S1M3 Circulatory System Histology
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The Blood vascular system consists of what 2 parts?
- 1.) Heart: the muscle to pump into the two systems
- 2.) Two Systems: a Pulmonary Circuit (carrying blood to/from lungs) and a Systemic Circuit (delivering blood to and from all the organs!)
The right side of the heart pumps blood through what circuit?
The pulmonary circuit to the lungs and back to the left side of the heart.
The left side of the heart
pumps blood into what circuit? Easy question comon!
Left side of heart pumps into the systemic circuit to all the body tissues and then deoxy blood comes back to the right side of the heart.
Blood flowing through the pulmonary circuit gains what and loses what?
What are the three layers of your blood vessels from inside--> out?
- 1.) tunica intima (it's intimate with the blood)
- 2.) tunica media
- 3.) tunica adventitia
Features of the tunica intima?
- Single layer of endothelial cells
- In contact with the blood
- Made of LCT & scattered Smooth Muscle.
Features of tunica media?
Concentric layers of smooth muscle cells
***smooth muscle has interspered elastic fibers, type III collagen and proteoglycans
What tis the tunica media important in?
Regulation of blood pressure because of the smooth muscle cells that are present in the tunica media.
tunica adventitia is composed of what?
it is the outer-most layer of the BV and is made of just CT.
**composed of fibroblasts, type I collagen, and longitudinal elastic fibers
What is unique about the demarkation of the tunica adventitia?
Can tell where it begins (against the tunica media) but not where it ends because it becomes continuous with the surrounding vessels and CT.
The tunica adventitia
of large arteries and veins contain what and WHY?
a system of vessels called the vasa vasorum that supply blood to the vascular walls themselves because the tunica adventitia is too thick!
What are your largest arteries referred to as?
Elastic arteries or conducting arteries (ie., aorta) which are the biggest arteries closest to the aorta and its branches)
Why do your elastic arteries or coducting arteries have to be elastic?
They're so close to the heart and they have to handle the HIGH BP coming from the heart.
What are 3 types of arteries?
- 1.) Elastic Arteries (largest)
- 2.)Muscular Arteries (next largest)
- 3.)Arterioles (and metarterioles) smallest arteries
What are your arterioles and why are they important?
Smallest arteries that regulate blood flow into capillary beds.
Easy Question You should know by now:
Systole is what?
When the heart contracts duh.
Easy Question You should know by now: Diastole is what?
when the heart relaxes
The recoil of a distended elastic artery is called what?
What is a dissecting aorta?
when you aorta can't take the pressure from expansion and as a results rips through the inner t. intima layer and can even rip the t. media. You get a seperation of the layers, and blood flowing through the other layers.
- Rips all the way? Du bist schnell tot. Rips partially? Blood ends up in the t. media which needs to be fixed.
What is characteristic of the larger muscular arteries?
- They have less elastic fibers in the middle of the t.mediaAlso have Inner/external elastic lamina that seperates external media from adventitia
True or False? The largest muscular artery will have both an Internal/External elastic lamina?
TRUE: the largest muscular arteries have both layers--
As the artery gets smaller you lose the external elastic lamina first and the internal elastic lamina last.
How do you recognize a muscular artery?
- The INTERNAL ELASTIC LAMINA!Seperates the tunica intima from the tunica media.
Capillaries don't have any _______?
If it has muscle around the vessel it is called a metarteriole not a capillary.
An arteriole has what in its tunica media?
2-3 layers of SMOOTH MUSCLE cells.
(medium caliber) artery
has what in its tunica media?
up to 40 LAYERS of SMOOTH MUSCLE
Veins have a smaller _______ than arteries of the same size?
- *instead veins can have more smooth muscle in the adventitia, to help blood move along
Veins have _______ present in the tunica adventitia that is a major feature to distinguish them from arteries.
Smooth muscle bundles are present in the tunica adventitia which contract and cause parastaltic motion that moves the blood along
What have more vasa vasorum, large arteries or large veins?
- large VEINS!
- because veins carry deoxy blood, to compensate, the larger veins typically contain more vasa vasorum to provide metabolites to the thick t. adventitia
How do you differentiate between an artery and vein?
LOOK at the size of the WALL
- Veins have thinner walls than arteries
- Lumen of vein is much larger relative to the size of the tunics
Veins have _____ arteries do not.
- Valves!Used to regulate blood flow, prevent backflow of blood
The valves of veins
are made from what layer
? and composed of what fibers
- tunica intima jutting out into the lumen
- Reinforced with collagen and elastic fibers
- Purpose: PREVENT BACKFLOW :(
What are varicose veins
- If the one-way valves in your veins fail to close, blood will pool in the vein
- Over time, the pooling will force the vein walls outward resulting in enlargement and ugly bulging of the vein, making to look rope-like.
MORE COMMON IN WOMEN--less developed skeletal muscle, being overweight can also contribute to this as well.
Capillaries serve what purpose?
- Junction between arteries and veins
- Major place for exchange of gases and nutrients btw. bloodstream and extravesicular tissue
- ***THIS is WHY we need a circulatory system.
- The heart is just a pump, A/Vs are just transporters, the capillaries are where the action is
Capillary blood flow can be controlled with precapillary sphincters, but what is the name of the channels that always alows blood to flow from the artery to the vein?
- Called Thoroughfare channels
What are the three types of capillaries
- Continuous (least leaky)
- Discontinuous (most leaky)
Each capillary is composed of a _______layer of endothelium attached to a basal lamina
What are pericytes
- Associated closely with capillaries and post-capillary venules, they have contractile function (contain actin & myosin, tropomyosin
- WHY? because remember capillaries lack a tunica media and muscle and pericytes take the place of the muscle in the tunica media.
- Allows blood to continuously flow though capillaries
_________ capillaries contain lots of pinocytotic vesicles responsible for transport of large macromolecules in both directions across the endocytotic cytoplasm
Continuous (or somatic) capillaries
Why does skeletal muscle have lots of capillaries?
Capillaries provide the oxygen & nutrients to the muscles in order to contract!
Where do you find a lot of fenestrated capillaries?
- Tissues where rapid interchange of substances occus between the tissues and the blood
- KidneyIntestine (for nutrients)
- Endocrine glands (for secretions)
Fenestrated capillaries are different from continuous capillaries how?
- Have PORES or "windows" bridged by an ultrathin diaphragm! (allows movement of substances across capillaries)
WHAT IS THIS?
A fenestrated capillary of the glomerulus of the kidney.
NAME the STRUCTURE the ARROWs pointing to
Each arrow is a Fenestration with a diaphragm, picture is then of a fenestrated capillary.
What are the leakiest capillaries?
- Sinusoidal (discontinuous) capillaries
- Have HUGE gaps btw endothelial cells
- Incomplete basal lamina
What organs do you find Sinusoidal (discontinuous) capillaries?
- Hematopoietic organs (megakaryocytes send their projections through these holes)
- Bone Marrow
- ***Whole CELLS will pass through these large holes
Cavelolae are very numerous in endothelial cells, they function to ______ ?
Shuttle material across the endothelial wall!!
Adluminal refers to what?
The side of a vessel facing the lumen
Abluminal refers to what?
- The side of a vessel directed away from the lumen
- b for beyond!!!!
Blood brain barrier (BBB) has what?
A special type of capillary which lets essential metabolites (O2, glucose) pass from blood to brain and CNS but blocks molecules bigger than 500 daltons.
The BBB has extensive _____________ that resemble the ___________ of epithelial cells
Tight tight tight tight tight junctions.
What is one part of the brain NOT "behind" the BBB?
the PINEAL GLAND which secretes hormone melatonin directly into the systemic circulation.
Must Know: What are the four types of microcirculation?
- 1.) Normal: Arteriole --> metarteriole-->capillary-->venule and vein
- 2.) Arteriovenous anastomosis (direct communic. btw arterioles and venules, no capillaries --> ie, penis clitoris
- 3.)Arterial portal system: arteriole-->capillary-->arteriole (ie., kidney glomerulus)
- 4.)Venous portal system: present in liver (venule-->capillary-->venule
Sequence of an arterial portal system?
ie KIDNEY glomerulus
Example of an arteriovenous anastomosis?
Penis & Clitoris (normally closed off with a sphincter!
Sequence of a venous portal system?
What are the three layers of the heart? Which is the thickest?
- Endocardium: continuous with tunica intima of blood vessels entering heart
- Myocardium (middle and thickest layer)
- Epicardium: the outer most layer of the heart, called the visceral layer of the pericardium
Be familar with the three layers of your heart (endocardium, myocardium and epicardium
What type of tissue is this?
- Cardiac muscle tissue, dark red is myocardium
- Endocardium is above it and is stained purple
- Pale fibers are the PURKINJE FIBERS in the endocardium
What are these structures with the nuclei and light area around them?
- These are purkinje cells
- The light area around the nuclei of the conducting cells is caused by local accumulation of glycogen
______________ is the chronic disease characterized by abnormal thickening and hardening of the arterial walls with resulting loss of elasticity.
______________ is an arteriosclerosis characterized by the deposition of fatty substances in and fibrosis of the inner layer of the arteries.
Athrosclerosis involves changes to what layer of the arteries?
the tunica intima
What is an Atheroma? What is a characteristic of?
- lipid deposits in the tunica intima of arteries, porducing a yellow swelling on the endothelial surface.
- Characteristic of artherosclerosis!
What triggers atheroclerosis?
- any damage to the cells lining the arteries
- a result of high BP
- Toxic Substances
Atheroclerotic plaques develop how?
- 1.) Monocyte migrate through endothelial wall and into the intima, where they differentiate into macrophages
- 2.)Macrophages take up excess LDL (lipid) forming FOAM cells. These foam cells release GF (growth factors, cytokines that act on smooth muscle, so smooth muscle cells migrate secrete collagen and fibrous tissue to heal damage and form a fibrous cap.
What are FOAM cells?
When macrophages that have migrated to a atherosclerotic plaque forming area, and take up lots of LDL (lipid) and take on a different "Foamy" appearance
What is a fibrous cap?
It is a bunch of lipid (fat) that has forms UNDER the endothelial cells, that will become calcified, brittle and could crack and expose collagen, jumpstarting the clotting cascade that can cause a heart attack.
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