Histology- Circulatory System

Front 1

Important function of lymphatic system:

Back 1

Return fluid of the tissue spaces to the blood.

Front 2

Macrovasculature:

Back 2

More then 0.1 mm in diameter:
Large arterioles
Muscular and elastic arteries
Muscular veins

Front 3

Microvasculature:

Back 3

Arterioles
Capillaries
Post capillary venules

(Only visible with microscope)

Front 4

Subendocardial layer:

Back 4

Layer of connective tissue between endocardium and myocardium, contain vessels, nerves and branches of the conductive system

Front 5

Where is pericardial fluid (20ml) located:

Back 5

Between the visceral (epicard) and parietal layer of serous pericardium

Front 6

Structure of heart valves:

Back 6

Central core of dense fibrous connective tissue (containing both collagen and elastic fibers), lined on both sides by endothelial layer. The base of valves are attached to cardiac skeleton

Front 7

Cells of SA node:

Back 7

Small mass of modified cardiac muscle cells that are fusiform, smaller and with fewer myofibrils then normal cardiac muscle cells. AV node cells are similar but with more cell projections

Front 8

Purkinje fiber cells:

Back 8

One or two central nuclei and cytoplasm rich in glycogen and mitochondria. Penetrate heart wall from endocard layer to epicard.

Front 9

Are chordae tendinae part of fibrous cardiac skeleton?

Back 9

Yes, and it attaches to papillary muscles avoiding valves turning inside- out during ventricular contraction. Are covered by endothelium.

Front 10

Basic stricture of large blood vessels:

Back 10

1. Endothelium
2. Smooth muscle
3. Connective tissue with elastic elements in addition to collagen

Front 11

Endothelium:

Back 11

Semipermeable membrane of simple squamous epithelium between blood plasma and interstitial fluid.
Produce NO, endothelins and vasoconstrictive agents. Convert angiotensin I to II (lungs).

Front 12

What is special about endothelial cells of arteries:

Back 12

They contain very small elongated vesicles (Weibel- Palade bodies) containing selectin and von Willebrand factor.

Front 13

Purkinje fibers:

Back 13

Larger cells then contractile cells. Joined by intercalated disks and many gap junction---> impulse conduction rather then contraction. Lots of Glycogen in cytoplasm (stained)

Front 14

Epicardium:

Back 14

Loose connective tissue containing autonomic nerves and adipose tissue. Covered bye simple squamous- cuboidal epithelium. Coronary vessels are located here. Secrete pericardial fluid

Front 15

Are concentration of GAGs higher in arterial then venous tissue?

Back 15

Yes

Front 16

Tunica intima:

Back 16

Endothelial layer on a subendothelal connective tissue layer, with som smooth mm. cells. (In arteries separated from media by internal elastic lamina, fenestrated elastin allowing diffusion and nourishing of deep vessel wall).

Front 17

Tunica media:

Back 17

Concentric layers of helically arranged smooth muscle cells. Among smooth mm. cells are elastic fibers, reticular fibers of collagen type III, proteoglycans and glycoproteins (produced by these cells)
Arteries has a external elastic lamina that separates media from tunica adventitia.

Front 18

Tunica adventitia:

Back 18

Type I collagen and elastic fibers. The adventitial layer is continuos with the stromal connective tissue of the organ which the vessel run through,

Front 19

Vasa vasorum:

Back 19

Vessels within the vessel of large vessels. Consists of arterioles, venules and capillaries. Supply media and adventitia, because the vessel wall is to thick for diffusion from lumen to outer layers.

Front 20

Why do large veins usually have more vasa vasorum then arteries?

Back 20

Because they carry deoxygenated blood.

Front 21

Important function of elasticity of large arteries:

Back 21

During systole elastic laminae of large arteries stretch and absorb the pressure avoiding a drastic increase in BP. During diastole elastic laminae rebound which increase the pressure and pushes blood forward maintaining a constant BP and blood flow.

Front 22

Muscular arteries:

Back 22

Can control blood flow to organs by contracting/ relaxing smooth muscles. Tunica media contains up to 40 layers of smooth mm. cells.

Front 23

General statement about muscular arteries:

Back 23

Arteries large enough to have names are of this type (mostly). With greater distance from the heart arteries generally have more smooth muscle and less elastic fibers

Front 24

Carotid sinuses:

Back 24

Small dilatations of the internal carotid artery containing baroreceptors detecting increase in BP. Have thin media to absorb changes in pressure, and intima and adventitia with many nerve endings from IX cranial nerve, the glossopharyngeal nerve.

Front 25

Carotid bodies:

Back 25

Small ganglia like structure near the bifurcation of the common carotid arteries containing chemoreceptors sensitive to blood CO2 and O2 concentrations. Aortic bodies in the arch of the aorta are similar.

Front 26

Arterioles:

Back 26

Less then 0.5 mm in diameter and only two layers of smooth mm. in media. Elastic lamenae are absent and adventitia is very thin. Circular smooth mm. in media.

Front 27

Capillaries:

Back 27

Single layer of endothelial cells rolled up in a tube. 5- 10 micrometers in diameter and about 50 micrometers in length.

Front 28

Capillaries VS. rest of blood vessels:

Back 28

Capillaries= 90% if all blood vessels in the body (about 96 000 km). Total diameter of capillaries = 800 times larger the the aorta.

Front 29

Speed of blood flow in aorta VS. capillaries:

Back 29

Aorta: 320 mm/s
Capillaries: 0.3 mm/s

Front 30

Permeability of capillaries:

Back 30

Water and some other hydrophilic molecules less then 1.5 mm in diameter and below 10 kDa can cross capillary wall by diffusion through intercellular junctions. Other passage ways are: pores in fenestrated capillaries, the spaces between endothelial cells of sinusoidal capillaries, and pinocytotic vesicles.

Front 31

Glomus cells:

Back 31

Cells filled with vesicles with neurotransmitters (dopamine, serotonin, adrenline) located near large sinusoidal capillaries in carotid bodies. Glomus cells form synaptic connections with dendritic fibers of glossopharyngeal nerve. Changes in blood CO2, O2 or pH levels in the sinusoidal blood are detected by glomus cells, which then release neurotransmitters that activates the sensory nerve to relay this information to the brain.

Front 32

What vessels have loosest junctions?

Back 32

Junctions between endothelial cells of post capillary venules. At these places there is fluid loss from the circulatory system to the interstitium during inflammatory response--> edema. It is the junctions of zonula occludens that control the permeability.

Front 33

Pericytes:

Back 33

Mesenchymal cells with long cytoplasmic processes surrounding the endothelial layer along capillaries and post capillary venules. Can differentiate after vessel injury and become tunica media. However their primary function is contraction due to large amounts of actin, myosin and tropomyosin.

Front 34

Continuous capillaries:

Back 34

Most common, allows regulated exchange of materials, characterized by distinct continuity of endothelial cells in its wall. Lots of tight junctions, continuous basement membrane. Transport across vessel wall only by diffusion of transcytosis.

Front 35

Fenestrated capillaries:

Back 35

Allows extensive molecular exchange across the endothelium. Have tight junctions but fenestrated openings. The openings are usually covered by a thin diaphragm of heparan sulphate avoiding filtration of negatively charged proteins. Continuous basement membrane Found in tissues with a rapid interchange of substances; kidneys, intestines, choroid plexus and endocrine glands.

Front 36

Sinusoid/ discontinuous capillaries:

Back 36

Endothelial cells with large fenestrate without diaphragm, discontinuous basement membrane. Permits maximal exchange of macromolecules. Found in liver, spleen, some endocrine organs and bone marrow. Large diameters, up to 40 micrometers.

Front 37

Metarterioles:

Back 37

Branches of arterioles with precapillary sphincters which control circulation in capillary beds.

Front 38

Postcapillary venules:

Back 38

Have pericytes, are the primary site at which white blood cells leave the circulation at sites of infection or tissue damage.

Front 39

Characteristic feature of all venules:

Back 39

Large diameter of lumen compared to the overall thinness of the wall.

Front 40

Large veins:

Back 40

Have well developed tunica intima, but thin tunica media with few layers of smooth muscle and lots of connective tissue. Thick adventitia with longitudinal orientated smooth mm. Contain elastic fibers, but not elastic laminae like arteries.

Front 41

Valves of veins:

Back 41

Especially in large veins. Consist of semilunar folds of tunica intima, lined on both sides by endothelium.

Front 42

Lymphatic vessels:

Back 42

Thin closed- ended vessels that consists of a single layer of endothelium and an incomplete basal lamina. The vessels are held open by bundles of anchoring filaments of the elastic fiber system.

Front 43

Exceptions where lymphatics are not found:

Back 43

CNS and bone marrow

Front 44

Circulation in lymphatics is aided by:

Back 44

External forces like in veins: the muscle pump, thorax pump and artery pump. + contraction of smooth mm. in the lymphatic vessel wall.