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HEART. MICROCIRCULATORY BED.
Heart.
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Heart wall is composed 3 tunics:
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Endocardium (inner tunica) ;
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Myocardium (middle, muscular tunica);
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Epicardium (outer tunica).
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Endocardium is composed 4 layers:
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endothelium (simple squamous epithelium);
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subendothelial layer (loose irregular connective tissue);
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layer of smooth muscle cells and elastic fibres;
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outer layer of connective tissue.
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Myocardium is composed striated cardiac muscle tissue. It presented by cardiac muscle fibres. One muscle fibre is chain of cardiac muscle cells, which attached “end-to-end” by intercalated disks.
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Myocardium of ventricles contains contractile cardiac muscle cells. These cells are columnar-shaped, have 1-2 nuclei and abundance of myofibrills. Its function- is contraction.
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Myocardium of atria contains secretory cardiac muscle cells. These cells are star-shaped. Cytoplasm contains secretory granules. Its function is secretion into blood hormone “Na-uretic factor”.
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After death, zone of necrosis of cardiac muccle cells is replaced by connective tissue scar.
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Epicardium, like pericardium, is composed of layer of connective tissue, which covered by mesothelium (.simple squamous epithelium).
Microcirculatory bed
(capillaries, arterioles, venules).
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Muscles, lungs, skin contain capillaries with continuous endothelium. Its wall is composed of 2 cell types: endothelial cells and pericytes.
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Small intestine, endocrine glands containe capillaries with fenestrated endothelium. Cytoplasm of endothelial cells has narrow pores, named fenestrae.
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Liver, red bone marrow, spleen contain sinusoidal capillaries. Cytoplasm of endothelial cells has wide clefts. Pericytes are absent
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Main function of all capillary types is gases and nutrients exchange.
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Wall of arterioles is composed of 3 tunics:
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tunica intima (or interna)
B. tunica media
C. tunica adventitia (or externa) – loose irregular connective tissue
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Tunica intima is composed of 3 layers:
- endothelium
- subendothelial layer (loose irregular connective tissue)
-internal elastic membrane
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Tunica media contains strictly and only1-2 layers of smooth muscle cells.
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Function - arterioles regulate level of blood pressure.
Куратор темы – доцент В.В. Бондаренко.
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