urinary system part 1

Question 1

what are the functions of the kidneys?

Answer 1

 Regulate Blood composition:

• Water Balance
• Ion Balance
• Waste Removal
• Maintain acid/base Balance

 Regulate Blood Pressure

 Stimulate red blood cell production

 Maintain Calcium levels (PTH reduces loss of calcium from primitive urine)

Question 2

what is the Renal capsule?

Answer 2

◦ Renal capsule: fibrous connective tissue. Surrounds each kidney

Question 3

what is the Perirenal fat?

Answer 3

◦ Perirenal fat

 Engulfs renal capsule and acts as cushioning

Question 4

what is the Renal fascia?

Answer 4

◦ Renal fascia: thin layer loose connective tissue
 Anchors kidneys and
surrounding adipose to
abdominal wall

Question 5

what is the Hilum

Answer 5

◦ Hilum

 Renal artery and nerves enter and renal vein and ureter exit kidneys

Question 6

where are the locations of the kidneys?

Answer 6

◦ Lie behind peritoneum
(retroperitoneal) on posterior
abdominal wall on either side of vertebral column

◦ Lumbar vertebrae and rib
cage partially protect

◦ Right kidney slightly lower
than left

Question 7

internal anatomy of the kidneys that we need to know-cortex?

Answer 7

 Cortex: outer area

◦ Renal columns: part of cortical tissue that extends into medulla

Question 8

internal anatomy of the kidneys that we need to know-Medulla?

Answer 8

 Medulla: inner area;

surrounds renal sinus

Question 9

internal anatomy of the kidneys that we need to know-Ureter?

Answer 9

 Ureter: exits at the hilum;

connects to urinary bladder

Question 10

what are the characteristics of a Nephron?

Answer 10

 Functional Unit of the Kidney.

 1 Million in each kidney.

 Unique blood supply

 2 capillary beds in series, connect arteries to
veins.

 Structure is important in maintaining constant
blood pressure.

Question 11

what is the anatomy of a Nephron

Answer 11

 Bowman’s capsule

 Glomerulus: network
of capillaries. Blood
enters through
afferent arteriole,
exits through efferent
arteriole.

Question 12

what is Glomerular filtration?

Answer 12

Glomerular Filtration:

◦ Filtering of blood into tubule forming the primitive urine

Question 13

what is Tubular Reabsorption?

Answer 13

Tubular Reabsorption:

◦ Absorption of substances needed by body from tubule to blood

Question 14

what is Tubular Secretion?

Answer 14

Tubular Secretion:

◦ Secretion of substances to be eliminated from the body
into the tubule from the blood

Question 15

part 1: Glomerular filtration

Answer 15

 Approximately 20% of blood is filtered under
pressure through walls of Glomerular capillaries
and Bowman’s Capsule.

 180 litres per day

 Entire plasma volume filtered up to 60 times per
day.

 Once filtrate has entered Bowman’s capsule it
flows through the lumen of the nephron into the
proximal tubules.

Question 16

part 2: Tubular reabsorption

Answer 16

 Once inside lumen of nephron small molecules
are reabsorbed from filtrate.

 Specialised proteins located on cell membranes
of nephron transport molecules.

 Either active or passive transport.

 Water is reabsorbed passively by osmosis in
response to high concentration of sodium
reabsorption.

 Solvent Drag – Small molecules transported by
the drag of water.

Question 17

sodium Reabsorption, % of reabsorption at different parts of the kidneys

Answer 17

 Proximal Tube – reabsorbs 65% of filtered
sodium.

 Loop of Henle – reabsorbs 25%

 Distal Tubule – reabsorbs 8%

 Collecting duct – reabsorbs 2% in presence of Aldosterone.

Question 18

Hormonal mechanisms-ADH:

Answer 18

• Secreted by the posterior pituitary gland.
• Controls permeability of cell walls in distal tubule
  and collecting duct.
• Osmoreceptors(senses change in sodium in blood) in hypothalamus sense changes in sodium concentration in blood and secrete ADH accordingly.
• ↑ ADH - ↑ permeability - ↓Urine volume.
• ↓ ADH - ↓ permeability - ↑Urine volume.
• Negative feedback.

Question 19

Roles of ADH in regulating urine concentration and volume

Answer 19

1. concentration of water in blood decreases.
2. increases in osmotic pressure of the body fluids stimulates osmoreceptors in hypothalamus in brain
3. hypothalamus signals posterior pituitary to releases ADH.
4. Blood carries ADH to kidneys
5. ADH causes distal convoluted tubules and collecting ducts to increase water reabsorption
6. urine concentrates, and urine volume decreases

Question 20

Renin-Angiotensin-Aldosterone

Answer 20

 Renin secretion ↑ with ↓ in Bp or ↓ in sodium
concentration.

 Renin enters circulation: angiotensinogen -
angiotensin I – (ACE (ACE inhibitors are used to treat high blood pressure)) – angiotensin II.

 Angiotensin II:
- Increases peripheral resistance (constricts
blood vessels)
- Increases ADH secretion.
- Sensation of thirst
- Increases aldosterone secretion.

Question 21

Aldosterone characteristics and functions

Answer 21

 Steroid hormone.

 Increases reabsorption of sodium from filtrate.

 More sodium in blood leads to concentration
gradient. Water moves back into blood by osmosis.

 Decreased urine volume.

Question 22

Tubular load characteristics?

Answer 22

 Total amount of a substance filtered into
nephron each minute.

 Glucose – normally completely reabsorbed by
active transport.

 If tubular load exceeds capacity for reabsorption
then excess glucose will remain in urine.

 Tubular maximum – maximum rate at which a
substance can be reabsorbed.

Question 23

Tubular secretion characteristics?

Answer 23

 Movement of some substances which may be
harmful to the body into the nephron.

 By-products of metabolism (Hydrogen).

 Drugs or molecules not normally produced by
the body (Penicillin).

 Can be either active or passive transport.