Urinary System - Unit 4

Question 1

What are the functions of the Kidneys?

Answer 1

• Elimination of metabolic waste products
• Regulation of ion levels
• Regulation of the acid-base balance
• Regulation of blood pressure
• Elimination of biologically active molecules

Question 2

Explain the Filtration step of urine production.

Answer 2

Filtration (glomerular filtration) happens first.
- Water and other small dissolved molecules are passively removed from blood plasma within the glomerulus
- Froms a fluid called filtrate

Question 3

Explain the Tubular Reabsorption step of urine production.

Answer 3

About 99% of filtered substances are quickly returned to the blood by membrane transport processes from the lumen of the renal tubules and collecting ducts

Question 4

Explain the Tubular Secretion step of urine production.

Answer 4

Movement of solutes moves, by active transport, out of the blood into the tubular fluid. Materials are moved selectively to be excreted from the body.

Question 5

Explain the structure of the Filtration Membrane.

Answer 5

A filtration membrane is a porous thin, negatively charged structure. It has 3 layers:
1. Fenestrated endothelium of glomerular. capillaries
2. Basement membrane of glomerulus
3. Filtration slits formed by podocytes of the visceral layer of Bowman’s capsule.

Question 6

How is filtration formation formed?

Answer 6

Filtrate is formed due to differences in hydrostatic pressure of the blood in the glomerulus and the opposing pressures of both osmotic blood pressure and fluid pressure in the capsular space of the renal corpuscle

Question 7

What is Glomerular Capillary Pressure (GCP)?

Answer 7

Driving forces that pushes water and some dissolved solutes out of the glomerulus and into the capsular space of the renal corpuscle. Outward pressure (promotes filtration).

(blood pressure)

Question 8

What is Capsular Hydrostatic Pressure (CHP)?

Answer 8

Pressure in the capsular space due to the amount of filtrate already in the lumen of Bowman’s capsule. Inward pressure (opposes filtration).

Question 9

What is Blood Colloid Osmotic Pressure (BCOP)?

Answer 9

Osmotic pressure caused by proteins in the blood. Tends to pull fluids into the glomerulus. Inward pressure (opposes filtration).

Question 10

What substances are not normal components in urine? What substances have regulated reabsorption in urine?

Answer 10

Some substances are not normal components in the
urine because 100% of the substance is reabsorbed.
- Nutrients and small plasma proteins

Some substances have regulated reabsorption,
meaning that not all of the substance is reabsorbed.
- Na+, K+, Ca2+

Question 11

Explain the cells of tubule walls.

Answer 11

Each cell has:
– Apical surface: surface that faces filtrate. Apical membrane
– Basal surface: faces interstitial fluid. Basal
membrane
– Lateral surfaces: surfaces between cells

Question 12

Explain Tubular Reabsorption.

Answer 12

Typically occurs in the proximal convoluted tubule. Substances are transported from the tubular lumen into the interstitial fluid and then into the peritubular capillaries.

• Active transport of Na+ across the basal membrane from the tubule cell to interstitial fluid linked to reabsorption of most solutes.
  -Because of this active transport, the concentration of Na+ is low inside the cell and Na+ moves into the nephron cell from filtrate through the apical membrane.
• Other substances, moved by symport, from the filtrate into the nephron cells are substances that should be retained by the body.

Question 13

Explain the Loop of Henle.

Answer 13

The loop of henle descends into the medulla; interstitial fluid is high in solutes. It has 2 portions.

• The descending thin segment is highly permeable to water and moderately permeable to most other solutes.
• The ascending thin segment is not permeable to water but is to solutes

Question 13

Explain Tubular Secretion.

Answer 13

It moves non-filtered substances, metabolic waste, drugs, and hormones from the blood into the tubule of the nephron.
- Usually active transport processes

Question 13

What is the Micturition Reflex?

Answer 13

It’s the elimination of urine from the urinary bladder. It’s activated when the urinary bladder is stretched.

• Stretching activates stretch receptors which send action potentials to the spinal cord.
• The spinal cord sends action potentials to the urinary bladder causing detrusor muscles (smooth muscle) to contract and relax the internal urethral sphincter.
• Urine will flow from the urinary bladder through the urethra.
• Voluntary initiation requires action potentials to be sent to “turn on” reflex and relax the external urinary sphincter.

Question 13

Explain urine movement after the production of urine.

Answer 13

After urine is formed hydrostatic pressure forces urine through the nephron.

Peristalsis moves urine through the ureters from regions of the renal pelvis to the urinary bladder.
- Parasympathetic stimulation: increases frequency
- Sympathetic stimulation: decreases frequency

Ureters enter the bladder obliquely through the trigone. Pressure in the bladder compresses the ureter and prevents backflow.

Question 13

Explain the Urinary Bladder.

Answer 13

The urinary bladder acts as a reservoir for urine until it
can be eliminated at the appropriate time/place. (Storage container)
- Max = 1L of urine
- Urge = 200mL
- Discomfort = 500mL