Cardiovascular System Flashcards
function of blood vessels
- transport blood throughout body & return lymph to blood
- transport nutrients & O2
- transport waste products
- temperature regulation
- distribution of hormones & cells of immune system
3 major layers of blood vessels
tunica intima
tunica media
tunica adventitia
tunica intima
- endothelial cells (simple squamous epithelium - lines lumen)
- basal lamina
- subendothelial CT
- internal elastic lamina (IEL) - contains elastin, perforated by fenestrae (for nutrients), separates intima from media in arteries
tunica media
-thickest layer in arteries
- smooth muscle
- helically (“circularly”)
- contraction narrows the lumen & helps regulate blood pressure
- make most components of ECM (not fibroblasts)
- matrix includes elastic fibers, reticular fibers, proteoglycans (elastic laminae in elastic arteries)
- external elastic lamina (EEL) - separates media from adventitia (most prominent in muscular arteries)
tunica adventitia
-longitudinally oriented collagen and elastic fibers
-primarily type I collagen
-contains autonomic nerves that innervate the smooth muscle (of media)
-vasa vasorum (vessels of the vessels)
-supply the adventitia and media with nutrients
-more numerous in veins than in arteries
-adventitia blends into the surrounding connective tissue
functions of endothelial cells (9 total)
- permeability barrier
- maintain basement membrane
- type IV collagen & laminin
- promote thrombus formation (von Willebrand factor III)
- minimize pathological thrombus formation (NO, prostacyclin)
- secrete vasoactive factors (endothelin - vasoconstrictor, NO - vasodilator)
- secrete growth factors (FGF, PDGF)
- synthesize cell adhesion molecules (P & E selectins & integrins)
- secrete interleukins (IL-1, IL-6, IL-8)
- storage of products in Weibel Palade bodies (derived from golgi)
Of arteries, veins, and lymph vessels, which act as high pressure and which at low?
High - arteries
Low - veins, lymph
Which carry blood to the heart & which away?
To - Veins
Away - Arteries
Arteries
- high pressure
- carry blood away from heart
- travel with one or more veins in neurovascular bundle
- smaller lumen than vein
- thicker tunica media than vein
Elastic vs Muscular arteries
Elastic
- IEL - no thicker than elastic laminae of tunica media
- lots of fenestrated elastic laminae in media
- allows for rapid expansion & recoil (pulsatile flow-> continuous flow)
- no distinct EEL
- has vaso vasorum in adventitia
- fibroblasts are predominant cell type in adventitia
Muscular
- subendothelial layer of intima is thinner (increases with age)
- IEL - prominent, often appears scalloped
- few elastic fibers in media
- EEL - fragmented, extends into adventitia
- vaso vasorum - absent in smallest
- distributes blood to different regions of body
Arterioles
- smaller than arteries
- regulate blood pressure
- control distribution of blood to capillary beds via precapillary sphincters
- intima - may or may not have IEL
- media - about 2-3 layers of smooth muscle, EEL - absent in smallest arterioles
- adventitia - sparse
Atherosclerosis
- most common form of arteriosclerosis
- fatty plaques in tunica intima -> fibrosis & calcification
- lipid accumulates in macrophages (“foam cells”)
- limits blood flow and can cause ischemia
Pericytes
- undifferentiated mesenchymal cells - can differentiate into endothelium or smooth muscle
- found around capillaries & postcapillary venules
Function of capillaries & what allows them to carry out this function
Function - metabolic exchange between blood & surrounding tissues
- 7-9micrometers in diameter - allow for single blood cell passage
- large surface area of capillary network -> low pressure, cells move through slowly (more time to do nutrient exchange)
What are the 3 types of capillaries?
continuous
fenestrated
discontinuous
continuous capillary
-found in most tissues
-tight junctions
-no fenestrations
have pinocytotic vesicles
fenestrated capillary
- GI tract, kidney glomeruli, endocrine organs
- have fenestrations or pores
discontinuous capillary (sinusoid)
- liver, bone marrow, spleen, adrenal cortex
- leakiest type
- wider lumen
- large gaps between endothelial cells
- basal lamina may be discontinuous or absent
metarterioles
- smallest arterioles
- branch from arteriole toward capillaries/veins
- discontinuous layer of smooth muscle
- have precapillary sphincters
arteriovenous anastosmoses (AV shunt)
- connects arterial and venous sides with no capillary bed
- good for maintaining core body temperature (prevents heat loss at skin)
What is a portal system?
two capillary beds connected by one or more arteries or veins (eg. vein-vein or artery-artery)
Where can you find an arterial portal system?
Kidney
Where can you find a venous portal system?
Hypophysis, GI tract & liver
Postcapillary venules (PCV)
- right after capillary
- wider diameter (can accommodate 2-3 RBDs side-by-side)
Where does diapedesis of leukocytes occur?
postcapillary venules
Where is the most sensitive site for vasoactive mediators such as histamine and serotonin?
postcapillary venules
Muscular/Collecting venules
- where postcapillary venules merge or enlarge
- large diameter (up to 1mm)
- have turnica media (1-2 layers of smooth muscle)
- have thin tunica adventitia
How much of the blood do veins hold?
70%
Veins
- low pressure
- larger lumens than arteries
- thinner walls than arteries
- media thinner than that of arteries
- have valves to prevent backflow (extension of intima)
What is the thickest layer of the vein wall?
adventitia
What is unique about the inferior and superior vena cava?
have longitudinally arranged smooth muscle in adventitia
What is the surface area of the capillary network in adults?
6000 sq ft
adults have 60,000 miles of capillaries
Nerves of what nervous system innervate the smooth muscle of blood vessels?
autonomic
sympathetic - norephinephrine - vasoconstriction
-skin & kidneys (most common), heart & cerebral vessels (rare)
sympathetic - acetylcholine (ACh) - vasodilation
-blood vessels in skeletal muscle
parasympathetic - ACh or NO - vasodilation
salivary glands, erectile tissue of the penis
Lymph vessels
- low pressure
- return interstitial fluid to the great veins at the root of the neck (…my question….what makes them so great? lol)
- NO BLOOD
Lymphatic capillaries
- single layer of endothelial cells, absent or discontinuous basal lamina
- anchoring filaments connect incomplete basal lamina to perivascular collagen (prevent collapse)
- have valves
- absorbs excess tissue fluid & macromolecules (not blood)
- lacteals in intestinal villi - absorb chylomicrons
Larger lymphatic vessels
- many valves
- larger lumens
- thinner walls
- more irregular shape
- variation in wall thickness
What are the largest lymphatic vessels?
right lymphatic duct & thoracic duct
What causes the fluid to move into the venules from surrounding interstitium?
osmotic pressure created by high concentrations of albumin
What causes the fluid to move out of the capillaries and into the interstitium?
hydrostatic pressure created by blood flow against capillary walls
Pressure & fluid movement for arterial side and venous side of the capillary bed
arterial side
hydrostatic > osmotic
fluid forced out
venous side
osmotic > hydrostatic
fluid comes in
Causes of edema
- Increased venous hydrostatic pressure - left side heart failure & pulmonary edema
- Obstruction of lymphatic drainage - axillary node removal or radiation damage
- Increased permeability of endothelium - burn victims
- Decreased osmotic pressure of blood - hepatic cirrhosis or malnutrition (abdominal ascites)
Route that blood flows through heart/body
Lungs -> pulmonary vein -> left atrium -> bicuspid/mitral valve -> left ventricle -> aorta -> systemic -> vena cava -> right atrium -> tricuspid valve -> right ventricle -> pulmonary artery -> lungs
3 layers of cardiac wall
endocardium
- CT made of up elastic and collagen fibers
- no adipose
- contains the impulse conducting systems of ventricles
myocardium
- cardiac muscle
- dense capillary beds
- thicker in ventricles than atria
- thicker in left side than right side of heart
epicardium
- contains large blood vessels
- abundant adipocytes
- autonomic nerves
- outermost layer -> visceral pericardium
- thicker than endocardium
- blends into myocardium
What is papillary muscle connected to in the heart?
chordae tendineae
Myocardial infarction
- loss of cross striations and myocytes
- infiltration of leukocytes
- replacement of dead myocytes with CT (makes stiff)
- reperfusion needs to happen in <20 min to prevent cell death
Aortic dissection/aneurysm
- large longitudinal tear in aortic wall
- causes fluid accumulation between intima and media
Sinoatrial (SA) node
- pacemaker
- pale cells (lots of glycogen, few myofilaments)
- no intercalated discs
- adrenergic and cholinergic nerve endings present
- in wall of right atrium near entry point of superior vena cava
Atrioventricular (AV) node
- morphologically similar to SA node
- receives impulses from SA node
- in wall of right atrium, superior to septal cusp of tricuspid valve
Atrioventricular bundle (bundle of His)
- extends from AV node
- branches to right and left
- ends in Purkinje fibers
Purkinje fibers
- pale cells (lots of glycogen, few myofilaments)
- larger than ordinary contractile ventricular myocytes
- no T-tubules
- irregular Z-lines
Chordae tendineae
CT surrounded by outer layer of endocardium
Papillary muscles
core cardiac muscle surrounded by outer layer of endocardium
Semilunar valves
- 3 pocket-shaped cusps
- pulmonic - between right ventricle & pulmonary artery
- aortic - between left ventricle and aorta
Cardiac skeleton
- dense collagenous CT (NOT bone or cartillage)
- anchoring point for atrial and ventricular myocytes
- heart valves are continuous with the cardiac skeleton
- components
- 4 annuli fibrosi (aorta, pulmonary artery, and AV valves)
- 2 fibrous trigones (right and left, unite annuli fibrosi)
- septum membranaceum
