Histology Flashcards
Endocardium
Internal lining of the heart chambers
Consist of three types of cells
- endothelium (closest to the chambers)
- fibroelastic CT
- subendocardium (closest to the surface of the heart)
Myocardium
Middle layer of tissues comprised primarily of contractile cardiac myocytes
- actually does the contracting of the heart
Epicardium
External layer of the heart and consists of two layers
- subpericardium: areolar and adipose CT supporting the coronary arteries/veins/nerves/lymph vessels to the heart.
- visceral pericardium: mesothelium layer that produces a lubricating serous fluid contained within the pericardial cavity.
Heart murmur
Regurgitation of blood through a prolapsed valve
Stenosis
Narrowing of a valve through scar tissue of plaque buildup
Ischemia
Reduction and/or loss of oxygenated blood flow to the tissues due to obstruction of hemorrhages of coronary arteries
Angina
Visceral cardiac pain caused from a myocardial ischemia
MI (heart attack)
Damage/necrosis of myocardial tissue caused by ischemia
Tunica intima
Internal lining of the lumen of the vessel
Consist of endothelium and sub endothelium
Tunica media
Middle layer of tissues composed primarily of concentric layers of smooth muscle fibers arranged helically.
Consist of smooth muscle, elastic fibers
Tunica externa
External layer of the vessels composed of loose CT
Contain type 1 collagen and elastic fibers
Also contain autonomic nerve fibers (mainly sympathetics)
Vasa vasorum
Blood vessel supply of blood to keep the healthy
Primarily only present in larger and medium vessels
Functional roles of endothelium
Monitors and mediated the bidirectional exchange of molecules between blood and tissues
Controls local clot formation
Regulates local vascular tone and blood flow
Facilities local inflammation and immune responses
Promotes proliferation of cells within a vascular wall and white blood cells.
Blood pressure
Cardiac output x stroke volume + total peripheral resistance
Systemic hypertension
High blood pressure Through the systemic circuit. Can be secondary or primary.
Secondary = chronic hypertension via renal or endocrine dysfunctions
Primary = essential or idiopathic chronic hypertension do to environmental/lifestyle factors
Aortic dissection
A tear in the tunica intima layer of the aorta that overtime causes complete dissection the aorta if not treated,
Cardiac Skelton
Prominent areas of fibrous dense irregular CT found in the endocardium and myocardium
used as landmarks to separate atria from ventricle, form AV valves and the interventricular/ intratrial septa
Functions:
- electrical insulation between atria and ventricles (coordinate heartbeat)
- attachment points for cardiac muscle
- anchors and supports heart valves
What valves are chorda tendonae found in?
AV valves (bicuspid/tricuspid)
Differences in contractile apparatus in cardiac myocytes vs skeletal muscle myocytes
Cardiac has
- more mitochondria
- less Sarcoplasmic reticulum
- presence of fat
Atrial natriuretic peptide/factor
Polypeptide hormones found primarily in the right atrium that decrease blood pressure via initiating vasodilation and antagonize the renin-angiotensin system
SA node vs AV node
SA node
- found in the right atria near the SVC
- sets atria pace and is the prime initiator of the contraction
AV node
- found on the floor of the right atria near the septum
- sets the ventricular pace and sends the conduction through the AV bundles
Why cant cardiac cells regenerate?
They do not possess satellite cells like skeletal muscles do
Layers of blood vessels from deep to superficial
Tunica intima
- endothelium
- subendothelium
Tunica media
Tunica externa (adventitia)
Difference in layer of arteries vs veins
Arteries
- no valves
- tunica media is thickest layer of vessel
- small tunica externa
Veins
- valves
- tunica externa (adventitia) is thickest layer of vessel
Continuous capillaries
Most common type of capillary bed
Most restrictive with exchange, causes molecules to have to diffuse through transportation
Present in muscles, CT, lungs, exocrine glands, nervous tissue
Overlapping endothelium cells prevent paracellular transport
Very defined basement membrane
Fenestrated capillaries
Found in kidneys, intestines, choroid plexus and exocrine glands
Endothelial cells still overlap, however they have numerous small openings with a thin diaphragm which allow easier diffusion
Possess a uniform basement membrane
Discontinuous capillaries
Rarest kind of capillaries found in liver, spleen, bone marrow
Endothelial cells have large holes without diaphragms which causes discontinuous endothelium layers
Discontinuous basement membrane
Largest diameter capillaries
Molecules that directly control vasoconstriction
Endothelium 1-3
Thromboxane A2
Prostaglandin
Molecules that directly control vasodialation
Nitrous oxide
Prostacyclin
EDHF
