Cardiovasc Flashcards
Endothelium
Endothelial cell - SIMPLE SQ, POLYGONAL and ELONGATED.
–>specialized epithelium that acts as a SEMIPERMEABLE BARRIER between BLOOD + INTERSTITIAL fluid
Main function: METABOLIC EXCHANGE between molecules of the blood and tissue through diff mechanisms eg. diffusion, receptor-mediated etc.
Other functions;
1. NONTHROMBOGENIC SURFACE: blood NO CLOT + secretes agents controlling clot formation (HEPARIN, PLASMINOGEN and VON WILLEBRAN factor)
2. regulate vascular tone and BLOOD FLOW by secreting factors that stimulate smooth muscle contraction or relaxation ; ENDOTHELIN or NO (nitric oxide)
3. INFLAMMATION and local immune response …
4. GROWTH FACTORS to promote proliferation of WBC lineages and cells of the wall
–> vascular endothelial growth factor (VEGF) stimulate formation of the vascular system form embryonic mesenchyme (VASCULOGENESIS), help maintain vasculature on adults + promote capillary sprouting (angiogenesis)
5. enzymatic function
*ENGIOPOITIN - stimulate endothelial cells to recruit smooth muscle cells and fibroblasts to form the other tissue of wall.
- diapedesis
layers of large blood vessels (NO CAPILLARIES)
1.T intima - ENDOTHELIAL and a thin SUBENDOTHELIAL layer of LOOSE CT, w rare smooth muscle cells in LONGITUDINAL arrangement
*In arteries; thin layer of INTERNAL ELASTIC LAMINA (ELASTIN) between the intima and media (for DIFFUSION)
2.T media - (thickest) HELICALLY arranged SMOOTH M cells, interposed w ELASTIC fibers and LAMELLAE, RETICULAR fibers PROTEOGLYCANS, collagen type III, GLYCOPROTEINS (all produced by the cells).
*+ EXTERNAL ELASTIC LAMINA at media (separate from adventitia:thinner)
3.T adventitia - LOOSE CT with type 1 collagen and ELASTIC fibers in LONGITUDINAL arrangements
- bound to the stroma
of large vessels; network of UNMYELINATED autonomic nerve fibers - vasomotor releasing VASOCONTRICTOR NOREPINEPHRINE (more in arteries than veins).
supplied by the VASA VASORUM
- arterioles, capillaries and venules in the adventitia and outer media.
–> provides nutrients + oxygen to the cells of tunica
*luminal blood provides for the intima
Elastic Artery
Aorta, pulmonary artery and their large branches (high Pressure); conducting arteries to carry blood to smaller arteries.
d >10mm
same tunica layer
- thick t. intimal - endothelium + subendothelial CT (w lots of smooth m cells)
- internal elastic lamella - tunica media - very thick; elastic lamallae (10um thick) alternate with layer of smooth muscle fibers (circular)
- external elastic memb
3, t. adventitia - loose CT (underdeveloped)
(collagen + elastic fibers)
- vasa vasorum + nerves
Staining;
cross section; HE + trichrome
longitudinal section; ORCEIN
during venrticular (systole) elastic lamellae stretched to reduce force of P. relaxation (diastole) P drops but elastin maintain arterial P
Muscular artery
d= 10-1mm
1. t. intima - endothelium, THIN subendothelial layer and a PROMINENT internal elastic lamina
- LESS ELASTIN and more muscle
- t.media - 40 layers of large smooth muscle cells (circular) interspread with LITTLE ELASTIC LAMELLAR, proteogly, reticular
- external elastic lamina only in the larger muscular arteries
- control blood flow to organ by contracting/relaxing smooth m. - t. adventita - CT (collagen + elastic fiber) w LYMPHATIC capillaries, VASA VASORUM and nerves
Branches= microvasculature arteries decrease to 2-3 layer of muscle for exchange of blood and tissue fluid
Arteriole
smallest arteries
- less than 0.1 mm in diameter
- t. intima-endo with round nuclei. THIN subendothelial cells (NO elastic laminae)
- t. media - CIRCULARLY arranged smooth muscle cells (1-3 layer)
- t. adventitia - very THIN and INCOSPICOUS
*at the end smooth m act as sphincters for periodic flow into capillaries.
Venules
transition from the capillaries = postcapillary venule
15-20um =d
- -t.intima endothelium
- t media; smooth m with 1-2
- t adventitita-CT
converge into larger collecting venules; with a t. media of 2-3 layers of smooth m = muscular venules
contain PERICYTES; cells at the intervals of the walls - vessel formation, blood-barrier and immune cell entry.
—> primary site where white blood cells adhere to the endothelium and leave at circulation at affected region
Veins
low P= contraction of the smooth m fibers in the media + external compress by surrouning skeletal muscle moves blood back to the heart
d= 10mm or less
Classified according to development of tunics:
MEDIUM vein:
1. t. intima - THIN w valves (elastic fibers + covered with endothelium)
- valves: most large v have: SEMILUNAR FOLDS of t.intima project in lumen; lined w endothelium; rich in ELASTIC f.
- t. media - smooth m with network of RETICULAR and ELASTIC fibers (CT) - CIRCULAR
- t. adventitia - THICK (well developed) w COLLAGENOUS layer + ELASTIC FIBERS + LYMPHATIC capillaries (LONGITUDINAL)
LARGE v = MUSCULAR VEIN
1. THICK intima - endothelium, subendothelial CT + sporadic smooth muscle cells (circular)
- THIN media - smooth muscle circular with CT+ elastic
- THICKER adventitia - longitudinal bundles of smooth muscle
+ CT (longitudinal)+ elastic
Capillaries
Capillary beds = network of capillaries
- its density depends on the metabolic activity of tissue
- higher metabolic rate (kidney, liver etc.) have more capillaries. lower MR (smooth muscle, dense CT) have less.
–>supplied by the terminal arteriole branches = METARTERIOLE - act as precapillary sphincters (has smooth m; control blood flow) -> continuous w THROUGHFARE CHANNELS (lack muscle)-> POSTCAPPILARY VENULE
Capillaries
- composed of SINGLE layer of ENDOTHELIAL cells rolled as tube with a basement membrane w TIGHT junctional
- 4-10um=d (transit of blood cells one at a time) and 50um long; (5%=300ml of blood traveling through)
- total length 100,000 km and 5000m^2
- THIN WALLS for gas exchange
continuous cap
–> regulate the exchange of material
- SOLID endothelial lining with OCCLUDING junctions (minimal fluid leakage)
- most common type found in muscles, nerve, exocrine, respiratory tissue and skin
- completes TRANSCYTOSIS of macromolecules (PINOCYTOTIC vesicles)
fenestrated cap
—> extensive molecular exchange (rapid)
- THIN SQ ENDOTHELIAL cells with PORES in the cytoplasm+ continuous basement membrane
- fenestration are around 80nm in diameter
some covered by thin DIAPHRAGM OF PROTEOGLYCANS
- found in the endocrine tissue, glands, kidney, intestines, choroid plexus
discontinous= sinusoidal cap
- maximal exchange of MACROMOL and cells
- ENDOTHELIUM with LARGE PORES, NO DIAPHRAGMS + IRREG INTERCELLULAR CLEFT
- have a DISCONTINOUS basement membrane
- 30-40um, slow down blood flow
- found in the liver, spleen, bone marrow
Pericytes
- mesenchymal cells with long cytoplasmic processes surrounding the endothelial layer.
- found in the POSTCAPPILARY VENULES and CAPILLARY
- secrete ECM components and form their own BASAL LAMINA (which fuses with the basement membrane of the endothelial cells)
- cytoskeleton networks; MYOSIN, ACTIN and TROPOMYOSIN for dilation and constriction.
- In the CNS ; BLOOD-BRAIN barrier
- participate in REGENETATION of tissues as stem cells and after injury can become smooth muscle
lymphatic system
thin-walled endothelial channels (lymphatic capillaries) drain excess interstitial fluid (lymph nodes)-> blood
rich in lightly stained protein (NO rbc), has lymphocytes +WBC
lymphatic capillaries- ONE layer of THIN ENDOTHELIAL cells
- NO TIGHT junction; rest on a DISCONTINOUS BASAL LAMINA
- ANCHORING FIL of collagen extend from basal lamina-> CT (prevent collapse)
- domains of adj endothelial cells (NO HEMIDESMOSOME) extend to the lumen = VALVE
- found in many tissue except CNS, bone marrow, cartilage, teeth, placenta and thymus
lymphatic vessels - THIN WALLS, high CT and smooth muscle
- have valves
- interposed in the path are the L.N
- converge as the thoracic duct (left internal jugular-> left subclavian v) and the right lymphatic duct (right internal j v)
- similar to veins but adventitia is UNDERDEVELOPED only with VASA VASORUM and neural network
Layers of heart
- internal ENDOCARDIUM
- inner layer: of SQ ENDOTHELIAL cells + SUBENDOTHELIUM loose CT
- middle layer: smooth muscle = MYOELASTIC + DENSE CT, w ELASTIC fibers and COLLAGEN fibers
- deep layer: SUBENDOCARDIAL LOOSE CT merging w the myocardium
- V, N, branches of impulse-CONDUCTING system are in this layer (PURKINJE fibers using gap junction) - MYOCARDIUM - THICKEST layer
- cardiac muscle cells (CARDIOMYOCYTES)
- fibers are arranged SPIRALLY around the chambers; thicker in ventricles than atria
- separated by the PERIMYSAL LOOSE CT separates fascicles - EPICARDIUM - external layer
- MESOTHELIUM (simple sq) + FIBROELASTIC layer + SUBEPICARDIAL CT (loose CT) w BLOOD VESSELS AND N
- corresponds to the VISCERAL layer of the pericardium = SEROUSMEMBRANE where heart lies
- Reflects back as a PARIETAL layer where the VESSELS enter and exit the heart
-In between the layers there is small lubricant FLUID (facilitate heart mov) + cushioning ADIPOCYTES
- fluid is produced by the both layers of the serous mesothelium cells
- facilitate heart movements
VALVE/septa: DENSE FIBROUS CT, strong fibrous rings part of fibrous sk (dense fibrous region around valves; base is origin+ insertion for cardiac m)
Regions of dense irregular CT have diff functions:
- anchoring the heart valves
- insertion of the cardiac muscle
- coordinates heartbeat by electrical insulation between the atria and ventricles
conducting system
SUBENDOCARDIAL layer, composed of modified cardiac muscle cells+ spread to the myocardium for contractions
By 2 nodes of specialized myocardial tissue at the right atrium.
sinoatrial node –> atrioventricular node -> AV bundle and subendocardial conducting network
1.SA pacemaker near the SVC
6-7 mm^3 mass of cardiac muscle with myofibrils and intercalated disks
–> impulse initiates and moves along the myocardial fibers contracting the ATRIA.
AV: floor of the right atrium next to the AV valve
composed of the SA cells but have the cytoplasmic projections forming an AV bundle to the interventricular septum (bundle of HIS) into the wall of each ventricle (modified cardiac cells w GAP JUNCTIONS)
–> stimulate depolarization of cells
At the apex bundles divide into the conducting network =
Purkinje fibers
- peripheral MYOFIBRILS with 1+ central nuclei
- pale-staining fibers
- high in GLYCOGEN
–> penetrate myocardium to trigger conduction to both ventricles
