Histology Flashcards
what is the structure of a capillary in CV system
single layer of simple squamous epithelium (endothelium) surrounded by basement membrane
What is the main distinguishing feature of a blood capillary vs lymphatics
uniform vessel diameter
8mm
What is the method of most the interchange at a capillary
simple diffusion
what controls rate of capillary transport
blood and colloid osmotic pressures
How are high MW molecules transported across capillaries
active transport via pinocytosis
How do WBCs and lymphocytes cross capillaries
diapedesis
how are the simple squamous cells forming capillaries held together
tight junctions
What are some glands with fenestrated capillaries
endocrine glands, renal gomerulus, intestinal villi pores
in fenestrated capillaries what are the pores closed by
diaphragm that is thinner than unit membrane
What are majority of the support cells for capillaries
pericytes, mesenchymal-like cells
In injury repair what can the support cells of capillaries do
transform to vascular smooth muscle and also can augment BM production
Where do you find discontinuous capillaries
sinusoids
How do sinusoids differ from tru capillaries
discontinuous endothelium, discontinuous BM, larger than capillaries- up to 30mm
What organs contain sinusoidal capillaries
liver, spleen, bone marrow
where are capillaries continuous
hypophysis and adrenal glands
what are the 3 layers of blood vessels
tunica intima, tunica media, tunica adventitia
What are the layers within tunica intima
endothelium, BM, subbendothelial CT, inner elastic lamina
What are they layers within tunica media
smooth mm and CT and external elastic lamina
What are the layers of tunica adventitia
dense CT and fibroblasts
What are the 3 general categories of arteries
arterioles, medium sized (muscular aa) and large (elastic) aa
What is the most prominent tunic in all aa
tunica media
what are other layers that are sometimes visible in arteries
inner and external elastic laminae
What is the diameter of an arteriole
0.05 - 0.5mm
What are the layers of an arteriole from thickest to thinnest
tunica media
tunica adventitia
tunica intima
how many layers of smooth m are in the arteriole tunica media
1-5
What is the function of tunica media in arterioles
control blood flow and regulates blood pressure
what is the diameter of a muscular/medium artery
0.5mm - 1cm
What is the most prominent part of tunica intima in a medium artery
the inner elastic lamina
how many layers of smooth muscle are in the tunica media of medium arteries
5-40 layers
Why is there so much smooth muscle in the muscular arteries
maintain pressure
what is the diameter of large elastic arteries
1 - 2.5 cm
describe tunica intima in elastic aa
polygonal endothelial cells with thick CT and small inner elastic lamina
describe tunica media in elastic aa
alot of elastic fibers
what is the purpose of the elastic fibers in elastic aa
retains shape during pressure. diminishes pulsatile delivery to peripheral vessels
over distention of tunica intima and media is prevented by what in elastic aa
the tunica adventitia
how are the collagen bundles oriented in the tunica adventitia of elastic aa
spiral longitudinally around vessel
What is vasa vasorum
small nutrient aa supplying walls of larger aa
what type of nerve fibers terminate on arterial smooth mm
ANS
What are the sensory receptors of the arterial system
Carotid body and sinus
What is the carotid body
mass of epithelioid cells and verve endings found at bifurcation of common carotid
what does the carotid body do
stimulates respiration in response to lowered blood O2
What is the carotid sinus
dilatation of internal carotid artery with specialized nerve endings
what does the carotid sinus do
sensitive to blood pressure change
what are the types of venules
post-capillary or pericytic
and muscular
What layer is most prominent in veins
tunica adventitia
what makes up the tunica media in veins
mainly collagen, little sm muscle or elastic fibers
What makes up tunica adventitia
smooth m and fibrous CT longitudinal and spirally oriented
What size veins have valves
medium sized
what are valves made of
invaginations tunica intima
the free edges of valves face in what direction
direction of blood flow
where are valves usually found in veins
lower limbs because low blood pressure
Describe the tunica intima of a venule
endothelium and BM
describe the tunica media of a venule
1-3 smooth mm layers
scattered elastic fibers
describe the tunica adventitia of a venule
thickest part of a venule wall, primarily longitudinal collagen bundles
describe tunica intima of a medium vein
endothelial cells are polygonal
small amount of subendothelial CT
longitudinal/spiral smooth m fibers
IEL is diffuse
describe tunica media of a medium vein
thin, smooth muscle is in spiral bundles, separated by collagen
describe tunica adventitia of a medium vein
collagen and elastic fibers predominate
Describe overall structure of a large vein like vena cava
thick tunica adventitia- longitudinal and smooth muscle. very thing media and thin intima
What are usually large in cross sections: aa or vv
veins
What is unique of cardiac skeletal m
beat rhythmically without external stimuli
how many nuclei are in cardiac m
binucleate and centrally located
how big are cardiac mm
50-100mm in length
15-20mm diameter
how are cardiac m cells joined together
fascia adherens- intercalated discs that are rich in gap junctions
what are the 3 layers of heart tissue
endocardium, myocardium and epicardium
what happens to damaged cardiac tissue
replaced by fibrous CT
What makes up the endocardium
endothelium and BM as well as subendothelial CT and sub endocardial CT
what is the role of subendocardial CT
bing endocardium to myocardium
Where are the purkinge fibers in the heart
in the subendocardial CT area
what are the purkinje fiber layer rich in
glycogen
Where is the SA node
junction of sup vena cava and right atrium
what inn stimulates myocardial activity and what inhibits it?
stimulated by sympathetic and inhibited by vagal parasympathetic
What separates cardiac muscle bundles
CT networks made of collagen elastic fibers and reticular fibers
What runs throughout the CT network of cardiac m bundles
capillaries and nerves
What is another name for visceral part of pericardial sac
the epicardium
what lines the epicardium
mesothelium
what makes up the epicardium
think layer CT which carries aa and vv
what does the loose CT of the epicardium connect
serous mesothelium to myocardium
how do you distinguish endocardium from epicardium
epicardium has fat to protect vessels
How does the epicardium appear compared to myocardium in a general stain
epicardium white because adipose and myocardium has big red spots
Where are the fibrous rings found in heart
valves
what makes up the fibrous rings in heart
dense fibrous CT, collagen and elastic fibers
What are fibrous trigones
thickened areas of dense fibrous CT between R and L AV canals and aortic valve
What forms the membranous part of AV septum
fibrous trigone
what are the heart valves tissue wise
evaginations of endocardium into AV canals
What tissue is in the core of heart valves
subendothelium and eubendocardium
At what pressure difference do electrolytes pass from blood to extracellular space
when hydrostatic pressure of blood exceeds osmotic pressure of interstitium- Arterial side of capillary
describe the pressure at the venous terminus of capillary
osmotic pressure of interstitial exceeds hydrostatic pressure of blood
what is greater. exchange at arterial side of capillary or resorption at venous side?
exchange so excess is lymph
What type of vessel do lymphatics resemble
veins because tunica media is mainly CT
describe lymph capillary
continuous endothelium with thin wall, irregular lumen, many many valves and incomplete basal lamina, no junctional elements
how to lymph capillaries originate
blind-ending vessels
what is the difference of lymph valves when compared to venous valves
the core is exclusively collagen III
what are the differences between large lymphatics and large veins
thinner walls, tunics less distinguishable and there are many valves and sinuses
what are the differences with the thoracic duct and right lymphatic duct with great veins
thinner walls, more prominent muscle layers and the tunica adventitia is not well developed
