Intro to Renal Review!

Kidneys!

100

What do kidneys do when there's too much OR too little of something? Any limitations?

Too much: out through the urine

Too little: stays in body BUT kidney HAS to make a minimum amount of urine a day, so there will still be water/electrolyte loss

200

What are the *main* functions of the kidneys?

Homeostatic function to control ECF volume, electrolyte composition + osmolarity

300

List the 10 kidney functions:

1. Water Balance

2. Acid-Base Balance

3. Osmolarity of body fluids

4. Quantity + concentration of ECF ions

5. Plasma volume

6. Excreting wastes

7. Excreting foreign compounds

8. Producing erythropoietin (blood)

9. Producing renin (salt)

10. Converting vitamin D into active form

400

Define:

Renal cortex 

+

Renal medulla

Renal cortex: outer, granular (due to all glomeruli + Bowman's capsules) region of kidneys

Renal medulla: inner region of kidneys that form renal pyramids (striated triangles due to parallel arrangement of tubules + vessels)

DUE TO ARRANGEMENT OF NEPHRONS

500

Describe the flow of urine after being filtered by the kidneys.

Kidney -> renal pelvis -> ureter (duct) -> urinary bladder (temporarily stores urine) contracts -> urethra -> outside body

Urethra in males: long + curvy + prostate surrounds

Nephron!

100

What is a nephron + what is its basic function?

Functional unit of the kidney.

Regulates water, bp, and solute by filtering blood + making urine

200

What are the components of a nephron and what are their basic components?

Vascular component: glomeruli (ball-like tufts of capillaries)

Tubular component: hollow, fluid-filled tube

300

Describe the passage of blood through the nephron.

Renal arteries ---divide---> afferent arterioles ---supply blood to---> glomerular capillaries (filters) ---join to form ---> efferent arteriole ---subdivides---> pertibular capillaries (supply renal tissue w/ blood around tubular) ---rejoin ---> venules -> renal vein -> leaves kidney

400

Describe the basic components of the "tubular component"

Bowman's capsule (around glomerulus + collects filtrate)

Proximal tubule (uncontrolled reabsorption, v coiled)

Loop of Henle (u-shaped, establishes osmotic gradient in renal medulla; descending + ascending) -> in between afferent + efferent  by glomerulus = juxtaglomerular apparatus

Distal tubule (controlled reabsorption)

Collecting duct (tubule) (draining urine from diff. nephrons into renal pelvis)

500

Describe the differences between the two types of nephrons.

1. Cortical Nephrons: glomeruli in outer layer of cortex, loop of Henle only a little bit in medula (majority of nephrons for regulation + excretion)

2. Juxtamedullary nephrons: glomeruli in inner layer of cortex next to medulla (most of urine dilute/concentrate), loop of Henle completely in medullar, pertibular capillaries = vasa recta (hair pin mirroring Henle)

Renal Processes

100

What are the basic renal processes (to make urine)?

1. Glomerular filtration

2. Tubular reabsorption

3. Tubular secretion

200

Describe glomerular filtration

Non-discriminant filtration of a protein-free plasma from the glomerulus into Bowman's capsule

300

Describe Tubular reabsorption

Selective movement of filtered substances from the tubular lumen into the peritubular capillaries (to re-circulate, most of plasma does this)

400

Describe Tubular Secretion

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

500

Describe Urine excretion

elimination of substances from the body in the urine, result of the three processes. more stuff excreted here than is filtered (because of tubular secretion).

Renal Blood Flow + Glomerular Filtration

100

When is RBF the highest and when is it the lowest?

RBF highest at rest, lowest when exercising.

200

What controls the RBF?

ANS - sympathetic + vasoconstriction (enforced by adrenal medulla), nerves not essential BECAUSE:

Autoregulation:

1. Myogenic response (smooth muscle contract)

2. Tubuloglomerular feedback (constriction of afferent arterioles due to increased NaCl concentration in distal tubule)

300

What makes up the glomerular membrane?

1. Glomerular capillary wall

2. basement membrane

3. inner layer of Bowman's capsule

400

Describe the Glomerular capillary wall + the Basement Membrane in more detail:

Glomerular capillary wall: single, flat, perforated w/ large pores

Basement membrane: acellular, gelatinous, collagen (strength), glycoproteins (-ve and discourages smaller plasma proteins)

500

Describe Inner Bowman's capsule in more detail.

Made up of "podocytes" -> octopus-like cells that encircle glomerular tuft w/ elongated foot processes that enterlace w/ neighbouring ones

"filtration slits" narrow slits between these ^^ that make a pathway for fluid

Glomerular Capillary Blood Pressure

100

What are the unique characteristics of Glomerular capillary BP in comparison to other capillary BPs?

1. MUCH more permeable

2. Filtration happens across entire length

200

What are the forces involved with Glomerular capillary BP?

1. Glomerular capillary BP = favours filtration (very high, heart)

2. Plasma-colloid osmotic pressure = opposes filtration (unequal protein + water)

3. Bowman's capsule hydrostatic pressure = opposes filtration (out of Bowman's)

300

Describe net filtration pressure

net difference favouring filtration, forces blood through glomerular membrane 

400

Describe glomerular filtration rate (GFR)

actual rate of filtration, depends on net filtration + how much glomerular SA there is (how holey is it?)

GFR = Kf (filtration coefficient) X net filtration pressure

500

What controls GFR?

Plasma-colloid + bowman's capsule pressure not subject to regulation - can randomly change in disease state

Controlled adjustments BY Glomeruli capillary bp: effects radius + therefore resistance of afferent arteriole:

1. auto-regulation (prevents quick, random changes)

2. extrinsic sympathetic control (long-term regulation of arterial bp)