Urinary 1

Question 1

Label the main components of the urinary system

Answer 1

maacro level:

• Bilaterally symmertrical- two kidneys
• kidneys joint to bladder by ureters
• bladder joined to exit point by urethras

micro level:

• renal cortex- outer layer (short nephrons here)
• renal medulla- inner layer (long nephrons here)
• nephrons drain into the renal pelvis
• renal pelvis drains down the urethers into the bladder
• long juxtamedullary nephron
• Short cortical nephron

Question 2

Explain the functions of the kidneys

Answer 2

•The kidneys perform a variety of functions aimed at maintaining homeostasis

–Kidneys, in concert with hormonal and neural inputs that control their function, are primarily responsible for maintaining stable volume, electrolyte composition, and osmolarity of the ECF

Question 3

The body’s main fluid compartments:

Answer 3

• Extracellular (1/3) – plasma and interstitial fluid
• Intracellular (2/3)

These compartments are separated by blood vessels, but free exchange occurs

Question 4

State the fluid composition for a 65kg male

Answer 4

Total body fluid~ 40L

Intracellular~ 25L

Extracellular (plasma-3L and interstiltial fluid-12L)~ 15L

Question 5

Give an overview of basic kidney functions and processes

Answer 5

–Maintain H₂O balance in the body

–Maintain proper osmolarity of body fluids, primarily through regulating H₂O balance

–Regulate the quantity and concentration of most ECF ions

–Maintain proper plasma volume

–Help maintain proper acid-base balance

Question 6

Kidney functions: production, conversion and excretion

Answer 6

–Eliminate wastes of bodily metabolism

–Excrete foreign compounds

–Produce renin

–Produce erythropoietin

–Convert vitamin D into its active form (D2 to D3)

Question 7

What does the urinary system consists of

Answer 7

the urine-forming organs

–Kidneys and structures that carry urine from the kidneys to the outside for elimination from the body

Question 8

What is the Functional Unit of the Kidney?

Answer 8

The nephron

Question 9

State the Vascular components of the nephron

Answer 9

–Glomerus, afferent arterioles, efferent arterioles, and peritubular capillaries

Question 10

Where does the tubular component of the nephron start?

Answer 10

At the Bowmans capsule

Question 11

Where are the cortical and juxtamedullary nephrons?

Answer 11

–Glomeruli of cortical nephrons lie in the outer cortex layer and glomeruli of juxtamedullary nephrons lie in the inner cortex layer

Question 12

Functions of Parts of a Nephron: Afferent arteriole (vascular component)

Answer 12

Carries blood to the glomerulus

Question 13

Functions of Parts of a Nephron: Glomerulus (vascular component)

Answer 13

A tuft of capillaries that filters a protein-free plasma into the tubular component

Question 14

Functions of Parts of a Nephron: Efferent arteriole (vascular component)

Answer 14

Carries blood from the glomerulus

Question 15

Functions of Parts of a Nephron: peritubular capillaries (vascular component)

Answer 15

supply the renal tissue; involved in exchanges with the fluid in the tubular lumen

Question 16

Functions of Parts of a Nephron: Bowman’s capsule (tubular component)

Answer 16

Collects the glomerular filtrate

Question 17

Functions of Parts of a Nephron: Proximal tubule (tubular component)

Answer 17

Uncontrolled reabsorption and secretion of selected substances occur here

Question 18

Functions of Parts of a Nephron: Loop of Henle (tubular component)

Answer 18

(of juxtamedullary nephrons only; not shown)—establishes an osmotic gradient in the renal medulla that is important in the kidney’s ability to produce urine of varying concentration

Question 19

Functions of Parts of a Nephron: Distal tubule and collecting duct (tubular component)

Answer 19

Variable, controlled reabsorption of Na+ and H₂O and secretion of K⁺ and H⁺ occur here; fluid leaving the collecting duct is urine, which enters the renal pelvis

Question 20

What is the combined vascular and tubular component of the nephron?

What is the function of this component?

Answer 20

Juxtaglomerular apparatus

Formed by the distal convoluted tubule and the glomerular afferent arteriole—produces substances involved in the control of kidney function

Question 21

Label the tubular and vascular components of the kidney

Answer 21

Question 22

What are the 4 Basic Renal Processes?

Answer 22

• Glomerular filtration→ filtration of blood at the glomerulus
• Tubular reabsorption→ reabsorption of contents that have been filtered into the tubular components back into the blood
• Tubular secretion→ secretion of compounds that weren’t filtered from blood vessels into the tubular components
• Urine excretion→ removal of the filtrate from the body as urine

Question 23

Define glomerular filtration

Answer 23

Nondiscriminant filtration of a protein- free plasma from the glomerulus into Bowman’s capsule

Question 24

Define tubular reabsoprtion

Answer 24

Selective movement of filtered substances from the tubular lumen into the peritubular capillaries

Question 25

Define tubular secretion

Answer 25

Selective movement of nonfiltered substances from the peritubular capillaries into the tubular lumen

Question 26

Draw a diagram to explain golmerular filtration

Answer 26

Glomerulus-production of filtrate from the blood

tubular reansorption- components that have been filtered into the tubular components of the nephron can be reasbsorbed across the cells that line the lumen, into interstiital fluid and back into the blood

Tubular secretion- Compounds that were’nt filtered into the glomerulus and have gone into the peritubular capillary can be secreted from the blood vessels and absorbed into the filtrate

Question 27

Why is the glomerular membrane considerably more permeable than capillaries elsewhere?

Answer 27

Glomerular capillary wall consists of a single layer of flattened endothelial cells

Question 28

What is the major force that causes glomerular filtration?

Answer 28

•Glomerular capillary blood pressure is the major force that causes glomerular filtration

–3 forces involved in glomerular filtration

–Glomerular filtration rate (GFR = K_f x net filtration pressure)

K_f = the coefficient of filtration

this is regulated by the shape of cells (podocytes) that line the glomerulus

Question 29

To be filtered, a substance must pass through:

Answer 29

1. The pores between and the fenestrations within the endothelial cells of the glomerular capillary
2. An acellular basement membrane
3. The filtration slits between the foot processes of the podocytes in the inner layer of Bowman’s capsule

Question 30

Label the Bowman’s capsule and the glomerulus inside it

How does the shape of the podocytes change to failitate or inhibit filtration?

Answer 30

• Podocytes- act as gatekeepers in the lumen of the Bowmans capsule, their shape can be regulated under neural and hormonal activity (they can become long and thin- creating gaps between cells which means that filtering blood into the tubular components will be easier or they can become short and wide to inhibit filtration)

Question 31

Describe the relative size of the afferent arteriole and efferent areriole that go into and come out of the glomerulus

Answer 31

Afferent arteriole that is supplying blood to the glomerulus is much thicker and more muscular than the efferent arteriole. This gives the kidney local control over blood flow into the glomerulus because it can cause either vasodilation or vasoconstriction of the afferent arteriole which can increase or decrease the pressure of the blood that goes into the glomerulus

Question 32

State the forces involved in glomerula filtration and its effect

Answer 32

Glomerular capillary blood pressure→ favors filtration (55mmHg)

Plasma-colloid osmotic pressure (created by molecules that have been absorbed → Opposes filtration (30mmHg)

Bowmn’s capsule hydrostatic pressure→ Favors filtration (15mmHG)

Net filtration pressure (difference between force favoring filtration and forces apposing filtration) → favors filtration (10mmHg)

Question 33

•Changes in GFR result mainly from changes in glomerular capillary blood pressure

Answer 33

–Unregulated influences on the GFR (PCOP- plasma coroid osmotic pressure and BCHP- bowmans capsule hydrostatic pressure)

–Controlled adjustments in the GFR (GCBP- )

–Mechanisms responsible for autoregulation of the GFR (ABP)

Myogenic mechanism – smooth muscle stretch

Tubuloglomerular feedback

–Importance of autoregulation of the GFR

Question 34

How does arteriolar vasodilation and vasocostriction affect GFR?

Answer 34

Arteriolar vasoconstriction decreases the GFR

Arteriolar vasodilation increases the GFR

Question 35

–Extrinsic sympathetic control of the GFR

Explain how Intrinsic controls can be overridden by extrinsic controls

Answer 35

• blood volume drops activates baroreceptors
• Sympathetic vasoconstriction in arterioles throughout the body
• Afferent arterioles have more adrenergic receptors than efferent
• Afferent constricts more than efferent
• Less blood flows into the glomerulus and blood leaves easier.

Question 36

Summarise the facotors that affect GFR

Answer 36

Question 37

What is GFR influenced by?

Answer 37

GFR is Influenced by Changes in the Filtration Coefficient (K_f)

Question 38

•GFR depends on the surface area and permeability of the glomerular membrane (both are variable):

How much of the cardiac output do the kidneys recieve?

Answer 38

•The kidneys normally receive 20% to 25% of the cardiac output

–Must continuously perform regulatory and excretory functions on huge volumes of plasma delivered to maintain internal fluid environment stability

Question 39

(a) Describe increased K_f on podocyte relaxation
(b) Describe decreased K_f on podocyte contraction

Answer 39

Increased filtration coefficient= podocytes lengthen, creating gaps (filtration slits)= increased volume of filtrate passing from vascular components to tubular components

Decreased filtration coefficient= podocytes stimulated neurally or horomonally to contract, they are closer together and close off filtration slits= decreased volume of filtrate passing from vascular components to tubular components

Question 40

How does the length of nephrons differ when they live in arid conditions such as a sandrat?

Answer 40

Longer nephrons to provide a larger surface area for water to be reasbsorbed

Question 41

Describe the ajustment pathway that can be made for a drop in blood pressure that involve a change in golmelular filtration rate

Answer 41

1. Drop in arterial blood pressure
2. detection by aortic arch and carotid sinus baroreceptors
3. Increased sympathetic activity
4. Generalised arteriolar vasoconstriction
5. Afferent arteriolar vasoconstriction
6. Decreased GFR
7. Decreased urine volume
8. Increased conservation of fluid and salt
9. Increased arterial blood pressure

Question 42

Describe the short term adjustment for decreased arterial blood pressure

Answer 42

• Increased total peripherial resistance
• Increased cardiac output
• Increased arterial blood pressure

Question 43

What are the two biggest drivers of filtration?

Answer 43

1. Change in blood pressure in the glomerulus
2. Change in permeability in the Bowmans capsules