Cardiorenal I Flashcards
Epicardium
the most external layer of the heart wall and is also called the visceral layer of the serous pericardium. It includes the following components: -mesothelial lining -CT underneath
Myocardium
the principal component of the heart wall. It is formed by cardiac muscle. This part of the ventricles is substantially thicker than that of the atria
Endocardium
Is the most internal layer of the heart wall. It includes the following components: -endothelium -subendothelial CT -impulse conducting system of the heart
Mesothelial Lining (of myocardium)
covers the external surface of the heart
Connective Tissue underlying Myocardial Mesothelium
- Loose connective tissue, adipose tissue. 2. Nerves pass through this layer. 3. Blood vessels travel to the myocardium through this layer.
Endothelium of the heart
is the epithelium that lines the luminal surface of the heart.
Subendothelial CT
a thin sheath of connective tissue located directly beneath the endothelial lining
Impulse Conducting System
The deeper layer of subendo CT contains this nerve system
Fibrous Skeleton
Heart walls are supported by a well-developed fibrous skeleton that also extends into the valves. The internal fibrous skeleton of the heart consists of four fibrous rings that surround the valve orifices and two trigones, which connect the rings together. These structures are composed of dense irregular connective tissue
Fibrous ring of the pulmonary trunk
surrounds the base of the pulmonary trunk
Fibrous ring of the aorta
surrounds the root of the aorta
Left atrioventricular ring, or ring of the mitral valve
surrounds the left atrioventricular orifice
Right atrioventricular ring, or ring of the tricuspid valve
surrounds the right atrioventricular orifice
Left fibrous trigone connects
connects left atrioventricular and aortic fibrous rings
Right fibrous trigone connects
connects left and right atrioventricular fibrous rings
membranous part of the interventricular septum
devoid of cardiac muscle and is composed of dense irregular connective tissue. It contains part of the atrioventricular bundle
Valves
composed of connective tissue covered with endothelium. The loose connective tissue acts as a shock-absorber. Dense irregular connective tissue with elastic fibers provides structural support for the valve. Valves are composed of three layers: -Fibrosa -Spongiosa -Atrialis
Fibrosa
formed of dense irregular connective tissue connected to the corresponding fibrous ring. It extends from the base along the ventricular side of the atrioventricular valves.
Spongiosa
is sandwiched between the fibrosa and atrialis and forms the core of the valve. It is formed of loose connective tissue with large amount of elastic fibers. It is most prominent in the free edge of the valve and acts as a shock-absorber by dampening vibrations when the valve closes. A few adipose tissue cells may be seen within this layer occasionally.
Atrialis
covers the atrial aspect of the spongiosa. It is rich in proteoglycans and contains elastic fibers and occasional smooth muscle cells.
Clinical comment: mitral valve prolapse
is one of the most common valve pathologies affecting 5-10 % of the population worldwide. It is caused by the abnormal formation of structural proteins that form the valve, such as collagen or fibrillin. The mutation of fibrillin (one of the proteins that form elastic fibers) gene causes so-called Marfan syndrome. Patients with this syndrome tend to suffer from this condition.
Cardiac muscle contracts dependently/independently of nerve stimulation.
independently The innervation from the autonomic nervous system does not initiate the heartbeat, but regulates the heart rate
The heart rate can be altered by:
i. Parasympathetic nerves decrease the heart rate. ii. Sympathetic nerves increase the heart rate. iii. Hormones and other chemical substances can change the heart rate and force of contraction.
Examples that increase the force of contraction and increase the heart rate.
epinephrine, thyroid hormones, caffeine, and many other substances
Cardiac conducting system
The heartbeat is initiated, coordinated, and regulated by modified cardiac muscle cells that form the cardiac conducting system. Cardiac conducting cells called the Purkinje fibers are cardiac muscle cells modified for the conduction of electric impulses in a way similar to nerve cells. Purkinje fibers form nodes and bundles including the sinoatrial and atrioventricular nodes and the bundle of His.
Myocardial infarction
caused by the obstruction of coronary arteries and loss of blood supply to the cardiac muscle for more than 20 min
Myocarditis
inflammation of the myocardium caused by infection or intoxication. It causes inflammatory changes to the cardiac muscle.
myxoma
One of the more common benign tumors of the heart. most commonly found in the left atrium and are best identified using echocardiography
Malignant tumors
usually originate elsewhere and metastasize to the heart. One of the most common tumors that spread into the heart is metastatic melanoma
Angiosarcoma
one of the rare tumors that actually originate in the heart. It accounts to about one third of all of the malignant tumors that originate in the hear
Cardiomyopathy
results in the change in the structure of the cardiac muscle and weakens the heart
General structure of arteries and veins
The walls of arteries and veins are composed of three layers that are called tunics: tunica intima, tunica media, and tunica adventitia. Different arteries and veins can be differentiated from each other by the thickness of the wall and by the composition and thickness of individual tunics
Tunica intima (heart)
the most internal layer of the vessel. It consists of three components: endothelium, subendothelial connective tissue, and internal elastic lamina
Endothelium of the Tunica Intima (heart)
Endothelium with basal lamina lines the luminal surface. Endothelial cells participate in structural and functional integrity of the vascular wall. They are responsible for several important properties of blood vessels: i. Endothelial cells represent the barrier between the blood and underlying tissue. ii. Endothelial cells are capable of controlling the blood flow through the secretion of agents that constrict or dilate blood vessels iii. Regulation or modulation of immune responses through the regulation of leukocyte adhesion and through production of several interleukins (IL-1, IL-6, IL-8). iv. Endothelial cells express high metabolic and hormonal activity mainly through the secretion of various growth factors, such as hemopoietic colony-stimulating factors (CSF), fibroblast growth factor, and platelet-derived growth factor (PDGF), as well as inhibitors such as transforming growth factor β (TGF β). Endothelial cells are responsible for the conversion of angiotensin I to angiotensin II (in the presence of ACE).
Selective permeability barrier of Tunica Intima
allows selective movement of small and large molecules from the blood to the tissue and back. Simple diffusion is only possible for small uncharged molecules such as oxygen or carbon dioxide. Other molecules can travel across the endothelium via three different pathways: a. Transcellular pathway b. paracellular pathway c. gaps/fenestrations
Transcellular pathway
allows active transport across the plasma membrane. i. Transcellular pathway uses numerous pinocytic vesicles or caveolae (clathrin-independent form of endocytosis) to transport material from blood to the cell. ii. Clathrin-dependent endocytosis is used for the transport of LDL and cholesterol.
Paracellular pathway
allows passive transport across the zonula occludens
non-thrombogenic barrier
Endothelial cells provide the non-thrombogenic barrier between blood platelets and subendothelial tissue. a. They produce anticoagulants, such as thrombomodulin. b. Damage to the endothelial cells causes them to release the prothrombogenic agents, such as von Willebrand factor, which leads to blood clotting.
Von Willerbrand Factor
prothrombic agent that leads to blood clotting antibodies to von Willebrand factor can be used to identify endothelium-derived tumors, e.g. angiosarcomas.
Vasoconstrictors
ACE (angiotensin-converting enzyme), endothelin, thromboxane.
Vasodilators
NO or prostacyclin
Subendothelial layer of Tunica Intima (heart)
loose CT
Internal Elastic lamina of Tunica Intima (heart)
a flattened fenestrated sheet of elastin, which separates tunica intima from media
Tunica media (heart)
the middle layer that mostly consists of smooth muscle and is especially well-developed in arteries. It includes: a. Circularly arranged smooth muscle fibers. b. External elastic lamina separates media from adventitia
Tunica adventitia (heart)
the most external layer that is usually composed mostly of connective tissue. It includes the following elements: a. Longitudinally arranged smooth muscle fibers. b. Loose connective tissue is located primarily on the periphery of adventitia. c. Small blood vessels that supply the walls of the larger blood vessels are called vasa vasorum. d. Nerves that innervate the blood vessels and travel through the adventitia are called nervi vasorum.
Arteries (three major types)
a. Large elastic arteries, which are the conducting vessels. b. Muscular arteries, which are medium-sized distributing vessels. c. Small arteries and arterioles, which are small resistance vessels.
Large elastic arteries
nclude some of the largest arterial blood vessels in the body, such as the pulmonary artery and aorta. Some of their larger branches such as the subclavian, common carotid, and others, belong to this type as well. These are conducting vessels.
Tunica Intima of Large Arteries
composed of typical elements of a blood vessel including: i. Endothelium ii. subendo layer iii. inconspicuous internal elastic lamina
Tunica Media of Large Arteries
large arteries is extremely thick. In individuals with hypertension both thickness of the layer and the number of the lamellae increases. i. Numerous elastic lamellae form concentric layers between the muscle cells. The lamellae are formed by elastin. ii. Smooth muscle fibers are circularly arranged
Large Artery Endothelium
with basal lamina. Endothelial cells contain rod-like inclusions called Weibel-Palade bodies, which contain von Willebrand factor
Tunica adventitia of large arteries
relatively thin. It contains collagen and elastic fibers, fibroblasts and macrophages. There is a number of minor blood vessels, vasa vasorum and nerves, nervi vasorum are typically present in this layer as well.
Muscular arteries
are similar to large arteries, but generally differ in smaller size, in having very little elastic material in the tunica media, and in having a prominent internal elastic lamina. These are distributing vessels.
Tunica intima of muscle arteries
thinner than in large arteries. It consists of the same layers: i. Endothelium with basal lamina. ii. Thin subendothelial layer with collagen and elastic fibers. iii. Prominent internal elastic lamina.
Tunica media of muscular arteries
has very few elastic lamellae. It is mostly composed of circularly arranged smooth muscle fibers. The external elastic lamina is well-developed. It is thicker than the adventitia.
Tunica adventitia of muscular arteries
is relatively well-developed. It contains collagen and elastic fibers, fibroblasts and macrophages. There is a small number of minor blood vessels, vasa vasorum, and nerves, nervi vasorum, typically present in this layer as well, although they are not as abundant as in the elastic arteries.
Small arteries and arterioles
small in size and contain fewer layers of smooth muscle in the tunica media. Tunica adventitia in these blood vessels is thin. These are resistance vessels. a. Small arteries have up to eight layers of smooth muscle fibers in the tunica media. Typically there is an internal elastic lamina. b. Arterioles have one or two layers of smooth muscle in the tunica media. Internal elastic lamina is not developed. Arterioles control the blood flow to the capillary network by contracting the smooth muscle cells. Depending on the type of activity the arterioles direct the blood to the organs that need it most. During physical exercise blood goes to the skeletal muscle. After the meal the blood is directed to the intestine.
Atherosclerosis
formation of lesions in the tunica intima. These lesions contain the following components: i. Fibrous tissue. ii. Smooth muscle cells. iii. Macrophages. iv. Foam cells. v. Cholesterol crystals. vi. Cell debris. b. Progression of lesions causes disruption of the endothelium, blood stasis, and thrombosis. c. This eventually may result in the occlusion of the vessel. d. Possible consequences are responsible for over 50 % of deaths in the US and include myocardial infarction and stroke.
Capillaries
are the smallest blood vessels in the body. The diameter of capillary is just large enough for blood cells to pass through it (one at a time). They do not exhibit the typical three tunics in their walls. Their walls are extremely thin to allow fluids containing gases, metabolites, and waste products to move through them. Each capillary consists of a single layer of endothelial cells and pericytes enclosed by a basal lamina.
Pericytes
undifferentiated mesenchymal stem cells that surround the capillary with branching cytoplasmic processes. Pericytes provide vascular support and promote stability of capillaries and postcapillary venules. They can differentiate into a variety of cell types, including adipocytes, fibroblasts, chondroblasts, and osteoblasts
Continuous capillaries
e found in the muscle tissue, lung, and central nervous system. They are characterized by the presence of occluding junctions between cells. The basal lamina in these capillaries is continuous.
Fenestrated capillaries
are found primarily in the tissues where there is substantial fluid transport, such as intestinal villi, choroid plexus, renal glomeruli, and in the endocrine organs. They are characterized by the presence of many small (10-100 nm) fenestrations in the endothelial cells (not in the basal lamina) that help to filter the fluid in.
Discontinuous capillaries (or sinusoids)
are large capillaries found in specialized organs such as liver, spleen, and bone marrow. In these rather large capillaries endothelial cells can be completely separated by larger gaps (150-175 nm) that extend into the basal lamina, which is also fenestrated. This allows the endothelium to act as a filter.
Veins
generally have thinner walls than the arteries. There are three major types of veins: small veins, or venules, medium veins, and large veins.
Postcapillary venules
receive blood from the capillaries. They do not have tunica media. This is the principal site of emigration of white blood cells into tissue. The emigration is initiated by such agents as histamine and serotonin, which cause the increase in the permeability of venules and migration of WBCs that is accompanied by edema. The postcapillary venules of the lymphatic organs have tall endothelium and are called high endothelial venules.
Muscular venules
collect blood from the postcapillary venules and can be up to 1 mm in diameter. They have very little smooth muscle in the tunica media
Medium veins
are less than 1 cm in diameter. The three tunics are readily observable in the medium veins. They collect blood from muscular venules.
Medium Vein Tunica Intima
consists of the same layers as in the arteries: i. Endothelium with basal lamina. ii. Very thin subendothelial layer with collagen and elastic fibers. iii. Very thin internal elastic lamina.
Medium Vein Tunica Media
of medium veins is much thinner than in the arteries of the same diameter. It is thinner than the tunica adventitia (different from an artery of the same size).
Medium Vein Tunica adventitia
is thicker than media and contains: i. Elastic fibers. ii. Collagen fibers. iii. Fibroblasts and macrophages. iv. Vasa vasorum. v. Nervi vasorum.
Large Veins
are more than 1 cm in diameter. They deliver blood to the heart. The three tunics are readily observable in the large veins. The tunicas are similar to the medium veins, but the boundaries are not as distinct.
Large Vein Tunica Intima
consists of the same layers as in the medium vein, but the subendothelial layer of connective tissue is thicker and the internal elastic membrane is prominent.
Large Vein Tunica Media
is inconspicuous
Large Vein Tunica Adventitia
a is extremely well-developed in large veins and has many longitudinally oriented smooth muscle fibers in it.
Valves
Many veins have valves that guarantee the unidirectional flow of blood through them. They consist of a thin layer of connective tissue covered with endothelial lining
Lymphatic vessels
convey fluid from tissues to the large veins collect the fluid from lymphatic capillaries and deliver it to the blood vascular system by draining into large veins in the base of the neck. Before lymph is returned to blood, it goes through lymph nodes, where it is exposed to the immune system. Lymphatic vessels have valves that prevent the backflow of lymph and guarantee the unidirectional flow of lymph.
lymphatic capillaries
The smallest lymphatic vessels. They have greater permeability than blood capillaries, which allows them to collect protein-rich fluid from intercellular spaces. The fluid is then delivered to lymphatic vessels. The fluid at this point is called lymph. Lymphatic capillaries are most common in the loose connective tissue.
