
Secondary - vasomotion
Medullary ischemic reflex does what
The hypothalamus increases bp during stress, anger and arousal
Hypothalamus mediates redistribution of blood flow during exercise and changes in body temp
Medulla oblongata monitors its own..
blood supply
What are the hormones that regulate blood pressure for short term?
- *Adrenal** medulla - Epinephrine/norepinephrine - increases Co and vasoconstriction.
- aldosterone - promotes Na+ and water retention by kidneys
- *Angiotensin** II - Stimulates vasoconstriction- ^BP
- *ADH**(Vasopressin) - promotes water retention - ^BP
atrial natriuretic peptide (ANP) - increases urinary sodium excretion, reduces blood volume and promotes vasodilation - decrease BP
When binds to a-adrenergic receptors the result is
when bind to b adrenergic receptors the result is
a- adrenergic - vasoconstrict
b-adrenergic - vasodilate
Long term mechanisms control BP by regulating
blood volume via kidneys
Kidneys regulate arterial blood pressure by
- Direct renal mechanism (urine elimination or retention)
- Indirect renal mechanism (renin-angiotension-aldosternone)
Decreased arterial blood pressure causes what to release from kidneys..
—– Enters blood and catalyzes the conversion of angiotensinogen from the liver to —–
Renin
Angiotensin I which gets converted to angiotensin II
Angiotensin II acts in what 4 ways to stabilize arterial BP
- Stimulates aldosterone secretion
- Causes ADH to release from posterior pituitary
- Triggers hypothalamic thirst center
- Acts as a potent vasoconstrictor, directly increasing blood pressure
Tissue perfusion is
Blood flow through body tissues at precisely right amount to provide proper function
involved in:
Delivery of O2, nutrients to and removal of waste
Gas exchange
Absorption of nutrients
Urine formation
The rate of tissue perfusion is controlled by what extrinsic and intrinsic factors?
Extrinsic control - Sympathetic nervous system & hormones (reduce flow to regions that need it least)
Intrinsic control (local) - local arterioles undergo a modification of their diameters
What are the 2 intrinsic mechanisms?
What does NO and endothelins do?
Metabolic - change in local chemicals - release NO or endothelins
Myogenic - Muscle - passive stretch or reduced stretch
NO - vasodilator
Endothelins - vasoconstrictor
Syncope means?
What happens when your bp is above 160 mm Hg?
Fainting - Can happen below 60 mm Hg
Above 160 mm Hg can result in cerebral edema
Speed of blood flow is related to cross sectional area. Capillaries have the largest area so they have the —– flow
Slowest - which allows for enough time for exchange between blood and tissues
Molecules pass by —– between blood and interstitial fluid down their _______ ______.
What passes from blood to tissues?
What passed from tissues to blood?
Diffusion
Concentration gradient
Blood to tissues - O2 and nutrients
Tissues to blood - CO2 and metabolic waste
What are the 4 different routes molecules use to cross capillary?
- Diffuse directly through endothelial membrane (except lipids)
- Pass through clefts (water soluble)
- Pass through fenestrations (water soluble)
- Active transport via pinocytotic vesicles or caveolae (proteins/larger molecules)
Direction and amount of fluid exchange at capillaries depend on what 2 opposing forces?
Hydrostatic pressure
Colloid osmotic pressure
What is hydrostatic pressure?
what are the 2 types?
Force exerted by fluid pressing against wall
Capillary (HPc) - bp that forces fluids through capillary walls, 35 - 17 mmHg
Interstitial (HPif) - pressure pushing fluid back into vessel, usually assumed a 0 bc lymphatic vessels drain interstitial fluid
What are the 2 colloid osmotic pressures?
Capillary colloid osmotic pressure (OPc) 26 mmHg- Sucking pressure created by nondiffusible plasma proteins pulling water back into capillary
Interstitial fluid osmotic pressure (OPif) - pressure sucking from interstitial fluid. very little proteins so only around 1 mmHg
Net filtration pressure (NFP) is what formula
Net fluid out at arterial end is?
Net fluid in at venous is?
NFP = (HPc-HPif) + (OPif-OPc)
Filtration
reabsorption
What is edema?
what is it caused by?
Accumulation of excess fluid in a tissue (abnormal increase in amount of interstitial fluid)
occurs when fluid filters into a tissue faster than its absorbed
Caused by increase in outward pressure or decrease in inward pressure
an increase is capillary hydrostatic pressure accelerates….
an increase in interstitial fluid osmotic pressure can result…
a decrease in capillary colloid osmotic pressure hinders…
fluid loss from blood
from an inflammatory response
fluid return to blood (reduced capillary absorption)
Interstitial fluid in subcutaneous tissues generally causes
What are the 3 main causes of edema?
- *Increased capillary filtration**
- Kidney failure, histamine release, old age, poor venous return
- *Reduced capillary absorption**
- Hypoproteinemia, liver disease, protein deficiency
- *Obstructed lymphatic drainage**
- surgical removal of lymph nodes
What are the consequences of edema?
Tissue necrosis
pulmonary edema- suffocation threat
cerebral edema - headaches, nausea, seizures, coma
Severe edema or circulatory shock - low blood volume and pressure
What is hypertension?
Sustained elevated arterial pressure of 140/90 mm Hg or higher
Prehypertension is close to those numbers
Can be seen during fever, physical exertion and emotional upset. Common in obese people
Prolonged hypertension is cause of heart failure, vascular disease, renal failure and stroke
What is hypotension?
Orthostatic hypotension?
Chronic hypotension?
Acute hypotension?
Below 90/60 mm Hg
temp low bp - suddenly rising too fast
chronic - poor nutrition warning sign for hyppthyroidism
acute - warning sign for circulatory shock
Circulatory shock?
Abnormal perfusion
where blood vessels inadequately fill and cannot circulate blood normally; cannot meet tissue needs
What is hypovolemic shock?
Vascular shock?
Cardiogenic shock?
Neurogenic shock?
Septic shock?
Anaphylactic shock?
hypovolemic shock - results from large scale blood loss
Vascular shock - results from extreme vasodilation
Cardiogenic shock - inefficient heart cannot sustain adequate circulation
Neurogenic shock - loss of vasomotor tone, vasodilation (emotional shock to brainstem injury)
Septic shock - bacterial toxins trigger vasodilation and increased capillary permeability
Anaphlyatic shock - severe immune reaction to antigen, histamine release, generalized vasodilation, increased capillary permeability
