Urinary System

Question 1

Name the three functions of the urinary system?

Answer 1

1. Urine excretion
2. Endocrine organ
3. Homeostatic role (controls blood pressure, tissue osmolality, electrolyte and water balance and plasma pH

Question 2

How can the kidneys affect the pH balance

Answer 2

Excreting hydrogen ions in acidosis and bicarbonate ions in alkalosis

Question 3

How can the kidneys indirectly raise the blood pressure and drive red blood cell production?

Answer 3

They secrete renin which raises blood pressure and erythropoietin which accelerates red blood cell production

Question 4

What carries urine from the kidneys to bladder?

Answer 4

Ureters

Question 5

Describe the position of the kidneys

Answer 5

They are high up in the abdomen with one on each side. They sit inferior to the diaphragm and posterior to the abdominal wall (retroperitoneal).

Question 6

What protects the kidneys?

Answer 6

They are encapsulated by layers of fascia and firm renal fat.

Question 7

Describe the basic internal structure of the kidney

Answer 7

The outter portion of the kidney is called the cortex and this extends down between medullary pyramids. The pyramids project into a minor calyx (calyces for plural), these converge into major calyces which form the renal pelvis at the hilum. Pelvis becomes the ureter.

Question 8

What is the functional unit of the kidney?

Answer 8

A nephron

Question 9

Describe the basic structure of a nephron?

Answer 9

It consists of;
Renal corpuscle (glomerulus), this is where the blood supply comes in.  Then it moves into the proximal convoluted tubule. The loop of Henle which is closely related to circulation which is important when determining the concentration of urine. The distal convoluted tubule which them moves into a Collecting duct (where a number of nephrons merge together).

Question 10

Where are nephrons located?

Answer 10

In the medullary pyramid

Question 11

How does the structure of the collecting duct change?

Answer 11

It increases in size

Question 12

Name the two different types of nephrons and describe them.

Answer 12

Juxtamedullary nephron, ( located in the inner cortex, this is designed to concentrate urine and has long nephron loops). And the superficial nephron (located in outter cortex, they reabsorb a large volume of fluid that is filtered from vasculature and they have short nephron loops)

Question 13

Describe the general located of the ureter in females

Answer 13

Females - posterior to overy, lateral to cervix and anterior to the womb.

Question 14

Describe the basic structure of the ureter

Answer 14

It is muscular and uses peristaltic waves to propel urine downwards. It also contains a one-way valve to prevent urine reflux into the ureter once in the bladder.

Question 15

Describe the basic structure of the bladder.

Answer 15

It is made of smooth muscle and is filled by relaxation of its muscular wall (the detrusor muscle) and is emptied by the contraction of the detrusor muscle, this is aided by raising intra-abdominal pressure. Lines by urothelium (transition epithelium) These cells are rounded and stratified.

Question 16

What is the glomerulus?

Answer 16

It is a cluster of capillaries where filtration occurs.

Question 17

Give an overview of the filtration process

Answer 17

Blood enters the glomerulus where is is filtered, the hydrostatic pressure forces out the ultrafiltrate. The endothelium is fenestrated which allows the passage of materials and they pass through podocyte foot processes into the bowman capsule.

Question 18

GIve an overview of the reabsorption process.

Answer 18

Sodium ptassium-ATPase creates a sodium gradient and provides energy for transportation. Ion transport creates a voltage gradient between the tubule lumen and interstitium which allows for more movement of substances across the membrane. Water follows sodium and is reabsorbed by osmosis. Solvent drag means solutes are carried along in the water flow. A concentrated of solutes is left in the lumen after water reabsorption.

Question 19

The excretion of the nephron consists of what?

Answer 19

What is filtered out of the blood and whats secreted into the collecting ducts but minus what is reabsorbed.

Question 20

How does the osmolality change in the kidney?

Answer 20

It ranges from relatively low osmolality from the cortex and outer medulla to high osmolality in the inner medulla (where the loops of henle are located)

Question 21

Describe how water is reabsorbed

Answer 21

As filtrate comes down from the proximal tubule, water is exposed to high osmolality and is driven out due to the osmotic pressure gradient.

Question 22

Describe what prevents water from being reabsorbed by the nephron

Answer 22

The impermeability of the ascending limb of the loop prevents water from reentering and diluting its contents. Dilution would collapse the gradient that drives sodium diffusion out of the nephron.

Question 23

Describe some of the features proximal tubule epithelium?

Answer 23

They have apical microvilli which increases surface area and have junctions between cells are leaky so they maximise free flow of water and dissolved solutes

Question 24

What is reabsorbed water returned too?

Answer 24

Vasculature via the peritubular network

Question 25

What controls the outflow of urine via the urethra and what are they controlled by?

Answer 25

Inner and outer sphincters. The inner sphincter and bladder contraction is controlled by spinal reflexes and the CNS. The outer sphincter is under voluntary control.

Question 26

What does filling of the bladder cause?

Answer 26

The muscular wall to stretch which initiates a spinal micturition reflex. The reflex causes the parasympathetic motor efferents to stimulate bladder contraction

Question 27

What prevents you from urinating?

Answer 27

The central nervous system. It will only empty when the outer sphincter is voluntarily relaxes.