Urinary system

Question 1

What are the functions of the urinary system?

Answer 1

Regulate the blood volume and composition.
Regulate Blood Pressure
Storage as well as excretion of waste product via urine

Question 2

what are the main functions of the kidneys?

Answer 2

Formation of urine, maintaining water, electrolyte and acid-base balance
excretion of waste products
production and secretion of erythropoietin, the hormone which stimulates formation of red blood cells

Question 3

Where do the kidneys lie?

Answer 3

on the posterior abdominal wall, one on each side of the vertebral column, behind the peritoneum and below the diaphragm.
Extend from the level of the 12th Thoracic vertebra to the 3rd lumbar vertebra.
The right kidney is normally slightly lower than the left, due to the space occupied by the liver.

Question 4

What are the different tissue layers of the kidney?

Answer 4

An outer, fibrous capsule, surrounding the kidney.
The cortex, a reddish-brown layer of tissue immediately below the capsule and surrounding the renal pyramids.
The medulla, the innermost layer, consisting of pale, conical-shaped, striated structures, the renal pyramids. Each pyramid has a pointed end called the papilla.

Question 5

What is the hilum of the kidney?

Answer 5

The concave medial border of the kidney, where the renal blood and lymph vessels, the ureter and the nerves enter.

Question 6

How does urine exit the kidneys?

Answer 6

It passes through a renal papilla into the drainage system that begins at a minor calyx, several of which will merge into a major calyx, and again, several will combine forming the renal pelvis.
The renal pelvis is a hollow funnel-shaped structure that narrows when it leaves the kidney as the ureter. The ureter leads to the bladder.

Question 7

What are the walls of the calyces and renal pelvis lined with?

Answer 7

Transitional epithelium and contains smooth muscle.

Question 8

How is urine propelled through the calyces, renal pelvis and ureters?

Answer 8

Peristalsis, the intrinsic contraction of smooth muscle.

Question 9

What do nephrons consist of?

Answer 9

Glomerular capsule (bowman’s capsule) which almost completely encapsules a bundle of capillaries called the
Glomerulus
Proximal convoluted tubule
The medullary loop (loop of Henle)
Distal convoluted tubule leading to the
collecting duct
The collecting ducts merge, forming larger ducts which empty into the minor calyces.

Question 10

How does blood flow around the kidneys?

Answer 10

The renal artery enters the kidney at the hilum. It then divides into smaller arteries and arterioles.
An afferent arteriole enters each glomerular capsule and then subdivides into a cluster of tiny arterial capillaries, forming the glomerulus. The blood vessel leading away from the glomerulus is the efferent arteriole.

Question 11

What drives filtration in the nephrons?

Answer 11

The afferent arteriole has a larger diameter than the efferent arteriole, increasing the pressure inside the glomerulus and drives filtration across the glomerular capillary walls.

Question 12

What are the walls of the glomerulus and glomerular capsule made of?
What are the walls of the rest of the nephron made of?

Answer 12

A single layer of flattened epithelial cells. They are very permeable to facilitate filtration.
The walls of the remainder of the nephron and the collecting duct are formed by a single layer of simple squamous epithelium.

Question 13

What are the 3 processes in the formation of urine?

Answer 13

Filtration, selective reabsorption, secretion

Question 14

Where does filtration take place?
What happens?

Answer 14

The semipermeable walls of the glomerulus and the glomerular capsule.
Water and other small molecules readily pass through, although some are reabsorbed later. Blood cells, plasma proteins and other large molecules are too large to filter through and therefore remain in the capillaries.

Question 15

What is the glomerular filtration rate?

Answer 15

the volume of filtrate formed by both kidneys each minute. In a healthy adult, it’s about 125ml/min.
Nearly all filtrate from the kidneys is reabsorbed, with less than 1% excreted as urine.

Question 16

What is autoregulation?

Answer 16

The mechanism protecting renal blood flow from fluctuations in blood pressure.
This system fails when systolic blood pressure falls below 80mmHg.

Question 17

Where does most selective reabsorption take place?

Answer 17

Proximal convoluted duct. The epithelial lining of which possesses microvilli to aid reabsorption. Water, electrolytes, glucose and amino acids are reabsorbed here.

Question 18

Which hormones influence calcium reabsorption?

Answer 18

Parathyroid hormone - regulates the reabsorption of calcium and phosphate so that normal blood levels are maintained. Parathyroid hormone increases blood calcium levels and calcitonin lowers it.

Question 19

Which hormone influences water reabsorption?

Answer 19

Antidiuretic hormone increases the permeability of the distal convoluted tubule, increasing water reabsorption. Osmoreceptors in the hypothalamus monitor water levels in the blood and ADH secretion is adjusted accordingly.

Question 20

What does aldosterone do?

Answer 20

Secreted by the adrenal cortex, it increases the reabsorption of sodium and water, and the excretion of potassium.

Question 21

Which hormone decreases reabsorption of sodium and water?

Answer 21

Atrial natriuretic hormone is produced by the atria of the heart in response to stretching of the atrial wall when blood volume is increased.

Question 22

What is tubular secretion?

Answer 22

Substances that have not been entirely filtered out of the blood due to size or the short time they remain in the glomerulus are secreted into the filtrate within convoluted tubules. The secretion of hydrogen ions is important in maintaining normal blood ph.

Question 23

Why is urine amber in colour?

Answer 23

Due to the presence of urobilin.

Question 24

What is excreted in urine?

Answer 24

water (95%)
urea (2%)
uric acid
creatinine
ammonia
sodium
potassium
chlorides
phosphates
sulphates
oxalates

Question 25

What does the renin-angiotensin-aldosterone system regulate?

Answer 25

Electrolyte balance as a way to control blood pressure.

Question 26

How is pH balance regulated?

Answer 26

proximal convoluted tubules secrete hydrogen ions into the filtrate, where they combine with buffers. carbonic acid is converted to carbon dioxide and water.
Hydrogen ions are excreted in urine as ammonia salts and hydrogen phosphate.

Question 27

What is the structure of ureters?

Answer 27

They have an outer covering of fibrous connective tissue continuous with the capsule of the kidney.
A middle muscular layer consisting of interlacing smooth muscle fibres that form a functional unit around the ureter and an additional outer longitudinal layer in the lower third.
An inner layer called the mucosa, composed of transitional epithelium.

Question 28

What is the structure of the bladder?

Answer 28

Has an outer layer of loose connective tissue, containing blood and lymphatic vessels and nerves, covered on the upper surface by the peritoneum.
The middle layer, consisting of interlacing smooth muscle fibres and elastic tissue loosely arranged in 3 layers. called the detrusor muscle, and when it contracts, it empties the bladder.
the inner mucosa, composed of transitional epithelium, permits distension of the bladder as it fills.
When the bladder is empty, the inner lining is arranged in rugae (folds) which dissapear as it fills.

Question 29

What controls the outflow of urine from the bladder?

Answer 29

The internal urethral sphincter controls the outflow of urine from the bladder. This is a thickening of the urethral smooth muscle layer in the upper part of the urethra. This sphincter is not under voluntary control.

Question 30

What is the external urethral orifice?

Answer 30

Where the female urethra exits the body. It is guarded by the external urethral sphincter, which is under voluntary control.

Question 31

What is the structure of the female urethra?

Answer 31

It has 2 main layers: an outer muscle layer and an inner lining of mucosa, which is continuous with that of the bladder.
The muscle layer has two parts- an inner layer of smooth muscle that is under autonomic nerve control, and an outer layer of striated muscle surrounding it. The straited muscle forms the external urethral sphincter and is under voluntary control.
The mucosa is supported by loose fibroelastic connective tissue containing blood vessels and nerves.

Question 32

How does micturition occur?

Answer 32

Accumulation of urine in the bladder activates stretch receptors in the bladder wall, which generates a sensory impulse transmitted to the spinal cord and brain. Contraction of the external urethral sphincter and muscles of the pelvic floor can inhibit micturition until it is convenient.