Unit 3. Renal Anatomy & Function

Urine

______ is a body fluid that flushes out waste products from the body

It is formed in our urinary system as blood is filtered by the kidney in order to remove unneeded products of metabolism that are somehow considered deleterious to one's health.

1. They should be sterile

2. Lined by special cells. (EXCEPT for KIDNEYS)

Renal organs should be?

1. kidneys

2. ureters

3. bladder

4. urethra

Enumerate RENAL ORGANS

Kidneys

It is a bean shaped paired organ, where the urine is formed, located at the posterior wall of the abdomen.

1-1.5 millions

Each kidney is composed of approximately ___________ of nephrons.

a. Cortical Nephrons

b. Juxtamedullary nephron

Types of Nephrons

Length = 12.5 cm

Width = 6cm

Thickness = 2.5 cm

Kidney dimensions

CORTICAL NEPHRON

This type of nephron constitute approximately 85% of the nephron in the kidneys

cortex ;

tubular reabsorption and secretion

CORTICAL NEPHRON is seen in the _______ alone and is intended for _________________

JUXTAMEDULLARY NEPHRON

have longer henle's loops that extend deep into the medulla of the kidney.

concentration of the urine.

JUXTAMEDULLARY NEPHRON plays a significant role in the ___________________

Glomerulus

2 main parts of Nephrons:

• comprised of highly specialized tuft of capillaries that is intended for the filtration of blood.

8 capillary lobes ;

glomerular filtration barrier

Glomerulus consists of a coil of approximately ______________, the walls of which are referred to as _______________________

Loop of Henle

2 main parts of Nephrons:

• specialized for reabsorption and secretion processes.

Loop of Henle

2 main parts of Nephrons:

• plays a crucial role in adjusting urine concentration before micturition.

URETER

Connects the kidneys to the bladder

Length = 25cm

URETER dimensions

URINARY BLADDER

Serves as storage of urine

150 ml of urine

Maximum volume of urine the bladder can hold

micturition reflex

When the bladder is full, we get the sense of urination, called as the ___________

URETHRA

Where urine is drained

Male = 24cm

Female = 4 cm

URETHRA dimensions

Urethritis

• Urethra becomes swollen or sore

• Usually seen in female young adults who are sexually active

cystitis

• Infection of the urinary bladder

• Lower Urinary Tract Infection

pyelonephritis

• infection of the kidneys

• Upper Urinary Tract Infection

1. Renal blood flow

2. Glomerular filtration

3. Tubular Reabsorption

4. Tubular Secretion

The urine volume and concentration is regulated by what renal functions?

renal artery ;

nephron

RENAL BLOOD FLOW:

• The ____________ supplies blood to the kidney, wherein the kidneys carry blood to enter the capillaries of _________.

glomerulus

RENAL BLOOD FLOW:

• Filtration process through the _________ separates the filtrate from the filtered blood.

efferent arteriole.

RENAL BLOOD FLOW:

• After filtration, the remaining blood exits the glomerulus through the ______________

peritubular capillaries

RENAL BLOOD FLOW:

• Around the proximal convoluted tubule (PCT) and distal convoluted tubule (DCT) are the ____________________

a. Reabsorption

b. Secretion

RENAL BLOOD FLOW:

• 2 main functions of peritubular arteries

PCT

Major site of reabsorption

DCT

Major site of concentration and final adjustments of urine

vasa recta

The _________ which is located adjacent to the Loop of Henle in the juxtaglomerular region, serves as a site for major exchanges of water and salts.

osmotic gradient (salt concentration)

The exchange happening in the vasa recta maintains the ____________________ in the medulla, which is necessary for renal concentration.

water and salts ;

countercurrent exchange

Vasa recta exchanges ___________ with the surrounding tissues through a process called ___________________.

renal vein

After reabsorption and secretion are complete, the blood enters larger veins that unite onto the _________, which carries the cleaned blood back to the heart.

Renal artery → afferent arteriole → glomerulus → efferent arteriole → peritubular capillaries → vasa recta → renal vein

Summary of Renal blood flow

Bowman’s Capsule → PCT → Descending loop of Henle → Ascending loop of Henle → DCT→ Collecting duct → Renal calyces → Ureter → Bladder

Summary of Urinary Filtrate Flow

25%

Human kidney receive approximately _____ of cardiac output (blood pumped by the heart)

Afferent arteriole

where blood enters the kidney.

Efferent arteriole

where blood drains after glomerular filtration

Peritubular capillaries and Vasa recta

blood from efferent arteriole enters here

Peritubular capillaries

surround the PCT and DCT for reabsorption of important substances

Vasa recta

it is located adjacent to ascending and descending loops of Henle

Descending loops of Henle

where major exchanges of water and salt take place between blood and medullary interstitium

Medullary interstitium

this maintains osmotic gradient

Renal blood flow -=approximately 1200 ml/min

Renal plasma flow = ranges from 600 to 700 ml/min

For normal body size which is 1.73m² of surface:

Renal blood flow =

Renal plasma flow =

a. Glomerular Structure

b. Glomerular Pressure

c. Renin-Angiotensin-Aldosterone System (RAAS)

FACTORS THAT AFFECT KIDNEY (GLOMERULAR) FILTRATION

1. Capillary endothelial cells

2. Basement membrane (basal lamina)

3. Visceral epithelium of the Bowman capsule

3 distinct structural components of the glomerulus:

pores (fenestrated)

The endothelial cells of the capillary wall differ in those other capillaries by containing ______________

permeability ;

macromolecules and cells

The pores of the capillary endothelium increase capillary ____________, but do not allow _________________ to pass through

Hydrostatic pressure (Glomerular pressure)

Results from the differences in sizes of

• The afferent arteriole = wider (larger diameter).

• The efferent arteriole = narrower (smaller diameter).

autoregulatory mechanism

There is an ________________ . that aid in this process by increasing or decreasing the size of the afferent and efferent arterioles.

RAAS

The _______ is a hormonal system that maintains blood pressure, blood volume, and sodium balance.

Juxtaglomerular Apparatus (JGA)

The RAAS is controlled by the ____________________, a specialized structure found in the nephron.

1. Juxtaglomerular cells

2. Macula densa

Juxtaglomerular apparatus components:

Juxtaglomerular (JG) cells

Juxtaglomerular apparatus components:

• Located in the afferent arteriole

• Detect low blood pressure

renin

Juxtaglomerular (JG) cells release what enzyme

Macula densa

Juxtaglomerular apparatus components:

• Located in the distal convoluted tubule (DCT)

• Detects the amount of sodium chloride (NaCl) in the filtrate

• blood pressure

• plasma sodium content

RAAS regulates the flow of blood to and within the glomerulus by responding to which changes?

1. Dilates afferent arteriole & constricts efferent arteriole

2. Stimulates sodium reabsorption in the PCT

3. Triggers the adrenal cortex to release aldosterone

4. Triggers hypothalamus to release antidiuretic hormone (ADH)

4 Actions of RAAS

TUBULAR REABSORPTION

The body cannot lose 120 mL of water-containing essential substances every minute. Therefore, when the plasma ultrafiltrate enters the proximal convoluted tubule, the nephrons, through cellular transport mechanisms, begin reabsorbing these essential substances and water.

1. active transport

2. Passive transport

2 means of tubular reabsorption:

ACTIVE TRANSPORT

2 means of tubular reabsorption:

• The substance to be reabsorbed must combine with a carrier protein contained in the membranes of the renal tubular epithelial cells

Passive Transport

2 means of tubular reabsorption:

• It is the movement of molecules across a membrane as a result of differences in their concentration or electrical potential on opposite sides of the membrane

• Glucose, amino acids, salts = PCT

• Chloride = Ascending Loop of Henle

• Sodium = PCT & DCT

Substances reabsorbed via active transport

• Water = in all parts of the tubule EXCEPT in the Ascending Loop of Henle

• Urea = PCT & Ascending loop of Henle

• Sodium = Ascending loop of Henle

Substances reabsorbed via passive transport

TUBULAR SECRETION

Substances that are no longer needed by the body are secreted so that equilibrium in metabolism is maintained.

acid base balance.

Tubular secretion is important in eliminating waste products not filtered by the glomerulus and in regulation of _______________