Histo- Heart & blood vessels
Terms
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- What are the three layers of vessels in general?
-
tunica intima= innermost layer
tunica media= middle layer
tunica adventitia= outermost layer -
Is the tunica intima closest to the lumen of the blood vessels?
What is the TI lined with? -
-yes
-endothelium - What type of cells is endothelium made of?
- simple squamous epithelial cells
- What is the tunica intima composed of?
- connective tissue and firbroblasts with some elastic and collagen fibers
- What forms the outer boundary of the tunica intima and is the boundary between the tunica intima and the tunica media?
- the internal elastic membrane
- Do the cells and fibers of the tunica intima run parallel or perpendicular in the vessel?
- parallel
- What is a function of the tunica intima?
- it provides a smooth surface to prevent blood clotting.
- What direction do the fibers and the cells of the tunica media run in relation to the long axis of the vessel?
- perpendicular in a circular manner around the vessel
- What type of cells and membranes are located in the tunica media?
- smooth muscle cells and elastic membranes
- Do the smooth muscle cells of the tunica media give rise to elastic tissue?
- yes
-
What is the vasa vasorum?
Give an example of a vasa vasorum -
-small arteries and veins that lie in the wall of large vessels and give nutrients to the muscle tissue: the vessel of the vessel
-coronary arteries are the vasa vasorum of the heart - How do small blood vessels recieve nutrition?
- diffusion
- Where can one find the vasa vasorum in a blood vessel?
- in the tunica adventitia and the outskirts of the tunica media
- What does the connective tissue of the tunica adventitia contain?
-
-collagen fibers
-fibroblasts
-the external elastic membrane (is part of the TA, not boundary)
-in larger vessels the vasa vasorum - Do tunica adventita fibers run parallel or perpendicular to the long axis of the blood vessel?
- parallel
- What are the three classifications of arteries?
-
1. elastic arteries
2. muscular arteries
3. small muscular arteries/arterioles - What are elastic arteries?
-
-the very large distributing arteries
-example=aorta and renal arteries - In elastic arteries is the tunica intima thick or thin?
-
-It is a thick subendothelial layer of CT
-some elastic fibers making the internal elastic membrane but hard to see - In the elastsic arteries, what types of cells does the tunica intima contain?
-
-some smooth muscle cells
-some elastic fibers making the internal elastec membrane - In the elastic arteries, is the tunica media thick or thin?
- thick
- In the elastic arteries, does the smooth muscle alternate with elastic membranes in the tunica media? Why?
-
-yes
-because the smooth muscle is producing the elastic membranes - In the elastic arteries, what does the structure of the elastic membranes look like?
- the elastic tissue is full of fenestrations
- What are the fenestrations in the elastic tissue of the tunica media of the elastic arteries?
- holes in the wall to allow the passage of material such as nutrients, ions and wastes
- In the elastic arteries, is the tunica media fed by a vasa vasorum?
- yes
- In the elastic arteries, what does the tunica adventitia contain?
- the vasa vasorum
- What are the muscular arteries known as?
- most named arteries of the body wall and organs
- In the muscular arteries,is the tunica intima thick or thin?
- thin subendothelial CT layer
- In the muscular arteries, is the tunica intima bordered by an internal elastic membrane?
- yes
- In the muscular arteries, what does the tunica media contain?
- 2-40 layers of circular smooth muscle
- In the muscular arteries, is there an external elastic membrane present in the tunica adventitia?
- only in larger arteries
- In the muscular arteries, is a vasa vasorum present?
- no, these vessels are small enough to suppply nutrients by diffusion
- What are the small muscular arteries/arterioles?
- the smallest of the arteries
- In the small muscular arteries/arterioles, what size is the tunic intima?
- less than .5mm in diameter
- In the small muscular arteries/arterioles, what does the tunica media contain?
- 102 layers of circular smooth muscle
- In the small muscular arteries/arterioles, does the tunica adventitia contain an external elastic membrane?
- no
- How many red blood cells can travel through a capillary at a time?
- only one- if you see 2-3 cells side by side it is not a capillary
- What are general characteristics of capillaries?
-
-composed of a single layer of endothelial cells that are simple squamous epthelium
-all cells rest on a basal lamina/basement membrane
-pericytes are scattered along the surface - What is a pericyte?
-
-a mesenchymal cell with long cytoplasmic processes that partly surround the endothelial cells of the capillary
- these cells are enclosed in their own basement membrane - What is the function of a pericyte?
-
-is contractile, contains actin, myosin, and tropomyosin,helps move the fluid in the lumen of the capillary on through it
-can repair after tissue injury, can form new blood vessels and CT - What are continous or somatic capillaries?
- endothelium is characterized by an absence of fenestrae in the wall, all cells rest on a continuous basement lamina/membrane
- How do continous/somatic capillaries transport stuff without fenestrations?
- pinocytosis
- Where are continous/somatic capillaries located?
-
-in muscle, CT, exocrine glands, and nervous tissue
**can not see this on a slide but must know from the type of tissue it is in
-found where rapid exchange is not needed - What are fenestrated/visceral capillaries?
- endothelium is characterized by large fenestrae in the wall that are either uncovered or covered by a thin diaphragm (not trilaminar), all cells rest on a basement membrane/lamina
- How do fenestrated/visceral capillaries transport stuff?
- across the fenestrae
- Where are fenestrated/visceral capillaries located?
-
-in organs where rapid transport between tissues and blood is needed
-kidneys, intestines, endocrine organs - What are sinusoids?
-
-a specialized capillary which has an enlarged diameter and has a tortuous course that slows the circulation of blood
-these are fat capillaries
-are wider & accomidate more than one blood cell
-do not have pericytes
-have endothelium and a basal lamina outside of endothelial cells - What are characteristics of fenestrated sunusoids?
- their cells have fenestrae, are in endocrine organs
- What are characteristics of discontinous sunusoids?
- there are gaps or spaces where two endothelial cells join, the basal lamina may be discontinuous, is in the liver and other organs
- What is the function of capillaries/sinusoids?
-
-exchange of materials across the wall of the capillary
-materials = gas(CO2 or O2) or nutrients - What type of capilliary is in skeletal muscle?
- continous, this is why muscles fatigue
- What are the comparitive speeds through the different types of capillaries?
-
slowest=continous
middle=discontinous
fastest=fenestrated - What do veins do?
- return blood to the heart
- Are the walls of veins more or less organized than arteries?
- less
- Do veins have organized smooth muscle in them?
- no
-
Are there more veins or arteries in the body?
Are the walls of veins thicker or thinner than arteries?
Is the circumfrence of a vein larger or smaller than an aretery? -
-more veins
-thinner
-larger - What are some general characteristics of veins?
-
-low blood pressure
-contain valves
-thickest layer in veins is the tunica adventitia - What is a venule?
-
-a thin wall vessel, the endothelium is similar in function to the capillary but the diameter begins to enlarge.
-is a very small caliber vein - What are small veins?
- most of the veins in the body with the exception of the main trunks
- Do venules contain a tunic adventita?
- yes
- What does the tunica intima of the small veins contain?
-
- a thin layer of CT covered by endothelium
-valves (folds of the intima)
**facial veins do not have valves - What does the tunica media of small veins contain?
- a few poorly organized layers of smooth muscles
- What does the tunica adventitia of small veins contain?
- has well developed, numerous collagen fibers w/ no smooth muscle
- What are some examples of large veins?
- vena cava and renal veins
- Is the tunica intima well developed in the large veins?
- yes
- What are characteristics of the tunica media of large veins?
- a few layers or circular arranged smooth muscle
- What are characteristics of the tunica adventitia of the large veins?
-
-thick layer, contains longitudinal clusters of smooth muscle parallel to the long axis of the blood vessel
-this gives structural support to the wall and helps move vascular contents
-there is collagen fibers in between the smooth muscle - What is the normal capillary blood flow?
-
arteriole
metarterioles(precapillary sphincters)
capillary
venules(postcapillary venule)
vein - What are arteriovenous anastamoses/shunts?
-
-places where blood bypasses capillary beds completely or reduces flow in a capillary bed for the purpose of thermoregualtion
-direct connections between the arterial and venous systems - What is the function of arteriovenous anastamoses/shunts?
-
-shuts down blood flow in cold and increases blood flow in fever
-function is to regulate blood pressure, blood flow and conservation of heat - Is the arteriovenous anastamoses/shunts in addition to the capillary beds?
- yes
- What are precapillary sphincters?
-
-sphincters that are at the end of metarterioles
-these regulate blood flow through the capillary bed - What are postcapillary venules?
-
-sometimes referred to as venous portion of the capillary bed
-functions similar to capillaries
-is modified in lymphatic organs for transport of the T-lymphocytes
-is surrounded by contractile pieces
-5-6 times of the capillary - Arteries compared to veins
-
lumen A=circular V=irregular
T.intima A=I. elastic memb V= valves
T. media A=thick V=thin
T.adventitia A=thin,no SM V=thick - Is the heart a modified blood vessel?
- yes
- What are the three layer of the heart?
-
epicardium-T. adventitia
myocardium-T. media
endocardium-T. intima - What is the epicardium analagous to?
- the visceral pericardium
-
Where is the epicardium on the heart?
What type of epithelium is the epicardium made of? -
-external layer of the heart
-simple squamous epithelium -
Where is the subepicardial CT?
What is its function? -
-the subepicardial CT is under the simple squamous epithelium of the epicardium
-it contains coronary vessels, nerves, and fat of the heart - What is the myocardium?
-
-the middle, largest layer of the heart
-contains cardiac muscle w/ intercalated disks and the sliding filament theory
-has a rich vascular supply - What is the endocardium composed of and where is it?
-
-simple squamous epithelium and subenodcardium
-is the internal layer of the heart, lines the chambers - What is subendocardial tissue?
-
-thin CT tissue
-contains the impulse conducting system of the heart (perkinje cells)
-does not contain large coronary vessels - What are perkinje cells?
-
-specialized modified cardiac muscle cells of the endocardium in the subendothelium
-this is the only kind of nervous/impulse to supply cardiac muscle (the heart does not get a direct nervous supply) - What is the cardiac conducting system composed of?
-
-sinoatrial node
-atrioventricular node
-bundle of His