Exercise 26

Functional Anatomy of The Urinary System

Renal capsulea tough fibrous layer surrounding the kidney and covered in a thick layer of adipose tissue. It provides some protection from trauma and damage.

Gross Anatomy of the Human Urinary System

Organs of the Urinary System

Figure 15.1a

• Kidneys• Ureters• Urinary

bladder• Urethra• Renal Artery

Urinary System Organs

Function

Kidneys • Maintains water and electrolyte balance of the blood

• Produces urine

Ureters • Transports urine to urinary bladder

Urinary bladder • Serves as a storage area for urine

Urethra • Transports urine to the body’s exterior• Is shorter in women than in men

Renal Artery • Transports arterial blood to the kidney

Internal Anatomy of the Kidney

Renal cortex —outer region; contains most of nephron structureRenal medulla —inside the cortex; contains inner collecting ductsRenal pelvis – basin continuous with ureterRenal columns —extensions of cortex-like material inward that separate the pyramidsCalyces —cup-shaped structures, extensions of pelvis that funnel urine Renal or fibrous capsule -- a tough fibrous layer surrounding the kidney

Internal Anatomy of the Kidney

Functional Microscopic Anatomy of the Kidney

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Glomerulus= site of filtrate formationRed arrows = BloodBlue arrows = Filtrate

Glomerulus = a tiny ball-shaped structure composed of capillary blood vessels actively involved in the filtration of the blood to form urine .

Bowman’s Capsule =Fluids from blood in the glomerulus are collected in the Bowman's capsule (i.e., glomerular filtrate) and further processed along the nephron to form urine.

Proximal convoluted tubule= primary site of tubular reabsorption

Glucose, Amino Acids, Na+, and Water are being reabsorbed by the Proximal Convoluted Tubule

Collecting Ducts- collects the urine from the nephron and send it to the ureter.

Peritubular capillaries – receives substances from the tubular cells

Bowman’s Capsule: the inner membrane forms part of the filtration mechanism

• There are two layers of cells that fluid (with its contents) has to pass through during filtration.

The first layer is the endothelium of the glomerular capillary.

The second layer is the visceral layer of the Bowman’s capsule, formed by podocytes

• The renal corpuscle is where plasma is filtered from capillaries into the renal tubules. At the center of renal corpuscle is the glomerulus, a meshwork of capillaries. The glomerulus is surrounded by Bowman's capsule

Glomerulus and Bowman’s Capsule

Visceral layer

Parietal layer

Podocytes make up the visceral layer of Bowman’s Capsule

Glomerulus is a high-pressure capillary bedThe afferent arteriole feeding the glomerulus is is larger than the efferent arteriole which drains the arteriole

The high pressure forces out fluid and blood components smaller than proteins from the glomerulus into the glomerular capsule

Proximal Convoluted Tubule The cuboidal cells of the proximal convoluted tubule have long microvilli (brush border) on their inside surface that dramatically increase the surface area for reabsorption from the filtrate.

What is the purpose of this brush border epithelium?

Filtrate

Close up of brush border (microvilli)

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Glomerular capsuleProximal convoluted tubuleLoop of HenleDistal convoluted tubuleCollecting duct

Nephron in Cortex

Renal CortexMedullary pyramidCalycesRenal pelvis

This is a low power view of a cross section through the kidney. Note the inner medullary tissue (green) surrounded by the outer cortical tissue (blue)

Kidney

CortexIdentify a glomerulus, which appears as a ball of tightly packed material containing many small nuclei

Notice the vacant appearing region corresponding to the glomerular capsule that surrounds it.

The balance of the kidney tissue consists of renal tubules.

Loop of Henle

(D) Descending limbs of the loop of Henle look similar to the proximal tubule, with apical brush borders. (Blue)(A) Ascending limbs are composed of cuboidal cells, but unlike the proximal convoluted tubule, they do not have apical brush borders. (Green)(C) Collecting ducts can also be seen on this slide. They can be easily distinguished by the presence of prominent lateral borders between adjacent cells. (Orange)

Loop of Henle

• Descending limb, with its brush border similar to that of the proximal tubule. (Blue)• Ascending limb lacks this brush border and its cells have a more squamous

appearance. (Red)• Collecting duct can be observed. (Purple)

Renal Pelvis

Urine in the collecting ducts eventually empties into the renal pelvis.

Renal pelvis is the initial dilated portion of ureter.

Ureter

Urinary Bladder

Compare the transitional epithelium between a relaxed bladder and a distended bladder.

The urinary bladder is lined by transitional epithelium, underneath which are thick layers of smooth muscle interwoven in various directions.

Urethra