5. The heart functions as a pump the right and the left half an atrium + a ventricle valves - atrioventricular semilunar the wall of the heart - three layers : the endocardium ( tunica interna ) - is in contact with blood the myocardium ( tunica media ) - intermediate solid layer of cardiac muscle tissue the epicardium ( tunica externa) - smooth external covering layer = visceral layer of pericardium
29. f enestrated capillaries occur in organs with rapid interchange of substances between cells and blood , i.e. intestinal villi, pancreas, choroid plexus, ciliary body Remember: modified fenestrated capillaries are contained in the renal glomeruli t he fenestrae are larger (70 - 90 nm) and more numerous than in the fenestrated capillaries of other organs, no diaphragms are present in the fenestrae sinusoidal capillaries , or sinusoids ( discontinuous capillaries ) are characterized by a tortuous path greatly enlarged diameter (30 - 40 m) and discontinuous basal lamina and absence of pericytes the endothelial cells are separated each other by numerous and large gaps that facilitate the transport of substances between blood and cells s inusoids occur mainly in the liver , some hematopoietic organs ( such as the bone marrow ), some endocrine glands (adenohypophysis, islets of Langerhans)
30. conduct lymph to the bloodstream they begin in the organs as blind lymphatic capillaries they are usually collapsed in histological sections capillaries collect tissue (interstitial) fluid from the organs . They are called lacteals in the intestine. small and medium-sized lymphatic vessels (lymphatics) c ontain the lymph and have valves in their lumina main ducts: ductus thoracicus - thoracic duct; right lympatic duct - truncus lymphaceus dx . both empty the lymph into the bloodstream at the junction of the left internal jugular and left subclavian veins (angulus venosus) Lymph vessels
31. Lymphatic capillaries very simple structure : their wall is composed of endothelial cells and fine reticular fibres of circular orientation the basal lamina is not developed Lymphatic vessels and ducts are thin walled tubes their wall s resemble the wall s of veins it consists of 3 layers: an intima, a media and an adventitia