Histology plus Flashcards
Where is the endocardium thicker?
Atrium
How are adhering jxns connected?
Actin filaments
What are purkinje cells?
Specialized cardiac myocytes connected via intercalated discs and gap jxns with fewer myofibrils and few mitochondria
What is the shape change associated with myocardium from endocardium to epicardium?
Longitudinal to oblique myocardium
What types of cells have intercalated disks?
Myocytes (connected in series) and purkinje fibers
What does titin attach to?
Connects thick filaments (myosin) to Z line
What is the difference between cardiac titin and skeletal titin?
Cardiac titin is shorter and stiffer. Can’t lengthen past passive tension, ensuring you don’t overstretch muscles
What is a thin filament?
2 strands of actin coiled together with tropomyosin and troponin
What is a thick filament?
About 200 myosin molecules
What is the Z line?
end of sarcomere
What is the I band?
Thin filaments only
What is the A band?
Thin and thick filaments
What is the M line
Middle of the sarcomere
What is the H zone
Myosin only
Which type of blood vessels only have intima?
capillaries
Aortic intima
Endothelium, connective tissue, internal elastic lamina
Aortic media
Many elastic laminae, much smooth m
Aortic adventia
Thinner than the media, external elastic lamina, vaso vasorum
Muscular artery intima
Endothelium, CT, internal elastic lamina
Muscular artery media
Some SM, no elastic laminae
Muscular artery adventia
Thinner than media, external elastic lamina is larger, fewer vas vasorum than aorta
Role of muscular arteries
Control regional blood flow (distributing vessels)
Arteriole intima
Endotehlium, CT, slight internal elastic lamina
Arteriole media
sl SM
Arteriole adventia
Very thin, no external elastic lamina or vaso vasorum
Capillary intima
Endothelium, basement membrane only
–>capillaries only have intima
Venule intima
Endothelium, sl CT
Venule media
None, sl SM
Venule adventia
Very thin, no EEL or vaso vasorum
Vein intima
Endothelium, CT
Vein Media
Some SM no elastic laminae
Vein adventia
Thicker than media, no EEL, few vaso vasorum
What do fibroblasts and smooth muscle have in common?
They both contribute to ECM
How does the adventitia of small BVs differ from that of larger BVs?
Not separated from surrounding CTs as it is in larger BVs
Why are elastic laminae of vessels perforated?
To allow for diffusion of nutrients
-Media is not well vascularized so receives nutrients by diffusion through intima
What property of sm cells allows for its decrease in energy expenditure?
Tonic SM has very slow cross bridge turnover. It can also enter latch state in which tension is maintained without cycling of cross bridges (maintains T with little energy, constant stim by SNS)
Compared to skeletal m, how does myosin bind in smooth muscle?
Binds with opposite polarity
What are the secretory functions of smooth muscle cells?
Secrete collagen, elastin, EC matrix
–>all can be altered in disease
Describe the process of contraction in sm cells
Ca/calmod complex–>MLCK–>RLC–>inc ATP binding capacity
3 ways to increase Ca2+ in SM cells
- AP allows ca2+ to flow through plasma membrane via voltage sensitive channels
- Ligand to GCPR–>IP3 allows ca2+ to exit SR
- Stretch–>open Ca2+ channels in the plasma membrane
What can reduce MLCK activity?
- Decrease of cytoplasmic Ca2+
2. Inactivation by ligand binding leading to inc in cAMP causes vasodilation (like epineph)
What activates MLC phosphatase activity?
NO
Takes phos group off of the RLC
What is the internal elastic lamina?
Boundary between intima and media
Do veins have an external elastic lamina?
No!
What layer do you look at to tell the dif between an artery and vein?
Media. Adventitia is thicker than the media
What are the 4 types of capillaries?
- Continuous: tight jxns between endothelial cells, particles must pass through cytoplams and basal lamina to enter/exit lumen
- Fenestrated: endothelial cells have holes, basal lamina is continuous
- Discontinuous: Large gaps between endoth cells and basal lamina is incomplete
- Sinusoids: giant capillary, not really a type, often have discontinuous endothelium
Where do you find fenestrated capillaries?
Kidney, endocrine organs
Where do you find discontinuous capillaries?
Spleen, lymph nodes, liver
What features allow for a greater degree and maintenance of contractility in smooth vs skel muscle?
- Proportion of actin to myosin is much higher
- SM lacks rigid organization into sarcomeres
- Myosin heads bind to a dif actin filament with opposite polarity
List endothelial cell properties
- Anti/prothrombotic properties in all vessels
- Exchange of fluids, gases, solutes in capillaries
- Modulation of cell migration, inflammatory and immune (venules)
- Modulation of vasc SM contractility (arteries, arterioles)
What does endothelial dysfxn result in?
Abnormalities in vascular: T=tone G=growth I=inflammation F=fluidity
List mcs that cause vasoconstriciton
Endothelin
Angiotensin II
Thromboxane A2
Acetylcholine
List mcs that cause vasodilation
NO
Prostacyclin
Bradykinin
ACh
What is the annuli fibrosa of the heart?
- Composed of dense CT that forms aponeurosis
- Serves as a support structure of valves and ventricles
- Electrically isolates atria from ventricles
- Fibrous skeleton is an attachment for the myocardium
Role of delayed rectifier K+ channel
Repolarizes heart and therefore determines the maximum diastolic potential
What ion causes the upstroke in automatic APs?
Calcium (T and L channels)
