Histology Flashcards
What are the characteristics of smooth muscle fibers with respect to myofibrils, location of nucleus and involuntariness of contraction?
Myofibrils not visible
Nucleus centrally located
Involuntary contraction
What are the characteristics of striated skeletal fibers with respect to myofibrils, location of nucleus and involuntariness of contraction?
Myofibrils visible
Peripheral nuclei (multinucleated)
Voluntary contraction
What are the characteristics of striated cardiac fibers with respect to myofibrils, location of nucleus and involuntariness of contraction?
Myofibrils visible
Centrally located nucleus
Involuntary contraction
What is the band letter at the center of the A band in striated cells?
H
What is the band letter at the center the I band in striated cells?
Z
What separates individual cells?
Endomysium
What separates a bundle of cells from one another?
Perymysium
What is the sheath that surrounds a muscle?
Epimysium
What is the name of the striated muscle cells that has a finger-like projection
Sarcolemma
What is the bundle of muscle fiber that lies before the perymysium
Fascicle
What is a sarcomere?
The repeating unit between two Z lines
What is the protein that holds the Z lines?
Alpha-actinin
What are the two types of filaments in a sarcomere?
Thin filament: F-actin
Thick filament: Myosin filament
What is found at the center of the H band?
The M-line, which is the site of the enzyme “Creatine Kinase”
What does the creatine kinase do?
Allows contraction
When does axon activation occurs?
When acetyl choline (Ach) gets to potassium/sodium receptors
During contraction, what happens when myosin binds actin and cleaves ATP?
Myosin head bends, and the thin filament slides over the thick filament (contraction occurs)
During the mechanism of contraction, what happens when calcium if removed by sarcoplasmic reticulum?
There’s relaxation
Starting from the most external layer, what are the two division of the pericardium (and what are their subdivisions)?
External:
Fibrous pericardium
Serous pericardium
(Serous is further divided in parietal lamina, and visceral lamina)
The endocardium is made of what?
Endothelium
Connective tissue
Smooth muscle tissue
What is the myocardium made of?
Muscle fibers
What is the other name of the epicardium?
Visceral layer of the serous pericardium
In the heart’s sarcomeres, what does the zonula adherens do?
Transmit contractile forces
In the heart’s sarcomeres, what does the macula adherens do?
Maintain stability
What is the Ehlers-Danlos syndrome?
Lack of collagens, affecting connective tissue.
This can cause walls to rupture (high risk of aneurysm)
Neuromuscular disease leading to muscle weakness
Caused by antibodies preventing ACh receptors to get activated
What is the Dx?
Myasthenia Gravis
What is muscular dystrophy (the Duchenne-Becker Dx)
Mutation of dystrophin gene leading to improperly formed muscle
Caused by a lack of laminins that required dystroglycans, which themselves required dystrophins
You see a collapsed blood vessel on the histology image. Is it an artery or a vein?
A vein (arteries are thicker, and will therefore not collapse)
How do we call veins that fail to close to regulate the blood flow?
Varicose veins
What are the causes of varicose veins?
Obesity
Smoking
Pregnancy
Varicose veins can cause what?
High blood pressure
What is the intima made of in muscular arteries?
Endothelium (simple squamous)
Internal elastic limiting membrane
What is a vasa vasorum, and where can we find such a thing?
It’s a small blood vessel that supplies the wall of larger blood vessels.
We can find it in some blood vessels adventitia
What are the three types of capillaries, and their subdivisions?
Impermeable/continuous
Permeable (divided in “Fenestrated” and “Sinusoids”)
What kind of capillaries allow the movement of RBC and WBC between its endothelial cells?
Sinusoid capillaries
How can you distinguish capillaries from post-capillaries venules?
Post-capillaries venules have pericytes around the lumen.
What are the vasoactive substances produced by the endothelium?
Endothelin (vasoconstriction) Nitric Oxide (vasodilatation)
By what metabolic means does the endothelium regulate the blood pressure?
Conversion of angiotensin 1 to angiotensin 2
Inactivation of bradykinin
