Introduction to the kidney and renal function

Question 1

What are the 2 functions of the urinary system?

Answer 1

1. Excretion

The removal of organic waste

products from body fluids

2. Elimination

The discharge of waste products

into the environment

Question 2

List the essential renal functions

Answer 2

Question 3

What is the consequence of renal dysfunction?

Answer 3

Question 4

How can renal dysfunction kill you?

Answer 4

Renal function is essential for survival… renal failure, if severe and untreated, leads to death

This failure may be rapid:

acute kidney injury (AKI)

about 10% of renal failure

or it may take many months or, more typically, years to develop:

chronic kidney disease (CKD)

about 90% of renal failure

Question 5

What is the treatment for renal failure?

Answer 5

Ultimately, renal function must be supplemented artificially, either by dialysis or by a transplanted kidney

Question 6

Where are the kidneys situated?

Answer 6

Paired organs situated«

on posterior (back) wall of abdomen

behind the peritoneum

on either side of the vertebral column

Question 7

What are the measurements of a kidney?

Answer 7

Each kidney: 120-170 g (adult human)

Approx: 11 cm long, 6 cm wide, 3 cm thick

Question 8

What is the renal hilum?

Answer 8

Where each kidney is joined at medial side to renal artery and vein, nerves and ureter

Question 9

What are the 2 layers of the kidney and what do they contain?

Answer 9

Cortex (outer layer) - composed of ~ 1.25 million nephrons

Medulla (inner layer) - pyramids drain into pelvis which drain into ureters

Question 11

What is a nephron?

Answer 11

A nephron is the “functional unit” of the kidney responsible for urine formation and composition

Question 12

Why does GFR decrease with age?

Answer 12

Approximately 1.25 million nephrons per human kidney…

but numbers (and therefore renal function) decline with age

(10,000 nephrons lost per year from about 50 years, GFR 50 % of normal adult rate by age 75)

Question 13

What are the 5 sections of the nephron?

Answer 13

Glomerulus (Renal corpuscle)

Proximal tubule (PT)

Loop of Henle (LOH)

Distal tubule (DT)

Collecting duct (CD)

Question 14

Label the types of nephron shown

Answer 14

Question 15

What are the 2 types of nephron?

Answer 15

CORTICAL NEPHRONS

70-80% of all nephrons in human kidneys

Located in the cortex

Short loop of Henle into medulla

JUXTAMEDULLARY NEPHRONS

20-30% of all nephrons in human kidneys

Situated closer to medulla

Loop of Henle extends deep into renal pyramids

Question 16

Why do kidneys recieve 20% of cardiac output?

Answer 16

Required for energy-consuming transport processes

Question 17

Answer 17

Question 18

Complete the diagram on blood vessels in the nephron

Answer 18

Question 19

Complete the diagram on blood supply to the nephron

Answer 19

Question 20

What is the sympathetic nerve supply to the kidneys?

Answer 20

Sympathetic postganglionic fibres from sympathetic chain and fibres from coeliac ganglion

• supplies arteries, afferent and efferent arterioles and granular cells
• reduces blood supply to kidney during stress (fight or flight response)

Question 21

What is the parasympathetic supply to the kidneys?

Answer 21

Parasympathetic efferent supply from vagus nerve - ganglion in hilum

• may control tone of efferent arterioles
• may modify glomerular filtration rate (GFR) and renal blood flow (RBF)

Question 22

Which nervous supply to the kidneys may be associated with hypertension?

Answer 22

Sympathetic

Question 23

What are the 3 major functions of the nephron?

Answer 23

FILTRATION of blood to produce a filtrate

REABSORPTION of water, ions and organic nutrients from filtrate

SECRETION of waste products into tubular fluid

Question 24

What are the 2 types of transport that happens in the nephron?

Answer 24

Transcellular transport - movement through cells

Paracellular transport - movement between cells

Question 25

What is glomerular filtration

Answer 25

Filtration occurs at the glomerulus

It is the initial step in urine formation

Question 26

List the molecules that are filtered and not filtered at the glomerulus

Answer 26

All small molecules are filtered

• Electrolytes
• Amino acids
• Glucose
• Metabolic waste
• Some drugs, metabolites

Cells and large molecules remain in the blood

• Red blood cells
• Lipids
• Proteins

Most drugs, metabolites

Question 27

More than ____% of filtered water, electrolytes and nutrients are reabsorbed back into the blood…

Answer 27

More than 99% of filtered water, electrolytes and nutrients are reabsorbed back into the blood…

Question 28

How does tubular reabsorption occur?

Answer 28

Some solutes (e.g. Na+) are reabsorbed down concentration and/or electrochemical gradients

Others molecules can undergo co- transport, (e.g. glucose with Na+)

Water follows passively along the osmotic gradient created by solute (Na+) reuptake via aquaporins

Reabsorption of solutes requires energy in the form of adenosine triphosphate (ATP) which drive Na+ reabsorption via the Na+K+ATPase transporter

Question 29

How does tubular secretion work?

Answer 29

Some endogenous substances and drugs cannot be filtered at the glomerulus - this may be due to their size or due to their protein binding

Specialised pumps in the PT can transport compounds from the plasma into the nephron for excretion

Question 30

What are the 2 kinds of pumps involved in tubular secretion?

Answer 30

For organic acids or drugs (e.g. uric acid, diuretics, antibiotics – e.g. penicillin)

For organic bases or drugs (e.g. creatinine, procainamide)