CARDIOVASCULAR SYSTEM This resource is licensed under the Creative Commons Attribution Non-Commercial & No Derivative Works License

Objective Students should be able to: Compare the histological structures of arteries and veins. Relate the structure of different blood vessel walls to their function. Examine the nutrient blood supply and the innervation of large blood vessels. Compare the organisation and structure of exchange vessels in different tissues.

The Heart Into the right atrium comes blood from : From the right ventricle blood is pumped to the : Into the left atrium blood comes from : From the left ventricle blood is pumped to :

The Heart Into the right atrium comes blood from : The systemic circulation. From the right ventricle blood is pumped to the : Into the left atrium blood comes from : From the left ventricle blood is pumped to :

The Heart Into the right atrium comes blood from : The systemic circulation. From the right ventricle blood is pumped to the : Lungs. Into the left atrium blood comes from : From the left ventricle blood is pumped to :

The Heart Into the right atrium comes blood from : The systemic circulation. From the right ventricle blood is pumped to the : Lungs. Into the left atrium blood comes from : From the left ventricle blood is pumped to :

The Heart Into the right atrium comes blood from : The systemic circulation. From the right ventricle blood is pumped to the : Lungs. Into the left atrium blood comes from : From the left ventricle blood is pumped to :

Canine Thorax left view, left lung removed Sy C As A V2 S O V1 LA D L P LV RV A – Aorta D – Diaphragm LV- Left ventricle LA- Left auricle RV- Right ventricle O - Oesophagus S - Left subclavian artery L - Accessory lobe of right lung P - Left phrenic nerve innervating diaphragm Sy - Sympathetic trunk V1 - Dorsal vagal trunk V2 - Ventral vagal trunk C - Cervicothoracic ganglion (sympathetic) As - Ansa subclavia of cervicothoracic ganglion White arrow - Left interventricular groove (Sulcus interventricularis paraconalis)

Demo slide section through wall of heart. What three layers make up the wall of the heart? 1.0 mm

Demo slide section through wall of heart. What three layers make up the wall of the heart? Endocardium : lines atria and ventricles, forms valves. Myocardium : the cardiac muscle. Epicardium : covers the external surface of the heart – serous membrane also called the visceral pericardium. myocardium endocardium chamber of ventricle epicardium 1.0 mm

Demo slide section through developing rabbit heart LA: left atrium LV: left ventricle RV: right ventricle pulmonary artery ductus arteriosus bronchus oesophagus aortic arch (path of) lung LA pulmonary arch atrio-ventricular valve vena cava diaphragm LV RV liver ribs 1.0 mm

Identify the principal features of cardiac muscle. SLIDE 106 Cardiac muscle Identify the principal features of cardiac muscle. 50 µm

SLIDE 106 Cardiac muscle Identify the principal features of cardiac muscle. Intercalated discs, central nuclei (usually one but sometimes two) with perinuclear space, branched fibres, good blood supply. I I : intercalated discs central nucleus branched fibres blood vessels 50 µm

SLIDE 106 Cardiac muscle List the structures that allow cardiac muscle to act as a functional syncytium. TS section of fibres 25 µm

SLIDE 106 Cardiac muscle List the structures that allow cardiac muscle to act as a functional syncytium. Intercalated discs. Gap junctions. Branched fibres – lateral junctions. Rich vasculature. TS section of fibres 25 µm

Cardiac muscle demonstration slide for Purkinje fibres What type of cells make up Purkinje fibres? M : myocardium Pf : Purkinje fibres L : lumen of heart M Pf L 250 µm The endocardium is lost in this section

Cardiac muscle demonstration slide for Purkinje fibres What type of cells make up Purkinje fibres? Impulse conducting cardiac muscle cells. They form the atrioventricular bundle and its branches in the walls of the ventricles. M : myocardium Pf : Purkinje fibres L : lumen of heart M Pf L 250 µm The endocardium is lost in this section

SLIDE 56 Aorta (dog) elastic arteries This slide shows a transverse section through the aorta. Identify the layers of this structure at both low and high magnification. Suggest why there appear to be two lumens in this structure? 1.0 mm

SLIDE 56 Aorta (dog) elastic arteries This slide shows a transverse section through the aorta. Identify the layers of this structure at both low and high magnification. Suggest why there appear to be two lumens in this structure? The section was most likely cut at the divergence of the brachiocephalic trunk. aorta brachiocephalic trunk 1.0 mm

SLIDE 56 Aorta (dog) elastic arteries Identify the layers of this structure. 250 µm

SLIDE 56 Aorta (dog) elastic arteries Identify the layers of this structure. Tunica intima (interna) : consists of endothelial lining, sub endothelial connective tissue and internal elastic membrane. Tunica media : consists of circular smooth muscle layer, elastic and collagen fibres and the external elastic membrane. Tunica externa (adventitia) : outer covering. connective tissue sheath. tunica media lumen tunica externa tunica intima 250 µm

SLIDE 56 Aorta (dog) elastic arteries What structures are present in the tunica adventitia? What is their function? 250 µm

SLIDE 56 Aorta (dog) elastic arteries What structures are present in the tunica adventitia? Blood vessels – the vaso vasorum and autonomic nerves – the nervi vasorum. What is their function? They supply the wall of the blood vessel. adipocytes blood vessel nerve 250 µm

Micrograph of cross section of a nerve fascicle This section was stained with haematoxylin and eosin and shows the typical appearance of a nerve bundle running through the tissue. Remember the diameters of such bundles can vary considerably. 50 µm

SLIDE 56 Aorta (dog) elastic arteries Why are elastic fibres more prevalent in the aorta than in other arteries? 50 µm

SLIDE 56 Aorta (dog) elastic arteries Why are elastic fibres more prevalent in the aorta than in other arteries? The elasticity of the tunica media sustains blood pressure (reduces fluctuations) between heart beats. smooth muscle tunica media collagen elastic fibres tunica intima endothelium 50 µm

SLIDE 56 Aorta (dog) elastic arteries Why are elastic fibres more prevalent in the aorta than in other arteries? The elasticity of the tunica media sustains blood pressure (reduces fluctuations) between heart beats. Systole : elastic walls stretched. Pressure converted to elastic tension. Diastole : elastic rebound in arterial wall maintains blood pressure. smooth muscle tunica media collagen elastic fibres tunica intima endothelium 50 µm

Compare with previous slide 56 (aorta). SLIDE 51 Large veins Compare with previous slide 56 (aorta). 250 µm 1.0 mm

Are the same layers present in both vessels? SLIDE 51 Large veins Are the same layers present in both vessels? 100 µm

Are the same layers present in both vessels? Yes. SLIDE 51 Large veins Are the same layers present in both vessels? Yes. lumen tunica intima tunica media tunica adventitia 100 µm

In which layer are most of the smooth muscle cells found? SLIDE 51 Large veins In which layer are most of the smooth muscle cells found? 50 µm

SLIDE 51 Large veins In which layer are most of the smooth muscle cells found? In the tunica media; (walls of veins are thinner relative to the size of the lumen). lumen endothelium muscle cells in tunica media tunica adventitia 50 µm

SLIDE 51 Large veins Junction between tunica media and tunica adventitia. Dark pink staining muscle cells more numerous in tunica media. A small venule is seen in the tunica adventitia. venule 50 µm

At high magnification the depth of the tunica intima can be seen. SLIDE 51 Large veins At high magnification the depth of the tunica intima can be seen. 25 µm

At high magnification the depth of the tunica intima can be seen. SLIDE 51 Large veins At high magnification the depth of the tunica intima can be seen. endothelial cells smooth muscle cell in tunica media tunica intima 25 µm

SLIDE 52 Large vein (Vena cava) elastic stain In this section elastic tissue has been stained black. Which region has the most elastic tissue? 250 µm

SLIDE 52 Large vein (Vena cava) elastic stain In this section elastic tissue has been stained black. Which region has the most elastic tissue? Tunica media. tunica intima tunica media tunica adventitia 250 µm

SLIDE 52 Large vein (Vena cava) elastic stain At higher magnification, elastic fibres can be seen. elastic fibres 100 µm

SLIDE 57 Muscular arteries Muscular arteries are usually smaller diameter than elastic ones. Autonomic regulation of these vessels produces changes in blood flow to organ systems. 1.0 mm

SLIDE 57 Muscular arteries How does the structure of a muscular artery relate to its compliance? 100 µm

SLIDE 57 Muscular arteries How does the structure of a muscular artery relate to its compliance? Thicker musculature - lower compliance. tunica adventitia tunica media tunica intima blood cells smooth muscle cells 100 µm

SLIDE 57 Muscular arteries The smooth muscle cells in the tunica media 50 µm

SLIDE 57 Muscular arteries What is the functional significance of the arrangement of these smooth muscle cells? The smooth muscle is a near-circular tight helical arrangement. Muscular arteries control blood flow to various organs. 50 µm

Femoral vein The three layers tunica intima, tunica media and tunica adventitia can be identified. The thickest layer is the tunica adventitia. tunica intima lumen tunica media tunica adventitia 250 µm

Identify the layer of endothelial cells lining the vein. Femoral vein Identify the layer of endothelial cells lining the vein. 50 µm

Identify the layer of endothelial cells lining the vein. Femoral vein Identify the layer of endothelial cells lining the vein. tunica adventitia tunica media endothelium tunica intima 50 µm

SLIDE 59 Muscular artery (elastic stain) Muscular artery stained to show elastic fibres. 0.5 mm

SLIDE 59 Muscular artery (elastic stain) The internal elastic membrane of the tunica intima can be seen. Also the external elastic membrane at the base of the tunica media. The tunica adventitia has the most elastic fibres (stained black) and is of a similar thickness to the tunica media. 100 µm

SLIDE 59 Muscular artery (elastic stain) The internal elastic membrane of the tunica intima can be seen. Also the external elastic membrane at the base of the tunica media. The tunica adventitia has the most elastic fibres (stained black) and is of a similar thickness to the tunica media. external elastic membrane internal elastic membrane of tunica intima tunica adventitia tunica media endothelium elastic fibres 100 µm

SLIDE 59 Companion vein (elastic stain) Again with the companion vein most of the elastic fibres are staining up in the tunica adventitia, which is the thickest layer. 100 µm

SLIDE 59 Companion vein (elastic stain) Again with the companion vein most of the elastic fibres are staining up in the tunica adventitia, which is the thickest layer. endothelium of tunica intima tunica media elastic fibres in tunica adventitia 100 µm

SLIDE 34 Arterioles and venules (stomach submucosa) In this section of the stomach; identify the submucosa and locate arterioles and venules. 250 µm

SLIDE 34 Arterioles and venules (stomach submucosa) In this section of the stomach; identify the submucosa and locate arterioles and venules. mucosal layers submucosa muscularis 250 µm

SLIDE 34 Arterioles and venules (stomach submucosa) Why is the lumen of the arteriole smaller than that of the venule? 100 µm

SLIDE 34 Arterioles and venules (stomach submucosa) Why is the lumen of the arteriole smaller than that of the venule? Compliance. A : arteriole V V : venule A A V 100 µm

SLIDE 34 Arterioles and venules (stomach submucosa) The walls of the arterioles have distinct layers of smooth muscle and regulate the blood flow through the capillary bed. The thin walls of venules may have a few smooth muscle cells. 50 µm

Arterioles and venules Identify which of these structures contributes a) most to peripheral resistance: b) least to peripheral resistance: Elastic artery arteriole capillary vein venule

Arterioles and venules Identify which of these structures contributes a) most to peripheral resistance: b) least to peripheral resistance: Elastic artery arteriole capillary vein venule a

Arterioles and venules Identify which of these structures contributes a) most to peripheral resistance: b) least to peripheral resistance: Elastic artery arteriole capillary vein venule a b

Capillaries and sinusoids Identify capillaries or sinusoids in the following slides: Capillaries in loose connective tissue - slide 118. Capillaries in skeletal muscle - slide 6 (goat tongue). - slide 103. Capillaries in cardiac muscle - slide 106. Capillaries in loose connective tissue - slide 58. Locate sinusoids in the liver - slide 49. - slide 21.

SLIDE 118 Capillary in loose connective tissue Viewed under an oil immersion lens the flattened nature and single layer of simple squamous epithelium (endothelium) of the capillary wall can be seen. REVISION Simple Squamous Epithelium… a single layer of thin and flattened cells well adapted for active transport and movement of gases and metabolites. N : nuclei of endothelial cells N N 25 µm

SLIDE 6 Skeletal muscle (goat) Capillaries in the skeletal muscle of the tongue. Low magnification view showing surface papillae, striated muscle layers and glandular units. muscle salivary glands 1.0 mm

SLIDE 6 Skeletal muscle (goat) The striated muscle fibres of the tongue run in many directions. Sections of tongue muscle provide good examples of capillaries cut in longitudinal and in transverse section. 100 µm

SLIDE 6 Skeletal muscle (goat) At high magnification the individual blood cells can be resolved in the capillaries. 25 µm

SLIDE 6 Skeletal muscle (goat) At high magnification the individual blood cells can be resolved in the capillaries. C : capillaries M E : endothelial cells C M : muscle nuclei C E M E 25 µm

SLIDE 103 Striated skeletal muscle (rat) Shown : A-bands. I- bands. Z-lines sarcomere capillary in the endomysium 10 µm

Capillaries in cardiac muscle. SLIDE 106 Cardiac muscle Capillaries in cardiac muscle. red blood cells in capillary 25 µm

Capillaries in cardiac muscle. SLIDE 106 Cardiac muscle Capillaries in cardiac muscle. red blood cells in capillary 50 µm

SLIDE 58 Loose connective tissue (spread) Capillaries in loose (areolar) connective tissue. This slide is a spread preparation. C : capillaries P : pericytes A C A : adipocytes C P A P 50 µm

SLIDE 58 Loose connective tissue (spread) Areolar connective tissue. How can you distinguish the blood capillaries? The capillaries are cellular, the endothelial cells forming the walls are visible as are often the circulating red and white blood cells. C C C : capillaries F adipocytes F : fibroblasts C 25 µm

SLIDE 49 Adult liver (pig) Sinusoids in liver lobules. Hepatocytes form cords of cells with at least one surface against a sinusoid. 250 µm

SLIDE 49 Adult liver (pig) Sinusoids in liver lobules. Hepatocytes form cords of cells with at least one surface against a sinusoid. hepatocyte cords central vein sinusoids portal area 250 µm

SLIDE 49 Adult liver (pig) Sinusoids in liver lobules. 100 µm

SLIDE 49 Adult liver (pig) Sinusoids in liver lobules. C : central vein hepatocytes sinusoids C 100 µm

SLIDE 21 Sinusoids in liver (Stained for reticular fibres) Revision : Note the loose interwoven network created by the reticular fibres that are stained black. What is this protein fibre composed of? Collagen type III. Why is this protein fibre most appropriate in these tissues? Reticular fibres support tissues and organs, protecting cells and structures subjected to volume changes. hepatocytes reticular fibres sinusoids 25 µm

Capillaries and sinusoids State three differences between sinusoids and capillaries.

Capillaries and sinusoids State three differences between sinusoids and capillaries. 1 . Sinusoids usually larger and more varied shape than capillaries. Sinusoids may be fenestrated, have gaps and pores in the endothelium. They have a discontinuous basal lamina. What structures connect individual endothelial cells?

Capillaries and sinusoids State three differences between sinusoids and capillaries. 1 . Sinusoids usually larger and more varied shape than capillaries. Sinusoids may be fenestrated, have gaps and pores in the endothelium. They have a discontinuous basal lamina. What structures connect individual endothelial cells? Gap or tight junctions.

Capillaries and sinusoids What is an arteriovenous anastamosis? How do capillaries resist collapse? In which vessels are valves found, and why?

Capillaries and sinusoids What is an arteriovenous anastamosis? A by-pass of the capillary bed between an arteriole and a venule. How do capillaries resist collapse? In which vessels are valves found, and why?

Capillaries and sinusoids What is an arteriovenous anastamosis? A by-pass of the capillary bed between an arteriole and a venule. How do capillaries resist collapse? Arteriole blood pressure maintains capillary shape. In which vessels are valves found, and why?

Capillaries and sinusoids What is an arteriovenous anastamosis? A by-pass of the capillary bed between an arteriole and a venule. How do capillaries resist collapse? Arteriole blood pressure maintains capillary shape. In which vessels are valves found, and why? In some veins. Particularly those draining the limbs. They prevent backflow and back pressure.

Lectures. Dr. C.Lawson. First Year Histology. 011. Cardiovascular. J.Bredl. 03-09-03. Gross Anatomy Correlates. S.Frean. 08-09-03. Histology Slides and Stains. Tanya Hopcroft. New compressed version 07-2006. updated 2007.