Vessels+ Valve Structure/Histology Flashcards
General layers of vascular walls
1) Tunica intima: endothelium + basement membrane
2) Tunica media: smooth muscle, collagen, elastin
3) Tunica adventitia: loose connective tissue + blood + nerves + immune cells + fibroblasts
Ways to subdivide arteries
Can be by size (large, medium, small) or wall properties ( large=elastic, medium=muscular, arterioles), or function (large and medium are distributing, small is resistance)
Differences and similarities between elastic and muscular arteries…
Both: media is the thickest layer, thick vessel wall compared to lumen size
Elastic arteries: only have internal elastic membrane, have lamellae of elastic fibers, and an adventia around half the size of media
Muscular:, have internal and external elastic membrane, no lamellae (less elastin), travel with veins, large adventitia
Function and structure of arterioles
- They are resistance vessels
- Have all three tunics, and media has 1-3 layers of smooth muscle
- Are small… only contain 10-15 RBCs at a time
- Usually travel with venules
Differences between arterioles and venules
Arterioles: round lumen, thicker wall
Venules: irregular lumen, thinner wall, discontinuous smooth muscle
Atherosclerosis
-natural course
1) In larger vessels there is injury of the endothelium.
2) Lipids accumulate in intima
3) Inflammation. Macrophages eat lipids become foam cells
4) Core is foam cells, lipid droplets, dead cells. Outside is fibrous cap
3 types of capillaries, function and location
1) Continous: endothelial cells joined together. Muscle, lung, CNS (anywhere there is a blood-tissue barrier)
2) Fenestrated: fenestrations let small molecules move in and out. Endocrine glands, kidney, gallbladder, GI
3) Discontinous: large, discontinuous endothelium. Often associated with specialized cells (e.g. Kupffer cells) No BM. In liver, spleen, bone marrow
Differences between arteries and veins
Veins: have large adventitia, fewer layers of smooth muscle, some veins have valves, layers can be difficult to differentiate
How does blood get back to the heart
- gravity
- one way valves
- skeletal muscle pump
- venoconstriction
- respiratory activity
Similarities and differences between capilaries and small lymph vessels
Both: have single layer endothelium
Lymph vessels: are blind-ended. At the end, cells just overlap each other and open whenever the fluid pressure on the outside is great enough
The 3 layers of the heart wall
Endocardium, myocardium and epicardium
Components of the endocardium
- simple squamous epithelium
- subendothelial connective tissue. collagen. elastin, fibroblasts, some SMCs
How to differentiate between the endocardium and epicardium on a slide?
Epicardium is thinner, usually washed out because it contains fatty tissue, and may have vessels and nerve fascicles
Thickness of endocardium in atrium vs. ventricle
Endocardium around 3X thicker in atrium - it is thicker in areas of lower wall thickness
Function of trabeculae carnae
- help the heart wring itself out
- prevent ventricle walls from sticking
Which part of the pericardium does the epicardium form?
- the visceral serous pericardium
Components of the pericardium
- loose, fatty connective tissue
- mesothelium secretes lubricant
- blood vessels and nerve fasicles
Cardiomyocyte features
- branched
- 1-2 central nuclei
- striated
- lots of mitochondria
- long lived cells
- poor regenerative capacity
- intercalated disks
Intercalated disks function
- electrical and mechanical linkage between cell borders
Intercalated disk components and where they attach
1) fascia adherens (links actin I bands in adjacent cells)
2) Desmosomes (link to intermediate filaments network)
3) Gap junctions: electrical linkage
What is released by atrial myocytes and what does it do?
Atrial natriuretic peptide
- inhibits RAS
- promotes water excretion, and lower BP
- released with atrial myocytes are stretched
Location of purkinje fibers
- the subendocardium in the interventricular septum
How to differentiate purkinje fibers and myocardium
Purkinje fibers appear
- larger in diameter
- washed out
They are also high in glycogen, mitochondria and have peripheral myofibrils
Trabeculae and valves are covered on both sides by….
endocardium
What are the three layers of a valve leaflet? What do they attach to ?
- Fibrosus (collagen)
- Spongiosa (proteoglycans)
- Ventricularis (elastin)
They attach to the anulus fibrosus of the cardiac skeleton
Composition of heart valves: how much collagen and how much elastin?
50% collagen
13% elastin
How to tell lymphatics from arterioles or venules?
- very thin walled
- no obvious media
- no RBCs in lumen
Contrast electrical communication in skeletal vs. cardiac muscle
Skeletal uses motor end plates whereas cardiac relies on gap junctions in intercalated disks
How to differentiate between atria, ventricle and interventricular septum?
Atria: thickest endocardium
Ventricle: thinner endocardium, trabeculae, thicker myocardium
Interventricular septum: two layers of endocardium, purkinje fibers
Where are T-tubules in skeletal vs. cardiac muscle cells?
Skeletal: at level of A band
Cardiac: at Z-line
more likely to form dyads in cardiac muscle vs. triads in skeletal muscle
How to find SER on ERs of cardiac muscle
- the little tubes that run between myofibrils
How to recognize gap junctions
- they look like long-ish zippers in the longitudunal plane
How to recognize different parts of the sarcomere in cross-section
- A bands are double hexagonal (thin + thick filaments overlap)
- Z band- square lattice
- I band: thin filaments, 1/2 as many as in the Z band
What is mitral stenosis usually due to?
Rheumatic fever- not common in north america
