Urinary System-Anatomy and Physiology

Zoe McCarthy

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Urinary System in Context

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Urinary System in Context

System How does it do it?

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Functions of the Urinary system• 1. Regulating blood volume and pressure

• 2. Regulating plasma concentrations of sodium, potassium, chloride and other ions

• 3. Stabilising blood pH

• 4. Conserving nutrients

• 5. Detoxifying poisons (with the liver)

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Organisation of the Urinary System

• Kidneys• Ureters• Urinary bladder• Urethra

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Position of the KidneysCT abdomen with contrast MRI coronal abdomen

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Protection of the Kidneys

• 3 layers of connective tissue:– Inner layer- Renal capsule

– Middle layer- Adipose capsule

– Outer layer-Renal fascia

Renal cortex

Retroperitoneal space

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Surface anatomy of the Kidney

• Hilum is located on the medial surface

10 cm

5.5cm

3cm

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Internal Structure of the Kidney

Renal pyramids

Renal papilla

Renal Columns

Renal Lobe

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Microscopic structure of the Kidney and Urine Production

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Renal Corpuscle and Filtration

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Nephron-Tubular System1. Proximal convoluted

tubule

2. Descending loop of Henle

3. Ascending loop of Henle

4. Distal convoluted tubule

5. Collecting duct

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Summary so far…..Blood enters the kidney through the renal artery at the site of the hilum

The renal artery divides in to ever smaller arteries and arterioles

Afferent arterioles take blood to the glomerulus to be filtered

Once blood is filtered efferent arterioles take blood away from the glomerulus

The glomerulus is a network of capillaries which filters the blood

Products which are filtered out: water, mineral salts, amino acids, glucose, hormones, urea, toxins

Products which do not filter and remain in the blood: Leukocytes, erythrocytes, platelets, plasma proteins

The filtered substances move into the proximal convoluted tubule

The PCT is concerned with reabsorption- organic nutrients are reabsorbed and water follows because there is a concentration gradient

The remaining filtrate moves into the descending loop of henle. This is lined with thin cells so water moves out

Because water has been reabsorbed the concentration of the filtrate is not very high

The walls of the ascending loop of henle are lined with thicker cells, so water can’t pass in or out. Instead sodium and chloride is pumped out actively

The filtrate now enters the distal convoluted tubule- is it now only 20% of what it originally was.In the DCT the volume and

composition of the filtrate can be adjusted but this is controlled by hormones

From the DCT the filtrate now passes into the collecting duct.

A number of other nephrons join up to the cleectig duct which travels through the medulla to the renal papilla wher the filtrate is emptied in the minor calyx

4-5 minor calyces join up to make a major calyx

2-3 major calyces join up to form the renal pelvis The renal pelvis joins the

ureter at the hilumThe ureter transport the filtrate/urine from the kidney to the bladder

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The Formation of Urine

• 3 processes involved in the formation of urine.

– Simple filtration– Selective reabsorbtion

• Hormonal control-» Parathyroid hormone, calcitonin» Anti diuretic hormone» Aldosterone

– Secretion

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Ureters• Superiorly

• Continuous with the renal pelvis

• Inferiorly• Pass through the abdominal

cavity, behind the peritoneum, infront of the psoas muscle, into the pelvic cavity ehere they enter the posterior wall of the bladder

• 25-30 cm in length

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Ureter- Cross Section

• 3 layers of tissue

– Outer layer• Fibrous tissue

– Middle layer• Muscle

– Inner layer• Epithelium

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Bladder

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Bladder- structure of

• 3 layers– Outer layer

• Loose connective tissue

– Middle layer• Smooth muscle and

elastic fibres

– Inner layer• Lined with transitional

epithelium

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Urethra• Extends from the

base of the bladder to the outside world.

• Anatomical differences mean that male and female urethras are different.– Female: 4cm long– Male: 14cm

long

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Urethra- structure of

• Muscle layer

• Submucosa layer

• Mucosa

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