20110112 04 circulatory notes.txt

From Iusmhistology

• started here on 01/12/11

Contents 1 Circulatory 1.1 Objectives 1.2 Components 1.3 Functions 1.4 Histology of vessels 1.5 Capillaries 1.5.1 Structures 1.5.2 Image examples 1.5.3 Facts 1.6 Topics 1.6.1 Heart 1.6.1.1 Observation 1.7 Lymphatics 1.7.1 Observations 2 Lab 6: Cardiovascular tissue 2.1 SMALL VESSELS 2.1.1 Slide 10: Mesentery, human 2.1.2 Slide 25: Lymph node, monkey 2.1.3 Slide 15: peripheral nerve 2.2 MUSCULAR (MEDIUM) ARTERIES AND MEDIUM VEINS 2.2.1 Slide 16: Aorta and mesenteric artery, human 2.2.2 Slide 25: Lymph node, monkey 2.2.3 Slide 10: Mesentery, human 2.3 ELASTIC (LARGE) ARTERIES 2.3.1 Slide 16: Aorta 2.3.2 Slide 37: Aorta 2.4 LARGE VEINS 2.4.1 Slide 38: Vena cava 2.5 THE HEART 2.5.1 Atrium 2.5.2 Ventricle 2.5.2.1 Slide 19: Heart, ventricle and auricle 2.5.2.2 Slide 20: Heart ventricle moneky

[edit] Circulatory

• First time we'll see tissues put together into tissues and organs.

[edit] Objectives

• At the conclusion ofthe unit on the circulatory system, each student should be able to:
  • Sketch from memory the histologic structure of all ofthe vessels. Label the tunicae.
  • Distinguish the relative functions of the parts ofthe vascular system, and correlate these with their structures.
  • Describe the physical relationship ofpericytes to endothelial cells.
  • List the four types of capillary and describe their similarities and differences. How do these differences relate to function?
  • Describe the function of precapillary sphincters and arteriovenous anastomoses.
  • List the metabolic functions ofendothelial cells, as described in the text.
  • List the layers ofthe heart and distinguish between atrium and ventricle in the structures ofthese layers.
  • Describe the specialized cells ofthe heart.
  • Compare and contrast lymphatic vessels with blood vessels with regard to structure and function.

[edit] Components

• Heart
  • Pumps to two systmes at once
  • Has variable output and speed
    • Yes, output, asin the volume
• Artieries
  • Low capacity: hold little of the total blood
  • Carry at high hydrostatic pressure
• Capillaries
  • Low hydrostatic pressure
  • High cross-sectional area
  • Low flow velocity
  • Good chance for diffusion with fluid around caps
• Veins
  • Very Low hydrostatic pressure
  • High and variable capacity
    • Can hold 75% or can contract to hold less volume (if dehydrated) or expand (if well hydrated).

[edit] Functions

• Draw a heart, divide with two lines to make four sections.
  • Atria and ventricles
• Blood goes out left ventrical to systemic capillaries (everything but the lungs)
• Blood comes back into venules and veins and right atrium.
• Then to right ventricle and to the pulomonary system (the lungs)
  • We won't talk about pulmonary vessels this lecture.
  • Theya re different because their pressure is different.
• Back into left atria and ventricle

[edit] Histology of vessels

• The vessels have layers, called tunics.
  • Tunics were garmets, tight-fitting shirts.
• Layer closest to the blood is tunica intima.
• Outside most layer is called tunica adventitia or tunica externa.
  • The layer that comes to the outside of the vessel.
• In between is the tuica intermedia
  • Contains muscle
• Vessels can have vessels in them: vasa vesorum (vessels of the vessels)
  • This is to supply the outer cells of the bigger vessels.
• When we see smooth muscle in the vessels, there is probably innervation
  • We usually won't see the nerves, though, because they are so small.

[edit] Capillaries

• Capillaries are about 10 microns, so blood cells just barely fit thorugh.
  • In smaller capillaries, RBCs even have to change their shape and squeeze through.
• Not all capillaries are the same
  • Different degree of permeability depending on where they are in the body.
  • Thinner, more holes = more permeability
• Recall that a cell membrane is about 10 nm with proteins in it.
• Recall that we can see about 1 micron things as points via LM.
• Capilarries are usually 7-10 microns in diameter.
• They only have the tunica intima.
• Sometimes have pericytes with them
  • Can replace other cells
  • Can form new blood vessels
  • Can undergo division
• Caps are simple squamous epithelium
• Continuous capilarries:
  • Have a relatively thick (though very thin) extension of cytoplasm
  • Found in muscle, nerve, connective tissue, and exocrine glands
    • Like salivary glands seen on monday.
• Fenestrated capilarries
  • Have windows = fenetre in french
  • Found in kidney, GI, and endocrine glands (pit, thryroid)
  • More leaky than continuous
• Fenestrated capilarries without diaphragm
  • Have windows
  • The windows do not have diaphragms that are like a piece of glass in the window
  • Found in the renal glomerulus
  • More leaky than fenestrated with
• Sinusoidal capilarries
  • Bone marrow, liver, lymphod tissue
  • Where lots of proteins move in and out of blood
  • usually cells can move in and out pretty easily as well.

[edit] Structures

• Continuous
  • Tight jxns with endothelial cells
  • Have lots of penocytoic vesicles
    • Looks like material is brought into cell from outside
  • Not fenestri
  • No diaphram
  • BM is always present in continuous caps
  • Tightest of caps
• Fenestrated with diaphragm
  • A little leakier
  • Have tight jxns with endothelial cells
  • Have some pinocytotic vesicles
  • Have fenestri, diaphragm, and bm.
• Fenestrated without diaphragm
  • Tight jxns
  • Pinocytoics
  • Fenestri
  • BM
• Sinusoidal
  • Some tight jxns, but some of the endothelial cells don't form tight jxns with their neighbor.
  • No pinocytoic vesicles
  • Have fenestri, without diaphragm
  • Discontinuous BM
  • Leakiest.

[edit] Image examples

• Epithelial cells can wrap all the way around a vessel.
• Fenestrations:
  • They are arranged in little collections.
• Pinocytotic vessles are much like the fenestra.
  • Also called caveoli
  • Can fuse to cause little diaphrams
• Diaphragm of fenestra
  • Has spokes
  • Made of PB1 and other proteins
  • PB1 forms fibrilar spokes across the fenestra.

[edit] Facts

• Entrance to the capillary bed is controlled by the pre-capilarry sphincter.
  • controls whether and how much blood flows into the capillary bed.
• Capillaries function to keep cells and protine in the blood.
  • BBB exists to
  • BBB is made up by continuous capillaries and the cellular barriers on the outside.

*Read 188-189 on function of endothelial cells
**A quesiton will coem from this for exam.

xXVlVc Good post! Found a lot of new and interesting! Will share the link with others:D

[edit] Topics

• Arteriole-venus anastamosis
  • Used them when we played in the snow.
  • Blood flow to skin shuts down.
  • This is achieved by connecting artery and vein so the capillary bed is bypassed.
  • This maintains normal blood flow in arteries and veins.

[edit] Heart

• has three tunics: endocardium, myocardium, epicardium
  • differ in the atrium and ventricle.
• Endocardium:
  • Atrium: Endothelium and connective tissue
  • Ventricle: Only endothelium
• Myocardium:
  • Atrium: Cardiac muscle
  • Ventricle: Thick layer of cardiac muscle
• Epicardium:
  • Atrium: Connective tissue and mesothelium
  • Ventricle: Connective tissue and lots of larger vessels (coronary arteries), and mesothelium.
• Specialized cells:
  • Nodal cells
    • Set pace of heart
  • Perkinje cells
    • Modified cardiac muscle cells
    • Carry signal from one part of the heart to another.

[edit] Observation

• Endocardium layer of atrium is thicker than the epicardium.
  • Makes sense because the atrium may get stretched an endocardium will sustain the structure.
• Epicardium:
  • Mesothelium on the outside is often simple squamous epithelium.
• Perkinje cells:
  • Looke very diff
  • Multiple nuclei and some myofibers
  • But not packed full of contractile apparatus

[edit] Lymphatics

• Lymphatics drain ECF.
  • Blood vessels leak
  • Lymph vessels recover the fluid that has escaped the blood circulation
  • Also impt for lymphatic cells
• Lymphatic capillaries:
  • blind ended capillaries
  • exist out in tissue
  • Have incomplete fenestri
  • have very few tight junctions
  • have very little bm
  • They are super leaky
• The cells of the lymph capillaries are anchored to the connective tissue around them by collagen fibrils.
  • So when pressed, they are squished but open up upon freedom from pressure and as connective tissue spreads.
  • This pulls fluid into it.
• Caps form larger vessels
  • These have thinner walls than veins of similar size.

[edit] Observations

• Lymphatics sometimes have valves that keep lymph flowing in one direction.
• The walls may not be apparent; they can look like open space with endothelium lining it.

[edit] Lab 6: Cardiovascular tissue

• There are three layers to cardiac tissue:
  • Tunica intima
  • Tunica media
  • Tunica adventitia
• In some parts of the cardiovascular tissues, one of these three tissues dominates over the others:
  • The tunica media is dominant in all arteries (small to large).
  • The tunica adventitia is dominant in most if not all veins.
• See Basic Histology 11-7.

[edit] SMALL VESSELS

• Arterioles and venules are the smallest of the arteries and veins, respectively.
• They are often seen as paired structures in connective tissue.
• Note that the arterioles will have a thick wall composed mostly of tunica media; venules will have a much thinner wall.
• Capillaries are very difficult to see in light microscopy because they are a single endothelial cell thick.
• Note that we use H&E as well as orcein to stain vessels.
  • Orcein generates brown stains.

[edit] Slide 10: Mesentery, human

• This is an orcein and H&E stain.
• The arterioles and venules are easily seen to be paired.
• Arteriole observations:
  • A thin tunica intima exists as a deep, purple, smooth band.
  • A thick tunica media clearly distinguishes between arteriole and venule.
  • The tunica adventitia is about half as thick as the tunica media and stains as a jagged band of cells.
• Venules
  • The tunica intima stains a deep purple as in the arteriole but is not as smooth; each cell seems to jut out into the lumen.
  • The tunica media is thinner than in the artiole with a more speckled pattern--less homogenous.
  • The tunica abventitia of the venule gives a similar jagged stain but is slightly lighter.
    • The two tunica adventitia are often adjacent.

[edit] Slide 25: Lymph node, monkey

• This is an orcein and H&E stain.
• Similar to slide 10.
• In this section, the venules tunica intima does not show the same jagged pattern as seen in the mesentery.
• Another difference is that in this section the arteriole's tunica adventitia has a definite wavy pattern as opposed to a jagged homogeneity.

[edit] Slide 15: peripheral nerve

• This is an H&E stain.
• Wavy pattern of arteriole tunica adventitia seen again.

[edit] MUSCULAR (MEDIUM) ARTERIES AND MEDIUM VEINS

• Medium arteries are also called muscular arteries because of the prominent smooth muscle found in the tunic media.
  • However, in muscular arteries, the tunica adventitia is often thicker than the tunic media.
• Muscular arteries also have eleastic fibers running through them.
  • These fold over themselves as contraction occurs.
• Some medium arteries show a prominent external elastic lamina in the tunica media.
• Elastic fibers can also be found running in the tunica adventitia.

[edit] Slide 16: Aorta and mesenteric artery, human

• This is an orcein and H&E stain.
• The elstic fibers of the tunica media are seen as blue-purple, folded, ghostly, fibers.
• A fairly continuous external elastic lamina can be seen in the transition between tunica media and tunica adventitia.
• Elastic fibers are visible in the tunica adventitia as pink connective tissue.

[edit] Slide 25: Lymph node, monkey

• This is an H&E stain.
• Elastic fibers of the tunica media are readily seen.

[edit] Slide 10: Mesentery, human

[edit] ELASTIC (LARGE) ARTERIES

• Note that this section is specific to arteries.
• We have seen elastic fibers as blue-purple in orcein + H&E; they will appear as read or brown with just orcein.
• In large vessels, vasa vasorum should be visible in the tunica adventitia

[edit] Slide 16: Aorta

• This is an orcein stain so elastic fibers will be red / brown.
• There is a definite border between the tunica media and the tunica adventitia.
• Though there is a distinction between the tunica media and the tunic intima, there isn't really a solid border.

[edit] Slide 37: Aorta

• This is an H&E stain so elastic fibers will be blue-purple.
• Again there is a definite border between tunica media and tunica adventitia but not between the tunica media and tunica intima.

• stopped here

[edit] LARGE VEINS

• Large veins like the vena cava have longitudinal bundles of muscle cells in the adventitia.
• Large veins also have thin tunica media.

[edit] Slide 38: Vena cava

• This is an H&E stain.
• Note that because the vena cava is a large vein, the media is thin and there are smooth muscle cells in the adventitia.
• The vasa vesorum are readily apparent, also.

[edit] THE HEART

[edit] Atrium

• The ventricle is easily identified as the tissue with epicardium (which has a high fat content) at the border.
• Note that coronary arteries are also visible, supplying oxygenated blood to the cardiac tissue.

[edit] Ventricle

[edit] Slide 19: Heart, ventricle and auricle

• Note that the epi, myo, and endo cardium of the atrium and the ventricle are visible.
  • The epicardium of the atrium is especially thick.

[edit] Slide 20: Heart ventricle moneky

• In the ventricle, Perkinje fibers are visible but difficult to find.
  • These fibers conduct the electricity of the heart.

• stopped here on 01/12/11.