Urinary System mls

44
Urinary System Francis Ian L. Salaver, RMT

description

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Transcript of Urinary System mls

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Urinary System

Francis Ian L. Salaver, RMT

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Urinary System

Composed of the following organs: Paired Kidneys Ureters Urinary Bladder and; Urethra

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Function of the Kidneys

Regulation of water and electrolytes

Acid base balance Acidic blood= release hydrogen into urine Basic blood = release bicarbonate in the urine

Excretion of metabolic waste products through urine formation (including drug metabolites)

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Function of the Kidneys

Secretion of renin to increase blood pressure **

Secretion of erythropoietin Increases red cell production in the bone marrow

Activation of Vitamin D Gluconeogenesis

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Kidney

Has a concave medial border called HILUM where nerves enter and ureter exits; where blood and lymph vessels enter and exits.

Has a convex lateral side. Each side is covered by capsule

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Kidney

At the hilum, the ureter expands as the RENAL PELVIS and divides into 2-3 MAJOR CALYCES.

Smaller branches called MINOR CALYCES arise from the major calyces

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Kidney

Outer cortex and Inner Medulla Inner medulla contains 8-12 conical structures called

RENAL PYRAMIDS which are separated by the structure from the cortex called RENAL COLUMNS

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Kidney

Each pyramid and renal column along its side comprises one RENAL LOBE

Striations extending from the medulla into the cortex are called MEDULLARY RAYS

Tip of the pyramid that projects into the minor calyces are called RENAL PAPILLA

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Kidney

Functional unit: NEPHRONS

1 million in number Major divisions

Glomerulus Proximal Convoluted Tubule Loop of Henle

Descending limb Ascending limb

Distal Convoluted Tubule Connecting Tubule

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Nephron

Glomerulus/Renal Corpuscle = Dilated part; tuft of capillary loops and site of filtration

Proximal tubule – long convoluted tube; located on the cortex

Loop of Henle – Medulla

Distal tubule- ascending part from loop of Henle into the cortex

Connecting tubule – links nephrons to the collecting duct

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Cortical versus Juxtamedullary Nephrons

Longer loop of Henle???

Most abundant?

Found mostly on the cortex?medulla?

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Blood circulation of the Kidney

Renal artery

Segmental artery

Interlobar artery

Arcuate artery

Interlobular artery

Afferent arterioles

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Peritubular capillaries surround the proximal and distal tubules

Vasa recta surrounds the loop of Henle

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Nephron Function

Filtration Tubular Reabsorption Tubular Secretion

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Renal corpuscle and filtration

Contains tuft of capillaries surrounded by a doulbe-walled epithelial capsule called the Bowmans capsule. Has a vascular pole and tubular pole

Internal visceral layer closely envelops the capillaries

Outer parietal layer forms the capsule

Between the two layers is the capsular/urinary space

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Renal corpuscle and filtration

Outer layer of capsule is lined by simple squamous. At tubular pole, the lining epithelium changes to simple cuboidal.

Visceral layer forms the podocytes. From the body of the podocytes, several processes extend and curve around the capillary forming the pedicels with filtration slits in between them

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Slit diaphragm

Spans two adjacent pedicels and bridges slit pores

Modified tight junctions

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Process of filtration

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Proximal Convoluted Tubule

Starts from the tubular pole of the renal corpuscle

Lined by simple cuboidal epithelium

Fills up the cortex

Tubular reabsorption and secretion

Almost half of water, glucose, amino acids, vitamins and salts are reabsorbed back into the blood in the PCT

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Proximal Convoluted Tubule

Cells are well-stained; with numerous mitochondria, and long microvilli

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Loop of Henle

U-shaped structure with thin descending and ascending limb

Lined by simple squamous epithelium

Situated in the hyperosmolar medulla

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Countercurrent mechanism

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Distal convoluted tubule

Lined by simple cuboidal epithelim

Less absorption and secretion than in PCT

Cells are smaller and no microvilli (more nuclei can be seen)

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Macula Densa

Straight part of the DCT (macula densa) comes in contact with the arterioles at the vascular pole of the renal corpuscle (juxtaglomerular cells)

= JUXTAGLOMERULAR apparatus = RENIN

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Collecting Ducts

Each nephron has connecting tubules which carry filtrate into collecting ducts

Simple cuboidal epithelium

At the medulla, collecting ducts fuse to form ducts of Bellini which run to the tips of the

At the apex of the pyramid, the papillary duct is formed.

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Collecting Ducts

Principal cells = pale staining cells, few organelles, sparse microvilli and unusually distinct cell boundaries

Final site of water reabsorption

Responds to the ADH released from the posterior pituitary gland

Expresses aquaporin channels

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Collecting Ducts

Intercalated cells – darkly stained cells interspersed within principal cells

Secrete Hydrogen or Bicarbonate ions

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Ureter and Urinary Bladder

Transports urine from renal pelvis to the urinary bladder where urine is temporary stored.

Lined by Transitional epithelium or urothelium

• Single layer of basal cells

• Intermediate region of several or more columnar cells

• Superficial layer of bulbous cells called umbrella cells

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Tight Junction in umbrella cells

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Urethra

Tube that carries the urine from the urinary bladder to the exterior

In males, has three portion

1. Prostatic urethra

2. Membranous urethra

3. Spongy urethra

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