Lecture 25: Urinary System Anatomy

Question 1

What are the functions of the urinary system?

Answer 1

1. Regulate water and solute balance within the body.
2. Regulate ion concentrations in the ECF.
3. Maintain pH
4. Excretion of wastes
5. Convert vitamin D into its active form
6. Regulate erythropoiesis by making and releasing the erythropoietin hormone.
7. Regulate blood pressure

Question 2

How do kidneys maintain pH?

Answer 2

Kidneys can adjust blood pH by excreting various levels of hydrogen ad bicarbonate ions.

Question 3

What are some wastes which the kidneys excrete?

Answer 3

1. Metabolic wastes (Urea, Uric acid and Creatinine)
2. Toxins
3. Drugs

Question 4

Where are the kidneys located and how are they protected?

Answer 4

The kidneys are located in the superior lumbar region of the abdominal cavity. The right kidney is slightly inferior to the left due to presence of liver. The adipose tissue protects the kidneys.

Question 5

What is the hilum?

Answer 5

It is where the renal artery, vein and ureter come in and out.

Question 6

Which are the three distinct regions of a kidney?

Answer 6

1. Renal Cortex
2. Renal Medulla
3. Renal Pelvis

Question 7

What is the function of the renal cortex?

Answer 7

Filters the blood with the help of nephrons. (Remove waste, extra water and harmful substances from the blood)

Question 8

What is the renal medulla composed of?

Answer 8

Made up of renal pyramids containing urine collecting ducts which receive urine from the nephrons.
Urine is delivered from each pyramid through its papilla to the renal pelvis.

Question 9

What is the renal pelvis composed of?

Answer 9

Includes calyces; cup shaped areas that enclose the papillae to catch urine and empty it into the renal pelvis. The renal pelvis is continuous with the ureter leaving the kidney.

Question 10

What are the two parts of the nephron and their functions?

Answer 10

1. Renal Corpuscle: Consists of a glomerulus (tiny ball of blood vessels) where blood is filtered and bowman’s capsule (a cup shaped structure which captures the filtered fluid).
2. Renal Tubule: Along the way, the body reabsorbs what it still needs while wastes are turned into urine.

Question 11

What are the functions of a nephron?

Answer 11

1. Filtration
2. Reabsorption
3. Secretion

Question 12

How does the glomerulus filter blood?

Answer 12

Blood is fed into the glomerulus through afferent arteriole and empties into an efferent arteriole. The efferent arteriole is smaller in diameter than afferent. As a result, hydrostatic pressure allows for greater filtration to occur.

Question 13

What are podocytes and their function?

Answer 13

Podocytes cling to the surface of glomerulus. They create tiny gaps called filtration slits which allow for water and small molecules to pass through.

Question 14

Which are the three layers that make up the filtration membrane?

Answer 14

1. Fenestrated capillary endothelium
2. Basement membrane
3. Foot processes of podocytes of the glomerular capsule.

Question 15

What are the three regions to the renal tubule?

Answer 15

1. Proximal convoluted tubule
2. Loop of Henle (descending and ascending limbs)
3. Distal convoluted tubule

Question 16

What is the function of proximal convoluted tubule?

Answer 16

Confined to the renal cortex.
Main region of reabsorption and wall made up of cuboidal cells with dense microvilli.

Question 17

What is the function of Loop of Henle?

Answer 17

Descending limb: Reabsorption of water
Ascending limb: Reabsorption of ions

Question 18

What is the function of distal convoluted tubule?

Answer 18

Hormones mediates reabsorption of sodium and calcium ions and secretion of potassium ions.

Question 19

What is the function of collecting ducts?

Answer 19

Receive filtrate from many nephrons and deliver urine through papillae of pyramids into the renal pelvis.

Question 20

Outline the pathway in urine formation.

Answer 20

Renal corpuscle
Proximal convoluted tubule
Descending loop of Henle
Ascending loop of Henle
Distal convoluted tubule
Collecting duct (travels through renal pyramids)
Renal pelvis
Ureter

Question 21

What are kidney stones?

Answer 21

Calcium phosphate or calcium oxalate crystals form within the kidney.

Question 22

Which are the two locations for blood nephron interface?

Answer 22

1. Glomerulus: Filtrate is forced out of the glomerular capillaries into the capsule.
2. Exchange between filtrate in renal tubule and blood in peritubular capillaries.

Question 23

Which two sphincters control micturition?

Answer 23

1. Internal sphincter (Smooth muscle under involuntary control)
2. External sphincter (Skeletal muscle under voluntary control)

Question 24

Describe the micturition reflex?

Answer 24

Stretch receptors in the wall of the bladder send impulses to the Micturition reflex center in the sacral region of the spinal cord.
Through parasympathetic pathways the smooth muscle in the wall of the bladder is stimulated to contract putting pressure on the internal sphincter.
Urine forces through the internal sphincter and enters the superior aspect of the urethra. This is when we become aware of the urge to urinate.