HISTOLOGY OF THE URINARY SYSTEM

Transcription

1 HISTOLOGY OF THE URINARY SYSTEM

2 The Urinary System Kidneys, ureters, urinary bladder & urethra Urine flows from each kidney, down its ureter to the bladder and to the outside via the urethra Filter the blood and return most of water and solutes to the bloodstream 26-2 Tortora & Grabowski 9/e

3 Overview of Kidney Functions Regulation of blood ionic composition Regulation of blood ph, osmolarity & glucose Regulation of blood volume conserving or eliminating water Regulation of blood pressure Na+, K+, Ca+2, Cl- and phosphate ions secreting the enzyme renin adjusting renal resistance Release of erythropoietin & calcitriol Excretion of wastes & foreign substances 26-3 Tortora & Grabowski 9/e

4 External Anatomy of Kidney Paired kidney-bean-shaped organ 4-5 in long, 2-3 in wide, 1 in thick Found just above the waist between the peritoneum & posterior wall of abdomen retroperitoneal along with adrenal glands & ureters Protected by 11th & 12th ribs with right kidney lower Tortora & Grabowski 9/e

5 External Anatomy of Kidney Blood vessels & ureter enter hilus of kidney Renal capsule = transparent membrane maintains organ shape Adipose capsule that helps protect from trauma Renal fascia = dense, irregular connective tissue that holds against back body wall

6 Internal Anatomy of the Kidneys Parenchyma of kidney renal cortex = superficial layer of kidney renal medulla inner portion consisting of 8-18 cone-shaped renal pyramids separated by renal columns renal papilla point toward center of kidney Drainage system fills renal sinus cavity cuplike structure (minor calyces) collect urine from the papillary ducts of the papilla minor & major calyces empty into the renal pelvis which empties into the ureter 26-6 Tortora & Grabowski 9/e

7 Internal Anatomy of Kidney What is the difference between renal hilus & renal sinus? Outline a major calyx & the border between cortex & medulla.

8 Blood & Nerve Supply of Kidney Abundantly supplied with blood vessels receive 25% of resting cardiac output via renal arteries Functions of different capillary beds glomerular capillaries where filtration of blood occurs vasoconstriction & vasodilation of afferent & efferent arterioles produce large changes in renal filtration peritubular capillaries that carry away reabsorbed substances from filtrate vasa recta supplies nutrients to medulla without disrupting its osmolarity form Sympathetic vasomotor nerves regulate blood flow & renal resistance by altering arterioles 26-8 Tortora & Grabowski 9/e

9

10 Blood Vessels around the Nephron Glomerular capillaries are formed between the afferent & efferent arterioles Efferent arterioles give rise to the peritubular capillaries and vasa recta

11 Blood Supply to the Nephron

12 The Nephron Kidney has over 1 million nephrons composed of a corpuscle and tubule Renal corpuscle = site of plasma filtration Renal tubule glomerulus is capillaries where filtration occurs glomerular (Bowman s) capsule is double-walled epithelial cup that collects filtrate proximal convoluted tubule loop of Henle dips down into medulla distal convoluted tubule Collecting ducts and papillary ducts drain urine to the renal pelvis and ureter Tortora & Grabowski 9/e

13

14

15

16

17 n o r h p Ne basic structural and functional unit of the kidney. Its chief function is to regulate the concentration of water and soluble substances like sodium salts by filtering the blood, reabsorbing what is needed and excreting the rest as urine.

18 A nephron eliminates wastes from the body, regulates blood volume and blood pressure, controls levels of electrolytes and metabolites, and regulates blood ph. Its functions are vital to life and are regulated by the endocrine system by hormones such as antidiuretic hormone, aldosterone, and parathyroid hormone.

19 microscopic units of a kidney, have 2 main parts, renal corpuscle (Bowman's capsule with glomerulus) renal tubule.

20

21 RENAL CORPUSCLE glomeruli surrounded by Bowman's capsules. Bowman's capsule -- the cup-shaped top of a nephron. It is the sack-like Bowmans's capsule that surrounds the glomerulus. Glomerulus -- a network of blood capillaries tucked into Bowman's capsule.

22

23

24 Histology of Renal Tubule & Collecting Duct Proximal convoluted tubule Descending limb of loop of Henle simple cuboidal with brush border of microvilli that increase surface area simple squamous Ascending limb of loop of Henle simple cuboidal to low columnar forms juxtaglomerular apparatus where makes contact with afferent arteriole macula densa is special part of ascending limb Distal convoluted & collecting ducts simple cuboidal composed of principal & intercalated cells which have microvilli

25 Juxtaglomerular Apparatus Structure where afferent arteriole makes contact with ascending limb of loop of Henle There are three cellular components of the apparatus which are the; macula densa, extraglomerular mesangial cells, juxtaglomerular cells (also known as granular cells)

26 Number of Nephrons Remains constant from birth any increase in size of kidney is size increase of individual nephrons If injured, no replacement occurs Dysfunction is not evident until function declines by 25% of normal (other nephrons handle the extra work) Removal of one kidney causes enlargement of the remaining until it can filter at 80% of normal rate of 2 kidneys Tortora & Grabowski 9/e

27 Overview of Renal Physiology Nephrons and collecting ducts perform 3 basic processes glomerular filtration tubular reabsorption water & useful substances are reabsorbed into the blood tubular secretion a portion of the blood plasma is filtered into the kidney wastes are removed from the blood & secreted into urine Rate of excretion of any substance is its rate of filtration, plus its rate of secretion, minus its rate of reabsorption Tortora & Grabowski 9/e

28 Overview of Renal Physiology Glomerular filtration of plasma Tubular reabsorption Tubular secretion

29 Glomerular Filtration Blood pressure produces glomerular filtrate Filtration fraction is 20% of plasma 48 Gallons/day filtrate reabsorbed to 1-2 qt. urine Filtering capacity enhanced by: thinness of membrane & large surface area of glomerular capillaries glomerular capillary BP is high due to small size of efferent arteriole

30 Filtration Membrane #1 Stops all cells and platelets #2 Stops large plasma proteins #3 Stops medium-sized proteins, not small ones

31 Net Filtration Pressure NFP = total pressure that promotes filtration NFP = GBHP - (CHP + BCOP) = 10mm Hg

32 Histology Bowman's capsule Cells of the outer or parietal layer of Bowman's capsule form a simple squamous epithelium. Cells of the inner layer, podocytes in the visceral layer, are extremely complex in shape. Small footlike processes, pedicles, of their cytoplasm form a fenestrated epithelium around the fenestrated capillaries of the glomerulus.

33 The openings between the pedicles are called filtration slits. They are spanned by a thin membrane, the filtration slit membrane. Between the podocytes and the endothelial cells of the capillaries a comparatively thick basal lamina, which can be subdivided into an outer lamina externa, a middle lamina densa and an inner lamina interna. The basal lamina and the slit membranes form the glomerular filtration barrier, which prevents some large molecules from entering the capsular space between the outer and inner epithelial layers of Bowman's capsule. Mesangial cells in the glomerulus form the connective tissue that gives structural support to podocytes and vessels.

34

35

36

37

38

39

40

41

42

43

44

45 Histo: proximal tubule walls - low columnar epithelium. The eosinophilic cells of the epithelium have a wide brush border and are active in endocytosis.

46 Histo of Loop of Henle It is 'U' shaped and has descending and ascending segments. Thin descending segment has flattened epithelium( squamous). It is permeable to water but not solutes.

47 Histo: Distal convoluted tubule straight part of the DCT is formed by the low cuboidal cells without a brush border. The diameter of the tubule gradually expands to about 35 microns. convoluted part and comes in contact with the Glomerulus forming the Macula Densa.

48

49

50 Nephron structure characteristic Renal corpusle Capillary ball covered by podocyte & surrounded by simple squamous epithelial capsule, capsular space. Proximal convulated Lined with simple cubodial epithelium & prominent brush border Loop of Henle Tubule that form a loop, there are thick & thin ascending & desecnding portion; the most distal part of the loop often extends into the medulla. Thick limb are lined with simple squamous/ cuboidal epithelium Thin limb are lined with simple squamous epithelium Distal convulated Lined with simple cuboidal with only sparse brush border; cytoplasm of cells tend to be

51 Anatomy of Ureters 10 to 12 in long Varies in diameter from 1-10 mm Extends from renal pelvis to bladder Retroperitoneal Enters posterior wall of bladder Physiological valve only bladder wall compresses arterial opening as it expands during filling flow results from peristalsis, gravity & hydrostatic pressure

52 Ureter The wall of the ureter is made 3 layers. From inside outwards they are : 1. Mucosa- which is made up of epithelium & lamina propria 2. Muscular coat made of smooth muscles 3. Fibrosa made of fibrous connective tissue Mucosa- is thrown into folds and thus gives the appearance of star shaped lumen.

53 1. Transitional epithelium. 3-5 layers thickness. 2. Lamina propria- dense, irregular layer of fibroelastic connective tissue The epithelium is separated from the lamina propria by a basal lamina.

54 Muscular layer Upper 2/3 of the ureter is made of two layers of smooth muscle cells. Inner longitudinal and outer circular layer( in contrast to the wall of GIT which has inner circular & outer longitudinal!). Lower 1/3 of the ureter has a third outer layer of longitudinal muscles( inner longitudinal, middle circular, outer loingitudinal ). Fibrous coat is made up of fibrous connective tissue

55

56

57 The urethra: Female: relatively short, exits just anterior to the vagina Male: longer, divided into three sections the prostatic, membranous and spongy urethra. The prostatic urethra is enclosed in the prostate gland. The membranous urethra is a short section that penetrates the urogenital diaphragm. The spongy urethra or penile urethra extends from the membranous urethra to the external urethral orifice (meatus).

58 Histology: In both male and females the urethra starts out as transitional cell but quickly becomes stratified squamous in the female. The male urethra is more variable but ends up stratified squamous as well.

59

60 Histology of the bladder mucosa of transitional epithelium, Submucosa, and thick muscular layer know as the detrusor muscle

61

62

63 Clinical correlates Urinary incontinence Childbirth and other events can injure the scaffolding that helps support the bladder in women. Pelvic floor muscles, the vagina, and ligaments support your bladder. Specifically, the symptoms of overactive bladder include Overactive bladder urinary frequency bothersome urination eight or more times a day or two or more times at night urinary urgency the sudden, strong need to urinate immediately urge incontinence leakage or gushing of urine that follows a sudden, strong urge nocturia awaking at night to urinate