Module 2 Flashcards
What are the three wall layers in arteries and veins from inside to out?
Tunica Exerna
Tunica Media
Tunica Interna
What are the 5 types of blood vessels?
Arteries, Arterioles, Capillaries, Venules, Veins
What is the Tunica Externa composed of?
Elastic and Collagen Fibers or connective tissue
What does the Tunica Externa contain/do?
- Nerves of Vessels, Vasa Vasorum (Transport O2/Nutrients to cells of BVW)
- Seen on Large Vessels like the Aorta
- Anchors vessels to surrounding Tissues
What are the three parts of the Tunica Intima (From external to internal)?
- Internal Elastic Lamina
- Basement Membrane
- Endothelium
Describe the Internal Elastic Lamina
- Found ONLY in Arteries/not veins
- Seperates between Intima and Media
- Composed of thin sheets of elastic fibers
- Variable Window like openings (Facilitates diffusion from Interna to Media)
Describe the Basement Membrane
- Physical support for Epithelial layer
- Network of collagen fibers (tensile strength, strength/recoil)
- Anchors Endothelium to CT
- Regulates molecular movement
- Guides cell movement during tissue repair
Describe Endothelium
- Lining of Lumen
- Continuous
- Helps inhibit platelet aggregation
- Reduces friction/damage
- Secretes Chemical mediators/influences contractile smooth muscle
- Assists capillary permeability
Describe Arteries and the two major types
- Transport mostly oxygenated blood from heart to the tissues of the body
- Thicker than veins in tunica media
- Plentiful elastic fibers, stretch and expand easily
2 Major:
- Elastic
- Muscular
What are some characteristics of Elastic Arteries?
- Largest Diameter (Aorta, Pulmonary Trunk, carotids, illiacs)
- Vessels walls, thin 1/10th
What is in the Tunica Externa (Adventitia) of Elastic Arteries?
Fibroblasts, Nerve Fibers, Vasa Vasporum
What is in the Tunica Media of Elastic Arteries?
- More Collagen
- Minimal Smooth Muscle
- More elastic fibers (Elastic Lamellae)
What is in the Tunica Intima of Elastic Arteries?
- First place to see Atherosclerosis
- Has supporting layer of Elastin Rich Collagen
(including Endothelial/Myointmal Cells)
Explain pressure reservoir that exists in Elastic Arteries
Momentary Storage of mechanical energy due to expansion of blood pressure (Recoils to make into kinetic energy)
What is another name for the Elastic Arteries?
“Conducting Arteries”
What is another name for Muscular Arteries
“Distributing Arteries”
How does the Tunica externa layer differ in Muscular vs Elastic Arteries?
Much Thicker
How does the Tunica Media layer differ in Muscular vs Elastic Arteries?
- More Smooth Muscle/Less Elastic
- Greater Vasodilation/Vasoconstriction
- Adjusts rate of blood flow
- Can’t propel (little elastic)
Describe Vasomotor/Vascular Tone
- Muscle contracts maintaining a state of partial contraction to maintain vessel pressure and efficient blood flow
Define Anastomoses
Two or more arteries supplying blood to the same region of the body
What are end arteries?
Arteries that do not anastomoses
What is collateral circulation?
Anastomoses provide alternate routes for blood to reach an organ
What are the characteristics of Arterioles?
- approx 400mil
- 15-300um
- Rich in Smooth Muscle
- Wall Thickness 1/2 of total vessel diameter
Explain the composition of the Tunica Externa of Arterioles
- Areolar Connective Tissue containing abundant unmyelinated sympathetic nerves
- Contains local Chemical Mediators (Can alter diameter, therefore blood rate and resistance)
Explain the composition of the Tunica Media and Tunica Intima of the Arterioles
- Both very thin
How does a high and low rate of firing affect the arteries?
Higher Rate- Vasoconstriction
Low Rate-
Vasodilation
What is another name for Arterioles due to their ability to dilate and constrict?
Resistance Vessels- Resistance from blood rubbing against vessel wall (smaller diameter, increased resistance)
How does contraction of smooth muscle in arterioles affect resistance?
Smaller Diameter: Vasoconstriction creates greater resistance, increased BP
Greater Diameter:
Vasodilation creates less resistance, lower BP
What are Metarterioles?
- Short vessels that connect arterioles to capillary networks
- Formed by single smooth muscle cell rings.
What is the purpose of Metarterioles?
- Act as precapillary sphincter that regulated blood flow into the capillaries that branch off the Merarteriole
- Can close of capillary bed
What are capillaries?
Smallest blood vessels , 20 billion, surface area allows for nutrient exchange
What is the composition of capillaries?
- Single endothelial layer and basement membrane (No media/externa)
- Allows for nutrient, gas, waste diffusion
What is the PRIMARY function of Capillaries?
- Exhange of substances between blood and insterstital fluid
What is another name of capillaries?
“exchange vessels”
What three structures are capillaries absent? Why?
- Absent in avascular substances
- Cornea, Lens of Eye, Cartilage
What areas have higher metabolic demand for capillary networks?
Muscles, Brain, Liver, Kidneys, Nervous System
What is a capillary bed?
- Network of 10-100 Capillaries that arise from a single metarteriole
Explain the activity of Capillary beds at rest and active
- At rest, only a small portion of capillary beds are active
- At active the capillary bed opens blood flow in
What is Vasomotion?
- Contraction and relaxation of precapillary sphincters to ensure capillary beds receive blood flow even at rest.
- Due to chemical release of nitric oxide
What is a Thoroughfare Channel?
Direct route from arteriole to venule, bypassing majority of capillary bed. Very little chance for nutrient exchange.
When is the Thoroughfare Channel utilized?
Hemorrhage, Increased Stoke Volume (Exercise)
What are the three types of capillaries?
Continuous, Fenstrated, Sinusoids
Describe Continuous Capillaries
- Most are Continuous
- Continuous tube interrupted only by inter cellular clefts
- Found in CNS, Lungs, skin, muscle tissue
Describe Fenstrated Capillaries
- Plasma membranes have many fenstrations (pores) allowing for easier diffusion
- Found in Kidneys, Villi (SI), most endocrine glands, ciliary processes of the eye
Describe Sinusoids
-Wider/Winding
- Incomplete/Absent membranes
- Large Fenstrations
- Large Clefts
- Contain specialized lining cells adapted to the function of the tissue
(Spleen, Marrow, anterior pituitary, adrenal glands)
What are Portal Systems?
- When one capillary network feeds into another
- Ex. hepatic portal (liver), hypophyseal portal (pituitary)
In what part of the body is the portal system most beneficial?
Hepatic- allows liver to filter blood from:
- Stomach, Spleen, pancreas, gallbladder, mesenteric systems
What are post capillary venules?
- Small Veins that recieve blood directly from capillary beds (porous for WBC (Immune Response))
- Last site of metabolic exchange
What are Musculary Venules?
- Changes from precapillary venules when gaining 1-2 layers of smooth muscle, preventing metabolic exchange
What venules are the most distensible?
Both postcapillary/muscular venules, 360%
What are veins and their layers?
- Thinner than Arteries
- Lumen tend to be larger than Arteries
- Ooz not squirt
- Not meant to withstand lots of pressure
Tunica Externa:
- Thickest Layer (Collagen/Elastic)
Tunica Media:
- Much thinner, less smooth muscle/elastic fibers than arteries
Tunica Intima:
- Much Thinner than arteries
Where and what purpose are valves in the veins?
- Thin folds of Tunica Interna (Cups)
- Prevents backflow due to low blood pressure
One Way Valves exist in small anastomosing vessels to deep veins, to prevent reverse flow
What are Vascular Sinus?
- Thin endothelial wall, no smooth muscle
- Ex. Coronary Sinus
What are anastomic veins?
- Veins paired and accompany medium to small sized muscular arteries
- Greatest # in limbs
- Largest: Superior Anastomic Vein
What is the difference between Superficial and Deep Veins?
- Superficial: lie within the subcutaneous layer of the skin
= Much larger
= Pathway for capillaries of upper limbs - Deep: Travel between skeletal muscles
=Smaller
= Principle return pathway to heart
At Rest, divide the percentages of where blood exists in the body?
64% Veins/Venules 13% Systematic 7% in systemic Capillaries 9% in Pulmonary BV 7% in Heart
What are the three basic mechanisms for capillary exchange?
Diffusion, Transcytosis, Bulf Flow
What is the most important mechanism for Capillary Exchange?
Diffusion
What is the general concentration gradient between interstitual/Blood?
- Interstitial Fluid:
- CO2/ Wastes (High)
- Blood:
- O2/Nutrients (High)
- Diffusion down their concentration gradient
What structures/substances are touched by Diffusion?
- Intercellular Clefts
- Fenstrations- Glucose and Amino Acids
How are brain capillary diffusion different from other capillaries?
- Only water/some gases/Lipid soluble molecules pass through
- Glucose and Amino Acids are selectively transported
- Very Tight Junctions hence Blood/Brain Barrier
Describe Trancytosis
- Enocytosis followed by Exocytosis
- Used mainly for large, lipid in-soluable molecules (Insulin)
What is bulk flow?
Passive process by which large number of ions/particles/molecules in a fluid move together in the same direction
How is bulk flow different from diffusion?
- Bulk flow rate is much greater than diffusion
- Bulk moves from high to low as long as there is a pressure difference
- Bulk is more important for regulation of blood volume/interstitial fluid
What are the two types of Pressure-Driven Bulk flow?
- Filtration/Absorption
What is filtration and the two pressures that promote filtration?
- From blood capillaries into interstitial space
Blood Hydrostatic Pressure(BHP)
Interstitial Fluid Osmotic Pressure (IFOP)
What is Re-absorption? What promotes it?
- From interstitial fluid into blood
Blood Colloid Osmotic Pressure (BCOP)
What is the Net Filtration Pressure? (NFP)
- Balance of filtration and re-absorption
- Determines if they are steady or changing
What is Starling’s Law of Capillaries?
Volume of Solutes reabsorbed is near the volume of fluid filtered
What is BHP?
Blood Hydrostatic Pressure- pressure that blood exertes against blood vessel walls
- “Pushes”fluid out of capillaries into interstitial space
What is IFOP?
Interstitial Fluid Osmotic Pressure- “Pulls” fluid out of capillaries into interstitial space
What is BCOP?
Blood Colloid Osmotic Pressure- forced caused by colloidal suspension of protein in plasma
“Pulls” fluid from interstitial spaces into capillaries
What is IFHP?
Interstitial Fluid Hydrostatic Pressure- opposing pressure to BHP
“Pushes” fluid out of interstitial spaces back into capillaries
What is the percentage of fluid filtered and reabsorbed?
85%/20L
17L/3L in Lymphatic
What two factors affect how cardiac output becomes distributed into the circulatory routes?
Flow/Resistance
How is flow described and its factors?
- Pressure gradient from one end of the tube to the other
- Radius of the tube to the fourth power
- Viscosity of the Fluid, Length of the tube
What are the four principles of flow?
- Directly porportional to longitudinal pressure gradient
- Inversely proportional to the length of the tube
- Inversely proportional to viscosity of the fluid
- Directly proportional to the 4th power of the radius of the tube
What factors affect resistance?
- Radius of the tube to the fourth power
- viscosity and length of the tube
What are the three factors of Vascular Resistance?
- Size of the Lumen
- Blood Viscosity
- Total Blood Vessel length
What two major things affect Blood Viscosity?
- Ratio of Solids to Fluid
- Higher viscosity, higher resistance, slower flow
How is Resistance characterized in total blood vessel length?
- The longer the vessel the greater the resistance to blood flow
Define SVR
Systemic Vascular Resistance- All vascular resistance offered by systemic blood vessels
(TPR) Total peripheral resistance
What structures contribute most to vascular resistance and why?
Arterioles, capillaries, venules- because of lumen size
Explain the relationship between cross-sectional area and velocity?
As cross sectional area increases, velocity decreases
- Velocity is slowest in the capillaries due to the size of its surface area in relation to arteries where it is the fastest
Where is flow generally located in the lumen?
Laminar Flow, or center of the vessel/lowest is near the vascular wall
How is turbulent flow characterized?
Irregularities in flow patterns, typical is pathological patients
What two mechanisms assist in returning blood to the right side of the heart?
Skeletal Pump
Respiratory Pump
Explain the skeletal pump
Standing at Rest- Venous valves are allowing blood towards the heart
Standing compresses the veins resulting in milking to overcome gravitational forces
Explain valve closures and openings when contraction and relaxation of the lower muscles
Contraction: Distal valve closes, proximal opens
Relaxation: Proximal valve closes, distal opens
Describe the Inhalation portion of the respiratory pump
Inhalation is when the diaphram moves downward causing decrease in thoracic cavity, increase in abdominal pressure
- Veins in the abdominal cavity are compressed and blood moves up towards the heart
Describe the Exhalation portion of the Respiratory Pump
Diaphragm moves upward increases thoracic cavity pressure, decrease in abdominal, abdominal valves close preventing backflow
How is Blood Pressure determined?
Cardiac Output, Blood Volume, Vascular Resistance
Systolic BP
Highest BP in Arteries
Diastolic BP
Lowest BP in arteries
What is MAP
Mean arterial Pressure is 70-100
What areas do the interconnected negative feedback system affect?
HR, SV, SVR, Blood Volume
What does the CV Center do?
Regulates HR, Contractility, Blood vessel diameter
