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Main page | Structure | Departments | Department of Histology and Embryology | Materials for students | Modul 2 | URINARY SYSTEM.

URINARY SYSTEM.
KIDNEY   (KD).
1. KD is composed of : a) connective tissue capsule, b) CORTEX, c) MEDULLA (in centre).
2. Cortex  is composed of NEPHRONS - it are structural and functional units of KD.
3. NEPHRON is composed of: 1) renal corpuscle, 2) system of tubules. Renal corpuscle is composed of: a) glomerulus, b) Bowmans capsule. Glomerulus is composed of 40 fenestrated capillaries.
Bowmans capsule  is composed of : parietal layer, .visceral layer, urinary space between 2 layers.
Visceral layer is composed of PODOCYTES.    Podocyte- is irregular-shaped epithelial cell with
long primary process, which branches on short pedicels (secondary processes).
Tri-layered basal lamina locates between fenestrated capillary and podocytes  and contains lamina densa. Lamina densa is composed of mashwork from collagen fibrills. Diameter of openings =4 nm.
Filtration barrier is composed of: 1) fenestrated endothelial cell of glomerulus, 2) tri-layered basal lamina, 3) filtration SLITS between pedicels of PODOCYTE.
1st phase of urine production – is ultrafiltration. It happens from glomerular capillaries through filtration barrier into urinary space. 5 substancies are filtered and pass to proximal and distal tubules. That are:1) 150 liters of H2O per day, 2) LOW molecular blood proteins and amino acids, 3)glucose, 4) Na+ ions, 5) urea. This mixture is PRIMARY urine. In proximal and distal nephron  tubules primary urine undergoes to 2nd phase of urine production – it is reabsorption (RA).. It happens from lumen of tubules through epithelial cell into secondary peritubular capillaries. Wall of proximal tubules is composed of  simple cuboidal epith. 1cell has abundance of 4 organells, that fulfil RA :1) apical microvilli (for RA of glucose), 2) basal folds (for RA of H2O), 3) mitochondria -for RA of Na ions, 4) lysosomes/pinocytotic vesicles (for RA of proteins). After proximal tubules proteins and glucose disappear completely.  Wall of distal tubules is composed of simple cuboidal epith. 1cell has abundance of ONLY 2 organells, that fulfil RA : 1) basal folds (RA of H2O), 2) mitochondria ( RA of Na ions).
Wall of collecting tubule is composed of simple columnar/cuboidal epith. Cells are classified on:
1) Principal (pale) cell . Funct.: a) after ADH stimulation it reabsorbs H2O, b) secrets prostaglandins in blood. 2) Intercalated cells. A lot of mitochondria. Funct.:Secretion of H+ ions into urine. It is 3rd phase of urine production — secretory phase.
After collecting tubules fluid becomes secondary urine. It contains only 3 subst.(after filtration of 5 subst.): a) H2O (1.5-2.0 L/day),  b) toxic UREA, c) Na+ ions. It is released from the body.
RENIN apparatus: 1) JUXTAGLOMERULAR cells. It are :a) locate in tunica media of afferent arteriole, b) tissue type-are modified smooth muscle cells with secretory granules, c) Funct.: secretion of enzyme RENIN in blood, 2) MACULA DENSA cells. It are: a) locate in wall of distal tubules, b) tissue type-is TALL, NARROW COLUMNAR epithelial cells, nuclei are near to each other, c) basement membrane is absent, d) Funct.: it are Na+ receptors.
URETER
Wall is composed of 4 TUNICS: 1) folded T. MUCOSA, 2) T.  SUBMUCOSA (L.I.C.T.), 3) MUSCULARIS externa, 4) T.adventitia(L.I.C.T). T. mucosa is composed of: a) TRANSITIONAL epith., b) lamina propria (L.I.C.T). Muscularis externa (smooth muscle tiss.) has a) in UPPER one half 2 layers (inner –longitud., outer –circular), b) in LOWER one half 3 layers (outer and inner -are longitud., middle- circular).
URINARY BLADDER
Wall is composed of 4 TUNICS: 1) folded (excepting trigone) T. MUCOSA, 2) T. SUBMUCOSA (L.I.C.T.), 3) MUSCULARIS externa, 4) T.adventitia(L.I.C.T). T. mucosa is composed of: a) TRANSITIONAL epith., b) lamina propria (L.I.C.T ). Muscularis externa (smooth muscle tiss.) has 3 layers (outer and inner -are longitud., middle- circular). Pecularities of trigone: a) T.mucosa is smooth, NOT folded, b) T. submucosa is absent.
Составитель – доцент В.В. Бондаренко.
 
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