Cardio Flashcards
T/F: smooth muscle has 1 nucleus
True
______capillaries have pores and are seen in liver/spleen/lymph/bone marrow/some endocrine glands
Sinusoidal
Where do we get the name “striated muscle”?
Highly organized arrangement of filaments within the muscle cell
(this gives a characteristic alteration of light and dark bands when viewed in longitudinal section)
Derivations of “sarco”, “myo”, and “mys” are generally used in relation to _____.
muscle
Define sarcolemma
Muscle cell membrane
Define sarcoplasm
Cytoplasm of muscle cells
Define sarcoplasmic reticulum
Highly specialized membrane system derived from the muscle endoplasmic reticulum
Why is smooth muscle referred to as involuntary?
It is regulated by the autonomic nervous system, hormones, or local physiological conditions
Where is smooth muscle found (7)?
- GI tract
- Wall of urinary tract
- Reproductive system
- Blood vessels
- Gland ducts
- Respiratory system
- Dermis
Describe the shape and the nucleus location of smooth muscle cells.
- Fusiform shape
- Single nucleus located in the thickest central portion of the cell
Describe the nucleus of a fusiform - shaped cell in longitudinal cross section when contracted vs. relaxed?
Contracted: cork screw appearance
Relaxed: round
Describe the histological appearance of multiple smooth muscle cells in cross section.
- Packed with the narrow part of one cell lying adjacent to the thick (nucleus - containing) portion of another cell.
- In cross-section we see a range of diameters, the thickest having a nucleus in the center
Which organelles are present adjacent to each pole of a smooth muscle cell nucleus?
- Polyribosomes
- RER
- Golgi
- Mitochondria
Do smooth muscle cells contain T tubules?
No
Describe the sarcoplasmic reticulum of smooth muscle cells (3).
- Continuous w/RER
- Rudimentary and scattered throughout the sarcoplasm
- Contains Calcium binding proteins (Calsequestrin)
Define caveolae.
Structures involved in calcium sequestration
(near cell surface & look like pinocytotic vesicles)
Why is smooth muscle “smooth” and not “striated”?
Myofilaments are NOT arranged in an organized manner, as striated muscle is.
What are the three types of filaments found in smooth muscle sarcoplasm?
- Thin filaments
- Intermediate filaments
- Thick elements
What are thin filaments of smooth muscle cells coposed of?
Actin and tropomyosin (NO TROPONIN)
What are intermediate filaments of smooth muscle sarcoplasm composed of?
Desmin
What are thick filaments of smooth muscle sarcoplasm composed of?
Myosin
What is unique about the arrangement of thick and thin filaments in smooth muscle?
- *Thick filament**: myosin heads all along the length of the filaments
- *Thin filaments:** longer & 3 xs more than skeletal m.
(casual intermingled association between filaments, not as structured as skeletal m.)
Where do the thin and intermediate filaments insert?
- dense bodies
- dense plaques
Define dense bodies
- Small, poorly defined densities in the cytoplasm
- Possess Alpha actin and other proteins
Define dense plaques
- Similar to dense bodies. Uniform Arrangement on inner surface of sarcolemma
- Composed of actin, vinculin, talin & other proteins
Which two structures of the extracellular components help to transmit & coordinate force of contraction by smooth muscle cells?
Basal lamina
Reticular fibers
Identify:
- Black dots
- Dashed lines
- Fine black lines
- Blue lines
- Black dots = plaques and dense bodies
- Dashed lines = thick and thin filaments (blue & black lines)
- Black lines = Thin filaments
- Blue lines = Thick filaments
List the components of the endocardium (6)
- Endothelium
- Subendothelial connective tissue
- Collagen
- Elastic fibers
- Occasional smooth muscle cells
6.
The endocardium is continuous with _____.
Tunica intima of vessels entering the heart
(consists of elastic fibers, collagen, endothlial cells, subendothelial CT & smooth m.)
Describe The myocardium
- Thickest tunic
- Cardiac muscle arranged in layered, spiral pattern around the heart chambers
Describe the epicardium
- Covered by simple squamous epithelium (mesothelium) & Loose CT (under mesothelium)
- adipose cells and coronary vessels are seen in this layer
How are cardiac myocytes different from skeletal muscle fibers?
- long and branched
- One centrally located nucleus (sometimes 2)
- Lipofuscin granules (in older cells)
How does the t tubule system of atrial myocytes differ from ventricular myocytes?
atria has smaller and poorly developed T tubules system
Cardiac myocytes undergo 60 contractions per minute on average. How does it meet the energy demands for this?
- mitochodria: immediately adjacent to the sarcolemma, wedged between myofibrils and perinuclear space
- Lipid droplets store triglycerides used by mitochondria
(mitochondria make up to 40% of the sarcoplasm compared to 2% and skeletal m.)
How do the T tubules systems differ between skeletal m. & cardiac m.?
In cardiac myocytes:
- T tubules of cardiac myocytes or larger in diameter
- Sarcoplasmic reticulum is less expensive
- diads instead of triads
What are the three important specializations of intercalated discs?
- fascia adherens
- desmosomes (macula adherens)
- gap (nexus) jxns
(yellow arrows in photo)
What is the function and location of fascia adherens?
Function: Attachment site for actin filaments of the terminal sarcomeres
Location: transverse portion of disc (accounts for density of disc; similar to z-disc)
What is the function, location, and composition of desmosomes (macula adherens)?
- *Location**: transverse portion of disc
- *Function**: holding myocyte ends together
- *Composition**: intermediate filament proteins
What is the location and function of gap (nexus) junctions?
- *Location**: lateral portion of intercalated discs
- *Function**: contains connexons (connection channels between myocytes) which allow passage of molecules (1,500 Da)
What is one of the most important factors that allows a wave of contraction to spread throughout the heart wall?
The ability of ions to freely pass through Gap Junctions
What components comprise the fibrous skeleton of the heart? Where are they found?
- Dense irregular collagenous connective tissue with collagen bundles.
- Basis of aorta, pulmonary artery, atrioventricular orifices (annuli fibrosi), aortic valve cusps (trigonum fibrosum), upper atrioventricular septum (septum membranaceum)
fibrous skeleton functions
- Structural support
- Attachment for cardiac muscle
- Structural discontinuity between atria and ventricles (prevents simultaneous contraction)
Constituents of cardiac valves
- Core of fibrous connective tissue
- Endothelial covering
Inflamed cardiac valves can lead to _____ (3).
- Blood regurgitation
- Volume overload
- Heart failure
Atrial contraction must finish before _____
the initiation of ventricular contraction (accomplished by conducting system of heart)
List the highly specialized cardiac myocytes involved in the impulse conduction system of the heart.
- Sinoatrial node
- Atrioventricular node
- AV Bundle/Bundle of His
Where is the sinoatrial node located?
Right atrium, near its Junction with the superior vena cava
Where is the site of initiation of excitation of the cardiac conduction system?
SA node
Describe the histological features of the SA node of the heart
- Cells are pale with few myofilaments
- Gap Junctions
- No intercalated discs
The SA node depolarizes spontaneously at ____ beats per minute.
70
(pacemaker of the heart, but ANS can modify)
Define internodal tract
Cells that carry impulses from the SA node to the AV node
Where is the AV node located?
Lower right side of the interatrial septum
(continuous with the bundle of His)
Purkinje fibers are prominent in the _____ and continue into the _____.
- distal portions of the AV node
- right and left bundle branches
How are purkinje fibers morphologically different from cardiac myocytes ?
- Shorter and wider,
- No intercalated discs
- Pale cytoplasm
- small population of myofilaments (arranged in poorly to find vestigial sarcomeres)
Chronic hypertension can lead to which morphological changes which eventually lead to impaired contractile function?
Thickening or hypertrophy of The ventricle wall
Define calcium paradox
Rapid return of blood flow to ischemic tissue can cause mycordial cell death due to massive influx of calcium into cardiac myocytes.
Endothelium of Tunica intima
Simple squamous
How are endothelial cells held together in the Tunica intima?
Tight junctions and occasional gap junctions
Describe tunica intima connective tissue
Subendothelial connective tissue and smooth muscle cells
Describe Tunica Media
- Middle layer
- Circumferencially arranged smooth muscle cells
- Extracellular Matrix
Describe the Tunica adventitia
- Outer surface of vessels
- Collagen (type 1)
- Elastic fibers
- Fibroblast
What are the classifications of arteries?
- Large elastic
- Muscular
- Arterioles
Describe the Tunica intima of large elastic arteries
- Endothelium
- subendothelial layer of loose connective tissue
- Occasional smooth muscle cells
- Internal elastic lamina (elastin and fenestrations)
Describe the Tunica Media of large elastic arteries
- 70 fenestrated elastic lamellae (ECM separates each layer)
- concentric arrangement
- SM cells (secrete collagen, reticular fibers, elastin, ground substance)
NO FIBROBLASTS IN THIS LAYER
Describe the Tunica adventitia of large elastic arteries
- Loose irregular connective tissue
- Fibroblasts (UNLIKE THE TUNICA MEDIA)
- Vasa vasorum
Most arteries are of which classification?
Muscular
(aka distributing arteries: control blood distribution to organs)
Define Vasa vasorum
Vessels of the tunica adventitia of thick-walled arteries and veins that provide nutrients to cells that lie in the outer tunics
Large elastic arteries are also known as
Conducting arteries: provide continuous blood flow through vascular system w/reduced fluctuation in blood pressure.
Function of elastic arteries
prevent excessive BP: elastic lamellae of tunica media stretch during systole & relax during diastole
Describe the tunica intima of muscular arteries
Endothelium plus thin subendothelial layer with few smooth muscle fibers
Internal elastic lamina: outermost boundary; causes undulations in tunica intima
Describe the Tunica Media of muscular arteries
- Up to 40 layers of smooth muscle cells
- concentric orientation
- external elastic lamina (outer border)
Describe the tunica adventitia of muscular arteries
- Longitudinally oriented collagen
- Fibroblasts synthesize the collagen and other ECM components
- free nerve endings
- vasa vasorum
(Generally thinner than the Tunica Media)
Describe arterioles
- One to a few smooth muscle layers in the Tunica Media
- rarely internal elastic lamellae
- tunica adventitia poorly defined
*
Describe meta arterioles
- Continuous with capillary beds
- Smooth muscle cells form a sphincter around the vessel where they join the capillary
- Greater diameter than continuous capillaries
(notice how the nucleus buldges into the lumen or the arteriole. The lumen of the venule is larger (more compliant))
Where are pericytes located?
Outside of capillaries and small venules
Describe pericytes
- numerous cytoplasmic extensions wrapping around the capillary
- share gap junctions & basal lamina w/endothelial cells
Function of pericytes
- Regulate blood flow through capillaries
- Division and formation of new vessels and connective tissue is damaged
Most common subtype of capillaries found in connective tissue, muscles, nervs & exocrine glands
Continuous capillaries
Describe continuous capillaries
- No fenestrations
- Tight junctions
- Carrier - mediated transport
Where are fenestrated capillaries found?
- Intestine
- Endocrine glands
- Kidneys
(rapid exchange occures between blood and these tissues)
Describe fenestrated capillaries
- Continuous basal lamina
- Thin diaphragm, non-membranous covering
The endothelium of _____ is more permeable than that of capillaries
postcapillary venules
Leukocytes tend to exit the bloodstream at ______.
postcapillary venules
Describe postcapillary venules
- Blood enters immediately after exiting capillary beds
- Structure is comparable to capillaries (endothelium surrounded by reticular fibers and pericytes)
medium-sized vein
Valves are thin leaflets formed from ____ and are most common in ______.
- Tunica intima projections
- medium veins
Describe the Tunica Media of medium veins
- Loose circular arrangement of smooth muscle cells
- some collagen
- occasional fibroblast
Describe the Tunica adventitia of medium veins
- Thickest tunic
- Elastic fibers
- Collagen bundles
- Some smooth muscles
- Longitudinal arrangement
Large vein (ex: vena cava, pulmonary veins)
Describe the Tunica intima of large veins
Thicker subendothelial connective tissue (than medium veins)
Describe the Tunica Media in large veins
Poorly defined in most large veins, but pulmonary veins have a developed circular smooth muscle layer
Describe the Tunica adventitia enlarged veins
- Thick and well-developed
- Elastic fibers
- Longitudinal collagen
- Vasa vasorum
(large veins lying below the heart have prevalent smooth muscle to move blood against gravity)
Weibel-Palade bodies
Membrane-bound inclusions of arterial endothelial cells that contain glycoprotein coagulating factor
(aka von willebrand factor)
Define arteriosclerosis
Hardening/thickening of arteries and a reduction in elasticity
(mostly pathological but does occur as part of the natural aging)
Secondary hypertension can result from _____.
Arteriosclerosis
Define atherosclerosis
- Atherosclerosis plaque of fibrous and fatty tissue forms in the wall of an artery, reducing lumen size
- Thrombus may form if endothelium is damaged leading to thrombus or embolis
(most common pathological form of arteriosclerosis & leading cause of death in industrialized countries)
Define thrombus
Clot forms when endothelium is damaged and blocks vessel
Define embolus
Clot forms if the end of the alarm is damaged and breaks off into circulation
(eventually lodging in a vessel lumen causing ischemia)
What are the three major functions of capillaries?
- Selective permeability
- Synthetic / metabolic activity
- Auntie thrombogenic function
Describe the synthetic/metabolic activities of capillaries
- Production of growth factors coagulation factors
- Activat a wide range of circulating molecules
Describe the anti thrombotic function of capillaries
- Capillary endothelial cells produce anti-coagulants and inhibitors of platelet aggregation
- Barriers between platelets and subendothelial tissue
Describe lymphatic capillaries
- Drains for lymph
- Located in subepithelial loose connective tissue
- No pores
- No tight junctions
(not distinguishable under a standard light microscope preparation)
Describe lymphatic vessels
- Closely spaced valves
- Vessels drain into progressively larger vessels
- Some have elastic fibers and smooth muscle cells
(comparable to venules, but NO RBCs)
Describe the tunica intima of lymphatic duct
Endothelium and layers of collagen and elastic fibers and subendothelial space
Internal elastic lamina (where TI meets TM)
Describe the tunica media of lymphatic ducts
Longitudinal and circular smooth muscle
Describe the tunica adventitia of the lymphatic ducts
- Longitudinal smooth muscle and collagen fibers
- Continuous with surrounding connective tissue
